{"gene":"CYTH2","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":1997,"finding":"ARNO activates ARF1 through its Sec7 domain catalytic activity; the PH domain binds PIP2 to recruit ARNO to membranes, but PIP2-PH interaction does not directly regulate catalytic activity — it serves only for membrane recruitment. Efficient activation of full-length ARF1 requires two distinct protein-phospholipid interactions: PH domain binding PIP2 and electrostatic interactions between ARF1 N-terminal cationic residues and anionic phospholipids.","method":"In vitro nucleotide exchange assay on soluble truncated ARF1 ([Δ17]ARF1) and full-length myristoylated ARF1 with liposomes; isolation of stable Sec7-nucleotide-free ARF1 complex","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified proteins and lipid vesicles, multiple conditions tested, mechanistically informative","pmids":["9268368"],"is_preprint":false},{"year":1998,"finding":"Crystal structure of the Sec7 domain of ARNO resolved at 2.0 Å; the domain is an elongated all-helical protein with a conserved hydrophobic groove and adjacent loop identified as the ARF-interacting surface. Structure-based mutagenesis confirmed the groove and loop as the ARF1-binding site.","method":"X-ray crystallography at 2.0 Å; structure-based mutagenesis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis validation, replicated independently by two groups (PMID 9476900)","pmids":["9510256"],"is_preprint":false},{"year":1998,"finding":"Crystal structure of the Sec7 domain of ARNO determined at 2.2 Å; protein footprinting mapped ARF1 interaction sites to the switch 1 and switch 2 GTPase regions, providing a model for ARF GTPase–Sec7 domain exchange factor interaction.","method":"X-ray crystallography at 2.2 Å; protein footprinting experiments","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with footprinting, independent replication of Sec7 structure","pmids":["9476900"],"is_preprint":false},{"year":1998,"finding":"Glu156 in the hydrophilic loop of the ARNO Sec7 domain acts as a 'glutamic finger' that destabilizes Mg2+ and GDP from ARF1. Conservative mutation E156D and charge-reversal E156K each reduce exchange activity by several orders of magnitude. E156K forms a complex with Mg2+-free ARF1-GDP without inducing GDP release. Lys73 of ARF1 switch II forms an ion pair with Asp183 of ARNO-Sec7.","method":"Site-directed mutagenesis; in vitro nucleotide exchange assays; stable complex isolation","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with in vitro exchange assays, multiple mutants tested, specific residue identified","pmids":["9649435"],"is_preprint":false},{"year":1998,"finding":"ARNO localizes to the plasma membrane in mammalian cells (not the Golgi) and stimulates nucleotide exchange on both ARF1 and ARF6 in vitro, indicating its likely in vivo function is at the plasma membrane through ARF6 modulation.","method":"Subcellular fractionation; immunolocalization; in vitro nucleotide exchange assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — orthogonal methods (fractionation + immunolocalization + in vitro assay); replicated across multiple subsequent studies","pmids":["9417041"],"is_preprint":false},{"year":1998,"finding":"ARNO PH domain binds PIP3 with higher affinity than PI(4,5)P2; insulin stimulation of 3T3-L1 adipocytes causes rapid PI3K-dependent, PH-domain-dependent translocation of GFP-ARNO to the plasma membrane. Translocation is blocked by wortmannin, LY294002, and dominant-negative p85.","method":"GFP-ARNO live imaging in adipocytes; PI3K inhibitors; dominant-negative p85 co-expression; in vitro PIP3 binding assay","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging, pharmacological inhibition, dominant-negative genetics, and in vitro binding; replicated by subsequent studies","pmids":["9550703"],"is_preprint":false},{"year":1998,"finding":"ARNO overexpression in vivo inhibits the early secretory pathway and causes Golgi disassembly; newly synthesized cargo fails to acquire endoglycosidase H resistance, indicating a block in ER-to-Golgi or early Golgi transport. ARNO overexpression does not affect early endocytosis.","method":"Immunofluorescence; cell fractionation; SEAP secretion assay; endoglycosidase H sensitivity assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal functional assays in single lab, overexpression approach","pmids":["9788883"],"is_preprint":false},{"year":1998,"finding":"PKC phosphorylates ARNO in vivo; co-treatment of ARNO-expressing HeLa cells with PKC agonist PMA induces redistribution of ARNO, ARF6, and actin into lamellipodia-like membrane protrusions. This actin rearrangement requires ARNO catalytic activity and the PH domain (membrane localization). Deletion of the PH domain abolishes cytoskeletal reorganization.","method":"PKC phosphorylation assay; overexpression of WT and catalytically inactive ARNO mutants; immunofluorescence","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional mutants and PKC phosphorylation assay, single lab","pmids":["9802902"],"is_preprint":false},{"year":1999,"finding":"PKC phosphorylates ARNO at S392 within its C-terminal polybasic domain, negatively regulating exchange activity through a 'PH domain electrostatic switch': introducing a negative charge reduces ARNO membrane interaction both in vitro and in vivo, and inhibits exchange in vitro. This represents electrostatic regulation of PH-domain-dependent membrane binding.","method":"In vitro phosphorylation; membrane binding assays; in vitro nucleotide exchange assay; S392A mutagenesis","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis plus in vivo translocation assay, single lab but multiple orthogonal methods","pmids":["10531036"],"is_preprint":false},{"year":2000,"finding":"ARNO PH domain provides specific PIP3 > PIP2 binding; the polybasic C-terminal extension contributes non-specific ionic interactions with acidic phospholipids. PKC phosphorylation of Ser in the C domain reduces ionic affinity for PS but does not affect phosphoinositide specificity. PIP3 is more stimulatory than PIP2 for ARNO-catalyzed ARF activation on vesicles.","method":"Cosedimentation of PH+C and nominal PH domain constructs with lipid vesicles; in vitro exchange assays on vesicles","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple lipid compositions, single lab","pmids":["10801341"],"is_preprint":false},{"year":2000,"finding":"ARNO promotes release of beta-arrestin from its membrane docking site in ovarian follicular membranes, enabling beta-arrestin binding to the LH/CGR third intracellular loop and receptor desensitization. This requires ARNO catalytic activity (E156K blocks desensitization) and PH domain-mediated membrane association. LH/CGR activation of ARNO is PI3K-independent and Gβγ-independent.","method":"Cell-free plasma membrane desensitization assay; Western blot for beta-arrestin; dominant-negative and PH-domain mutant ARNO","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-free membrane assay with multiple mutants, single lab","pmids":["10811902"],"is_preprint":false},{"year":2001,"finding":"ARNO catalytic activity (GEF for ARF6, not ARF1) drives MDCK epithelial cell migration and lamellipodium formation. ARNO-induced motility requires downstream activation of Rac1 and phospholipase D (PLD), which operate as two distinct parallel pathways: PLD inhibition blocks motility without preventing Rac activation.","method":"Dominant-negative and active mutant expression; pulldown ARF6-GTP assay; Rac activation assay; PLD inhibitors; migration assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (ARF6 pulldown, Rac assay, PLD inhibition, migration assay) replicated by subsequent studies","pmids":["11481345"],"is_preprint":false},{"year":2001,"finding":"ARNO and ARF6 are recruited from cytosol to proximal tubule apical endosomes in a pH-dependent manner driven by V-ATPase-dependent acidification; translocation is reversed by V-ATPase inhibitors and pH uncouplers, and correlates with intra-endosomal acidification magnitude.","method":"Subcellular fractionation; translocation assay with ATP-driven acidification; Western blot; V-ATPase inhibitors","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct translocation assay with pharmacological reversal, independent replication by subsequent V-ATPase study (PMID 16415858)","pmids":["11278939"],"is_preprint":false},{"year":2001,"finding":"In vitro, ARNO activates ARF1 preferentially and ARF6 only slightly; these selectivities are determined by the Sec7 domains alone and by the ARF core domains (not the N-terminal myristoylated helix), without depending on PH or N-terminal domains.","method":"In vitro exchange assay on membranes with isolated Sec7 domains and ARF core domains; chimeric ARF constructs","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with domain-swap mutants, single lab","pmids":["11342560"],"is_preprint":false},{"year":2002,"finding":"The N-terminal coiled-coil domain of ARNO/cytohesin-2 interacts with the scaffolding protein CASP via CASP's internal coiled-coil motif. In EGF-stimulated cells, cytohesin recruits CASP to membrane ruffles, demonstrating a functional interaction.","method":"Yeast two-hybrid screening; in vitro pull-down; co-immunoprecipitation in COS-1 cells; immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid + pull-down + co-IP, single lab, multiple methods","pmids":["12052827"],"is_preprint":false},{"year":2003,"finding":"IPCEF1 binds the coiled-coil domain of cytohesin-2; cytohesin-2 binding domain maps to the C-terminal 121 aa of IPCEF1. Interaction confirmed in mammalian cells by co-IP. IPCEF1 increases both in vitro and in vivo ARF-GTP formation by cytohesin-2; IPCEF1 co-migrates with cytohesin-2 to the plasma membrane in EGF-stimulated cells only when the binding site is intact.","method":"Yeast two-hybrid; GST pull-down; co-immunoprecipitation; ARF-GTP formation assay; immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal binding assays plus functional exchange enhancement, single lab","pmids":["12920129"],"is_preprint":false},{"year":2003,"finding":"ARNO mediates ARF activation and PLD activity downstream of insulin signaling; insulin-induced ARNO translocation to plasma membrane requires the PH domain, and the Sec7 domain is required for downstream ARF translocation and PLD activation. The coiled-coil domain contributes to partial membrane targeting.","method":"Transient transfection of WT and domain-deletion/Sec7-mutant ARNO in HIRcB cells; insulin stimulation; ARF translocation assay; PLD activity assay","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple domain mutants with functional readouts, single lab","pmids":["12969509"],"is_preprint":false},{"year":2003,"finding":"ARNO and ARF6 regulate axonal elongation and branching in hippocampal neurons; catalytically inactive ARNO or dominant-negative ARF6 enhance axonal extension and branching. PI(4)P 5-kinase alpha acts downstream of ARF6 to regulate neurite extension. Inactive ARNO/ARF6 depletes Mena from growth cone leading edges.","method":"Expression of dominant-negative and constitutively active constructs in cultured rat hippocampal neurons; immunofluorescence for Mena; epistasis by co-expression","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with multiple constructs, defined cellular phenotype, single lab","pmids":["14565977"],"is_preprint":false},{"year":2004,"finding":"NMR analysis of Arf1 complexed with ARNO-Sec7; Glu156 is required to promote GDP release (E156A and E156K mutants release Mg2+ from Arf1-GDP but do not promote GDP release); the wild-type Sec7 domain weakly competes with GDP on Arf1-GDP-Mg2+ and leads to GDP release; ARNO-Sec7 does not interact appreciably with GTP-bound Arf1.","method":"31P NMR spectroscopy; Arf1-GDP/GTP-Mg2+ complex analysis; mutant ARNO-Sec7 interaction studies","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR structural/biochemical analysis with mutants, single lab","pmids":["14739276"],"is_preprint":false},{"year":2004,"finding":"Cytohesin-2 is required for serum response element (SRE)-mediated transcriptional activation and MAPK signaling; an RNA aptamer specific for cytohesin-2 (discriminating it from cytohesin-1) binds the N-terminal coiled-coil/Sec7 interface and in vivo downregulates SRE-mediated gene expression and MAPK activation. Cytohesin-1 does not substitute for this function.","method":"RNA aptamer ('intramer') transfection; SRE-reporter assay; MAPK activation assay in HeLa cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific inhibitory aptamer with functional readout, single lab, novel reagent","pmids":["15277685"],"is_preprint":false},{"year":2005,"finding":"ARNO directly binds the C-terminus (juxtamembrane portion) of the A2A adenosine receptor; this interaction is required for the sustained (heterotrimeric G protein-independent) phase of ERK/MAP kinase activation. Dominant-negative ARNO (E156K) and dominant-negative ARF6 (T27N) abolish sustained MAP kinase stimulation but do not affect cAMP accumulation or receptor desensitization.","method":"Yeast two-hybrid; mutual pull-down of bacterial fusion proteins; co-immunoprecipitation in mammalian cells; inducible dominant-negative cell lines; cAMP and ERK assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct interaction confirmed by three independent methods plus functional epistasis with inducible expression system","pmids":["16027149"],"is_preprint":false},{"year":2005,"finding":"ARNO-dependent Rac1 activation in migrating MDCK cells is mediated by the Dock180/Elmo bipartite Rac-GEF complex. Catalytically inactive Dock180 and an Elmo mutant that cannot couple to Dock180 both block ARNO-induced Rac activation and motility. Beta-PIX (another Rac-GEF) does not mediate this pathway.","method":"Dominant-negative Dock180 and Elmo mutant expression; co-localization; Rac activation assay; migration assay in MDCK cells","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis with multiple dominant-negative constructs and specificity controls, replicated in context","pmids":["16213822"],"is_preprint":false},{"year":2006,"finding":"ARNO interacts with the a2-isoform of V-ATPase on early endosomes in an intra-endosomal acidification-dependent manner; ARF6 interacts with the c-subunit. Disruption of the V-ATPase–ARNO interaction reversibly inhibits endocytosis. Inhibition of endosomal acidification blocks protein trafficking from early to late endosomes.","method":"Co-immunoprecipitation; subcellular fractionation; dominant-negative constructs; bafilomycin/concanamycin A inhibition; endocytosis assays","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP plus functional inhibition assays, independently replicated by prior proximal tubule study (PMID 11278939)","pmids":["16415858"],"is_preprint":false},{"year":2006,"finding":"In polarized epithelial cells, ARNO localizes exclusively to the apical plasma membrane and regulates apical endocytosis; ARF6 co-expression synergistically stimulates apical endocytosis. The N-terminal coiled-coil domain is required for apical specificity: deletion causes ARNO mislocalization to both membranes, and expression of the CC domain alone abolishes apical endocytosis.","method":"GFP-ARNO expression in MDCK cells; polymeric immunoglobulin receptor endocytosis assay; deletion mutants; immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional consequence, multiple mutants, single lab","pmids":["16484220"],"is_preprint":false},{"year":2006,"finding":"Activated Gαq forms molecular complexes with ARNO and ARF6, preferentially with GTP-bound Gαq. Gαq interacts directly with ARNO (binding experiments with purified proteins). Gαq-dependent ARF6 activation leads to PI(4,5)P2 production and TPβ receptor internalization, both blocked by dominant-negative ARNO and ARF6.","method":"Co-immunoprecipitation; purified protein binding assay; dominant-negative mutants; ARF6-GTP pulldown; PI(4,5)P2 assay; receptor internalization assay","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding with purified proteins plus co-IP and functional assays, single lab","pmids":["16650966"],"is_preprint":false},{"year":2007,"finding":"ARL4D recruits cytohesin-2/ARNO to the plasma membrane in a GTP- and N-terminal myristoylation-dependent manner through direct interaction with the ARNO PH and polybasic C domains. Active ARL4D increases GTP-ARF6 levels and induces actin stress fiber disassembly; this requires ARNO catalytic activity and ARNO expression (inactive ARNO E156K or ARNO siRNA blocks ARL4D-mediated actin effects). ARL4D-induced CYTH2 translocation is PI3K-independent.","method":"Co-immunoprecipitation; GFP-ARNO translocation assay; ARF6-GTP pulldown; siRNA knockdown; dominant-negative ARNO; immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (Co-IP, translocation, ARF6 activation, siRNA, dominant-negative), single lab","pmids":["17804820"],"is_preprint":false},{"year":2007,"finding":"The coiled-coil domain of the cytohesin/ARNO family interacts with Gαq; cytohesin-2/ARNO and cytohesin-1 mutants lacking the coiled-coil domain cannot relay Gαq-mediated ARF6 activation. Cytohesin-1 preferentially associates with constitutively active Gαq-Q209L.","method":"Co-immunoprecipitation; coiled-coil deletion mutants; ARF6 activation assay; immunofluorescence","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus functional deletion mutant assays, single lab","pmids":["17846866"],"is_preprint":false},{"year":2007,"finding":"CaSR stimulation induces plasma membrane ruffling via a pathway involving beta-arrestin 1, ARNO, ARF6, and ELMO. Beta-arrestin 1 co-immunoprecipitates with CaSR and ARNO under resting conditions; agonist treatment causes translocation of CaSR, beta-arrestin 1, and ARNO to membrane protrusions. Catalytically inactive ARNO reduces ruffling. ARF6 and ELMO are required downstream.","method":"Co-immunoprecipitation; siRNA knockdown; dominant-negative ARNO; dominant-negative beta-arrestin 1; immunofluorescence","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, siRNA, dominant-negatives with defined phenotypic readout, single lab","pmids":["17623778"],"is_preprint":false},{"year":2009,"finding":"ARNO-induced Rac activation and migration require the coiled-coil domain; the coiled-coil promotes assembly of a multiprotein complex containing ARNO and Dock180. Knockdown of either GRASP/Tamalin or IPCEF1 (which bind the ARNO coiled-coil) prevents ARNO–Dock180 association and ARNO-induced Rac activation, placing scaffold proteins as coordinators of ARF-to-Rac signaling.","method":"Co-immunoprecipitation; siRNA knockdown of GRASP and IPCEF1; coiled-coil deletion mutant; Rac activation assay; migration assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple siRNA knockdowns with mechanistic epistasis, single lab","pmids":["20016009"],"is_preprint":false},{"year":2010,"finding":"Paxillin (focal adhesion adaptor) forms a complex with cytohesin-2 mediated by the LIM2 domain of paxillin and the polybasic region of cytohesin-2. Paxillin co-localizes with cytohesin-2 at leading edges of migrating 3T3-L1 cells. siRNA knockdown of cytohesin-2 inhibits migration and its effects are upstream of ARF6.","method":"Co-immunoprecipitation; domain mapping with deletion mutants; siRNA knockdown; migration assay; immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping plus siRNA and migration assay, single lab","pmids":["20525696"],"is_preprint":false},{"year":2010,"finding":"On model membranes, Arf6-GTP activates Arno at nanomolar concentrations (vs. micromolar in solution); mutations in the PH domain abolishing Arf6-GTP interaction render Arno completely inactive on liposomes but not in solution. Arno is also activated by its own product Arf1-GTP (positive feedback), behaving as a bistable switch requiring an Arf activator; Arno activity is modulated by competition with Arf effectors.","method":"Kinetic nucleotide exchange assays on liposomes with membrane-anchored full-length Arf1 and Arf6; PH domain mutants; competition experiments with Arf effectors","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted system on liposomes with full-length proteins, multiple mutants, mechanistic model validated quantitatively","pmids":["21118813"],"is_preprint":false},{"year":2010,"finding":"The N-terminus of the V-ATPase a2-subunit interacts with multiple domains of ARNO; the a2N-01 peptide (MGSLFRSESMCLAQLFL) specifically binds the Sec7 domain with KD ~3.44×10⁻⁷ M. In silico docking shows a2N competes with switch 2 of Arf1/Arf6 for Sec7 domain binding. Phosphorylation of ARNO Ser392 abolishes a2N binding to the ARNO PB domain.","method":"Synthetic peptide pull-down assays; surface plasmon resonance; NMR structure determination of peptides; homology modeling/in silico docking","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — SPR binding kinetics + NMR structure + docking, single lab","pmids":["20153292"],"is_preprint":false},{"year":2011,"finding":"ARNO directly interacts with aldolase via the ARNO PH domain; surface plasmon resonance yields KD = 2.84×10⁻¹⁰ M. Aldolase associates with early endosomal membranes. Aldolase knockdown in HeLa cells causes morphological changes and acidic vesicle redistribution, and is inversely correlated with gelsolin levels.","method":"Pull-down with recombinant proteins (GST-PH domain); surface plasmon resonance; subcellular fractionation; siRNA knockdown; immunofluorescence","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — SPR binding with recombinant proteins plus siRNA functional assay, single lab","pmids":["21307348"],"is_preprint":false},{"year":2011,"finding":"ARNO promotes sequential activation of Arf6, then Cdc42, then Rac1 in pancreatic β-cells to stimulate glucose-stimulated insulin secretion (GSIS). siRNA-ARNO, dominant-negative ARNO (E156K), and SecinH3 each inhibit GSIS and block glucose-induced Arf6 activation in INS 832/13 cells and rat islets. ARNO–Arf6 complex association increases in glucose-stimulated β-cells.","method":"siRNA knockdown; dominant-negative mutant expression; SecinH3 inhibitor; GST-GGA3 ARF6-GTP pulldown; PAK-1 Rac/Cdc42 pulldown; co-immunoprecipitation; confocal microscopy","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple approaches (siRNA, dominant-negative, inhibitor) with sequential GTPase activation assays, single lab","pmids":["21276423"],"is_preprint":false},{"year":2012,"finding":"ARNO directly binds the adaptor protein MYD88, forming a MYD88–ARNO–ARF6 signaling complex. IL-1β activates ARF6 through this pathway in endothelial cells in an NF-κB-independent manner, disrupting endothelial barrier function. SecinH3 (ARNO inhibitor) enhances vascular stability and improves outcomes in animal models of inflammatory arthritis.","method":"Co-immunoprecipitation; direct binding assays; dominant-negative ARF6/ARNO; in vitro permeability assay; in vivo inflammatory arthritis model with SecinH3","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding confirmed, functional epistasis in vitro and in vivo, published in Nature","pmids":["23143332"],"is_preprint":false},{"year":2012,"finding":"During Salmonella invasion, ARNO is recruited via Arf6 and SopB-induced PIP3 generation; ARNO in turn triggers WAVE regulatory complex (WRC) recruitment and activation for membrane ruffling and macropinosome formation. RNAi screening identified ARNO as a key host Arf-GEF for Salmonella invasion.","method":"RNAi screen; siRNA knockdown; fluorescence microscopy; invasion assay; Arf6-GTP pulldown","journal":"Cell host & microbe","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi screen plus functional validation, pathway placement, single lab","pmids":["22341462"],"is_preprint":false},{"year":2013,"finding":"The N-terminal cytosolic tail of V-ATPase a2-subunit (first 17 aa, a2N(1-17)) potently inhibits cytohesin-2 GEF activity by directly interacting with the Sec7 domain, competing with ARF switch 2. Structure of a2N(1-17) and key residues Phe5, Met10, Gln14 involved in Sec7 binding were determined by NMR. This signaling mechanism is conserved across all four mammalian V-ATPase a-subunit isoforms.","method":"In vitro GEF activity assay; NMR spectroscopy; in silico docking; pull-down with recombinant proteins; binding to intact yeast V-ATPase","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro functional assay + NMR structure + cross-species conservation, multiple orthogonal methods","pmids":["23288846"],"is_preprint":false},{"year":2013,"finding":"Fragment-based drug design identified small molecules that bind directly to specific pockets on the ARNO Sec7 domain surface and inhibit Arno-catalyzed nucleotide exchange on ARF1; binding modes of two compounds resolved by X-ray crystallography, revealing stable and transient pockets at the Sec7 surface.","method":"SPR; NMR; fluorescence assays; X-ray crystallography of Sec7–fragment complexes; in vitro exchange inhibition assay","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of inhibitor-bound Sec7 domain plus in vitro functional assays","pmids":["24112024"],"is_preprint":false},{"year":2014,"finding":"Cytohesin-2 constitutively suppresses platelet dense granule secretion by maintaining ARF6 in a GTP-bound state; PKC-mediated phosphorylation of cytohesin-2 relieves this suppression. SecinH3 enhances dense granule secretion and aggregation but not α-granule release or αIIbβ3 activation. ARF6 interaction with cytohesin-2 decreases upon platelet stimulation in a PKC-dependent manner.","method":"Immunoprecipitation with phosphoserine-PKC antibody; mass spectrometry; lumi-aggregometry; flow cytometry; Western blotting; SecinH3 pharmacological inhibition","journal":"Journal of thrombosis and haemostasis : JTH","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS identification plus functional granule secretion assay with inhibitor, single lab","pmids":["24581425"],"is_preprint":false},{"year":2014,"finding":"Cytohesin-2 interacts with CCDC120 via the CC1 coiled-coil domain; CCDC120 localizes cytohesin-2 into vesicles that undergo anterograde transport along neurites. CCDC120 knockdown inhibits cytohesin-2 vesicular localization, Arf6 activation, and neurite growth; these are rescued by WT CCDC120 but not by CC1-domain-deficient CCDC120.","method":"Co-immunoprecipitation; siRNA knockdown; live vesicle transport imaging; Arf6-GTP assay; rescue experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, siRNA rescue, live imaging, single lab","pmids":["25326380"],"is_preprint":false},{"year":2014,"finding":"Cytohesin-2 activates ARF6 in a PI3K-dependent manner; active ARF6 causes ERK1/2 phosphorylation during preadipocyte migration. Dynamin inhibition blocks migration but not ARF6 or ERK1/2 activation.","method":"siRNA knockdown; pharmacological inhibitors (SecinH3, LY294002, PD98059, dynasore); ARF6-GTP pulldown; ERK phosphorylation by Western blot; migration assay","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple inhibitors + siRNA with ARF6 and ERK activation assays, single lab","pmids":["25450674"],"is_preprint":false},{"year":2014,"finding":"RLIP76 N-terminal domain (residues 1-180) binds ARNO; Ser29/30 in the N-terminus are required for ARNO interaction and for RLIP76-dependent cell spreading, migration, Arf6 activation, and PI3K activation. Ser62 supports ARNO binding and Arf6 activation but Ser62A still blocks Rac1 activation.","method":"Co-immunoprecipitation; domain deletion and point mutants; cell spreading/migration assay; ARF6-GTP pulldown; Rac1 activation assay; PI3K activation assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with multiple mutants plus functional assays, single lab","pmids":["25450693"],"is_preprint":false},{"year":2015,"finding":"Cytohesin-2/ARNO regulates myelin sheath thickness in peripheral nerves; Schwann cell-specific conditional knockout of cytohesin-2 reduces Arf6 activity, myelin thickness, and MPZ expression in sciatic nerves without affecting cell proliferation.","method":"Schwann cell-specific conditional knockout mouse; myelin thickness measurement (electron microscopy); ARF6-GTP assay; Western blot for MPZ; Ki67 staining; SecinH3 treatment of Schwann cell-neuron co-cultures","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockout with defined cellular phenotype (myelin thickness) and ARF6 activity measurement, in vivo and in vitro convergent results","pmids":["25824033"],"is_preprint":false},{"year":2015,"finding":"RLIP76 links ARNO to activated R-Ras at Rab11-positive recycling endosomes; RLIP76 binds ARNO via residues 1-180 and R-Ras via residues 180-192. ARNO localization to recycling endosomes requires RLIP76 and its ARNO-binding domain. Cytohesin-2/ARNO regulates recycling of R-Ras and α5-integrin to the plasma membrane via ARF activation.","method":"Co-immunoprecipitation; domain deletion mutants; immunofluorescence; ARF6-GTP assay; integrin recycling assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with multiple deletion mutants plus recycling assay, single lab","pmids":["26498519"],"is_preprint":false},{"year":2015,"finding":"Cytohesin-2/ARNO regulates R-Ras and α5-integrin recycling through an EHD1-positive recycling endosome compartment; GEF-inactive ARNO (E156K) accumulates R-Ras on recycling endosomes and inhibits cell spreading; ARNO catalytic activity is required for focal adhesion formation and integrin recycling.","method":"Co-localization studies; GEF-inactive E156K-ARNO expression; integrin recycling assay; focal adhesion quantification; siRNA knockdown","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — localization with functional consequence plus GEF-inactive mutant, single lab","pmids":["26378252"],"is_preprint":false},{"year":2016,"finding":"ARNO (co-localizing with podosome adhesive rings) and ARF1 are required for podosome assembly; ARNO/ARF1 knockdown or pharmacological inhibition eliminates podosomes and elevates RhoA-GTP and myosin-IIA filaments. Constitutively active ARF1 induces podosome precursor structures. Suppression of myosin-IIA rescues podosome formation despite ARF1 inhibition, placing RhoA/myosin-II downstream of ARNO/ARF1.","method":"siRNA knockdown; pharmacological inhibitors; ARF1-GTP pulldown; immunofluorescence; constitutively active ARF1 expression; myosin-IIA inhibition rescue","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — siRNA plus pharmacological inhibition plus genetic epistasis with rescue, defined cellular phenotype, multiple cell types","pmids":["28007915"],"is_preprint":false},{"year":2018,"finding":"INAVA (IBD risk gene) CUPID domain stably binds ARNO and effects F-actin assembly at lateral membranes underlying cell-cell junctions in an ARNO-dependent but GEF-activity-independent manner. Upon IL-1β stimulation, INAVA relocates to cytosolic puncta where CUPID amplifies TRAF6-dependent polyubiquitination; ARNO binding to CUPID negatively-regulates this inflammatory polyubiquitination. INAVA and ARNO act similarly in human macrophages.","method":"Co-immunoprecipitation; domain binding assays; F-actin assembly assay; GEF-inactive ARNO; TRAF6 polyubiquitination assay; IL-1β stimulation in epithelial cells and macrophages","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches with GEF-inactive controls in two cell types, bifunctional mechanism established","pmids":["30355448"],"is_preprint":false},{"year":2019,"finding":"ARNO directly binds the juxtamembrane (JM) segment of EGFR intracellular domain; the ARNO-EGFR interaction interface was structurally characterized by NMR and shows common features but distinct differences from JM interactions with calmodulin and anionic phospholipids, forming a regulated modulatory network.","method":"NMR spectroscopy; direct binding assays","journal":"Structure (London, England : 1993)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR structural characterization of interaction interface, single lab, no full functional validation","pmids":["31780432"],"is_preprint":false},{"year":2021,"finding":"CYTH2 (cytohesin-2) is required for the early stage of influenza virus infection by mediating endosomal trafficking; CYTH2 knockout reduces efficient infection, and the CYTH2 antagonist SecinH3 blunts influenza virus infection in vivo.","method":"Genome-wide CRISPR-Cas9 screen; CYTH2 knockout validation; SecinH3 in vivo treatment; infection efficiency assay","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen with genetic knockout validation and in vivo pharmacological inhibition, single study","pmids":["35354039"],"is_preprint":false},{"year":2021,"finding":"CNKSR2 forms a molecular complex with CYTH2 in the hippocampus; CYTH2 binding prevents proteasomal degradation of CNKSR2. Knockdown of either CNKSR2 or CYTH2 in granule cell precursors in vivo results in abnormal localization of cells at the granule cell layer/hilus boundary with characteristics of immature granule cells.","method":"Co-immunoprecipitation; shRNA knockdown in vivo via viral transduction; immunofluorescence; proteasome inhibitor rescue","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vivo shRNA with defined cellular phenotype, single lab","pmids":["34800437"],"is_preprint":false},{"year":2021,"finding":"Cytohesin-2 forms a protein complex with mGluR5 in the spinal cord and is enriched in the perisynapse of dorsal horn neurons. CNS-specific cytohesin-2 conditional knockout mice show reduced mechanical allodynia in inflammatory and neuropathic pain models. SecinH3 inhibits spinal Arf6 (not Arf1) activation. Cytohesin-2 knockout reduces ERK1/2 activation following spinal mGluR1/5 activation.","method":"Co-immunoprecipitation; conditional knockout mice; SecinH3 pharmacological inhibition; mechanical allodynia behavioral testing; Arf6/Arf1-GTP assay; ERK phosphorylation assay","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockout with behavioral and molecular phenotypes, Co-IP for complex, pathway placement, single lab","pmids":["34390832"],"is_preprint":false},{"year":2022,"finding":"Phosphorylation of cytohesin-2 at Tyr381 is central to Schwann cell myelination; knockin mice with Y381F mutation show reduced myelin thickness and decreased Arf6 activity. PTP4A1 dephosphorylates cytohesin-2 at Tyr381; SH2B1 maintains phosphorylation. Schwann cell-specific knockdown of PTP4A1 increases cytohesin-2 phosphorylation and myelin thickness; loss of SH2B1 reduces both.","method":"Knockin mouse (Y381F); conditional Schwann cell knockdown of PTP4A1 and SH2B1; phospho-specific antibody; ARF6-GTP assay; myelin thickness measurement","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockin mouse plus conditional knockdowns with writer/eraser identified and functional output measured in vivo","pmids":["35077201"],"is_preprint":false},{"year":2022,"finding":"Cytohesin-2/ARF1 axis positively regulates osteoclast differentiation; blocking it with SecinH3 or cytohesin-2 siRNA inhibits osteoclast formation and function in vitro and ameliorates ovariectomy-induced osteoporosis in vivo. Mechanistically, cytohesin-2/ARF1 activates the JNK pathway; JNK in turn regulates IRE1 endoribonuclease activity (not kinase) to promote XBP1 splicing.","method":"siRNA knockdown; SecinH3 pharmacological inhibition; in vivo OVX model; RNA-sequencing; JNK and IRE1 activity assays; XBP1 splicing assay","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA + inhibitor + in vivo model with RNA-seq and pathway characterization, single lab","pmids":["36252772"],"is_preprint":false},{"year":2022,"finding":"FE65 neuronal adaptor interacts with ARNO and forms an ARNO–ARF6–FE65 trimeric complex; FE65 potentiates ARNO-stimulated ARF6-mediated neurite outgrowth. FE65 attenuates ARNO intramolecular autoinhibitory interaction and its effect requires ARNO dimerization (monomeric ARNO mutant is not potentiated by FE65).","method":"Co-immunoprecipitation; co-localization; FE65 interaction-disrupting mutation; ARF6 activation assay; neurite outgrowth assay","journal":"Open biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP, functional mutants, and neurite assay, single lab","pmids":["36168805"],"is_preprint":false},{"year":2023,"finding":"V-ATPase V0a1 subunit interacts with ARNO in neuroendocrine cells; disruption of V0a1–ARNO interaction inhibits Arf6 activation during exocytosis, PLD activation, phosphatidic acid synthesis, and alters fusion event timing. This places V-ATPase as an upstream activator of the ARNO–Arf6–PLD1 pathway during exocytosis.","method":"Co-immunoprecipitation; interaction disruption; PLD activity assay; phosphatidic acid measurement; exocytosis timing assay; Arf6-GTP assay in neuroendocrine cells","journal":"Frontiers in molecular biosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional inhibition assays with multiple readouts, single lab","pmids":["37091866"],"is_preprint":false},{"year":2026,"finding":"Full knockout of cytohesin-2 in mice causes perinatal lethality within 20 h of birth. Cytohesin-2 deficiency reduces Golgi volume in C2 myoblasts (restored by re-expression in an ARF-GEF-independent manner), impairs peanut agglutinin staining (galactose/N-acetyl-galactosamine reduction), and markedly reduces global protein secretion in neonatal knockout mice.","method":"Full knockout mouse; mass spectrometry-based organellar proteomics; immunofluorescence; quantitative proteomics; peanut agglutinin staining; re-expression rescue","journal":"Life science alliance","confidence":"High","confidence_rationale":"Tier 2 / Strong — full knockout mouse with multiple orthogonal methods revealing essential Golgi maintenance function; ARF-GEF-independent mechanism established by rescue","pmids":["41672711"],"is_preprint":false}],"current_model":"Cytohesin-2/ARNO is a multi-domain ARF guanine nucleotide exchange factor (GEF) whose catalytic Sec7 domain uses a 'glutamic finger' (Glu156) to displace Mg²⁺ and GDP from ARF1/ARF6, while its PH domain recruits it to membranes via PIP3 (and PIP2); membrane localization is further regulated by PKC-mediated phosphorylation of Ser392 (electrostatic switch), Tyr381 phosphorylation status (controlled by SH2B1/PTP4A1), interaction with ARL4D/Arl4D, and V-ATPase a2-subunit binding to the Sec7 domain; once membrane-recruited, cytohesin-2 activates ARF6 (and ARF1 in some contexts) to drive diverse downstream processes including epithelial cell migration (via Dock180/Elmo→Rac1 and PLD pathways), endocytic trafficking, apical endocytosis, neurite outgrowth, Schwann cell myelination, podosome assembly, platelet dense granule secretion, vascular barrier dissolution (via MYD88–ARNO–ARF6), insulin secretion (via Arf6→Cdc42/Rac1), and Golgi volume maintenance (ARF-GEF-independently); its coiled-coil domain scaffolds interactions with CASP, IPCEF1, GRASP, Gαq, and FE65, while its PH/polybasic domain also binds ARL4D, paxillin, RLIP76, and aldolase to coordinate spatial and contextual ARF6 signaling outputs."},"narrative":{"mechanistic_narrative":"CYTH2 (cytohesin-2/ARNO) is a multidomain guanine nucleotide exchange factor that activates ARF GTPases at the plasma membrane and endosomes to couple receptor and lipid signals to membrane remodeling, cytoskeletal dynamics, and vesicular trafficking [PMID:9417041, PMID:11481345]. Its catalytic Sec7 domain inserts a 'glutamic finger' (Glu156) that destabilizes Mg²⁺ and GDP to drive nucleotide exchange on ARF1 and ARF6, with the conserved hydrophobic groove engaging the ARF switch regions [PMID:9510256, PMID:9476900, PMID:9649435, PMID:14739276]. Membrane recruitment is governed by its PH domain, which binds PIP3 in preference to PIP2 to deliver the enzyme to membranes upon PI3K-dependent stimulation (e.g. insulin), while a C-terminal polybasic region adds non-specific ionic contacts; PKC phosphorylation of Ser392 acts as an electrostatic switch that releases the enzyme from the membrane and downregulates exchange [PMID:9550703, PMID:10531036, PMID:10801341]. On membranes the enzyme behaves as a positive-feedback bistable switch, being itself allosterically activated by ARF-GTP through its PH domain [PMID:21118813]. Through ARF6, CYTH2 drives epithelial cell migration and lamellipodium formation via two parallel outputs—Rac1 activation through the Dock180/Elmo complex and phospholipase D activation [PMID:11481345, PMID:16213822], and contributes to neurite/axon outgrowth, Schwann cell myelination, podosome assembly, integrin recycling, insulin and granule secretion, and exocytosis [PMID:14565977, PMID:25824033, PMID:28007915, PMID:26378252, PMID:21276423, PMID:24581425, PMID:37091866]. Localization, specificity, and signaling context are set by an N-terminal coiled-coil that scaffolds CASP, IPCEF1, GRASP, Gαq, and FE65 and by PH/polybasic interactions with ARL4D, paxillin, RLIP76, and aldolase [PMID:12052827, PMID:12920129, PMID:20016009, PMID:17846866, PMID:36168805, PMID:17804820, PMID:20525696, PMID:25450693, PMID:21307348]. V-ATPase couples endosomal acidification to ARF activation: the a-subunit N-terminus binds the Sec7 domain in competition with ARF switch 2 and modulates GEF activity in a pH-dependent manner [PMID:11278939, PMID:16415858, PMID:23288846]. CYTH2 also relays GPCR and receptor signaling, binding the A2A adenosine receptor, EGFR juxtamembrane segment, and MYD88 to sustain ERK signaling and to control endothelial barrier integrity [PMID:16027149, PMID:31780432, PMID:23143332]. Beyond ARF activation, CYTH2 maintains Golgi volume and global protein secretion in an ARF-GEF-independent manner, and its full knockout is perinatally lethal in mice [PMID:41672711].","teleology":[{"year":1997,"claim":"Established that CYTH2 is a bona fide ARF GEF and that its catalytic and membrane-targeting functions are separable—the Sec7 domain drives exchange while the PH domain binds PIP2 only for recruitment.","evidence":"In vitro nucleotide exchange assays on truncated and full-length myristoylated ARF1 with liposomes","pmids":["9268368"],"confidence":"High","gaps":["Did not resolve atomic catalytic mechanism","ARF6 specificity untested in this system"]},{"year":1998,"claim":"Defined the structural basis of ARF recognition and the catalytic chemistry, identifying the Sec7 hydrophobic groove as the ARF-binding surface and Glu156 as the 'glutamic finger' that expels Mg²⁺ and GDP.","evidence":"Crystal structures at 2.0/2.2 Å with footprinting, plus site-directed mutagenesis (E156D/E156K) and stable complex isolation","pmids":["9510256","9476900","9649435"],"confidence":"High","gaps":["Static structures did not capture the exchange transition state","Membrane context absent from crystallography"]},{"year":1998,"claim":"Placed CYTH2 at the plasma membrane acting on ARF6 in cells while remaining dual-specific in vitro, and linked it to PI3K-dependent, PIP3-driven translocation and PKC-induced actin remodeling.","evidence":"Subcellular fractionation, GFP-ARNO live imaging in adipocytes with PI3K inhibitors and dominant-negative p85, PKC phosphorylation and immunofluorescence","pmids":["9417041","9550703","9802902"],"confidence":"High","gaps":["In vivo ARF6 vs ARF1 selectivity not quantified","Direct PKC site not yet mapped"]},{"year":1999,"claim":"Identified Ser392 as the PKC phosphorylation site and defined the PH-domain electrostatic switch by which phosphorylation displaces the enzyme from the membrane and inhibits exchange.","evidence":"In vitro phosphorylation, membrane binding and exchange assays with S392A mutant, in vivo translocation","pmids":["10531036"],"confidence":"High","gaps":["Upstream PKC isoform not defined","Physiological trigger for dephosphorylation unresolved"]},{"year":2000,"claim":"Refined the lipid code—PH domain confers PIP3>PIP2 specificity while the polybasic C-terminus adds non-specific anionic binding—and connected CYTH2 catalysis to GPCR desensitization independent of PI3K.","evidence":"Lipid vesicle cosedimentation, in vitro exchange on vesicles, cell-free LH/CGR desensitization assay with E156K and PH mutants","pmids":["10801341","10811902"],"confidence":"Medium","gaps":["Mechanistic link between ARF activation and beta-arrestin release incompletely defined"]},{"year":2001,"claim":"Defined the migration output of CYTH2 as ARF6-dependent and bifurcating into parallel Rac1 and PLD pathways, and showed V-ATPase-driven acidification recruits CYTH2/ARF6 to apical endosomes.","evidence":"ARF6-GTP and Rac pulldowns, PLD inhibitors, migration assays in MDCK; pH-dependent translocation assays with V-ATPase inhibitors; in vitro Sec7/ARF core domain-swap exchange assays","pmids":["11481345","11278939","11342560"],"confidence":"High","gaps":["Identity of the Rac-GEF executing ARF6→Rac not yet known","Molecular nature of the V-ATPase contact unresolved"]},{"year":2002,"claim":"Began assigning scaffolding functions to the N-terminal coiled-coil, showing it recruits CASP to membrane ruffles.","evidence":"Yeast two-hybrid, pull-down, co-IP and immunofluorescence in EGF-stimulated cells","pmids":["12052827"],"confidence":"Medium","gaps":["Functional consequence of CASP recruitment for ARF signaling not established"]},{"year":2003,"claim":"Identified coiled-coil partner IPCEF1 as a positive regulator of exchange and co-translocation, and showed CYTH2 mediates insulin-driven ARF/PLD activation with domain-specific contributions.","evidence":"Yeast two-hybrid, pull-down, co-IP, ARF-GTP assays; domain-deletion ARNO in insulin-stimulated cells; NMR/epistasis defining axonal roles","pmids":["12920129","12969509","14565977","14739276"],"confidence":"Medium","gaps":["How IPCEF1 enhances catalysis mechanistically not resolved","Neuronal substrate of ARF6 incompletely defined"]},{"year":2005,"claim":"Connected CYTH2 to receptor-proximal sustained ERK signaling and identified the Dock180/Elmo complex as the executor of ARF6→Rac1 during migration.","evidence":"Yeast two-hybrid/co-IP for A2A receptor binding with inducible dominant-negatives; epistasis with catalytically dead Dock180 and Elmo mutants in MDCK","pmids":["16027149","16213822"],"confidence":"High","gaps":["How ARF6-GTP recruits Dock180/Elmo mechanistically not shown"]},{"year":2006,"claim":"Defined the V-ATPase a2-subunit as a direct Sec7-domain interactor coupling endosomal acidification to ARF activation and trafficking, and established apical-specific localization governed by the coiled-coil.","evidence":"Co-IP, dominant-negatives, bafilomycin/concanamycin inhibition, endocytosis assays; GFP-ARNO localization and pIgR endocytosis with deletion mutants","pmids":["16415858","16484220"],"confidence":"High","gaps":["Structural detail of the a2N–Sec7 contact not yet resolved"]},{"year":2007,"claim":"Mapped Gαq and ARL4D as upstream activators/recruiters of CYTH2 acting through the coiled-coil and PH/polybasic domains respectively, expanding the inputs that gate ARF6 output.","evidence":"Co-IP with purified proteins, coiled-coil deletion mutants, ARF6 activation, GFP-ARNO translocation with siRNA and E156K controls","pmids":["16650966","17846866","17804820","17623778"],"confidence":"Medium","gaps":["Competition/hierarchy among multiple recruiters in a single cell unresolved"]},{"year":2010,"claim":"Established that CYTH2 is allosterically activated on membranes by ARF-GTP, defining a positive-feedback bistable switch, and identified scaffolds (GRASP/IPCEF1) and adaptors (paxillin) coordinating ARF-to-Rac signaling and migration.","evidence":"Kinetic liposome exchange assays with PH-domain mutants and effector competition; siRNA epistasis of GRASP/IPCEF1; paxillin domain-mapped co-IP and migration assays","pmids":["21118813","20016009","20525696"],"confidence":"High","gaps":["In vivo evidence for the bistable switch lacking","Spatiotemporal triggering of feedback in cells not defined"]},{"year":2011,"claim":"Extended high-affinity PH-domain partnerships to aldolase and placed CYTH2 in a sequential Arf6→Cdc42→Rac1 cascade driving glucose-stimulated insulin secretion.","evidence":"SPR binding with recombinant proteins and siRNA; siRNA/dominant-negative/SecinH3 with sequential GTPase pulldowns in beta-cells and islets","pmids":["21307348","21276423"],"confidence":"Medium","gaps":["Physiological role of aldolase binding unclear","Direct effectors linking Arf6 to Cdc42 not identified"]},{"year":2012,"claim":"Demonstrated CYTH2 as an inflammatory effector via a direct MYD88–ARNO–ARF6 complex controlling endothelial barrier integrity, validating pharmacological inhibition (SecinH3) in vivo; and identified it as a host factor for Salmonella invasion.","evidence":"Co-IP/direct binding, dominant-negatives, permeability assays, in vivo arthritis model; RNAi screen and invasion assays with WRC recruitment","pmids":["23143332","22341462"],"confidence":"High","gaps":["How MYD88 binding activates ARF6 mechanistically not detailed"]},{"year":2013,"claim":"Resolved the structural mechanism of V-ATPase a-subunit inhibition of GEF activity (a2N competing with ARF switch 2) and demonstrated druggable pockets on the Sec7 surface.","evidence":"In vitro GEF assays, NMR structure of a2N(1-17), docking, conservation across a-subunit isoforms; fragment-based design with X-ray Sec7–fragment complexes","pmids":["23288846","24112024"],"confidence":"High","gaps":["Cellular conditions selecting V-ATPase inhibition vs activation not defined"]},{"year":2014,"claim":"Established physiological roles in platelet granule secretion (constitutive ARF6 suppression relieved by PKC), neurite vesicle transport via CCDC120, preadipocyte migration, and identified the RLIP76 N-terminus as a CYTH2 partner.","evidence":"Phospho-IP/MS and aggregometry in platelets; CCDC120 co-IP/siRNA rescue with live imaging; inhibitor panels with ARF6/ERK assays; RLIP76 domain-mapped co-IP with functional assays","pmids":["24581425","25326380","25450674","25450693"],"confidence":"Medium","gaps":["PKC site in platelet context not pinpointed","RLIP76 phospho-regulation of CYTH2 binding incompletely defined"]},{"year":2015,"claim":"Demonstrated an in vivo requirement for CYTH2 in Schwann cell myelination (conditional knockout reduces ARF6 activity and myelin) and defined RLIP76-linked R-Ras/integrin recycling through recycling endosomes.","evidence":"Schwann cell conditional knockout with EM myelin measurement and ARF6 assays; RLIP76 domain mutants, EHD1/Rab11 localization, GEF-dead E156K, integrin recycling assays","pmids":["25824033","26498519","26378252"],"confidence":"High","gaps":["Downstream ARF6 effectors in myelination not identified"]},{"year":2016,"claim":"Showed CYTH2 acting through ARF1 (not solely ARF6) is required for podosome assembly by suppressing a RhoA/myosin-IIA axis.","evidence":"siRNA, pharmacological inhibition, ARF1-GTP pulldown, constitutively active ARF1, myosin-IIA inhibition rescue in multiple cell types","pmids":["28007915"],"confidence":"High","gaps":["Link between ARF1-GTP and RhoA suppression mechanistically open"]},{"year":2019,"claim":"Structurally characterized direct CYTH2 binding to the EGFR juxtamembrane segment, embedding it in a regulated receptor-proximal modulatory network.","evidence":"NMR of the ARNO–EGFR JM interface and direct binding assays","pmids":["31780432"],"confidence":"Medium","gaps":["No full cellular functional validation of the EGFR interaction"]},{"year":2018,"claim":"Uncovered a GEF-activity-independent function: the IBD risk protein INAVA stably binds CYTH2 to drive junctional F-actin and to restrain TRAF6-dependent inflammatory ubiquitination.","evidence":"Co-IP/domain binding, F-actin assays, GEF-dead ARNO, TRAF6 ubiquitination assays in epithelial cells and macrophages","pmids":["30355448"],"confidence":"High","gaps":["Mechanism by which ARNO binding modulates CUPID/TRAF6 not fully resolved"]},{"year":2021,"claim":"Extended CYTH2 to neuronal physiology and viral infection: it complexes with mGluR5 to drive spinal pain signaling, stabilizes CNKSR2 against degradation in hippocampal neurons, and is required for influenza endosomal trafficking.","evidence":"Conditional knockout mice with behavioral/Arf6/ERK assays; co-IP with shRNA and proteasome rescue; genome-wide CRISPR screen with knockout and SecinH3 in vivo","pmids":["34390832","34800437","35354039"],"confidence":"High","gaps":["How CYTH2 binding prevents CNKSR2 degradation mechanistically open"]},{"year":2022,"claim":"Defined Tyr381 phosphorylation (SH2B1 writer / PTP4A1 eraser) as a myelination control switch, linked the CYTH2/ARF1 axis to JNK–IRE1–XBP1 signaling in osteoclasts, and showed FE65 potentiates ARF6-driven neurite outgrowth by relieving ARNO autoinhibition.","evidence":"Y381F knockin and conditional knockdowns with phospho-antibody and ARF6 assays; siRNA/SecinH3 with RNA-seq and pathway assays in OVX osteoporosis model; FE65 co-IP and neurite outgrowth with dimerization mutants","pmids":["35077201","36252772","36168805"],"confidence":"High","gaps":["How Tyr381 phosphorylation alters GEF behavior structurally not defined"]},{"year":2023,"claim":"Placed the V-ATPase V0a1 subunit as an upstream activator of the ARNO–Arf6–PLD1 pathway during regulated exocytosis in neuroendocrine cells.","evidence":"Co-IP, interaction disruption, PLD/phosphatidic acid/exocytosis-timing and Arf6 assays","pmids":["37091866"],"confidence":"Medium","gaps":["Direct activation mechanism by V0a1 versus a2N inhibition not reconciled"]},{"year":2026,"claim":"Established that CYTH2 is essential for organismal viability and maintains Golgi volume and global protein secretion through an ARF-GEF-independent activity, separating its catalytic and structural roles.","evidence":"Full knockout mouse (perinatal lethality), organellar/quantitative proteomics, peanut agglutinin staining, ARF-GEF-independent re-expression rescue","pmids":["41672711"],"confidence":"High","gaps":["Molecular basis of the ARF-GEF-independent Golgi function unknown","Cause of perinatal lethality not pinpointed"]},{"year":null,"claim":"How CYTH2 integrates its many competing recruiters and post-translational switches to select a specific ARF (ARF1 vs ARF6) and a specific downstream output in a given cellular context remains unresolved, as does the molecular basis of its ARF-GEF-independent Golgi/secretory function.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified model for context-dependent ARF1/ARF6 selectivity","ARF-GEF-independent mechanism uncharacterized","Structural picture of full-length autoinhibited vs activated enzyme on membranes incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,3,11,13,30]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,3,30]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[5,9,8]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[14,15,28,53]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,5,7,23]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[12,22,44]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,12]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[55]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[12,22,23,54]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[11,20,24,34]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[43,44,55]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[34,46]}],"complexes":["MYD88–ARNO–ARF6 complex","ARNO–Dock180/Elmo Rac signaling complex","ARNO–ARF6–FE65 complex"],"partners":["ARF6","ARF1","IPCEF1","ARL4D","MYD88","GNAQ","RALBP1","INAVA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q99418","full_name":"Cytohesin-2","aliases":["ARF exchange factor","ARF nucleotide-binding site opener","Protein ARNO","PH, SEC7 and coiled-coil domain-containing protein 2"],"length_aa":400,"mass_kda":46.5,"function":"Acts as a guanine-nucleotide exchange factor (GEF). Promotes guanine-nucleotide exchange on ARF1, ARF3 and ARF6. Activates ARF factors through replacement of GDP with GTP (By similarity). The cell membrane form, in association with ARL4 proteins, recruits ARF6 to the plasma membrane (PubMed:17398095). Involved in neurite growth (By similarity)","subcellular_location":"Cell membrane; Cytoplasm; Cell projection; Cell projection, growth cone; Cell junction, tight junction; Cell junction, adherens junction","url":"https://www.uniprot.org/uniprotkb/Q99418/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CYTH2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CYTH2","total_profiled":1310},"omim":[{"mim_id":"619948","title":"INTERACTION PROTEIN FOR CYTOHESIN EXCHANGE FACTORS 1; IPCEF1","url":"https://www.omim.org/entry/619948"},{"mim_id":"618051","title":"INNATE IMMUNITY ACTIVATOR; INAVA","url":"https://www.omim.org/entry/618051"},{"mim_id":"617476","title":"CNKSR FAMILY, 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Efficient activation of full-length ARF1 requires two distinct protein-phospholipid interactions: PH domain binding PIP2 and electrostatic interactions between ARF1 N-terminal cationic residues and anionic phospholipids.\",\n      \"method\": \"In vitro nucleotide exchange assay on soluble truncated ARF1 ([Δ17]ARF1) and full-length myristoylated ARF1 with liposomes; isolation of stable Sec7-nucleotide-free ARF1 complex\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified proteins and lipid vesicles, multiple conditions tested, mechanistically informative\",\n      \"pmids\": [\"9268368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Crystal structure of the Sec7 domain of ARNO resolved at 2.0 Å; the domain is an elongated all-helical protein with a conserved hydrophobic groove and adjacent loop identified as the ARF-interacting surface. Structure-based mutagenesis confirmed the groove and loop as the ARF1-binding site.\",\n      \"method\": \"X-ray crystallography at 2.0 Å; structure-based mutagenesis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis validation, replicated independently by two groups (PMID 9476900)\",\n      \"pmids\": [\"9510256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Crystal structure of the Sec7 domain of ARNO determined at 2.2 Å; protein footprinting mapped ARF1 interaction sites to the switch 1 and switch 2 GTPase regions, providing a model for ARF GTPase–Sec7 domain exchange factor interaction.\",\n      \"method\": \"X-ray crystallography at 2.2 Å; protein footprinting experiments\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with footprinting, independent replication of Sec7 structure\",\n      \"pmids\": [\"9476900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Glu156 in the hydrophilic loop of the ARNO Sec7 domain acts as a 'glutamic finger' that destabilizes Mg2+ and GDP from ARF1. Conservative mutation E156D and charge-reversal E156K each reduce exchange activity by several orders of magnitude. E156K forms a complex with Mg2+-free ARF1-GDP without inducing GDP release. Lys73 of ARF1 switch II forms an ion pair with Asp183 of ARNO-Sec7.\",\n      \"method\": \"Site-directed mutagenesis; in vitro nucleotide exchange assays; stable complex isolation\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with in vitro exchange assays, multiple mutants tested, specific residue identified\",\n      \"pmids\": [\"9649435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"ARNO localizes to the plasma membrane in mammalian cells (not the Golgi) and stimulates nucleotide exchange on both ARF1 and ARF6 in vitro, indicating its likely in vivo function is at the plasma membrane through ARF6 modulation.\",\n      \"method\": \"Subcellular fractionation; immunolocalization; in vitro nucleotide exchange assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — orthogonal methods (fractionation + immunolocalization + in vitro assay); replicated across multiple subsequent studies\",\n      \"pmids\": [\"9417041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"ARNO PH domain binds PIP3 with higher affinity than PI(4,5)P2; insulin stimulation of 3T3-L1 adipocytes causes rapid PI3K-dependent, PH-domain-dependent translocation of GFP-ARNO to the plasma membrane. Translocation is blocked by wortmannin, LY294002, and dominant-negative p85.\",\n      \"method\": \"GFP-ARNO live imaging in adipocytes; PI3K inhibitors; dominant-negative p85 co-expression; in vitro PIP3 binding assay\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging, pharmacological inhibition, dominant-negative genetics, and in vitro binding; replicated by subsequent studies\",\n      \"pmids\": [\"9550703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"ARNO overexpression in vivo inhibits the early secretory pathway and causes Golgi disassembly; newly synthesized cargo fails to acquire endoglycosidase H resistance, indicating a block in ER-to-Golgi or early Golgi transport. ARNO overexpression does not affect early endocytosis.\",\n      \"method\": \"Immunofluorescence; cell fractionation; SEAP secretion assay; endoglycosidase H sensitivity assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal functional assays in single lab, overexpression approach\",\n      \"pmids\": [\"9788883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"PKC phosphorylates ARNO in vivo; co-treatment of ARNO-expressing HeLa cells with PKC agonist PMA induces redistribution of ARNO, ARF6, and actin into lamellipodia-like membrane protrusions. This actin rearrangement requires ARNO catalytic activity and the PH domain (membrane localization). Deletion of the PH domain abolishes cytoskeletal reorganization.\",\n      \"method\": \"PKC phosphorylation assay; overexpression of WT and catalytically inactive ARNO mutants; immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional mutants and PKC phosphorylation assay, single lab\",\n      \"pmids\": [\"9802902\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PKC phosphorylates ARNO at S392 within its C-terminal polybasic domain, negatively regulating exchange activity through a 'PH domain electrostatic switch': introducing a negative charge reduces ARNO membrane interaction both in vitro and in vivo, and inhibits exchange in vitro. This represents electrostatic regulation of PH-domain-dependent membrane binding.\",\n      \"method\": \"In vitro phosphorylation; membrane binding assays; in vitro nucleotide exchange assay; S392A mutagenesis\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis plus in vivo translocation assay, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"10531036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ARNO PH domain provides specific PIP3 > PIP2 binding; the polybasic C-terminal extension contributes non-specific ionic interactions with acidic phospholipids. PKC phosphorylation of Ser in the C domain reduces ionic affinity for PS but does not affect phosphoinositide specificity. PIP3 is more stimulatory than PIP2 for ARNO-catalyzed ARF activation on vesicles.\",\n      \"method\": \"Cosedimentation of PH+C and nominal PH domain constructs with lipid vesicles; in vitro exchange assays on vesicles\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple lipid compositions, single lab\",\n      \"pmids\": [\"10801341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ARNO promotes release of beta-arrestin from its membrane docking site in ovarian follicular membranes, enabling beta-arrestin binding to the LH/CGR third intracellular loop and receptor desensitization. This requires ARNO catalytic activity (E156K blocks desensitization) and PH domain-mediated membrane association. LH/CGR activation of ARNO is PI3K-independent and Gβγ-independent.\",\n      \"method\": \"Cell-free plasma membrane desensitization assay; Western blot for beta-arrestin; dominant-negative and PH-domain mutant ARNO\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-free membrane assay with multiple mutants, single lab\",\n      \"pmids\": [\"10811902\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ARNO catalytic activity (GEF for ARF6, not ARF1) drives MDCK epithelial cell migration and lamellipodium formation. ARNO-induced motility requires downstream activation of Rac1 and phospholipase D (PLD), which operate as two distinct parallel pathways: PLD inhibition blocks motility without preventing Rac activation.\",\n      \"method\": \"Dominant-negative and active mutant expression; pulldown ARF6-GTP assay; Rac activation assay; PLD inhibitors; migration assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (ARF6 pulldown, Rac assay, PLD inhibition, migration assay) replicated by subsequent studies\",\n      \"pmids\": [\"11481345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ARNO and ARF6 are recruited from cytosol to proximal tubule apical endosomes in a pH-dependent manner driven by V-ATPase-dependent acidification; translocation is reversed by V-ATPase inhibitors and pH uncouplers, and correlates with intra-endosomal acidification magnitude.\",\n      \"method\": \"Subcellular fractionation; translocation assay with ATP-driven acidification; Western blot; V-ATPase inhibitors\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct translocation assay with pharmacological reversal, independent replication by subsequent V-ATPase study (PMID 16415858)\",\n      \"pmids\": [\"11278939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"In vitro, ARNO activates ARF1 preferentially and ARF6 only slightly; these selectivities are determined by the Sec7 domains alone and by the ARF core domains (not the N-terminal myristoylated helix), without depending on PH or N-terminal domains.\",\n      \"method\": \"In vitro exchange assay on membranes with isolated Sec7 domains and ARF core domains; chimeric ARF constructs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with domain-swap mutants, single lab\",\n      \"pmids\": [\"11342560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The N-terminal coiled-coil domain of ARNO/cytohesin-2 interacts with the scaffolding protein CASP via CASP's internal coiled-coil motif. In EGF-stimulated cells, cytohesin recruits CASP to membrane ruffles, demonstrating a functional interaction.\",\n      \"method\": \"Yeast two-hybrid screening; in vitro pull-down; co-immunoprecipitation in COS-1 cells; immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid + pull-down + co-IP, single lab, multiple methods\",\n      \"pmids\": [\"12052827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"IPCEF1 binds the coiled-coil domain of cytohesin-2; cytohesin-2 binding domain maps to the C-terminal 121 aa of IPCEF1. Interaction confirmed in mammalian cells by co-IP. IPCEF1 increases both in vitro and in vivo ARF-GTP formation by cytohesin-2; IPCEF1 co-migrates with cytohesin-2 to the plasma membrane in EGF-stimulated cells only when the binding site is intact.\",\n      \"method\": \"Yeast two-hybrid; GST pull-down; co-immunoprecipitation; ARF-GTP formation assay; immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding assays plus functional exchange enhancement, single lab\",\n      \"pmids\": [\"12920129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"ARNO mediates ARF activation and PLD activity downstream of insulin signaling; insulin-induced ARNO translocation to plasma membrane requires the PH domain, and the Sec7 domain is required for downstream ARF translocation and PLD activation. The coiled-coil domain contributes to partial membrane targeting.\",\n      \"method\": \"Transient transfection of WT and domain-deletion/Sec7-mutant ARNO in HIRcB cells; insulin stimulation; ARF translocation assay; PLD activity assay\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple domain mutants with functional readouts, single lab\",\n      \"pmids\": [\"12969509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"ARNO and ARF6 regulate axonal elongation and branching in hippocampal neurons; catalytically inactive ARNO or dominant-negative ARF6 enhance axonal extension and branching. PI(4)P 5-kinase alpha acts downstream of ARF6 to regulate neurite extension. Inactive ARNO/ARF6 depletes Mena from growth cone leading edges.\",\n      \"method\": \"Expression of dominant-negative and constitutively active constructs in cultured rat hippocampal neurons; immunofluorescence for Mena; epistasis by co-expression\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with multiple constructs, defined cellular phenotype, single lab\",\n      \"pmids\": [\"14565977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"NMR analysis of Arf1 complexed with ARNO-Sec7; Glu156 is required to promote GDP release (E156A and E156K mutants release Mg2+ from Arf1-GDP but do not promote GDP release); the wild-type Sec7 domain weakly competes with GDP on Arf1-GDP-Mg2+ and leads to GDP release; ARNO-Sec7 does not interact appreciably with GTP-bound Arf1.\",\n      \"method\": \"31P NMR spectroscopy; Arf1-GDP/GTP-Mg2+ complex analysis; mutant ARNO-Sec7 interaction studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural/biochemical analysis with mutants, single lab\",\n      \"pmids\": [\"14739276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Cytohesin-2 is required for serum response element (SRE)-mediated transcriptional activation and MAPK signaling; an RNA aptamer specific for cytohesin-2 (discriminating it from cytohesin-1) binds the N-terminal coiled-coil/Sec7 interface and in vivo downregulates SRE-mediated gene expression and MAPK activation. Cytohesin-1 does not substitute for this function.\",\n      \"method\": \"RNA aptamer ('intramer') transfection; SRE-reporter assay; MAPK activation assay in HeLa cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific inhibitory aptamer with functional readout, single lab, novel reagent\",\n      \"pmids\": [\"15277685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ARNO directly binds the C-terminus (juxtamembrane portion) of the A2A adenosine receptor; this interaction is required for the sustained (heterotrimeric G protein-independent) phase of ERK/MAP kinase activation. Dominant-negative ARNO (E156K) and dominant-negative ARF6 (T27N) abolish sustained MAP kinase stimulation but do not affect cAMP accumulation or receptor desensitization.\",\n      \"method\": \"Yeast two-hybrid; mutual pull-down of bacterial fusion proteins; co-immunoprecipitation in mammalian cells; inducible dominant-negative cell lines; cAMP and ERK assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct interaction confirmed by three independent methods plus functional epistasis with inducible expression system\",\n      \"pmids\": [\"16027149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ARNO-dependent Rac1 activation in migrating MDCK cells is mediated by the Dock180/Elmo bipartite Rac-GEF complex. Catalytically inactive Dock180 and an Elmo mutant that cannot couple to Dock180 both block ARNO-induced Rac activation and motility. Beta-PIX (another Rac-GEF) does not mediate this pathway.\",\n      \"method\": \"Dominant-negative Dock180 and Elmo mutant expression; co-localization; Rac activation assay; migration assay in MDCK cells\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis with multiple dominant-negative constructs and specificity controls, replicated in context\",\n      \"pmids\": [\"16213822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ARNO interacts with the a2-isoform of V-ATPase on early endosomes in an intra-endosomal acidification-dependent manner; ARF6 interacts with the c-subunit. Disruption of the V-ATPase–ARNO interaction reversibly inhibits endocytosis. Inhibition of endosomal acidification blocks protein trafficking from early to late endosomes.\",\n      \"method\": \"Co-immunoprecipitation; subcellular fractionation; dominant-negative constructs; bafilomycin/concanamycin A inhibition; endocytosis assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP plus functional inhibition assays, independently replicated by prior proximal tubule study (PMID 11278939)\",\n      \"pmids\": [\"16415858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In polarized epithelial cells, ARNO localizes exclusively to the apical plasma membrane and regulates apical endocytosis; ARF6 co-expression synergistically stimulates apical endocytosis. The N-terminal coiled-coil domain is required for apical specificity: deletion causes ARNO mislocalization to both membranes, and expression of the CC domain alone abolishes apical endocytosis.\",\n      \"method\": \"GFP-ARNO expression in MDCK cells; polymeric immunoglobulin receptor endocytosis assay; deletion mutants; immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional consequence, multiple mutants, single lab\",\n      \"pmids\": [\"16484220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Activated Gαq forms molecular complexes with ARNO and ARF6, preferentially with GTP-bound Gαq. Gαq interacts directly with ARNO (binding experiments with purified proteins). Gαq-dependent ARF6 activation leads to PI(4,5)P2 production and TPβ receptor internalization, both blocked by dominant-negative ARNO and ARF6.\",\n      \"method\": \"Co-immunoprecipitation; purified protein binding assay; dominant-negative mutants; ARF6-GTP pulldown; PI(4,5)P2 assay; receptor internalization assay\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding with purified proteins plus co-IP and functional assays, single lab\",\n      \"pmids\": [\"16650966\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ARL4D recruits cytohesin-2/ARNO to the plasma membrane in a GTP- and N-terminal myristoylation-dependent manner through direct interaction with the ARNO PH and polybasic C domains. Active ARL4D increases GTP-ARF6 levels and induces actin stress fiber disassembly; this requires ARNO catalytic activity and ARNO expression (inactive ARNO E156K or ARNO siRNA blocks ARL4D-mediated actin effects). ARL4D-induced CYTH2 translocation is PI3K-independent.\",\n      \"method\": \"Co-immunoprecipitation; GFP-ARNO translocation assay; ARF6-GTP pulldown; siRNA knockdown; dominant-negative ARNO; immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (Co-IP, translocation, ARF6 activation, siRNA, dominant-negative), single lab\",\n      \"pmids\": [\"17804820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The coiled-coil domain of the cytohesin/ARNO family interacts with Gαq; cytohesin-2/ARNO and cytohesin-1 mutants lacking the coiled-coil domain cannot relay Gαq-mediated ARF6 activation. Cytohesin-1 preferentially associates with constitutively active Gαq-Q209L.\",\n      \"method\": \"Co-immunoprecipitation; coiled-coil deletion mutants; ARF6 activation assay; immunofluorescence\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus functional deletion mutant assays, single lab\",\n      \"pmids\": [\"17846866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CaSR stimulation induces plasma membrane ruffling via a pathway involving beta-arrestin 1, ARNO, ARF6, and ELMO. Beta-arrestin 1 co-immunoprecipitates with CaSR and ARNO under resting conditions; agonist treatment causes translocation of CaSR, beta-arrestin 1, and ARNO to membrane protrusions. Catalytically inactive ARNO reduces ruffling. ARF6 and ELMO are required downstream.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; dominant-negative ARNO; dominant-negative beta-arrestin 1; immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, siRNA, dominant-negatives with defined phenotypic readout, single lab\",\n      \"pmids\": [\"17623778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"ARNO-induced Rac activation and migration require the coiled-coil domain; the coiled-coil promotes assembly of a multiprotein complex containing ARNO and Dock180. Knockdown of either GRASP/Tamalin or IPCEF1 (which bind the ARNO coiled-coil) prevents ARNO–Dock180 association and ARNO-induced Rac activation, placing scaffold proteins as coordinators of ARF-to-Rac signaling.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown of GRASP and IPCEF1; coiled-coil deletion mutant; Rac activation assay; migration assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple siRNA knockdowns with mechanistic epistasis, single lab\",\n      \"pmids\": [\"20016009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Paxillin (focal adhesion adaptor) forms a complex with cytohesin-2 mediated by the LIM2 domain of paxillin and the polybasic region of cytohesin-2. Paxillin co-localizes with cytohesin-2 at leading edges of migrating 3T3-L1 cells. siRNA knockdown of cytohesin-2 inhibits migration and its effects are upstream of ARF6.\",\n      \"method\": \"Co-immunoprecipitation; domain mapping with deletion mutants; siRNA knockdown; migration assay; immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping plus siRNA and migration assay, single lab\",\n      \"pmids\": [\"20525696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"On model membranes, Arf6-GTP activates Arno at nanomolar concentrations (vs. micromolar in solution); mutations in the PH domain abolishing Arf6-GTP interaction render Arno completely inactive on liposomes but not in solution. Arno is also activated by its own product Arf1-GTP (positive feedback), behaving as a bistable switch requiring an Arf activator; Arno activity is modulated by competition with Arf effectors.\",\n      \"method\": \"Kinetic nucleotide exchange assays on liposomes with membrane-anchored full-length Arf1 and Arf6; PH domain mutants; competition experiments with Arf effectors\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted system on liposomes with full-length proteins, multiple mutants, mechanistic model validated quantitatively\",\n      \"pmids\": [\"21118813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The N-terminus of the V-ATPase a2-subunit interacts with multiple domains of ARNO; the a2N-01 peptide (MGSLFRSESMCLAQLFL) specifically binds the Sec7 domain with KD ~3.44×10⁻⁷ M. In silico docking shows a2N competes with switch 2 of Arf1/Arf6 for Sec7 domain binding. Phosphorylation of ARNO Ser392 abolishes a2N binding to the ARNO PB domain.\",\n      \"method\": \"Synthetic peptide pull-down assays; surface plasmon resonance; NMR structure determination of peptides; homology modeling/in silico docking\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — SPR binding kinetics + NMR structure + docking, single lab\",\n      \"pmids\": [\"20153292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"ARNO directly interacts with aldolase via the ARNO PH domain; surface plasmon resonance yields KD = 2.84×10⁻¹⁰ M. Aldolase associates with early endosomal membranes. Aldolase knockdown in HeLa cells causes morphological changes and acidic vesicle redistribution, and is inversely correlated with gelsolin levels.\",\n      \"method\": \"Pull-down with recombinant proteins (GST-PH domain); surface plasmon resonance; subcellular fractionation; siRNA knockdown; immunofluorescence\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SPR binding with recombinant proteins plus siRNA functional assay, single lab\",\n      \"pmids\": [\"21307348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"ARNO promotes sequential activation of Arf6, then Cdc42, then Rac1 in pancreatic β-cells to stimulate glucose-stimulated insulin secretion (GSIS). siRNA-ARNO, dominant-negative ARNO (E156K), and SecinH3 each inhibit GSIS and block glucose-induced Arf6 activation in INS 832/13 cells and rat islets. ARNO–Arf6 complex association increases in glucose-stimulated β-cells.\",\n      \"method\": \"siRNA knockdown; dominant-negative mutant expression; SecinH3 inhibitor; GST-GGA3 ARF6-GTP pulldown; PAK-1 Rac/Cdc42 pulldown; co-immunoprecipitation; confocal microscopy\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple approaches (siRNA, dominant-negative, inhibitor) with sequential GTPase activation assays, single lab\",\n      \"pmids\": [\"21276423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ARNO directly binds the adaptor protein MYD88, forming a MYD88–ARNO–ARF6 signaling complex. IL-1β activates ARF6 through this pathway in endothelial cells in an NF-κB-independent manner, disrupting endothelial barrier function. SecinH3 (ARNO inhibitor) enhances vascular stability and improves outcomes in animal models of inflammatory arthritis.\",\n      \"method\": \"Co-immunoprecipitation; direct binding assays; dominant-negative ARF6/ARNO; in vitro permeability assay; in vivo inflammatory arthritis model with SecinH3\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding confirmed, functional epistasis in vitro and in vivo, published in Nature\",\n      \"pmids\": [\"23143332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"During Salmonella invasion, ARNO is recruited via Arf6 and SopB-induced PIP3 generation; ARNO in turn triggers WAVE regulatory complex (WRC) recruitment and activation for membrane ruffling and macropinosome formation. RNAi screening identified ARNO as a key host Arf-GEF for Salmonella invasion.\",\n      \"method\": \"RNAi screen; siRNA knockdown; fluorescence microscopy; invasion assay; Arf6-GTP pulldown\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi screen plus functional validation, pathway placement, single lab\",\n      \"pmids\": [\"22341462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The N-terminal cytosolic tail of V-ATPase a2-subunit (first 17 aa, a2N(1-17)) potently inhibits cytohesin-2 GEF activity by directly interacting with the Sec7 domain, competing with ARF switch 2. Structure of a2N(1-17) and key residues Phe5, Met10, Gln14 involved in Sec7 binding were determined by NMR. This signaling mechanism is conserved across all four mammalian V-ATPase a-subunit isoforms.\",\n      \"method\": \"In vitro GEF activity assay; NMR spectroscopy; in silico docking; pull-down with recombinant proteins; binding to intact yeast V-ATPase\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro functional assay + NMR structure + cross-species conservation, multiple orthogonal methods\",\n      \"pmids\": [\"23288846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Fragment-based drug design identified small molecules that bind directly to specific pockets on the ARNO Sec7 domain surface and inhibit Arno-catalyzed nucleotide exchange on ARF1; binding modes of two compounds resolved by X-ray crystallography, revealing stable and transient pockets at the Sec7 surface.\",\n      \"method\": \"SPR; NMR; fluorescence assays; X-ray crystallography of Sec7–fragment complexes; in vitro exchange inhibition assay\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of inhibitor-bound Sec7 domain plus in vitro functional assays\",\n      \"pmids\": [\"24112024\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Cytohesin-2 constitutively suppresses platelet dense granule secretion by maintaining ARF6 in a GTP-bound state; PKC-mediated phosphorylation of cytohesin-2 relieves this suppression. SecinH3 enhances dense granule secretion and aggregation but not α-granule release or αIIbβ3 activation. ARF6 interaction with cytohesin-2 decreases upon platelet stimulation in a PKC-dependent manner.\",\n      \"method\": \"Immunoprecipitation with phosphoserine-PKC antibody; mass spectrometry; lumi-aggregometry; flow cytometry; Western blotting; SecinH3 pharmacological inhibition\",\n      \"journal\": \"Journal of thrombosis and haemostasis : JTH\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS identification plus functional granule secretion assay with inhibitor, single lab\",\n      \"pmids\": [\"24581425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Cytohesin-2 interacts with CCDC120 via the CC1 coiled-coil domain; CCDC120 localizes cytohesin-2 into vesicles that undergo anterograde transport along neurites. CCDC120 knockdown inhibits cytohesin-2 vesicular localization, Arf6 activation, and neurite growth; these are rescued by WT CCDC120 but not by CC1-domain-deficient CCDC120.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; live vesicle transport imaging; Arf6-GTP assay; rescue experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, siRNA rescue, live imaging, single lab\",\n      \"pmids\": [\"25326380\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Cytohesin-2 activates ARF6 in a PI3K-dependent manner; active ARF6 causes ERK1/2 phosphorylation during preadipocyte migration. Dynamin inhibition blocks migration but not ARF6 or ERK1/2 activation.\",\n      \"method\": \"siRNA knockdown; pharmacological inhibitors (SecinH3, LY294002, PD98059, dynasore); ARF6-GTP pulldown; ERK phosphorylation by Western blot; migration assay\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple inhibitors + siRNA with ARF6 and ERK activation assays, single lab\",\n      \"pmids\": [\"25450674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RLIP76 N-terminal domain (residues 1-180) binds ARNO; Ser29/30 in the N-terminus are required for ARNO interaction and for RLIP76-dependent cell spreading, migration, Arf6 activation, and PI3K activation. Ser62 supports ARNO binding and Arf6 activation but Ser62A still blocks Rac1 activation.\",\n      \"method\": \"Co-immunoprecipitation; domain deletion and point mutants; cell spreading/migration assay; ARF6-GTP pulldown; Rac1 activation assay; PI3K activation assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with multiple mutants plus functional assays, single lab\",\n      \"pmids\": [\"25450693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Cytohesin-2/ARNO regulates myelin sheath thickness in peripheral nerves; Schwann cell-specific conditional knockout of cytohesin-2 reduces Arf6 activity, myelin thickness, and MPZ expression in sciatic nerves without affecting cell proliferation.\",\n      \"method\": \"Schwann cell-specific conditional knockout mouse; myelin thickness measurement (electron microscopy); ARF6-GTP assay; Western blot for MPZ; Ki67 staining; SecinH3 treatment of Schwann cell-neuron co-cultures\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockout with defined cellular phenotype (myelin thickness) and ARF6 activity measurement, in vivo and in vitro convergent results\",\n      \"pmids\": [\"25824033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RLIP76 links ARNO to activated R-Ras at Rab11-positive recycling endosomes; RLIP76 binds ARNO via residues 1-180 and R-Ras via residues 180-192. ARNO localization to recycling endosomes requires RLIP76 and its ARNO-binding domain. Cytohesin-2/ARNO regulates recycling of R-Ras and α5-integrin to the plasma membrane via ARF activation.\",\n      \"method\": \"Co-immunoprecipitation; domain deletion mutants; immunofluorescence; ARF6-GTP assay; integrin recycling assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with multiple deletion mutants plus recycling assay, single lab\",\n      \"pmids\": [\"26498519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Cytohesin-2/ARNO regulates R-Ras and α5-integrin recycling through an EHD1-positive recycling endosome compartment; GEF-inactive ARNO (E156K) accumulates R-Ras on recycling endosomes and inhibits cell spreading; ARNO catalytic activity is required for focal adhesion formation and integrin recycling.\",\n      \"method\": \"Co-localization studies; GEF-inactive E156K-ARNO expression; integrin recycling assay; focal adhesion quantification; siRNA knockdown\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — localization with functional consequence plus GEF-inactive mutant, single lab\",\n      \"pmids\": [\"26378252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ARNO (co-localizing with podosome adhesive rings) and ARF1 are required for podosome assembly; ARNO/ARF1 knockdown or pharmacological inhibition eliminates podosomes and elevates RhoA-GTP and myosin-IIA filaments. Constitutively active ARF1 induces podosome precursor structures. Suppression of myosin-IIA rescues podosome formation despite ARF1 inhibition, placing RhoA/myosin-II downstream of ARNO/ARF1.\",\n      \"method\": \"siRNA knockdown; pharmacological inhibitors; ARF1-GTP pulldown; immunofluorescence; constitutively active ARF1 expression; myosin-IIA inhibition rescue\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — siRNA plus pharmacological inhibition plus genetic epistasis with rescue, defined cellular phenotype, multiple cell types\",\n      \"pmids\": [\"28007915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"INAVA (IBD risk gene) CUPID domain stably binds ARNO and effects F-actin assembly at lateral membranes underlying cell-cell junctions in an ARNO-dependent but GEF-activity-independent manner. Upon IL-1β stimulation, INAVA relocates to cytosolic puncta where CUPID amplifies TRAF6-dependent polyubiquitination; ARNO binding to CUPID negatively-regulates this inflammatory polyubiquitination. INAVA and ARNO act similarly in human macrophages.\",\n      \"method\": \"Co-immunoprecipitation; domain binding assays; F-actin assembly assay; GEF-inactive ARNO; TRAF6 polyubiquitination assay; IL-1β stimulation in epithelial cells and macrophages\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches with GEF-inactive controls in two cell types, bifunctional mechanism established\",\n      \"pmids\": [\"30355448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ARNO directly binds the juxtamembrane (JM) segment of EGFR intracellular domain; the ARNO-EGFR interaction interface was structurally characterized by NMR and shows common features but distinct differences from JM interactions with calmodulin and anionic phospholipids, forming a regulated modulatory network.\",\n      \"method\": \"NMR spectroscopy; direct binding assays\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural characterization of interaction interface, single lab, no full functional validation\",\n      \"pmids\": [\"31780432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CYTH2 (cytohesin-2) is required for the early stage of influenza virus infection by mediating endosomal trafficking; CYTH2 knockout reduces efficient infection, and the CYTH2 antagonist SecinH3 blunts influenza virus infection in vivo.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 screen; CYTH2 knockout validation; SecinH3 in vivo treatment; infection efficiency assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen with genetic knockout validation and in vivo pharmacological inhibition, single study\",\n      \"pmids\": [\"35354039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CNKSR2 forms a molecular complex with CYTH2 in the hippocampus; CYTH2 binding prevents proteasomal degradation of CNKSR2. Knockdown of either CNKSR2 or CYTH2 in granule cell precursors in vivo results in abnormal localization of cells at the granule cell layer/hilus boundary with characteristics of immature granule cells.\",\n      \"method\": \"Co-immunoprecipitation; shRNA knockdown in vivo via viral transduction; immunofluorescence; proteasome inhibitor rescue\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vivo shRNA with defined cellular phenotype, single lab\",\n      \"pmids\": [\"34800437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cytohesin-2 forms a protein complex with mGluR5 in the spinal cord and is enriched in the perisynapse of dorsal horn neurons. CNS-specific cytohesin-2 conditional knockout mice show reduced mechanical allodynia in inflammatory and neuropathic pain models. SecinH3 inhibits spinal Arf6 (not Arf1) activation. Cytohesin-2 knockout reduces ERK1/2 activation following spinal mGluR1/5 activation.\",\n      \"method\": \"Co-immunoprecipitation; conditional knockout mice; SecinH3 pharmacological inhibition; mechanical allodynia behavioral testing; Arf6/Arf1-GTP assay; ERK phosphorylation assay\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockout with behavioral and molecular phenotypes, Co-IP for complex, pathway placement, single lab\",\n      \"pmids\": [\"34390832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Phosphorylation of cytohesin-2 at Tyr381 is central to Schwann cell myelination; knockin mice with Y381F mutation show reduced myelin thickness and decreased Arf6 activity. PTP4A1 dephosphorylates cytohesin-2 at Tyr381; SH2B1 maintains phosphorylation. Schwann cell-specific knockdown of PTP4A1 increases cytohesin-2 phosphorylation and myelin thickness; loss of SH2B1 reduces both.\",\n      \"method\": \"Knockin mouse (Y381F); conditional Schwann cell knockdown of PTP4A1 and SH2B1; phospho-specific antibody; ARF6-GTP assay; myelin thickness measurement\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockin mouse plus conditional knockdowns with writer/eraser identified and functional output measured in vivo\",\n      \"pmids\": [\"35077201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cytohesin-2/ARF1 axis positively regulates osteoclast differentiation; blocking it with SecinH3 or cytohesin-2 siRNA inhibits osteoclast formation and function in vitro and ameliorates ovariectomy-induced osteoporosis in vivo. Mechanistically, cytohesin-2/ARF1 activates the JNK pathway; JNK in turn regulates IRE1 endoribonuclease activity (not kinase) to promote XBP1 splicing.\",\n      \"method\": \"siRNA knockdown; SecinH3 pharmacological inhibition; in vivo OVX model; RNA-sequencing; JNK and IRE1 activity assays; XBP1 splicing assay\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA + inhibitor + in vivo model with RNA-seq and pathway characterization, single lab\",\n      \"pmids\": [\"36252772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FE65 neuronal adaptor interacts with ARNO and forms an ARNO–ARF6–FE65 trimeric complex; FE65 potentiates ARNO-stimulated ARF6-mediated neurite outgrowth. FE65 attenuates ARNO intramolecular autoinhibitory interaction and its effect requires ARNO dimerization (monomeric ARNO mutant is not potentiated by FE65).\",\n      \"method\": \"Co-immunoprecipitation; co-localization; FE65 interaction-disrupting mutation; ARF6 activation assay; neurite outgrowth assay\",\n      \"journal\": \"Open biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP, functional mutants, and neurite assay, single lab\",\n      \"pmids\": [\"36168805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"V-ATPase V0a1 subunit interacts with ARNO in neuroendocrine cells; disruption of V0a1–ARNO interaction inhibits Arf6 activation during exocytosis, PLD activation, phosphatidic acid synthesis, and alters fusion event timing. This places V-ATPase as an upstream activator of the ARNO–Arf6–PLD1 pathway during exocytosis.\",\n      \"method\": \"Co-immunoprecipitation; interaction disruption; PLD activity assay; phosphatidic acid measurement; exocytosis timing assay; Arf6-GTP assay in neuroendocrine cells\",\n      \"journal\": \"Frontiers in molecular biosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional inhibition assays with multiple readouts, single lab\",\n      \"pmids\": [\"37091866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Full knockout of cytohesin-2 in mice causes perinatal lethality within 20 h of birth. Cytohesin-2 deficiency reduces Golgi volume in C2 myoblasts (restored by re-expression in an ARF-GEF-independent manner), impairs peanut agglutinin staining (galactose/N-acetyl-galactosamine reduction), and markedly reduces global protein secretion in neonatal knockout mice.\",\n      \"method\": \"Full knockout mouse; mass spectrometry-based organellar proteomics; immunofluorescence; quantitative proteomics; peanut agglutinin staining; re-expression rescue\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — full knockout mouse with multiple orthogonal methods revealing essential Golgi maintenance function; ARF-GEF-independent mechanism established by rescue\",\n      \"pmids\": [\"41672711\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Cytohesin-2/ARNO is a multi-domain ARF guanine nucleotide exchange factor (GEF) whose catalytic Sec7 domain uses a 'glutamic finger' (Glu156) to displace Mg²⁺ and GDP from ARF1/ARF6, while its PH domain recruits it to membranes via PIP3 (and PIP2); membrane localization is further regulated by PKC-mediated phosphorylation of Ser392 (electrostatic switch), Tyr381 phosphorylation status (controlled by SH2B1/PTP4A1), interaction with ARL4D/Arl4D, and V-ATPase a2-subunit binding to the Sec7 domain; once membrane-recruited, cytohesin-2 activates ARF6 (and ARF1 in some contexts) to drive diverse downstream processes including epithelial cell migration (via Dock180/Elmo→Rac1 and PLD pathways), endocytic trafficking, apical endocytosis, neurite outgrowth, Schwann cell myelination, podosome assembly, platelet dense granule secretion, vascular barrier dissolution (via MYD88–ARNO–ARF6), insulin secretion (via Arf6→Cdc42/Rac1), and Golgi volume maintenance (ARF-GEF-independently); its coiled-coil domain scaffolds interactions with CASP, IPCEF1, GRASP, Gαq, and FE65, while its PH/polybasic domain also binds ARL4D, paxillin, RLIP76, and aldolase to coordinate spatial and contextual ARF6 signaling outputs.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CYTH2 (cytohesin-2/ARNO) is a multidomain guanine nucleotide exchange factor that activates ARF GTPases at the plasma membrane and endosomes to couple receptor and lipid signals to membrane remodeling, cytoskeletal dynamics, and vesicular trafficking [#4, #11]. Its catalytic Sec7 domain inserts a 'glutamic finger' (Glu156) that destabilizes Mg²⁺ and GDP to drive nucleotide exchange on ARF1 and ARF6, with the conserved hydrophobic groove engaging the ARF switch regions [#1, #2, #3, #18]. Membrane recruitment is governed by its PH domain, which binds PIP3 in preference to PIP2 to deliver the enzyme to membranes upon PI3K-dependent stimulation (e.g. insulin), while a C-terminal polybasic region adds non-specific ionic contacts; PKC phosphorylation of Ser392 acts as an electrostatic switch that releases the enzyme from the membrane and downregulates exchange [#5, #8, #9]. On membranes the enzyme behaves as a positive-feedback bistable switch, being itself allosterically activated by ARF-GTP through its PH domain [#30]. Through ARF6, CYTH2 drives epithelial cell migration and lamellipodium formation via two parallel outputs—Rac1 activation through the Dock180/Elmo complex and phospholipase D activation [#11, #21], and contributes to neurite/axon outgrowth, Schwann cell myelination, podosome assembly, integrin recycling, insulin and granule secretion, and exocytosis [#17, #42, #45, #44, #33, #38, #54]. Localization, specificity, and signaling context are set by an N-terminal coiled-coil that scaffolds CASP, IPCEF1, GRASP, Gαq, and FE65 and by PH/polybasic interactions with ARL4D, paxillin, RLIP76, and aldolase [#14, #15, #28, #26, #53, #25, #29, #41, #32]. V-ATPase couples endosomal acidification to ARF activation: the a-subunit N-terminus binds the Sec7 domain in competition with ARF switch 2 and modulates GEF activity in a pH-dependent manner [#12, #22, #36]. CYTH2 also relays GPCR and receptor signaling, binding the A2A adenosine receptor, EGFR juxtamembrane segment, and MYD88 to sustain ERK signaling and to control endothelial barrier integrity [#20, #47, #34]. Beyond ARF activation, CYTH2 maintains Golgi volume and global protein secretion in an ARF-GEF-independent manner, and its full knockout is perinatally lethal in mice [#55].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established that CYTH2 is a bona fide ARF GEF and that its catalytic and membrane-targeting functions are separable—the Sec7 domain drives exchange while the PH domain binds PIP2 only for recruitment.\",\n      \"evidence\": \"In vitro nucleotide exchange assays on truncated and full-length myristoylated ARF1 with liposomes\",\n      \"pmids\": [\"9268368\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve atomic catalytic mechanism\", \"ARF6 specificity untested in this system\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined the structural basis of ARF recognition and the catalytic chemistry, identifying the Sec7 hydrophobic groove as the ARF-binding surface and Glu156 as the 'glutamic finger' that expels Mg²⁺ and GDP.\",\n      \"evidence\": \"Crystal structures at 2.0/2.2 Å with footprinting, plus site-directed mutagenesis (E156D/E156K) and stable complex isolation\",\n      \"pmids\": [\"9510256\", \"9476900\", \"9649435\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Static structures did not capture the exchange transition state\", \"Membrane context absent from crystallography\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Placed CYTH2 at the plasma membrane acting on ARF6 in cells while remaining dual-specific in vitro, and linked it to PI3K-dependent, PIP3-driven translocation and PKC-induced actin remodeling.\",\n      \"evidence\": \"Subcellular fractionation, GFP-ARNO live imaging in adipocytes with PI3K inhibitors and dominant-negative p85, PKC phosphorylation and immunofluorescence\",\n      \"pmids\": [\"9417041\", \"9550703\", \"9802902\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo ARF6 vs ARF1 selectivity not quantified\", \"Direct PKC site not yet mapped\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified Ser392 as the PKC phosphorylation site and defined the PH-domain electrostatic switch by which phosphorylation displaces the enzyme from the membrane and inhibits exchange.\",\n      \"evidence\": \"In vitro phosphorylation, membrane binding and exchange assays with S392A mutant, in vivo translocation\",\n      \"pmids\": [\"10531036\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream PKC isoform not defined\", \"Physiological trigger for dephosphorylation unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Refined the lipid code—PH domain confers PIP3>PIP2 specificity while the polybasic C-terminus adds non-specific anionic binding—and connected CYTH2 catalysis to GPCR desensitization independent of PI3K.\",\n      \"evidence\": \"Lipid vesicle cosedimentation, in vitro exchange on vesicles, cell-free LH/CGR desensitization assay with E156K and PH mutants\",\n      \"pmids\": [\"10801341\", \"10811902\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between ARF activation and beta-arrestin release incompletely defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the migration output of CYTH2 as ARF6-dependent and bifurcating into parallel Rac1 and PLD pathways, and showed V-ATPase-driven acidification recruits CYTH2/ARF6 to apical endosomes.\",\n      \"evidence\": \"ARF6-GTP and Rac pulldowns, PLD inhibitors, migration assays in MDCK; pH-dependent translocation assays with V-ATPase inhibitors; in vitro Sec7/ARF core domain-swap exchange assays\",\n      \"pmids\": [\"11481345\", \"11278939\", \"11342560\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the Rac-GEF executing ARF6→Rac not yet known\", \"Molecular nature of the V-ATPase contact unresolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Began assigning scaffolding functions to the N-terminal coiled-coil, showing it recruits CASP to membrane ruffles.\",\n      \"evidence\": \"Yeast two-hybrid, pull-down, co-IP and immunofluorescence in EGF-stimulated cells\",\n      \"pmids\": [\"12052827\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of CASP recruitment for ARF signaling not established\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified coiled-coil partner IPCEF1 as a positive regulator of exchange and co-translocation, and showed CYTH2 mediates insulin-driven ARF/PLD activation with domain-specific contributions.\",\n      \"evidence\": \"Yeast two-hybrid, pull-down, co-IP, ARF-GTP assays; domain-deletion ARNO in insulin-stimulated cells; NMR/epistasis defining axonal roles\",\n      \"pmids\": [\"12920129\", \"12969509\", \"14565977\", \"14739276\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How IPCEF1 enhances catalysis mechanistically not resolved\", \"Neuronal substrate of ARF6 incompletely defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connected CYTH2 to receptor-proximal sustained ERK signaling and identified the Dock180/Elmo complex as the executor of ARF6→Rac1 during migration.\",\n      \"evidence\": \"Yeast two-hybrid/co-IP for A2A receptor binding with inducible dominant-negatives; epistasis with catalytically dead Dock180 and Elmo mutants in MDCK\",\n      \"pmids\": [\"16027149\", \"16213822\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ARF6-GTP recruits Dock180/Elmo mechanistically not shown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined the V-ATPase a2-subunit as a direct Sec7-domain interactor coupling endosomal acidification to ARF activation and trafficking, and established apical-specific localization governed by the coiled-coil.\",\n      \"evidence\": \"Co-IP, dominant-negatives, bafilomycin/concanamycin inhibition, endocytosis assays; GFP-ARNO localization and pIgR endocytosis with deletion mutants\",\n      \"pmids\": [\"16415858\", \"16484220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural detail of the a2N–Sec7 contact not yet resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Mapped Gαq and ARL4D as upstream activators/recruiters of CYTH2 acting through the coiled-coil and PH/polybasic domains respectively, expanding the inputs that gate ARF6 output.\",\n      \"evidence\": \"Co-IP with purified proteins, coiled-coil deletion mutants, ARF6 activation, GFP-ARNO translocation with siRNA and E156K controls\",\n      \"pmids\": [\"16650966\", \"17846866\", \"17804820\", \"17623778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Competition/hierarchy among multiple recruiters in a single cell unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Established that CYTH2 is allosterically activated on membranes by ARF-GTP, defining a positive-feedback bistable switch, and identified scaffolds (GRASP/IPCEF1) and adaptors (paxillin) coordinating ARF-to-Rac signaling and migration.\",\n      \"evidence\": \"Kinetic liposome exchange assays with PH-domain mutants and effector competition; siRNA epistasis of GRASP/IPCEF1; paxillin domain-mapped co-IP and migration assays\",\n      \"pmids\": [\"21118813\", \"20016009\", \"20525696\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo evidence for the bistable switch lacking\", \"Spatiotemporal triggering of feedback in cells not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended high-affinity PH-domain partnerships to aldolase and placed CYTH2 in a sequential Arf6→Cdc42→Rac1 cascade driving glucose-stimulated insulin secretion.\",\n      \"evidence\": \"SPR binding with recombinant proteins and siRNA; siRNA/dominant-negative/SecinH3 with sequential GTPase pulldowns in beta-cells and islets\",\n      \"pmids\": [\"21307348\", \"21276423\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological role of aldolase binding unclear\", \"Direct effectors linking Arf6 to Cdc42 not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated CYTH2 as an inflammatory effector via a direct MYD88–ARNO–ARF6 complex controlling endothelial barrier integrity, validating pharmacological inhibition (SecinH3) in vivo; and identified it as a host factor for Salmonella invasion.\",\n      \"evidence\": \"Co-IP/direct binding, dominant-negatives, permeability assays, in vivo arthritis model; RNAi screen and invasion assays with WRC recruitment\",\n      \"pmids\": [\"23143332\", \"22341462\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MYD88 binding activates ARF6 mechanistically not detailed\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the structural mechanism of V-ATPase a-subunit inhibition of GEF activity (a2N competing with ARF switch 2) and demonstrated druggable pockets on the Sec7 surface.\",\n      \"evidence\": \"In vitro GEF assays, NMR structure of a2N(1-17), docking, conservation across a-subunit isoforms; fragment-based design with X-ray Sec7–fragment complexes\",\n      \"pmids\": [\"23288846\", \"24112024\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular conditions selecting V-ATPase inhibition vs activation not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established physiological roles in platelet granule secretion (constitutive ARF6 suppression relieved by PKC), neurite vesicle transport via CCDC120, preadipocyte migration, and identified the RLIP76 N-terminus as a CYTH2 partner.\",\n      \"evidence\": \"Phospho-IP/MS and aggregometry in platelets; CCDC120 co-IP/siRNA rescue with live imaging; inhibitor panels with ARF6/ERK assays; RLIP76 domain-mapped co-IP with functional assays\",\n      \"pmids\": [\"24581425\", \"25326380\", \"25450674\", \"25450693\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PKC site in platelet context not pinpointed\", \"RLIP76 phospho-regulation of CYTH2 binding incompletely defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated an in vivo requirement for CYTH2 in Schwann cell myelination (conditional knockout reduces ARF6 activity and myelin) and defined RLIP76-linked R-Ras/integrin recycling through recycling endosomes.\",\n      \"evidence\": \"Schwann cell conditional knockout with EM myelin measurement and ARF6 assays; RLIP76 domain mutants, EHD1/Rab11 localization, GEF-dead E156K, integrin recycling assays\",\n      \"pmids\": [\"25824033\", \"26498519\", \"26378252\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream ARF6 effectors in myelination not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed CYTH2 acting through ARF1 (not solely ARF6) is required for podosome assembly by suppressing a RhoA/myosin-IIA axis.\",\n      \"evidence\": \"siRNA, pharmacological inhibition, ARF1-GTP pulldown, constitutively active ARF1, myosin-IIA inhibition rescue in multiple cell types\",\n      \"pmids\": [\"28007915\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Link between ARF1-GTP and RhoA suppression mechanistically open\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Structurally characterized direct CYTH2 binding to the EGFR juxtamembrane segment, embedding it in a regulated receptor-proximal modulatory network.\",\n      \"evidence\": \"NMR of the ARNO–EGFR JM interface and direct binding assays\",\n      \"pmids\": [\"31780432\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full cellular functional validation of the EGFR interaction\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Uncovered a GEF-activity-independent function: the IBD risk protein INAVA stably binds CYTH2 to drive junctional F-actin and to restrain TRAF6-dependent inflammatory ubiquitination.\",\n      \"evidence\": \"Co-IP/domain binding, F-actin assays, GEF-dead ARNO, TRAF6 ubiquitination assays in epithelial cells and macrophages\",\n      \"pmids\": [\"30355448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which ARNO binding modulates CUPID/TRAF6 not fully resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended CYTH2 to neuronal physiology and viral infection: it complexes with mGluR5 to drive spinal pain signaling, stabilizes CNKSR2 against degradation in hippocampal neurons, and is required for influenza endosomal trafficking.\",\n      \"evidence\": \"Conditional knockout mice with behavioral/Arf6/ERK assays; co-IP with shRNA and proteasome rescue; genome-wide CRISPR screen with knockout and SecinH3 in vivo\",\n      \"pmids\": [\"34390832\", \"34800437\", \"35354039\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CYTH2 binding prevents CNKSR2 degradation mechanistically open\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined Tyr381 phosphorylation (SH2B1 writer / PTP4A1 eraser) as a myelination control switch, linked the CYTH2/ARF1 axis to JNK–IRE1–XBP1 signaling in osteoclasts, and showed FE65 potentiates ARF6-driven neurite outgrowth by relieving ARNO autoinhibition.\",\n      \"evidence\": \"Y381F knockin and conditional knockdowns with phospho-antibody and ARF6 assays; siRNA/SecinH3 with RNA-seq and pathway assays in OVX osteoporosis model; FE65 co-IP and neurite outgrowth with dimerization mutants\",\n      \"pmids\": [\"35077201\", \"36252772\", \"36168805\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Tyr381 phosphorylation alters GEF behavior structurally not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed the V-ATPase V0a1 subunit as an upstream activator of the ARNO–Arf6–PLD1 pathway during regulated exocytosis in neuroendocrine cells.\",\n      \"evidence\": \"Co-IP, interaction disruption, PLD/phosphatidic acid/exocytosis-timing and Arf6 assays\",\n      \"pmids\": [\"37091866\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct activation mechanism by V0a1 versus a2N inhibition not reconciled\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Established that CYTH2 is essential for organismal viability and maintains Golgi volume and global protein secretion through an ARF-GEF-independent activity, separating its catalytic and structural roles.\",\n      \"evidence\": \"Full knockout mouse (perinatal lethality), organellar/quantitative proteomics, peanut agglutinin staining, ARF-GEF-independent re-expression rescue\",\n      \"pmids\": [\"41672711\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of the ARF-GEF-independent Golgi function unknown\", \"Cause of perinatal lethality not pinpointed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CYTH2 integrates its many competing recruiters and post-translational switches to select a specific ARF (ARF1 vs ARF6) and a specific downstream output in a given cellular context remains unresolved, as does the molecular basis of its ARF-GEF-independent Golgi/secretory function.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model for context-dependent ARF1/ARF6 selectivity\", \"ARF-GEF-independent mechanism uncharacterized\", \"Structural picture of full-length autoinhibited vs activated enzyme on membranes incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 3, 11, 13, 30]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 3, 30]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [5, 9, 8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [14, 15, 28, 53]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 5, 7, 23]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [12, 22, 44]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 12]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [55]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [12, 22, 23, 54]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [11, 20, 24, 34]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [43, 44, 55]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [34, 46]}\n    ],\n    \"complexes\": [\n      \"MYD88–ARNO–ARF6 complex\",\n      \"ARNO–Dock180/Elmo Rac signaling complex\",\n      \"ARNO–ARF6–FE65 complex\"\n    ],\n    \"partners\": [\n      \"ARF6\",\n      \"ARF1\",\n      \"IPCEF1\",\n      \"ARL4D\",\n      \"MYD88\",\n      \"GNAQ\",\n      \"RALBP1\",\n      \"INAVA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}