{"gene":"SNX27","run_date":"2026-06-10T07:46:37","timeline":{"discoveries":[{"year":2010,"finding":"SNX27 is required for efficient PDZ-directed recycling of the β2-adrenoreceptor (β2AR) from early endosomes to the plasma membrane. This recycling activity requires both PDZ domain-dependent recognition of the β2AR cytoplasmic tail and PX domain-dependent association with the endosome membrane.","method":"Endogenous expression knockdown, domain mutagenesis, subcellular fractionation, live-cell imaging","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean KD at endogenous levels with defined cellular phenotype, domain mutagenesis establishing two required functional domains, single lab with two orthogonal methods","pmids":["20733053"],"is_preprint":false},{"year":2011,"finding":"SNX27 serves as an essential adaptor protein linking β2ARs to the retromer tubule, enabling endosome-to-plasma membrane trafficking. SNX27 interacts with the retromer-associated WASH complex and mediates entry of β2ARs into Rab4-associated retromer tubules.","method":"shRNA knockdown, Co-IP, fluorescence microscopy, receptor recycling assays","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP and functional KD with defined phenotype, replicated across independent methods in a focused mechanistic study","pmids":["21602791"],"is_preprint":false},{"year":2011,"finding":"SNX27 is primarily targeted to the early endosome by interaction of its PX domain with PtdIns(3)P. SNX27 interacts with NMDA receptor 2C (NR2C) via its PDZ domain and the C-terminal PDZ-binding motif of NR2C, and its absence impairs NR2C endocytosis/endosomal sorting.","method":"Knockout mouse, subcellular fractionation, Co-IP, endocytosis assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO model combined with biochemical interaction mapping and functional endocytosis assay, single lab but multiple orthogonal methods","pmids":["21300787"],"is_preprint":false},{"year":2013,"finding":"SNX27 promotes recycling of over 100 cell-surface transmembrane proteins (including GLUT1, ATP7A, zinc/amino acid transporters, and signaling receptors) from endosomes to the plasma membrane by linking PDZ-dependent cargo recognition to the retromer complex. Direct interaction of the SNX27 PDZ domain with the retromer subunit VPS26 is necessary and sufficient to prevent lysosomal entry of SNX27 cargo.","method":"Quantitative proteomics of SNX27 interactome, quantitative surface proteomics of SNX27/retromer-depleted cells, domain mutant rescue experiments","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — quantitative proteomics combined with functional surface proteomics and genetic rescue experiments across large cargo set, single lab with multiple orthogonal methods","pmids":["23563491"],"is_preprint":false},{"year":2013,"finding":"SNX27 PDZ domain interacts with the C-terminal PDZ-binding motif of ZO-2. Upon tight junction disruption, ZO-2 transiently localizes to SNX27-positive early endosomes. SNX27 depletion reduces ZO-2 mobility at cell-cell contacts and increases junctional permeability to large solutes.","method":"Proteomic pulldown, Co-IP, live FRAP imaging, epithelial permeability assay, siRNA knockdown","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus FRAP and functional permeability assay in a single lab study","pmids":["23826934"],"is_preprint":false},{"year":2014,"finding":"Crystal structures and NMR experiments reveal that an exposed β-hairpin in the SNX27 PDZ domain engages a groove in the arrestin-like structure of VPS26A. VPS26A binding increases the affinity of the SNX27 PDZ domain for PDZ-binding motifs by an order of magnitude, demonstrating cooperativity in cargo selection.","method":"X-ray crystallography, NMR, biophysical binding assays (ITC/SPR), functional cell-based cargo sorting assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with NMR validation and quantitative binding measurements revealing cooperativity, multiple orthogonal methods in a single rigorous study","pmids":["25136126"],"is_preprint":false},{"year":2014,"finding":"Quantitative proteomics of the VPS35 retromer interactome confirmed functional heterogeneity in SNX27-retromer-mediated endosome-to-plasma membrane sorting; suppression of the retromer-associated WASH complex did not uniformly affect retromer/SNX27 cargo, indicating cargo-specific functions for retromer-interacting proteins.","method":"Quantitative proteomics (SILAC), siRNA knockdown, trafficking assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative proteomics plus functional siRNA knockdown experiments in a single lab","pmids":["25278552"],"is_preprint":false},{"year":2015,"finding":"SNX27 directly interacts with FAM21, a subunit of the WASH complex, via its PDZ domain. This interaction is required for precise localization of SNX27 at an endosomal subdomain and for efficient recycling of SNX27-retromer cargoes to the plasma membrane. FAM21 prevents cargo transport to the Golgi by controlling phosphatidylinositol 4-phosphate levels.","method":"Co-IP, siRNA knockdown, subcellular localization imaging, lipid measurement","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct interaction established by Co-IP with functional KD showing both localization and trafficking defects, plus lipid mechanistic arm; single lab but multiple orthogonal methods","pmids":["26956659"],"is_preprint":false},{"year":2015,"finding":"The SNX27 FERM domain contains a phosphoinositide-binding site preferring bi- and tri-phosphorylated phosphoinositides. Perturbing this site alters SNX27 distribution between endosomal recycling compartments and PtdIns(3,4,5)P3-enriched plasma membrane domains during immunological synapse formation in activated T-cells.","method":"Biophysical binding assays, mutagenesis, live-cell fluorescence imaging, phosphoinositide pulldown","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biophysical measurements combined with mutagenesis and functional live-cell imaging, multiple orthogonal methods in a single study","pmids":["25472716"],"is_preprint":false},{"year":2015,"finding":"VPS26A-SNX27 interaction mediates mGluR5 recycling in dorsal horn neurons. Spinal nerve ligation enhanced VPS26A-SNX27 coprecipitation and increased mGluR5 membrane abundance; focal knockdown of VPS26A or SNX27 attenuated mGluR5 membrane insertion and behavioral allodynia.","method":"Co-IP, siRNA knockdown in vivo, immunofluorescence, behavioral pain assay","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP combined with in vivo knockdown and behavioral/biochemical readouts, single lab","pmids":["26538661"],"is_preprint":false},{"year":2016,"finding":"Specific acidic amino acid sequences upstream of the PDZ-binding motif are required for high-affinity engagement of the SNX27 PDZ domain. A subset of SNX27 ligands (β2AR, NMDA receptor) use conserved phosphorylation sites that substitute for acidic residues to enhance SNX27 binding, suggesting a phosphorylation-regulated switch for PDZ interaction and protein transport.","method":"Crystal structure, NMR, ITC binding assays, phosphopeptide binding studies, mutagenesis, cell-based trafficking assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural, biophysical, and cell-based mechanistic validation with phospho-regulatory switch established by multiple orthogonal approaches in one study","pmids":["27595347"],"is_preprint":false},{"year":2016,"finding":"SNX27 interacts with SORLA via the SORLA cytosolic tail to form a ternary complex with APP. SNX27 enhances cell-surface SORLA and APP levels, and depletion of SNX27 or SORLA reduces APP endosome-to-cell surface recycling kinetics. SNX27 overexpression enhances non-amyloidogenic APP surface cleavage products in a SORLA-dependent manner.","method":"Co-IP, siRNA knockdown, surface biotinylation, recycling kinetics assay, APP cleavage product quantification","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing ternary complex combined with functional KD and recycling assay, single lab","pmids":["27466343"],"is_preprint":false},{"year":2016,"finding":"SNX27 binds parathyroid hormone receptor (PTHR) via a PDZ domain-PDZ-binding motif interaction at endosomes. Mass spectrometry identified SNX27 in isolated endosomes as a PTHR binding partner. Depletion of SNX27 or VPS35 or actin depolymerization decreased the rate of PTHR recycling. PTHR can also engage retromer directly through VPS26, forming a ternary PTHR/SNX27/retromer complex.","method":"Mass spectrometry, Co-IP, molecular dynamics, protein binding assays, siRNA knockdown, receptor recycling assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS identification with biochemical validation and functional recycling assay, multiple methods in single lab","pmids":["27008860"],"is_preprint":false},{"year":2016,"finding":"SNX27 deficiency in mice results in reductions in ependymal cells and cilia density and severe postnatal hydrocephalus. SNX27 knockout leads to Notch hyperactivation, and inhibition of Notch intracellular domain signaling with γ-secretase inhibitors reversed ependymal cell/cilia loss and ventricular dilation, indicating SNX27 promotes ependymal cell differentiation and ciliogenesis by suppressing γ-secretase-dependent Notch signaling.","method":"SNX27 knockout mouse, γ-secretase inhibitor rescue, immunohistochemistry, cilia density quantification","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with pharmacological rescue establishing pathway position, single lab","pmids":["27974614"],"is_preprint":false},{"year":2017,"finding":"PTEN physically interacts with SNX27, and this interaction (phosphatase-independent) blocks the association of SNX27 with VPS26, thereby preventing SNX27-retromer assembly and impairing GLUT1 recycling from endosomes to the plasma membrane.","method":"Co-IP, siRNA knockdown, glucose uptake assay, surface biotinylation, somatic mutant analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing interaction mechanism, functional KD with GLUT1 trafficking readout, single lab","pmids":["29117568"],"is_preprint":false},{"year":2017,"finding":"SNX27 limits TCR-stimulated DAG-based signals in T lymphocytes by recycling DGKζ (diacylglycerol kinase ζ) via a PDZ-domain interaction. SNX27 silencing enhanced AP-1 and NF-κB transcription, while DGKζ silencing did not increase transcription, suggesting DGKζ function is SNX27-dependent.","method":"siRNA silencing, transcription reporter assays, Co-IP, Snx27-/- mouse analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional KD and genetic KO with transcriptional readouts, single lab","pmids":["29180720"],"is_preprint":false},{"year":2018,"finding":"SNX27 directly interacts with the PDZ-binding motif of ASCT2 (glutamine transporter SLC1A5) via its PDZ domain. CRISPR-mediated SNX27 KO causes ASCT2 missorting to lysosomes, reducing surface ASCT2, glutamine uptake, and mTORC1 activation, while enhancing autophagy.","method":"CRISPR KO, subcellular fractionation, surface biotinylation, glutamine uptake assay, mTORC1 signaling assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR KO with multiple functional readouts (trafficking, glutamine uptake, mTORC1, autophagy), direct interaction established biochemically; multiple orthogonal methods","pmids":["29563155"],"is_preprint":false},{"year":2018,"finding":"Cholera toxin causes PKA-dependent phosphorylation of an amino acid in the SNX27 PDZ domain, inhibiting SNX27-mediated trafficking of NHE3 from early endosomes to the plasma membrane. Mutagenesis (Ser to Asp) phenocopied loss of SNX27 function. Cholera toxin also destabilizes retromer. These effects can be partially rescued by pharmacological chaperones that enhance retromer stability.","method":"Phospho-mutagenesis, siRNA knockdown, surface biotinylation, NHE3 activity assay, pharmacological rescue","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — phospho-mutagenesis establishing PTM mechanism, functional trafficking assay, single lab","pmids":["30030371"],"is_preprint":false},{"year":2019,"finding":"OTULIN's C-terminal PDZ-binding motif (PDZbm) binds the cargo-binding site in the SNX27 PDZ domain. A second interface between the OTULIN OTU domain and SNX27 PDZ domain contributes to high-affinity interaction (revealed by crystal structure). OTULIN does not affect SNX27's catalytic function but antagonizes SNX27-dependent cargo loading, VPS26A binding, and endosome-to-plasma membrane trafficking.","method":"X-ray crystallography, Co-IP, mass spectrometry, siRNA knockdown, surface trafficking assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with biochemical and functional validation of a non-catalytic regulatory interaction, multiple orthogonal methods","pmids":["31541095"],"is_preprint":false},{"year":2019,"finding":"SNX27-mediated recycling of neuroligin-2 requires direct interaction between the SNX27 PDZ domain and the PDZ-binding motif in neuroligin-2. SNX27 knockdown reduces surface neuroligin-2, decreasing inhibitory synapse clustering and signaling strength; overexpression has the opposite effect.","method":"Co-IP, siRNA knockdown, live-cell imaging, electrophysiology, immunofluorescence","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing direct interaction, functional KD with synaptic and electrophysiological readouts, single lab","pmids":["31775031"],"is_preprint":false},{"year":2020,"finding":"SNX27 and retromer directly interact with MT1-MMP (ITC-based binding studies) and selectively recycle MT1-MMP (but not MT2-MMP) to invadopodia in metastatic breast cancer cells. SNX27 depletion reduces matrix degradation activity.","method":"ITC binding assay, siRNA knockdown, matrix degradation assay, Co-IP, colocalization imaging","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — ITC establishing direct binding, functional KD with specific cargo selectivity demonstrated, single lab","pmids":["31820782"],"is_preprint":false},{"year":2020,"finding":"SNX27 regulates DRA (SLC26A3) activity and recycling via a direct PDZ domain-PDZ-binding motif interaction. SNX27 knockdown reduced DRA activity by 50% without decreasing DRA surface expression, indicating SNX27 directs DRA to active lipid raft domains. SNX27 and DRA colocalize in Rab5-positive early endosomes at the apical pole of intestinal cells.","method":"siRNA knockdown, PDZ domain interaction assay, DRA activity assay (chloride flux), superresolution microscopy, subcellular colocalization","journal":"American journal of physiology. Gastrointestinal and liver physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction established biochemically with functional KD and activity assay, single lab","pmids":["32116023"],"is_preprint":false},{"year":2021,"finding":"MAPK11/14 (p38 kinases), activated by multiple extracellular stressors (starvation, LPS, IL-6, EGF), directly phosphorylate SNX27 at serine 51. This phosphorylation alters the conformation of the SNX27 cargo-binding pocket and decreases SNX27-cargo interactions, thereby inhibiting endocytic recycling and promoting lysosomal degradation of cargo.","method":"In vitro kinase assay, phospho-site mutagenesis, Co-IP, cargo recycling assay, structural/conformational analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay establishing direct phosphorylation at defined site, mutagenesis confirming mechanistic consequence, functional trafficking readout; multiple orthogonal methods in single study","pmids":["33605979"],"is_preprint":false},{"year":2021,"finding":"SNX27 interacts with VARP (VPS9-ankyrin repeat protein/ANKRD27) as a new retromer-interacting protein. VARP depletion causes differential trafficking defects of retromer cargo, suggesting cargo-specific roles within the SNX27-retromer pathway.","method":"Quantitative proteomics, Co-IP, siRNA knockdown, trafficking assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative proteomics followed by Co-IP and KD with trafficking phenotype, single lab","pmids":["25278552"],"is_preprint":false},{"year":2021,"finding":"SNX27 inhibits TNFα-induced NF-κB signaling activation by facilitating OTULIN localization to the TNF receptor complex at the membrane. SNX27-retromer translocation is required for this membrane targeting; chemical inhibition of SNX27-retromer (by cholera toxin) blocks OTULIN membrane localization.","method":"Co-IP, siRNA knockdown, NF-κB reporter assay, fractionation, cholera toxin inhibition","journal":"Cell & bioscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional reporter and pharmacological inhibition confirming mechanism, single lab","pmids":["34315543"],"is_preprint":false},{"year":2021,"finding":"AQP4 is a cargo of the SNX27-retromer complex. Kidins220 deficiency causes downregulation of SNX27-retromer, resulting in AQP4 lysosomal degradation. SNX27 silencing decreases AQP4 levels; SNX27 overexpression restores AQP4 content in Kidins220-deficient astrocytes.","method":"siRNA knockdown, SNX27 overexpression, lysosomal degradation assay, Co-IP, immunofluorescence, conditional KO mouse","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with gain/loss of function establishing AQP4 as SNX27-retromer cargo, single lab","pmids":["34002021"],"is_preprint":false},{"year":2021,"finding":"The SNX27 FERM domain directly binds the flexible SNX1/SNX2 N-terminus through acidic-DxF motifs. Forty residues containing two DxF motifs in the SNX1 N-terminus are sufficient for SNX27 binding (KD ~10 µM by ITC). Mutation of either DxF sequence abrogates binding.","method":"Pulldown with purified proteins, ITC calorimetry, mutagenesis, sequence alignment","journal":"Advances in biological regulation","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified proteins, ITC quantification, and mutagenesis confirming binding determinants in a single study","pmids":["34866035"],"is_preprint":false},{"year":2022,"finding":"SNX27 directly interacts with ACE2 via the ACE2 PDZ-binding motif and the SNX27 PDZ domain (complex structure determined). SNX27-retromer prevents ACE2/SARS-CoV-2 virus complex from entering lysosomes/late endosomes, thereby decreasing viral endocytic entry in cells where the endocytic pathway dominates.","method":"Crystal structure, functional viral infection assay, siRNA knockdown, surface trafficking assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of PDZ-PBM complex combined with functional viral infection assay and KD validation, multiple orthogonal methods","pmids":["35022217"],"is_preprint":false},{"year":2022,"finding":"The SNX27 FERM domain directly binds acidic-Asp-Leu-Phe (aDLF) motifs in the SNX1/SNX2 subunits of ESCPE-1, establishing a 'handover' model where SNX27-Retromer-captured cargo proteins are transferred into ESCPE-1 transport carriers for endosome-to-plasma membrane recycling. This assembly of SNX27:Retromer:ESCPE-1 evolved in a stepwise manner during early metazoan evolution.","method":"Biochemical reconstitution, structural analysis, mutagenesis, cellular trafficking assays, evolutionary analysis","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — biochemical reconstitution combined with structural analysis, mutagenesis, and cellular validation in a single comprehensive study","pmids":["35417450"],"is_preprint":false},{"year":2022,"finding":"SNX27 interacts with TANC2 via its PDZ domain; in the absence of HPV-18 E6, SNX27 directs TANC2 toward lysosomal degradation. HPV-18 E6 inhibits SNX27-TANC2 interaction in a PBM-dependent manner, increasing TANC2 levels and enhancing cell proliferation.","method":"Co-immunoprecipitation, mass spectrometry, siRNA knockdown, cell proliferation assay","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus KD with functional proliferation readout, single lab","pmids":["36326272"],"is_preprint":false},{"year":2023,"finding":"SNX27 regulates apical targeting and turnover of membrane mucin MUC17 in enterocytes. SNX27 controls MUC17 turnover at the brush border in concert with the motor protein MYO1B.","method":"siRNA knockdown, surface biotinylation, pulse-chase turnover assay, immunofluorescence","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional KD with defined cargo trafficking phenotype, single lab","pmids":["39661054"],"is_preprint":false},{"year":2024,"finding":"Crystal structures reveal that FAM21 (WASH complex subunit) binds the SNX27 FERM domain using aDLF motifs similar to those found in SNX1/SNX2. Overlapping FAM21 repeats and a Pro-Leu-containing motif bind three distinct sites on Retromer (VPS35 and VPS29). Mutation of the major VPS35-binding site partially reduces endosomal WASH association without fully preventing cargo recycling.","method":"X-ray crystallography, AlphaFold modeling, biochemical mutagenesis, Co-IP, cellular trafficking assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures combined with biochemical mutagenesis and functional cellular validation, multiple orthogonal methods establishing molecular basis of WASH-SNX27-Retromer coupling","pmids":["39116126"],"is_preprint":false},{"year":2025,"finding":"VARP directly interacts with SNX27 (new interaction identified by biochemical/biophysical approaches and AlphaFold modeling). VARP co-immunoprecipitates all coat components (SNX27, ESCPE-1, Retromer) in cells and is required to reconstitute a proposed endosomal 'supercomplex' in vitro. SNX27 alone and with Retromer remodels PI(3)P-containing membranes carrying PDZbm cargo into tubules in a reconstituted system.","method":"Biochemical reconstitution with purified proteins, liposome tubulation assay, AlphaFold modeling, Co-IP, ITC/biophysical binding measurements","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Strong — full biochemical reconstitution with purified proteins on physiological lipid membranes, combined with structural modeling and cellular Co-IP validation; multiple orthogonal methods","pmids":["39937906"],"is_preprint":false},{"year":2025,"finding":"PI(3)P synthesis during chemical LTP induction drives coordinate recruitment of SNX27-Retromer to endosomes and synaptic sites in hippocampal neurons. Both SNX27-Retromer and SNX17-Retriever pathways are necessary for cLTP-dependent dendritic spine structural enlargement, acting in parallel by recycling distinct cargo sets. Preventing PI(3)P synthesis blocks synaptic recruitment of SNX27, decreases cargo recycling, and blocks LTP.","method":"Live-cell imaging in primary hippocampal neurons, PI(3)P biosensor, siRNA/shRNA knockdown, dendritic spine morphometry, LTP recording in hippocampal slices","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (imaging, electrophysiology, genetic KD) with functional LTP readout in neurons and slices; replicates across multiple levels of analysis","pmids":["40920104"],"is_preprint":false},{"year":2004,"finding":"SNX27 (identified as a new PDZ-containing protein) interacts specifically with the 5-HT4(a) receptor splice variant via a PDZ-domain interaction. SNX27a redirects part of the 5-HT4(a)R to early endosomes.","method":"Peptide-affinity chromatography, 2D electrophoresis, mass spectrometry, subcellular localization imaging","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — proteomic identification confirmed by subcellular localization imaging, single lab; early characterization study","pmids":["15466885"],"is_preprint":false},{"year":2007,"finding":"Endosomal SNX27 polarizes to the immunological synapse (IS) in a distinct compartment adjacent to cytotoxic granules during NK cell tumor engagement, and polarizes to the apical membrane during NK cell migration.","method":"In vitro NK-tumor conjugation assay, fluorescence microscopy","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single localization experiment, no functional consequence established, single lab","pmids":["17644068"],"is_preprint":false},{"year":2016,"finding":"SNX27 interacts with GPR17 via a PDZ-binding motif at the GPR17 C-terminus and mediates GPR17 plasma membrane recycling in oligodendrocytes. SNX27 knockdown reduces GPR17 plasma membrane recycling and accelerates oligodendrocyte terminal maturation.","method":"Co-IP, siRNA knockdown, surface trafficking assay, cell differentiation assay","journal":"Glia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional KD establishing cargo recycling and differentiation consequences, single lab","pmids":["27270750"],"is_preprint":false},{"year":2019,"finding":"HTLV-1 Tax-1 interacts with SNX27 via its PDZ-binding motif and the SNX27 PDZ domain. Tax-1 overexpression causes reduction of GLUT1 on the plasma membrane. SNX27 knockdown increases virion release and decreases HTLV-1 infectivity, revealing a mechanism by which HTLV-1 regulates a receptor post-infection.","method":"Mass spectrometry, Co-IP, flow cytometry (surface GLUT1), siRNA knockdown, viral infectivity assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS identification with Co-IP validation and functional GLUT1 and infectivity assays, single lab","pmids":["30897179"],"is_preprint":false},{"year":2021,"finding":"SARS-CoV-2 spike (S) protein binds to the PDZ domain of SNX27 through an 'MTSC' motif (not a canonical PDZbm). Abrogation of either the SNX27 PDZ domain or the S protein MTSC motif decreases surface S protein expression and viral production.","method":"Co-IP, mutagenesis, surface expression assay, viral production assay","journal":"MedComm","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with mutagenesis validation and functional viral output assay, single lab","pmids":["34909756"],"is_preprint":false},{"year":2026,"finding":"VPS26A-retromer, together with SNX27, mediates unconventional protein secretion (Golgi-bypass) of transmembrane proteins including trafficking-deficient ΔF508-CFTR and SARS-CoV-2 spike protein under cellular stress. SNX27 recruits ΔF508-CFTR to the VPS26A-VPS35-VPS29 retromer complex for transport to the cell surface under UPS-inducing conditions.","method":"CRISPR KO screen, molecular interaction analysis, surface expression assay, viral particle assay","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — targeted CRISPR screen identifying VPS26A, followed by molecular interaction and surface trafficking analyses; single lab","pmids":["41942457"],"is_preprint":false},{"year":2024,"finding":"SNX27 interacts with EMILIN2 via its PDZ domain; HPV-18 E6 enhances (rather than disrupts) this SNX27-EMILIN2 interaction in a PBM-dependent manner, blocking EMILIN2 secretion and its inhibition of WNT1 signaling.","method":"Co-IP, mass spectrometry proteomics, siRNA knockdown, WNT signaling assay","journal":"Journal of virology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP identification with functional signaling assay, single lab, mechanism of enhanced interaction not fully characterized","pmids":["38874360"],"is_preprint":false},{"year":2022,"finding":"Tex264 interacts with SNX27 (confirmed by Co-IP and immunofluorescence). siRNA-mediated TEX264 knockdown inhibits cell migration potentially through reduced SNX27-mediated Itgα5 receptor membrane recycling.","method":"Co-IP, immunofluorescence, siRNA knockdown, cell migration assay","journal":"BioMed research international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP establishing interaction, functional KD with migration phenotype but limited mechanistic detail, single lab","pmids":["35837377"],"is_preprint":false}],"current_model":"SNX27 is an endosomal adaptor protein that uses its PX domain to bind PtdIns(3)P and localize to early endosomes, its PDZ domain to capture transmembrane cargo bearing PDZ-binding motifs (with affinity enhanced by phosphorylation of upstream acidic residues), and its FERM domain to interact with the VPS26 subunit of the retromer heterotrimer, the aDLF motifs of SNX1/SNX2 (ESCPE-1), and FAM21 (WASH complex); together these interactions form a hierarchical endosomal coat (SNX27–Retromer–ESCPE-1–WASH supercomplex, stabilized by VARP) that captures >100 cargo proteins and transfers them into tubular transport carriers for recycling to the plasma membrane, a process regulated by direct phosphorylation of SNX27 at Ser51 by stress-activated MAPK11/14, by competitive binding of OTULIN or PTEN to the SNX27 PDZ and FERM domains, and by dynamic PI(3)P synthesis that coordinates SNX27 recruitment to synapses during long-term potentiation."},"narrative":{"mechanistic_narrative":"SNX27 is an endosomal sorting nexin that functions as a cargo-selective adaptor coupling PDZ-binding-motif (PBM)-containing transmembrane proteins to the retromer complex for endosome-to-plasma-membrane recycling, preventing their default lysosomal degradation [PMID:20733053, PMID:23563491]. Its modular architecture integrates three activities: a PX domain that binds PtdIns(3)P to target early endosomes [PMID:21300787], a PDZ domain that recognizes C-terminal PBMs on cargo, and a FERM domain that engages the retromer and downstream coat machinery [PMID:34866035, PMID:35417450]. The PDZ domain directly binds the retromer subunit VPS26A through an exposed β-hairpin, and this interaction reciprocally enhances PDZ affinity for cargo PBMs by an order of magnitude, embedding cooperativity into cargo selection [PMID:25136126]; engagement is further tuned by acidic residues upstream of the PBM whose function can be substituted by regulated phosphorylation, creating a phospho-switch for cargo capture [PMID:27595347]. Through these interactions SNX27 recycles over 100 surface proteins, including nutrient and ion transporters (GLUT1, ASCT2/SLC1A5, DRA/SLC26A3), signaling receptors (β2-adrenoreceptor, NMDA receptor, GPR17), and adhesion/junction proteins [PMID:23563491, PMID:29563155, PMID:32116023]. The SNX27 FERM domain organizes a hierarchical endosomal coat by binding aDLF/DxF motifs in the SNX1/SNX2 subunits of ESCPE-1 — handing cargo into tubular transport carriers — and analogous aDLF motifs in FAM21 of the WASH complex, with VARP bridging the SNX27–Retromer–ESCPE-1 assembly into a reconstitutable supercomplex that remodels PI(3)P membranes into cargo-laden tubules [PMID:34866035, PMID:35417450, PMID:39116126, PMID:39937906]. Recycling output is controlled by post-translational and competitive regulation: stress-activated MAPK11/14 (p38) directly phosphorylate SNX27 at Ser51 to reshape the cargo-binding pocket and redirect cargo to lysosomes [PMID:33605979], while PTEN and OTULIN competitively bind the SNX27 PDZ/FERM surfaces to block VPS26A association and cargo loading [PMID:29117568, PMID:31541095]. Beyond housekeeping recycling, SNX27 shapes physiology in neurons, where PI(3)P-driven recruitment supports synaptic cargo recycling during LTP [PMID:40920104], and is exploited by viruses including SARS-CoV-2, whose spike and ACE2 engage the SNX27 PDZ domain to influence endocytic entry and surface expression [PMID:35022217, PMID:34909756].","teleology":[{"year":2004,"claim":"Established SNX27 as a PDZ-domain protein capable of binding a specific GPCR splice variant and directing it to endosomes, the first hint of an endosomal sorting role.","evidence":"Peptide-affinity chromatography, mass spectrometry and localization imaging of the 5-HT4(a) receptor","pmids":["15466885"],"confidence":"Medium","gaps":["No retromer link or recycling function defined","Mechanism of endosomal targeting unaddressed"]},{"year":2011,"claim":"Defined the two-domain logic of SNX27 sorting — PX-domain PtdIns(3)P binding for endosome targeting and PDZ-domain recognition of cargo PBMs — and showed it is required for recycling of β2AR and NMDA receptor cargo to the surface.","evidence":"Knockdown/knockout, subcellular fractionation, domain mutagenesis and endocytosis/recycling assays for β2AR and NR2C","pmids":["20733053","21300787","21602791"],"confidence":"High","gaps":["Molecular basis of retromer coupling not yet resolved","Cargo repertoire unknown"]},{"year":2013,"claim":"Generalized SNX27 from a few-receptor adaptor to a master recycling hub for >100 cargo and showed that direct PDZ–VPS26 binding is necessary and sufficient to divert cargo away from lysosomes.","evidence":"Quantitative interactome and surface proteomics with domain-mutant rescue in SNX27/retromer-depleted cells","pmids":["23563491"],"confidence":"High","gaps":["Structural basis of PDZ–VPS26 cooperativity not yet defined","How tubular carriers form downstream unresolved"]},{"year":2014,"claim":"Provided the structural mechanism by which retromer enhances cargo capture: VPS26A binds an exposed PDZ β-hairpin and allosterically increases PDZ affinity for cargo PBMs, establishing cooperative cargo selection.","evidence":"X-ray crystallography, NMR, ITC/SPR and cell-based sorting assays of the SNX27 PDZ–VPS26A complex","pmids":["25136126"],"confidence":"High","gaps":["Did not address FERM-domain partner interactions","Regulation of the allosteric switch not examined"]},{"year":2016,"claim":"Identified an acidic/phosphorylation code upstream of the PBM that controls high-affinity PDZ engagement, defining a phospho-regulated switch for cargo selection.","evidence":"Crystallography, NMR, ITC and phosphopeptide binding with cell-based trafficking assays","pmids":["27595347"],"confidence":"High","gaps":["Kinases generating the relevant phosphorylations on cargo not all identified","In vivo prevalence of the switch unquantified"]},{"year":2016,"claim":"Linked SNX27 to actin-based endosomal sorting machinery by showing direct PDZ-domain binding to FAM21 of the WASH complex controls SNX27 subdomain localization and PI4P levels to prevent Golgi mis-sorting.","evidence":"Co-IP, siRNA knockdown, localization imaging and lipid measurement","pmids":["26956659"],"confidence":"High","gaps":["Structural basis of FAM21 binding not resolved at this stage","PDZ vs FERM contribution to FAM21 binding not disentangled"]},{"year":2018,"claim":"Demonstrated that SNX27 loss redirects nutrient transporter cargo to lysosomes with downstream metabolic consequences, connecting recycling to mTORC1 signaling and autophagy.","evidence":"CRISPR KO with surface biotinylation, glutamine uptake, mTORC1 and autophagy readouts for ASCT2/SLC1A5","pmids":["29563155"],"confidence":"High","gaps":["Whether other transporters share this metabolic coupling not established","Tissue-level metabolic phenotype not addressed"]},{"year":2018,"claim":"Established post-translational and competitive regulation of SNX27: PKA-driven PDZ phosphorylation (cholera toxin) and phosphatase-independent PTEN binding both block VPS26 association and cargo recycling.","evidence":"Phospho-mutagenesis, Co-IP, surface biotinylation and trafficking/uptake assays (NHE3, GLUT1)","pmids":["30030371","29117568"],"confidence":"Medium","gaps":["Physiological signals controlling PTEN–SNX27 competition unclear","Phospho-site identity in cholera-toxin model not crystallographically resolved"]},{"year":2019,"claim":"Revealed dual-mode competitive inhibition by OTULIN, which uses both its PBM and a second OTU–PDZ interface to occupy the cargo-binding site and antagonize cargo loading without affecting catalysis.","evidence":"X-ray crystallography, Co-IP, mass spectrometry and surface trafficking assays","pmids":["31541095"],"confidence":"High","gaps":["Cellular trigger that shifts OTULIN between competitor and cargo not defined here"]},{"year":2021,"claim":"Identified the master stress switch on SNX27 itself: p38 MAPK (MAPK11/14) directly phosphorylates Ser51 to reshape the cargo-binding pocket, globally suppressing recycling and promoting lysosomal degradation under stress.","evidence":"In vitro kinase assay, phospho-site mutagenesis, Co-IP and cargo recycling/conformational analysis","pmids":["33605979"],"confidence":"High","gaps":["Which cargo subsets are most sensitive to Ser51 phosphorylation not resolved","Phosphatase reversing Ser51 unidentified"]},{"year":2021,"claim":"Expanded the coat to include VARP as a retromer-interacting partner with cargo-specific roles, foreshadowing a higher-order assembly.","evidence":"Quantitative proteomics, Co-IP and siRNA knockdown with trafficking assays","pmids":["25278552"],"confidence":"Medium","gaps":["Direct SNX27–VARP contact not yet defined at this stage"]},{"year":2022,"claim":"Resolved the FERM-domain handover mechanism: SNX27 directly binds aDLF/DxF motifs in SNX1/SNX2 of ESCPE-1, transferring captured cargo into tubular carriers, an assembly tracing to early metazoan evolution.","evidence":"Biochemical reconstitution, structural analysis, mutagenesis, ITC and cellular trafficking with evolutionary analysis","pmids":["35417450","34866035"],"confidence":"High","gaps":["Stoichiometry of the cargo handover in carriers not fully defined"]},{"year":2024,"claim":"Showed FAM21 uses aDLF motifs analogous to ESCPE-1 to bind the SNX27 FERM domain and contacts Retromer at three sites, molecularly unifying WASH–SNX27–Retromer coupling.","evidence":"Crystallography, AlphaFold modeling, mutagenesis, Co-IP and cellular trafficking","pmids":["39116126"],"confidence":"High","gaps":["Why VPS35-site mutation only partially reduces WASH association unresolved"]},{"year":2025,"claim":"Reconstituted the full endosomal coat in vitro, demonstrating VARP directly binds SNX27 and is required to assemble the SNX27–Retromer–ESCPE-1 supercomplex, with SNX27/Retromer alone remodeling PI(3)P membranes carrying PBM cargo into tubules.","evidence":"Reconstitution with purified proteins, liposome tubulation, AlphaFold modeling, Co-IP and ITC","pmids":["39937906"],"confidence":"High","gaps":["Native regulation and disassembly of the supercomplex in cells not addressed","Cryo-EM structure of the assembled coat absent"]},{"year":2025,"claim":"Placed SNX27 recycling in neuronal plasticity, showing PI(3)P synthesis during LTP recruits SNX27-Retromer to synapses to drive cargo recycling and spine enlargement in parallel with SNX17-Retriever.","evidence":"Live imaging with PI(3)P biosensor, knockdown, spine morphometry and LTP recordings in hippocampal neurons/slices","pmids":["40920104"],"confidence":"High","gaps":["Identity of the LTP-relevant SNX27 cargo set not fully enumerated","PI 3-kinase driving synaptic PI(3)P synthesis not pinned down"]},{"year":null,"claim":"How the multiple regulatory inputs (Ser51 phosphorylation, PTEN and OTULIN competition, cargo-PBM phosphorylation, PI(3)P dynamics) are integrated in real time to set cargo-specific recycling versus degradation outcomes remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model coupling stress kinase signaling to coat assembly state","In vivo phenotypic dissection of individual regulatory arms incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,3,5]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,8]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[3,16,21]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0,2,21]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,8]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,3,28]},{"term_id":"R-HSA-9609507","term_label":"Protein 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PROTEIN 50; ANKRD50","url":"https://www.omim.org/entry/619856"},{"mim_id":"619839","title":"SORTING NEXIN 31; SNX31","url":"https://www.omim.org/entry/619839"},{"mim_id":"611541","title":"SORTING NEXIN 27; SNX27","url":"https://www.omim.org/entry/611541"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SNX27"},"hgnc":{"alias_symbol":["MY014","KIAA0488","MGC20471"],"prev_symbol":[]},"alphafold":{"accession":"Q96L92","domains":[{"cath_id":"2.30.42.10","chopping":"40-141","consensus_level":"high","plddt":86.4007,"start":40,"end":141},{"cath_id":"3.30.1520.10","chopping":"164-261","consensus_level":"high","plddt":90.0323,"start":164,"end":261},{"cath_id":"3.10.20.90","chopping":"273-418","consensus_level":"medium","plddt":92.0864,"start":273,"end":418},{"cath_id":"2.30.29.30","chopping":"425-522","consensus_level":"high","plddt":95.4026,"start":425,"end":522}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96L92","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96L92-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96L92-F1-predicted_aligned_error_v6.png","plddt_mean":83.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SNX27","jax_strain_url":"https://www.jax.org/strain/search?query=SNX27"},"sequence":{"accession":"Q96L92","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96L92.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96L92/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96L92"}},"corpus_meta":[{"pmid":"23563491","id":"PMC_23563491","title":"A 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Gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/39128090","citation_count":0,"is_preprint":false},{"pmid":"41942457","id":"PMC_41942457","title":"VPS26A retromer complex and SNX27 mediate stress-induced Golgi bypass of membrane proteins.","date":"2026","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/41942457","citation_count":0,"is_preprint":false},{"pmid":"41609011","id":"PMC_41609011","title":"Novel Variants Identified in Families With SNX27 -Related Neurodevelopmental Disorder, Aiding in Characterizing Its Genotypic and Phenotypic Spectrum.","date":"2026","source":"American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41609011","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.05.635995","title":"Loss of intestinal endosome associated protein sorting nexin 27 disrupts epithelial barrier and promotes inflammation","date":"2025-02-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.05.635995","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.10.675364","title":"Differential Regulation of NHE3 Expression in Type 1 and Type 2 Diabetic Intestine: Impaired Endosomal Regulation of NHE3 Expression in Type 1 Diabetes","date":"2025-09-16","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.10.675364","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.24.614704","title":"Endo-IP and Lyso-IP Toolkit for Endolysosomal Profiling of Human Induced Neurons","date":"2024-09-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.24.614704","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":30665,"output_tokens":9829,"usd":0.119715,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":20460,"output_tokens":5107,"usd":0.114988,"stage2_stop_reason":"end_turn"},"total_usd":0.234703,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"SNX27 is required for efficient PDZ-directed recycling of the β2-adrenoreceptor (β2AR) from early endosomes to the plasma membrane. This recycling activity requires both PDZ domain-dependent recognition of the β2AR cytoplasmic tail and PX domain-dependent association with the endosome membrane.\",\n      \"method\": \"Endogenous expression knockdown, domain mutagenesis, subcellular fractionation, live-cell imaging\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD at endogenous levels with defined cellular phenotype, domain mutagenesis establishing two required functional domains, single lab with two orthogonal methods\",\n      \"pmids\": [\"20733053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SNX27 serves as an essential adaptor protein linking β2ARs to the retromer tubule, enabling endosome-to-plasma membrane trafficking. SNX27 interacts with the retromer-associated WASH complex and mediates entry of β2ARs into Rab4-associated retromer tubules.\",\n      \"method\": \"shRNA knockdown, Co-IP, fluorescence microscopy, receptor recycling assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP and functional KD with defined phenotype, replicated across independent methods in a focused mechanistic study\",\n      \"pmids\": [\"21602791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SNX27 is primarily targeted to the early endosome by interaction of its PX domain with PtdIns(3)P. SNX27 interacts with NMDA receptor 2C (NR2C) via its PDZ domain and the C-terminal PDZ-binding motif of NR2C, and its absence impairs NR2C endocytosis/endosomal sorting.\",\n      \"method\": \"Knockout mouse, subcellular fractionation, Co-IP, endocytosis assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO model combined with biochemical interaction mapping and functional endocytosis assay, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"21300787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SNX27 promotes recycling of over 100 cell-surface transmembrane proteins (including GLUT1, ATP7A, zinc/amino acid transporters, and signaling receptors) from endosomes to the plasma membrane by linking PDZ-dependent cargo recognition to the retromer complex. Direct interaction of the SNX27 PDZ domain with the retromer subunit VPS26 is necessary and sufficient to prevent lysosomal entry of SNX27 cargo.\",\n      \"method\": \"Quantitative proteomics of SNX27 interactome, quantitative surface proteomics of SNX27/retromer-depleted cells, domain mutant rescue experiments\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — quantitative proteomics combined with functional surface proteomics and genetic rescue experiments across large cargo set, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"23563491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SNX27 PDZ domain interacts with the C-terminal PDZ-binding motif of ZO-2. Upon tight junction disruption, ZO-2 transiently localizes to SNX27-positive early endosomes. SNX27 depletion reduces ZO-2 mobility at cell-cell contacts and increases junctional permeability to large solutes.\",\n      \"method\": \"Proteomic pulldown, Co-IP, live FRAP imaging, epithelial permeability assay, siRNA knockdown\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus FRAP and functional permeability assay in a single lab study\",\n      \"pmids\": [\"23826934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structures and NMR experiments reveal that an exposed β-hairpin in the SNX27 PDZ domain engages a groove in the arrestin-like structure of VPS26A. VPS26A binding increases the affinity of the SNX27 PDZ domain for PDZ-binding motifs by an order of magnitude, demonstrating cooperativity in cargo selection.\",\n      \"method\": \"X-ray crystallography, NMR, biophysical binding assays (ITC/SPR), functional cell-based cargo sorting assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with NMR validation and quantitative binding measurements revealing cooperativity, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"25136126\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Quantitative proteomics of the VPS35 retromer interactome confirmed functional heterogeneity in SNX27-retromer-mediated endosome-to-plasma membrane sorting; suppression of the retromer-associated WASH complex did not uniformly affect retromer/SNX27 cargo, indicating cargo-specific functions for retromer-interacting proteins.\",\n      \"method\": \"Quantitative proteomics (SILAC), siRNA knockdown, trafficking assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative proteomics plus functional siRNA knockdown experiments in a single lab\",\n      \"pmids\": [\"25278552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SNX27 directly interacts with FAM21, a subunit of the WASH complex, via its PDZ domain. This interaction is required for precise localization of SNX27 at an endosomal subdomain and for efficient recycling of SNX27-retromer cargoes to the plasma membrane. FAM21 prevents cargo transport to the Golgi by controlling phosphatidylinositol 4-phosphate levels.\",\n      \"method\": \"Co-IP, siRNA knockdown, subcellular localization imaging, lipid measurement\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction established by Co-IP with functional KD showing both localization and trafficking defects, plus lipid mechanistic arm; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"26956659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The SNX27 FERM domain contains a phosphoinositide-binding site preferring bi- and tri-phosphorylated phosphoinositides. Perturbing this site alters SNX27 distribution between endosomal recycling compartments and PtdIns(3,4,5)P3-enriched plasma membrane domains during immunological synapse formation in activated T-cells.\",\n      \"method\": \"Biophysical binding assays, mutagenesis, live-cell fluorescence imaging, phosphoinositide pulldown\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biophysical measurements combined with mutagenesis and functional live-cell imaging, multiple orthogonal methods in a single study\",\n      \"pmids\": [\"25472716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"VPS26A-SNX27 interaction mediates mGluR5 recycling in dorsal horn neurons. Spinal nerve ligation enhanced VPS26A-SNX27 coprecipitation and increased mGluR5 membrane abundance; focal knockdown of VPS26A or SNX27 attenuated mGluR5 membrane insertion and behavioral allodynia.\",\n      \"method\": \"Co-IP, siRNA knockdown in vivo, immunofluorescence, behavioral pain assay\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP combined with in vivo knockdown and behavioral/biochemical readouts, single lab\",\n      \"pmids\": [\"26538661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Specific acidic amino acid sequences upstream of the PDZ-binding motif are required for high-affinity engagement of the SNX27 PDZ domain. A subset of SNX27 ligands (β2AR, NMDA receptor) use conserved phosphorylation sites that substitute for acidic residues to enhance SNX27 binding, suggesting a phosphorylation-regulated switch for PDZ interaction and protein transport.\",\n      \"method\": \"Crystal structure, NMR, ITC binding assays, phosphopeptide binding studies, mutagenesis, cell-based trafficking assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural, biophysical, and cell-based mechanistic validation with phospho-regulatory switch established by multiple orthogonal approaches in one study\",\n      \"pmids\": [\"27595347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SNX27 interacts with SORLA via the SORLA cytosolic tail to form a ternary complex with APP. SNX27 enhances cell-surface SORLA and APP levels, and depletion of SNX27 or SORLA reduces APP endosome-to-cell surface recycling kinetics. SNX27 overexpression enhances non-amyloidogenic APP surface cleavage products in a SORLA-dependent manner.\",\n      \"method\": \"Co-IP, siRNA knockdown, surface biotinylation, recycling kinetics assay, APP cleavage product quantification\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing ternary complex combined with functional KD and recycling assay, single lab\",\n      \"pmids\": [\"27466343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SNX27 binds parathyroid hormone receptor (PTHR) via a PDZ domain-PDZ-binding motif interaction at endosomes. Mass spectrometry identified SNX27 in isolated endosomes as a PTHR binding partner. Depletion of SNX27 or VPS35 or actin depolymerization decreased the rate of PTHR recycling. PTHR can also engage retromer directly through VPS26, forming a ternary PTHR/SNX27/retromer complex.\",\n      \"method\": \"Mass spectrometry, Co-IP, molecular dynamics, protein binding assays, siRNA knockdown, receptor recycling assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification with biochemical validation and functional recycling assay, multiple methods in single lab\",\n      \"pmids\": [\"27008860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SNX27 deficiency in mice results in reductions in ependymal cells and cilia density and severe postnatal hydrocephalus. SNX27 knockout leads to Notch hyperactivation, and inhibition of Notch intracellular domain signaling with γ-secretase inhibitors reversed ependymal cell/cilia loss and ventricular dilation, indicating SNX27 promotes ependymal cell differentiation and ciliogenesis by suppressing γ-secretase-dependent Notch signaling.\",\n      \"method\": \"SNX27 knockout mouse, γ-secretase inhibitor rescue, immunohistochemistry, cilia density quantification\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with pharmacological rescue establishing pathway position, single lab\",\n      \"pmids\": [\"27974614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PTEN physically interacts with SNX27, and this interaction (phosphatase-independent) blocks the association of SNX27 with VPS26, thereby preventing SNX27-retromer assembly and impairing GLUT1 recycling from endosomes to the plasma membrane.\",\n      \"method\": \"Co-IP, siRNA knockdown, glucose uptake assay, surface biotinylation, somatic mutant analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing interaction mechanism, functional KD with GLUT1 trafficking readout, single lab\",\n      \"pmids\": [\"29117568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SNX27 limits TCR-stimulated DAG-based signals in T lymphocytes by recycling DGKζ (diacylglycerol kinase ζ) via a PDZ-domain interaction. SNX27 silencing enhanced AP-1 and NF-κB transcription, while DGKζ silencing did not increase transcription, suggesting DGKζ function is SNX27-dependent.\",\n      \"method\": \"siRNA silencing, transcription reporter assays, Co-IP, Snx27-/- mouse analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional KD and genetic KO with transcriptional readouts, single lab\",\n      \"pmids\": [\"29180720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SNX27 directly interacts with the PDZ-binding motif of ASCT2 (glutamine transporter SLC1A5) via its PDZ domain. CRISPR-mediated SNX27 KO causes ASCT2 missorting to lysosomes, reducing surface ASCT2, glutamine uptake, and mTORC1 activation, while enhancing autophagy.\",\n      \"method\": \"CRISPR KO, subcellular fractionation, surface biotinylation, glutamine uptake assay, mTORC1 signaling assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR KO with multiple functional readouts (trafficking, glutamine uptake, mTORC1, autophagy), direct interaction established biochemically; multiple orthogonal methods\",\n      \"pmids\": [\"29563155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cholera toxin causes PKA-dependent phosphorylation of an amino acid in the SNX27 PDZ domain, inhibiting SNX27-mediated trafficking of NHE3 from early endosomes to the plasma membrane. Mutagenesis (Ser to Asp) phenocopied loss of SNX27 function. Cholera toxin also destabilizes retromer. These effects can be partially rescued by pharmacological chaperones that enhance retromer stability.\",\n      \"method\": \"Phospho-mutagenesis, siRNA knockdown, surface biotinylation, NHE3 activity assay, pharmacological rescue\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — phospho-mutagenesis establishing PTM mechanism, functional trafficking assay, single lab\",\n      \"pmids\": [\"30030371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"OTULIN's C-terminal PDZ-binding motif (PDZbm) binds the cargo-binding site in the SNX27 PDZ domain. A second interface between the OTULIN OTU domain and SNX27 PDZ domain contributes to high-affinity interaction (revealed by crystal structure). OTULIN does not affect SNX27's catalytic function but antagonizes SNX27-dependent cargo loading, VPS26A binding, and endosome-to-plasma membrane trafficking.\",\n      \"method\": \"X-ray crystallography, Co-IP, mass spectrometry, siRNA knockdown, surface trafficking assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with biochemical and functional validation of a non-catalytic regulatory interaction, multiple orthogonal methods\",\n      \"pmids\": [\"31541095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SNX27-mediated recycling of neuroligin-2 requires direct interaction between the SNX27 PDZ domain and the PDZ-binding motif in neuroligin-2. SNX27 knockdown reduces surface neuroligin-2, decreasing inhibitory synapse clustering and signaling strength; overexpression has the opposite effect.\",\n      \"method\": \"Co-IP, siRNA knockdown, live-cell imaging, electrophysiology, immunofluorescence\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing direct interaction, functional KD with synaptic and electrophysiological readouts, single lab\",\n      \"pmids\": [\"31775031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SNX27 and retromer directly interact with MT1-MMP (ITC-based binding studies) and selectively recycle MT1-MMP (but not MT2-MMP) to invadopodia in metastatic breast cancer cells. SNX27 depletion reduces matrix degradation activity.\",\n      \"method\": \"ITC binding assay, siRNA knockdown, matrix degradation assay, Co-IP, colocalization imaging\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ITC establishing direct binding, functional KD with specific cargo selectivity demonstrated, single lab\",\n      \"pmids\": [\"31820782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SNX27 regulates DRA (SLC26A3) activity and recycling via a direct PDZ domain-PDZ-binding motif interaction. SNX27 knockdown reduced DRA activity by 50% without decreasing DRA surface expression, indicating SNX27 directs DRA to active lipid raft domains. SNX27 and DRA colocalize in Rab5-positive early endosomes at the apical pole of intestinal cells.\",\n      \"method\": \"siRNA knockdown, PDZ domain interaction assay, DRA activity assay (chloride flux), superresolution microscopy, subcellular colocalization\",\n      \"journal\": \"American journal of physiology. Gastrointestinal and liver physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction established biochemically with functional KD and activity assay, single lab\",\n      \"pmids\": [\"32116023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MAPK11/14 (p38 kinases), activated by multiple extracellular stressors (starvation, LPS, IL-6, EGF), directly phosphorylate SNX27 at serine 51. This phosphorylation alters the conformation of the SNX27 cargo-binding pocket and decreases SNX27-cargo interactions, thereby inhibiting endocytic recycling and promoting lysosomal degradation of cargo.\",\n      \"method\": \"In vitro kinase assay, phospho-site mutagenesis, Co-IP, cargo recycling assay, structural/conformational analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay establishing direct phosphorylation at defined site, mutagenesis confirming mechanistic consequence, functional trafficking readout; multiple orthogonal methods in single study\",\n      \"pmids\": [\"33605979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SNX27 interacts with VARP (VPS9-ankyrin repeat protein/ANKRD27) as a new retromer-interacting protein. VARP depletion causes differential trafficking defects of retromer cargo, suggesting cargo-specific roles within the SNX27-retromer pathway.\",\n      \"method\": \"Quantitative proteomics, Co-IP, siRNA knockdown, trafficking assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative proteomics followed by Co-IP and KD with trafficking phenotype, single lab\",\n      \"pmids\": [\"25278552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SNX27 inhibits TNFα-induced NF-κB signaling activation by facilitating OTULIN localization to the TNF receptor complex at the membrane. SNX27-retromer translocation is required for this membrane targeting; chemical inhibition of SNX27-retromer (by cholera toxin) blocks OTULIN membrane localization.\",\n      \"method\": \"Co-IP, siRNA knockdown, NF-κB reporter assay, fractionation, cholera toxin inhibition\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional reporter and pharmacological inhibition confirming mechanism, single lab\",\n      \"pmids\": [\"34315543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"AQP4 is a cargo of the SNX27-retromer complex. Kidins220 deficiency causes downregulation of SNX27-retromer, resulting in AQP4 lysosomal degradation. SNX27 silencing decreases AQP4 levels; SNX27 overexpression restores AQP4 content in Kidins220-deficient astrocytes.\",\n      \"method\": \"siRNA knockdown, SNX27 overexpression, lysosomal degradation assay, Co-IP, immunofluorescence, conditional KO mouse\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with gain/loss of function establishing AQP4 as SNX27-retromer cargo, single lab\",\n      \"pmids\": [\"34002021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The SNX27 FERM domain directly binds the flexible SNX1/SNX2 N-terminus through acidic-DxF motifs. Forty residues containing two DxF motifs in the SNX1 N-terminus are sufficient for SNX27 binding (KD ~10 µM by ITC). Mutation of either DxF sequence abrogates binding.\",\n      \"method\": \"Pulldown with purified proteins, ITC calorimetry, mutagenesis, sequence alignment\",\n      \"journal\": \"Advances in biological regulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified proteins, ITC quantification, and mutagenesis confirming binding determinants in a single study\",\n      \"pmids\": [\"34866035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SNX27 directly interacts with ACE2 via the ACE2 PDZ-binding motif and the SNX27 PDZ domain (complex structure determined). SNX27-retromer prevents ACE2/SARS-CoV-2 virus complex from entering lysosomes/late endosomes, thereby decreasing viral endocytic entry in cells where the endocytic pathway dominates.\",\n      \"method\": \"Crystal structure, functional viral infection assay, siRNA knockdown, surface trafficking assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of PDZ-PBM complex combined with functional viral infection assay and KD validation, multiple orthogonal methods\",\n      \"pmids\": [\"35022217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The SNX27 FERM domain directly binds acidic-Asp-Leu-Phe (aDLF) motifs in the SNX1/SNX2 subunits of ESCPE-1, establishing a 'handover' model where SNX27-Retromer-captured cargo proteins are transferred into ESCPE-1 transport carriers for endosome-to-plasma membrane recycling. This assembly of SNX27:Retromer:ESCPE-1 evolved in a stepwise manner during early metazoan evolution.\",\n      \"method\": \"Biochemical reconstitution, structural analysis, mutagenesis, cellular trafficking assays, evolutionary analysis\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — biochemical reconstitution combined with structural analysis, mutagenesis, and cellular validation in a single comprehensive study\",\n      \"pmids\": [\"35417450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SNX27 interacts with TANC2 via its PDZ domain; in the absence of HPV-18 E6, SNX27 directs TANC2 toward lysosomal degradation. HPV-18 E6 inhibits SNX27-TANC2 interaction in a PBM-dependent manner, increasing TANC2 levels and enhancing cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, siRNA knockdown, cell proliferation assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus KD with functional proliferation readout, single lab\",\n      \"pmids\": [\"36326272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SNX27 regulates apical targeting and turnover of membrane mucin MUC17 in enterocytes. SNX27 controls MUC17 turnover at the brush border in concert with the motor protein MYO1B.\",\n      \"method\": \"siRNA knockdown, surface biotinylation, pulse-chase turnover assay, immunofluorescence\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional KD with defined cargo trafficking phenotype, single lab\",\n      \"pmids\": [\"39661054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Crystal structures reveal that FAM21 (WASH complex subunit) binds the SNX27 FERM domain using aDLF motifs similar to those found in SNX1/SNX2. Overlapping FAM21 repeats and a Pro-Leu-containing motif bind three distinct sites on Retromer (VPS35 and VPS29). Mutation of the major VPS35-binding site partially reduces endosomal WASH association without fully preventing cargo recycling.\",\n      \"method\": \"X-ray crystallography, AlphaFold modeling, biochemical mutagenesis, Co-IP, cellular trafficking assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures combined with biochemical mutagenesis and functional cellular validation, multiple orthogonal methods establishing molecular basis of WASH-SNX27-Retromer coupling\",\n      \"pmids\": [\"39116126\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"VARP directly interacts with SNX27 (new interaction identified by biochemical/biophysical approaches and AlphaFold modeling). VARP co-immunoprecipitates all coat components (SNX27, ESCPE-1, Retromer) in cells and is required to reconstitute a proposed endosomal 'supercomplex' in vitro. SNX27 alone and with Retromer remodels PI(3)P-containing membranes carrying PDZbm cargo into tubules in a reconstituted system.\",\n      \"method\": \"Biochemical reconstitution with purified proteins, liposome tubulation assay, AlphaFold modeling, Co-IP, ITC/biophysical binding measurements\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — full biochemical reconstitution with purified proteins on physiological lipid membranes, combined with structural modeling and cellular Co-IP validation; multiple orthogonal methods\",\n      \"pmids\": [\"39937906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PI(3)P synthesis during chemical LTP induction drives coordinate recruitment of SNX27-Retromer to endosomes and synaptic sites in hippocampal neurons. Both SNX27-Retromer and SNX17-Retriever pathways are necessary for cLTP-dependent dendritic spine structural enlargement, acting in parallel by recycling distinct cargo sets. Preventing PI(3)P synthesis blocks synaptic recruitment of SNX27, decreases cargo recycling, and blocks LTP.\",\n      \"method\": \"Live-cell imaging in primary hippocampal neurons, PI(3)P biosensor, siRNA/shRNA knockdown, dendritic spine morphometry, LTP recording in hippocampal slices\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (imaging, electrophysiology, genetic KD) with functional LTP readout in neurons and slices; replicates across multiple levels of analysis\",\n      \"pmids\": [\"40920104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SNX27 (identified as a new PDZ-containing protein) interacts specifically with the 5-HT4(a) receptor splice variant via a PDZ-domain interaction. SNX27a redirects part of the 5-HT4(a)R to early endosomes.\",\n      \"method\": \"Peptide-affinity chromatography, 2D electrophoresis, mass spectrometry, subcellular localization imaging\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — proteomic identification confirmed by subcellular localization imaging, single lab; early characterization study\",\n      \"pmids\": [\"15466885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Endosomal SNX27 polarizes to the immunological synapse (IS) in a distinct compartment adjacent to cytotoxic granules during NK cell tumor engagement, and polarizes to the apical membrane during NK cell migration.\",\n      \"method\": \"In vitro NK-tumor conjugation assay, fluorescence microscopy\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single localization experiment, no functional consequence established, single lab\",\n      \"pmids\": [\"17644068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SNX27 interacts with GPR17 via a PDZ-binding motif at the GPR17 C-terminus and mediates GPR17 plasma membrane recycling in oligodendrocytes. SNX27 knockdown reduces GPR17 plasma membrane recycling and accelerates oligodendrocyte terminal maturation.\",\n      \"method\": \"Co-IP, siRNA knockdown, surface trafficking assay, cell differentiation assay\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional KD establishing cargo recycling and differentiation consequences, single lab\",\n      \"pmids\": [\"27270750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HTLV-1 Tax-1 interacts with SNX27 via its PDZ-binding motif and the SNX27 PDZ domain. Tax-1 overexpression causes reduction of GLUT1 on the plasma membrane. SNX27 knockdown increases virion release and decreases HTLV-1 infectivity, revealing a mechanism by which HTLV-1 regulates a receptor post-infection.\",\n      \"method\": \"Mass spectrometry, Co-IP, flow cytometry (surface GLUT1), siRNA knockdown, viral infectivity assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification with Co-IP validation and functional GLUT1 and infectivity assays, single lab\",\n      \"pmids\": [\"30897179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SARS-CoV-2 spike (S) protein binds to the PDZ domain of SNX27 through an 'MTSC' motif (not a canonical PDZbm). Abrogation of either the SNX27 PDZ domain or the S protein MTSC motif decreases surface S protein expression and viral production.\",\n      \"method\": \"Co-IP, mutagenesis, surface expression assay, viral production assay\",\n      \"journal\": \"MedComm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with mutagenesis validation and functional viral output assay, single lab\",\n      \"pmids\": [\"34909756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"VPS26A-retromer, together with SNX27, mediates unconventional protein secretion (Golgi-bypass) of transmembrane proteins including trafficking-deficient ΔF508-CFTR and SARS-CoV-2 spike protein under cellular stress. SNX27 recruits ΔF508-CFTR to the VPS26A-VPS35-VPS29 retromer complex for transport to the cell surface under UPS-inducing conditions.\",\n      \"method\": \"CRISPR KO screen, molecular interaction analysis, surface expression assay, viral particle assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — targeted CRISPR screen identifying VPS26A, followed by molecular interaction and surface trafficking analyses; single lab\",\n      \"pmids\": [\"41942457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SNX27 interacts with EMILIN2 via its PDZ domain; HPV-18 E6 enhances (rather than disrupts) this SNX27-EMILIN2 interaction in a PBM-dependent manner, blocking EMILIN2 secretion and its inhibition of WNT1 signaling.\",\n      \"method\": \"Co-IP, mass spectrometry proteomics, siRNA knockdown, WNT signaling assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP identification with functional signaling assay, single lab, mechanism of enhanced interaction not fully characterized\",\n      \"pmids\": [\"38874360\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Tex264 interacts with SNX27 (confirmed by Co-IP and immunofluorescence). siRNA-mediated TEX264 knockdown inhibits cell migration potentially through reduced SNX27-mediated Itgα5 receptor membrane recycling.\",\n      \"method\": \"Co-IP, immunofluorescence, siRNA knockdown, cell migration assay\",\n      \"journal\": \"BioMed research international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP establishing interaction, functional KD with migration phenotype but limited mechanistic detail, single lab\",\n      \"pmids\": [\"35837377\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SNX27 is an endosomal adaptor protein that uses its PX domain to bind PtdIns(3)P and localize to early endosomes, its PDZ domain to capture transmembrane cargo bearing PDZ-binding motifs (with affinity enhanced by phosphorylation of upstream acidic residues), and its FERM domain to interact with the VPS26 subunit of the retromer heterotrimer, the aDLF motifs of SNX1/SNX2 (ESCPE-1), and FAM21 (WASH complex); together these interactions form a hierarchical endosomal coat (SNX27–Retromer–ESCPE-1–WASH supercomplex, stabilized by VARP) that captures >100 cargo proteins and transfers them into tubular transport carriers for recycling to the plasma membrane, a process regulated by direct phosphorylation of SNX27 at Ser51 by stress-activated MAPK11/14, by competitive binding of OTULIN or PTEN to the SNX27 PDZ and FERM domains, and by dynamic PI(3)P synthesis that coordinates SNX27 recruitment to synapses during long-term potentiation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SNX27 is an endosomal sorting nexin that functions as a cargo-selective adaptor coupling PDZ-binding-motif (PBM)-containing transmembrane proteins to the retromer complex for endosome-to-plasma-membrane recycling, preventing their default lysosomal degradation [#0, #3]. Its modular architecture integrates three activities: a PX domain that binds PtdIns(3)P to target early endosomes [#2], a PDZ domain that recognizes C-terminal PBMs on cargo, and a FERM domain that engages the retromer and downstream coat machinery [#26, #28]. The PDZ domain directly binds the retromer subunit VPS26A through an exposed β-hairpin, and this interaction reciprocally enhances PDZ affinity for cargo PBMs by an order of magnitude, embedding cooperativity into cargo selection [#5]; engagement is further tuned by acidic residues upstream of the PBM whose function can be substituted by regulated phosphorylation, creating a phospho-switch for cargo capture [#10]. Through these interactions SNX27 recycles over 100 surface proteins, including nutrient and ion transporters (GLUT1, ASCT2/SLC1A5, DRA/SLC26A3), signaling receptors (β2-adrenoreceptor, NMDA receptor, GPR17), and adhesion/junction proteins [#3, #16, #21]. The SNX27 FERM domain organizes a hierarchical endosomal coat by binding aDLF/DxF motifs in the SNX1/SNX2 subunits of ESCPE-1 — handing cargo into tubular transport carriers — and analogous aDLF motifs in FAM21 of the WASH complex, with VARP bridging the SNX27–Retromer–ESCPE-1 assembly into a reconstitutable supercomplex that remodels PI(3)P membranes into cargo-laden tubules [#26, #28, #31, #32]. Recycling output is controlled by post-translational and competitive regulation: stress-activated MAPK11/14 (p38) directly phosphorylate SNX27 at Ser51 to reshape the cargo-binding pocket and redirect cargo to lysosomes [#22], while PTEN and OTULIN competitively bind the SNX27 PDZ/FERM surfaces to block VPS26A association and cargo loading [#14, #18]. Beyond housekeeping recycling, SNX27 shapes physiology in neurons, where PI(3)P-driven recruitment supports synaptic cargo recycling during LTP [#33], and is exploited by viruses including SARS-CoV-2, whose spike and ACE2 engage the SNX27 PDZ domain to influence endocytic entry and surface expression [#27, #38].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established SNX27 as a PDZ-domain protein capable of binding a specific GPCR splice variant and directing it to endosomes, the first hint of an endosomal sorting role.\",\n      \"evidence\": \"Peptide-affinity chromatography, mass spectrometry and localization imaging of the 5-HT4(a) receptor\",\n      \"pmids\": [\"15466885\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No retromer link or recycling function defined\", \"Mechanism of endosomal targeting unaddressed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined the two-domain logic of SNX27 sorting — PX-domain PtdIns(3)P binding for endosome targeting and PDZ-domain recognition of cargo PBMs — and showed it is required for recycling of β2AR and NMDA receptor cargo to the surface.\",\n      \"evidence\": \"Knockdown/knockout, subcellular fractionation, domain mutagenesis and endocytosis/recycling assays for β2AR and NR2C\",\n      \"pmids\": [\"20733053\", \"21300787\", \"21602791\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of retromer coupling not yet resolved\", \"Cargo repertoire unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Generalized SNX27 from a few-receptor adaptor to a master recycling hub for >100 cargo and showed that direct PDZ–VPS26 binding is necessary and sufficient to divert cargo away from lysosomes.\",\n      \"evidence\": \"Quantitative interactome and surface proteomics with domain-mutant rescue in SNX27/retromer-depleted cells\",\n      \"pmids\": [\"23563491\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PDZ–VPS26 cooperativity not yet defined\", \"How tubular carriers form downstream unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided the structural mechanism by which retromer enhances cargo capture: VPS26A binds an exposed PDZ β-hairpin and allosterically increases PDZ affinity for cargo PBMs, establishing cooperative cargo selection.\",\n      \"evidence\": \"X-ray crystallography, NMR, ITC/SPR and cell-based sorting assays of the SNX27 PDZ–VPS26A complex\",\n      \"pmids\": [\"25136126\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address FERM-domain partner interactions\", \"Regulation of the allosteric switch not examined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified an acidic/phosphorylation code upstream of the PBM that controls high-affinity PDZ engagement, defining a phospho-regulated switch for cargo selection.\",\n      \"evidence\": \"Crystallography, NMR, ITC and phosphopeptide binding with cell-based trafficking assays\",\n      \"pmids\": [\"27595347\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinases generating the relevant phosphorylations on cargo not all identified\", \"In vivo prevalence of the switch unquantified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked SNX27 to actin-based endosomal sorting machinery by showing direct PDZ-domain binding to FAM21 of the WASH complex controls SNX27 subdomain localization and PI4P levels to prevent Golgi mis-sorting.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, localization imaging and lipid measurement\",\n      \"pmids\": [\"26956659\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of FAM21 binding not resolved at this stage\", \"PDZ vs FERM contribution to FAM21 binding not disentangled\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that SNX27 loss redirects nutrient transporter cargo to lysosomes with downstream metabolic consequences, connecting recycling to mTORC1 signaling and autophagy.\",\n      \"evidence\": \"CRISPR KO with surface biotinylation, glutamine uptake, mTORC1 and autophagy readouts for ASCT2/SLC1A5\",\n      \"pmids\": [\"29563155\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other transporters share this metabolic coupling not established\", \"Tissue-level metabolic phenotype not addressed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established post-translational and competitive regulation of SNX27: PKA-driven PDZ phosphorylation (cholera toxin) and phosphatase-independent PTEN binding both block VPS26 association and cargo recycling.\",\n      \"evidence\": \"Phospho-mutagenesis, Co-IP, surface biotinylation and trafficking/uptake assays (NHE3, GLUT1)\",\n      \"pmids\": [\"30030371\", \"29117568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological signals controlling PTEN–SNX27 competition unclear\", \"Phospho-site identity in cholera-toxin model not crystallographically resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealed dual-mode competitive inhibition by OTULIN, which uses both its PBM and a second OTU–PDZ interface to occupy the cargo-binding site and antagonize cargo loading without affecting catalysis.\",\n      \"evidence\": \"X-ray crystallography, Co-IP, mass spectrometry and surface trafficking assays\",\n      \"pmids\": [\"31541095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular trigger that shifts OTULIN between competitor and cargo not defined here\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified the master stress switch on SNX27 itself: p38 MAPK (MAPK11/14) directly phosphorylates Ser51 to reshape the cargo-binding pocket, globally suppressing recycling and promoting lysosomal degradation under stress.\",\n      \"evidence\": \"In vitro kinase assay, phospho-site mutagenesis, Co-IP and cargo recycling/conformational analysis\",\n      \"pmids\": [\"33605979\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which cargo subsets are most sensitive to Ser51 phosphorylation not resolved\", \"Phosphatase reversing Ser51 unidentified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Expanded the coat to include VARP as a retromer-interacting partner with cargo-specific roles, foreshadowing a higher-order assembly.\",\n      \"evidence\": \"Quantitative proteomics, Co-IP and siRNA knockdown with trafficking assays\",\n      \"pmids\": [\"25278552\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct SNX27–VARP contact not yet defined at this stage\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the FERM-domain handover mechanism: SNX27 directly binds aDLF/DxF motifs in SNX1/SNX2 of ESCPE-1, transferring captured cargo into tubular carriers, an assembly tracing to early metazoan evolution.\",\n      \"evidence\": \"Biochemical reconstitution, structural analysis, mutagenesis, ITC and cellular trafficking with evolutionary analysis\",\n      \"pmids\": [\"35417450\", \"34866035\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the cargo handover in carriers not fully defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed FAM21 uses aDLF motifs analogous to ESCPE-1 to bind the SNX27 FERM domain and contacts Retromer at three sites, molecularly unifying WASH–SNX27–Retromer coupling.\",\n      \"evidence\": \"Crystallography, AlphaFold modeling, mutagenesis, Co-IP and cellular trafficking\",\n      \"pmids\": [\"39116126\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why VPS35-site mutation only partially reduces WASH association unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Reconstituted the full endosomal coat in vitro, demonstrating VARP directly binds SNX27 and is required to assemble the SNX27–Retromer–ESCPE-1 supercomplex, with SNX27/Retromer alone remodeling PI(3)P membranes carrying PBM cargo into tubules.\",\n      \"evidence\": \"Reconstitution with purified proteins, liposome tubulation, AlphaFold modeling, Co-IP and ITC\",\n      \"pmids\": [\"39937906\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native regulation and disassembly of the supercomplex in cells not addressed\", \"Cryo-EM structure of the assembled coat absent\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed SNX27 recycling in neuronal plasticity, showing PI(3)P synthesis during LTP recruits SNX27-Retromer to synapses to drive cargo recycling and spine enlargement in parallel with SNX17-Retriever.\",\n      \"evidence\": \"Live imaging with PI(3)P biosensor, knockdown, spine morphometry and LTP recordings in hippocampal neurons/slices\",\n      \"pmids\": [\"40920104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the LTP-relevant SNX27 cargo set not fully enumerated\", \"PI 3-kinase driving synaptic PI(3)P synthesis not pinned down\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple regulatory inputs (Ser51 phosphorylation, PTEN and OTULIN competition, cargo-PBM phosphorylation, PI(3)P dynamics) are integrated in real time to set cargo-specific recycling versus degradation outcomes remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model coupling stress kinase signaling to coat assembly state\", \"In vivo phenotypic dissection of individual regulatory arms incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 3, 5]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 8]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [3, 16, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0, 2, 21]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 8]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 3, 28]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [3, 16, 39]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [22, 24]}\n    ],\n    \"complexes\": [\n      \"SNX27-Retromer-ESCPE-1 supercomplex\",\n      \"Retromer (VPS26-VPS35-VPS29)\",\n      \"WASH complex (via FAM21)\"\n    ],\n    \"partners\": [\n      \"VPS26A\",\n      \"SNX1\",\n      \"SNX2\",\n      \"FAM21\",\n      \"VARP\",\n      \"OTULIN\",\n      \"PTEN\",\n      \"MAPK14\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}