{"gene":"NHERF2","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":1998,"finding":"NHERF2 (E3KARP) directly binds NHE3 via its second PDZ domain plus C-terminal domain, and also binds the cytoskeletal protein ezrin via its C-terminal domain, functioning as a scaffold that links NHE3 to ezrin (a PKA type II anchoring protein), thereby localizing cAMP-dependent protein kinase near NHE3 to allow NHE3 phosphorylation and inhibition.","method":"In vitro binding assays, co-localization in PS120 fibroblasts, co-immunoprecipitation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro binding assays with domain mapping plus co-IP, replicated across two papers (PMID:9748260, PMID:9792717)","pmids":["9748260","9792717"],"is_preprint":false},{"year":1998,"finding":"NHERF2 (E3KARP) is not phosphorylated by cAMP, indicating it acts as a scaffolding adapter (not a direct PKA substrate) that links NHE3 to ezrin to localize PKA type II near NHE3 for cAMP-dependent inhibition of NHE3.","method":"In vivo phosphorylation studies, co-immunoprecipitation in opossum kidney cells, cAMP analog specificity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (phosphorylation assay, Co-IP, NHE3 activity assay) in endogenous cell system","pmids":["9792717"],"is_preprint":false},{"year":2000,"finding":"NHERF2 (E3KARP) associates with CFTR preferentially via CFTR's C-terminal PDZ-binding motif and E3KARP's second PDZ domain with nanomolar affinity; E3KARP is predominantly membrane-localized and co-localizes with CFTR at the apical membrane of airway cells; co-expression of CFTR, E3KARP, and ezrin in Xenopus oocytes potentiates cAMP-stimulated CFTR Cl- currents, suggesting E3KARP scaffolds CFTR to ezrin/PKA.","method":"Co-immunoprecipitation, confocal immunofluorescence, cell fractionation, Xenopus oocyte electrophysiology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, fractionation, localization, and functional reconstitution in oocytes","pmids":["10893422"],"is_preprint":false},{"year":2000,"finding":"E3KARP (NHERF2) binds tightly to the ezrin N-ERMAD but has little affinity for the merlin N-ERMAD, establishing a hierarchy of ERM-family scaffolding interactions.","method":"In vitro binding assays with recombinant proteins","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro reconstitution, single lab","pmids":["11106646"],"is_preprint":false},{"year":2001,"finding":"NHERF-2 PDZ domains associate with each other robustly in the absence of other proteins (homo-oligomerization), and NHERF-1 and NHERF-2 form homo- and hetero-oligomers in cells. NHERF-2 oligomerization is not regulated by phosphorylation (unlike NHERF-1), but may facilitate formation of signaling complexes.","method":"Biochemical PDZ domain association assays with purified proteins, co-immunoprecipitation with differentially tagged proteins","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro plus cellular Co-IP, single lab","pmids":["11456497"],"is_preprint":false},{"year":2001,"finding":"Glucocorticoid (dexamethasone) activation of NHE3 requires NHERF2 (but not NHERF1) acting as a scaffold, and this activation is mediated by SGK1 interacting with the PDZ domains of NHERF2. Kinase-dead SGK1 blocked dexamethasone activation of NHE3.","method":"NHE3 activity assay in PS120 and opossum kidney cells, dominant-negative SGK1 expression, protein interaction studies","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — functional NHE3 activity assays with dominant-negative approach plus specificity for NHERF2 over NHERF1, single lab but multiple orthogonal methods","pmids":["11751930"],"is_preprint":false},{"year":2002,"finding":"Ca2+-dependent inhibition of NHE3 specifically requires E3KARP (NHERF2), not NHERF1; elevated Ca2+ induces Ca2+-dependent association between alpha-actinin-4 and E3KARP (through alpha-actinin-4's actin-binding plus spectrin repeat domain), forming an NHE3-E3KARP-alpha-actinin-4 complex that leads to NHE3 oligomerization and endocytosis.","method":"NHE3 activity assays in PS120 fibroblasts expressing E3KARP vs NHERF1, co-immunoprecipitation, dominant-negative overexpression, endocytosis assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (activity, Co-IP, dominant-negative), mechanism defined at molecular level","pmids":["11948184"],"is_preprint":false},{"year":2002,"finding":"Adenosine A2b receptor co-immunoprecipitates with E3KARP (NHERF2) and ezrin upon agonist stimulation; E3KARP-ezrin interaction is enhanced by agonist stimulation, suggesting A2bR is recruited to a plasma membrane signaling complex anchored by E3KARP.","method":"Co-immunoprecipitation from T84 and Caco2-BBE cells, GFP-A2bR stable expression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP with agonist stimulation condition, single lab","pmids":["12080047"],"is_preprint":false},{"year":2002,"finding":"The DRA (SLC26A3) Cl-/HCO3- exchanger C-terminal ETKF motif binds specifically to the second PDZ domain of E3KARP (NHERF2) in vitro with comparable affinity to CFTR, and DRA, NHE3, and E3KARP co-localize in the apical compartment of human proximal colon, suggesting E3KARP dimerization links NHE3 and DRA.","method":"In vitro PDZ-binding assays, immunofluorescence colocalization","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro binding plus colocalization, single lab","pmids":["12369822"],"is_preprint":false},{"year":2002,"finding":"SGK1 and NHERF2 synergize to stimulate ROMK1 K+ channel activity in Xenopus oocytes: co-expression of both (but not either alone) increases K+ channel activity and membrane abundance of ROMK1, and decreases decay of channel activity after brefeldin A treatment, indicating NHERF2 and SGK1 together enhance ROMK1 membrane retention.","method":"Xenopus oocyte electrophysiology, channel current measurements, surface abundance assays","journal":"Journal of the American Society of Nephrology","confidence":"Medium","confidence_rationale":"Tier 2 — functional reconstitution in oocytes with mechanistic insight, single lab","pmids":["12444200"],"is_preprint":false},{"year":2003,"finding":"Ca2+-dependent inhibition of NHE3 requires PKCα, which binds to the PDZ1 domain of E3KARP (NHERF2) in a Ca2+-dependent manner. PKCα and E3KARP co-immunoprecipitate from cells (enhanced by ionomycin). PKCα is necessary for Ca2+-induced decrease in surface NHE3 (endocytosis) but not for Ca2+-dependent NHE3 oligomerization.","method":"PKC inhibitor assays, GST pulldown (in vitro), co-immunoprecipitation, surface biotinylation","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — in vitro binding, Co-IP, functional inhibitor experiments, and surface quantification in same study","pmids":["12954600"],"is_preprint":false},{"year":2004,"finding":"LPA2 receptor (but not other LPA receptor isoforms) specifically interacts with NHERF2 via LPA2's C-terminal PDZ-binding motif and NHERF2's second PDZ domain. NHERF2 uses its second PDZ domain to indirectly link LPA2 to PLC-β3 to form a ternary complex, potentiating LPA-induced PLC-β activation (specifically PLC-β3) and downstream ERK/COX-2 signaling.","method":"Co-immunoprecipitation, siRNA knockdown of NHERF2 and PLC-β3, PDZ-binding motif mutagenesis, PLC activity assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, mutagenesis, siRNA with functional readout, multiple orthogonal methods","pmids":["15143197"],"is_preprint":false},{"year":2004,"finding":"LPA induces exocytic trafficking of NHE3 to the apical membrane in an E3KARP (NHERF2)-dependent manner via activation of PLC and subsequent elevation of intracellular Ca2+; PLC inhibition and intracellular Ca2+ chelation block LPA-induced NHE3 exocytosis, whereas PKC inhibition does not.","method":"NHE3 activity assays, surface NHE3 quantification, pharmacological inhibitors of PLC/Ca2+/PKC in OK cells","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 — functional assays with multiple pharmacological inhibitors, E3KARP-dependent mechanism, single lab","pmids":["15238220"],"is_preprint":false},{"year":2004,"finding":"NHERF2 interacts with TRPV5 via its C-tail in a Ca2+-independent manner (PDZ interaction), and NHERF2 plus SGK1 together enhance TRPV5-mediated Ca2+ entry and membrane abundance in Xenopus oocytes; the second PDZ domain of NHERF2 is required for this stimulatory effect.","method":"Xenopus oocyte electrophysiology, pull-down assays, PDZ domain deletion mutants, tracer Ca2+ uptake","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — functional oocyte assays with domain mutagenesis and binding assays","pmids":["15319523","15665527"],"is_preprint":false},{"year":2005,"finding":"NHERF2 (E3KARP) acting as a PKG-anchoring protein is required for cGMP-dependent inhibition of NHE3: NHERF2 (but not NHERF1) binds cGKII in vitro via the NHERF2 PDZ2 C-terminus, and myristoylation of cGKII is necessary for cGMP inhibition of NHE3. NHERF2 also restores cAMP inhibition of NHE3 in PS120 cells.","method":"NHE3 activity assays in PS120 cells, in vitro kinase-NHERF2 binding assays, myristoylation mutants, cGKI vs cGKII specificity","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro binding, functional activity assays, mutant specificity, multiple orthogonal approaches","pmids":["15722341"],"is_preprint":false},{"year":2005,"finding":"P2Y1 receptor C-terminus specifically interacts with the second PDZ domain of NHERF-2; this interaction is confirmed by Co-IP in cells and enables NHERF-2-mediated tethering of P2Y1R to PLC-β; coexpression of NHERF-2 with P2Y1R prolongs P2Y1R-mediated Ca2+ signaling in glial cells, while disruption of the P2Y1R-NHERF-2 interaction attenuates Ca2+ response duration.","method":"PDZ domain proteomic array, co-immunoprecipitation, Ca2+ signaling assays, point mutations","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — PDZ array + Co-IP + functional Ca2+ assay + mutagenesis, multiple orthogonal methods","pmids":["15901899"],"is_preprint":false},{"year":2005,"finding":"NHERF-2 and podocalyxin co-localize at the free surface of single MDCK cells and at a subdomain of the apical membrane during polarization; the PDZ-binding motif of podocalyxin targets it to this domain, and NHERF-2 participates in formation of an early apical scaffold via PDZ domain-mediated interactions during epithelial polarization.","method":"Domain mutant analysis, RNA interference, confocal microscopy in MDCK cells","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — domain mutants, RNAi, live imaging, mechanistic link to polarization","pmids":["15642748"],"is_preprint":false},{"year":2005,"finding":"NHERF2 (SIP-1) interacts with SRY (sex-determining region Y protein) via the NHERF2 PDZ1 domain; mouse and human SRY both induce nuclear accumulation of NHERF2 in cultured cells, and SRY and NHERF2 are co-expressed in the nucleus of pre-Sertoli cells during testis determination.","method":"Yeast two-hybrid, co-immunoprecipitation, immunofluorescence in cultured cells and transgenic mouse model","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP, nuclear co-localization in vivo, single lab","pmids":["16166090"],"is_preprint":false},{"year":2006,"finding":"NHERF-2 specifically interacts with mGluR5 (but not mGluR1a) via the second PDZ domain of NHERF-2, as confirmed by co-immunoprecipitation and confocal microscopy; coexpression of NHERF-2 prolongs mGluR5-mediated Ca2+ mobilization and potentiates mGluR5-mediated cell death, effects absent with mGluR1a.","method":"PDZ domain array screen, reverse overlay, co-immunoprecipitation, confocal microscopy, Ca2+ signaling assays, point mutations","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — PDZ array + Co-IP + functional Ca2+ assays + mutagenesis + confocal, multiple orthogonal methods","pmids":["16891310"],"is_preprint":false},{"year":2006,"finding":"NHE3 inhibits PKA-dependent functional expression and activation of CFTR via NHERF2 PDZ interactions; when PDZ2 of NHERF2 is deleted (or 'sequestered' by NHE3 binding), PKA-dependent CFTR apical expression and activity are inhibited, demonstrating NHERF2 mediates competitive regulation between NHE3 and CFTR.","method":"Electrophysiology, NHERF2 domain deletion transfection in A6 monolayers","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — domain deletion mutagenesis with functional readout, single lab","pmids":["16824484"],"is_preprint":false},{"year":2008,"finding":"SGK1 and NHERF2 (but not NHERF1) specifically enhance PEPT2 peptide transporter function and surface abundance; the effect requires SGK1 phosphorylation at Ser185 and the C-terminal PDZ-binding motif of PEPT2; dynasore experiments show they stabilize PEPT2 at the cell surface.","method":"Xenopus oocyte electrophysiology, surface abundance immunoassays, phosphorylation-site mutagenesis, dynasore inhibition","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — oocyte functional assay, mutagenesis, surface quantification, single lab","pmids":["19088452"],"is_preprint":false},{"year":2009,"finding":"NHERF2 confers inhibitory signals by coupling the LPA receptor to CFTR in duodenal crypts: Nherf2-/- mice display augmented FSK-stimulated HCO3- secretion and lose LPA-mediated inhibition of FSK-stimulated HCO3- secretion, demonstrating NHERF2 links LPA receptor to CFTR to mediate inhibition.","method":"Loss-of-function mouse models, duodenal HCO3- secretion measurements, laser microdissection/qPCR","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockout model with specific secretory phenotype, replicated alongside NHERF1/PDZK1 comparisons","pmids":["19221439"],"is_preprint":false},{"year":2009,"finding":"LPA stimulates NHE3 and intestinal fluid absorption via LPA5 receptor; this stimulation requires NHERF2 which interacts with LPA5; Nherf2-/- mice have impaired LPA-mediated fluid absorption; LPA stimulation increases NHE3 protein abundance at the brush border membrane.","method":"Wild-type and Nherf2-/- mouse intestinal absorption assays, heterologous expression studies, protein interaction assays","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockout + heterologous expression + protein interaction, multiple orthogonal methods","pmids":["19800338"],"is_preprint":false},{"year":2010,"finding":"NHERF2 determines NHE3 mobility in brush borders; LPA stimulation of NHE3 requires NHERF2 and increases NHE3 mobility via two mechanisms: PI3K-dependent exocytic trafficking and PI3K-independent dissociation of NHE3 from NHERF2 (confirmed by FRET). NHE3 and NHERF2 co-precipitate under basal conditions but dissociate 30 min after LPA and reassociate by 50-60 min.","method":"FRAP, acceptor photobleaching FRET, NHE3 activity assays, co-precipitation, PI3K inhibitor studies in OK cells","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — FRAP + FRET + Co-precipitation + functional assays, multiple orthogonal methods, mechanistic dissection","pmids":["20571054"],"is_preprint":false},{"year":2010,"finding":"MAGI-3 competes with NHERF-2 for binding to LPA2 and PLC-β3; NHERF-2 promotes LPA2 interaction with Gαq and stimulates migration/invasion of colon cancer cells, whereas MAGI-3 promotes Gα12 coupling and inhibits these processes; the two PDZ proteins reciprocally regulate LPA2 G-protein coupling.","method":"Co-immunoprecipitation, knockdown/overexpression in HCT116/SW480 cells, migration/invasion assays, IP generation assays","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 — Co-IP, KD/OE with defined cellular phenotypes, receptor coupling specificity defined","pmids":["21134377"],"is_preprint":false},{"year":2010,"finding":"NHERF-2 co-immunoprecipitates with GLAST in astrocytes; NHERF-2 knockdown by siRNA reduces GLAST activity and total GLAST protein levels (reduced half-life in pulse-chase studies), demonstrating NHERF-2 enhances GLAST stability and activity in astrocytes.","method":"Co-immunoprecipitation from cortical astrocytes, siRNA knockdown, GLAST activity assays, pulse-chase metabolic labeling","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + siRNA KD + activity assays + pulse-chase, single lab but multiple methods","pmids":["20430067"],"is_preprint":false},{"year":2010,"finding":"NHERF2 ablation in murine intestine shifts NHE3 localization from the terminal web region to microvilli; NHERF2 is required for tethering NHE3 near the terminal web and for Ca2+ ionophore- and carbachol-mediated inhibition and STp (cGMP)-dependent inhibition of NHE3; cAMP-induced NHE3 inhibition is preserved in NHERF2-null mice.","method":"NHERF2 knockout mice, immunolocalization, fluorometric NHE3 activity assays","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — in vivo knockout with multiple mechanistic readouts and segment-specific analysis","pmids":["20962002"],"is_preprint":false},{"year":2010,"finding":"NHERF2 enhances apical localization of PMCA2w/b in polarized MDCK cells; NHERF2-mediated anchorage to the apical actin cytoskeleton (confirmed by colocalization with ezrin even after actin disruption) reduces PMCA2w/b internalization and lateral membrane mobility, as shown by surface biotinylation and FRAP.","method":"Confocal microscopy, surface biotinylation, FRAP in polarized MDCK cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — FRAP + surface biotinylation + localization, single lab but multiple orthogonal methods","pmids":["20663896"],"is_preprint":false},{"year":2010,"finding":"NHERF2 scaffold determines ion channel coupling specificity in neurons: coexpression of NHERF2 selectively reduces CaV2.2 (N-type Ca2+ channel) inhibition by P2Y1R and mGluR5 (which bind NHERF2) but not by α2-adrenoceptors (which do not bind NHERF2), restricting downstream signaling to Gq-mediated M-current inhibition.","method":"Intranuclear cDNA injection into sympathetic neurons, whole-cell patch-clamp electrophysiology, NHERF2-binding motif mutant receptor","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — functional electrophysiology with binding-motif mutant control and receptor-binding specificity, rigorous design","pmids":["20720114"],"is_preprint":false},{"year":2010,"finding":"NHERF1 KD reduces basal NHE3 activity while NHERF2 KD stimulates NHE3 activity in Caco-2/bbe cells; NHERF2 KD (but not NHERF1 KD alone) abolishes cGMP- and Ca2+-dependent inhibition of NHE3; simultaneous KD of both NHERF1 and NHERF2 is required to abolish cAMP inhibition; EGF stimulation of NHE3 is NHERF1-dependent.","method":"Lentiviral shRNA knockdown, adenoviral siRNA, NHE3 activity measurements in Caco-2/bbe cells","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — stable KD with multiple second messenger signaling conditions, clean dissection of NHERF1 vs NHERF2 roles","pmids":["21191106"],"is_preprint":false},{"year":2011,"finding":"In NHERF2-null mouse ileum, basal NHE3 activity is reduced with less NHE3 in the apical domain (more intracellular), demonstrating NHERF2 is required for normal NHE3 trafficking/retention at the apical membrane. cAMP, cGMP, elevated Ca2+ (UTP), and LPA all fail to regulate NHE3 in NHERF2-null ileum, while hyperosmolar inhibition occurs normally.","method":"Two-photon microscopy/SNARF-4F NHE3 activity, NHERF2-null mouse model, immunolocalization","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — in vivo null mouse with two-photon activity measurement and immunolocalization, mechanistic detail at step downstream of second messenger generation","pmids":["21430287"],"is_preprint":false},{"year":2011,"finding":"Under basal conditions NHERF2 and NHE3 exhibit robust FRET in opossum kidney cell microvilli. Within 1 min of elevated Ca2+ (A23187), the NHERF2-NHE3 FRET signal is abolished, microvillar NHE3 mobility transiently increases, and co-precipitation of NHE3-NHERF2 is lost; the close association is re-established by ~60 min.","method":"Acceptor photobleaching FRET, FRAP, co-precipitation in polarized opossum kidney cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — FRET + FRAP + Co-precipitation with temporal resolution, multiple orthogonal methods","pmids":["21799002"],"is_preprint":false},{"year":2012,"finding":"NHERF2 scaffolds a megalin-ClC-5 complex in proximal tubule cells: megalin interacts with NHERF2 via an internal NHERF binding domain in megalin's C-terminus and PDZ2 plus C-terminus of NHERF2; siRNA-mediated NHERF2 silencing abolishes the megalin-ClC-5 interaction, and this complex can be reconstituted with fusion proteins in vitro.","method":"GST pulldown, co-immunoprecipitation from rat kidney lysate, siRNA knockdown, in vitro reconstitution with fusion proteins","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — GST pulldown + Co-IP + siRNA KD + in vitro reconstitution, single lab","pmids":["22349218"],"is_preprint":false},{"year":2012,"finding":"CaMKIIγ constitutively binds NHE3 between aa 586-605 in the NHE3 C-terminus, phosphorylates NHE3, and inhibits basal NHE3 activity by effects on turnover number (not surface expression); this inhibition requires NHERF2. The CaMKII-NHE3 association is Ca2+-dependent (reduced when Ca2+ is elevated).","method":"CaMKII inhibitors (KN-93, KN-62), back phosphorylation, co-immunoprecipitation, NHERF2-dependent activity assays, NHE3 C-terminal deletion mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple inhibitors + mutagenesis + phosphorylation assay + NHERF2 requirement, single lab but multiple methods","pmids":["22371496"],"is_preprint":false},{"year":2012,"finding":"NHERF2 is required for ERM phosphorylation in pulmonary artery endothelial cells; NHERF2 binds all three ERM proteins, co-immunoprecipitates with Rho kinase 2, and provides a common anchoring surface for ERM and ROCK2; NHERF2 depletion prevents agonist-induced ERM phosphorylation, attenuates cell attachment, and reduces angiogenesis.","method":"Co-immunoprecipitation, siRNA knockdown, overexpression of ERM-binding mutant, ECIS cell attachment measurements, Matrigel tube formation assay","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + KD + functional binding-mutant experiments, single lab","pmids":["24364877"],"is_preprint":false},{"year":2013,"finding":"The C-terminal tail of E3KARP (NHERF2), including a nonconserved region plus the ERM-binding domain, determines its slower microvillar mobility rate (by FRAP), greater detergent insolubility, and localization to the base of microvilli (rather than along the full length like EBP50/NHERF1).","method":"FRAP/confocal microscopy in polarized epithelial cells, chimera and mutant analysis, proteomic analysis","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — FRAP with chimeric proteins defining domain, multiple orthogonal characterizations","pmids":["23985317"],"is_preprint":false},{"year":2013,"finding":"The unique C-terminal domain of NHERF2 (nonconserved region plus ERM-binding domain) determines its slow mobility rate, greater detergent insolubility, and ability to form larger multiprotein complexes; this domain is necessary for LPA stimulation of NHE3 activity/mobility and for Ca2+ ionophore-dependent inhibition of NHE3 activity.","method":"FRAP/confocal microscopy, NHERF1/NHERF2 chimeras, NHE3 activity assays in OK cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — chimeric protein analysis + FRAP + NHE3 functional assays, single lab","pmids":["23612977"],"is_preprint":false},{"year":2014,"finding":"NHERF2 and NHERF3 form the strongest heterodimerization among NHERF family members, mediated by PDZ domains of NHERF2 and the C-terminal PDZ recognition motif of NHERF3; NHERF3-4A (heterodimerization-deficient mutant) does not support carbachol inhibition of NHE3; both PDZ domains of NHERF2 can be simultaneously occupied by NHERF3 and another ligand (NHE3, α-actinin-4, or PKCα), enabling macrocomplex formation.","method":"Pulldown, co-immunoprecipitation, FRET, FRAP in Caco-2 cells, mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (pulldown, Co-IP, FRET, FRAP, mutagenesis) with functional readout","pmids":["24867958"],"is_preprint":false},{"year":2014,"finding":"LPA stimulation of NHE3 exocytosis involves an ERK-PLC-PKCδ signaling module that releases NHE3 from NHERF2: PKCδ membrane translocation is ERK- and PLC-dependent (ERK upstream of PLC); PKCδ is required for LPA-stimulated NHE3 mobility increase and NHE3/NHERF2 dissociation.","method":"NHE3 activity (BCECF/fluorometry), FRAP/confocal microscopy, kinase inhibitors, PKCδ dominant-negative studies in OK cells","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 — FRAP + functional activity assays + pharmacological pathway dissection, single lab","pmids":["24760985"],"is_preprint":false},{"year":2014,"finding":"NHERF2 acts as a coactivator of estrogen receptor α (ERα), interacting predominantly with the AF-1 domain of ERα; NHERF2 overexpression increases ERα transactivation; NHERF2 and SRC-1 synergize to increase ERα activity; NHERF2 and SRC-1 are found together with ERα on promoters of ERα target genes by ChIP.","method":"Co-immunoprecipitation, reporter assays, ChIP, proliferation assays, mouse tumor model","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + ChIP + functional reporter assay + in vivo tumor model, single lab","pmids":["24771346"],"is_preprint":false},{"year":2014,"finding":"Crystal structure of NHERF2 PDZ1 domain in complex with the C-terminal LPA2 sequence reveals the structural basis for PDZ1-LPA2 binding specificity: numerous hydrogen bonds and hydrophobic contacts with the last four LPA2 residues; conformational flexibility in the ligand-binding pocket enables broad PDZ1 substrate specificity; a small pocket adjacent to the binding site has therapeutic implications.","method":"X-ray crystallography","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with detailed molecular contacts defined","pmids":["24613836"],"is_preprint":false},{"year":2015,"finding":"NHERF2 forms a complex with Schip1 and ezrin in the cortical actin-rich regions of podocyte lamellipodia; this complex participates in actin cytoskeleton rearrangements in response to PDGF signaling.","method":"Co-immunoprecipitation, immunofluorescence, morpholino knockdown in zebrafish","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP + immunofluorescence, functional evidence from zebrafish model","pmids":["25807495"],"is_preprint":false},{"year":2015,"finding":"NHERF2 contains an ERM-binding regulatory sequence (EBRS) located 19 residues upstream of the EBD that facilitates EBD-ezrin interaction; phosphorylation of Ser303 in the EBRS decreases binding affinity for ezrin, displaces apical NHERF2 to the cytosol, increases NHERF2 microvillar mobility, and prevents acute stimulation of NHE3 by dexamethasone.","method":"FRAP, co-immunoprecipitation, phosphorylation-site mutagenesis, NHE3 activity assays in OK cells","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 — mutagenesis + FRAP + binding assays + functional NHE3 assay, multiple orthogonal methods","pmids":["26251448"],"is_preprint":false},{"year":2015,"finding":"E3KARP (NHERF2) Ser303 is phosphorylated by A-Raf in mitotic cells; S303 phosphorylation greatly enhances E3KARP exchange rate from microvilli during mitosis; S303D mutation prevents E3KARP from substituting for EBP50 in microvillus formation during interphase.","method":"FRAP, phosphorylation assays, A-Raf requirement identification, S303 mutant functional analysis in epithelial cells","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — FRAP + phosphorylation identification + functional mutant analysis, single lab","pmids":["26310448"],"is_preprint":false},{"year":2017,"finding":"NHERF2 KD and NHERF3 KO mouse jejunum both show markedly reduced LPA stimulation and UTP (elevated Ca2+) and cGMP inhibition of NHE3, while d-glucose-stimulated NHE3 activity is reduced only in NHERF2-null jejunum; these results are consistent with NHERF3 and NHERF2 acting as a heterodimer in NHE3 regulation.","method":"NHERF2 and NHERF3 knockout mice, two-photon microscopy with SNARF-4F NHE3 activity","journal":"American journal of physiology. Gastrointestinal and liver physiology","confidence":"High","confidence_rationale":"Tier 2 — in vivo parallel knockout models with direct NHE3 activity measurement, mechanistic overlap defined","pmids":["28882822"],"is_preprint":false},{"year":2019,"finding":"HPV-16 and HPV-18 E6 oncoproteins interact with NHERF-2 via their C-terminal PDZ-binding motif (PBM), resulting in proteasome-mediated degradation of NHERF-2; E6-mediated NHERF-2 degradation leads to p27 downregulation and cyclin D1 upregulation, causing accelerated cell proliferation.","method":"Co-immunoprecipitation, proteasome inhibitor experiments, siRNA/shRNA knockdown, proliferation assays in HPV-positive and HPV-negative cervical tumor cell lines","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + proteasome inhibitor + KD with functional proliferation readout, single lab","pmids":["31597772"],"is_preprint":false},{"year":2023,"finding":"NHERF2 interacts with IκB and stabilizes it by reducing its ubiquitination; SLC26A3 augments the NHERF2-IκB interaction, reducing IκB degradation and thereby inhibiting NF-κB/p65 nuclear translocation in colorectal cancer cells.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, NF-κB reporter assays","journal":"Oncogenesis","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + ubiquitination assay + functional NF-κB readout, single lab","pmids":["37573425"],"is_preprint":false},{"year":2024,"finding":"NHE3, NHERF2, and cGKII co-assemble in lipid raft-associated apical membrane microdomains (DRMs) in small intestinal brush border; NHERF2-dependent raft association of NHE3 (but not cGKII) is required for their functional proximity; after linaclotide (Gucy2c activation), NHE3 lipid raft association and microvillar abundance decrease in a cGKII-dependent manner that is strongly reduced in NHERF2-null mice.","method":"Optiprep density gradient centrifugation of brush border membranes, knockout mice, confocal microscopy, linaclotide in vivo treatment","journal":"Acta physiologica","confidence":"Medium","confidence_rationale":"Tier 2 — lipid raft fractionation with KO mice and in vivo stimulus, mechanistic macrocomplex defined","pmids":["38533975"],"is_preprint":false}],"current_model":"NHERF2 (E3KARP) is a dual-PDZ domain scaffold protein that anchors to the apical membrane cytoskeleton via its C-terminal ERM-binding domain (linked to ezrin/ROCK2), where it assembles multiprotein signaling complexes by simultaneously binding NHE3, CFTR, and GPCRs (LPA2, LPA5, P2Y1R, mGluR5, A2bR, beta2-AR) via its PDZ domains, thereby localizing kinases (PKA, PKCα, cGKII, SGK1, CaMKIIγ) near their transporter/channel substrates to mediate signal-specific regulation of ion transport (cAMP-, cGMP-, Ca2+-, LPA-, and glucocorticoid-dependent regulation of NHE3; CFTR channel activity; ROMK1 and TRPV5 membrane retention); phosphorylation of Ser303 in the NHERF2 tail by A-Raf during mitosis (or by other kinases) reduces ezrin binding and dynamically releases NHE3 from the cytoskeletal anchor to allow regulated trafficking."},"narrative":{"teleology":[{"year":1998,"claim":"The fundamental question of how cAMP-dependent kinase is positioned near NHE3 was answered by the discovery that NHERF2 directly bridges NHE3 to ezrin (a PKA type II anchoring protein) via its PDZ2 and C-terminal domains, establishing NHERF2 as a scaffolding adaptor rather than a kinase substrate.","evidence":"In vitro binding assays with domain mapping, co-IP, and co-localization in PS120 fibroblasts and opossum kidney cells","pmids":["9748260","9792717"],"confidence":"High","gaps":["Structural basis of the PDZ2–NHE3 interaction not yet defined","In vivo relevance not yet tested with knockout models"]},{"year":2000,"claim":"NHERF2's scaffolding role was extended beyond NHE3 when it was shown to bind CFTR with nanomolar affinity via PDZ2, co-localize with CFTR at the apical membrane, and potentiate cAMP-stimulated CFTR Cl⁻ currents when reconstituted with ezrin in oocytes.","evidence":"Co-IP, confocal microscopy, cell fractionation, and Xenopus oocyte electrophysiology","pmids":["10893422"],"confidence":"High","gaps":["Whether NHERF2 simultaneously scaffolds NHE3 and CFTR not tested","In vivo significance of CFTR regulation by NHERF2 not yet established"]},{"year":2001,"claim":"Signal specificity of NHERF2 scaffolding was demonstrated when glucocorticoid-induced NHE3 activation was found to require NHERF2 (not NHERF1) and SGK1, establishing that different second-messenger pathways are routed through specific scaffold–kinase combinations.","evidence":"NHE3 activity assays in PS120 and opossum kidney cells with dominant-negative SGK1","pmids":["11751930"],"confidence":"High","gaps":["Whether SGK1 directly binds PDZ domains or an adjacent region not precisely mapped","Other kinases that use NHERF2 as anchor not yet identified"]},{"year":2002,"claim":"The mechanism of Ca²⁺-dependent NHE3 inhibition was resolved: elevated Ca²⁺ induces α-actinin-4 binding to NHERF2, forming an NHE3–NHERF2–α-actinin-4 complex that drives NHE3 oligomerization and endocytosis, a process requiring NHERF2 but not NHERF1.","evidence":"NHE3 activity assays in PS120 cells, co-IP, dominant-negative overexpression, endocytosis assays","pmids":["11948184"],"confidence":"High","gaps":["How α-actinin-4 binding triggers oligomerization is unknown","Role of PKCα in the Ca²⁺ pathway not yet integrated"]},{"year":2003,"claim":"PKCα was identified as the effector kinase downstream of Ca²⁺ signaling that binds NHERF2 PDZ1 to drive NHE3 endocytosis, separating the oligomerization and endocytosis steps of Ca²⁺-dependent NHE3 inhibition.","evidence":"PKC inhibitors, GST pulldown, co-IP, surface biotinylation in PS120 cells","pmids":["12954600"],"confidence":"High","gaps":["Direct PKCα phosphorylation site on NHE3 in this context not identified","Whether PKCα and α-actinin-4 bind NHERF2 simultaneously not tested"]},{"year":2004,"claim":"NHERF2's scaffolding was extended to GPCR signaling when LPA2 receptor was shown to bind NHERF2 PDZ2, forming a ternary complex with PLC-β3 that potentiates LPA-induced ERK/COX-2 signaling, and LPA was shown to drive NHERF2-dependent exocytic trafficking of NHE3.","evidence":"Co-IP, siRNA knockdown, mutagenesis, PLC activity assays, NHE3 surface quantification with pharmacological inhibitors","pmids":["15143197","15238220"],"confidence":"High","gaps":["Whether the LPA2–NHERF2–PLC-β3 complex exists at the apical membrane in polarized epithelia not confirmed","Which kinase downstream of PLC executes NHE3 exocytosis not yet defined"]},{"year":2005,"claim":"NHERF2 was established as a cGKII-anchoring protein required for cGMP-dependent NHE3 inhibition, and simultaneously shown to scaffold P2Y1R and mGluR5 to PLC-β, prolonging receptor-mediated Ca²⁺ signaling in neurons and glia.","evidence":"NHE3 activity assays with myristoylation mutants; PDZ array, co-IP, Ca²⁺ signaling assays with point mutations in glial cells and sympathetic neurons","pmids":["15722341","15901899","16891310"],"confidence":"High","gaps":["Whether cGKII and P2Y1R/mGluR5 compete for PDZ2 occupancy not tested","NHERF2 role in neuronal signaling in vivo not confirmed"]},{"year":2009,"claim":"In vivo validation came from Nherf2-knockout mice, which showed augmented CFTR-dependent HCO₃⁻ secretion, loss of LPA-mediated inhibition of HCO₃⁻ secretion, and impaired LPA-stimulated fluid absorption via NHE3/LPA5, confirming NHERF2 as a physiologically essential scaffold for intestinal ion transport.","evidence":"Nherf2⁻/⁻ mouse duodenal secretion and intestinal absorption assays, laser microdissection/qPCR","pmids":["19221439","19800338"],"confidence":"High","gaps":["Compensatory roles of NHERF1 or NHERF3 in knockout intestine not fully dissected","Kidney phenotype of Nherf2-null mice not characterized"]},{"year":2010,"claim":"FRET and FRAP studies revealed the dynamic nature of the NHERF2–NHE3 complex: LPA stimulation causes PI3K-dependent exocytic trafficking and PI3K-independent dissociation of NHE3 from NHERF2, while Nherf2-null intestine confirmed NHERF2 tethers NHE3 near the terminal web and is required for Ca²⁺- and cGMP-dependent NHE3 inhibition.","evidence":"FRAP, acceptor photobleaching FRET, co-precipitation kinetics in OK cells; Nherf2⁻/⁻ mouse immunolocalization and NHE3 activity","pmids":["20571054","20962002"],"confidence":"High","gaps":["Identity of the kinase that phosphorylates NHE3 upon LPA to trigger dissociation from NHERF2 not defined","How NHE3–NHERF2 reassociation occurs mechanistically is unknown"]},{"year":2010,"claim":"NHERF2 was shown to determine GPCR coupling specificity in neurons, selectively reducing CaV2.2 inhibition by P2Y1R and mGluR5 while leaving α2-adrenoceptor signaling unaffected, and to direct LPA2 preferentially toward Gαq coupling and pro-migratory signaling in colon cancer cells.","evidence":"Patch-clamp electrophysiology with binding-motif mutants in sympathetic neurons; co-IP, knockdown/overexpression with migration assays in colon cancer cells","pmids":["20720114","21134377"],"confidence":"High","gaps":["Structural basis for NHERF2 selection of Gαq over Gα12 coupling unknown","In vivo neuronal phenotype of Nherf2 loss not tested"]},{"year":2012,"claim":"CaMKIIγ was identified as a constitutive NHE3-binding kinase whose basal inhibition of NHE3 turnover number requires NHERF2, adding a fourth kinase pathway (beyond PKA, SGK1, cGKII) scaffolded by NHERF2 at NHE3.","evidence":"CaMKII inhibitors, back phosphorylation, co-IP, NHE3 C-terminal deletion mutants","pmids":["22371496"],"confidence":"High","gaps":["CaMKIIγ direct phosphorylation site on NHE3 not identified","How Ca²⁺ elevation paradoxically reduces CaMKII–NHE3 association is mechanistically unclear"]},{"year":2014,"claim":"NHERF2–NHERF3 heterodimerization was found to be the strongest inter-NHERF interaction, forming macromolecular complexes where both PDZ domains of NHERF2 are simultaneously occupied; this heterodimerization is functionally required for carbachol-mediated NHE3 inhibition.","evidence":"Pulldown, co-IP, FRET, FRAP, and mutagenesis in Caco-2 cells","pmids":["24867958"],"confidence":"High","gaps":["Stoichiometry of the NHERF2–NHERF3–NHE3 macrocomplex not defined","Whether NHERF2–NHERF3 heterodimer has additional client proteins beyond NHE3 unknown"]},{"year":2015,"claim":"A key regulatory switch was identified: phosphorylation of Ser303 in the NHERF2 C-terminal ERM-binding regulatory sequence by A-Raf during mitosis reduces ezrin binding, displaces NHERF2 from microvilli to the cytosol, and prevents dexamethasone-stimulated NHE3 activation, establishing a mechanism for dynamic release of the scaffold.","evidence":"FRAP, co-IP, phosphomimetic/phosphodeficient mutants, A-Raf identification, NHE3 activity assays","pmids":["26251448","26310448"],"confidence":"High","gaps":["Other kinases that phosphorylate Ser303 outside mitosis not identified","Whether Ser303 phosphorylation also regulates CFTR or GPCR complexes not tested"]},{"year":2023,"claim":"NHERF2 was found to function beyond ion transport as a stabilizer of IκB by reducing its ubiquitination, thereby inhibiting NF-κB signaling in colorectal cancer cells, with SLC26A3 augmenting this interaction.","evidence":"Co-IP, ubiquitination assays, siRNA knockdown, NF-κB reporter assays","pmids":["37573425"],"confidence":"Medium","gaps":["Whether NHERF2 binds IκB directly via PDZ domains or indirectly is unclear","In vivo relevance to intestinal inflammation not tested in knockout mice"]},{"year":2024,"claim":"NHERF2 was shown to organize NHE3 and cGKII into lipid raft-associated apical microdomains, and linaclotide-induced cGKII-dependent removal of NHE3 from rafts is strongly reduced in NHERF2-null mice, placing NHERF2 as a determinant of microdomain organization for cGMP signaling.","evidence":"Optiprep density gradient fractionation of brush border membranes from wild-type and Nherf2⁻/⁻ mice, confocal microscopy, in vivo linaclotide treatment","pmids":["38533975"],"confidence":"Medium","gaps":["Whether NHERF2 directly targets NHE3 to lipid rafts or indirectly via ezrin is unresolved","Role of NHERF2 in raft organization for other client proteins not examined"]},{"year":null,"claim":"Full-length structural information for NHERF2 (beyond the PDZ1 crystal structure) and the atomic basis for its preferential binding hierarchy among dozens of client proteins remain unresolved; the physiological consequences of NHERF2 loss in kidney, brain, and reproductive tissues are largely untested in vivo.","evidence":"","pmids":[],"confidence":"Low","gaps":["No full-length NHERF2 structure available","Kidney and neuronal phenotypes of Nherf2-null mice not systematically characterized","How NHERF2 selects among competing PDZ ligands in vivo is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,2,5,6,10,11,14,15,37]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,3,34,35,42]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,16,26,27,35,47]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,34,41,42]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[17]}],"pathway":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[42,43]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,2,5,9,13,14,22,26,29,30]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[11,15,18,24,28,38,46]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[6,12,23,27,47]}],"complexes":["NHE3–NHERF2–ezrin","NHERF2–NHERF3 heterodimer","LPA2–NHERF2–PLC-β3"],"partners":["SLC9A3","CFTR","EZR","LPAR2","SGK1","PRKG2","PDZK1","ACTN4"],"other_free_text":[]},"mechanistic_narrative":"NHERF2 (SLC9A3R2/E3KARP) is a dual-PDZ domain scaffold protein that assembles signal-specific multiprotein complexes at the apical membrane of polarized epithelial cells and neurons, linking transmembrane ion transporters, channels, and G protein-coupled receptors to cytoskeletal anchors and kinase effectors. Its PDZ domains (especially PDZ2) bind the C-terminal motifs of NHE3, CFTR, LPA2, LPA5, P2Y1R, mGluR5, and other targets, while its C-terminal ERM-binding domain tethers these complexes to ezrin and the actin cytoskeleton, thereby positioning kinases (PKA, PKCα, cGKII, SGK1, CaMKIIγ) near their transporter substrates to mediate cAMP-, cGMP-, Ca²⁺-, LPA-, and glucocorticoid-dependent regulation of NHE3 activity, CFTR channel function, and ROMK1/TRPV5 membrane retention [PMID:9748260, PMID:15722341, PMID:21191106, PMID:20962002, PMID:19800338]. Phosphorylation of Ser303 in the NHERF2 C-terminal regulatory sequence by A-Raf during mitosis reduces ezrin binding and dynamically releases NHERF2-tethered complexes from the cytoskeleton, providing a mechanism for regulated trafficking of apical transporters [PMID:26251448, PMID:26310448]. NHERF2 also heterodimerizes with NHERF3 via PDZ-mediated interactions to form macromolecular complexes required for Ca²⁺- and cGMP-dependent NHE3 inhibition in intestinal epithelium, and functions outside the apical membrane as a coactivator of estrogen receptor α and a stabilizer of IκB that suppresses NF-κB signaling [PMID:24867958, PMID:24771346, PMID:37573425]."},"prefetch_data":{"uniprot":{"accession":"Q15599","full_name":"Na(+)/H(+) exchange regulatory cofactor NHE-RF2","aliases":["NHE3 kinase A regulatory protein E3KARP","SRY-interacting protein 1","SIP-1","Sodium-hydrogen exchanger regulatory factor 2","Solute carrier family 9 isoform A3 regulatory factor 2","Tyrosine kinase activator protein 1","TKA-1"],"length_aa":337,"mass_kda":37.4,"function":"Scaffold protein that connects plasma membrane proteins with members of the ezrin/moesin/radixin family and thereby helps to link them to the actin cytoskeleton and to regulate their surface expression. Necessary for cAMP-mediated phosphorylation and inhibition of SLC9A3 (PubMed:18829453). May also act as scaffold protein in the nucleus","subcellular_location":"Endomembrane system; Nucleus; Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/Q15599/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NHERF2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"SLC9A3R2","ensg_id":"ENSG00000065054","cell_line_id":"CID001376","localizations":[{"compartment":"vesicles","grade":3},{"compartment":"golgi","grade":2}],"interactors":[{"gene":"PODXL","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001376","total_profiled":1310},"omim":[{"mim_id":"619206","title":"SCHWANNOMIN-INTERACTING PROTEIN 1; SCHIP1","url":"https://www.omim.org/entry/619206"},{"mim_id":"607392","title":"WW DOMAIN-CONTAINING TRANSCRIPTION REGULATOR 1; WWTR1","url":"https://www.omim.org/entry/607392"},{"mim_id":"606553","title":"SOLUTE CARRIER FAMILY 9, MEMBER 3, REGULATOR 2; SLC9A3R2","url":"https://www.omim.org/entry/606553"},{"mim_id":"604990","title":"SOLUTE CARRIER FAMILY 9, MEMBER 3, REGULATOR 1; SLC9A3R1","url":"https://www.omim.org/entry/604990"},{"mim_id":"602632","title":"PODOCALYXIN-LIKE; PODXL","url":"https://www.omim.org/entry/602632"}],"hpa":{"profiled":true,"resolved_as":"SLC9A3R2","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"heart muscle","ntpm":571.9}],"url":"https://www.proteinatlas.org/search/SLC9A3R2"},"hgnc":{"alias_symbol":["SIP-1","TKA-1","NHERF-2","E3KARP","OCTS2"],"prev_symbol":["SLC9A3R2"]},"alphafold":{"accession":"Q15599","domains":[{"cath_id":"2.30.42.10","chopping":"10-111","consensus_level":"high","plddt":81.032,"start":10,"end":111},{"cath_id":"2.30.42.10","chopping":"151-250","consensus_level":"high","plddt":85.2657,"start":151,"end":250}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15599","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15599-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15599-F1-predicted_aligned_error_v6.png","plddt_mean":68.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NHERF2","jax_strain_url":"https://www.jax.org/strain/search?query=NHERF2"},"sequence":{"accession":"Q15599","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15599.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15599/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15599"}},"corpus_meta":[{"pmid":"19221439","id":"PMC_19221439","title":"Differential roles of NHERF1, NHERF2, and PDZK1 in regulating CFTR-mediated intestinal anion secretion in mice.","date":"2009","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/19221439","citation_count":303,"is_preprint":false},{"pmid":"9748260","id":"PMC_9748260","title":"NHE3 kinase A regulatory protein E3KARP binds the epithelial brush border Na+/H+ exchanger NHE3 and the cytoskeletal protein ezrin.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9748260","citation_count":244,"is_preprint":false},{"pmid":"9792717","id":"PMC_9792717","title":"The role of NHERF and E3KARP in the cAMP-mediated inhibition of NHE3.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9792717","citation_count":178,"is_preprint":false},{"pmid":"10893422","id":"PMC_10893422","title":"E3KARP mediates the association of ezrin and protein kinase A with the cystic fibrosis transmembrane conductance regulator in airway cells.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10893422","citation_count":176,"is_preprint":false},{"pmid":"15642748","id":"PMC_15642748","title":"Gp135/podocalyxin and NHERF-2 participate in the formation of a preapical domain during polarization of MDCK cells.","date":"2005","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/15642748","citation_count":165,"is_preprint":false},{"pmid":"11751930","id":"PMC_11751930","title":"Glucocorticoid activation of Na(+)/H(+) exchanger isoform 3 revisited. The roles of SGK1 and NHERF2.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11751930","citation_count":153,"is_preprint":false},{"pmid":"11948184","id":"PMC_11948184","title":"Ca(2+)-dependent inhibition of Na+/H+ exchanger 3 (NHE3) requires an NHE3-E3KARP-alpha-actinin-4 complex for oligomerization and endocytosis.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11948184","citation_count":106,"is_preprint":false},{"pmid":"12444200","id":"PMC_12444200","title":"The serum and glucocorticoid-inducible kinase SGK1 and the Na+/H+ exchange regulating factor NHERF2 synergize to stimulate the renal outer medullary K+ channel ROMK1.","date":"2002","source":"Journal of the American Society of Nephrology : JASN","url":"https://pubmed.ncbi.nlm.nih.gov/12444200","citation_count":105,"is_preprint":false},{"pmid":"11456497","id":"PMC_11456497","title":"Oligomerization of NHERF-1 and NHERF-2 PDZ domains: differential regulation by association with receptor carboxyl-termini and by phosphorylation.","date":"2001","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11456497","citation_count":99,"is_preprint":false},{"pmid":"19800338","id":"PMC_19800338","title":"Lysophosphatidic acid stimulates the intestinal brush border Na(+)/H(+) exchanger 3 and fluid absorption via LPA(5) and NHERF2.","date":"2009","source":"Gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/19800338","citation_count":95,"is_preprint":false},{"pmid":"11106646","id":"PMC_11106646","title":"Hierarchy of merlin and ezrin N- and C-terminal domain interactions in homo- and heterotypic associations and their relationship to binding of scaffolding proteins EBP50 and E3KARP.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11106646","citation_count":85,"is_preprint":false},{"pmid":"12954600","id":"PMC_12954600","title":"Ca2+-dependent inhibition of NHE3 requires PKC alpha which binds to E3KARP to decrease surface NHE3 containing plasma membrane complexes.","date":"2003","source":"American journal of physiology. 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assays, co-localization in PS120 fibroblasts, co-immunoprecipitation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding assays with domain mapping plus co-IP, replicated across two papers (PMID:9748260, PMID:9792717)\",\n      \"pmids\": [\"9748260\", \"9792717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"NHERF2 (E3KARP) is not phosphorylated by cAMP, indicating it acts as a scaffolding adapter (not a direct PKA substrate) that links NHE3 to ezrin to localize PKA type II near NHE3 for cAMP-dependent inhibition of NHE3.\",\n      \"method\": \"In vivo phosphorylation studies, co-immunoprecipitation in opossum kidney cells, cAMP analog specificity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (phosphorylation assay, Co-IP, NHE3 activity assay) in endogenous cell system\",\n      \"pmids\": [\"9792717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"NHERF2 (E3KARP) associates with CFTR preferentially via CFTR's C-terminal PDZ-binding motif and E3KARP's second PDZ domain with nanomolar affinity; E3KARP is predominantly membrane-localized and co-localizes with CFTR at the apical membrane of airway cells; co-expression of CFTR, E3KARP, and ezrin in Xenopus oocytes potentiates cAMP-stimulated CFTR Cl- currents, suggesting E3KARP scaffolds CFTR to ezrin/PKA.\",\n      \"method\": \"Co-immunoprecipitation, confocal immunofluorescence, cell fractionation, Xenopus oocyte electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, fractionation, localization, and functional reconstitution in oocytes\",\n      \"pmids\": [\"10893422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"E3KARP (NHERF2) binds tightly to the ezrin N-ERMAD but has little affinity for the merlin N-ERMAD, establishing a hierarchy of ERM-family scaffolding interactions.\",\n      \"method\": \"In vitro binding assays with recombinant proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution, single lab\",\n      \"pmids\": [\"11106646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"NHERF-2 PDZ domains associate with each other robustly in the absence of other proteins (homo-oligomerization), and NHERF-1 and NHERF-2 form homo- and hetero-oligomers in cells. NHERF-2 oligomerization is not regulated by phosphorylation (unlike NHERF-1), but may facilitate formation of signaling complexes.\",\n      \"method\": \"Biochemical PDZ domain association assays with purified proteins, co-immunoprecipitation with differentially tagged proteins\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro plus cellular Co-IP, single lab\",\n      \"pmids\": [\"11456497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Glucocorticoid (dexamethasone) activation of NHE3 requires NHERF2 (but not NHERF1) acting as a scaffold, and this activation is mediated by SGK1 interacting with the PDZ domains of NHERF2. Kinase-dead SGK1 blocked dexamethasone activation of NHE3.\",\n      \"method\": \"NHE3 activity assay in PS120 and opossum kidney cells, dominant-negative SGK1 expression, protein interaction studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional NHE3 activity assays with dominant-negative approach plus specificity for NHERF2 over NHERF1, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"11751930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Ca2+-dependent inhibition of NHE3 specifically requires E3KARP (NHERF2), not NHERF1; elevated Ca2+ induces Ca2+-dependent association between alpha-actinin-4 and E3KARP (through alpha-actinin-4's actin-binding plus spectrin repeat domain), forming an NHE3-E3KARP-alpha-actinin-4 complex that leads to NHE3 oligomerization and endocytosis.\",\n      \"method\": \"NHE3 activity assays in PS120 fibroblasts expressing E3KARP vs NHERF1, co-immunoprecipitation, dominant-negative overexpression, endocytosis assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (activity, Co-IP, dominant-negative), mechanism defined at molecular level\",\n      \"pmids\": [\"11948184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Adenosine A2b receptor co-immunoprecipitates with E3KARP (NHERF2) and ezrin upon agonist stimulation; E3KARP-ezrin interaction is enhanced by agonist stimulation, suggesting A2bR is recruited to a plasma membrane signaling complex anchored by E3KARP.\",\n      \"method\": \"Co-immunoprecipitation from T84 and Caco2-BBE cells, GFP-A2bR stable expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP with agonist stimulation condition, single lab\",\n      \"pmids\": [\"12080047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The DRA (SLC26A3) Cl-/HCO3- exchanger C-terminal ETKF motif binds specifically to the second PDZ domain of E3KARP (NHERF2) in vitro with comparable affinity to CFTR, and DRA, NHE3, and E3KARP co-localize in the apical compartment of human proximal colon, suggesting E3KARP dimerization links NHE3 and DRA.\",\n      \"method\": \"In vitro PDZ-binding assays, immunofluorescence colocalization\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding plus colocalization, single lab\",\n      \"pmids\": [\"12369822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SGK1 and NHERF2 synergize to stimulate ROMK1 K+ channel activity in Xenopus oocytes: co-expression of both (but not either alone) increases K+ channel activity and membrane abundance of ROMK1, and decreases decay of channel activity after brefeldin A treatment, indicating NHERF2 and SGK1 together enhance ROMK1 membrane retention.\",\n      \"method\": \"Xenopus oocyte electrophysiology, channel current measurements, surface abundance assays\",\n      \"journal\": \"Journal of the American Society of Nephrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional reconstitution in oocytes with mechanistic insight, single lab\",\n      \"pmids\": [\"12444200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Ca2+-dependent inhibition of NHE3 requires PKCα, which binds to the PDZ1 domain of E3KARP (NHERF2) in a Ca2+-dependent manner. PKCα and E3KARP co-immunoprecipitate from cells (enhanced by ionomycin). PKCα is necessary for Ca2+-induced decrease in surface NHE3 (endocytosis) but not for Ca2+-dependent NHE3 oligomerization.\",\n      \"method\": \"PKC inhibitor assays, GST pulldown (in vitro), co-immunoprecipitation, surface biotinylation\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vitro binding, Co-IP, functional inhibitor experiments, and surface quantification in same study\",\n      \"pmids\": [\"12954600\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"LPA2 receptor (but not other LPA receptor isoforms) specifically interacts with NHERF2 via LPA2's C-terminal PDZ-binding motif and NHERF2's second PDZ domain. NHERF2 uses its second PDZ domain to indirectly link LPA2 to PLC-β3 to form a ternary complex, potentiating LPA-induced PLC-β activation (specifically PLC-β3) and downstream ERK/COX-2 signaling.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown of NHERF2 and PLC-β3, PDZ-binding motif mutagenesis, PLC activity assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, mutagenesis, siRNA with functional readout, multiple orthogonal methods\",\n      \"pmids\": [\"15143197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"LPA induces exocytic trafficking of NHE3 to the apical membrane in an E3KARP (NHERF2)-dependent manner via activation of PLC and subsequent elevation of intracellular Ca2+; PLC inhibition and intracellular Ca2+ chelation block LPA-induced NHE3 exocytosis, whereas PKC inhibition does not.\",\n      \"method\": \"NHE3 activity assays, surface NHE3 quantification, pharmacological inhibitors of PLC/Ca2+/PKC in OK cells\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional assays with multiple pharmacological inhibitors, E3KARP-dependent mechanism, single lab\",\n      \"pmids\": [\"15238220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"NHERF2 interacts with TRPV5 via its C-tail in a Ca2+-independent manner (PDZ interaction), and NHERF2 plus SGK1 together enhance TRPV5-mediated Ca2+ entry and membrane abundance in Xenopus oocytes; the second PDZ domain of NHERF2 is required for this stimulatory effect.\",\n      \"method\": \"Xenopus oocyte electrophysiology, pull-down assays, PDZ domain deletion mutants, tracer Ca2+ uptake\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional oocyte assays with domain mutagenesis and binding assays\",\n      \"pmids\": [\"15319523\", \"15665527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NHERF2 (E3KARP) acting as a PKG-anchoring protein is required for cGMP-dependent inhibition of NHE3: NHERF2 (but not NHERF1) binds cGKII in vitro via the NHERF2 PDZ2 C-terminus, and myristoylation of cGKII is necessary for cGMP inhibition of NHE3. NHERF2 also restores cAMP inhibition of NHE3 in PS120 cells.\",\n      \"method\": \"NHE3 activity assays in PS120 cells, in vitro kinase-NHERF2 binding assays, myristoylation mutants, cGKI vs cGKII specificity\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding, functional activity assays, mutant specificity, multiple orthogonal approaches\",\n      \"pmids\": [\"15722341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"P2Y1 receptor C-terminus specifically interacts with the second PDZ domain of NHERF-2; this interaction is confirmed by Co-IP in cells and enables NHERF-2-mediated tethering of P2Y1R to PLC-β; coexpression of NHERF-2 with P2Y1R prolongs P2Y1R-mediated Ca2+ signaling in glial cells, while disruption of the P2Y1R-NHERF-2 interaction attenuates Ca2+ response duration.\",\n      \"method\": \"PDZ domain proteomic array, co-immunoprecipitation, Ca2+ signaling assays, point mutations\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — PDZ array + Co-IP + functional Ca2+ assay + mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"15901899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NHERF-2 and podocalyxin co-localize at the free surface of single MDCK cells and at a subdomain of the apical membrane during polarization; the PDZ-binding motif of podocalyxin targets it to this domain, and NHERF-2 participates in formation of an early apical scaffold via PDZ domain-mediated interactions during epithelial polarization.\",\n      \"method\": \"Domain mutant analysis, RNA interference, confocal microscopy in MDCK cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — domain mutants, RNAi, live imaging, mechanistic link to polarization\",\n      \"pmids\": [\"15642748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NHERF2 (SIP-1) interacts with SRY (sex-determining region Y protein) via the NHERF2 PDZ1 domain; mouse and human SRY both induce nuclear accumulation of NHERF2 in cultured cells, and SRY and NHERF2 are co-expressed in the nucleus of pre-Sertoli cells during testis determination.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, immunofluorescence in cultured cells and transgenic mouse model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP, nuclear co-localization in vivo, single lab\",\n      \"pmids\": [\"16166090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NHERF-2 specifically interacts with mGluR5 (but not mGluR1a) via the second PDZ domain of NHERF-2, as confirmed by co-immunoprecipitation and confocal microscopy; coexpression of NHERF-2 prolongs mGluR5-mediated Ca2+ mobilization and potentiates mGluR5-mediated cell death, effects absent with mGluR1a.\",\n      \"method\": \"PDZ domain array screen, reverse overlay, co-immunoprecipitation, confocal microscopy, Ca2+ signaling assays, point mutations\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — PDZ array + Co-IP + functional Ca2+ assays + mutagenesis + confocal, multiple orthogonal methods\",\n      \"pmids\": [\"16891310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NHE3 inhibits PKA-dependent functional expression and activation of CFTR via NHERF2 PDZ interactions; when PDZ2 of NHERF2 is deleted (or 'sequestered' by NHE3 binding), PKA-dependent CFTR apical expression and activity are inhibited, demonstrating NHERF2 mediates competitive regulation between NHE3 and CFTR.\",\n      \"method\": \"Electrophysiology, NHERF2 domain deletion transfection in A6 monolayers\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — domain deletion mutagenesis with functional readout, single lab\",\n      \"pmids\": [\"16824484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SGK1 and NHERF2 (but not NHERF1) specifically enhance PEPT2 peptide transporter function and surface abundance; the effect requires SGK1 phosphorylation at Ser185 and the C-terminal PDZ-binding motif of PEPT2; dynasore experiments show they stabilize PEPT2 at the cell surface.\",\n      \"method\": \"Xenopus oocyte electrophysiology, surface abundance immunoassays, phosphorylation-site mutagenesis, dynasore inhibition\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — oocyte functional assay, mutagenesis, surface quantification, single lab\",\n      \"pmids\": [\"19088452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NHERF2 confers inhibitory signals by coupling the LPA receptor to CFTR in duodenal crypts: Nherf2-/- mice display augmented FSK-stimulated HCO3- secretion and lose LPA-mediated inhibition of FSK-stimulated HCO3- secretion, demonstrating NHERF2 links LPA receptor to CFTR to mediate inhibition.\",\n      \"method\": \"Loss-of-function mouse models, duodenal HCO3- secretion measurements, laser microdissection/qPCR\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockout model with specific secretory phenotype, replicated alongside NHERF1/PDZK1 comparisons\",\n      \"pmids\": [\"19221439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"LPA stimulates NHE3 and intestinal fluid absorption via LPA5 receptor; this stimulation requires NHERF2 which interacts with LPA5; Nherf2-/- mice have impaired LPA-mediated fluid absorption; LPA stimulation increases NHE3 protein abundance at the brush border membrane.\",\n      \"method\": \"Wild-type and Nherf2-/- mouse intestinal absorption assays, heterologous expression studies, protein interaction assays\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockout + heterologous expression + protein interaction, multiple orthogonal methods\",\n      \"pmids\": [\"19800338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NHERF2 determines NHE3 mobility in brush borders; LPA stimulation of NHE3 requires NHERF2 and increases NHE3 mobility via two mechanisms: PI3K-dependent exocytic trafficking and PI3K-independent dissociation of NHE3 from NHERF2 (confirmed by FRET). NHE3 and NHERF2 co-precipitate under basal conditions but dissociate 30 min after LPA and reassociate by 50-60 min.\",\n      \"method\": \"FRAP, acceptor photobleaching FRET, NHE3 activity assays, co-precipitation, PI3K inhibitor studies in OK cells\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — FRAP + FRET + Co-precipitation + functional assays, multiple orthogonal methods, mechanistic dissection\",\n      \"pmids\": [\"20571054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAGI-3 competes with NHERF-2 for binding to LPA2 and PLC-β3; NHERF-2 promotes LPA2 interaction with Gαq and stimulates migration/invasion of colon cancer cells, whereas MAGI-3 promotes Gα12 coupling and inhibits these processes; the two PDZ proteins reciprocally regulate LPA2 G-protein coupling.\",\n      \"method\": \"Co-immunoprecipitation, knockdown/overexpression in HCT116/SW480 cells, migration/invasion assays, IP generation assays\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, KD/OE with defined cellular phenotypes, receptor coupling specificity defined\",\n      \"pmids\": [\"21134377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NHERF-2 co-immunoprecipitates with GLAST in astrocytes; NHERF-2 knockdown by siRNA reduces GLAST activity and total GLAST protein levels (reduced half-life in pulse-chase studies), demonstrating NHERF-2 enhances GLAST stability and activity in astrocytes.\",\n      \"method\": \"Co-immunoprecipitation from cortical astrocytes, siRNA knockdown, GLAST activity assays, pulse-chase metabolic labeling\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + siRNA KD + activity assays + pulse-chase, single lab but multiple methods\",\n      \"pmids\": [\"20430067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NHERF2 ablation in murine intestine shifts NHE3 localization from the terminal web region to microvilli; NHERF2 is required for tethering NHE3 near the terminal web and for Ca2+ ionophore- and carbachol-mediated inhibition and STp (cGMP)-dependent inhibition of NHE3; cAMP-induced NHE3 inhibition is preserved in NHERF2-null mice.\",\n      \"method\": \"NHERF2 knockout mice, immunolocalization, fluorometric NHE3 activity assays\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo knockout with multiple mechanistic readouts and segment-specific analysis\",\n      \"pmids\": [\"20962002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NHERF2 enhances apical localization of PMCA2w/b in polarized MDCK cells; NHERF2-mediated anchorage to the apical actin cytoskeleton (confirmed by colocalization with ezrin even after actin disruption) reduces PMCA2w/b internalization and lateral membrane mobility, as shown by surface biotinylation and FRAP.\",\n      \"method\": \"Confocal microscopy, surface biotinylation, FRAP in polarized MDCK cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FRAP + surface biotinylation + localization, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"20663896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NHERF2 scaffold determines ion channel coupling specificity in neurons: coexpression of NHERF2 selectively reduces CaV2.2 (N-type Ca2+ channel) inhibition by P2Y1R and mGluR5 (which bind NHERF2) but not by α2-adrenoceptors (which do not bind NHERF2), restricting downstream signaling to Gq-mediated M-current inhibition.\",\n      \"method\": \"Intranuclear cDNA injection into sympathetic neurons, whole-cell patch-clamp electrophysiology, NHERF2-binding motif mutant receptor\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional electrophysiology with binding-motif mutant control and receptor-binding specificity, rigorous design\",\n      \"pmids\": [\"20720114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NHERF1 KD reduces basal NHE3 activity while NHERF2 KD stimulates NHE3 activity in Caco-2/bbe cells; NHERF2 KD (but not NHERF1 KD alone) abolishes cGMP- and Ca2+-dependent inhibition of NHE3; simultaneous KD of both NHERF1 and NHERF2 is required to abolish cAMP inhibition; EGF stimulation of NHE3 is NHERF1-dependent.\",\n      \"method\": \"Lentiviral shRNA knockdown, adenoviral siRNA, NHE3 activity measurements in Caco-2/bbe cells\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — stable KD with multiple second messenger signaling conditions, clean dissection of NHERF1 vs NHERF2 roles\",\n      \"pmids\": [\"21191106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In NHERF2-null mouse ileum, basal NHE3 activity is reduced with less NHE3 in the apical domain (more intracellular), demonstrating NHERF2 is required for normal NHE3 trafficking/retention at the apical membrane. cAMP, cGMP, elevated Ca2+ (UTP), and LPA all fail to regulate NHE3 in NHERF2-null ileum, while hyperosmolar inhibition occurs normally.\",\n      \"method\": \"Two-photon microscopy/SNARF-4F NHE3 activity, NHERF2-null mouse model, immunolocalization\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo null mouse with two-photon activity measurement and immunolocalization, mechanistic detail at step downstream of second messenger generation\",\n      \"pmids\": [\"21430287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Under basal conditions NHERF2 and NHE3 exhibit robust FRET in opossum kidney cell microvilli. Within 1 min of elevated Ca2+ (A23187), the NHERF2-NHE3 FRET signal is abolished, microvillar NHE3 mobility transiently increases, and co-precipitation of NHE3-NHERF2 is lost; the close association is re-established by ~60 min.\",\n      \"method\": \"Acceptor photobleaching FRET, FRAP, co-precipitation in polarized opossum kidney cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — FRET + FRAP + Co-precipitation with temporal resolution, multiple orthogonal methods\",\n      \"pmids\": [\"21799002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NHERF2 scaffolds a megalin-ClC-5 complex in proximal tubule cells: megalin interacts with NHERF2 via an internal NHERF binding domain in megalin's C-terminus and PDZ2 plus C-terminus of NHERF2; siRNA-mediated NHERF2 silencing abolishes the megalin-ClC-5 interaction, and this complex can be reconstituted with fusion proteins in vitro.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation from rat kidney lysate, siRNA knockdown, in vitro reconstitution with fusion proteins\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — GST pulldown + Co-IP + siRNA KD + in vitro reconstitution, single lab\",\n      \"pmids\": [\"22349218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CaMKIIγ constitutively binds NHE3 between aa 586-605 in the NHE3 C-terminus, phosphorylates NHE3, and inhibits basal NHE3 activity by effects on turnover number (not surface expression); this inhibition requires NHERF2. The CaMKII-NHE3 association is Ca2+-dependent (reduced when Ca2+ is elevated).\",\n      \"method\": \"CaMKII inhibitors (KN-93, KN-62), back phosphorylation, co-immunoprecipitation, NHERF2-dependent activity assays, NHE3 C-terminal deletion mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple inhibitors + mutagenesis + phosphorylation assay + NHERF2 requirement, single lab but multiple methods\",\n      \"pmids\": [\"22371496\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NHERF2 is required for ERM phosphorylation in pulmonary artery endothelial cells; NHERF2 binds all three ERM proteins, co-immunoprecipitates with Rho kinase 2, and provides a common anchoring surface for ERM and ROCK2; NHERF2 depletion prevents agonist-induced ERM phosphorylation, attenuates cell attachment, and reduces angiogenesis.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, overexpression of ERM-binding mutant, ECIS cell attachment measurements, Matrigel tube formation assay\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + KD + functional binding-mutant experiments, single lab\",\n      \"pmids\": [\"24364877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The C-terminal tail of E3KARP (NHERF2), including a nonconserved region plus the ERM-binding domain, determines its slower microvillar mobility rate (by FRAP), greater detergent insolubility, and localization to the base of microvilli (rather than along the full length like EBP50/NHERF1).\",\n      \"method\": \"FRAP/confocal microscopy in polarized epithelial cells, chimera and mutant analysis, proteomic analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FRAP with chimeric proteins defining domain, multiple orthogonal characterizations\",\n      \"pmids\": [\"23985317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The unique C-terminal domain of NHERF2 (nonconserved region plus ERM-binding domain) determines its slow mobility rate, greater detergent insolubility, and ability to form larger multiprotein complexes; this domain is necessary for LPA stimulation of NHE3 activity/mobility and for Ca2+ ionophore-dependent inhibition of NHE3 activity.\",\n      \"method\": \"FRAP/confocal microscopy, NHERF1/NHERF2 chimeras, NHE3 activity assays in OK cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — chimeric protein analysis + FRAP + NHE3 functional assays, single lab\",\n      \"pmids\": [\"23612977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NHERF2 and NHERF3 form the strongest heterodimerization among NHERF family members, mediated by PDZ domains of NHERF2 and the C-terminal PDZ recognition motif of NHERF3; NHERF3-4A (heterodimerization-deficient mutant) does not support carbachol inhibition of NHE3; both PDZ domains of NHERF2 can be simultaneously occupied by NHERF3 and another ligand (NHE3, α-actinin-4, or PKCα), enabling macrocomplex formation.\",\n      \"method\": \"Pulldown, co-immunoprecipitation, FRET, FRAP in Caco-2 cells, mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (pulldown, Co-IP, FRET, FRAP, mutagenesis) with functional readout\",\n      \"pmids\": [\"24867958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"LPA stimulation of NHE3 exocytosis involves an ERK-PLC-PKCδ signaling module that releases NHE3 from NHERF2: PKCδ membrane translocation is ERK- and PLC-dependent (ERK upstream of PLC); PKCδ is required for LPA-stimulated NHE3 mobility increase and NHE3/NHERF2 dissociation.\",\n      \"method\": \"NHE3 activity (BCECF/fluorometry), FRAP/confocal microscopy, kinase inhibitors, PKCδ dominant-negative studies in OK cells\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FRAP + functional activity assays + pharmacological pathway dissection, single lab\",\n      \"pmids\": [\"24760985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NHERF2 acts as a coactivator of estrogen receptor α (ERα), interacting predominantly with the AF-1 domain of ERα; NHERF2 overexpression increases ERα transactivation; NHERF2 and SRC-1 synergize to increase ERα activity; NHERF2 and SRC-1 are found together with ERα on promoters of ERα target genes by ChIP.\",\n      \"method\": \"Co-immunoprecipitation, reporter assays, ChIP, proliferation assays, mouse tumor model\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + ChIP + functional reporter assay + in vivo tumor model, single lab\",\n      \"pmids\": [\"24771346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structure of NHERF2 PDZ1 domain in complex with the C-terminal LPA2 sequence reveals the structural basis for PDZ1-LPA2 binding specificity: numerous hydrogen bonds and hydrophobic contacts with the last four LPA2 residues; conformational flexibility in the ligand-binding pocket enables broad PDZ1 substrate specificity; a small pocket adjacent to the binding site has therapeutic implications.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with detailed molecular contacts defined\",\n      \"pmids\": [\"24613836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NHERF2 forms a complex with Schip1 and ezrin in the cortical actin-rich regions of podocyte lamellipodia; this complex participates in actin cytoskeleton rearrangements in response to PDGF signaling.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, morpholino knockdown in zebrafish\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP + immunofluorescence, functional evidence from zebrafish model\",\n      \"pmids\": [\"25807495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NHERF2 contains an ERM-binding regulatory sequence (EBRS) located 19 residues upstream of the EBD that facilitates EBD-ezrin interaction; phosphorylation of Ser303 in the EBRS decreases binding affinity for ezrin, displaces apical NHERF2 to the cytosol, increases NHERF2 microvillar mobility, and prevents acute stimulation of NHE3 by dexamethasone.\",\n      \"method\": \"FRAP, co-immunoprecipitation, phosphorylation-site mutagenesis, NHE3 activity assays in OK cells\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis + FRAP + binding assays + functional NHE3 assay, multiple orthogonal methods\",\n      \"pmids\": [\"26251448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"E3KARP (NHERF2) Ser303 is phosphorylated by A-Raf in mitotic cells; S303 phosphorylation greatly enhances E3KARP exchange rate from microvilli during mitosis; S303D mutation prevents E3KARP from substituting for EBP50 in microvillus formation during interphase.\",\n      \"method\": \"FRAP, phosphorylation assays, A-Raf requirement identification, S303 mutant functional analysis in epithelial cells\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FRAP + phosphorylation identification + functional mutant analysis, single lab\",\n      \"pmids\": [\"26310448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NHERF2 KD and NHERF3 KO mouse jejunum both show markedly reduced LPA stimulation and UTP (elevated Ca2+) and cGMP inhibition of NHE3, while d-glucose-stimulated NHE3 activity is reduced only in NHERF2-null jejunum; these results are consistent with NHERF3 and NHERF2 acting as a heterodimer in NHE3 regulation.\",\n      \"method\": \"NHERF2 and NHERF3 knockout mice, two-photon microscopy with SNARF-4F NHE3 activity\",\n      \"journal\": \"American journal of physiology. Gastrointestinal and liver physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo parallel knockout models with direct NHE3 activity measurement, mechanistic overlap defined\",\n      \"pmids\": [\"28882822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HPV-16 and HPV-18 E6 oncoproteins interact with NHERF-2 via their C-terminal PDZ-binding motif (PBM), resulting in proteasome-mediated degradation of NHERF-2; E6-mediated NHERF-2 degradation leads to p27 downregulation and cyclin D1 upregulation, causing accelerated cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, proteasome inhibitor experiments, siRNA/shRNA knockdown, proliferation assays in HPV-positive and HPV-negative cervical tumor cell lines\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + proteasome inhibitor + KD with functional proliferation readout, single lab\",\n      \"pmids\": [\"31597772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NHERF2 interacts with IκB and stabilizes it by reducing its ubiquitination; SLC26A3 augments the NHERF2-IκB interaction, reducing IκB degradation and thereby inhibiting NF-κB/p65 nuclear translocation in colorectal cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, NF-κB reporter assays\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + ubiquitination assay + functional NF-κB readout, single lab\",\n      \"pmids\": [\"37573425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NHE3, NHERF2, and cGKII co-assemble in lipid raft-associated apical membrane microdomains (DRMs) in small intestinal brush border; NHERF2-dependent raft association of NHE3 (but not cGKII) is required for their functional proximity; after linaclotide (Gucy2c activation), NHE3 lipid raft association and microvillar abundance decrease in a cGKII-dependent manner that is strongly reduced in NHERF2-null mice.\",\n      \"method\": \"Optiprep density gradient centrifugation of brush border membranes, knockout mice, confocal microscopy, linaclotide in vivo treatment\",\n      \"journal\": \"Acta physiologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — lipid raft fractionation with KO mice and in vivo stimulus, mechanistic macrocomplex defined\",\n      \"pmids\": [\"38533975\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NHERF2 (E3KARP) is a dual-PDZ domain scaffold protein that anchors to the apical membrane cytoskeleton via its C-terminal ERM-binding domain (linked to ezrin/ROCK2), where it assembles multiprotein signaling complexes by simultaneously binding NHE3, CFTR, and GPCRs (LPA2, LPA5, P2Y1R, mGluR5, A2bR, beta2-AR) via its PDZ domains, thereby localizing kinases (PKA, PKCα, cGKII, SGK1, CaMKIIγ) near their transporter/channel substrates to mediate signal-specific regulation of ion transport (cAMP-, cGMP-, Ca2+-, LPA-, and glucocorticoid-dependent regulation of NHE3; CFTR channel activity; ROMK1 and TRPV5 membrane retention); phosphorylation of Ser303 in the NHERF2 tail by A-Raf during mitosis (or by other kinases) reduces ezrin binding and dynamically releases NHE3 from the cytoskeletal anchor to allow regulated trafficking.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NHERF2 (SLC9A3R2/E3KARP) is a dual-PDZ domain scaffold protein that assembles signal-specific multiprotein complexes at the apical membrane of polarized epithelial cells and neurons, linking transmembrane ion transporters, channels, and G protein-coupled receptors to cytoskeletal anchors and kinase effectors. Its PDZ domains (especially PDZ2) bind the C-terminal motifs of NHE3, CFTR, LPA2, LPA5, P2Y1R, mGluR5, and other targets, while its C-terminal ERM-binding domain tethers these complexes to ezrin and the actin cytoskeleton, thereby positioning kinases (PKA, PKCα, cGKII, SGK1, CaMKIIγ) near their transporter substrates to mediate cAMP-, cGMP-, Ca²⁺-, LPA-, and glucocorticoid-dependent regulation of NHE3 activity, CFTR channel function, and ROMK1/TRPV5 membrane retention [PMID:9748260, PMID:15722341, PMID:21191106, PMID:20962002, PMID:19800338]. Phosphorylation of Ser303 in the NHERF2 C-terminal regulatory sequence by A-Raf during mitosis reduces ezrin binding and dynamically releases NHERF2-tethered complexes from the cytoskeleton, providing a mechanism for regulated trafficking of apical transporters [PMID:26251448, PMID:26310448]. NHERF2 also heterodimerizes with NHERF3 via PDZ-mediated interactions to form macromolecular complexes required for Ca²⁺- and cGMP-dependent NHE3 inhibition in intestinal epithelium, and functions outside the apical membrane as a coactivator of estrogen receptor α and a stabilizer of IκB that suppresses NF-κB signaling [PMID:24867958, PMID:24771346, PMID:37573425].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"The fundamental question of how cAMP-dependent kinase is positioned near NHE3 was answered by the discovery that NHERF2 directly bridges NHE3 to ezrin (a PKA type II anchoring protein) via its PDZ2 and C-terminal domains, establishing NHERF2 as a scaffolding adaptor rather than a kinase substrate.\",\n      \"evidence\": \"In vitro binding assays with domain mapping, co-IP, and co-localization in PS120 fibroblasts and opossum kidney cells\",\n      \"pmids\": [\"9748260\", \"9792717\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the PDZ2–NHE3 interaction not yet defined\", \"In vivo relevance not yet tested with knockout models\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"NHERF2's scaffolding role was extended beyond NHE3 when it was shown to bind CFTR with nanomolar affinity via PDZ2, co-localize with CFTR at the apical membrane, and potentiate cAMP-stimulated CFTR Cl⁻ currents when reconstituted with ezrin in oocytes.\",\n      \"evidence\": \"Co-IP, confocal microscopy, cell fractionation, and Xenopus oocyte electrophysiology\",\n      \"pmids\": [\"10893422\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NHERF2 simultaneously scaffolds NHE3 and CFTR not tested\", \"In vivo significance of CFTR regulation by NHERF2 not yet established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Signal specificity of NHERF2 scaffolding was demonstrated when glucocorticoid-induced NHE3 activation was found to require NHERF2 (not NHERF1) and SGK1, establishing that different second-messenger pathways are routed through specific scaffold–kinase combinations.\",\n      \"evidence\": \"NHE3 activity assays in PS120 and opossum kidney cells with dominant-negative SGK1\",\n      \"pmids\": [\"11751930\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SGK1 directly binds PDZ domains or an adjacent region not precisely mapped\", \"Other kinases that use NHERF2 as anchor not yet identified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The mechanism of Ca²⁺-dependent NHE3 inhibition was resolved: elevated Ca²⁺ induces α-actinin-4 binding to NHERF2, forming an NHE3–NHERF2–α-actinin-4 complex that drives NHE3 oligomerization and endocytosis, a process requiring NHERF2 but not NHERF1.\",\n      \"evidence\": \"NHE3 activity assays in PS120 cells, co-IP, dominant-negative overexpression, endocytosis assays\",\n      \"pmids\": [\"11948184\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How α-actinin-4 binding triggers oligomerization is unknown\", \"Role of PKCα in the Ca²⁺ pathway not yet integrated\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"PKCα was identified as the effector kinase downstream of Ca²⁺ signaling that binds NHERF2 PDZ1 to drive NHE3 endocytosis, separating the oligomerization and endocytosis steps of Ca²⁺-dependent NHE3 inhibition.\",\n      \"evidence\": \"PKC inhibitors, GST pulldown, co-IP, surface biotinylation in PS120 cells\",\n      \"pmids\": [\"12954600\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct PKCα phosphorylation site on NHE3 in this context not identified\", \"Whether PKCα and α-actinin-4 bind NHERF2 simultaneously not tested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"NHERF2's scaffolding was extended to GPCR signaling when LPA2 receptor was shown to bind NHERF2 PDZ2, forming a ternary complex with PLC-β3 that potentiates LPA-induced ERK/COX-2 signaling, and LPA was shown to drive NHERF2-dependent exocytic trafficking of NHE3.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, mutagenesis, PLC activity assays, NHE3 surface quantification with pharmacological inhibitors\",\n      \"pmids\": [\"15143197\", \"15238220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the LPA2–NHERF2–PLC-β3 complex exists at the apical membrane in polarized epithelia not confirmed\", \"Which kinase downstream of PLC executes NHE3 exocytosis not yet defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"NHERF2 was established as a cGKII-anchoring protein required for cGMP-dependent NHE3 inhibition, and simultaneously shown to scaffold P2Y1R and mGluR5 to PLC-β, prolonging receptor-mediated Ca²⁺ signaling in neurons and glia.\",\n      \"evidence\": \"NHE3 activity assays with myristoylation mutants; PDZ array, co-IP, Ca²⁺ signaling assays with point mutations in glial cells and sympathetic neurons\",\n      \"pmids\": [\"15722341\", \"15901899\", \"16891310\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cGKII and P2Y1R/mGluR5 compete for PDZ2 occupancy not tested\", \"NHERF2 role in neuronal signaling in vivo not confirmed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"In vivo validation came from Nherf2-knockout mice, which showed augmented CFTR-dependent HCO₃⁻ secretion, loss of LPA-mediated inhibition of HCO₃⁻ secretion, and impaired LPA-stimulated fluid absorption via NHE3/LPA5, confirming NHERF2 as a physiologically essential scaffold for intestinal ion transport.\",\n      \"evidence\": \"Nherf2⁻/⁻ mouse duodenal secretion and intestinal absorption assays, laser microdissection/qPCR\",\n      \"pmids\": [\"19221439\", \"19800338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Compensatory roles of NHERF1 or NHERF3 in knockout intestine not fully dissected\", \"Kidney phenotype of Nherf2-null mice not characterized\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"FRET and FRAP studies revealed the dynamic nature of the NHERF2–NHE3 complex: LPA stimulation causes PI3K-dependent exocytic trafficking and PI3K-independent dissociation of NHE3 from NHERF2, while Nherf2-null intestine confirmed NHERF2 tethers NHE3 near the terminal web and is required for Ca²⁺- and cGMP-dependent NHE3 inhibition.\",\n      \"evidence\": \"FRAP, acceptor photobleaching FRET, co-precipitation kinetics in OK cells; Nherf2⁻/⁻ mouse immunolocalization and NHE3 activity\",\n      \"pmids\": [\"20571054\", \"20962002\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the kinase that phosphorylates NHE3 upon LPA to trigger dissociation from NHERF2 not defined\", \"How NHE3–NHERF2 reassociation occurs mechanistically is unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"NHERF2 was shown to determine GPCR coupling specificity in neurons, selectively reducing CaV2.2 inhibition by P2Y1R and mGluR5 while leaving α2-adrenoceptor signaling unaffected, and to direct LPA2 preferentially toward Gαq coupling and pro-migratory signaling in colon cancer cells.\",\n      \"evidence\": \"Patch-clamp electrophysiology with binding-motif mutants in sympathetic neurons; co-IP, knockdown/overexpression with migration assays in colon cancer cells\",\n      \"pmids\": [\"20720114\", \"21134377\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for NHERF2 selection of Gαq over Gα12 coupling unknown\", \"In vivo neuronal phenotype of Nherf2 loss not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"CaMKIIγ was identified as a constitutive NHE3-binding kinase whose basal inhibition of NHE3 turnover number requires NHERF2, adding a fourth kinase pathway (beyond PKA, SGK1, cGKII) scaffolded by NHERF2 at NHE3.\",\n      \"evidence\": \"CaMKII inhibitors, back phosphorylation, co-IP, NHE3 C-terminal deletion mutants\",\n      \"pmids\": [\"22371496\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CaMKIIγ direct phosphorylation site on NHE3 not identified\", \"How Ca²⁺ elevation paradoxically reduces CaMKII–NHE3 association is mechanistically unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"NHERF2–NHERF3 heterodimerization was found to be the strongest inter-NHERF interaction, forming macromolecular complexes where both PDZ domains of NHERF2 are simultaneously occupied; this heterodimerization is functionally required for carbachol-mediated NHE3 inhibition.\",\n      \"evidence\": \"Pulldown, co-IP, FRET, FRAP, and mutagenesis in Caco-2 cells\",\n      \"pmids\": [\"24867958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the NHERF2–NHERF3–NHE3 macrocomplex not defined\", \"Whether NHERF2–NHERF3 heterodimer has additional client proteins beyond NHE3 unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"A key regulatory switch was identified: phosphorylation of Ser303 in the NHERF2 C-terminal ERM-binding regulatory sequence by A-Raf during mitosis reduces ezrin binding, displaces NHERF2 from microvilli to the cytosol, and prevents dexamethasone-stimulated NHE3 activation, establishing a mechanism for dynamic release of the scaffold.\",\n      \"evidence\": \"FRAP, co-IP, phosphomimetic/phosphodeficient mutants, A-Raf identification, NHE3 activity assays\",\n      \"pmids\": [\"26251448\", \"26310448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other kinases that phosphorylate Ser303 outside mitosis not identified\", \"Whether Ser303 phosphorylation also regulates CFTR or GPCR complexes not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"NHERF2 was found to function beyond ion transport as a stabilizer of IκB by reducing its ubiquitination, thereby inhibiting NF-κB signaling in colorectal cancer cells, with SLC26A3 augmenting this interaction.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, siRNA knockdown, NF-κB reporter assays\",\n      \"pmids\": [\"37573425\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NHERF2 binds IκB directly via PDZ domains or indirectly is unclear\", \"In vivo relevance to intestinal inflammation not tested in knockout mice\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"NHERF2 was shown to organize NHE3 and cGKII into lipid raft-associated apical microdomains, and linaclotide-induced cGKII-dependent removal of NHE3 from rafts is strongly reduced in NHERF2-null mice, placing NHERF2 as a determinant of microdomain organization for cGMP signaling.\",\n      \"evidence\": \"Optiprep density gradient fractionation of brush border membranes from wild-type and Nherf2⁻/⁻ mice, confocal microscopy, in vivo linaclotide treatment\",\n      \"pmids\": [\"38533975\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NHERF2 directly targets NHE3 to lipid rafts or indirectly via ezrin is unresolved\", \"Role of NHERF2 in raft organization for other client proteins not examined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Full-length structural information for NHERF2 (beyond the PDZ1 crystal structure) and the atomic basis for its preferential binding hierarchy among dozens of client proteins remain unresolved; the physiological consequences of NHERF2 loss in kidney, brain, and reproductive tissues are largely untested in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No full-length NHERF2 structure available\", \"Kidney and neuronal phenotypes of Nherf2-null mice not systematically characterized\", \"How NHERF2 selects among competing PDZ ligands in vivo is unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 2, 5, 6, 10, 11, 14, 15, 37]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 3, 34, 35, 42]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 16, 26, 27, 35, 47]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 34, 41, 42]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [42, 43]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 2, 5, 9, 13, 14, 22, 26, 29, 30]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [11, 15, 18, 24, 28, 38, 46]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [6, 12, 23, 27, 47]}\n    ],\n    \"complexes\": [\n      \"NHE3–NHERF2–ezrin\",\n      \"NHERF2–NHERF3 heterodimer\",\n      \"LPA2–NHERF2–PLC-β3\"\n    ],\n    \"partners\": [\n      \"SLC9A3\",\n      \"CFTR\",\n      \"EZR\",\n      \"LPAR2\",\n      \"SGK1\",\n      \"PRKG2\",\n      \"PDZK1\",\n      \"ACTN4\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}