{"gene":"TBC1D4","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2005,"finding":"The recombinant GAP domain of AS160/TBC1D4 has Rab GTPase-activating protein activity with specificity toward Rabs 2A, 8A, 10, and 14; a point mutation replacing the catalytic arginine with lysine abolishes this activity.","method":"In vitro GAP activity assay with recombinant GAP domain; active-site mutagenesis (R→K); mass spectrometry identification of Rabs on GLUT4 vesicles","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic reconstitution with mutagenesis of catalytic residue, replicated in subsequent studies","pmids":["15971998"],"is_preprint":false},{"year":2005,"finding":"AS160/TBC1D4 associates with GLUT4 vesicles in basal adipocytes and dissociates upon insulin stimulation; this association is mediated by the cytosolic tail of insulin-regulated aminopeptidase (IRAP). shRNA knockdown of AS160 increases plasma membrane GLUT4 in an insulin-independent manner, consistent with an inhibitory role in the basal state.","method":"Proteomic analysis of affinity-purified GLUT4 vesicles; in vitro and in vivo co-immunoprecipitation with IRAP; shRNA knockdown with GLUT4 surface measurement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, in vitro binding, and functional knockdown with defined phenotype; replicated by other labs","pmids":["16154996"],"is_preprint":false},{"year":2005,"finding":"AS160/TBC1D4 RabGAP activity is required for basal GLUT4 retention: knockdown increases basal GLUT4 exocytosis 3-fold, and re-expression of wild-type but not a GAP-dead mutant restores normal GLUT4 behavior.","method":"shRNA knockdown; rescue with wild-type vs. GAP-domain mutant AS160; GLUT4 exocytosis rate measurement in 3T3-L1 adipocytes","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with specific phenotypic readout, structure-function rescue with GAP mutant, replicated across labs","pmids":["16213228"],"is_preprint":false},{"year":2004,"finding":"AS160/TBC1D4 is required specifically for insulin stimulation of GLUT4 exocytosis but not for insulin-induced inhibition of GLUT4 endocytosis; a dominant-inhibitory mutant blocks exocytosis at a step before vesicle fusion with the plasma membrane.","method":"Dominant-inhibitory AS160 mutant overexpression; quantitative GLUT4 exocytosis and endocytosis assays in adipocytes","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic dissection of exo- vs. endocytosis using dominant-negative mutant, replicated in subsequent studies","pmids":["15254270"],"is_preprint":false},{"year":2006,"finding":"14-3-3 proteins interact with AS160/TBC1D4 in an insulin- and Akt-dependent manner primarily through phospho-Thr642; the AS160(T642A) mutant lacks 14-3-3 binding and blocks insulin-stimulated GLUT4 translocation; introducing a constitutive 14-3-3 binding site into AS160(4P) restores GLUT4 translocation without disrupting IRAP interaction.","method":"LC-MS/MS identification of 14-3-3 as AS160-interacting proteins; co-immunoprecipitation; site-directed mutagenesis; GLUT4 translocation assay in adipocytes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, mutagenesis of specific phosphorylation site, functional rescue experiment, multiple orthogonal methods","pmids":["16880201"],"is_preprint":false},{"year":2006,"finding":"Rab8A and Rab14 (but not Rab10) act as functional targets of AS160 in L6 muscle cells: co-expression of GFP-Rab8A or GFP-Rab14 with phosphorylation-deficient AS160 (4P) rescued GLUT4 translocation inhibited by 4P-AS160; constitutively active Rab8A also rescued.","method":"Co-expression rescue assay in L6 myoblasts expressing GLUT4myc; constitutively active and wild-type Rab overexpression","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional rescue in intact cells, single lab, two constructs tested","pmids":["17208202"],"is_preprint":false},{"year":2007,"finding":"Rab10 is a downstream effector of AS160 in adipocytes: overexpression of GTPase-deficient Rab10 increases surface GLUT4 in basal cells; Rab10 knockdown attenuates insulin-induced GLUT4 redistribution; knocking down Rab10 in AS160-knockdown cells partially blocks the basal increase in plasma membrane GLUT4.","method":"Rab10 constitutively active mutant overexpression; siRNA knockdown; double-knockdown epistasis; GLUT4 surface assay in adipocytes","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with double knockdown, gain-of-function and loss-of-function, multiple orthogonal approaches","pmids":["17403373"],"is_preprint":false},{"year":2006,"finding":"AS160 phosphorylation in skeletal muscle is regulated by at least two kinase pathways: insulin-stimulated phosphorylation requires Akt2 (blocked by wortmannin and absent in Akt2-KO mice), whereas contraction-stimulated phosphorylation is only partially reduced by Akt2 loss and is fully blocked by AICAR in AMPK-α2 transgenic mice, implicating AMPK-α2 as a distinct upstream kinase.","method":"In vivo and ex vivo phosphorylation of AS160 in Akt2-KO mice, AMPK-α2-kinase-dead transgenic mice, with wortmannin treatment; immunoblot with phospho-Akt substrate antibody","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic KO and transgenic models, replicated with pharmacological inhibitors, consistent across labs","pmids":["16804077"],"is_preprint":false},{"year":2006,"finding":"Recombinant AMPK heterotrimeric complexes (α1β1γ1 and α2β2γ1) directly phosphorylate AS160 in a cell-free assay; AICAR-stimulated AS160 phosphorylation in intact skeletal muscle requires AMPK-α2 and γ3 subunits.","method":"Cell-free phosphorylation assay with purified recombinant AMPK; AICAR treatment in AMPK-α2-KO, AMPK-α2-KD, and γ3-KO mice","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay plus multiple genetic KO models confirming the result","pmids":["16804075"],"is_preprint":false},{"year":2006,"finding":"Overexpression of phosphorylation-deficient AS160 (4P mutant) significantly inhibits both insulin- and contraction-stimulated glucose uptake in mouse skeletal muscle in vivo; this inhibition requires intact RabGAP activity, as the RabGAP-dead double mutant does not inhibit.","method":"In vivo electroporation of wild-type, 4P, R/K, and double-mutant AS160 into mouse tibialis anterior; in vivo [3H]2-deoxyglucose uptake after insulin or contraction","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo loss-of-function/structure-function with defined phenotypic readout, multiple mutant constructs, replicated by other groups","pmids":["16935857"],"is_preprint":false},{"year":2007,"finding":"AS160 contains a calmodulin-binding domain (CBD) that is required specifically for contraction-stimulated (but not insulin-stimulated) glucose uptake in mouse skeletal muscle; CBD mutation impairs contraction-stimulated glucose uptake, and this effect is rescued by also mutating the RabGAP domain (R/K), implying calmodulin regulates AS160 RabGAP activity during contraction.","method":"In vivo electroporation of CBD-mutant AS160; immunoprecipitation with biotinylated calmodulin; in vivo glucose uptake measurement","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — structure-function mutagenesis in vivo with defined functional readout and mechanistic rescue experiment","pmids":["17717281"],"is_preprint":false},{"year":2007,"finding":"Eight residues on AS160 (Ser318, Ser341, Thr568, Ser570, Ser588, Thr642, Ser666, Ser751) are differentially phosphorylated in response to IGF-1, EGF, PMA, and AICAR; 14-3-3 binding requires primarily Thr642, and is abolished by Thr642Ala/Ser341Ala double mutation; RSK1, SGK1, and PKB each display distinct phosphorylation signatures on AS160 in vitro.","method":"14-3-3 affinity chromatography; mass spectrometry phosphosite mapping; in vitro kinase assays with RSK1, SGK1, PKB, AMPK; mutagenesis of phosphorylation sites","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assays with multiple purified kinases, mass spectrometry site mapping, mutagenesis validation","pmids":["17617058"],"is_preprint":false},{"year":2008,"finding":"AS160 phosphorylation by Akt, conventional/novel PKC, and AMPK-α2 converges to regulate GLUT4 translocation; nonphosphorylatable AS160 (4P) blocks GLUT4 translocation induced by insulin, PDGF, K+ depolarization, and AICAR, but not hypertonicity or 2,4-DNP; GAP-inactive AS160 mutants have no inhibitory effect.","method":"Overexpression of 4P-AS160, RK-AS160, and 4PRK-AS160 mutants in CHO-IR and muscle cells; quantification of surface GLUT4myc with various stimuli","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — structure-function with multiple mutants and stimuli, consistent mechanistic interpretation","pmids":["17259386"],"is_preprint":false},{"year":2006,"finding":"AS160/TBC1D4 interacts with the amino terminus of IRAP through its second phosphotyrosine-binding (PTB) domain; this interaction is not regulated by AS160 phosphorylation; co-localization confirmed by confocal microscopy.","method":"Co-immunoprecipitation of overexpressed and endogenous proteins; confocal microscopy; domain mapping with PTB constructs","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP of endogenous proteins, domain mapping, replicated in independent studies","pmids":["16762977"],"is_preprint":false},{"year":2008,"finding":"The membrane association of TBC1D4/AS160 with GLUT4-containing membranes is required for its inhibitory action on GLUT4 translocation under basal conditions; insulin-dependent dissociation from membranes is not required for GLUT4 translocation, but phosphorylation of TBC1D4 at T642 is essential.","method":"Subcellular fractionation; overexpression of phosphorylation and membrane-targeting mutants; GLUT4 translocation assay in adipocytes","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple mutant constructs, fractionation, functional readout; single lab","pmids":["18801932"],"is_preprint":false},{"year":2009,"finding":"A novel phosphorylation site, Ser711, on TBC1D4/AS160 is phosphorylated by AMPK (but not Akt1, Akt2, or PKCζ) in vitro; AICAR and contraction increase Ser711 phosphorylation in mouse skeletal muscle in an AMPK-α2-dependent manner; however, S711A mutation does not alter glucose uptake.","method":"Mass spectrometry phosphosite identification; in vitro kinase assay with purified recombinant AMPK, Akt1, Akt2, PKCζ; phosphospecific antibody; AMPK-α2 kinase-dead transgenic mice; S711A mutant glucose uptake assay","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase reconstitution with multiple kinases, genetic mouse model confirmation, mutagenesis functional test","pmids":["19923418"],"is_preprint":false},{"year":2011,"finding":"Knockin mutation of AS160-Thr649Ala (equivalent to human Thr642) in mice abolishes insulin-stimulated AS160 binding to 14-3-3 proteins, impairs glucose disposal and insulin sensitivity, and reduces insulin-stimulated glucose transport and cell surface GLUT4 in isolated muscles (but not adipocytes), providing genetic evidence that Thr649 phosphorylation is required for insulin action in muscle.","method":"Knockin mouse generation (Thr649Ala); hyperinsulinemic-euglycemic clamp; isolated muscle glucose transport assay; GLUT4 surface measurement; 14-3-3 co-immunoprecipitation","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic knockin with multiple orthogonal physiological readouts","pmids":["21195350"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of the RabGAP domains of human TBC1D4 (AS160) and TBC1D1 were solved at 3.5 Å and 2.2 Å resolution, respectively; both contain 16 α-helices and no β-sheets; alanine-scanning mutagenesis identified key residues (including Met930 in TBC1D1) required for catalytic activity and GLUT4 translocation.","method":"X-ray crystallography; alanine-scanning mutagenesis of predicted Rab-binding interface; GLUT4 translocation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mutagenesis and functional validation in GLUT4 translocation assay","pmids":["21454505"],"is_preprint":false},{"year":2012,"finding":"The second PTB domain of TBC1D4/AS160 contains a phospholipid-binding domain that facilitates plasma membrane targeting; a distinct non-overlapping region within this domain binds intracellular GLUT4-containing storage vesicles (GSVs). The interaction with GSVs (not plasma membrane) confers the inhibitory effect on GLUT4 translocation; constitutive targeting of AS160 to the plasma membrane increases surface GLUT4 by enhancing AS160 phosphorylation, 14-3-3 binding, and inhibiting GAP activity.","method":"Mutagenesis of phospholipid-binding domain; subcellular targeting constructs; GLUT4 translocation assay; phospholipid-binding assay; co-immunoprecipitation in adipocytes","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — structure-function mutagenesis of multiple domains with functional readout, multiple orthogonal methods","pmids":["23045393"],"is_preprint":false},{"year":2014,"finding":"Rab8a acts as a downstream effector of AS160 in a ternary complex with Fsp27 to positively regulate lipid droplet (LD) fusion in adipocytes; GDP-bound (not GTP-bound) Rab8a exhibits fusion-promoting activity; AS160 is the GAP for Rab8a; MSS4 antagonizes Fsp27-mediated LD fusion through Rab8a.","method":"Co-immunoprecipitation; shRNA knockdown of Rab8a in ob/ob mouse livers; overexpression studies; LD fusion assay in adipocytes","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP, in vivo knockdown, gain/loss-of-function, defined molecular complex","pmids":["25158853"],"is_preprint":false},{"year":2012,"finding":"AS160 mediates insulin- and AMPK-stimulated surface translocation of CD36 in cardiomyocytes through Rab8a; AS160 knockdown redistributes CD36 to the surface and abrogates stimulated recruitment; phosphorylation-deficient AS160 (4P) suppresses stimulated CD36 membrane recruitment; Rab8a overexpression and knockdown specifically modulates insulin/AICAR-induced CD36 translocation.","method":"AS160 and Rab8a knockdown and overexpression in cardiomyocytes; CD36 surface measurement; GLUT4 and CD36 translocation assays","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function and gain-of-function with two substrates (GLUT4 and CD36), multiple orthogonal approaches","pmids":["22315395"],"is_preprint":false},{"year":2014,"finding":"Combined deletion of TBC1D1 and TBC1D4 in mice (D1/4KO) almost completely abolishes insulin-stimulated glucose uptake in muscle and adipose cells, with substantially reduced GLUT4 protein levels; single knockouts show only partial impairment, indicating non-redundant but overlapping roles.","method":"Double knockout (Tbc1d1/Tbc1d4 KO) mouse; euglycemic-hyperinsulinemic clamp; isolated muscle and adipocyte glucose uptake; GLUT4 protein quantification; cell surface GLUT4 labeling","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic double-KO epistasis with multiple physiological readouts","pmids":["25249576"],"is_preprint":false},{"year":2016,"finding":"The RabGAP activity of AS160 is specifically required to maintain GLUT4 protein levels in a cell/tissue-autonomous manner; the RabGAP-inactive AS160(R917K) knockin mouse phenocopies the AS160-KO, and inhibition of lysosomal function restores GLUT4 protein levels, indicating that loss of AS160 RabGAP activity promotes lysosomal degradation of GLUT4.","method":"Muscle-specific AS160 KO; RabGAP-inactive AS160(R917K) knockin mouse; lysosome inhibition rescue; GLUT4 protein measurement","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent genetic models (KO and knockin), pharmacological rescue, clear molecular mechanism","pmids":["27554475"],"is_preprint":false},{"year":2021,"finding":"Full-length TBC1D4 forms oligomers of ~600 kDa and has markedly higher specific GAP activity toward Rab10 compared with the truncated GAP domain alone; AKT phosphorylates TBC1D4 preferentially at Ser324 and Thr649, while AMPK preferentially phosphorylates Ser348, Ser577, Ser595, Ser711, and Ser764; phosphorylation by AKT or AMPK does not alter intrinsic RabGAP activity but disrupts interaction with IRAP, suggesting phosphorylation regulates TBC1D4 vesicle recruitment rather than catalytic activity.","method":"Baculovirus-expressed recombinant full-length TBC1D4; size-exclusion chromatography; co-immunoprecipitation; high-resolution mass spectrometry; Michaelis-Menten kinetics with stable isotope-labeled γ-[18O4]-ATP; in vitro phosphorylation assays with purified AKT and AMPK","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with full-length protein, mass spectrometry site mapping, kinetic assays, multiple purified kinases","pmids":["33872597"],"is_preprint":false},{"year":2007,"finding":"AS160 phosphorylation is required for the docking step of GLUT4 storage vesicles (GSVs) at the plasma membrane; quantitative dual-color fluorescence assay revealed that a dominant-negative AS160 mutant proportionally inhibits both docking and fusion of GSVs, indicating AS160 acts at or before docking but not in the regulation of GSV fusion after docking.","method":"Novel dual-color fluorescent GLUT4 probe; single-vesicle fusion assay; dominant-negative AS160 mutant overexpression in 3T3-L1 adipocytes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — novel quantitative assay, single lab, functional dissection of trafficking step","pmids":["18063571"],"is_preprint":false},{"year":2008,"finding":"GLUT4 vesicle recruitment to the cell periphery requires Rac/actin dynamics, while AS160 phosphorylation (acting through Rab8A) is essential for vesicle docking/fusion; selective Rab8A knockdown magnifies the effect of non-phosphorylatable AS160 (4P) on blocking GLUT4 insertion, placing Rab8A downstream of AS160.","method":"Dominant-negative Rac; latrunculin B actin disruption; tetanus toxin VAMP2 cleavage; non-phosphorylatable AS160-4P; selective Rab8A siRNA knockdown; GLUT4myc insertion assay in L6 myoblasts","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal perturbations with defined sub-steps, epistasis established by double perturbation","pmids":["18650435"],"is_preprint":false},{"year":2010,"finding":"AS160 directly interacts with the NP domain of the Na+,K+-ATPase α-subunit; AS160 coexpression causes intracellular retention of the sodium pump; AMPK-dependent phosphorylation of AS160 regulates Na+,K+-ATPase cell surface expression, as AMPK inhibition-induced endocytosis of the pump is prevented by AS160 shRNA knockdown.","method":"Co-immunoprecipitation; co-expression in COS cells; domain mapping; shRNA knockdown; pharmacological AMPK inhibition (Compound C); Na+,K+-ATPase surface expression assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated by co-IP with domain mapping, functional epistasis with knockdown; single lab","pmids":["20943949"],"is_preprint":false},{"year":2010,"finding":"Aldosterone increases AS160 expression and induces AS160 phosphorylation predominantly at SGK1 sites (Thr568 and Ser751), promoting AS160 interaction with 14-3-3β and ε; AS160 stabilizes ENaC in intracellular compartments under basal conditions, and aldosterone/SGK1-dependent AS160 phosphorylation permits ENaC forward trafficking to the apical membrane.","method":"AS160 overexpression and knockdown in cortical collecting duct epithelial cells; 14-3-3 co-immunoprecipitation; mutagenesis of SGK1 phospho-sites; amiloride-sensitive Na+ current measurement; apical membrane biotinylation","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss- and gain-of-function with site-directed mutagenesis of phosphorylation sites and defined electrophysiological readout","pmids":["20410134"],"is_preprint":false},{"year":2011,"finding":"AS160 knockdown in 3T3-L1 adipocytes releases GLUT4 from intracellular retention into the actively cycling pool without changing the exocytosis rate constant (kex) or endocytosis rate constant (ken); Akt regulates kex through an AS160-independent mechanism, indicating AS160 controls GLUT4 vesicle tethering/docking/fusion through Rab GTP-hydrolysis, while a separate Akt substrate regulates the final fusion step.","method":"Kinetic modeling of GLUT4 trafficking; shRNA knockdown; PI3K/Akt inhibitor treatments; mathematical modeling","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinetic dissection with multiple inhibitors, single lab, mathematical modeling to support mechanistic interpretation","pmids":["21613213"],"is_preprint":false},{"year":2009,"finding":"Cytoplasmic RIP140 (exported from the nucleus after PKCε phosphorylation and arginine methylation) interacts directly with AS160 to impede AS160 phosphorylation by Akt, thereby reducing GLUT4 trafficking and glucose uptake in adipocytes; this pathway is activated in epididymal adipocytes of diet-induced obese mice.","method":"Co-immunoprecipitation; AS160 phosphorylation assay; GLUT4 translocation assay; in vivo diet-induced obesity model","journal":"Cell metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with functional consequence on AS160 phosphorylation and GLUT4 trafficking; single lab","pmids":["19945409"],"is_preprint":false},{"year":2007,"finding":"Rip11 forms a protein complex with AS160 in a Rab11-independent manner in adipocytes; insulin induces dissociation of AS160 from Rip11; Rip11 knockdown inhibits insulin-stimulated glucose uptake, and Rip11 overexpression blocks insertion of translocated GLUT4 vesicles into the plasma membrane.","method":"Co-immunoprecipitation; siRNA knockdown; Rip11 overexpression; GLUT4 vesicle insertion assay; 2-deoxyglucose uptake in 3T3-L1 adipocytes","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with defined functional readout; single lab, moderate mechanistic follow-up","pmids":["18003705"],"is_preprint":false},{"year":2009,"finding":"RUVBL2 is a novel AS160-binding protein identified by tandem affinity purification/mass spectrometry; depletion of RUVBL2 in 3T3-L1 adipocytes inhibits insulin-stimulated GLUT4 translocation and glucose uptake by reducing insulin-stimulated AS160 phosphorylation; re-introduction of human RUVBL2 reverses the inhibitory effect.","method":"Mammalian TAP combined with mass spectrometry; siRNA knockdown; rescue re-expression; GLUT4 translocation assay","journal":"Cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS identification of interactor with functional validation by knockdown and rescue; single lab","pmids":["19532121"],"is_preprint":false},{"year":2012,"finding":"ClipR-59 interacts directly with AS160 through its ankyrin repeats; this interaction is required for ClipR-59 to promote AS160 phosphorylation and GLUT4 membrane translocation; ClipR-59 functions as a scaffold facilitating Akt-mediated AS160 phosphorylation.","method":"Co-immunoprecipitation; ankyrin-repeat deletion mutant (ΔANK); GLUT4 translocation assay; glucose transport measurement in 3T3-L1 adipocytes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mapping by mutagenesis, co-IP, functional readout; single lab","pmids":["22689584"],"is_preprint":false},{"year":2011,"finding":"AS160 knockdown in mouse cortical collecting duct cells (mpkCCDc14) increases AQP2 density at the plasma membrane in the absence of dDAVP stimulation; phosphorylation of AS160 is dependent on PI3K/Akt pathway (Akt1 knockdown reduces phospho-AS160); these findings suggest AS160 RabGAP activity restrains AQP2 trafficking to the plasma membrane.","method":"siRNA knockdown of AS160 and Akt1; immunocytochemistry; cell surface biotinylation; dDAVP stimulation in M-1 and mpkCCDc14 cells","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown with surface quantification and Akt pathway dependence; single lab","pmids":["21511697"],"is_preprint":false},{"year":2010,"finding":"WNK1 phosphorylates TBC1D4 in vitro, forms a protein complex with TBC1D4 in HEK293 cells, increases TBC1D4 binding to 14-3-3 proteins, reduces TBC1D4 interaction with Rab8A, and regulates cell surface expression of GLUT1; these effects require WNK1 catalytic activity.","method":"Co-immunoprecipitation; in vitro phosphorylation by WNK1; kinase-dead mutant; GLUT1 surface expression assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus co-IP and functional readout; single lab","pmids":["20937822"],"is_preprint":false},{"year":2019,"finding":"WNK1 phosphorylates TBC1D4 at Ser704 (identified by mass spectrometry); WNK1 knockdown decreases plasma membrane GLUT1 and glucose uptake; phosphomimetic and unphosphorylatable Ser704 mutants of TBC1D4 each affect cell surface GLUT1 abundance.","method":"RNA interference of WNK1; mass spectrometry phosphosite identification; phosphomimetic and alanine substitution mutants; GLUT1 surface quantification","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS phosphosite identification, knockdown, and mutagenesis with functional readout; single lab","pmids":["31816312"],"is_preprint":false},{"year":2017,"finding":"FKBP51 forms a novel physical association with AS160; FKBP51 antagonism (SAFit2) or genetic deletion increases AS160 phosphorylation and enhances GLUT4 surface expression and glucose uptake in skeletal myotubes, placing FKBP51 as a negative regulator upstream of the AKT2-AS160 axis.","method":"Co-immunoprecipitation; phosphorylation immunoblot; GLUT4 surface assay; FKBP51 KO mice; SAFit2 pharmacological treatment","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus genetic KO and pharmacological inhibition with functional readout; single lab","pmids":["29170369"],"is_preprint":false},{"year":2016,"finding":"Rab28 is a substrate for the GAP domains of both TBC1D4 and TBC1D1 in vitro; Rab28 GTP-binding state is acutely regulated by insulin in vivo; Rab28 siRNA knockdown decreases basal glucose uptake in skeletal muscle, and constitutively active Rab28 increases basal GLUT4 surface levels in adipocytes.","method":"In vitro GAP activity assay; GTP-binding measurement; siRNA knockdown in isolated muscle; constitutively active Rab28-Q72L overexpression","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro substrate identification confirmed by in vivo loss/gain-of-function; single lab","pmids":["27929607"],"is_preprint":false},{"year":2016,"finding":"AS160 knockdown causes blunted cell proliferation and G1 phase arrest in multiple cell lines in a glucose-independent manner; this is mediated by upregulation of the CDK inhibitor p21; AS160 overexpression downregulates p21 and rescues arrested cell cycle; p21 knockdown rescues the proliferation defect caused by AS160 depletion.","method":"shRNA knockdown in fibroblasts and cancer cells; cell cycle analysis; p21 immunoblot; AS160 overexpression rescue; p21 siRNA double knockdown","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function, overexpression rescue, and epistatic double knockdown; single lab","pmids":["27152871"],"is_preprint":false},{"year":2018,"finding":"AS160 (TBC1D4) acts as the Rab14 GAP within Chlamydia trachomatis-infected cells; bacterial infection induces Akt phosphorylation and phosphorylation/inactivation of AS160 at the inclusion membrane, thereby maintaining Rab14 in the GTP-bound state to facilitate sphingolipid delivery to chlamydial inclusions; Akt inhibition prevents AS160 phosphorylation, reduces Rab14 at inclusions, and impairs bacterial replication.","method":"Pharmacological Akt inhibition; AS160 siRNA knockdown; immunofluorescence; electron microscopy; sphingolipid trafficking assay","journal":"Frontiers in microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with two independent approaches (inhibitor and siRNA) and defined trafficking readout; single lab","pmids":["31001235"],"is_preprint":false},{"year":2016,"finding":"AS160 phosphorylation on Ser588 and Thr642 is regulated by PP1-α: PP1-α co-immunoprecipitates with AS160 (not PP1-β, PP1-γ1, or PP2A); recombinant PP1 inhibitor-2 delays AS160 dephosphorylation; PP1-α siRNA knockdown increases AS160 phosphorylation on both sites without altering Akt phosphorylation.","method":"Co-immunoprecipitation of PP1 isoforms with AS160; pharmacological phosphatase inhibitor treatment; recombinant inhibitor-2 protein; PP1-α/β/γ1 siRNA knockdown; phosphospecific immunoblot","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP of endogenous proteins, domain-specific inhibitor, and isoform-specific siRNA all converging on same finding","pmids":["27246912"],"is_preprint":false},{"year":2023,"finding":"TBC1D4-Ser711 phosphorylation by AMPK mediates the insulin-sensitizing effect of exercise on skeletal muscle glucose uptake: TBC1D4-S711A knockin mice show normal contraction-stimulated glucose uptake but lack the post-exercise/contraction enhancement of insulin sensitivity observed in wild-type mice; enhanced TBC1D4-S711 phosphorylation occurs concomitantly with improved insulin sensitivity after exercise.","method":"TBC1D4-S711A knockin mouse; in vitro contraction; hyperinsulinemic-euglycemic clamp; glucose uptake measurement; AMPK activity assay; phosphospecific immunoblot","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic knockin with defined physiological phenotype and mechanistic specificity","pmids":["37074686"],"is_preprint":false},{"year":2018,"finding":"In cells co-expressing both TBC1D4 and TBC1D1, Tbc1d1 functionally dominates AS160/TBC1D4, and GLUT4 release relies on Tbc1d1-evoking proximal stimuli (AICAR, Ca2+); AS160 modulates sensitivity to stimuli in Tbc1d1-mediated GLUT4 release; cooperative actions require the PTB1 and calmodulin-binding domains of Tbc1d1 and phosphorylation sites on both AS160 (Thr642) and Tbc1d1 (Ser237, Thr596).","method":"GLUT4 nanometry; cell-based reconstitution; varying expression ratios; mutational analyses of multiple domains and phosphorylation sites","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional reconstitution with multiple mutants; single lab","pmids":["30482843"],"is_preprint":false},{"year":2022,"finding":"AS160 expression is essential for post-exercise enhancement of insulin-stimulated glucose uptake (ISGU) in skeletal muscle: AS160-KO rats lack post-exercise improvement in ISGU; AAV-mediated rescue of AS160 in AS160-KO muscle restores this enhancement; AAV-delivered GLUT4 alone does not rescue; AS160 mutated at Ser588/Thr642/Ser704 only partially restores the post-exercise effect.","method":"AS160-KO rat model; AAV-mediated gene delivery of wild-type or phosphomutant AS160 and GLUT4; isolated muscle glucose uptake assay post-exercise","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple AAV rescue experiments providing mechanistic dissection, in vivo exercise model","pmids":["34753801"],"is_preprint":false},{"year":2008,"finding":"AS160 is expressed in pancreatic beta-cells and phosphorylated after glucose stimulation via insulin receptor/IRS-2/PI3K/Akt, independently of cytosolic Ca2+; AS160 knockdown in MIN6B1 beta-cells increases basal insulin secretion, abolishes glucose-stimulated insulin release, increases apoptosis, and eliminates glucose-induced proliferation.","method":"shRNA knockdown and siRNA in MIN6B1 and primary mouse islet cells; AS160 phosphorylation immunoblot; insulin secretion assay; apoptosis measurement","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-specific knockdown with multiple phenotypic readouts; single lab","pmids":["18276765"],"is_preprint":false}],"current_model":"TBC1D4/AS160 is a Rab GTPase-activating protein (with GAP activity established in vitro against Rabs 2A, 8A, 10, 14, and 28) that resides on GLUT4 storage vesicles via its PTB2 domain interaction with IRAP, where it maintains GLUT4 intracellular retention by keeping target Rabs in the GDP-bound inactive state; insulin activates Akt2 (and additionally RSK1/SGK1) to phosphorylate multiple sites including the critical Thr649 (human Thr642), triggering 14-3-3 binding that disrupts IRAP interaction and releases the inhibitory constraint on Rab10/Rab8A, thereby enabling GLUT4 vesicle docking and fusion with the plasma membrane; exercise/contraction-stimulated AMPK additionally phosphorylates Ser711 (a key site for post-exercise insulin sensitization) and other sites; the RabGAP activity also maintains GLUT4 protein levels by preventing lysosomal degradation; AS160 additionally regulates trafficking of CD36, Na+/K+-ATPase, ENaC, and AQP2 through analogous phospho-regulated Rab-GAP mechanisms, and controls cell proliferation through p21."},"narrative":{"mechanistic_narrative":"TBC1D4 (AS160) is a Rab GTPase-activating protein that serves as the central insulin- and contraction-responsive brake on regulated GLUT4 vesicle trafficking, coupling kinase signaling to membrane fusion [PMID:15971998, PMID:16213228]. Its recombinant GAP domain hydrolyzes GTP on Rabs 2A, 8A, 10, and 14, an activity destroyed by mutation of the catalytic arginine, and crystallography defines an all-α-helical Rab-binding fold whose interface residues are required for catalysis and GLUT4 translocation [PMID:15971998, PMID:21454505]. In the basal state TBC1D4 docks onto GLUT4 storage vesicles through its second PTB domain, which binds the cytosolic tail of IRAP and, via a distinct phospholipid-binding region, mediates vesicle versus plasma-membrane targeting; this membrane association keeps target Rabs (notably Rab8A and Rab10) GDP-bound and retains GLUT4 intracellularly, since knockdown or GAP-dead rescue releases GLUT4 to the surface [PMID:16154996, PMID:16762977, PMID:23045393, PMID:17403373, PMID:18650435]. Insulin drives Akt2 to phosphorylate the critical Thr642 (mouse Thr649), recruiting 14-3-3 and disrupting the IRAP/membrane interaction, thereby relieving the Rab brake to permit GLUT4 vesicle docking and fusion; knockin of the non-phosphorylatable Thr649Ala allele impairs muscle glucose disposal in vivo [PMID:16880201, PMID:21195350, PMID:18801932, PMID:18063571]. A parallel contraction/exercise pathway uses AMPK-α2, which directly phosphorylates TBC1D4 including Ser711, the site required for post-exercise insulin sensitization but dispensable for acute contraction-stimulated uptake [PMID:16804077, PMID:16804075, PMID:19923418, PMID:37074686, PMID:34753801]. Phosphorylation regulates vesicle recruitment rather than intrinsic catalysis, as full-length oligomeric TBC1D4 retains GAP activity after Akt or AMPK phosphorylation while losing IRAP binding [PMID:33872597]. Beyond acute trafficking, the GAP activity maintains GLUT4 protein abundance by preventing its lysosomal degradation, and combined loss of TBC1D4 and TBC1D1 abolishes insulin-stimulated glucose uptake in muscle and fat [PMID:27554475, PMID:25249576]. The same phospho-regulated Rab-GAP logic governs trafficking of additional cargoes including CD36, the Na+/K+-ATPase, ENaC, and AQP2, and TBC1D4 further restrains cell proliferation through p21 [PMID:22315395, PMID:20943949, PMID:20410134, PMID:21511697, PMID:27152871].","teleology":[{"year":2005,"claim":"Established that AS160/TBC1D4 is an enzyme with defined Rab-GAP activity and a catalytic arginine, identifying its biochemical mechanism of action.","evidence":"In vitro GAP assay with recombinant GAP domain and catalytic arginine-to-lysine mutagenesis, plus MS of GLUT4-vesicle Rabs","pmids":["15971998"],"confidence":"High","gaps":["In vitro Rab specificity did not establish which Rabs are physiological in-cell targets","No structure of the catalytic domain at this stage"]},{"year":2005,"claim":"Showed that AS160 physically docks on GLUT4 vesicles via IRAP and acts as a basal-state inhibitor, explaining how a cytosolic GAP is targeted to its trafficking compartment.","evidence":"GLUT4-vesicle proteomics, reciprocal IRAP co-IP, and shRNA knockdown with GLUT4 surface measurement in adipocytes","pmids":["16154996","16213228"],"confidence":"High","gaps":["Did not identify the downstream Rab effector relieved upon dissociation","Mechanism linking GAP activity to retention not yet resolved"]},{"year":2004,"claim":"Localized AS160 action to the GLUT4 exocytic limb, specifically before vesicle fusion, distinguishing it from endocytic regulation.","evidence":"Dominant-inhibitory AS160 mutant with quantitative exo/endocytosis assays in adipocytes","pmids":["15254270"],"confidence":"High","gaps":["Did not pinpoint docking versus fusion sub-step","No molecular identity of the blocked Rab"]},{"year":2006,"claim":"Defined the insulin-input mechanism: Akt-dependent phosphorylation at Thr642 creates a 14-3-3 binding site that relieves inhibition, and dual kinase inputs (Akt2 for insulin, AMPK-α2 for contraction) converge on AS160.","evidence":"LC-MS/MS 14-3-3 capture, phosphosite mutagenesis, GLUT4 translocation assays, plus Akt2-KO and AMPK transgenic mouse phosphorylation studies and cell-free AMPK kinase assays","pmids":["16880201","16804077","16804075","16762977"],"confidence":"High","gaps":["Whether 14-3-3 binding alters GAP catalysis or only localization was unresolved","Functional Rab targets relieved by phosphorylation not yet defined in cells"]},{"year":2007,"claim":"Identified the in-cell Rab effectors (Rab8A, Rab10, Rab14) downstream of AS160, converting in vitro substrates into a physiological pathway and placing Rab8A downstream of AS160 phosphorylation.","evidence":"Constitutively active/dominant Rab rescue and siRNA epistasis in L6 and adipocytes, with Rac/actin and VAMP2 perturbations dissecting trafficking steps","pmids":["17208202","17403373","18650435","18063571"],"confidence":"High","gaps":["Cell-type-specific dominance of Rab8A versus Rab10 not fully reconciled","Docking versus fusion contributions of individual Rabs not separated"]},{"year":2007,"claim":"Mapped the multi-site phospho-code and additional regulatory domains, showing distinct kinases (RSK1, SGK1, PKB, AMPK) and a calmodulin-binding domain selectively gating contraction responses.","evidence":"MS phosphosite mapping, in vitro kinase assays with multiple kinases, and in vivo CBD-mutant electroporation with glucose uptake","pmids":["17617058","16935857","17717281","17259386"],"confidence":"High","gaps":["Functional consequence of most individual sites beyond Thr642 unresolved","How calmodulin modulates GAP activity mechanistically not defined"]},{"year":2008,"claim":"Refined the targeting logic: membrane/GSV association via the PTB2 region confers the basal inhibitory effect, separating localization from catalysis.","evidence":"Subcellular fractionation and membrane-targeting/phosphomutant constructs in adipocytes","pmids":["18801932","23045393"],"confidence":"High","gaps":["Whether dissociation per se is dispensable versus phosphorylation remained debated across constructs","Lipid identity driving membrane binding not fully defined"]},{"year":2011,"claim":"Provided in vivo genetic and structural proof that Thr649 phosphorylation and the GAP fold are required for muscle insulin action.","evidence":"Thr649Ala knockin mice with hyperinsulinemic-euglycemic clamp and muscle glucose transport, plus X-ray crystallography of the GAP domain with mutagenesis","pmids":["21195350","21454505"],"confidence":"High","gaps":["Tissue divergence (muscle versus adipocyte phenotype) mechanism unexplained","Full-length protein architecture beyond GAP domain unknown"]},{"year":2016,"claim":"Showed a second, slower function of GAP activity: maintaining GLUT4 protein levels by preventing lysosomal degradation, and demonstrated genetic redundancy with TBC1D1.","evidence":"RabGAP-inactive R917K knockin and muscle-specific KO with lysosome-inhibition rescue, plus Tbc1d1/Tbc1d4 double-KO clamp studies","pmids":["27554475","25249576"],"confidence":"High","gaps":["Which Rab(s) route GLUT4 to lysosomes not identified","Division of labor between TBC1D1 and TBC1D4 substrates incompletely resolved"]},{"year":2021,"claim":"Resolved the long-standing question of whether phosphorylation regulates catalysis versus recruitment, showing full-length oligomeric TBC1D4 retains GAP activity but loses IRAP binding upon Akt/AMPK phosphorylation.","evidence":"Baculovirus full-length protein, size-exclusion chromatography, Michaelis-Menten kinetics with isotope-labeled ATP, MS site mapping, and co-IP","pmids":["33872597"],"confidence":"High","gaps":["Structural basis of oligomerization not determined","How recruitment loss translates to Rab activation in vivo not directly visualized"]},{"year":2023,"claim":"Defined the molecular basis of exercise-induced insulin sensitization, attributing it specifically to AMPK phosphorylation of Ser711.","evidence":"TBC1D4-S711A knockin mice with contraction protocols and hyperinsulinemic-euglycemic clamps, plus the earlier AS160-KO rat AAV rescue series","pmids":["37074686","34753801","19923418"],"confidence":"High","gaps":["Downstream effector linking Ser711 to sustained sensitization unknown","Whether human Ser711-equivalent behaves identically not addressed"]},{"year":2018,"claim":"Generalized the TBC1D4 mechanism to other cargoes and contexts, showing analogous phospho-regulated Rab-GAP control of CD36, Na+/K+-ATPase, ENaC, AQP2, GLUT1, lipid droplet fusion, cell proliferation, and even pathogen-driven trafficking.","evidence":"Knockdown/overexpression, domain mapping, phosphosite mutagenesis, and trafficking/electrophysiology readouts across cardiomyocytes, kidney epithelia, adipocytes, beta-cells, cancer cells, and Chlamydia-infected cells","pmids":["22315395","20943949","20410134","21511697","20937822","31816312","25158853","27152871","31001235","18276765"],"confidence":"Medium","gaps":["Most non-GLUT4 cargoes shown in single labs without in vivo genetic confirmation","Shared versus cargo-specific Rab effectors not systematically mapped"]},{"year":null,"claim":"How the network of upstream regulators (PP1-α, FKBP51, RIP140, RUVBL2, ClipR-59, WNK1, Rip11) integrates with the core Akt/AMPK–14-3-3 axis to set GAP activity quantitatively in different tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model of phospho-input integration","Most regulators validated in single cell systems without genetic in vivo data","Structural basis of full-length regulation incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,17,23]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[18]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,13]}],"localization":[{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[1,13,18]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1,23]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[18]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,7,16]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,3,24]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[20,26,27]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[9,21,22]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[38]}],"complexes":[],"partners":["IRAP","RAB10","RAB8A","RAB14","AKT2","PRKAA2","YWHAB","WNK1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60343","full_name":"TBC1 domain family member 4","aliases":["Akt substrate of 160 kDa","AS160"],"length_aa":1298,"mass_kda":146.6,"function":"May act as a GTPase-activating protein for RAB2A, RAB8A, RAB10 and RAB14. Isoform 2 promotes insulin-induced glucose transporter SLC2A4/GLUT4 translocation at the plasma membrane, thus increasing glucose uptake","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O60343/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TBC1D4","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ACTR2","stoichiometry":0.2},{"gene":"ANKRD27","stoichiometry":0.2},{"gene":"ARL8B","stoichiometry":0.2},{"gene":"CALM1","stoichiometry":0.2},{"gene":"CALM2","stoichiometry":0.2},{"gene":"CALM3","stoichiometry":0.2},{"gene":"MIS12","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/TBC1D4","total_profiled":1310},"omim":[{"mim_id":"616087","title":"TYPE 2 DIABETES 5; T2D5","url":"https://www.omim.org/entry/616087"},{"mim_id":"612673","title":"RAS-ASSOCIATED PROTEIN RAB14; RAB14","url":"https://www.omim.org/entry/612673"},{"mim_id":"612672","title":"RAS-ASSOCIATED PROTEIN RAB10; RAB10","url":"https://www.omim.org/entry/612672"},{"mim_id":"612465","title":"TBC1 DOMAIN FAMILY, MEMBER 4; TBC1D4","url":"https://www.omim.org/entry/612465"},{"mim_id":"610549","title":"DIABETES MELLITUS, INSULIN-RESISTANT, WITH ACANTHOSIS NIGRICANS","url":"https://www.omim.org/entry/610549"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Cytosol","reliability":"Enhanced"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skeletal muscle","ntpm":77.5}],"url":"https://www.proteinatlas.org/search/TBC1D4"},"hgnc":{"alias_symbol":["KIAA0603","AS160","DKFZp779C0666"],"prev_symbol":[]},"alphafold":{"accession":"O60343","domains":[{"cath_id":"2.30.29.30","chopping":"34-70_77-98_116-189","consensus_level":"medium","plddt":80.1872,"start":34,"end":189},{"cath_id":"2.30.29.30","chopping":"201-238_345-448","consensus_level":"high","plddt":80.4154,"start":201,"end":448},{"cath_id":"-","chopping":"451-529","consensus_level":"medium","plddt":86.2056,"start":451,"end":529}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60343","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60343-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60343-F1-predicted_aligned_error_v6.png","plddt_mean":66.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TBC1D4","jax_strain_url":"https://www.jax.org/strain/search?query=TBC1D4"},"sequence":{"accession":"O60343","fasta_url":"https://rest.uniprot.org/uniprotkb/O60343.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60343/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60343"}},"corpus_meta":[{"pmid":"18477703","id":"PMC_18477703","title":"Emerging role for AS160/TBC1D4 and TBC1D1 in the regulation of GLUT4 traffic.","date":"2008","source":"American journal of physiology. 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a point mutation replacing the catalytic arginine with lysine abolishes this activity.\",\n      \"method\": \"In vitro GAP activity assay with recombinant GAP domain; active-site mutagenesis (R→K); mass spectrometry identification of Rabs on GLUT4 vesicles\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic reconstitution with mutagenesis of catalytic residue, replicated in subsequent studies\",\n      \"pmids\": [\"15971998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"AS160/TBC1D4 associates with GLUT4 vesicles in basal adipocytes and dissociates upon insulin stimulation; this association is mediated by the cytosolic tail of insulin-regulated aminopeptidase (IRAP). shRNA knockdown of AS160 increases plasma membrane GLUT4 in an insulin-independent manner, consistent with an inhibitory role in the basal state.\",\n      \"method\": \"Proteomic analysis of affinity-purified GLUT4 vesicles; in vitro and in vivo co-immunoprecipitation with IRAP; shRNA knockdown with GLUT4 surface measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, in vitro binding, and functional knockdown with defined phenotype; replicated by other labs\",\n      \"pmids\": [\"16154996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"AS160/TBC1D4 RabGAP activity is required for basal GLUT4 retention: knockdown increases basal GLUT4 exocytosis 3-fold, and re-expression of wild-type but not a GAP-dead mutant restores normal GLUT4 behavior.\",\n      \"method\": \"shRNA knockdown; rescue with wild-type vs. GAP-domain mutant AS160; GLUT4 exocytosis rate measurement in 3T3-L1 adipocytes\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with specific phenotypic readout, structure-function rescue with GAP mutant, replicated across labs\",\n      \"pmids\": [\"16213228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"AS160/TBC1D4 is required specifically for insulin stimulation of GLUT4 exocytosis but not for insulin-induced inhibition of GLUT4 endocytosis; a dominant-inhibitory mutant blocks exocytosis at a step before vesicle fusion with the plasma membrane.\",\n      \"method\": \"Dominant-inhibitory AS160 mutant overexpression; quantitative GLUT4 exocytosis and endocytosis assays in adipocytes\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic dissection of exo- vs. endocytosis using dominant-negative mutant, replicated in subsequent studies\",\n      \"pmids\": [\"15254270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"14-3-3 proteins interact with AS160/TBC1D4 in an insulin- and Akt-dependent manner primarily through phospho-Thr642; the AS160(T642A) mutant lacks 14-3-3 binding and blocks insulin-stimulated GLUT4 translocation; introducing a constitutive 14-3-3 binding site into AS160(4P) restores GLUT4 translocation without disrupting IRAP interaction.\",\n      \"method\": \"LC-MS/MS identification of 14-3-3 as AS160-interacting proteins; co-immunoprecipitation; site-directed mutagenesis; GLUT4 translocation assay in adipocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, mutagenesis of specific phosphorylation site, functional rescue experiment, multiple orthogonal methods\",\n      \"pmids\": [\"16880201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Rab8A and Rab14 (but not Rab10) act as functional targets of AS160 in L6 muscle cells: co-expression of GFP-Rab8A or GFP-Rab14 with phosphorylation-deficient AS160 (4P) rescued GLUT4 translocation inhibited by 4P-AS160; constitutively active Rab8A also rescued.\",\n      \"method\": \"Co-expression rescue assay in L6 myoblasts expressing GLUT4myc; constitutively active and wild-type Rab overexpression\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue in intact cells, single lab, two constructs tested\",\n      \"pmids\": [\"17208202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rab10 is a downstream effector of AS160 in adipocytes: overexpression of GTPase-deficient Rab10 increases surface GLUT4 in basal cells; Rab10 knockdown attenuates insulin-induced GLUT4 redistribution; knocking down Rab10 in AS160-knockdown cells partially blocks the basal increase in plasma membrane GLUT4.\",\n      \"method\": \"Rab10 constitutively active mutant overexpression; siRNA knockdown; double-knockdown epistasis; GLUT4 surface assay in adipocytes\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with double knockdown, gain-of-function and loss-of-function, multiple orthogonal approaches\",\n      \"pmids\": [\"17403373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"AS160 phosphorylation in skeletal muscle is regulated by at least two kinase pathways: insulin-stimulated phosphorylation requires Akt2 (blocked by wortmannin and absent in Akt2-KO mice), whereas contraction-stimulated phosphorylation is only partially reduced by Akt2 loss and is fully blocked by AICAR in AMPK-α2 transgenic mice, implicating AMPK-α2 as a distinct upstream kinase.\",\n      \"method\": \"In vivo and ex vivo phosphorylation of AS160 in Akt2-KO mice, AMPK-α2-kinase-dead transgenic mice, with wortmannin treatment; immunoblot with phospho-Akt substrate antibody\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic KO and transgenic models, replicated with pharmacological inhibitors, consistent across labs\",\n      \"pmids\": [\"16804077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Recombinant AMPK heterotrimeric complexes (α1β1γ1 and α2β2γ1) directly phosphorylate AS160 in a cell-free assay; AICAR-stimulated AS160 phosphorylation in intact skeletal muscle requires AMPK-α2 and γ3 subunits.\",\n      \"method\": \"Cell-free phosphorylation assay with purified recombinant AMPK; AICAR treatment in AMPK-α2-KO, AMPK-α2-KD, and γ3-KO mice\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay plus multiple genetic KO models confirming the result\",\n      \"pmids\": [\"16804075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Overexpression of phosphorylation-deficient AS160 (4P mutant) significantly inhibits both insulin- and contraction-stimulated glucose uptake in mouse skeletal muscle in vivo; this inhibition requires intact RabGAP activity, as the RabGAP-dead double mutant does not inhibit.\",\n      \"method\": \"In vivo electroporation of wild-type, 4P, R/K, and double-mutant AS160 into mouse tibialis anterior; in vivo [3H]2-deoxyglucose uptake after insulin or contraction\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo loss-of-function/structure-function with defined phenotypic readout, multiple mutant constructs, replicated by other groups\",\n      \"pmids\": [\"16935857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AS160 contains a calmodulin-binding domain (CBD) that is required specifically for contraction-stimulated (but not insulin-stimulated) glucose uptake in mouse skeletal muscle; CBD mutation impairs contraction-stimulated glucose uptake, and this effect is rescued by also mutating the RabGAP domain (R/K), implying calmodulin regulates AS160 RabGAP activity during contraction.\",\n      \"method\": \"In vivo electroporation of CBD-mutant AS160; immunoprecipitation with biotinylated calmodulin; in vivo glucose uptake measurement\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — structure-function mutagenesis in vivo with defined functional readout and mechanistic rescue experiment\",\n      \"pmids\": [\"17717281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Eight residues on AS160 (Ser318, Ser341, Thr568, Ser570, Ser588, Thr642, Ser666, Ser751) are differentially phosphorylated in response to IGF-1, EGF, PMA, and AICAR; 14-3-3 binding requires primarily Thr642, and is abolished by Thr642Ala/Ser341Ala double mutation; RSK1, SGK1, and PKB each display distinct phosphorylation signatures on AS160 in vitro.\",\n      \"method\": \"14-3-3 affinity chromatography; mass spectrometry phosphosite mapping; in vitro kinase assays with RSK1, SGK1, PKB, AMPK; mutagenesis of phosphorylation sites\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assays with multiple purified kinases, mass spectrometry site mapping, mutagenesis validation\",\n      \"pmids\": [\"17617058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AS160 phosphorylation by Akt, conventional/novel PKC, and AMPK-α2 converges to regulate GLUT4 translocation; nonphosphorylatable AS160 (4P) blocks GLUT4 translocation induced by insulin, PDGF, K+ depolarization, and AICAR, but not hypertonicity or 2,4-DNP; GAP-inactive AS160 mutants have no inhibitory effect.\",\n      \"method\": \"Overexpression of 4P-AS160, RK-AS160, and 4PRK-AS160 mutants in CHO-IR and muscle cells; quantification of surface GLUT4myc with various stimuli\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — structure-function with multiple mutants and stimuli, consistent mechanistic interpretation\",\n      \"pmids\": [\"17259386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"AS160/TBC1D4 interacts with the amino terminus of IRAP through its second phosphotyrosine-binding (PTB) domain; this interaction is not regulated by AS160 phosphorylation; co-localization confirmed by confocal microscopy.\",\n      \"method\": \"Co-immunoprecipitation of overexpressed and endogenous proteins; confocal microscopy; domain mapping with PTB constructs\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP of endogenous proteins, domain mapping, replicated in independent studies\",\n      \"pmids\": [\"16762977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The membrane association of TBC1D4/AS160 with GLUT4-containing membranes is required for its inhibitory action on GLUT4 translocation under basal conditions; insulin-dependent dissociation from membranes is not required for GLUT4 translocation, but phosphorylation of TBC1D4 at T642 is essential.\",\n      \"method\": \"Subcellular fractionation; overexpression of phosphorylation and membrane-targeting mutants; GLUT4 translocation assay in adipocytes\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mutant constructs, fractionation, functional readout; single lab\",\n      \"pmids\": [\"18801932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"A novel phosphorylation site, Ser711, on TBC1D4/AS160 is phosphorylated by AMPK (but not Akt1, Akt2, or PKCζ) in vitro; AICAR and contraction increase Ser711 phosphorylation in mouse skeletal muscle in an AMPK-α2-dependent manner; however, S711A mutation does not alter glucose uptake.\",\n      \"method\": \"Mass spectrometry phosphosite identification; in vitro kinase assay with purified recombinant AMPK, Akt1, Akt2, PKCζ; phosphospecific antibody; AMPK-α2 kinase-dead transgenic mice; S711A mutant glucose uptake assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase reconstitution with multiple kinases, genetic mouse model confirmation, mutagenesis functional test\",\n      \"pmids\": [\"19923418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Knockin mutation of AS160-Thr649Ala (equivalent to human Thr642) in mice abolishes insulin-stimulated AS160 binding to 14-3-3 proteins, impairs glucose disposal and insulin sensitivity, and reduces insulin-stimulated glucose transport and cell surface GLUT4 in isolated muscles (but not adipocytes), providing genetic evidence that Thr649 phosphorylation is required for insulin action in muscle.\",\n      \"method\": \"Knockin mouse generation (Thr649Ala); hyperinsulinemic-euglycemic clamp; isolated muscle glucose transport assay; GLUT4 surface measurement; 14-3-3 co-immunoprecipitation\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic knockin with multiple orthogonal physiological readouts\",\n      \"pmids\": [\"21195350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of the RabGAP domains of human TBC1D4 (AS160) and TBC1D1 were solved at 3.5 Å and 2.2 Å resolution, respectively; both contain 16 α-helices and no β-sheets; alanine-scanning mutagenesis identified key residues (including Met930 in TBC1D1) required for catalytic activity and GLUT4 translocation.\",\n      \"method\": \"X-ray crystallography; alanine-scanning mutagenesis of predicted Rab-binding interface; GLUT4 translocation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mutagenesis and functional validation in GLUT4 translocation assay\",\n      \"pmids\": [\"21454505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The second PTB domain of TBC1D4/AS160 contains a phospholipid-binding domain that facilitates plasma membrane targeting; a distinct non-overlapping region within this domain binds intracellular GLUT4-containing storage vesicles (GSVs). The interaction with GSVs (not plasma membrane) confers the inhibitory effect on GLUT4 translocation; constitutive targeting of AS160 to the plasma membrane increases surface GLUT4 by enhancing AS160 phosphorylation, 14-3-3 binding, and inhibiting GAP activity.\",\n      \"method\": \"Mutagenesis of phospholipid-binding domain; subcellular targeting constructs; GLUT4 translocation assay; phospholipid-binding assay; co-immunoprecipitation in adipocytes\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — structure-function mutagenesis of multiple domains with functional readout, multiple orthogonal methods\",\n      \"pmids\": [\"23045393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Rab8a acts as a downstream effector of AS160 in a ternary complex with Fsp27 to positively regulate lipid droplet (LD) fusion in adipocytes; GDP-bound (not GTP-bound) Rab8a exhibits fusion-promoting activity; AS160 is the GAP for Rab8a; MSS4 antagonizes Fsp27-mediated LD fusion through Rab8a.\",\n      \"method\": \"Co-immunoprecipitation; shRNA knockdown of Rab8a in ob/ob mouse livers; overexpression studies; LD fusion assay in adipocytes\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP, in vivo knockdown, gain/loss-of-function, defined molecular complex\",\n      \"pmids\": [\"25158853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"AS160 mediates insulin- and AMPK-stimulated surface translocation of CD36 in cardiomyocytes through Rab8a; AS160 knockdown redistributes CD36 to the surface and abrogates stimulated recruitment; phosphorylation-deficient AS160 (4P) suppresses stimulated CD36 membrane recruitment; Rab8a overexpression and knockdown specifically modulates insulin/AICAR-induced CD36 translocation.\",\n      \"method\": \"AS160 and Rab8a knockdown and overexpression in cardiomyocytes; CD36 surface measurement; GLUT4 and CD36 translocation assays\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function and gain-of-function with two substrates (GLUT4 and CD36), multiple orthogonal approaches\",\n      \"pmids\": [\"22315395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Combined deletion of TBC1D1 and TBC1D4 in mice (D1/4KO) almost completely abolishes insulin-stimulated glucose uptake in muscle and adipose cells, with substantially reduced GLUT4 protein levels; single knockouts show only partial impairment, indicating non-redundant but overlapping roles.\",\n      \"method\": \"Double knockout (Tbc1d1/Tbc1d4 KO) mouse; euglycemic-hyperinsulinemic clamp; isolated muscle and adipocyte glucose uptake; GLUT4 protein quantification; cell surface GLUT4 labeling\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic double-KO epistasis with multiple physiological readouts\",\n      \"pmids\": [\"25249576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The RabGAP activity of AS160 is specifically required to maintain GLUT4 protein levels in a cell/tissue-autonomous manner; the RabGAP-inactive AS160(R917K) knockin mouse phenocopies the AS160-KO, and inhibition of lysosomal function restores GLUT4 protein levels, indicating that loss of AS160 RabGAP activity promotes lysosomal degradation of GLUT4.\",\n      \"method\": \"Muscle-specific AS160 KO; RabGAP-inactive AS160(R917K) knockin mouse; lysosome inhibition rescue; GLUT4 protein measurement\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent genetic models (KO and knockin), pharmacological rescue, clear molecular mechanism\",\n      \"pmids\": [\"27554475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Full-length TBC1D4 forms oligomers of ~600 kDa and has markedly higher specific GAP activity toward Rab10 compared with the truncated GAP domain alone; AKT phosphorylates TBC1D4 preferentially at Ser324 and Thr649, while AMPK preferentially phosphorylates Ser348, Ser577, Ser595, Ser711, and Ser764; phosphorylation by AKT or AMPK does not alter intrinsic RabGAP activity but disrupts interaction with IRAP, suggesting phosphorylation regulates TBC1D4 vesicle recruitment rather than catalytic activity.\",\n      \"method\": \"Baculovirus-expressed recombinant full-length TBC1D4; size-exclusion chromatography; co-immunoprecipitation; high-resolution mass spectrometry; Michaelis-Menten kinetics with stable isotope-labeled γ-[18O4]-ATP; in vitro phosphorylation assays with purified AKT and AMPK\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with full-length protein, mass spectrometry site mapping, kinetic assays, multiple purified kinases\",\n      \"pmids\": [\"33872597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AS160 phosphorylation is required for the docking step of GLUT4 storage vesicles (GSVs) at the plasma membrane; quantitative dual-color fluorescence assay revealed that a dominant-negative AS160 mutant proportionally inhibits both docking and fusion of GSVs, indicating AS160 acts at or before docking but not in the regulation of GSV fusion after docking.\",\n      \"method\": \"Novel dual-color fluorescent GLUT4 probe; single-vesicle fusion assay; dominant-negative AS160 mutant overexpression in 3T3-L1 adipocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel quantitative assay, single lab, functional dissection of trafficking step\",\n      \"pmids\": [\"18063571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GLUT4 vesicle recruitment to the cell periphery requires Rac/actin dynamics, while AS160 phosphorylation (acting through Rab8A) is essential for vesicle docking/fusion; selective Rab8A knockdown magnifies the effect of non-phosphorylatable AS160 (4P) on blocking GLUT4 insertion, placing Rab8A downstream of AS160.\",\n      \"method\": \"Dominant-negative Rac; latrunculin B actin disruption; tetanus toxin VAMP2 cleavage; non-phosphorylatable AS160-4P; selective Rab8A siRNA knockdown; GLUT4myc insertion assay in L6 myoblasts\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal perturbations with defined sub-steps, epistasis established by double perturbation\",\n      \"pmids\": [\"18650435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AS160 directly interacts with the NP domain of the Na+,K+-ATPase α-subunit; AS160 coexpression causes intracellular retention of the sodium pump; AMPK-dependent phosphorylation of AS160 regulates Na+,K+-ATPase cell surface expression, as AMPK inhibition-induced endocytosis of the pump is prevented by AS160 shRNA knockdown.\",\n      \"method\": \"Co-immunoprecipitation; co-expression in COS cells; domain mapping; shRNA knockdown; pharmacological AMPK inhibition (Compound C); Na+,K+-ATPase surface expression assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated by co-IP with domain mapping, functional epistasis with knockdown; single lab\",\n      \"pmids\": [\"20943949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Aldosterone increases AS160 expression and induces AS160 phosphorylation predominantly at SGK1 sites (Thr568 and Ser751), promoting AS160 interaction with 14-3-3β and ε; AS160 stabilizes ENaC in intracellular compartments under basal conditions, and aldosterone/SGK1-dependent AS160 phosphorylation permits ENaC forward trafficking to the apical membrane.\",\n      \"method\": \"AS160 overexpression and knockdown in cortical collecting duct epithelial cells; 14-3-3 co-immunoprecipitation; mutagenesis of SGK1 phospho-sites; amiloride-sensitive Na+ current measurement; apical membrane biotinylation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss- and gain-of-function with site-directed mutagenesis of phosphorylation sites and defined electrophysiological readout\",\n      \"pmids\": [\"20410134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AS160 knockdown in 3T3-L1 adipocytes releases GLUT4 from intracellular retention into the actively cycling pool without changing the exocytosis rate constant (kex) or endocytosis rate constant (ken); Akt regulates kex through an AS160-independent mechanism, indicating AS160 controls GLUT4 vesicle tethering/docking/fusion through Rab GTP-hydrolysis, while a separate Akt substrate regulates the final fusion step.\",\n      \"method\": \"Kinetic modeling of GLUT4 trafficking; shRNA knockdown; PI3K/Akt inhibitor treatments; mathematical modeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinetic dissection with multiple inhibitors, single lab, mathematical modeling to support mechanistic interpretation\",\n      \"pmids\": [\"21613213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cytoplasmic RIP140 (exported from the nucleus after PKCε phosphorylation and arginine methylation) interacts directly with AS160 to impede AS160 phosphorylation by Akt, thereby reducing GLUT4 trafficking and glucose uptake in adipocytes; this pathway is activated in epididymal adipocytes of diet-induced obese mice.\",\n      \"method\": \"Co-immunoprecipitation; AS160 phosphorylation assay; GLUT4 translocation assay; in vivo diet-induced obesity model\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with functional consequence on AS160 phosphorylation and GLUT4 trafficking; single lab\",\n      \"pmids\": [\"19945409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rip11 forms a protein complex with AS160 in a Rab11-independent manner in adipocytes; insulin induces dissociation of AS160 from Rip11; Rip11 knockdown inhibits insulin-stimulated glucose uptake, and Rip11 overexpression blocks insertion of translocated GLUT4 vesicles into the plasma membrane.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; Rip11 overexpression; GLUT4 vesicle insertion assay; 2-deoxyglucose uptake in 3T3-L1 adipocytes\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with defined functional readout; single lab, moderate mechanistic follow-up\",\n      \"pmids\": [\"18003705\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RUVBL2 is a novel AS160-binding protein identified by tandem affinity purification/mass spectrometry; depletion of RUVBL2 in 3T3-L1 adipocytes inhibits insulin-stimulated GLUT4 translocation and glucose uptake by reducing insulin-stimulated AS160 phosphorylation; re-introduction of human RUVBL2 reverses the inhibitory effect.\",\n      \"method\": \"Mammalian TAP combined with mass spectrometry; siRNA knockdown; rescue re-expression; GLUT4 translocation assay\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification of interactor with functional validation by knockdown and rescue; single lab\",\n      \"pmids\": [\"19532121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ClipR-59 interacts directly with AS160 through its ankyrin repeats; this interaction is required for ClipR-59 to promote AS160 phosphorylation and GLUT4 membrane translocation; ClipR-59 functions as a scaffold facilitating Akt-mediated AS160 phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation; ankyrin-repeat deletion mutant (ΔANK); GLUT4 translocation assay; glucose transport measurement in 3T3-L1 adipocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mapping by mutagenesis, co-IP, functional readout; single lab\",\n      \"pmids\": [\"22689584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AS160 knockdown in mouse cortical collecting duct cells (mpkCCDc14) increases AQP2 density at the plasma membrane in the absence of dDAVP stimulation; phosphorylation of AS160 is dependent on PI3K/Akt pathway (Akt1 knockdown reduces phospho-AS160); these findings suggest AS160 RabGAP activity restrains AQP2 trafficking to the plasma membrane.\",\n      \"method\": \"siRNA knockdown of AS160 and Akt1; immunocytochemistry; cell surface biotinylation; dDAVP stimulation in M-1 and mpkCCDc14 cells\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown with surface quantification and Akt pathway dependence; single lab\",\n      \"pmids\": [\"21511697\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"WNK1 phosphorylates TBC1D4 in vitro, forms a protein complex with TBC1D4 in HEK293 cells, increases TBC1D4 binding to 14-3-3 proteins, reduces TBC1D4 interaction with Rab8A, and regulates cell surface expression of GLUT1; these effects require WNK1 catalytic activity.\",\n      \"method\": \"Co-immunoprecipitation; in vitro phosphorylation by WNK1; kinase-dead mutant; GLUT1 surface expression assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus co-IP and functional readout; single lab\",\n      \"pmids\": [\"20937822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"WNK1 phosphorylates TBC1D4 at Ser704 (identified by mass spectrometry); WNK1 knockdown decreases plasma membrane GLUT1 and glucose uptake; phosphomimetic and unphosphorylatable Ser704 mutants of TBC1D4 each affect cell surface GLUT1 abundance.\",\n      \"method\": \"RNA interference of WNK1; mass spectrometry phosphosite identification; phosphomimetic and alanine substitution mutants; GLUT1 surface quantification\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS phosphosite identification, knockdown, and mutagenesis with functional readout; single lab\",\n      \"pmids\": [\"31816312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FKBP51 forms a novel physical association with AS160; FKBP51 antagonism (SAFit2) or genetic deletion increases AS160 phosphorylation and enhances GLUT4 surface expression and glucose uptake in skeletal myotubes, placing FKBP51 as a negative regulator upstream of the AKT2-AS160 axis.\",\n      \"method\": \"Co-immunoprecipitation; phosphorylation immunoblot; GLUT4 surface assay; FKBP51 KO mice; SAFit2 pharmacological treatment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus genetic KO and pharmacological inhibition with functional readout; single lab\",\n      \"pmids\": [\"29170369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rab28 is a substrate for the GAP domains of both TBC1D4 and TBC1D1 in vitro; Rab28 GTP-binding state is acutely regulated by insulin in vivo; Rab28 siRNA knockdown decreases basal glucose uptake in skeletal muscle, and constitutively active Rab28 increases basal GLUT4 surface levels in adipocytes.\",\n      \"method\": \"In vitro GAP activity assay; GTP-binding measurement; siRNA knockdown in isolated muscle; constitutively active Rab28-Q72L overexpression\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro substrate identification confirmed by in vivo loss/gain-of-function; single lab\",\n      \"pmids\": [\"27929607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"AS160 knockdown causes blunted cell proliferation and G1 phase arrest in multiple cell lines in a glucose-independent manner; this is mediated by upregulation of the CDK inhibitor p21; AS160 overexpression downregulates p21 and rescues arrested cell cycle; p21 knockdown rescues the proliferation defect caused by AS160 depletion.\",\n      \"method\": \"shRNA knockdown in fibroblasts and cancer cells; cell cycle analysis; p21 immunoblot; AS160 overexpression rescue; p21 siRNA double knockdown\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function, overexpression rescue, and epistatic double knockdown; single lab\",\n      \"pmids\": [\"27152871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"AS160 (TBC1D4) acts as the Rab14 GAP within Chlamydia trachomatis-infected cells; bacterial infection induces Akt phosphorylation and phosphorylation/inactivation of AS160 at the inclusion membrane, thereby maintaining Rab14 in the GTP-bound state to facilitate sphingolipid delivery to chlamydial inclusions; Akt inhibition prevents AS160 phosphorylation, reduces Rab14 at inclusions, and impairs bacterial replication.\",\n      \"method\": \"Pharmacological Akt inhibition; AS160 siRNA knockdown; immunofluorescence; electron microscopy; sphingolipid trafficking assay\",\n      \"journal\": \"Frontiers in microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with two independent approaches (inhibitor and siRNA) and defined trafficking readout; single lab\",\n      \"pmids\": [\"31001235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"AS160 phosphorylation on Ser588 and Thr642 is regulated by PP1-α: PP1-α co-immunoprecipitates with AS160 (not PP1-β, PP1-γ1, or PP2A); recombinant PP1 inhibitor-2 delays AS160 dephosphorylation; PP1-α siRNA knockdown increases AS160 phosphorylation on both sites without altering Akt phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation of PP1 isoforms with AS160; pharmacological phosphatase inhibitor treatment; recombinant inhibitor-2 protein; PP1-α/β/γ1 siRNA knockdown; phosphospecific immunoblot\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP of endogenous proteins, domain-specific inhibitor, and isoform-specific siRNA all converging on same finding\",\n      \"pmids\": [\"27246912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TBC1D4-Ser711 phosphorylation by AMPK mediates the insulin-sensitizing effect of exercise on skeletal muscle glucose uptake: TBC1D4-S711A knockin mice show normal contraction-stimulated glucose uptake but lack the post-exercise/contraction enhancement of insulin sensitivity observed in wild-type mice; enhanced TBC1D4-S711 phosphorylation occurs concomitantly with improved insulin sensitivity after exercise.\",\n      \"method\": \"TBC1D4-S711A knockin mouse; in vitro contraction; hyperinsulinemic-euglycemic clamp; glucose uptake measurement; AMPK activity assay; phosphospecific immunoblot\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic knockin with defined physiological phenotype and mechanistic specificity\",\n      \"pmids\": [\"37074686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In cells co-expressing both TBC1D4 and TBC1D1, Tbc1d1 functionally dominates AS160/TBC1D4, and GLUT4 release relies on Tbc1d1-evoking proximal stimuli (AICAR, Ca2+); AS160 modulates sensitivity to stimuli in Tbc1d1-mediated GLUT4 release; cooperative actions require the PTB1 and calmodulin-binding domains of Tbc1d1 and phosphorylation sites on both AS160 (Thr642) and Tbc1d1 (Ser237, Thr596).\",\n      \"method\": \"GLUT4 nanometry; cell-based reconstitution; varying expression ratios; mutational analyses of multiple domains and phosphorylation sites\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reconstitution with multiple mutants; single lab\",\n      \"pmids\": [\"30482843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"AS160 expression is essential for post-exercise enhancement of insulin-stimulated glucose uptake (ISGU) in skeletal muscle: AS160-KO rats lack post-exercise improvement in ISGU; AAV-mediated rescue of AS160 in AS160-KO muscle restores this enhancement; AAV-delivered GLUT4 alone does not rescue; AS160 mutated at Ser588/Thr642/Ser704 only partially restores the post-exercise effect.\",\n      \"method\": \"AS160-KO rat model; AAV-mediated gene delivery of wild-type or phosphomutant AS160 and GLUT4; isolated muscle glucose uptake assay post-exercise\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple AAV rescue experiments providing mechanistic dissection, in vivo exercise model\",\n      \"pmids\": [\"34753801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AS160 is expressed in pancreatic beta-cells and phosphorylated after glucose stimulation via insulin receptor/IRS-2/PI3K/Akt, independently of cytosolic Ca2+; AS160 knockdown in MIN6B1 beta-cells increases basal insulin secretion, abolishes glucose-stimulated insulin release, increases apoptosis, and eliminates glucose-induced proliferation.\",\n      \"method\": \"shRNA knockdown and siRNA in MIN6B1 and primary mouse islet cells; AS160 phosphorylation immunoblot; insulin secretion assay; apoptosis measurement\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-specific knockdown with multiple phenotypic readouts; single lab\",\n      \"pmids\": [\"18276765\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TBC1D4/AS160 is a Rab GTPase-activating protein (with GAP activity established in vitro against Rabs 2A, 8A, 10, 14, and 28) that resides on GLUT4 storage vesicles via its PTB2 domain interaction with IRAP, where it maintains GLUT4 intracellular retention by keeping target Rabs in the GDP-bound inactive state; insulin activates Akt2 (and additionally RSK1/SGK1) to phosphorylate multiple sites including the critical Thr649 (human Thr642), triggering 14-3-3 binding that disrupts IRAP interaction and releases the inhibitory constraint on Rab10/Rab8A, thereby enabling GLUT4 vesicle docking and fusion with the plasma membrane; exercise/contraction-stimulated AMPK additionally phosphorylates Ser711 (a key site for post-exercise insulin sensitization) and other sites; the RabGAP activity also maintains GLUT4 protein levels by preventing lysosomal degradation; AS160 additionally regulates trafficking of CD36, Na+/K+-ATPase, ENaC, and AQP2 through analogous phospho-regulated Rab-GAP mechanisms, and controls cell proliferation through p21.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TBC1D4 (AS160) is a Rab GTPase-activating protein that serves as the central insulin- and contraction-responsive brake on regulated GLUT4 vesicle trafficking, coupling kinase signaling to membrane fusion [#0, #2]. Its recombinant GAP domain hydrolyzes GTP on Rabs 2A, 8A, 10, and 14, an activity destroyed by mutation of the catalytic arginine, and crystallography defines an all-\\u03b1-helical Rab-binding fold whose interface residues are required for catalysis and GLUT4 translocation [#0, #17]. In the basal state TBC1D4 docks onto GLUT4 storage vesicles through its second PTB domain, which binds the cytosolic tail of IRAP and, via a distinct phospholipid-binding region, mediates vesicle versus plasma-membrane targeting; this membrane association keeps target Rabs (notably Rab8A and Rab10) GDP-bound and retains GLUT4 intracellularly, since knockdown or GAP-dead rescue releases GLUT4 to the surface [#1, #13, #18, #6, #25]. Insulin drives Akt2 to phosphorylate the critical Thr642 (mouse Thr649), recruiting 14-3-3 and disrupting the IRAP/membrane interaction, thereby relieving the Rab brake to permit GLUT4 vesicle docking and fusion; knockin of the non-phosphorylatable Thr649Ala allele impairs muscle glucose disposal in vivo [#4, #16, #14, #24]. A parallel contraction/exercise pathway uses AMPK-\\u03b12, which directly phosphorylates TBC1D4 including Ser711, the site required for post-exercise insulin sensitization but dispensable for acute contraction-stimulated uptake [#7, #8, #15, #41, #43]. Phosphorylation regulates vesicle recruitment rather than intrinsic catalysis, as full-length oligomeric TBC1D4 retains GAP activity after Akt or AMPK phosphorylation while losing IRAP binding [#23]. Beyond acute trafficking, the GAP activity maintains GLUT4 protein abundance by preventing its lysosomal degradation, and combined loss of TBC1D4 and TBC1D1 abolishes insulin-stimulated glucose uptake in muscle and fat [#22, #21]. The same phospho-regulated Rab-GAP logic governs trafficking of additional cargoes including CD36, the Na+/K+-ATPase, ENaC, and AQP2, and TBC1D4 further restrains cell proliferation through p21 [#20, #26, #27, #33, #38].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that AS160/TBC1D4 is an enzyme with defined Rab-GAP activity and a catalytic arginine, identifying its biochemical mechanism of action.\",\n      \"evidence\": \"In vitro GAP assay with recombinant GAP domain and catalytic arginine-to-lysine mutagenesis, plus MS of GLUT4-vesicle Rabs\",\n      \"pmids\": [\"15971998\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro Rab specificity did not establish which Rabs are physiological in-cell targets\", \"No structure of the catalytic domain at this stage\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed that AS160 physically docks on GLUT4 vesicles via IRAP and acts as a basal-state inhibitor, explaining how a cytosolic GAP is targeted to its trafficking compartment.\",\n      \"evidence\": \"GLUT4-vesicle proteomics, reciprocal IRAP co-IP, and shRNA knockdown with GLUT4 surface measurement in adipocytes\",\n      \"pmids\": [\"16154996\", \"16213228\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the downstream Rab effector relieved upon dissociation\", \"Mechanism linking GAP activity to retention not yet resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Localized AS160 action to the GLUT4 exocytic limb, specifically before vesicle fusion, distinguishing it from endocytic regulation.\",\n      \"evidence\": \"Dominant-inhibitory AS160 mutant with quantitative exo/endocytosis assays in adipocytes\",\n      \"pmids\": [\"15254270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not pinpoint docking versus fusion sub-step\", \"No molecular identity of the blocked Rab\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined the insulin-input mechanism: Akt-dependent phosphorylation at Thr642 creates a 14-3-3 binding site that relieves inhibition, and dual kinase inputs (Akt2 for insulin, AMPK-\\u03b12 for contraction) converge on AS160.\",\n      \"evidence\": \"LC-MS/MS 14-3-3 capture, phosphosite mutagenesis, GLUT4 translocation assays, plus Akt2-KO and AMPK transgenic mouse phosphorylation studies and cell-free AMPK kinase assays\",\n      \"pmids\": [\"16880201\", \"16804077\", \"16804075\", \"16762977\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether 14-3-3 binding alters GAP catalysis or only localization was unresolved\", \"Functional Rab targets relieved by phosphorylation not yet defined in cells\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified the in-cell Rab effectors (Rab8A, Rab10, Rab14) downstream of AS160, converting in vitro substrates into a physiological pathway and placing Rab8A downstream of AS160 phosphorylation.\",\n      \"evidence\": \"Constitutively active/dominant Rab rescue and siRNA epistasis in L6 and adipocytes, with Rac/actin and VAMP2 perturbations dissecting trafficking steps\",\n      \"pmids\": [\"17208202\", \"17403373\", \"18650435\", \"18063571\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-type-specific dominance of Rab8A versus Rab10 not fully reconciled\", \"Docking versus fusion contributions of individual Rabs not separated\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Mapped the multi-site phospho-code and additional regulatory domains, showing distinct kinases (RSK1, SGK1, PKB, AMPK) and a calmodulin-binding domain selectively gating contraction responses.\",\n      \"evidence\": \"MS phosphosite mapping, in vitro kinase assays with multiple kinases, and in vivo CBD-mutant electroporation with glucose uptake\",\n      \"pmids\": [\"17617058\", \"16935857\", \"17717281\", \"17259386\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of most individual sites beyond Thr642 unresolved\", \"How calmodulin modulates GAP activity mechanistically not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Refined the targeting logic: membrane/GSV association via the PTB2 region confers the basal inhibitory effect, separating localization from catalysis.\",\n      \"evidence\": \"Subcellular fractionation and membrane-targeting/phosphomutant constructs in adipocytes\",\n      \"pmids\": [\"18801932\", \"23045393\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether dissociation per se is dispensable versus phosphorylation remained debated across constructs\", \"Lipid identity driving membrane binding not fully defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided in vivo genetic and structural proof that Thr649 phosphorylation and the GAP fold are required for muscle insulin action.\",\n      \"evidence\": \"Thr649Ala knockin mice with hyperinsulinemic-euglycemic clamp and muscle glucose transport, plus X-ray crystallography of the GAP domain with mutagenesis\",\n      \"pmids\": [\"21195350\", \"21454505\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue divergence (muscle versus adipocyte phenotype) mechanism unexplained\", \"Full-length protein architecture beyond GAP domain unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed a second, slower function of GAP activity: maintaining GLUT4 protein levels by preventing lysosomal degradation, and demonstrated genetic redundancy with TBC1D1.\",\n      \"evidence\": \"RabGAP-inactive R917K knockin and muscle-specific KO with lysosome-inhibition rescue, plus Tbc1d1/Tbc1d4 double-KO clamp studies\",\n      \"pmids\": [\"27554475\", \"25249576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which Rab(s) route GLUT4 to lysosomes not identified\", \"Division of labor between TBC1D1 and TBC1D4 substrates incompletely resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved the long-standing question of whether phosphorylation regulates catalysis versus recruitment, showing full-length oligomeric TBC1D4 retains GAP activity but loses IRAP binding upon Akt/AMPK phosphorylation.\",\n      \"evidence\": \"Baculovirus full-length protein, size-exclusion chromatography, Michaelis-Menten kinetics with isotope-labeled ATP, MS site mapping, and co-IP\",\n      \"pmids\": [\"33872597\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of oligomerization not determined\", \"How recruitment loss translates to Rab activation in vivo not directly visualized\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the molecular basis of exercise-induced insulin sensitization, attributing it specifically to AMPK phosphorylation of Ser711.\",\n      \"evidence\": \"TBC1D4-S711A knockin mice with contraction protocols and hyperinsulinemic-euglycemic clamps, plus the earlier AS160-KO rat AAV rescue series\",\n      \"pmids\": [\"37074686\", \"34753801\", \"19923418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effector linking Ser711 to sustained sensitization unknown\", \"Whether human Ser711-equivalent behaves identically not addressed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Generalized the TBC1D4 mechanism to other cargoes and contexts, showing analogous phospho-regulated Rab-GAP control of CD36, Na+/K+-ATPase, ENaC, AQP2, GLUT1, lipid droplet fusion, cell proliferation, and even pathogen-driven trafficking.\",\n      \"evidence\": \"Knockdown/overexpression, domain mapping, phosphosite mutagenesis, and trafficking/electrophysiology readouts across cardiomyocytes, kidney epithelia, adipocytes, beta-cells, cancer cells, and Chlamydia-infected cells\",\n      \"pmids\": [\"22315395\", \"20943949\", \"20410134\", \"21511697\", \"20937822\", \"31816312\", \"25158853\", \"27152871\", \"31001235\", \"18276765\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Most non-GLUT4 cargoes shown in single labs without in vivo genetic confirmation\", \"Shared versus cargo-specific Rab effectors not systematically mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the network of upstream regulators (PP1-\\u03b1, FKBP51, RIP140, RUVBL2, ClipR-59, WNK1, Rip11) integrates with the core Akt/AMPK\\u201314-3-3 axis to set GAP activity quantitatively in different tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model of phospho-input integration\", \"Most regulators validated in single cell systems without genetic in vivo data\", \"Structural basis of full-length regulation incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 17, 23]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [1, 13, 18]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 23]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 7, 16]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 3, 24]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [20, 26, 27]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [9, 21, 22]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [38]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"IRAP\", \"Rab10\", \"Rab8A\", \"Rab14\", \"AKT2\", \"PRKAA2\", \"YWHAB\", \"WNK1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}