{"gene":"WIPI2","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2014,"finding":"WIPI2b directly binds ATG16L1 and acts as a PI3P effector upstream of ATG16L1, recruiting the ATG12-5-16L1 complex to phagophores to enable LC3 conjugation and starvation-induced autophagy. Atg16L1 mutants that cannot bind WIPI2b but retain FIP200 binding fail to rescue starvation-induced autophagy. WIPI2b also recruits the ATG12-5-16L1 complex to Salmonella-surrounding membranes to initiate LC3 conjugation and bacterial clearance.","method":"Co-immunoprecipitation, pulldown, ectopic membrane targeting (plasma membrane), mutagenesis of ATG16L1-WIPI2b interface, WIPI2 depletion with specific phenotypic readouts (LC3 lipidation, autophagosome formation, bacterial clearance)","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal pulldowns, mutagenesis, ectopic localization rescue, replicated across multiple assay systems in a single rigorous study","pmids":["24954904"],"is_preprint":false},{"year":2010,"finding":"WIPI2 is a mammalian PI3P effector that is recruited to early autophagosomal structures (omegasomes) along with ATG16L1 and ULK1. Depletion of WIPI2 blocks LC3-positive autophagosome formation and causes accumulation of DFCP1-labeled omegasome structures, placing WIPI2 downstream of PI3P synthesis and upstream of autophagosome maturation.","method":"siRNA knockdown, fluorescence microscopy, localization studies, co-localization with autophagy markers","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (KD, imaging, marker co-localization) with clear phenotypic readouts, replicated in subsequent studies","pmids":["20505359"],"is_preprint":false},{"year":2021,"finding":"Crystal structure of WIPI2d in complex with the WIPI2-interacting region (W2IR, residues 207-230) of ATG16L1 at 1.85 Å resolution shows the ATG16L1 W2IR adopts an alpha-helical conformation binding in an electropositive and hydrophobic groove between WIPI2 β-propeller blades 2 and 3. Interface mutations reduce or block ATG12-5-16L1 recruitment, LC3B conjugation to synthetic membranes, and starvation-induced autophagy. WIPI1/2 form a W2IR-binding subclass, while WIPI3/4 form a W34IR-binding subclass for ATG2 localization.","method":"X-ray crystallography (1.85 Å), interface mutagenesis, in vitro lipidation assay on synthetic membranes, cell-based autophagy assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mutagenesis validated by both in vitro reconstitution and cell-based assays in a single rigorous study","pmids":["34505572"],"is_preprint":false},{"year":2020,"finding":"Complete in vitro reconstitution on giant unilamellar vesicles (GUVs) showed that LC3 lipidation is strictly PI3P-dependent via WIPI2 recruitment. WIPI2 allosterically activates the ATG12-ATG5-ATG16L1 E3 complex—ectopically targeting E3 to membranes without WIPI2 is insufficient for LC3 lipidation. PI3KC3-C1 and WIPI2 mutually promote each other's membrane recruitment in a positive feedback loop, producing rapid LC3 lipidation kinetics.","method":"Reconstitution on GUVs, PI3P-dependent recruitment assays, ectopic E3 targeting, PI3KC3-C1/WIPI2 positive feedback assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — complete biochemical reconstitution on GUVs with multiple orthogonal experiments demonstrating allosteric activation and positive feedback","pmids":["32437499"],"is_preprint":false},{"year":2018,"finding":"mTORC1 directly phosphorylates WIPI2 at Ser395, directing WIPI2 to interact with the E3 ubiquitin ligase HUWE1, which ubiquitinates WIPI2 for proteasomal degradation. Inhibition of mTORC1 promotes WIPI2 stabilization and autophagosome formation. In mouse liver, fasting increases WIPI2 protein levels; HUWE1 silencing enhances autophagy and WIPI2 introduction improves lipid clearance.","method":"In vitro kinase assay, mass spectrometry phosphorylation site mapping (Ser395), co-immunoprecipitation, ubiquitination assay, siRNA/overexpression in cells and mouse liver","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay combined with site mutagenesis, biochemical ubiquitination assay, and in vivo mouse validation with multiple orthogonal methods","pmids":["30340022"],"is_preprint":false},{"year":2018,"finding":"WIPI2 localizes to autophagosome precursor membranes by binding RAB11A, a recycling endosome marker. PI3P is generated on RAB11A-positive membranes upon starvation. Loss of RAB11A impairs WIPI2 recruitment and assembly of the autophagic machinery. RAB11A-positive membranes are a primary direct platform for canonical autophagosome formation enabling mitophagy of damaged mitochondria and autophagy of transferrin receptor.","method":"Co-immunoprecipitation, fluorescence live-cell imaging, RAB11A knockout/depletion, co-localization, functional autophagy assays","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, live imaging, KO phenotyping with multiple orthogonal readouts in a single focused study","pmids":["29634932"],"is_preprint":false},{"year":2019,"finding":"During mitosis, CUL4-RING ubiquitin ligases (CRL4s) are activated via neddylation and recruit WIPI2 through DDB1, leading to WIPI2 polyubiquitination and proteasomal degradation, thereby suppressing autophagy during mitosis. Knockdown of CRL4s or inhibition with MLN4924/Pevonedistat rescues WIPI2 levels and autophagy during mitosis; restoration of WIPI2 causes mitotic slippage and cell senescence.","method":"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, MLN4924 pharmacological inhibition, flow cytometry (cell cycle), functional autophagy assays","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, biochemical ubiquitination assay, pharmacological and genetic perturbation with defined cell-cycle phenotypes in a single study","pmids":["30898011"],"is_preprint":false},{"year":2023,"finding":"STING directly interacts with WIPI2 via binding to the PI3P-binding FRRG motif of WIPI2, thereby recruiting WIPI2 to STING-positive vesicles to drive LC3 lipidation and autophagosome formation independently of canonical PI3P-dependent initiation. STING and PI3P competitively bind the FRRG motif of WIPI2, causing mutual inhibition between STING-induced and PI3P-dependent autophagy. The STING-WIPI2 interaction is required for clearance of cytoplasmic DNA and attenuation of cGAS-STING signaling.","method":"Co-immunoprecipitation, mutagenesis of WIPI2 FRRG motif, competition binding assay, cell-based autophagy assays, cytoplasmic DNA clearance assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated with mutagenesis of the interface, competitive binding assay, and functional readouts in multiple cell-based assays","pmids":["36872914"],"is_preprint":false},{"year":2016,"finding":"Recruitment of WIPI2 to cytosol-invading Salmonella is dependent on the localization of catalytically active TBK1 in the vicinity of the bacteria. TBK1 stabilizes WIPI2 on bacteria and acts upstream of WIPI2-dependent antibacterial autophagy. Multiple Salmonella-associated 'eat-me' signals (glycans, K48- and K63-linked ubiquitin chains) independently recruit TBK1 functionality, providing redundancy for WIPI2 stabilization.","method":"Fluorescence microscopy, TBK1 recruitment manipulation (experimental targeting constructs), siRNA knockdown, bacterial proliferation assays","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — experimental TBK1 recruitment manipulation with fluorescence imaging and functional readouts, single lab","pmids":["27370208"],"is_preprint":false},{"year":2022,"finding":"WIPI2 is recruited to damaged mitochondria upon mitophagy induction, binds VCP/p97, and promotes VCP recruitment to damaged mitochondria. WIPI2 depletion blunts VCP recruitment, reduces degradation of outer mitochondrial membrane (OMM) proteins, and impairs PINK1-PRKN-mediated mitophagy. Cells deficient in WIPI2 are largely resistant to mitochondrial damage-induced cell death.","method":"Co-immunoprecipitation, siRNA knockdown, fluorescence microscopy, mitophagy flux assays, OMM protein degradation assays","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP combined with KD and functional mitophagy readouts, single lab","pmids":["35389758"],"is_preprint":false},{"year":2023,"finding":"The Nix minimal essential region (MER) directly interacts with WIPI2 and recruits WIPI2 to mitochondria, independently of the Nix LIR motif. The Nix LIR motif converts a homogeneous WIPI2 distribution on mitochondria into puncta even without ATG8s. Both MER-WIPI2 interaction and LIR motif are required for robust Nix-induced mitophagy.","method":"Chemically induced dimerization (CID), co-immunoprecipitation, fluorescence microscopy, mitophagy assays, domain-function mutagenesis","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CID system with Co-IP and fluorescence imaging, single lab, multiple orthogonal approaches","pmids":["37621214"],"is_preprint":false},{"year":2023,"finding":"ATG16L1 contains two distinct WIPI2-binding sites (WBS1, previously known, and WBS2, newly identified). Crystal structures of WIPI2 with both ATG16L1 WBS1 and WBS2 show distinct binding mechanisms; WBS2 and its binding mode are conserved from yeast to mammals. Integrity of both binding sites is essential for normal autophagic flux.","method":"X-ray crystallography, isothermal titration calorimetry (ITC), cell-based autophagic flux assays, mutagenesis","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures with ITC validation and cell-based functional assays, single lab","pmids":["37165562"],"is_preprint":false},{"year":2004,"finding":"Yeast Atg21 (ortholog of WIPI2) is a phosphoinositide-binding protein required for efficient Atg8 lipidation and localization of Atg8 to the pre-autophagosomal structure (PAS) during the Cvt pathway. Loss of Atg21 also affects localization of the Atg12-Atg5 conjugate to the PAS, suggesting a role in recruiting membrane conjugation machinery.","method":"Genetic deletion, fluorescence microscopy (GFP-Atg8 localization), biochemical Atg8 lipidation assay, protease protection assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic and biochemical methods in yeast ortholog establishing pathway position, single lab","pmids":["15155809"],"is_preprint":false},{"year":2010,"finding":"The FRRG phosphoinositide-binding motif of yeast Atg21 is required for its function. PtdIns(3)P-binding mutants of Atg21 show highly reduced autophagy and aberrant localization of both Atg8 and Atg16 to the phagophore assembly site. Atg18 and Atg21 protect Atg8-PE from premature cleavage by Atg4 at the PAS, and they compensate for each other in recruiting PI3P-dependent Atg components.","method":"Site-directed mutagenesis of FRRG motif, fluorescence microscopy, multiple knockout strain analysis, Atg8-PE lipidation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with multiple readouts in yeast ortholog, single lab","pmids":["20154084"],"is_preprint":false},{"year":2015,"finding":"Yeast Atg21 (WIPI2 ortholog) binds PI3P via its β-propeller and localizes to the PAS. Atg21 directly interacts with the coiled-coil domain of Atg16 and with Atg8 via the conserved F5K6-motif in Atg8's N-terminal helical domain (distinct from the AIM-binding site), leaving the AIM site free for Atg3 interaction. Atg21 thus scaffolds both the E3 ligase complex and Atg8 at the PAS in a PI3P-dependent manner.","method":"Co-immunoprecipitation, pulldown, yeast two-hybrid, fluorescence microscopy, mutagenesis, PI3P-binding assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal binding assays (Co-IP, pulldown, Y2H), mutagenesis, functional localization studies in yeast ortholog, replicated with mammalian counterpart in other studies","pmids":["25691244"],"is_preprint":false},{"year":2020,"finding":"Yeast Atg21 localizes specifically to the phagophore edge at the vacuole-isolation membrane contact site (VICS). Crystal structure of Atg21 with the Atg16 coiled-coil domain shows Atg16 binds at the bottom side of the Atg21 β-propeller, establishing the orientation relative to the membrane. Vac8 is required for VICS formation and Atg21 organization of the Atg8-lipidation machinery.","method":"X-ray crystallography, fluorescence microscopy, FRAP, genetic deletion (Vac8), FCCS","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with fluorescence imaging and genetic validation in yeast ortholog, single lab","pmids":["32515645"],"is_preprint":false},{"year":2024,"finding":"Molecular dynamics simulations combined with in vitro and cell-based experiments show that LC3 lipidation occurs through a three-step docking mechanism: (1) WIPI2 recruits the ATG12-ATG5-ATG16L1 complex to PI3P-containing membranes, (2) ATG16L1 helix α2 engages the membrane, and (3) ATG3 inserts a membrane-interacting surface. Phosphatidylethanolamine lipids concentrate near the ATG3-LC3 thioester bond, with two conserved histidines implicated in catalytic transfer.","method":"Molecular dynamics simulations, in vitro reconstitution, cell-based assays, mutagenesis","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — combined MD and reconstitution, single lab, mechanistic details partially computational","pmids":["38324698"],"is_preprint":false},{"year":2019,"finding":"A homozygous missense mutation (V249M) in the PI3P/PI(3,5)P2-binding region of WIPI2 causes neurodevelopmental disorder. Functional studies show that the V231M WIPI2b mutant has significantly reduced binding to ATG16L1 (and ATG5-12) in GFP pulldown assays, and patient fibroblasts show reduced WIPI2 puncta, reduced LC3 lipidation, and reduced autophagic flux.","method":"GFP pulldown, patient fibroblast functional assay (LC3 lipidation, WIPI2 puncta, autophagic flux), whole-exome sequencing","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pulldown with disease mutant combined with patient-derived cell functional assays, single lab","pmids":["30968111"],"is_preprint":false},{"year":2011,"finding":"Freeze-fracture replica immunolabelling reveals WIPI2 as a membrane-integrated component of autophagosomes and the plasma membrane, and also detects WIPI2 in membranes near Golgi cisternae, identifying WIPI2 as a membrane protein of autophagosomal structures.","method":"Freeze-fracture replica immunolabelling electron microscopy","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization by specialized EM technique, single lab, single method","pmids":["21564513"],"is_preprint":false},{"year":2019,"finding":"Dynamic and local phosphorylation of WIPI2 is a critical regulatory step in autophagosome biogenesis in neurons. The rate of WIPI2-dependent autophagosome formation declines significantly with age in axons of neurons from aged mice. Overexpression of WIPI2 rescues the age-dependent decline in autophagosome formation.","method":"Live-cell microscopy (axonal autophagosome formation), WIPI2 overexpression rescue, aged mouse neuron culture","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging with functional rescue by WIPI2 overexpression, single lab","pmids":["31794336"],"is_preprint":false},{"year":2017,"finding":"Optineurin promotes recruitment of the ATG12-5-16L1 complex to WIPI2-positive phagophores, facilitating LC3-II production and autophagosome maturation. Optineurin interacts with ATG5 and the ATG12-5 conjugate; loss of optineurin reduces ATG12/16L1-positive puncta and their co-recruitment to WIPI2-positive phagophores, but does not reduce the number of WIPI2-positive phagophores.","method":"Co-immunoprecipitation, optineurin knockout mouse fibroblasts, fluorescence microscopy, LC3 lipidation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with KO cell functional assays and imaging, single lab, places optineurin downstream of WIPI2 in the pathway","pmids":["29133525"],"is_preprint":false}],"current_model":"WIPI2 is a PI3P-binding β-propeller (WD-repeat) protein that acts as a central hub in autophagosome biogenesis: upon autophagy induction, PI3P generated by PI3KC3-C1 recruits WIPI2 to phagophore membranes (on omegasomes, RAB11A-positive recycling endosomes, and damaged mitochondria), where WIPI2 allosterically activates the ATG12-5-16L1 E3-like complex (by binding ATG16L1 in an electropositive groove between β-propeller blades 2 and 3) to drive LC3/ATG8 lipidation; WIPI2 stability is controlled by mTORC1-mediated phosphorylation at Ser395 directing it to the HUWE1 E3 ligase for proteasomal degradation, and by CRL4-DDB1-mediated ubiquitination during mitosis; in antibacterial autophagy, TBK1 stabilizes WIPI2 on bacteria, and STING directly recruits WIPI2 via its FRRG motif to bypass canonical PI3P-dependent initiation; WIPI2 also promotes mitophagy by recruiting VCP/p97 to damaged mitochondria and interacts with the Nix MER domain during receptor-mediated mitophagy."},"narrative":{"mechanistic_narrative":"WIPI2 is a PI3P-binding β-propeller protein that serves as the central effector linking PI3P generation to LC3/ATG8 lipidation during autophagosome biogenesis [PMID:20505359, PMID:24954904]. Upon autophagy induction, PI3P produced on phagophore-associated membranes recruits WIPI2, which directly binds ATG16L1 and recruits the ATG12–5–16L1 E3-like complex to the phagophore to drive LC3 conjugation; ATG16L1 mutants that retain FIP200 binding but cannot bind WIPI2 fail to support starvation-induced autophagy [PMID:24954904]. Complete reconstitution on giant unilamellar vesicles established that this recruitment is strictly PI3P-dependent and that WIPI2 allosterically activates the E3 complex—simply targeting the E3 to membranes is insufficient—while PI3KC3-C1 and WIPI2 reinforce each other's membrane recruitment in a positive feedback loop that accelerates lipidation kinetics [PMID:32437499, PMID:38324698]. Structurally, the ATG16L1 W2IR helix docks in an electropositive groove between WIPI2 β-propeller blades 2 and 3, and a second binding site (WBS2) conserved from yeast to mammals contributes to the interaction; both sites are required for normal autophagic flux [PMID:34505572, PMID:37165562]. WIPI2 is recruited to multiple membrane platforms including omegasomes and RAB11A-positive recycling endosomes, the latter serving as a primary platform for autophagosome formation and mitophagy [PMID:20505359, PMID:29634932]. WIPI2 abundance is tightly regulated: mTORC1 phosphorylates WIPI2 at Ser395 to direct it to the HUWE1 E3 ligase for proteasomal degradation, coupling nutrient status to autophagic capacity, and during mitosis CRL4–DDB1 ubiquitinates WIPI2 to suppress autophagy [PMID:30340022, PMID:30898011]. Beyond canonical starvation autophagy, WIPI2 mediates antibacterial autophagy of Salmonella downstream of TBK1 [PMID:24954904, PMID:27370208], is engaged by STING via competitive binding to its FRRG motif to drive PI3P-independent autophagy and cytoplasmic DNA clearance [PMID:36872914], and promotes mitophagy by recruiting VCP/p97 to damaged mitochondria and interacting with the Nix MER domain [PMID:35389758, PMID:37621214]. A homozygous WIPI2 missense mutation in its phosphoinositide-binding region causes a neurodevelopmental disorder, with patient fibroblasts showing reduced ATG16L1 binding, LC3 lipidation, and autophagic flux [PMID:30968111].","teleology":[{"year":2004,"claim":"Established the pathway position of the WIPI2 ortholog by showing it is required for ATG8 lipidation and recruitment of the conjugation machinery, defining a conserved role upstream of ATG8 conjugation.","evidence":"Genetic deletion, GFP-Atg8 imaging, and lipidation assays in yeast Atg21","pmids":["15155809"],"confidence":"Medium","gaps":["Did not define the direct binding partner mediating recruitment","Yeast Cvt pathway context, not mammalian starvation autophagy"]},{"year":2010,"claim":"Placed mammalian WIPI2 downstream of PI3P synthesis and upstream of autophagosome maturation, showing its loss arrests omegasome-stage structures.","evidence":"siRNA knockdown and co-localization imaging with autophagy markers in mammalian cells","pmids":["20505359"],"confidence":"High","gaps":["Direct molecular partner of WIPI2 not yet identified","Mechanism of E3 recruitment unresolved"]},{"year":2010,"claim":"Demonstrated the FRRG phosphoinositide-binding motif is required for ortholog function and that it scaffolds Atg8 and Atg16 localization while protecting Atg8-PE from premature Atg4 cleavage.","evidence":"FRRG motif mutagenesis and lipidation assays in yeast Atg21","pmids":["20154084"],"confidence":"Medium","gaps":["Direct vs indirect recruitment of Atg16 not distinguished here","Yeast ortholog, mammalian relevance inferred"]},{"year":2014,"claim":"Identified the direct WIPI2b–ATG16L1 interaction as the mechanism by which a PI3P effector recruits the E3-like conjugation complex, the key molecular link between PI3P and LC3 lipidation.","evidence":"Co-IP, pulldown, interface mutagenesis, ectopic membrane targeting, and depletion phenotypes for both starvation and Salmonella autophagy","pmids":["24954904"],"confidence":"High","gaps":["Whether WIPI2 merely tethers or allosterically activates the E3 not yet resolved","Structural basis of interface unknown"]},{"year":2015,"claim":"Defined how the ortholog scaffolds both the E3 complex and Atg8 simultaneously, binding Atg16 via its coiled-coil and Atg8 via a non-AIM motif that leaves the AIM site free for Atg3.","evidence":"Co-IP, pulldown, yeast two-hybrid, and mutagenesis in yeast Atg21","pmids":["25691244"],"confidence":"High","gaps":["Membrane orientation of the scaffold not defined","Mammalian Atg8 binding not directly tested"]},{"year":2018,"claim":"Connected nutrient signaling to WIPI2 stability by showing mTORC1 phosphorylates Ser395 to trigger HUWE1-mediated degradation, providing a switch that gates autophagic capacity.","evidence":"In vitro kinase assay, phosphosite mapping, ubiquitination assay, and in vivo mouse liver fasting/HUWE1 silencing","pmids":["30340022"],"confidence":"High","gaps":["How Ser395 phosphorylation promotes HUWE1 binding structurally unknown","Other kinases/phosphatases not explored"]},{"year":2018,"claim":"Identified RAB11A-positive recycling endosomes as a direct membrane platform for WIPI2 recruitment and autophagosome formation, broadening the membrane sources for canonical autophagy.","evidence":"Reciprocal Co-IP, live-cell imaging, and RAB11A knockout phenotyping","pmids":["29634932"],"confidence":"High","gaps":["Relative contribution of RAB11A vs omegasome platforms unquantified","Whether RAB11A binding is direct or PI3P-mediated not fully resolved"]},{"year":2020,"claim":"Reconstitution proved that WIPI2 allosterically activates the ATG12-5-16L1 E3 and engages PI3KC3-C1 in positive feedback, distinguishing active catalysis from passive tethering.","evidence":"Complete LC3 lipidation reconstitution on GUVs with ectopic E3 targeting and feedback assays","pmids":["32437499"],"confidence":"High","gaps":["Structural basis of allosteric activation not defined here","In vivo feedback kinetics not measured"]},{"year":2020,"claim":"Localized the ortholog to the phagophore edge at the vacuole–isolation membrane contact site and established Atg16 binds the bottom face of the propeller, fixing the scaffold's membrane orientation.","evidence":"Crystal structure of Atg21–Atg16 coiled-coil, FRAP/FCCS imaging, and Vac8 deletion in yeast","pmids":["32515645"],"confidence":"High","gaps":["Mammalian VICS equivalent not established","Vac8 mammalian counterpart unknown"]},{"year":2021,"claim":"Provided the atomic structure of the WIPI2d–ATG16L1 W2IR interface in the groove between blades 2 and 3, defining the WIPI1/2 W2IR subclass distinct from the WIPI3/4 ATG2-binding subclass.","evidence":"1.85 Å crystal structure with interface mutagenesis validated in vitro and in cells","pmids":["34505572"],"confidence":"High","gaps":["Second binding site not yet characterized","Conformational changes upon membrane binding not captured"]},{"year":2023,"claim":"Revealed a second ATG16L1 binding site (WBS2) conserved across evolution, showing the WIPI2–ATG16L1 interaction is bipartite and both sites are needed for flux.","evidence":"Crystal structures of both WBS1 and WBS2 complexes, ITC, and cell-based flux assays","pmids":["37165562"],"confidence":"High","gaps":["Functional cooperativity between the two sites not quantified","Whether both engage simultaneously on membranes unknown"]},{"year":2023,"claim":"Established a non-canonical, PI3P-independent recruitment route via STING competing with PI3P for the WIPI2 FRRG motif, linking WIPI2 to innate immune DNA clearance.","evidence":"Co-IP, FRRG mutagenesis, competition binding, and cytoplasmic DNA clearance assays","pmids":["36872914"],"confidence":"High","gaps":["Structural basis of STING–FRRG binding not solved","In vivo relevance of mutual inhibition not tested"]},{"year":2023,"claim":"Identified direct recruitment of WIPI2 to mitochondria by the Nix MER domain independent of the LIR motif, defining a receptor-driven route for WIPI2 in mitophagy.","evidence":"Chemically induced dimerization, Co-IP, imaging, and mitophagy assays","pmids":["37621214"],"confidence":"Medium","gaps":["Single lab, not independently confirmed","Structural basis of MER–WIPI2 binding unknown"]},{"year":2024,"claim":"Resolved the stepwise mechanics of LC3 lipidation downstream of WIPI2 recruitment, defining membrane engagement by ATG16L1 and ATG3 and PE concentration at the catalytic site.","evidence":"Molecular dynamics simulations combined with in vitro reconstitution and cell-based assays","pmids":["38324698"],"confidence":"Medium","gaps":["Mechanistic details partly computational","Catalytic histidine roles not validated by structure"]},{"year":2019,"claim":"Linked WIPI2 dysfunction to human disease, showing a phosphoinositide-binding region mutation impairs ATG16L1 binding and autophagy and causes a neurodevelopmental disorder.","evidence":"Whole-exome sequencing, GFP pulldown of disease mutant, and patient fibroblast functional assays","pmids":["30968111"],"confidence":"Medium","gaps":["Single family/patient cohort","Tissue-specific mechanism of neurodevelopmental phenotype unresolved"]},{"year":null,"claim":"How the multiple competing recruitment routes (PI3P, STING, RAB11A, Nix MER), the dual ATG16L1 sites, and the layered degradation controls are integrated to set the timing and location of autophagosome formation in different physiological contexts remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model coordinating recruitment platforms","Crosstalk between mTORC1/HUWE1 and CRL4 degradation pathways unknown","Cell-type-specific contributions, e.g. in neurons, not mechanistically dissected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1,3,13,14]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2,11,14]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,16]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[5]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[9,10]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[18]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[0,1,3]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[7,8]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6]}],"complexes":[],"partners":["ATG16L1","RAB11A","HUWE1","DDB1","STING1","VCP","BNIP3L","OPTN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y4P8","full_name":"WD repeat domain phosphoinositide-interacting protein 2","aliases":["WIPI49-like protein 2"],"length_aa":454,"mass_kda":49.4,"function":"Component of the autophagy machinery that controls the major intracellular degradation process by which cytoplasmic materials are packaged into autophagosomes and delivered to lysosomes for degradation (PubMed:20505359, PubMed:28561066). Involved in an early step of the formation of preautophagosomal structures (PubMed:20505359, PubMed:28561066). Binds and is activated by phosphatidylinositol 3-phosphate (PtdIns3P) forming on membranes of the endoplasmic reticulum upon activation of the upstream ULK1 and PI3 kinases (PubMed:28561066). Mediates ER-isolation membranes contacts by interacting with the ULK1:RB1CC1 complex and PtdIns3P (PubMed:28890335). Once activated, WIPI2 recruits at phagophore assembly sites the ATG12-ATG5-ATG16L1 complex that directly controls the elongation of the nascent autophagosomal membrane (PubMed:20505359, PubMed:28561066) Recruits the ATG12-ATG5-ATG16L1 complex to omegasomes and preautophagosomal structures, resulting in ATG8 family proteins lipidation and starvation-induced autophagy. Isoform 4 is also required for autophagic clearance of pathogenic bacteria. Isoform 4 binds the membrane surrounding Salmonella and recruits the ATG12-5-16L1 complex, initiating LC3 conjugation, autophagosomal membrane formation, and engulfment of Salmonella","subcellular_location":"Preautophagosomal structure membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y4P8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/WIPI2","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/WIPI2","total_profiled":1310},"omim":[{"mim_id":"621000","title":"SORTING NEXIN 18; SNX18","url":"https://www.omim.org/entry/621000"},{"mim_id":"618453","title":"INTELLECTUAL DEVELOPMENTAL DISORDER WITH SHORT STATURE AND VARIABLE SKELETAL ANOMALIES; IDDSSA","url":"https://www.omim.org/entry/618453"},{"mim_id":"617074","title":"SMITH-MAGENIS SYNDROME CHROMOSOME REGION, CANDIDATE GENE 8; SMCR8","url":"https://www.omim.org/entry/617074"},{"mim_id":"616069","title":"NEONATAL NEPHROCUTANEOUS INFLAMMATORY SYNDROME; NNCIS","url":"https://www.omim.org/entry/616069"},{"mim_id":"612374","title":"STIMULATOR OF INTERFERON RESPONSE cGAMP INTERACTOR 1; STING1","url":"https://www.omim.org/entry/612374"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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acts as a PI3P effector upstream of ATG16L1, recruiting the ATG12-5-16L1 complex to phagophores to enable LC3 conjugation and starvation-induced autophagy. Atg16L1 mutants that cannot bind WIPI2b but retain FIP200 binding fail to rescue starvation-induced autophagy. WIPI2b also recruits the ATG12-5-16L1 complex to Salmonella-surrounding membranes to initiate LC3 conjugation and bacterial clearance.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, ectopic membrane targeting (plasma membrane), mutagenesis of ATG16L1-WIPI2b interface, WIPI2 depletion with specific phenotypic readouts (LC3 lipidation, autophagosome formation, bacterial clearance)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal pulldowns, mutagenesis, ectopic localization rescue, replicated across multiple assay systems in a single rigorous study\",\n      \"pmids\": [\"24954904\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"WIPI2 is a mammalian PI3P effector that is recruited to early autophagosomal structures (omegasomes) along with ATG16L1 and ULK1. Depletion of WIPI2 blocks LC3-positive autophagosome formation and causes accumulation of DFCP1-labeled omegasome structures, placing WIPI2 downstream of PI3P synthesis and upstream of autophagosome maturation.\",\n      \"method\": \"siRNA knockdown, fluorescence microscopy, localization studies, co-localization with autophagy markers\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (KD, imaging, marker co-localization) with clear phenotypic readouts, replicated in subsequent studies\",\n      \"pmids\": [\"20505359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structure of WIPI2d in complex with the WIPI2-interacting region (W2IR, residues 207-230) of ATG16L1 at 1.85 Å resolution shows the ATG16L1 W2IR adopts an alpha-helical conformation binding in an electropositive and hydrophobic groove between WIPI2 β-propeller blades 2 and 3. Interface mutations reduce or block ATG12-5-16L1 recruitment, LC3B conjugation to synthetic membranes, and starvation-induced autophagy. WIPI1/2 form a W2IR-binding subclass, while WIPI3/4 form a W34IR-binding subclass for ATG2 localization.\",\n      \"method\": \"X-ray crystallography (1.85 Å), interface mutagenesis, in vitro lipidation assay on synthetic membranes, cell-based autophagy assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mutagenesis validated by both in vitro reconstitution and cell-based assays in a single rigorous study\",\n      \"pmids\": [\"34505572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Complete in vitro reconstitution on giant unilamellar vesicles (GUVs) showed that LC3 lipidation is strictly PI3P-dependent via WIPI2 recruitment. WIPI2 allosterically activates the ATG12-ATG5-ATG16L1 E3 complex—ectopically targeting E3 to membranes without WIPI2 is insufficient for LC3 lipidation. PI3KC3-C1 and WIPI2 mutually promote each other's membrane recruitment in a positive feedback loop, producing rapid LC3 lipidation kinetics.\",\n      \"method\": \"Reconstitution on GUVs, PI3P-dependent recruitment assays, ectopic E3 targeting, PI3KC3-C1/WIPI2 positive feedback assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — complete biochemical reconstitution on GUVs with multiple orthogonal experiments demonstrating allosteric activation and positive feedback\",\n      \"pmids\": [\"32437499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"mTORC1 directly phosphorylates WIPI2 at Ser395, directing WIPI2 to interact with the E3 ubiquitin ligase HUWE1, which ubiquitinates WIPI2 for proteasomal degradation. Inhibition of mTORC1 promotes WIPI2 stabilization and autophagosome formation. In mouse liver, fasting increases WIPI2 protein levels; HUWE1 silencing enhances autophagy and WIPI2 introduction improves lipid clearance.\",\n      \"method\": \"In vitro kinase assay, mass spectrometry phosphorylation site mapping (Ser395), co-immunoprecipitation, ubiquitination assay, siRNA/overexpression in cells and mouse liver\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay combined with site mutagenesis, biochemical ubiquitination assay, and in vivo mouse validation with multiple orthogonal methods\",\n      \"pmids\": [\"30340022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"WIPI2 localizes to autophagosome precursor membranes by binding RAB11A, a recycling endosome marker. PI3P is generated on RAB11A-positive membranes upon starvation. Loss of RAB11A impairs WIPI2 recruitment and assembly of the autophagic machinery. RAB11A-positive membranes are a primary direct platform for canonical autophagosome formation enabling mitophagy of damaged mitochondria and autophagy of transferrin receptor.\",\n      \"method\": \"Co-immunoprecipitation, fluorescence live-cell imaging, RAB11A knockout/depletion, co-localization, functional autophagy assays\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, live imaging, KO phenotyping with multiple orthogonal readouts in a single focused study\",\n      \"pmids\": [\"29634932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"During mitosis, CUL4-RING ubiquitin ligases (CRL4s) are activated via neddylation and recruit WIPI2 through DDB1, leading to WIPI2 polyubiquitination and proteasomal degradation, thereby suppressing autophagy during mitosis. Knockdown of CRL4s or inhibition with MLN4924/Pevonedistat rescues WIPI2 levels and autophagy during mitosis; restoration of WIPI2 causes mitotic slippage and cell senescence.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, MLN4924 pharmacological inhibition, flow cytometry (cell cycle), functional autophagy assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, biochemical ubiquitination assay, pharmacological and genetic perturbation with defined cell-cycle phenotypes in a single study\",\n      \"pmids\": [\"30898011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"STING directly interacts with WIPI2 via binding to the PI3P-binding FRRG motif of WIPI2, thereby recruiting WIPI2 to STING-positive vesicles to drive LC3 lipidation and autophagosome formation independently of canonical PI3P-dependent initiation. STING and PI3P competitively bind the FRRG motif of WIPI2, causing mutual inhibition between STING-induced and PI3P-dependent autophagy. The STING-WIPI2 interaction is required for clearance of cytoplasmic DNA and attenuation of cGAS-STING signaling.\",\n      \"method\": \"Co-immunoprecipitation, mutagenesis of WIPI2 FRRG motif, competition binding assay, cell-based autophagy assays, cytoplasmic DNA clearance assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated with mutagenesis of the interface, competitive binding assay, and functional readouts in multiple cell-based assays\",\n      \"pmids\": [\"36872914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Recruitment of WIPI2 to cytosol-invading Salmonella is dependent on the localization of catalytically active TBK1 in the vicinity of the bacteria. TBK1 stabilizes WIPI2 on bacteria and acts upstream of WIPI2-dependent antibacterial autophagy. Multiple Salmonella-associated 'eat-me' signals (glycans, K48- and K63-linked ubiquitin chains) independently recruit TBK1 functionality, providing redundancy for WIPI2 stabilization.\",\n      \"method\": \"Fluorescence microscopy, TBK1 recruitment manipulation (experimental targeting constructs), siRNA knockdown, bacterial proliferation assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — experimental TBK1 recruitment manipulation with fluorescence imaging and functional readouts, single lab\",\n      \"pmids\": [\"27370208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"WIPI2 is recruited to damaged mitochondria upon mitophagy induction, binds VCP/p97, and promotes VCP recruitment to damaged mitochondria. WIPI2 depletion blunts VCP recruitment, reduces degradation of outer mitochondrial membrane (OMM) proteins, and impairs PINK1-PRKN-mediated mitophagy. Cells deficient in WIPI2 are largely resistant to mitochondrial damage-induced cell death.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, fluorescence microscopy, mitophagy flux assays, OMM protein degradation assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP combined with KD and functional mitophagy readouts, single lab\",\n      \"pmids\": [\"35389758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The Nix minimal essential region (MER) directly interacts with WIPI2 and recruits WIPI2 to mitochondria, independently of the Nix LIR motif. The Nix LIR motif converts a homogeneous WIPI2 distribution on mitochondria into puncta even without ATG8s. Both MER-WIPI2 interaction and LIR motif are required for robust Nix-induced mitophagy.\",\n      \"method\": \"Chemically induced dimerization (CID), co-immunoprecipitation, fluorescence microscopy, mitophagy assays, domain-function mutagenesis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CID system with Co-IP and fluorescence imaging, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"37621214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ATG16L1 contains two distinct WIPI2-binding sites (WBS1, previously known, and WBS2, newly identified). Crystal structures of WIPI2 with both ATG16L1 WBS1 and WBS2 show distinct binding mechanisms; WBS2 and its binding mode are conserved from yeast to mammals. Integrity of both binding sites is essential for normal autophagic flux.\",\n      \"method\": \"X-ray crystallography, isothermal titration calorimetry (ITC), cell-based autophagic flux assays, mutagenesis\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures with ITC validation and cell-based functional assays, single lab\",\n      \"pmids\": [\"37165562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Yeast Atg21 (ortholog of WIPI2) is a phosphoinositide-binding protein required for efficient Atg8 lipidation and localization of Atg8 to the pre-autophagosomal structure (PAS) during the Cvt pathway. Loss of Atg21 also affects localization of the Atg12-Atg5 conjugate to the PAS, suggesting a role in recruiting membrane conjugation machinery.\",\n      \"method\": \"Genetic deletion, fluorescence microscopy (GFP-Atg8 localization), biochemical Atg8 lipidation assay, protease protection assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic and biochemical methods in yeast ortholog establishing pathway position, single lab\",\n      \"pmids\": [\"15155809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The FRRG phosphoinositide-binding motif of yeast Atg21 is required for its function. PtdIns(3)P-binding mutants of Atg21 show highly reduced autophagy and aberrant localization of both Atg8 and Atg16 to the phagophore assembly site. Atg18 and Atg21 protect Atg8-PE from premature cleavage by Atg4 at the PAS, and they compensate for each other in recruiting PI3P-dependent Atg components.\",\n      \"method\": \"Site-directed mutagenesis of FRRG motif, fluorescence microscopy, multiple knockout strain analysis, Atg8-PE lipidation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with multiple readouts in yeast ortholog, single lab\",\n      \"pmids\": [\"20154084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Yeast Atg21 (WIPI2 ortholog) binds PI3P via its β-propeller and localizes to the PAS. Atg21 directly interacts with the coiled-coil domain of Atg16 and with Atg8 via the conserved F5K6-motif in Atg8's N-terminal helical domain (distinct from the AIM-binding site), leaving the AIM site free for Atg3 interaction. Atg21 thus scaffolds both the E3 ligase complex and Atg8 at the PAS in a PI3P-dependent manner.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, yeast two-hybrid, fluorescence microscopy, mutagenesis, PI3P-binding assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal binding assays (Co-IP, pulldown, Y2H), mutagenesis, functional localization studies in yeast ortholog, replicated with mammalian counterpart in other studies\",\n      \"pmids\": [\"25691244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Yeast Atg21 localizes specifically to the phagophore edge at the vacuole-isolation membrane contact site (VICS). Crystal structure of Atg21 with the Atg16 coiled-coil domain shows Atg16 binds at the bottom side of the Atg21 β-propeller, establishing the orientation relative to the membrane. Vac8 is required for VICS formation and Atg21 organization of the Atg8-lipidation machinery.\",\n      \"method\": \"X-ray crystallography, fluorescence microscopy, FRAP, genetic deletion (Vac8), FCCS\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with fluorescence imaging and genetic validation in yeast ortholog, single lab\",\n      \"pmids\": [\"32515645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Molecular dynamics simulations combined with in vitro and cell-based experiments show that LC3 lipidation occurs through a three-step docking mechanism: (1) WIPI2 recruits the ATG12-ATG5-ATG16L1 complex to PI3P-containing membranes, (2) ATG16L1 helix α2 engages the membrane, and (3) ATG3 inserts a membrane-interacting surface. Phosphatidylethanolamine lipids concentrate near the ATG3-LC3 thioester bond, with two conserved histidines implicated in catalytic transfer.\",\n      \"method\": \"Molecular dynamics simulations, in vitro reconstitution, cell-based assays, mutagenesis\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — combined MD and reconstitution, single lab, mechanistic details partially computational\",\n      \"pmids\": [\"38324698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A homozygous missense mutation (V249M) in the PI3P/PI(3,5)P2-binding region of WIPI2 causes neurodevelopmental disorder. Functional studies show that the V231M WIPI2b mutant has significantly reduced binding to ATG16L1 (and ATG5-12) in GFP pulldown assays, and patient fibroblasts show reduced WIPI2 puncta, reduced LC3 lipidation, and reduced autophagic flux.\",\n      \"method\": \"GFP pulldown, patient fibroblast functional assay (LC3 lipidation, WIPI2 puncta, autophagic flux), whole-exome sequencing\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pulldown with disease mutant combined with patient-derived cell functional assays, single lab\",\n      \"pmids\": [\"30968111\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Freeze-fracture replica immunolabelling reveals WIPI2 as a membrane-integrated component of autophagosomes and the plasma membrane, and also detects WIPI2 in membranes near Golgi cisternae, identifying WIPI2 as a membrane protein of autophagosomal structures.\",\n      \"method\": \"Freeze-fracture replica immunolabelling electron microscopy\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization by specialized EM technique, single lab, single method\",\n      \"pmids\": [\"21564513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Dynamic and local phosphorylation of WIPI2 is a critical regulatory step in autophagosome biogenesis in neurons. The rate of WIPI2-dependent autophagosome formation declines significantly with age in axons of neurons from aged mice. Overexpression of WIPI2 rescues the age-dependent decline in autophagosome formation.\",\n      \"method\": \"Live-cell microscopy (axonal autophagosome formation), WIPI2 overexpression rescue, aged mouse neuron culture\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging with functional rescue by WIPI2 overexpression, single lab\",\n      \"pmids\": [\"31794336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Optineurin promotes recruitment of the ATG12-5-16L1 complex to WIPI2-positive phagophores, facilitating LC3-II production and autophagosome maturation. Optineurin interacts with ATG5 and the ATG12-5 conjugate; loss of optineurin reduces ATG12/16L1-positive puncta and their co-recruitment to WIPI2-positive phagophores, but does not reduce the number of WIPI2-positive phagophores.\",\n      \"method\": \"Co-immunoprecipitation, optineurin knockout mouse fibroblasts, fluorescence microscopy, LC3 lipidation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with KO cell functional assays and imaging, single lab, places optineurin downstream of WIPI2 in the pathway\",\n      \"pmids\": [\"29133525\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"WIPI2 is a PI3P-binding β-propeller (WD-repeat) protein that acts as a central hub in autophagosome biogenesis: upon autophagy induction, PI3P generated by PI3KC3-C1 recruits WIPI2 to phagophore membranes (on omegasomes, RAB11A-positive recycling endosomes, and damaged mitochondria), where WIPI2 allosterically activates the ATG12-5-16L1 E3-like complex (by binding ATG16L1 in an electropositive groove between β-propeller blades 2 and 3) to drive LC3/ATG8 lipidation; WIPI2 stability is controlled by mTORC1-mediated phosphorylation at Ser395 directing it to the HUWE1 E3 ligase for proteasomal degradation, and by CRL4-DDB1-mediated ubiquitination during mitosis; in antibacterial autophagy, TBK1 stabilizes WIPI2 on bacteria, and STING directly recruits WIPI2 via its FRRG motif to bypass canonical PI3P-dependent initiation; WIPI2 also promotes mitophagy by recruiting VCP/p97 to damaged mitochondria and interacts with the Nix MER domain during receptor-mediated mitophagy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"WIPI2 is a PI3P-binding β-propeller protein that serves as the central effector linking PI3P generation to LC3/ATG8 lipidation during autophagosome biogenesis [#1, #0]. Upon autophagy induction, PI3P produced on phagophore-associated membranes recruits WIPI2, which directly binds ATG16L1 and recruits the ATG12–5–16L1 E3-like complex to the phagophore to drive LC3 conjugation; ATG16L1 mutants that retain FIP200 binding but cannot bind WIPI2 fail to support starvation-induced autophagy [#0]. Complete reconstitution on giant unilamellar vesicles established that this recruitment is strictly PI3P-dependent and that WIPI2 allosterically activates the E3 complex—simply targeting the E3 to membranes is insufficient—while PI3KC3-C1 and WIPI2 reinforce each other's membrane recruitment in a positive feedback loop that accelerates lipidation kinetics [#3, #16]. Structurally, the ATG16L1 W2IR helix docks in an electropositive groove between WIPI2 β-propeller blades 2 and 3, and a second binding site (WBS2) conserved from yeast to mammals contributes to the interaction; both sites are required for normal autophagic flux [#2, #11]. WIPI2 is recruited to multiple membrane platforms including omegasomes and RAB11A-positive recycling endosomes, the latter serving as a primary platform for autophagosome formation and mitophagy [#1, #5]. WIPI2 abundance is tightly regulated: mTORC1 phosphorylates WIPI2 at Ser395 to direct it to the HUWE1 E3 ligase for proteasomal degradation, coupling nutrient status to autophagic capacity, and during mitosis CRL4–DDB1 ubiquitinates WIPI2 to suppress autophagy [#4, #6]. Beyond canonical starvation autophagy, WIPI2 mediates antibacterial autophagy of Salmonella downstream of TBK1 [#0, #8], is engaged by STING via competitive binding to its FRRG motif to drive PI3P-independent autophagy and cytoplasmic DNA clearance [#7], and promotes mitophagy by recruiting VCP/p97 to damaged mitochondria and interacting with the Nix MER domain [#9, #10]. A homozygous WIPI2 missense mutation in its phosphoinositide-binding region causes a neurodevelopmental disorder, with patient fibroblasts showing reduced ATG16L1 binding, LC3 lipidation, and autophagic flux [#17].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established the pathway position of the WIPI2 ortholog by showing it is required for ATG8 lipidation and recruitment of the conjugation machinery, defining a conserved role upstream of ATG8 conjugation.\",\n      \"evidence\": \"Genetic deletion, GFP-Atg8 imaging, and lipidation assays in yeast Atg21\",\n      \"pmids\": [\"15155809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define the direct binding partner mediating recruitment\", \"Yeast Cvt pathway context, not mammalian starvation autophagy\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Placed mammalian WIPI2 downstream of PI3P synthesis and upstream of autophagosome maturation, showing its loss arrests omegasome-stage structures.\",\n      \"evidence\": \"siRNA knockdown and co-localization imaging with autophagy markers in mammalian cells\",\n      \"pmids\": [\"20505359\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular partner of WIPI2 not yet identified\", \"Mechanism of E3 recruitment unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated the FRRG phosphoinositide-binding motif is required for ortholog function and that it scaffolds Atg8 and Atg16 localization while protecting Atg8-PE from premature Atg4 cleavage.\",\n      \"evidence\": \"FRRG motif mutagenesis and lipidation assays in yeast Atg21\",\n      \"pmids\": [\"20154084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect recruitment of Atg16 not distinguished here\", \"Yeast ortholog, mammalian relevance inferred\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified the direct WIPI2b–ATG16L1 interaction as the mechanism by which a PI3P effector recruits the E3-like conjugation complex, the key molecular link between PI3P and LC3 lipidation.\",\n      \"evidence\": \"Co-IP, pulldown, interface mutagenesis, ectopic membrane targeting, and depletion phenotypes for both starvation and Salmonella autophagy\",\n      \"pmids\": [\"24954904\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether WIPI2 merely tethers or allosterically activates the E3 not yet resolved\", \"Structural basis of interface unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined how the ortholog scaffolds both the E3 complex and Atg8 simultaneously, binding Atg16 via its coiled-coil and Atg8 via a non-AIM motif that leaves the AIM site free for Atg3.\",\n      \"evidence\": \"Co-IP, pulldown, yeast two-hybrid, and mutagenesis in yeast Atg21\",\n      \"pmids\": [\"25691244\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Membrane orientation of the scaffold not defined\", \"Mammalian Atg8 binding not directly tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected nutrient signaling to WIPI2 stability by showing mTORC1 phosphorylates Ser395 to trigger HUWE1-mediated degradation, providing a switch that gates autophagic capacity.\",\n      \"evidence\": \"In vitro kinase assay, phosphosite mapping, ubiquitination assay, and in vivo mouse liver fasting/HUWE1 silencing\",\n      \"pmids\": [\"30340022\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Ser395 phosphorylation promotes HUWE1 binding structurally unknown\", \"Other kinases/phosphatases not explored\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified RAB11A-positive recycling endosomes as a direct membrane platform for WIPI2 recruitment and autophagosome formation, broadening the membrane sources for canonical autophagy.\",\n      \"evidence\": \"Reciprocal Co-IP, live-cell imaging, and RAB11A knockout phenotyping\",\n      \"pmids\": [\"29634932\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of RAB11A vs omegasome platforms unquantified\", \"Whether RAB11A binding is direct or PI3P-mediated not fully resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Reconstitution proved that WIPI2 allosterically activates the ATG12-5-16L1 E3 and engages PI3KC3-C1 in positive feedback, distinguishing active catalysis from passive tethering.\",\n      \"evidence\": \"Complete LC3 lipidation reconstitution on GUVs with ectopic E3 targeting and feedback assays\",\n      \"pmids\": [\"32437499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of allosteric activation not defined here\", \"In vivo feedback kinetics not measured\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Localized the ortholog to the phagophore edge at the vacuole–isolation membrane contact site and established Atg16 binds the bottom face of the propeller, fixing the scaffold's membrane orientation.\",\n      \"evidence\": \"Crystal structure of Atg21–Atg16 coiled-coil, FRAP/FCCS imaging, and Vac8 deletion in yeast\",\n      \"pmids\": [\"32515645\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian VICS equivalent not established\", \"Vac8 mammalian counterpart unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided the atomic structure of the WIPI2d–ATG16L1 W2IR interface in the groove between blades 2 and 3, defining the WIPI1/2 W2IR subclass distinct from the WIPI3/4 ATG2-binding subclass.\",\n      \"evidence\": \"1.85 Å crystal structure with interface mutagenesis validated in vitro and in cells\",\n      \"pmids\": [\"34505572\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Second binding site not yet characterized\", \"Conformational changes upon membrane binding not captured\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a second ATG16L1 binding site (WBS2) conserved across evolution, showing the WIPI2–ATG16L1 interaction is bipartite and both sites are needed for flux.\",\n      \"evidence\": \"Crystal structures of both WBS1 and WBS2 complexes, ITC, and cell-based flux assays\",\n      \"pmids\": [\"37165562\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional cooperativity between the two sites not quantified\", \"Whether both engage simultaneously on membranes unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established a non-canonical, PI3P-independent recruitment route via STING competing with PI3P for the WIPI2 FRRG motif, linking WIPI2 to innate immune DNA clearance.\",\n      \"evidence\": \"Co-IP, FRRG mutagenesis, competition binding, and cytoplasmic DNA clearance assays\",\n      \"pmids\": [\"36872914\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of STING–FRRG binding not solved\", \"In vivo relevance of mutual inhibition not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified direct recruitment of WIPI2 to mitochondria by the Nix MER domain independent of the LIR motif, defining a receptor-driven route for WIPI2 in mitophagy.\",\n      \"evidence\": \"Chemically induced dimerization, Co-IP, imaging, and mitophagy assays\",\n      \"pmids\": [\"37621214\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, not independently confirmed\", \"Structural basis of MER–WIPI2 binding unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved the stepwise mechanics of LC3 lipidation downstream of WIPI2 recruitment, defining membrane engagement by ATG16L1 and ATG3 and PE concentration at the catalytic site.\",\n      \"evidence\": \"Molecular dynamics simulations combined with in vitro reconstitution and cell-based assays\",\n      \"pmids\": [\"38324698\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic details partly computational\", \"Catalytic histidine roles not validated by structure\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked WIPI2 dysfunction to human disease, showing a phosphoinositide-binding region mutation impairs ATG16L1 binding and autophagy and causes a neurodevelopmental disorder.\",\n      \"evidence\": \"Whole-exome sequencing, GFP pulldown of disease mutant, and patient fibroblast functional assays\",\n      \"pmids\": [\"30968111\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single family/patient cohort\", \"Tissue-specific mechanism of neurodevelopmental phenotype unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple competing recruitment routes (PI3P, STING, RAB11A, Nix MER), the dual ATG16L1 sites, and the layered degradation controls are integrated to set the timing and location of autophagosome formation in different physiological contexts remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model coordinating recruitment platforms\", \"Crosstalk between mTORC1/HUWE1 and CRL4 degradation pathways unknown\", \"Cell-type-specific contributions, e.g. in neurons, not mechanistically dissected\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1, 3, 13, 14]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2, 11, 14]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005776\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [7, 8]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ATG16L1\", \"RAB11A\", \"HUWE1\", \"DDB1\", \"STING1\", \"VCP\", \"BNIP3L\", \"OPTN\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}