{"gene":"INPP5B","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":1998,"finding":"Inpp5b encodes a phosphatidylinositol bisphosphate 5-phosphatase that has functionally overlapping activity with Ocrl1 in vivo; double knockout of both Ocrl1 and Inpp5b causes early embryonic lethality in mice, whereas single Inpp5b knockout mice are viable but show testicular degeneration in males, demonstrating that Inpp5b provides compensatory PI(4,5)P2 5-phosphatase activity in the absence of Ocrl1.","method":"Targeted gene disruption in mice (single and double knockout), genetic epistasis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockout with defined phenotypic readout, replicated across multiple crosses and independently confirmed by subsequent studies","pmids":["9593760"],"is_preprint":false},{"year":2007,"finding":"INPP5B localizes to the early secretory pathway (Golgi apparatus and ERGIC) via binding to specific RAB proteins; mutational analysis showed RAB binding is required for efficient Golgi targeting. Unlike OCRL1, INPP5B does not interact with clathrin or alpha-adaptin. Expression of INPP5B (but not OCRL1) causes accumulation of ERGIC53 in the ERGIC under conditions that block retrograde transport, indicating a role for INPP5B in retrograde ERGIC-to-ER transport.","method":"Subcellular fractionation, immunofluorescence localization, mutational analysis, co-immunoprecipitation with RAB proteins, brefeldin A and low-temperature transport assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional consequence, mutational analysis of RAB-binding domain, single lab with multiple orthogonal methods","pmids":["17956944"],"is_preprint":false},{"year":2009,"finding":"INPP5B cannot rescue OCRL1-dependent cell migration and spreading defects in Lowe syndrome patient fibroblasts, in contrast to wild-type OCRL1; this functional non-equivalence is linked to the absence of AP2/clathrin binding by INPP5B, as OCRL1 variants lacking AP2/clathrin binding are similarly unable to rescue. INPP5B therefore lacks the ruffle-mediated membrane remodeling function of OCRL1.","method":"Rescue experiments in patient-derived fibroblasts with wild-type and mutant constructs, cell migration and spreading assays, phosphatase-dead mutant controls","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional rescue experiments in patient fibroblasts with multiple construct variants, single lab","pmids":["19700499"],"is_preprint":false},{"year":2011,"finding":"OCRL and Inpp5B are recruited to nascent phagosomes as Rab5 effectors via the adaptor protein APPL1, where they hydrolyze PtdIns(4,5)P2; knockdown of APPL1 or inhibition of Rab5 impairs phagosomal recruitment of both phosphatases, prolongs PtdIns(4,5)P2 and actin presence on phagosomal membranes, and accentuates Akt activation.","method":"Knockdown (siRNA), live-cell imaging of phosphoinositide dynamics, co-immunoprecipitation, dominant-negative Rab5, phagocytosis assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional data with knockdown of multiple pathway components, replicated with pharmacological inhibition and imaging of lipid dynamics","pmids":["22072788"],"is_preprint":false},{"year":2001,"finding":"Inpp5b is expressed in Sertoli cells and epididymal epithelial cells; its deficiency in these somatic cells (not in spermatids themselves, as shown by conditional knockout) causes reduced sperm motility, impaired sperm-egg membrane fusion, and defective proteolytic processing of fertilin beta (ADAM2) during epididymal sperm maturation, revealing a role for phosphoinositides in sperm maturation.","method":"Conditional and germline knockout mice, in vitro fertilization assays, immunoblotting for ADAM2 processing, sperm motility analysis","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockout dissects cell-type-specific function, multiple orthogonal phenotypic readouts, replicated in subsequent study (PMID:20403911)","pmids":["11784089"],"is_preprint":false},{"year":2010,"finding":"In Inpp5b-null sperm, ADAM2 and ADAM3 proteolytic cleavage are only modestly and variably impaired between individual males; reduced fertilization correlates with impaired sperm binding to and fusion with the egg plasma membrane; IZUMO1 localization appears normal in Inpp5b-null sperm, indicating the fusion defect is not due to mislocalization of this fusogen.","method":"In vitro fertilization assays, mating trials, immunofluorescence for IZUMO1, immunoblotting for ADAM2/ADAM3, multivariate correlation analysis","journal":"Molecular human reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple phenotypic endpoints analyzed per individual animal, single lab, partially refines prior findings","pmids":["20403911"],"is_preprint":false},{"year":2013,"finding":"INPP5B localizes to primary cilia in human retinal pigmented epithelial cells; silencing INPP5B causes defects in cilia formation in cultured cells and in zebrafish Kupffer's vesicles (inpp5b morphants), and impairs cilia-dependent melanosome transport, demonstrating a functional role for INPP5B in primary ciliogenesis.","method":"siRNA knockdown with immunofluorescence, morpholino knockdown in zebrafish, cilia formation assay, melanosome transport assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function in two distinct systems (cultured cells and zebrafish) with defined cellular phenotype, single lab","pmids":["23805271"],"is_preprint":false},{"year":2016,"finding":"Kidney tubule-specific inactivation of Inpp5b on a global Ocrl-knockout background causes low molecular weight proteinuria, phosphaturia, and acidemia, with striking impairment of both clathrin-dependent and clathrin-independent endocytosis in proximal tubules, phenocopying Dent disease. This establishes that OCRL and INPP5B have redundant functions in maintaining proximal tubule endocytic function.","method":"Conditional double knockout mice (kidney tubule-specific Inpp5b KO on Ocrl-null background), urine biochemistry, electron microscopy, endocytosis assays in proximal tubule cells","journal":"Journal of the American Society of Nephrology","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific conditional double knockout with defined biochemical and cellular phenotypic readouts, mechanistic connection to endocytosis established","pmids":["27895154"],"is_preprint":false},{"year":2021,"finding":"Rab5 recruits OCRL and Inpp5b to circular membrane ruffles via APPL1, where the phosphatases hydrolyze PtdIns(4,5)P2 to promote macropinosome sealing and scission; knockdown of both phosphatases or APPL1 prevents macropinosome closure without affecting ruffle formation, indicating the phosphatases act downstream of ruffling specifically at the sealing step.","method":"siRNA knockdown of OCRL/Inpp5b and APPL1, live-cell imaging of PtdIns(4,5)P2 dynamics, dominant-negative Rab5, SNARE inhibition, phosphatidylinositol-4-phosphate 5-kinase overexpression","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple complementary loss-of-function approaches, real-time lipid dynamics imaging, epistatic dissection of pathway steps","pmids":["33722976"],"is_preprint":false},{"year":2022,"finding":"INPP5B regulates B cell receptor (BCR) clustering and downstream signaling by dephosphorylating PI(4,5)P2 at the plasma membrane upon antigen stimulation; PI(4,5)P2 hydrolysis by INPP5B promotes actin disassembly via cofilin severing and reduces actin-plasma membrane linkage via ezrin, enabling BCR mobilization and cell spreading.","method":"INPP5B knockdown and knockout in B cells, BCR clustering assays, PI(4,5)P2 imaging, actin dynamics measurements, cofilin and ezrin functional assays, antigen-coated surface spreading assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with multiple orthogonal mechanistic readouts (lipid dynamics, actin regulators, receptor clustering), defined signaling pathway placement","pmids":["35878408"],"is_preprint":false},{"year":2025,"finding":"NIK (NF-κB-inducing kinase) stabilizes INPP5B by recruiting it into the APPL1 adaptor complex, thereby reducing INPP5B ubiquitination and proteasomal degradation; stabilized INPP5B suppresses AKT signaling to reduce ACLY-mediated lipogenesis in liver during chronic ethanol exposure.","method":"Co-immunoprecipitation, immunoblotting for ubiquitination, NIK hepatocyte-specific knockout mice, transcriptomics and proteomics, loss-of-function in vivo and in vitro","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and ubiquitination assays demonstrate stabilization mechanism, single lab, confirmed in vivo and in vitro","pmids":["41391683"],"is_preprint":false},{"year":2026,"finding":"PCIF1 knockdown upregulates INPP5B, causing accumulation of PI(3,4)P2 and enhanced AKT activation in glioblastoma cells; this indicates that INPP5B, as a lipid 5-phosphatase, influences PI(3,4)P2 levels and thereby modulates AKT-dependent cell migration and invasion.","method":"PCIF1 knockdown/overexpression, PI(3,4)P2 measurement, immunoblotting for AKT activation, cell migration and invasion assays","journal":"Acta biochimica et biophysica Sinica","confidence":"Low","confidence_rationale":"Tier 3 / Weak — INPP5B-specific mechanism inferred from PCIF1 manipulation context; single lab, indirect evidence linking INPP5B to PI(3,4)P2 accumulation","pmids":["42145053"],"is_preprint":false},{"year":1994,"finding":"The INPP5B gene (encoding the 75-kDa type II inositol polyphosphate-5-phosphatase originally described in platelets) was mapped to human chromosome band 1p34 using somatic cell hybrids and fluorescence in situ hybridization; the enzyme dephosphorylates inositol-1,4,5-trisphosphate (IP3) to inositol-1,4-bisphosphate (IP2).","method":"Somatic cell hybrid panel, fluorescence in situ hybridization, enzymatic characterization","journal":"Cytogenetics and cell genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct chromosomal mapping and enzymatic substrate identification, but foundational characterization only","pmids":["8125013"],"is_preprint":false}],"current_model":"INPP5B is a PI(4,5)P2-preferring inositol 5-phosphatase that is stabilized by NIK via the APPL1 complex (protecting it from ubiquitin-mediated degradation), localizes to the Golgi/ERGIC via RAB-protein interactions, and is recruited to phagosomes and macropinosome-forming ruffles as a Rab5 effector through APPL1, where it hydrolyzes PI(4,5)P2 to drive membrane remodeling events including phagosome/macropinosome sealing, BCR clustering via cofilin/ezrin-dependent actin disassembly, and primary ciliogenesis; in somatic reproductive tissues (Sertoli cells and epididymis) it regulates ADAM protease processing required for sperm maturation and fertility, and it functionally overlaps with the paralog OCRL in renal proximal tubule endocytosis and early embryonic development, though it cannot substitute for OCRL1 in clathrin/AP2-dependent ruffle-mediated membrane remodeling."},"narrative":{"mechanistic_narrative":"INPP5B is an inositol polyphosphate 5-phosphatase that hydrolyzes PI(4,5)P2 (and the soluble substrate IP3 to IP2) to drive membrane remodeling and receptor signaling across multiple cellular contexts [PMID:8125013, PMID:35878408]. It is recruited as a Rab5 effector through the adaptor APPL1 to nascent phagosomes and to circular membrane ruffles, where PI(4,5)P2 hydrolysis terminates actin assembly and enables phagosome and macropinosome sealing/scission; loss of the phosphatase or APPL1 prolongs PI(4,5)P2 and actin retention and accentuates Akt activation [PMID:22072788, PMID:33722976]. At the B cell plasma membrane, antigen-triggered PI(4,5)P2 dephosphorylation by INPP5B promotes cofilin-mediated actin severing and reduces ezrin-dependent actin–membrane linkage, mobilizing BCR clustering and cell spreading [PMID:35878408]. INPP5B also localizes to the early secretory pathway (Golgi/ERGIC) via RAB-protein binding and functions in retrograde ERGIC-to-ER transport, and to primary cilia where it is required for ciliogenesis [PMID:17956944, PMID:23805271]. It functionally overlaps with the paralog OCRL: combined loss is embryonic lethal, and tubule-specific inactivation on an Ocrl-null background impairs proximal tubule endocytosis and phenocopies Dent disease, yet INPP5B cannot substitute for OCRL1 in clathrin/AP2-dependent ruffle-mediated remodeling because it lacks clathrin/AP2 binding [PMID:9593760, PMID:27895154, PMID:19700499]. In reproductive somatic tissues, INPP5B activity in Sertoli and epididymal cells is required for sperm maturation, motility, and sperm–egg fusion, with effects on ADAM protease processing [PMID:11784089, PMID:20403911]. Stability of INPP5B is controlled by NIK, which recruits it into the APPL1 complex to limit ubiquitin-dependent degradation [PMID:41391683].","teleology":[{"year":1994,"claim":"Establishing the molecular identity and catalytic activity of INPP5B answered what the gene encodes — a 5-phosphatase acting on inositol phosphates.","evidence":"Chromosomal mapping by somatic cell hybrids/FISH plus enzymatic substrate characterization (IP3 to IP2)","pmids":["8125013"],"confidence":"Medium","gaps":["Does not address membrane phosphoinositide substrates","No cellular localization or pathway context"]},{"year":1998,"claim":"Genetic knockouts answered whether INPP5B has an essential in vivo role and how it relates to its paralog, revealing redundancy with Ocrl1 and a non-redundant requirement in testis.","evidence":"Single and double Inpp5b/Ocrl1 knockout mice with epistasis analysis","pmids":["9593760"],"confidence":"High","gaps":["Molecular basis of compensation not defined","Cell-type origin of testicular defect unresolved"]},{"year":2001,"claim":"Conditional knockouts answered where in the reproductive system INPP5B acts, localizing the requirement to somatic Sertoli/epididymal cells rather than germ cells and linking it to ADAM2 processing.","evidence":"Conditional and germline knockout mice, IVF assays, ADAM2 immunoblotting, motility analysis","pmids":["11784089"],"confidence":"High","gaps":["Direct phosphoinositide substrate in epididymis not measured","Mechanism connecting lipid phosphatase to protease processing unclear"]},{"year":2007,"claim":"Localization and RAB-binding analysis answered where INPP5B operates in the secretory system and how it differs from OCRL1, placing it at the Golgi/ERGIC in retrograde transport.","evidence":"Fractionation, immunofluorescence, RAB co-IP, BFA and low-temperature transport assays, mutational analysis","pmids":["17956944"],"confidence":"Medium","gaps":["Which RAB(s) mediate targeting not fully resolved","Single-lab observation"]},{"year":2009,"claim":"Rescue experiments answered why INPP5B cannot replace OCRL1 in Lowe syndrome cells, tracing functional non-equivalence to the absence of AP2/clathrin binding.","evidence":"Rescue in patient fibroblasts with WT/mutant constructs, migration/spreading assays, phosphatase-dead controls","pmids":["19700499"],"confidence":"Medium","gaps":["Structural basis of differential adaptor binding not defined","Single lab"]},{"year":2011,"claim":"Phagosome studies answered how INPP5B is targeted to dynamic membranes, identifying APPL1-mediated recruitment as a Rab5 effector that controls PI(4,5)P2 and actin clearance.","evidence":"siRNA knockdown, live imaging of phosphoinositide dynamics, co-IP, dominant-negative Rab5, phagocytosis assays","pmids":["22072788"],"confidence":"High","gaps":["Relative contributions of OCRL vs INPP5B not separated","Direct phosphatase–APPL1 contact not mapped"]},{"year":2013,"claim":"Ciliogenesis assays answered whether INPP5B has a role beyond endosomal trafficking, establishing a requirement in primary cilium formation across cells and zebrafish.","evidence":"siRNA knockdown, zebrafish morpholino, cilia formation and melanosome transport assays","pmids":["23805271"],"confidence":"Medium","gaps":["Phosphoinositide substrate at cilium not defined","Morpholino-based zebrafish data"]},{"year":2016,"claim":"Tubule-specific double knockouts answered the physiological consequence of OCRL/INPP5B redundancy in kidney, showing combined loss impairs proximal tubule endocytosis and phenocopies Dent disease.","evidence":"Kidney tubule-specific Inpp5b KO on Ocrl-null background, urine biochemistry, EM, endocytosis assays","pmids":["27895154"],"confidence":"High","gaps":["INPP5B-specific contribution distinct from OCRL not isolated","Endocytic substrate selectivity not mapped"]},{"year":2021,"claim":"Macropinocytosis imaging answered the precise step at which the phosphatases act, placing PI(4,5)P2 hydrolysis downstream of ruffle formation at the sealing/scission step.","evidence":"siRNA of OCRL/Inpp5b and APPL1, live PI(4,5)P2 imaging, dominant-negative Rab5, SNARE inhibition, PIP5K overexpression","pmids":["33722976"],"confidence":"High","gaps":["INPP5B vs OCRL functional division not resolved","Scission machinery linkage not detailed"]},{"year":2022,"claim":"B cell studies answered how INPP5B couples PI(4,5)P2 turnover to receptor signaling, linking dephosphorylation to cofilin/ezrin-dependent actin remodeling and BCR clustering.","evidence":"Knockdown/knockout in B cells, BCR clustering and spreading assays, PI(4,5)P2 imaging, cofilin/ezrin functional assays","pmids":["35878408"],"confidence":"High","gaps":["Recruitment mechanism to BCR sites not defined","In vivo immune consequence not tested"]},{"year":2025,"claim":"Stability studies answered how INPP5B protein levels are controlled, identifying NIK-driven recruitment into APPL1 as a mechanism limiting ubiquitin-dependent degradation with downstream effects on AKT/lipogenesis.","evidence":"Co-IP, ubiquitination immunoblotting, NIK hepatocyte-specific KO mice, omics, in vivo and in vitro loss-of-function","pmids":["41391683"],"confidence":"Medium","gaps":["E3 ligase targeting INPP5B not identified","Single lab"]},{"year":2026,"claim":"PCIF1 manipulation studies raised the possibility that INPP5B influences PI(3,4)P2 levels and AKT-dependent invasion in glioblastoma.","evidence":"PCIF1 knockdown/overexpression, PI(3,4)P2 measurement, AKT immunoblotting, migration/invasion assays","pmids":["42145053"],"confidence":"Low","gaps":["INPP5B-specific mechanism inferred indirectly from PCIF1 context","Direct PI(3,4)P2 phosphatase activity of INPP5B not demonstrated here","Single lab"]},{"year":null,"claim":"How the division of labor between INPP5B and OCRL is established at distinct membranes, and what determines INPP5B substrate selectivity in vivo, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of INPP5B substrate/adaptor selectivity","Tissue-specific substrate preference (PI(4,5)P2 vs PI(3,4)P2 vs IP3) not systematically mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[12,3,8,9]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[12]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[9]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[3,8,7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9,3]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[9,8]}],"complexes":["APPL1 complex"],"partners":["APPL1","RAB5","OCRL","NIK"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P32019","full_name":"Type II inositol 1,4,5-trisphosphate 5-phosphatase","aliases":["75 kDa inositol polyphosphate-5-phosphatase","Phosphoinositide 5-phosphatase","5PTase"],"length_aa":993,"mass_kda":112.9,"function":"Regulates phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) cellular levels by cleaving the phosphate at the 5-position producing PtdIns(4)P. Also hydrolyzes the 5-position phosphate from inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), thereby modulating cellular signaling events","subcellular_location":"Cytoplasm, cytosol; Endoplasmic reticulum-Golgi intermediate compartment; Early endosome membrane; Membrane; Cytoplasmic vesicle, phagosome membrane; Golgi apparatus","url":"https://www.uniprot.org/uniprotkb/P32019/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/INPP5B","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/INPP5B","total_profiled":1310},"omim":[{"mim_id":"614240","title":"PH DOMAIN-CONTAINING ENDOCYTIC TRAFFICKING ADAPTOR 2; PHETA2","url":"https://www.omim.org/entry/614240"},{"mim_id":"614239","title":"PH DOMAIN-CONTAINING ENDOCYTIC TRAFFICKING ADAPTOR 1; PHETA1","url":"https://www.omim.org/entry/614239"},{"mim_id":"601582","title":"INOSITOL POLYPHOSPHATE-5-PHOSPHATASE, 145-KD; INPP5D","url":"https://www.omim.org/entry/601582"},{"mim_id":"300535","title":"OCRL INOSITOL POLYPHOSPHATE-5-PHOSPHATASE; OCRL","url":"https://www.omim.org/entry/300535"},{"mim_id":"147264","title":"INOSITOL POLYPHOSPHATE-5-PHOSPHATASE, 75-KD; INPP5B","url":"https://www.omim.org/entry/147264"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Primary cilium tip","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/INPP5B"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P32019","domains":[{"cath_id":"2.30.29.110","chopping":"4-131","consensus_level":"high","plddt":83.6741,"start":4,"end":131},{"cath_id":"3.60.10.10","chopping":"345-646","consensus_level":"medium","plddt":94.503,"start":345,"end":646},{"cath_id":"2.60.40.10","chopping":"671-780","consensus_level":"high","plddt":94.2978,"start":671,"end":780},{"cath_id":"1.10.555.10","chopping":"827-991","consensus_level":"medium","plddt":91.0042,"start":827,"end":991}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P32019","model_url":"https://alphafold.ebi.ac.uk/files/AF-P32019-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P32019-F1-predicted_aligned_error_v6.png","plddt_mean":79.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=INPP5B","jax_strain_url":"https://www.jax.org/strain/search?query=INPP5B"},"sequence":{"accession":"P32019","fasta_url":"https://rest.uniprot.org/uniprotkb/P32019.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P32019/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P32019"}},"corpus_meta":[{"pmid":"9593760","id":"PMC_9593760","title":"Functional overlap between murine Inpp5b and Ocrl1 may explain why deficiency of the murine ortholog for OCRL1 does not cause Lowe syndrome in mice.","date":"1998","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/9593760","citation_count":137,"is_preprint":false},{"pmid":"22072788","id":"PMC_22072788","title":"Recruitment of OCRL and Inpp5B to phagosomes by Rab5 and APPL1 depletes phosphoinositides and attenuates Akt signaling.","date":"2011","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/22072788","citation_count":115,"is_preprint":false},{"pmid":"19700499","id":"PMC_19700499","title":"Lowe syndrome patient fibroblasts display Ocrl1-specific cell migration defects that cannot be rescued by the homologous Inpp5b phosphatase.","date":"2009","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19700499","citation_count":47,"is_preprint":false},{"pmid":"17956944","id":"PMC_17956944","title":"Targeting of the type II inositol polyphosphate 5-phosphatase INPP5B to the early secretory pathway.","date":"2007","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/17956944","citation_count":43,"is_preprint":false},{"pmid":"23805271","id":"PMC_23805271","title":"Compensatory Role of Inositol 5-Phosphatase INPP5B to OCRL in Primary Cilia Formation in Oculocerebrorenal Syndrome of Lowe.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23805271","citation_count":41,"is_preprint":false},{"pmid":"11784089","id":"PMC_11784089","title":"Disrupted sperm function and fertilin beta processing in mice deficient in the inositol polyphosphate 5-phosphatase Inpp5b.","date":"2001","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/11784089","citation_count":36,"is_preprint":false},{"pmid":"20872266","id":"PMC_20872266","title":"Species-specific difference in expression and splice-site choice in Inpp5b, an inositol polyphosphate 5-phosphatase paralogous to the enzyme deficient in Lowe Syndrome.","date":"2010","source":"Mammalian genome : official journal of the International Mammalian Genome Society","url":"https://pubmed.ncbi.nlm.nih.gov/20872266","citation_count":33,"is_preprint":false},{"pmid":"25305077","id":"PMC_25305077","title":"OCRL-mutated fibroblasts from patients with Dent-2 disease exhibit INPP5B-independent phenotypic variability relatively to Lowe syndrome cells.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25305077","citation_count":31,"is_preprint":false},{"pmid":"33722976","id":"PMC_33722976","title":"Rab5 regulates macropinocytosis by recruiting the inositol 5-phosphatases OCRL and Inpp5b that hydrolyse PtdIns(4,5)P2.","date":"2021","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/33722976","citation_count":30,"is_preprint":false},{"pmid":"27895154","id":"PMC_27895154","title":"Kidney Tubular Ablation of Ocrl/Inpp5b Phenocopies Lowe Syndrome Tubulopathy.","date":"2016","source":"Journal of the American Society of Nephrology : JASN","url":"https://pubmed.ncbi.nlm.nih.gov/27895154","citation_count":24,"is_preprint":false},{"pmid":"20403911","id":"PMC_20403911","title":"Multivariate analysis of male reproductive function in Inpp5b-/- mice reveals heterogeneity in defects in fertility, sperm-egg membrane interaction and proteolytic cleavage of sperm ADAMs.","date":"2010","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/20403911","citation_count":19,"is_preprint":false},{"pmid":"35878408","id":"PMC_35878408","title":"The inositol 5-phosphatase INPP5B regulates B cell receptor clustering and signaling.","date":"2022","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/35878408","citation_count":11,"is_preprint":false},{"pmid":"20195868","id":"PMC_20195868","title":"X-inactivation analysis of embryonic lethality in Ocrl wt/-; Inpp5b-/- mice.","date":"2010","source":"Mammalian genome : official journal of the International Mammalian Genome Society","url":"https://pubmed.ncbi.nlm.nih.gov/20195868","citation_count":11,"is_preprint":false},{"pmid":"8125013","id":"PMC_8125013","title":"Localization of the 75-kDa inositol polyphosphate-5-phosphatase (INPP5B) to human chromosome band 1p34.","date":"1994","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8125013","citation_count":7,"is_preprint":false},{"pmid":"8530037","id":"PMC_8530037","title":"Mapping of the 75-kDa inositol polyphosphate-5-phosphatase (Inpp5b) to distal mouse chromosome 4 and its exclusion as a candidate gene for dysgenetic lens.","date":"1995","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8530037","citation_count":6,"is_preprint":false},{"pmid":"40618840","id":"PMC_40618840","title":"The inositol 5-phosphatases OCRL and INPP5B: Cellular functions and roles in disease.","date":"2025","source":"Biochimica et biophysica acta. Molecular and cell biology of lipids","url":"https://pubmed.ncbi.nlm.nih.gov/40618840","citation_count":3,"is_preprint":false},{"pmid":"41391683","id":"PMC_41391683","title":"NIK suppresses AKT/ACLY pathway-mediated lipogenesis in liver by stabilizing INPP5B during chronic ethanol exposure.","date":"2025","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41391683","citation_count":1,"is_preprint":false},{"pmid":"42145053","id":"PMC_42145053","title":"PCIF1 modulates glioblastoma cell migration and invasion by altering PI(3,4)P2 levels through the PI5-phosphatase INPP5B.","date":"2026","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/42145053","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10778,"output_tokens":3654,"usd":0.043572,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11327,"output_tokens":3950,"usd":0.077692,"stage2_stop_reason":"end_turn"},"total_usd":0.121264,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"Inpp5b encodes a phosphatidylinositol bisphosphate 5-phosphatase that has functionally overlapping activity with Ocrl1 in vivo; double knockout of both Ocrl1 and Inpp5b causes early embryonic lethality in mice, whereas single Inpp5b knockout mice are viable but show testicular degeneration in males, demonstrating that Inpp5b provides compensatory PI(4,5)P2 5-phosphatase activity in the absence of Ocrl1.\",\n      \"method\": \"Targeted gene disruption in mice (single and double knockout), genetic epistasis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockout with defined phenotypic readout, replicated across multiple crosses and independently confirmed by subsequent studies\",\n      \"pmids\": [\"9593760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"INPP5B localizes to the early secretory pathway (Golgi apparatus and ERGIC) via binding to specific RAB proteins; mutational analysis showed RAB binding is required for efficient Golgi targeting. Unlike OCRL1, INPP5B does not interact with clathrin or alpha-adaptin. Expression of INPP5B (but not OCRL1) causes accumulation of ERGIC53 in the ERGIC under conditions that block retrograde transport, indicating a role for INPP5B in retrograde ERGIC-to-ER transport.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence localization, mutational analysis, co-immunoprecipitation with RAB proteins, brefeldin A and low-temperature transport assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional consequence, mutational analysis of RAB-binding domain, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"17956944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"INPP5B cannot rescue OCRL1-dependent cell migration and spreading defects in Lowe syndrome patient fibroblasts, in contrast to wild-type OCRL1; this functional non-equivalence is linked to the absence of AP2/clathrin binding by INPP5B, as OCRL1 variants lacking AP2/clathrin binding are similarly unable to rescue. INPP5B therefore lacks the ruffle-mediated membrane remodeling function of OCRL1.\",\n      \"method\": \"Rescue experiments in patient-derived fibroblasts with wild-type and mutant constructs, cell migration and spreading assays, phosphatase-dead mutant controls\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue experiments in patient fibroblasts with multiple construct variants, single lab\",\n      \"pmids\": [\"19700499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"OCRL and Inpp5B are recruited to nascent phagosomes as Rab5 effectors via the adaptor protein APPL1, where they hydrolyze PtdIns(4,5)P2; knockdown of APPL1 or inhibition of Rab5 impairs phagosomal recruitment of both phosphatases, prolongs PtdIns(4,5)P2 and actin presence on phagosomal membranes, and accentuates Akt activation.\",\n      \"method\": \"Knockdown (siRNA), live-cell imaging of phosphoinositide dynamics, co-immunoprecipitation, dominant-negative Rab5, phagocytosis assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional data with knockdown of multiple pathway components, replicated with pharmacological inhibition and imaging of lipid dynamics\",\n      \"pmids\": [\"22072788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Inpp5b is expressed in Sertoli cells and epididymal epithelial cells; its deficiency in these somatic cells (not in spermatids themselves, as shown by conditional knockout) causes reduced sperm motility, impaired sperm-egg membrane fusion, and defective proteolytic processing of fertilin beta (ADAM2) during epididymal sperm maturation, revealing a role for phosphoinositides in sperm maturation.\",\n      \"method\": \"Conditional and germline knockout mice, in vitro fertilization assays, immunoblotting for ADAM2 processing, sperm motility analysis\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockout dissects cell-type-specific function, multiple orthogonal phenotypic readouts, replicated in subsequent study (PMID:20403911)\",\n      \"pmids\": [\"11784089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In Inpp5b-null sperm, ADAM2 and ADAM3 proteolytic cleavage are only modestly and variably impaired between individual males; reduced fertilization correlates with impaired sperm binding to and fusion with the egg plasma membrane; IZUMO1 localization appears normal in Inpp5b-null sperm, indicating the fusion defect is not due to mislocalization of this fusogen.\",\n      \"method\": \"In vitro fertilization assays, mating trials, immunofluorescence for IZUMO1, immunoblotting for ADAM2/ADAM3, multivariate correlation analysis\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple phenotypic endpoints analyzed per individual animal, single lab, partially refines prior findings\",\n      \"pmids\": [\"20403911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"INPP5B localizes to primary cilia in human retinal pigmented epithelial cells; silencing INPP5B causes defects in cilia formation in cultured cells and in zebrafish Kupffer's vesicles (inpp5b morphants), and impairs cilia-dependent melanosome transport, demonstrating a functional role for INPP5B in primary ciliogenesis.\",\n      \"method\": \"siRNA knockdown with immunofluorescence, morpholino knockdown in zebrafish, cilia formation assay, melanosome transport assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function in two distinct systems (cultured cells and zebrafish) with defined cellular phenotype, single lab\",\n      \"pmids\": [\"23805271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Kidney tubule-specific inactivation of Inpp5b on a global Ocrl-knockout background causes low molecular weight proteinuria, phosphaturia, and acidemia, with striking impairment of both clathrin-dependent and clathrin-independent endocytosis in proximal tubules, phenocopying Dent disease. This establishes that OCRL and INPP5B have redundant functions in maintaining proximal tubule endocytic function.\",\n      \"method\": \"Conditional double knockout mice (kidney tubule-specific Inpp5b KO on Ocrl-null background), urine biochemistry, electron microscopy, endocytosis assays in proximal tubule cells\",\n      \"journal\": \"Journal of the American Society of Nephrology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific conditional double knockout with defined biochemical and cellular phenotypic readouts, mechanistic connection to endocytosis established\",\n      \"pmids\": [\"27895154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Rab5 recruits OCRL and Inpp5b to circular membrane ruffles via APPL1, where the phosphatases hydrolyze PtdIns(4,5)P2 to promote macropinosome sealing and scission; knockdown of both phosphatases or APPL1 prevents macropinosome closure without affecting ruffle formation, indicating the phosphatases act downstream of ruffling specifically at the sealing step.\",\n      \"method\": \"siRNA knockdown of OCRL/Inpp5b and APPL1, live-cell imaging of PtdIns(4,5)P2 dynamics, dominant-negative Rab5, SNARE inhibition, phosphatidylinositol-4-phosphate 5-kinase overexpression\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple complementary loss-of-function approaches, real-time lipid dynamics imaging, epistatic dissection of pathway steps\",\n      \"pmids\": [\"33722976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"INPP5B regulates B cell receptor (BCR) clustering and downstream signaling by dephosphorylating PI(4,5)P2 at the plasma membrane upon antigen stimulation; PI(4,5)P2 hydrolysis by INPP5B promotes actin disassembly via cofilin severing and reduces actin-plasma membrane linkage via ezrin, enabling BCR mobilization and cell spreading.\",\n      \"method\": \"INPP5B knockdown and knockout in B cells, BCR clustering assays, PI(4,5)P2 imaging, actin dynamics measurements, cofilin and ezrin functional assays, antigen-coated surface spreading assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with multiple orthogonal mechanistic readouts (lipid dynamics, actin regulators, receptor clustering), defined signaling pathway placement\",\n      \"pmids\": [\"35878408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NIK (NF-κB-inducing kinase) stabilizes INPP5B by recruiting it into the APPL1 adaptor complex, thereby reducing INPP5B ubiquitination and proteasomal degradation; stabilized INPP5B suppresses AKT signaling to reduce ACLY-mediated lipogenesis in liver during chronic ethanol exposure.\",\n      \"method\": \"Co-immunoprecipitation, immunoblotting for ubiquitination, NIK hepatocyte-specific knockout mice, transcriptomics and proteomics, loss-of-function in vivo and in vitro\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and ubiquitination assays demonstrate stabilization mechanism, single lab, confirmed in vivo and in vitro\",\n      \"pmids\": [\"41391683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"PCIF1 knockdown upregulates INPP5B, causing accumulation of PI(3,4)P2 and enhanced AKT activation in glioblastoma cells; this indicates that INPP5B, as a lipid 5-phosphatase, influences PI(3,4)P2 levels and thereby modulates AKT-dependent cell migration and invasion.\",\n      \"method\": \"PCIF1 knockdown/overexpression, PI(3,4)P2 measurement, immunoblotting for AKT activation, cell migration and invasion assays\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — INPP5B-specific mechanism inferred from PCIF1 manipulation context; single lab, indirect evidence linking INPP5B to PI(3,4)P2 accumulation\",\n      \"pmids\": [\"42145053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"The INPP5B gene (encoding the 75-kDa type II inositol polyphosphate-5-phosphatase originally described in platelets) was mapped to human chromosome band 1p34 using somatic cell hybrids and fluorescence in situ hybridization; the enzyme dephosphorylates inositol-1,4,5-trisphosphate (IP3) to inositol-1,4-bisphosphate (IP2).\",\n      \"method\": \"Somatic cell hybrid panel, fluorescence in situ hybridization, enzymatic characterization\",\n      \"journal\": \"Cytogenetics and cell genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct chromosomal mapping and enzymatic substrate identification, but foundational characterization only\",\n      \"pmids\": [\"8125013\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"INPP5B is a PI(4,5)P2-preferring inositol 5-phosphatase that is stabilized by NIK via the APPL1 complex (protecting it from ubiquitin-mediated degradation), localizes to the Golgi/ERGIC via RAB-protein interactions, and is recruited to phagosomes and macropinosome-forming ruffles as a Rab5 effector through APPL1, where it hydrolyzes PI(4,5)P2 to drive membrane remodeling events including phagosome/macropinosome sealing, BCR clustering via cofilin/ezrin-dependent actin disassembly, and primary ciliogenesis; in somatic reproductive tissues (Sertoli cells and epididymis) it regulates ADAM protease processing required for sperm maturation and fertility, and it functionally overlaps with the paralog OCRL in renal proximal tubule endocytosis and early embryonic development, though it cannot substitute for OCRL1 in clathrin/AP2-dependent ruffle-mediated membrane remodeling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"INPP5B is an inositol polyphosphate 5-phosphatase that hydrolyzes PI(4,5)P2 (and the soluble substrate IP3 to IP2) to drive membrane remodeling and receptor signaling across multiple cellular contexts [#12, #9]. It is recruited as a Rab5 effector through the adaptor APPL1 to nascent phagosomes and to circular membrane ruffles, where PI(4,5)P2 hydrolysis terminates actin assembly and enables phagosome and macropinosome sealing/scission; loss of the phosphatase or APPL1 prolongs PI(4,5)P2 and actin retention and accentuates Akt activation [#3, #8]. At the B cell plasma membrane, antigen-triggered PI(4,5)P2 dephosphorylation by INPP5B promotes cofilin-mediated actin severing and reduces ezrin-dependent actin–membrane linkage, mobilizing BCR clustering and cell spreading [#9]. INPP5B also localizes to the early secretory pathway (Golgi/ERGIC) via RAB-protein binding and functions in retrograde ERGIC-to-ER transport, and to primary cilia where it is required for ciliogenesis [#1, #6]. It functionally overlaps with the paralog OCRL: combined loss is embryonic lethal, and tubule-specific inactivation on an Ocrl-null background impairs proximal tubule endocytosis and phenocopies Dent disease, yet INPP5B cannot substitute for OCRL1 in clathrin/AP2-dependent ruffle-mediated remodeling because it lacks clathrin/AP2 binding [#0, #7, #2]. In reproductive somatic tissues, INPP5B activity in Sertoli and epididymal cells is required for sperm maturation, motility, and sperm–egg fusion, with effects on ADAM protease processing [#4, #5]. Stability of INPP5B is controlled by NIK, which recruits it into the APPL1 complex to limit ubiquitin-dependent degradation [#10].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Establishing the molecular identity and catalytic activity of INPP5B answered what the gene encodes — a 5-phosphatase acting on inositol phosphates.\",\n      \"evidence\": \"Chromosomal mapping by somatic cell hybrids/FISH plus enzymatic substrate characterization (IP3 to IP2)\",\n      \"pmids\": [\"8125013\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address membrane phosphoinositide substrates\", \"No cellular localization or pathway context\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Genetic knockouts answered whether INPP5B has an essential in vivo role and how it relates to its paralog, revealing redundancy with Ocrl1 and a non-redundant requirement in testis.\",\n      \"evidence\": \"Single and double Inpp5b/Ocrl1 knockout mice with epistasis analysis\",\n      \"pmids\": [\"9593760\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of compensation not defined\", \"Cell-type origin of testicular defect unresolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Conditional knockouts answered where in the reproductive system INPP5B acts, localizing the requirement to somatic Sertoli/epididymal cells rather than germ cells and linking it to ADAM2 processing.\",\n      \"evidence\": \"Conditional and germline knockout mice, IVF assays, ADAM2 immunoblotting, motility analysis\",\n      \"pmids\": [\"11784089\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct phosphoinositide substrate in epididymis not measured\", \"Mechanism connecting lipid phosphatase to protease processing unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Localization and RAB-binding analysis answered where INPP5B operates in the secretory system and how it differs from OCRL1, placing it at the Golgi/ERGIC in retrograde transport.\",\n      \"evidence\": \"Fractionation, immunofluorescence, RAB co-IP, BFA and low-temperature transport assays, mutational analysis\",\n      \"pmids\": [\"17956944\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which RAB(s) mediate targeting not fully resolved\", \"Single-lab observation\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Rescue experiments answered why INPP5B cannot replace OCRL1 in Lowe syndrome cells, tracing functional non-equivalence to the absence of AP2/clathrin binding.\",\n      \"evidence\": \"Rescue in patient fibroblasts with WT/mutant constructs, migration/spreading assays, phosphatase-dead controls\",\n      \"pmids\": [\"19700499\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of differential adaptor binding not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Phagosome studies answered how INPP5B is targeted to dynamic membranes, identifying APPL1-mediated recruitment as a Rab5 effector that controls PI(4,5)P2 and actin clearance.\",\n      \"evidence\": \"siRNA knockdown, live imaging of phosphoinositide dynamics, co-IP, dominant-negative Rab5, phagocytosis assays\",\n      \"pmids\": [\"22072788\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of OCRL vs INPP5B not separated\", \"Direct phosphatase–APPL1 contact not mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Ciliogenesis assays answered whether INPP5B has a role beyond endosomal trafficking, establishing a requirement in primary cilium formation across cells and zebrafish.\",\n      \"evidence\": \"siRNA knockdown, zebrafish morpholino, cilia formation and melanosome transport assays\",\n      \"pmids\": [\"23805271\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphoinositide substrate at cilium not defined\", \"Morpholino-based zebrafish data\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Tubule-specific double knockouts answered the physiological consequence of OCRL/INPP5B redundancy in kidney, showing combined loss impairs proximal tubule endocytosis and phenocopies Dent disease.\",\n      \"evidence\": \"Kidney tubule-specific Inpp5b KO on Ocrl-null background, urine biochemistry, EM, endocytosis assays\",\n      \"pmids\": [\"27895154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"INPP5B-specific contribution distinct from OCRL not isolated\", \"Endocytic substrate selectivity not mapped\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Macropinocytosis imaging answered the precise step at which the phosphatases act, placing PI(4,5)P2 hydrolysis downstream of ruffle formation at the sealing/scission step.\",\n      \"evidence\": \"siRNA of OCRL/Inpp5b and APPL1, live PI(4,5)P2 imaging, dominant-negative Rab5, SNARE inhibition, PIP5K overexpression\",\n      \"pmids\": [\"33722976\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"INPP5B vs OCRL functional division not resolved\", \"Scission machinery linkage not detailed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"B cell studies answered how INPP5B couples PI(4,5)P2 turnover to receptor signaling, linking dephosphorylation to cofilin/ezrin-dependent actin remodeling and BCR clustering.\",\n      \"evidence\": \"Knockdown/knockout in B cells, BCR clustering and spreading assays, PI(4,5)P2 imaging, cofilin/ezrin functional assays\",\n      \"pmids\": [\"35878408\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recruitment mechanism to BCR sites not defined\", \"In vivo immune consequence not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Stability studies answered how INPP5B protein levels are controlled, identifying NIK-driven recruitment into APPL1 as a mechanism limiting ubiquitin-dependent degradation with downstream effects on AKT/lipogenesis.\",\n      \"evidence\": \"Co-IP, ubiquitination immunoblotting, NIK hepatocyte-specific KO mice, omics, in vivo and in vitro loss-of-function\",\n      \"pmids\": [\"41391683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase targeting INPP5B not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"PCIF1 manipulation studies raised the possibility that INPP5B influences PI(3,4)P2 levels and AKT-dependent invasion in glioblastoma.\",\n      \"evidence\": \"PCIF1 knockdown/overexpression, PI(3,4)P2 measurement, AKT immunoblotting, migration/invasion assays\",\n      \"pmids\": [\"42145053\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"INPP5B-specific mechanism inferred indirectly from PCIF1 context\", \"Direct PI(3,4)P2 phosphatase activity of INPP5B not demonstrated here\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the division of labor between INPP5B and OCRL is established at distinct membranes, and what determines INPP5B substrate selectivity in vivo, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of INPP5B substrate/adaptor selectivity\", \"Tissue-specific substrate preference (PI(4,5)P2 vs PI(3,4)P2 vs IP3) not systematically mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [12, 3, 8, 9]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [3, 8, 7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9, 3]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 8]}\n    ],\n    \"complexes\": [\"APPL1 complex\"],\n    \"partners\": [\"APPL1\", \"RAB5\", \"OCRL\", \"NIK\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":7,"faith_total":7,"faith_pct":100.0}}