{"gene":"SYTL1","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2001,"finding":"JFC1 was identified as a novel tandem C2 domain-containing protein that binds p67(phox) via affinity chromatography; JFC1-containing beads pulled down both p67(phox) and p47(phox) from neutrophil cytosol, but with purified recombinant proteins only p67(phox) bound directly to JFC1, indicating JFC1 binds the cytosolic NADPH oxidase complex via p67(phox) without disrupting the p67(phox)-p47(phox) interaction. JFC1 bound phosphatidylinositol 3,4,5-trisphosphate (PIP3) and to a lesser extent PI(3,4)P2, but not inositol 1,3,4,5-tetrakisphosphate. Expression of JFC1 in neutrophils was restricted to the plasma membrane/secretory vesicle fraction.","method":"Yeast two-hybrid screen, affinity chromatography (pulldown), lipid-binding assays, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal pulldown with both neutrophil cytosol and recombinant proteins, two orthogonal binding assays, single lab","pmids":["11278853"],"is_preprint":false},{"year":2001,"finding":"JFC1 is an ATP-binding protein with magnesium-dependent ATPase activity; it specifically binds ATP analog 8-azido-[α-32P]ATP with ~10× greater affinity than ADP and does not bind GTP. JFC1 hydrolyzes ATP (Km = 58 μM, kcat = 2.27/min) and dATP in a Mg2+-dependent manner. PIP3 did not affect JFC1 ATPase kinetics, suggesting PIP3 serves a separate function.","method":"Photoaffinity labeling with ATP analog, in vitro ATPase assay, kinetic analysis, truncation mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro enzymatic assay with mutagenesis/truncation and kinetic characterization, single lab but multiple orthogonal methods","pmids":["11553774"],"is_preprint":false},{"year":2002,"finding":"The C2A domain of JFC1 is the module responsible for binding 3'-phosphoinositides and directing plasma membrane association in living cells. The C2A domain colocalized with the PH domain of Akt in vivo, and both JFC1 C2A and full-length JFC1 dissociated from the membrane upon PI3K inhibition (LY294002). Membrane association of the C2A domain was modulated by calcium.","method":"Domain truncation/mutagenesis, in vitro lipid-binding assays, live-cell fluorescence microscopy with PI3K inhibitor treatment","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro binding assays combined with live-cell localization experiments and pharmacological perturbation, single lab with multiple orthogonal methods","pmids":["12189202"],"is_preprint":false},{"year":2002,"finding":"The JFC1 promoter contains three functional NF-κB binding sites; NF-κB p50 binds each site (gel retardation and supershift assays). TNFα stimulation and NF-κB overexpression transactivate the JFC1 promoter, while a dominant-negative IκB decreases basal JFC1 promoter activity. Mutation of the NF-κB sites abolishes transactivation.","method":"Gel retardation/EMSA, supershift assays, luciferase reporter assays, dominant-negative IκB transfection, primer extension analysis","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple orthogonal methods (EMSA, supershift, reporter assay, dominant-negative), single lab","pmids":["12137562"],"is_preprint":false},{"year":2005,"finding":"JFC1 is a Rab27a-binding protein that regulates androgen-dependent secretion of prostatic-specific acid phosphatase (PSAP) in LNCaP cells. JFC1 co-localizes with PSAP but rarely with PSA in prostate granules. Expression of the C2A domain of JFC1 (PIP3-binding domain) inhibited PSAP secretion but not PSA secretion. JFC1 overexpression increased PSA secretion. Both PSAP and PSA secretion were increased by wild-type or constitutively active Rab27aQ78L. PI3K inhibitor abolished PSAP secretion and partially inhibited PSA secretion.","method":"Overexpression/dominant-negative constructs, immunofluorescence colocalization, secretion assays (ELISA), PI3K inhibitor treatment","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple experimental approaches (gain/loss of function, colocalization, pharmacological inhibition), single lab","pmids":["16004602"],"is_preprint":false},{"year":2005,"finding":"Akt phosphorylates JFC1 at serine 241 (identified by HPLC-MS/MS and confirmed by mutagenesis). JFC1 phosphorylation is dependent on the PI3K/Akt pathway (shown using PTEN-null LNCaP cells and LY294002). Direct phosphorylation by Akt was confirmed in vitro. Akt-mediated phosphorylation dramatically decreases when JFC1 is bound to Rab27a, and phosphorylation causes JFC1 to dissociate from the membrane and redistribute to the cytosol. Phosphorylation does not alter JFC1-Rab27a binding affinity.","method":"Microcapillary HPLC-MS/MS phosphosite identification, site-directed mutagenesis, in vitro kinase assay, immunoprecipitation, live-cell imaging with PI3K inhibitor","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay, MS phosphosite identification, mutagenesis, and subcellular localization experiments, single lab with multiple orthogonal methods","pmids":["15998322"],"is_preprint":false},{"year":2008,"finding":"JFC1/Slp1 and Rab27a colocalize in predocked and docked vesicles in granulocytes (TIRF microscopy). JFC1 downregulation by siRNA impairs myeloperoxidase (azurophilic granule) secretion in granulocytes. Immunological interference with JFC1 impairs azurophilic granule exocytosis in human neutrophils. Rab27a but not JFC1 knockdown impairs gelatinase B secretion, indicating different Rab27a effectors mediate distinct granule exocytosis events.","method":"siRNA knockdown, TIRF microscopy colocalization, secretion assays (MPO and gelatinase B), immunological interference, genetically modified (Jinx) mouse neutrophils","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function by siRNA and genetic models, multiple secretion assays, TIRF microscopy, replicated with both human and mouse systems","pmids":["18939952"],"is_preprint":false},{"year":2012,"finding":"JFC1 interacts with and recruits the RhoA-GTPase-activating protein GMIP (Gem-interacting protein) to Rab27a-containing secretory granules. GMIP downregulation induces RhoA activation and actin polymerization, impairing vesicular transport and exocytosis. RhoA activity polarizes around JFC1-containing secretory granules. JFC1-knockout neutrophils show increased RhoA activity, and azurophilic granules fail to traverse cortical actin. Dynamic JFC1-containing vesicles maintain an actin-free environment in their surroundings, and actin depolymerization commences near the secretory organelle rather than the plasma membrane.","method":"Proteomic/co-immunoprecipitation (GMIP identification), siRNA knockdown, RhoA activation assays, quantitative live-cell microscopy, JFC1 knockout neutrophils, actin polymerization assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP/proteomics, genetic KO, siRNA, live-cell microscopy, multiple orthogonal methods, single lab","pmids":["22438581"],"is_preprint":false},{"year":2012,"finding":"JFC1 (Slp1) directly binds a C-terminal region of EPI64 (a TBC-domain RabGAP protein), and JFC1 is an effector for Rab8a. EPI64 uses its RabGAP activity to inactivate Rab8a-GTP, and JFC1 binding to EPI64 recruits Rab8a-GTP for deactivation. Mutants that uncouple JFC1 from either EPI64 or Rab8a-GTP abrogate EPI64-induced actin-coated vacuole formation, indicating the EPI64-JFC1-Rab8a axis regulates membrane recycling through the tubular endosome.","method":"Direct binding assay (co-expression/co-localization), mutant analysis, RabGAP activity assay (Rab8-GTP level measurement), phenotypic readout (vacuole formation)","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding shown, mutant uncoupling analysis, functional phenotype, single lab","pmids":["22219378"],"is_preprint":false},{"year":2019,"finding":"JFC1 (SYTL1) controls Rac1-GTP recycling from the neutrophil uropod to promote directional migration. JFC1 colocalizes with active Rac1 (Rac1-GTP) at dynamic vesicles (shown by STORM super-resolution microscopy). JFC1 interacts with Rac1-GTP in a Rab27a-independent manner. JFC1-null neutrophils display Rac1-GTP accumulation at the uropod, increased tail length, defective polarization, and impaired directional migration to fMLP in vitro. JFC1-null neutrophils also fail to migrate directionally toward chemoattractant in vivo (bone marrow chimeric mice). Chemoattractant-induced actin remodeling, calcium signaling, and Erk activation are normal in JFC1-null cells.","method":"JFC1 knockout mouse neutrophils, STORM super-resolution microscopy, Co-IP (JFC1-Rac1-GTP interaction), chemotaxis assays (in vitro and in vivo chimeric mice), Rac1-GTP activity assays","journal":"Journal of leukocyte biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, in vitro and in vivo functional assays, super-resolution microscopy, Co-IP, multiple orthogonal methods, single lab","pmids":["30748033"],"is_preprint":false},{"year":2023,"finding":"JFC1 (via its C2A domain binding 3'-phosphoinositides) localizes to Anaplasma phagocytophilum inclusions enriched with PI3P. JFC1 knockdown (shRNA) inhibits Anaplasma infection in HL-60 cells. The JFC1 C2A domain is sufficient and required for JFC1 and Rab27a localization to Anaplasma inclusions. Nexinhib20, a small-molecule inhibitor that blocks Rab27a-JFC1 binding, inhibits Anaplasma infection.","method":"shRNA stable knockdown, immunostaining, live-cell imaging, C2A domain truncation analysis, small-molecule inhibitor (Nexinhib20), Rab27a constitutively active/dominant-negative constructs","journal":"Microbes and infection","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function (shRNA), live imaging, domain truncation, pharmacological inhibition, single lab","pmids":["38110148"],"is_preprint":false},{"year":2023,"finding":"SYTL1 forms a complex with Rab27a and CD81 that promotes secretion of CD81+ exosomes. Linc01703 enhances this Rab27a/SYTL1/CD81 interaction. The complex-mediated exosome secretion suppresses immune cell infiltration in the tumor microenvironment.","method":"Co-immunoprecipitation (Rab27a/SYTL1/CD81 complex), in vivo tumor model, exosome secretion assays","journal":"Cancers","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP for complex identification, single lab, mechanistic details of SYTL1's role in the complex not fully resolved","pmids":["38136327"],"is_preprint":false},{"year":2022,"finding":"ELK1 recruits HDAC2 to the SYTL1 promoter to repress SYTL1 transcription and protein expression in bladder cancer cells. Chromatin immunoprecipitation and promoter binding assays confirmed the ELK1-HDAC2 complex occupies the SYTL1 promoter.","method":"ChIP/promoter binding assays, siRNA knockdown, western blot, in vivo xenograft model","journal":"Human cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct promoter occupancy demonstrated, functional rescue experiments, single lab","pmids":["36107384"],"is_preprint":false},{"year":2023,"finding":"WTAP promotes YTHDF2-mediated m6A methylation of SYTL1 mRNA, enhancing its degradation. RIP-qPCR confirmed YTHDF2 directly binds SYTL1 mRNA. Actinomycin D chase experiments showed WTAP reduces SYTL1 mRNA stability.","method":"RIP-qPCR, actinomycin D mRNA stability assay, RT-qPCR, western blot","journal":"Histology and histopathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP-qPCR for direct binding, mRNA stability assay, single lab, two orthogonal methods","pmids":["37933909"],"is_preprint":false},{"year":2025,"finding":"JFC1 regulates mobilization of a small subpopulation of CD11b+ (β2-integrin-containing) granules to the plasma membrane. Nexinhib20 inhibits JFC1 recruitment to CD11b+ granules and reduces β2-integrin surface mobilization, decreasing integrin avidity. This effect is Rac1-independent: Nexinhib20 does not inhibit Rac1 activation (confirmed by FRET-based Rac1 activity assay and Rac1-PAK1 binding assay). JFC1-KO mice confirm JFC1 dependence of CD11b+ granule subset mobilization.","method":"JFC1 knockout mouse neutrophils, Nexinhib20 pharmacological inhibition, quantitative 3D enhanced resolution microscopy, time-resolved FRET Rac1 activity assay, Rac1-PAK1 binding assay, flow cytometry (integrin surface mobilization)","journal":"Journal of leukocyte biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, small-molecule inhibitor, multiple orthogonal Rac1 activity assays, quantitative microscopy, single lab with multiple methods","pmids":["39883854"],"is_preprint":false}],"current_model":"JFC1/SYTL1 is a Rab27a effector protein containing tandem C2 domains and intrinsic Mg2+-dependent ATPase activity, whose C2A domain binds 3'-phosphoinositides (PIP3/PI(3,4)P2) to direct membrane association; Akt-mediated phosphorylation at Ser241 causes JFC1 to dissociate from the membrane and redistribute to the cytosol, while Rab27a binding inhibits this phosphorylation. JFC1 mediates docking and exocytosis of azurophilic granules in neutrophils by recruiting the RhoA-GAP GMIP to secretory granules, locally depolymerizing cortical actin to permit granule transit to the plasma membrane. Additionally, JFC1 interacts with active Rac1-GTP in a Rab27a-independent manner to recycle Rac1-GTP away from the neutrophil uropod, thereby controlling directional chemotaxis. JFC1 also acts as an effector for Rab8a through its interaction with EPI64, participates in CD81+ exosome secretion via a Rab27a/SYTL1/CD81 complex, and is transcriptionally regulated by NF-κB/TNFα and post-transcriptionally regulated by WTAP/YTHDF2-mediated m6A mRNA degradation."},"narrative":{"mechanistic_narrative":"SYTL1 (JFC1/Slp1) is a tandem C2-domain Rab27a effector that couples phosphoinositide-marked membranes to regulated vesicle docking and exocytosis, most extensively characterized in neutrophil granule secretion [PMID:11278853, PMID:16004602, PMID:18939952]. Its C2A domain binds 3'-phosphoinositides (PIP3 and PI(3,4)P2) and directs plasma-membrane and secretory-vesicle association in living cells, an interaction reversed by PI3K inhibition [PMID:11278853, PMID:12189202]. Membrane targeting is gated by the PI3K/Akt axis: Akt directly phosphorylates JFC1 at Ser241, driving its dissociation from membranes into the cytosol, whereas Rab27a binding strongly suppresses this phosphorylation [PMID:15998322]. JFC1 also possesses intrinsic Mg2+-dependent ATPase activity that is independent of its phosphoinositide binding [PMID:11553774]. In neutrophils, JFC1 colocalizes with Rab27a on docked and predocked granules and is required for azurophilic (myeloperoxidase) granule exocytosis, defining effector specificity among Rab27a-dependent secretion events [PMID:18939952]. It executes this by recruiting the RhoA-GAP GMIP to secretory granules to locally depolymerize cortical actin and permit granule transit to the plasma membrane [PMID:22438581], and it independently controls directional chemotaxis by recycling Rac1-GTP away from the neutrophil uropod in a Rab27a-independent manner [PMID:30748033]. Beyond neutrophils, JFC1 acts as a Rab8a effector through binding EPI64 to regulate endosomal membrane recycling [PMID:22219378], regulates androgen-dependent prostatic acid phosphatase secretion [PMID:16004602], and is exploited by Anaplasma phagocytophilum, whose PI3P-enriched inclusions recruit JFC1 via its C2A domain [PMID:38110148]. SYTL1 transcription is activated by NF-κB/TNFα through three functional promoter sites [PMID:12137562].","teleology":[{"year":2001,"claim":"Establishing that JFC1 physically links to the NADPH oxidase machinery and selectively binds 3'-phosphoinositides positioned it as a phosphoinositide-responsive adaptor at the neutrophil plasma membrane.","evidence":"Yeast two-hybrid, affinity pulldown with neutrophil cytosol and recombinant proteins, lipid-binding assays, and subcellular fractionation","pmids":["11278853"],"confidence":"Medium","gaps":["Functional consequence of the p67(phox) interaction for oxidase activity not tested","Single lab; reciprocal binding not extended in vivo"]},{"year":2001,"claim":"Identifying intrinsic Mg2+-dependent ATPase activity defined an enzymatic property of JFC1 distinct from its lipid-binding function, raising the question of what this activity drives mechanistically.","evidence":"Photoaffinity ATP-analog labeling, in vitro ATPase kinetics, and truncation mutagenesis","pmids":["11553774"],"confidence":"High","gaps":["Cellular substrate or physiological role of the ATPase activity unresolved","Whether ATP hydrolysis is required for any membrane-trafficking step untested"]},{"year":2002,"claim":"Mapping phosphoinositide binding and membrane targeting to the C2A domain explained how PI3K signaling spatially controls JFC1 recruitment.","evidence":"Domain truncation, in vitro lipid binding, and live-cell imaging with PI3K inhibition","pmids":["12189202"],"confidence":"High","gaps":["Role of the calcium modulation of C2A membrane binding in physiological secretion not defined"]},{"year":2002,"claim":"Demonstrating NF-κB/TNFα control of the JFC1 promoter linked its expression to inflammatory signaling, relevant to its neutrophil role.","evidence":"EMSA/supershift, luciferase reporters, and dominant-negative IκB in transfected cells","pmids":["12137562"],"confidence":"High","gaps":["Endogenous transcriptional induction kinetics during inflammation not characterized"]},{"year":2005,"claim":"Identifying JFC1 as a Rab27a effector regulating PSAP secretion connected its phosphoinositide-binding module to Rab27a-dependent regulated exocytosis.","evidence":"Overexpression/dominant-negative constructs, immunofluorescence, ELISA secretion assays, and PI3K inhibition in LNCaP cells","pmids":["16004602"],"confidence":"Medium","gaps":["Direct Rab27a-JFC1 binding interface not mapped here","Mechanism distinguishing PSAP from PSA granule targeting unresolved"]},{"year":2005,"claim":"Showing Akt phosphorylates Ser241 to release JFC1 from membranes, and that Rab27a binding blocks this, defined a regulatory switch integrating PI3K/Akt with Rab27a control of membrane residence.","evidence":"HPLC-MS/MS phosphosite mapping, in vitro kinase assay, mutagenesis, and live-cell imaging","pmids":["15998322"],"confidence":"High","gaps":["How Rab27a binding sterically or allosterically protects Ser241 not structurally defined"]},{"year":2008,"claim":"Genetic and siRNA loss-of-function established JFC1 as the Rab27a effector specifically required for azurophilic granule exocytosis, demonstrating effector-specific division of labor among Rab27a partners.","evidence":"siRNA knockdown, TIRF colocalization, MPO/gelatinase secretion assays, and Jinx mouse neutrophils","pmids":["18939952"],"confidence":"High","gaps":["Molecular basis for granule-subset selectivity not yet explained at this stage"]},{"year":2012,"claim":"Discovery that JFC1 recruits the RhoA-GAP GMIP to granules to locally depolymerize cortical actin provided the mechanism by which granules traverse the actin cortex to the plasma membrane.","evidence":"Co-IP/proteomics, siRNA, RhoA activation assays, live-cell microscopy, and JFC1-knockout neutrophils","pmids":["22438581"],"confidence":"High","gaps":["Whether GMIP recruitment is Rab27a-dependent not fully delineated","Coordination with SNARE-mediated fusion machinery not addressed"]},{"year":2012,"claim":"Identifying JFC1 as a Rab8a effector via EPI64 binding extended its function beyond Rab27a to endosomal membrane recycling.","evidence":"Direct binding/co-localization, uncoupling mutants, RabGAP activity assays, and vacuole-formation phenotype","pmids":["22219378"],"confidence":"Medium","gaps":["Physiological setting of the EPI64-JFC1-Rab8a axis outside the cell model unclear","Direct JFC1-EPI64 affinity and stoichiometry not quantified"]},{"year":2019,"claim":"Demonstrating Rab27a-independent JFC1 binding to Rac1-GTP and uropod recycling separated JFC1's chemotaxis function from its granule-secretion function.","evidence":"JFC1-knockout mouse neutrophils, STORM microscopy, Co-IP, and in vitro/in vivo chemotaxis assays","pmids":["30748033"],"confidence":"High","gaps":["Structural basis of the JFC1-Rac1-GTP interaction not defined","How the same protein partitions between Rab27a-dependent and -independent pools unresolved"]},{"year":2022,"claim":"ELK1-HDAC2 promoter repression of SYTL1 added an epigenetic transcriptional control layer relevant in bladder cancer.","evidence":"ChIP/promoter binding, siRNA, western blot, and xenograft model","pmids":["36107384"],"confidence":"Medium","gaps":["Downstream secretory consequences of SYTL1 repression in tumor cells not mechanistically traced"]},{"year":2023,"claim":"WTAP/YTHDF2-mediated m6A degradation of SYTL1 mRNA defined a post-transcriptional regulatory mechanism controlling SYTL1 abundance.","evidence":"RIP-qPCR and actinomycin D mRNA-stability chase","pmids":["37933909"],"confidence":"Medium","gaps":["m6A site location on SYTL1 mRNA not mapped","Cellular phenotype downstream of altered SYTL1 levels not established"]},{"year":2023,"claim":"Localization of JFC1 to PI3P-enriched Anaplasma inclusions via its C2A domain showed that an intracellular pathogen co-opts the phosphoinositide-binding mechanism, and that Nexinhib20 blocks infection.","evidence":"shRNA knockdown, C2A truncation, live imaging, and Nexinhib20 inhibition in HL-60 cells","pmids":["38110148"],"confidence":"Medium","gaps":["Whether JFC1 supports inclusion biogenesis or nutrient acquisition unclear","Role of the ATPase activity in this context untested"]},{"year":2023,"claim":"A proposed Rab27a/SYTL1/CD81 complex links SYTL1 to exosome secretion and tumor immune evasion.","evidence":"Co-immunoprecipitation, in vivo tumor model, and exosome secretion assays","pmids":["38136327"],"confidence":"Low","gaps":["Single Co-IP without reciprocal or structural validation of complex architecture","SYTL1's specific molecular contribution within the complex not resolved","Direct vs indirect CD81 interaction undefined"]},{"year":2025,"claim":"Demonstrating Rac1-independent JFC1 control of a CD11b+/β2-integrin granule subset further dissected its secretory functions, showing distinct pathways for integrin mobilization versus Rac1 recycling.","evidence":"JFC1-knockout neutrophils, Nexinhib20, 3D enhanced-resolution microscopy, and FRET-based Rac1 activity assays","pmids":["39883854"],"confidence":"High","gaps":["Granule-subset selectivity determinants for CD11b+ granules not identified","Whether GMIP/actin mechanism applies to this subset untested"]},{"year":null,"claim":"How a single effector partitions among its distinct Rab27a-dependent granule-secretion, Rab8a-dependent recycling, and Rab27a-independent Rac1-recycling functions, and the physiological role of its intrinsic ATPase activity, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of JFC1 bound to Rab27a, Rab8a, or Rac1-GTP","Functional substrate or trafficking role of the ATPase activity unknown","Mechanism allocating JFC1 between competing effector pools undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,7,8]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[1]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[6,7,9]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[8]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[4,6,7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[6,9,14]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[8,9]}],"complexes":[],"partners":["RAB27A","GMIP","EPI64","RAC1","RAB8A","P67PHOX","CD81"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IYJ3","full_name":"Synaptotagmin-like protein 1","aliases":["Exophilin-7","Protein JFC1"],"length_aa":562,"mass_kda":61.9,"function":"May play a role in vesicle trafficking (By similarity). Binds phosphatidylinositol 3,4,5-trisphosphate. Acts as a RAB27A effector protein and may play a role in cytotoxic granule exocytosis in lymphocytes (By similarity)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q8IYJ3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SYTL1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SYTL1","total_profiled":1310},"omim":[{"mim_id":"611790","title":"MYOSIN VIIA- AND RAB-INTERACTING PROTEIN; MYRIP","url":"https://www.omim.org/entry/611790"},{"mim_id":"608042","title":"SYNAPTOTAGMIN-LIKE 1; SYTL1","url":"https://www.omim.org/entry/608042"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"esophagus","ntpm":98.8},{"tissue":"pancreas","ntpm":101.4}],"url":"https://www.proteinatlas.org/search/SYTL1"},"hgnc":{"alias_symbol":["SLP1","JFC1","FLJ14996","exophilin-7"],"prev_symbol":[]},"alphafold":{"accession":"Q8IYJ3","domains":[{"cath_id":"2.60.40.150","chopping":"270-385","consensus_level":"high","plddt":92.1505,"start":270,"end":385},{"cath_id":"2.60.40.150","chopping":"399-556","consensus_level":"high","plddt":91.1777,"start":399,"end":556}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYJ3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYJ3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYJ3-F1-predicted_aligned_error_v6.png","plddt_mean":72.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SYTL1","jax_strain_url":"https://www.jax.org/strain/search?query=SYTL1"},"sequence":{"accession":"Q8IYJ3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IYJ3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IYJ3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYJ3"}},"corpus_meta":[{"pmid":"22438581","id":"PMC_22438581","title":"Vesicular trafficking through cortical actin during exocytosis is regulated by the Rab27a effector JFC1/Slp1 and the RhoA-GTPase-activating protein Gem-interacting protein.","date":"2012","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/22438581","citation_count":83,"is_preprint":false},{"pmid":"18939952","id":"PMC_18939952","title":"The Rab27a effectors JFC1/Slp1 and Munc13-4 regulate exocytosis of neutrophil granules.","date":"2008","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/18939952","citation_count":72,"is_preprint":false},{"pmid":"11278853","id":"PMC_11278853","title":"JFC1, a novel tandem C2 domain-containing protein associated with the leukocyte NADPH oxidase.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11278853","citation_count":43,"is_preprint":false},{"pmid":"12189202","id":"PMC_12189202","title":"The C2A domain of JFC1 binds to 3'-phosphorylated phosphoinositides and directs plasma membrane association in living cells.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12189202","citation_count":42,"is_preprint":false},{"pmid":"16004602","id":"PMC_16004602","title":"The Rab27a-binding protein, JFC1, regulates androgen-dependent secretion of prostate-specific antigen and prostatic-specific acid phosphatase.","date":"2005","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/16004602","citation_count":38,"is_preprint":false},{"pmid":"22219378","id":"PMC_22219378","title":"EPI64 interacts with Slp1/JFC1 to coordinate Rab8a and Arf6 membrane trafficking.","date":"2012","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/22219378","citation_count":24,"is_preprint":false},{"pmid":"15998322","id":"PMC_15998322","title":"Akt regulates the subcellular localization of the Rab27a-binding protein JFC1 by phosphorylation.","date":"2005","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/15998322","citation_count":23,"is_preprint":false},{"pmid":"30748033","id":"PMC_30748033","title":"The trafficking protein JFC1 regulates Rac1-GTP localization at the uropod controlling neutrophil chemotaxis and in vivo migration.","date":"2019","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/30748033","citation_count":18,"is_preprint":false},{"pmid":"38136327","id":"PMC_38136327","title":"LincRNA01703 Facilitates CD81+ Exosome Secretion to Inhibit Lung Adenocarcinoma Metastasis via the Rab27a/SYTL1/CD81 Complex.","date":"2023","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/38136327","citation_count":13,"is_preprint":false},{"pmid":"11553774","id":"PMC_11553774","title":"Characterization of the nucleotide-binding capacity and the ATPase activity of the PIP3-binding protein JFC1.","date":"2001","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/11553774","citation_count":10,"is_preprint":false},{"pmid":"36107384","id":"PMC_36107384","title":"ELK1 suppresses SYTL1 expression by recruiting HDAC2 in bladder cancer progression.","date":"2022","source":"Human cell","url":"https://pubmed.ncbi.nlm.nih.gov/36107384","citation_count":9,"is_preprint":false},{"pmid":"12137562","id":"PMC_12137562","title":"JFC1 is transcriptionally activated by nuclear factor-kappaB and up-regulated by tumour necrosis factor alpha in prostate carcinoma cells.","date":"2002","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/12137562","citation_count":9,"is_preprint":false},{"pmid":"37933909","id":"PMC_37933909","title":"WTAP enhances the instability of SYTL1 mRNA caused by YTHDF2 in bladder cancer.","date":"2023","source":"Histology and histopathology","url":"https://pubmed.ncbi.nlm.nih.gov/37933909","citation_count":8,"is_preprint":false},{"pmid":"38110148","id":"PMC_38110148","title":"Rab27a via its effector JFC1 localizes to Anaplasma inclusions and promotes Anaplasma proliferation in leukocytes.","date":"2023","source":"Microbes and infection","url":"https://pubmed.ncbi.nlm.nih.gov/38110148","citation_count":4,"is_preprint":false},{"pmid":"39883854","id":"PMC_39883854","title":"Nexinhib20 inhibits JFC1-mediated mobilization of a subset of CD11b/CD18+ vesicles decreasing integrin avidity, but does not inhibit Rac1.","date":"2025","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/39883854","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.08.669066","title":"TCUP – An Open Access Tool to Predict Tissue of Origin and Cancer of Unknown Primary (CUP)","date":"2025-08-12","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.08.669066","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10735,"output_tokens":4836,"usd":0.052373,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12833,"output_tokens":5008,"usd":0.094683,"stage2_stop_reason":"end_turn"},"total_usd":0.147056,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"JFC1 was identified as a novel tandem C2 domain-containing protein that binds p67(phox) via affinity chromatography; JFC1-containing beads pulled down both p67(phox) and p47(phox) from neutrophil cytosol, but with purified recombinant proteins only p67(phox) bound directly to JFC1, indicating JFC1 binds the cytosolic NADPH oxidase complex via p67(phox) without disrupting the p67(phox)-p47(phox) interaction. JFC1 bound phosphatidylinositol 3,4,5-trisphosphate (PIP3) and to a lesser extent PI(3,4)P2, but not inositol 1,3,4,5-tetrakisphosphate. Expression of JFC1 in neutrophils was restricted to the plasma membrane/secretory vesicle fraction.\",\n      \"method\": \"Yeast two-hybrid screen, affinity chromatography (pulldown), lipid-binding assays, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pulldown with both neutrophil cytosol and recombinant proteins, two orthogonal binding assays, single lab\",\n      \"pmids\": [\"11278853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"JFC1 is an ATP-binding protein with magnesium-dependent ATPase activity; it specifically binds ATP analog 8-azido-[α-32P]ATP with ~10× greater affinity than ADP and does not bind GTP. JFC1 hydrolyzes ATP (Km = 58 μM, kcat = 2.27/min) and dATP in a Mg2+-dependent manner. PIP3 did not affect JFC1 ATPase kinetics, suggesting PIP3 serves a separate function.\",\n      \"method\": \"Photoaffinity labeling with ATP analog, in vitro ATPase assay, kinetic analysis, truncation mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro enzymatic assay with mutagenesis/truncation and kinetic characterization, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"11553774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The C2A domain of JFC1 is the module responsible for binding 3'-phosphoinositides and directing plasma membrane association in living cells. The C2A domain colocalized with the PH domain of Akt in vivo, and both JFC1 C2A and full-length JFC1 dissociated from the membrane upon PI3K inhibition (LY294002). Membrane association of the C2A domain was modulated by calcium.\",\n      \"method\": \"Domain truncation/mutagenesis, in vitro lipid-binding assays, live-cell fluorescence microscopy with PI3K inhibitor treatment\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro binding assays combined with live-cell localization experiments and pharmacological perturbation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"12189202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The JFC1 promoter contains three functional NF-κB binding sites; NF-κB p50 binds each site (gel retardation and supershift assays). TNFα stimulation and NF-κB overexpression transactivate the JFC1 promoter, while a dominant-negative IκB decreases basal JFC1 promoter activity. Mutation of the NF-κB sites abolishes transactivation.\",\n      \"method\": \"Gel retardation/EMSA, supershift assays, luciferase reporter assays, dominant-negative IκB transfection, primer extension analysis\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple orthogonal methods (EMSA, supershift, reporter assay, dominant-negative), single lab\",\n      \"pmids\": [\"12137562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"JFC1 is a Rab27a-binding protein that regulates androgen-dependent secretion of prostatic-specific acid phosphatase (PSAP) in LNCaP cells. JFC1 co-localizes with PSAP but rarely with PSA in prostate granules. Expression of the C2A domain of JFC1 (PIP3-binding domain) inhibited PSAP secretion but not PSA secretion. JFC1 overexpression increased PSA secretion. Both PSAP and PSA secretion were increased by wild-type or constitutively active Rab27aQ78L. PI3K inhibitor abolished PSAP secretion and partially inhibited PSA secretion.\",\n      \"method\": \"Overexpression/dominant-negative constructs, immunofluorescence colocalization, secretion assays (ELISA), PI3K inhibitor treatment\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple experimental approaches (gain/loss of function, colocalization, pharmacological inhibition), single lab\",\n      \"pmids\": [\"16004602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Akt phosphorylates JFC1 at serine 241 (identified by HPLC-MS/MS and confirmed by mutagenesis). JFC1 phosphorylation is dependent on the PI3K/Akt pathway (shown using PTEN-null LNCaP cells and LY294002). Direct phosphorylation by Akt was confirmed in vitro. Akt-mediated phosphorylation dramatically decreases when JFC1 is bound to Rab27a, and phosphorylation causes JFC1 to dissociate from the membrane and redistribute to the cytosol. Phosphorylation does not alter JFC1-Rab27a binding affinity.\",\n      \"method\": \"Microcapillary HPLC-MS/MS phosphosite identification, site-directed mutagenesis, in vitro kinase assay, immunoprecipitation, live-cell imaging with PI3K inhibitor\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay, MS phosphosite identification, mutagenesis, and subcellular localization experiments, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"15998322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"JFC1/Slp1 and Rab27a colocalize in predocked and docked vesicles in granulocytes (TIRF microscopy). JFC1 downregulation by siRNA impairs myeloperoxidase (azurophilic granule) secretion in granulocytes. Immunological interference with JFC1 impairs azurophilic granule exocytosis in human neutrophils. Rab27a but not JFC1 knockdown impairs gelatinase B secretion, indicating different Rab27a effectors mediate distinct granule exocytosis events.\",\n      \"method\": \"siRNA knockdown, TIRF microscopy colocalization, secretion assays (MPO and gelatinase B), immunological interference, genetically modified (Jinx) mouse neutrophils\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function by siRNA and genetic models, multiple secretion assays, TIRF microscopy, replicated with both human and mouse systems\",\n      \"pmids\": [\"18939952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"JFC1 interacts with and recruits the RhoA-GTPase-activating protein GMIP (Gem-interacting protein) to Rab27a-containing secretory granules. GMIP downregulation induces RhoA activation and actin polymerization, impairing vesicular transport and exocytosis. RhoA activity polarizes around JFC1-containing secretory granules. JFC1-knockout neutrophils show increased RhoA activity, and azurophilic granules fail to traverse cortical actin. Dynamic JFC1-containing vesicles maintain an actin-free environment in their surroundings, and actin depolymerization commences near the secretory organelle rather than the plasma membrane.\",\n      \"method\": \"Proteomic/co-immunoprecipitation (GMIP identification), siRNA knockdown, RhoA activation assays, quantitative live-cell microscopy, JFC1 knockout neutrophils, actin polymerization assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP/proteomics, genetic KO, siRNA, live-cell microscopy, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"22438581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"JFC1 (Slp1) directly binds a C-terminal region of EPI64 (a TBC-domain RabGAP protein), and JFC1 is an effector for Rab8a. EPI64 uses its RabGAP activity to inactivate Rab8a-GTP, and JFC1 binding to EPI64 recruits Rab8a-GTP for deactivation. Mutants that uncouple JFC1 from either EPI64 or Rab8a-GTP abrogate EPI64-induced actin-coated vacuole formation, indicating the EPI64-JFC1-Rab8a axis regulates membrane recycling through the tubular endosome.\",\n      \"method\": \"Direct binding assay (co-expression/co-localization), mutant analysis, RabGAP activity assay (Rab8-GTP level measurement), phenotypic readout (vacuole formation)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding shown, mutant uncoupling analysis, functional phenotype, single lab\",\n      \"pmids\": [\"22219378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"JFC1 (SYTL1) controls Rac1-GTP recycling from the neutrophil uropod to promote directional migration. JFC1 colocalizes with active Rac1 (Rac1-GTP) at dynamic vesicles (shown by STORM super-resolution microscopy). JFC1 interacts with Rac1-GTP in a Rab27a-independent manner. JFC1-null neutrophils display Rac1-GTP accumulation at the uropod, increased tail length, defective polarization, and impaired directional migration to fMLP in vitro. JFC1-null neutrophils also fail to migrate directionally toward chemoattractant in vivo (bone marrow chimeric mice). Chemoattractant-induced actin remodeling, calcium signaling, and Erk activation are normal in JFC1-null cells.\",\n      \"method\": \"JFC1 knockout mouse neutrophils, STORM super-resolution microscopy, Co-IP (JFC1-Rac1-GTP interaction), chemotaxis assays (in vitro and in vivo chimeric mice), Rac1-GTP activity assays\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, in vitro and in vivo functional assays, super-resolution microscopy, Co-IP, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"30748033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"JFC1 (via its C2A domain binding 3'-phosphoinositides) localizes to Anaplasma phagocytophilum inclusions enriched with PI3P. JFC1 knockdown (shRNA) inhibits Anaplasma infection in HL-60 cells. The JFC1 C2A domain is sufficient and required for JFC1 and Rab27a localization to Anaplasma inclusions. Nexinhib20, a small-molecule inhibitor that blocks Rab27a-JFC1 binding, inhibits Anaplasma infection.\",\n      \"method\": \"shRNA stable knockdown, immunostaining, live-cell imaging, C2A domain truncation analysis, small-molecule inhibitor (Nexinhib20), Rab27a constitutively active/dominant-negative constructs\",\n      \"journal\": \"Microbes and infection\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function (shRNA), live imaging, domain truncation, pharmacological inhibition, single lab\",\n      \"pmids\": [\"38110148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SYTL1 forms a complex with Rab27a and CD81 that promotes secretion of CD81+ exosomes. Linc01703 enhances this Rab27a/SYTL1/CD81 interaction. The complex-mediated exosome secretion suppresses immune cell infiltration in the tumor microenvironment.\",\n      \"method\": \"Co-immunoprecipitation (Rab27a/SYTL1/CD81 complex), in vivo tumor model, exosome secretion assays\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP for complex identification, single lab, mechanistic details of SYTL1's role in the complex not fully resolved\",\n      \"pmids\": [\"38136327\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ELK1 recruits HDAC2 to the SYTL1 promoter to repress SYTL1 transcription and protein expression in bladder cancer cells. Chromatin immunoprecipitation and promoter binding assays confirmed the ELK1-HDAC2 complex occupies the SYTL1 promoter.\",\n      \"method\": \"ChIP/promoter binding assays, siRNA knockdown, western blot, in vivo xenograft model\",\n      \"journal\": \"Human cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct promoter occupancy demonstrated, functional rescue experiments, single lab\",\n      \"pmids\": [\"36107384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"WTAP promotes YTHDF2-mediated m6A methylation of SYTL1 mRNA, enhancing its degradation. RIP-qPCR confirmed YTHDF2 directly binds SYTL1 mRNA. Actinomycin D chase experiments showed WTAP reduces SYTL1 mRNA stability.\",\n      \"method\": \"RIP-qPCR, actinomycin D mRNA stability assay, RT-qPCR, western blot\",\n      \"journal\": \"Histology and histopathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP-qPCR for direct binding, mRNA stability assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"37933909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"JFC1 regulates mobilization of a small subpopulation of CD11b+ (β2-integrin-containing) granules to the plasma membrane. Nexinhib20 inhibits JFC1 recruitment to CD11b+ granules and reduces β2-integrin surface mobilization, decreasing integrin avidity. This effect is Rac1-independent: Nexinhib20 does not inhibit Rac1 activation (confirmed by FRET-based Rac1 activity assay and Rac1-PAK1 binding assay). JFC1-KO mice confirm JFC1 dependence of CD11b+ granule subset mobilization.\",\n      \"method\": \"JFC1 knockout mouse neutrophils, Nexinhib20 pharmacological inhibition, quantitative 3D enhanced resolution microscopy, time-resolved FRET Rac1 activity assay, Rac1-PAK1 binding assay, flow cytometry (integrin surface mobilization)\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, small-molecule inhibitor, multiple orthogonal Rac1 activity assays, quantitative microscopy, single lab with multiple methods\",\n      \"pmids\": [\"39883854\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"JFC1/SYTL1 is a Rab27a effector protein containing tandem C2 domains and intrinsic Mg2+-dependent ATPase activity, whose C2A domain binds 3'-phosphoinositides (PIP3/PI(3,4)P2) to direct membrane association; Akt-mediated phosphorylation at Ser241 causes JFC1 to dissociate from the membrane and redistribute to the cytosol, while Rab27a binding inhibits this phosphorylation. JFC1 mediates docking and exocytosis of azurophilic granules in neutrophils by recruiting the RhoA-GAP GMIP to secretory granules, locally depolymerizing cortical actin to permit granule transit to the plasma membrane. Additionally, JFC1 interacts with active Rac1-GTP in a Rab27a-independent manner to recycle Rac1-GTP away from the neutrophil uropod, thereby controlling directional chemotaxis. JFC1 also acts as an effector for Rab8a through its interaction with EPI64, participates in CD81+ exosome secretion via a Rab27a/SYTL1/CD81 complex, and is transcriptionally regulated by NF-κB/TNFα and post-transcriptionally regulated by WTAP/YTHDF2-mediated m6A mRNA degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SYTL1 (JFC1/Slp1) is a tandem C2-domain Rab27a effector that couples phosphoinositide-marked membranes to regulated vesicle docking and exocytosis, most extensively characterized in neutrophil granule secretion [#0, #4, #6]. Its C2A domain binds 3'-phosphoinositides (PIP3 and PI(3,4)P2) and directs plasma-membrane and secretory-vesicle association in living cells, an interaction reversed by PI3K inhibition [#0, #2]. Membrane targeting is gated by the PI3K/Akt axis: Akt directly phosphorylates JFC1 at Ser241, driving its dissociation from membranes into the cytosol, whereas Rab27a binding strongly suppresses this phosphorylation [#5]. JFC1 also possesses intrinsic Mg2+-dependent ATPase activity that is independent of its phosphoinositide binding [#1]. In neutrophils, JFC1 colocalizes with Rab27a on docked and predocked granules and is required for azurophilic (myeloperoxidase) granule exocytosis, defining effector specificity among Rab27a-dependent secretion events [#6]. It executes this by recruiting the RhoA-GAP GMIP to secretory granules to locally depolymerize cortical actin and permit granule transit to the plasma membrane [#7], and it independently controls directional chemotaxis by recycling Rac1-GTP away from the neutrophil uropod in a Rab27a-independent manner [#9]. Beyond neutrophils, JFC1 acts as a Rab8a effector through binding EPI64 to regulate endosomal membrane recycling [#8], regulates androgen-dependent prostatic acid phosphatase secretion [#4], and is exploited by Anaplasma phagocytophilum, whose PI3P-enriched inclusions recruit JFC1 via its C2A domain [#10]. SYTL1 transcription is activated by NF-\\u03baB/TNF\\u03b1 through three functional promoter sites [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing that JFC1 physically links to the NADPH oxidase machinery and selectively binds 3'-phosphoinositides positioned it as a phosphoinositide-responsive adaptor at the neutrophil plasma membrane.\",\n      \"evidence\": \"Yeast two-hybrid, affinity pulldown with neutrophil cytosol and recombinant proteins, lipid-binding assays, and subcellular fractionation\",\n      \"pmids\": [\"11278853\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Functional consequence of the p67(phox) interaction for oxidase activity not tested\", \"Single lab; reciprocal binding not extended in vivo\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identifying intrinsic Mg2+-dependent ATPase activity defined an enzymatic property of JFC1 distinct from its lipid-binding function, raising the question of what this activity drives mechanistically.\",\n      \"evidence\": \"Photoaffinity ATP-analog labeling, in vitro ATPase kinetics, and truncation mutagenesis\",\n      \"pmids\": [\"11553774\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Cellular substrate or physiological role of the ATPase activity unresolved\", \"Whether ATP hydrolysis is required for any membrane-trafficking step untested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapping phosphoinositide binding and membrane targeting to the C2A domain explained how PI3K signaling spatially controls JFC1 recruitment.\",\n      \"evidence\": \"Domain truncation, in vitro lipid binding, and live-cell imaging with PI3K inhibition\",\n      \"pmids\": [\"12189202\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Role of the calcium modulation of C2A membrane binding in physiological secretion not defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating NF-\\u03baB/TNF\\u03b1 control of the JFC1 promoter linked its expression to inflammatory signaling, relevant to its neutrophil role.\",\n      \"evidence\": \"EMSA/supershift, luciferase reporters, and dominant-negative I\\u03baB in transfected cells\",\n      \"pmids\": [\"12137562\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Endogenous transcriptional induction kinetics during inflammation not characterized\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identifying JFC1 as a Rab27a effector regulating PSAP secretion connected its phosphoinositide-binding module to Rab27a-dependent regulated exocytosis.\",\n      \"evidence\": \"Overexpression/dominant-negative constructs, immunofluorescence, ELISA secretion assays, and PI3K inhibition in LNCaP cells\",\n      \"pmids\": [\"16004602\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct Rab27a-JFC1 binding interface not mapped here\", \"Mechanism distinguishing PSAP from PSA granule targeting unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showing Akt phosphorylates Ser241 to release JFC1 from membranes, and that Rab27a binding blocks this, defined a regulatory switch integrating PI3K/Akt with Rab27a control of membrane residence.\",\n      \"evidence\": \"HPLC-MS/MS phosphosite mapping, in vitro kinase assay, mutagenesis, and live-cell imaging\",\n      \"pmids\": [\"15998322\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"How Rab27a binding sterically or allosterically protects Ser241 not structurally defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Genetic and siRNA loss-of-function established JFC1 as the Rab27a effector specifically required for azurophilic granule exocytosis, demonstrating effector-specific division of labor among Rab27a partners.\",\n      \"evidence\": \"siRNA knockdown, TIRF colocalization, MPO/gelatinase secretion assays, and Jinx mouse neutrophils\",\n      \"pmids\": [\"18939952\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Molecular basis for granule-subset selectivity not yet explained at this stage\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Discovery that JFC1 recruits the RhoA-GAP GMIP to granules to locally depolymerize cortical actin provided the mechanism by which granules traverse the actin cortex to the plasma membrane.\",\n      \"evidence\": \"Co-IP/proteomics, siRNA, RhoA activation assays, live-cell microscopy, and JFC1-knockout neutrophils\",\n      \"pmids\": [\"22438581\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether GMIP recruitment is Rab27a-dependent not fully delineated\", \"Coordination with SNARE-mediated fusion machinery not addressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identifying JFC1 as a Rab8a effector via EPI64 binding extended its function beyond Rab27a to endosomal membrane recycling.\",\n      \"evidence\": \"Direct binding/co-localization, uncoupling mutants, RabGAP activity assays, and vacuole-formation phenotype\",\n      \"pmids\": [\"22219378\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Physiological setting of the EPI64-JFC1-Rab8a axis outside the cell model unclear\", \"Direct JFC1-EPI64 affinity and stoichiometry not quantified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrating Rab27a-independent JFC1 binding to Rac1-GTP and uropod recycling separated JFC1's chemotaxis function from its granule-secretion function.\",\n      \"evidence\": \"JFC1-knockout mouse neutrophils, STORM microscopy, Co-IP, and in vitro/in vivo chemotaxis assays\",\n      \"pmids\": [\"30748033\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Structural basis of the JFC1-Rac1-GTP interaction not defined\", \"How the same protein partitions between Rab27a-dependent and -independent pools unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"ELK1-HDAC2 promoter repression of SYTL1 added an epigenetic transcriptional control layer relevant in bladder cancer.\",\n      \"evidence\": \"ChIP/promoter binding, siRNA, western blot, and xenograft model\",\n      \"pmids\": [\"36107384\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Downstream secretory consequences of SYTL1 repression in tumor cells not mechanistically traced\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"WTAP/YTHDF2-mediated m6A degradation of SYTL1 mRNA defined a post-transcriptional regulatory mechanism controlling SYTL1 abundance.\",\n      \"evidence\": \"RIP-qPCR and actinomycin D mRNA-stability chase\",\n      \"pmids\": [\"37933909\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"m6A site location on SYTL1 mRNA not mapped\", \"Cellular phenotype downstream of altered SYTL1 levels not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Localization of JFC1 to PI3P-enriched Anaplasma inclusions via its C2A domain showed that an intracellular pathogen co-opts the phosphoinositide-binding mechanism, and that Nexinhib20 blocks infection.\",\n      \"evidence\": \"shRNA knockdown, C2A truncation, live imaging, and Nexinhib20 inhibition in HL-60 cells\",\n      \"pmids\": [\"38110148\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether JFC1 supports inclusion biogenesis or nutrient acquisition unclear\", \"Role of the ATPase activity in this context untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A proposed Rab27a/SYTL1/CD81 complex links SYTL1 to exosome secretion and tumor immune evasion.\",\n      \"evidence\": \"Co-immunoprecipitation, in vivo tumor model, and exosome secretion assays\",\n      \"pmids\": [\"38136327\"],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Single Co-IP without reciprocal or structural validation of complex architecture\", \"SYTL1's specific molecular contribution within the complex not resolved\", \"Direct vs indirect CD81 interaction undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrating Rac1-independent JFC1 control of a CD11b+/\\u03b22-integrin granule subset further dissected its secretory functions, showing distinct pathways for integrin mobilization versus Rac1 recycling.\",\n      \"evidence\": \"JFC1-knockout neutrophils, Nexinhib20, 3D enhanced-resolution microscopy, and FRET-based Rac1 activity assays\",\n      \"pmids\": [\"39883854\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Granule-subset selectivity determinants for CD11b+ granules not identified\", \"Whether GMIP/actin mechanism applies to this subset untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single effector partitions among its distinct Rab27a-dependent granule-secretion, Rab8a-dependent recycling, and Rab27a-independent Rac1-recycling functions, and the physiological role of its intrinsic ATPase activity, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No structural model of JFC1 bound to Rab27a, Rab8a, or Rac1-GTP\", \"Functional substrate or trafficking role of the ATPase activity unknown\", \"Mechanism allocating JFC1 between competing effector pools undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 7, 8]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [6, 7, 9]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [4, 6, 7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6, 9, 14]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [8, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RAB27A\", \"GMIP\", \"EPI64\", \"RAC1\", \"RAB8A\", \"p67phox\", \"CD81\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":8,"faith_pct":87.5}}