{"gene":"FNIP1","run_date":"2026-04-28T17:46:04","timeline":{"discoveries":[{"year":2006,"finding":"FNIP1 was identified as a direct binding partner of folliculin (FLCN) and also interacts with AMPK. FNIP1 is phosphorylated by AMPK, and this phosphorylation is reduced by AMPK inhibitors, which also reduce FNIP1 expression. FLCN phosphorylation is diminished by rapamycin and amino acid starvation and facilitated by FNIP1 overexpression, placing FNIP1 in the AMPK and mTOR signaling pathways.","method":"Co-immunoprecipitation, pulldown, in vitro phosphorylation assay, pharmacological inhibition","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — original discovery with reciprocal Co-IP, in vitro phosphorylation, and pharmacological validation; highly cited foundational paper","pmids":["17028174"],"is_preprint":false},{"year":2008,"finding":"FNIP1 interaction with FLCN is mediated mainly by the C-terminal domains of each protein. Knockdown of FNIP1 decreases S6K1 phosphorylation, indicating that the FLCN-FNIP1 complex positively regulates S6K1 phosphorylation (mTOR signaling).","method":"Co-immunoprecipitation, siRNA knockdown, western blot for S6K1 phosphorylation","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP with domain mapping and functional knockdown readout, single lab","pmids":["18663353"],"is_preprint":false},{"year":2012,"finding":"Fnip1 knockout mice display a complete block in B cell development at the pre-B cell stage. AMPK and mTOR are dysregulated in Fnip1-null pre-B cells, resulting in excessive cell growth and enhanced apoptosis in response to metabolic stress, establishing Fnip1 as a metabolic checkpoint for B lymphocyte development.","method":"Genetic knockout mouse model, flow cytometry, immunoglobulin transgene rescue experiment, apoptosis assays","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype, multiple rescue experiments, replicated in second independent study same year","pmids":["22608497"],"is_preprint":false},{"year":2012,"finding":"Conditional deletion of Flcn in B cells recapitulates the pro-B cell arrest of Fnip1-null mice. The B cell developmental arrest in Fnip1-null mice results from rapid caspase-induced pre-B cell death, and a Bcl2 transgene reconstitutes mature B-cell populations, demonstrating FLCN-FNIP1 complex functions through both mTOR-dependent and independent pathways in B cell differentiation.","method":"Conditional knockout mice, Bcl2 transgene rescue, caspase activity assays, flow cytometry","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic rescue strategies, conditional deletion epistasis, independent replication of B cell phenotype","pmids":["22709692"],"is_preprint":false},{"year":2014,"finding":"Loss of Fnip1 in mice increases type I slow-twitch muscle fibers, increases AMPK activation, and increases PGC1α expression. Genetic disruption of PGC1α rescues normal levels of type I fiber markers in Fnip1-null mice, placing Fnip1 upstream of AMPK-PGC1α in the control of muscle fiber type specification.","method":"Knockout mouse model, genetic epistasis (Fnip1 KO × PGC1α KO double mutant), fiber type immunostaining, mitochondrial assays, biochemical analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean KO with genetic epistasis rescue experiment defining pathway position","pmids":["25548157"],"is_preprint":false},{"year":2014,"finding":"Fnip1-null mice show arrest of iNKT cell development at stage 2. Fnip1-null iNKT cells exhibit hyperactive mTOR, reduced mitochondrial number despite lower ATP levels, and increased apoptosis sensitivity, indicating Fnip1 maintains metabolic homeostasis required for iNKT cell maturation.","method":"Knockout mouse model, flow cytometry, TCR transgene and Bim KO rescue experiments, mitochondrial and metabolic assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — KO with defined cellular phenotype, multiple rescue experiments, metabolic measurements","pmids":["24785297"],"is_preprint":false},{"year":2015,"finding":"Structural analysis of yeast Fnip1/2 orthologue Lst4 confirms it contains a longin domain (first domain of the DENN module), and the Lst7 (folliculin orthologue)/Lst4 complex exists as a 1:1 heterodimer in solution. The Lst4 DENN domain mediates interaction with Lst7. The Lst7/Lst4 complex relocates to the vacuolar membrane in response to nutrient (carbon) starvation.","method":"Crystal structure, biochemical reconstitution, gel filtration, co-immunoprecipitation, fluorescence microscopy","journal":"Open biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus reconstituted complex biochemistry and localization imaging","pmids":["26631379"],"is_preprint":false},{"year":2016,"finding":"miR-499 directly targets Fnip1 mRNA. Inhibition of Fnip1 reactivates AMPK/PGC-1α signaling and mitochondrial oxidative metabolism in myocytes, establishing a miR-499/Fnip1/AMPK circuit that couples muscle fiber type and mitochondrial function.","method":"In vivo mouse models, miRNA target validation, siRNA knockdown in myocytes, metabolic assays, mdx mouse model","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 2 — in vivo and in vitro approaches with direct target validation and defined signaling circuit","pmids":["27506764"],"is_preprint":false},{"year":2016,"finding":"A loss-of-function mutation in Fnip1 causes profound B cell deficiency, and FNIP1-deficient mice develop cardiomyopathy with left ventricular hypertrophy and glycogen accumulation. γ2-specific AMPK activity is elevated in neonatal FNIP1-deficient myocardium, and AMPK-dependent ULK1 phosphorylation and autophagy are increased in FNIP1-deficient B cell progenitors, confirming FNIP1 as a negative regulator of AMPK.","method":"ENU-mutagenesis mouse model, cardiac phenotyping, kinase activity assays, autophagy assays, BCL2 rescue","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — independent loss-of-function model with multiple orthogonal biochemical readouts confirming AMPK regulation","pmids":["27303042"],"is_preprint":false},{"year":2019,"finding":"CK2 phosphorylates FNIP1 on priming serine-938, triggering relay phosphorylation on S939, S941, S946, and S948, which promotes FNIP1 interaction with Hsp90 and leads to incremental inhibition of Hsp90 ATPase activity and gradual activation of Hsp90 client proteins. PP5 dephosphorylates FNIP1, enabling O-GlcNAc addition to S938 that antagonizes phosphorylation, prevents Hsp90 interaction, and promotes FNIP1 ubiquitination at K1119 and proteasomal degradation.","method":"In vitro phosphorylation assay, mutagenesis of phospho-sites, co-immunoprecipitation, ATPase activity assay, ubiquitination assay, client protein activation assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzymatic assays combined with site-directed mutagenesis and multiple orthogonal biochemical readouts","pmids":["30699359"],"is_preprint":false},{"year":2021,"finding":"FNIP1 controls skeletal muscle mitochondrial oxidative program through AMPK signaling; basal levels of FNIP1 are sufficient to inhibit AMPK but not mTORC1 activity. Surprisingly, FNIP1 actions on type I fiber program are independent of AMPK and its downstream PGC-1α, establishing separable AMPK-dependent and -independent functions of FNIP1.","method":"Transgenic and knockout mouse models (Fnip1Tg, Fnip1KO, Fnip1TgKO), primary muscle cell assays, genetic epistasis","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple gain- and loss-of-function genetic models with epistasis dissecting two separable pathways","pmids":["33780446"],"is_preprint":false},{"year":2021,"finding":"Loss of FLCN or its binding partners FNIP1/FNIP2 in human renal tubular epithelial cells induces an interferon response independently of interferon, with STAT2 recruitment to chromatin and slowed cellular proliferation, identifying STAT1/2 signaling as a novel target downstream of the FLCN-FNIP complex in renal cells.","method":"CRISPR knockout in RPTEC/TERT1 cells, chromatin immunoprecipitation, transcriptomics, proliferation assays","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with ChIP and transcriptomic readout, but single lab study","pmids":["33459596"],"is_preprint":false},{"year":2022,"finding":"FNIP1 binds to and promotes the activity of SERCA (the main Ca2+ pump responsible for cytosolic Ca2+ removal) in adipocytes. Loss of FNIP1 results in enhanced intracellular Ca2+ signals and activation of a Ca2+-dependent thermogenic program, establishing FNIP1 as a negative regulator of beige adipocyte thermogenesis through SERCA-Ca2+ dynamics.","method":"Adipocyte-specific FNIP1 knockout mice, co-immunoprecipitation, Ca2+ imaging, SERCA activity assays, mitochondrial respiration assays, metabolic phenotyping","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding demonstrated by Co-IP, SERCA activity assay, Ca2+ imaging, and in vivo KO phenotype with multiple orthogonal methods","pmids":["35412553"],"is_preprint":false},{"year":2023,"finding":"AMPK directly phosphorylates five conserved serine residues in FNIP1, suppressing the function of the FLCN-FNIP1 complex. FNIP1 phosphorylation by AMPK is required for nuclear translocation of TFEB and TFEB-dependent increases of PGC1α and ERRα mRNAs, linking mitochondrial damage to sequential waves of lysosomal and mitochondrial biogenesis.","method":"In vitro AMPK phosphorylation assay, phospho-site mutagenesis, TFEB nuclear translocation imaging, transcriptional reporter assays, mitochondrial biogenesis assays","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution, mutagenesis, and multiple functional readouts; highly cited study","pmids":["37079666"],"is_preprint":false},{"year":2023,"finding":"MEF2A and MEF2D transcription factors directly regulate transcription of FNIP1 and FNIP2. The FLCN-FNIP1/2 complex acts as a GTPase-activating protein (GAP) for RRAGC/RRAGD to promote mTORC1 recruitment to lysosomes and activation. SRC kinase phosphorylates MEF2D, enhancing its transcriptional activity and MTORC1 activation through FNIP1/2 upregulation.","method":"ChIP, transcriptional reporter assays, knockdown/overexpression, lysosomal fractionation, mTORC1 activity assays","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and functional assays establishing transcriptional regulation, single lab","pmids":["37772772"],"is_preprint":false},{"year":2023,"finding":"Myofiber-specific FNIP1 deficiency stimulates PGC-1α to activate chemokine gene transcription, driving macrophage recruitment and functional muscle angiogenesis independently of AMPK.","method":"Muscle-specific knockout mouse model, hindlimb ischemia model, macrophage depletion, gene expression analysis, blood flow measurement","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — clean tissue-specific KO with mechanistic pathway dissection, single lab","pmids":["37932296"],"is_preprint":false},{"year":2023,"finding":"FNIP1 is a substrate of the FEM1b ubiquitin ligase axis; the FEM1b-FNIP1 interaction is targetable by the small molecule EN106. FNIP1 alters mitochondrial morphology, reduces oxidative phosphorylation, and protects cells from ROS accumulation.","method":"In vitro experiments in HUVECs, pharmacological inhibition with EN106, cellular ROS and mitochondrial morphology assays","journal":"Bioactive materials","confidence":"Low","confidence_rationale":"Tier 3 — mechanistic description via pharmacological inhibition, limited biochemical detail on FEM1b-FNIP1 interaction","pmids":["37521275"],"is_preprint":false},{"year":2024,"finding":"AMPK phosphorylation of FNIP1 at serine-220 (S220) controls mitochondrial electron transfer chain complex assembly, fuel utilization, and exercise performance in skeletal muscle. Using nonphosphorylatable (S220A) and phosphomimetic (S220D) transgenic mouse models, S220 phosphorylation was shown to regulate mitochondrial function independently of mTORC1-TFEB signaling.","method":"Phospho-site specific transgenic mouse models (S220A/S220D), in vitro AMPK phosphorylation, primary muscle cell biochemistry, exercise performance assays, electron transport chain complex assembly assays","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro phosphorylation combined with phospho-site mutagenesis knock-in mouse models and multiple functional readouts","pmids":["38324677"],"is_preprint":false},{"year":2024,"finding":"Muscle-specific FNIP1 deficiency stimulates nuclear translocation of TFEB, which activates transcription of Igf2 at a conserved promoter-binding site, leading to IGF2 secretion that stimulates osteoclastogenesis through IGF2 receptor signaling, establishing a muscle-bone cross-talk axis.","method":"Muscle-specific FNIP1 knockout and rescue (AAV9-FNIP1), TFEB ChIP at Igf2 promoter, AAV9-IGF2 overexpression, osteoclast assays, bone phenotyping","journal":"Science translational medicine","confidence":"High","confidence_rationale":"Tier 1-2 — ChIP identifying direct TFEB binding at Igf2 promoter, gain- and loss-of-function mouse models, mechanistic rescue experiments","pmids":["38838134"],"is_preprint":false},{"year":2024,"finding":"FNIP1 binds to phosphorylated STAT3 (p-STAT3) and suppresses its expression. Loss of FNIP1 increases STAT3 phosphorylation and nuclear localization, and pharmacological inhibition of p-STAT3 rescues the excessive tumorigenesis caused by FNIP1 deletion in colorectal cancer cells.","method":"Co-immunoprecipitation, in vivo and in vitro knockout models, STAT3 phosphorylation western blot, nuclear fractionation, p-STAT3 inhibitor rescue","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP plus functional rescue with inhibitor, single lab study","pmids":["39262790"],"is_preprint":false},{"year":2024,"finding":"MITF suppresses melanoma mesenchymal phenotype by activating expression of FNIP1, FNIP2, and FLCN, components of the non-canonical mTORC1 pathway, thereby promoting cytoplasmic retention and lysosome-mediated degradation of TFE3.","method":"Transcriptional reporter assays, TFE3 localization imaging, FNIP1/FNIP2/FLCN expression manipulation in melanoma cell lines","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 — preprint, indirect transcriptional regulation with localization readout, no direct biochemical mechanism for FNIP1 action","pmids":["bio_10.1101_2024.07.11.603140"],"is_preprint":true},{"year":2026,"finding":"Fnip1 modulates B cell receptor (BCR) signaling thresholds and metabolic programming by regulating the AMPK/FLCN/TFEB and CD19/PI3K/Akt/mTORC1 pathways, restricting TFEB nuclear access. Loss of Fnip1 in conditional knockout mice causes arrest at the transitional B220+CD93mid stage.","method":"Conditional knockout mouse model, BCR signaling assays, TFEB nuclear localization imaging, metabolic assays, MD4/mHEL/sHEL tolerance model","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — conditional KO with defined cellular phenotype and pathway analysis, preprint with multiple orthogonal approaches","pmids":["41959523"],"is_preprint":true}],"current_model":"FNIP1 is an adaptor protein that forms a complex with folliculin (FLCN) and interacts with AMPK; it is directly phosphorylated by AMPK on multiple serine residues (including S220 and five conserved sites), which suppresses the FLCN-FNIP1 GAP activity toward RagC/D GTPases, thereby controlling mTORC1 lysosomal recruitment, TFEB nuclear translocation, and downstream lysosomal/mitochondrial biogenesis; additionally, FNIP1 acts as a co-chaperone of Hsp90 (regulated by CK2 phosphorylation and PP5 dephosphorylation), interacts with SERCA to modulate intracellular Ca2+ dynamics in adipocytes, binds p-STAT3 to suppress its nuclear translocation, and functions as a negative regulator of AMPK activity in multiple tissues including muscle, B cells, and heart."},"narrative":{"teleology":[{"year":2006,"claim":"Identifying FNIP1 as a FLCN-binding, AMPK-phosphorylated protein placed it at the intersection of AMPK and mTOR signaling, establishing the molecular framework for all subsequent pathway dissection.","evidence":"Co-immunoprecipitation, in vitro AMPK phosphorylation assay, and pharmacological inhibition in mammalian cells","pmids":["17028174"],"confidence":"High","gaps":["AMPK phosphorylation sites on FNIP1 not mapped","functional consequence of phosphorylation unknown","no in vivo model"]},{"year":2008,"claim":"Mapping the FLCN–FNIP1 interaction to C-terminal domains and showing that FNIP1 knockdown reduces S6K1 phosphorylation established the complex as a positive regulator of mTOR signaling.","evidence":"Co-IP domain mapping and siRNA knockdown with S6K1 phosphorylation readout","pmids":["18663353"],"confidence":"Medium","gaps":["Whether mTOR regulation is direct or indirect was unresolved","no structural information"]},{"year":2012,"claim":"Fnip1 knockout mice revealed that FNIP1 is essential for B cell and iNKT cell development by maintaining metabolic homeostasis through AMPK/mTOR balance, extending the protein's role from biochemistry to an in vivo developmental checkpoint.","evidence":"Global Fnip1 KO mice, conditional Flcn deletion, Bcl2 transgene rescue, flow cytometry, apoptosis and metabolic assays","pmids":["22608497","22709692"],"confidence":"High","gaps":["Whether FNIP1 directly suppresses AMPK activity was unclear","mechanism linking metabolic dysregulation to apoptosis not defined"]},{"year":2014,"claim":"Genetic epistasis in Fnip1/PGC-1α double-knockout mice established that FNIP1 acts upstream of AMPK–PGC-1α to control skeletal muscle fiber type, revealing a tissue-specific metabolic function beyond immune cells; simultaneously, iNKT cell arrest confirmed generalized immune metabolic checkpoint function.","evidence":"Fnip1 KO × PGC-1α KO double mutant mice, fiber type immunostaining, mitochondrial assays; separate iNKT KO with TCR transgene and Bim KO rescue","pmids":["25548157","24785297"],"confidence":"High","gaps":["Whether muscle fiber phenotype involves mTORC1 or is solely AMPK-dependent was unresolved","direct AMPK inhibition mechanism unknown"]},{"year":2015,"claim":"Crystal structure of the yeast FNIP1 orthologue Lst4 revealed a DENN/longin domain architecture mediating heterodimer formation with FLCN orthologue Lst7 and nutrient-regulated vacuolar membrane recruitment, providing the first structural framework for the complex.","evidence":"Crystal structure, gel filtration, co-IP, fluorescence microscopy in yeast","pmids":["26631379"],"confidence":"High","gaps":["Mammalian FNIP1 structure not solved","GAP activity not yet assigned to the complex"]},{"year":2016,"claim":"An ENU-derived Fnip1 loss-of-function allele causing cardiomyopathy with elevated AMPK and autophagy independently confirmed FNIP1 as a negative regulator of AMPK, while miR-499 was identified as an upstream suppressor of Fnip1 mRNA linking muscle gene regulatory networks to AMPK control.","evidence":"ENU mutagenesis mouse, cardiac phenotyping, kinase assays; miR-499 target validation in vivo and in myocytes","pmids":["27303042","27506764"],"confidence":"High","gaps":["Molecular basis of AMPK inhibition by FNIP1 not defined","cardiac pathology mechanism not fully dissected"]},{"year":2019,"claim":"Demonstration that CK2 phosphorylates FNIP1 to promote Hsp90 co-chaperone activity, counteracted by PP5 dephosphorylation and O-GlcNAcylation-triggered ubiquitination, revealed a second major molecular function for FNIP1 independent of FLCN and AMPK.","evidence":"In vitro phosphorylation, phospho-site mutagenesis, Hsp90 ATPase assay, ubiquitination assay","pmids":["30699359"],"confidence":"High","gaps":["Physiological client proteins of FNIP1-regulated Hsp90 not identified","relationship between Hsp90 co-chaperone and FLCN-AMPK functions unclear"]},{"year":2021,"claim":"Transgenic gain- and loss-of-function models showed that FNIP1 regulates mitochondrial oxidative programming through both AMPK-dependent and AMPK-independent mechanisms, resolving earlier ambiguity about pathway dependence; separately, FLCN-FNIP1 loss induced interferon-like STAT1/2 signaling in renal cells.","evidence":"Fnip1 transgenic/KO epistasis in muscle; CRISPR KO in RPTEC/TERT1 cells with ChIP and transcriptomics","pmids":["33780446","33459596"],"confidence":"High","gaps":["AMPK-independent mechanism not molecularly identified","whether STAT1/2 activation contributes to Birt-Hogg-Dubé renal pathology unknown"]},{"year":2022,"claim":"Discovery that FNIP1 binds and stimulates SERCA to suppress cytosolic Ca²⁺ and Ca²⁺-dependent thermogenesis in adipocytes identified a third major molecular activity beyond FLCN-GAP and Hsp90 co-chaperone functions.","evidence":"Adipocyte-specific FNIP1 KO mice, co-IP, Ca²⁺ imaging, SERCA activity assays","pmids":["35412553"],"confidence":"High","gaps":["Structural basis of FNIP1-SERCA interaction unknown","whether SERCA regulation occurs in non-adipose tissues not tested"]},{"year":2023,"claim":"Identification of five conserved AMPK phosphorylation sites on FNIP1 that suppress FLCN-FNIP1 GAP activity toward RagC/D, enabling TFEB nuclear translocation and sequential lysosomal then mitochondrial biogenesis, provided the definitive mechanistic link between AMPK activation and mTORC1-TFEB control; the FLCN-FNIP1/2 complex was confirmed as the RagC/D GAP regulated transcriptionally by MEF2A/D.","evidence":"In vitro AMPK phosphorylation, phospho-site mutagenesis, TFEB nuclear translocation imaging, transcriptional reporters; ChIP for MEF2 at FNIP1 promoter","pmids":["37079666","37772772"],"confidence":"High","gaps":["Whether all five sites contribute equally is untested","structural basis of phosphorylation-dependent GAP inhibition unknown"]},{"year":2024,"claim":"Phospho-site-specific knock-in mice (S220A/S220D) demonstrated that AMPK phosphorylation of FNIP1-S220 controls mitochondrial ETC complex assembly and exercise performance independently of mTORC1-TFEB, revealing site-specific bifurcation of FNIP1 signaling outputs; additionally, FNIP1 deficiency drives TFEB-dependent Igf2 secretion mediating muscle-bone crosstalk and binds p-STAT3 to suppress tumorigenesis.","evidence":"Phospho-site transgenic mice with exercise and ETC assays; muscle-specific KO with TFEB ChIP at Igf2 promoter and AAV rescue; Co-IP of FNIP1 with p-STAT3 and STAT3 inhibitor rescue in CRC models","pmids":["38324677","38838134","39262790"],"confidence":"High","gaps":["Direct substrate/effector downstream of S220 phosphorylation for ETC assembly unidentified","whether p-STAT3 binding involves FLCN is unknown","physiological relevance of muscle-bone axis in human disease not established"]},{"year":null,"claim":"Major open questions include the structural basis of how AMPK phosphorylation inhibits FLCN-FNIP1 GAP activity, the molecular identity of the AMPK-independent mechanism controlling fiber type, whether the Hsp90 co-chaperone and SERCA-binding functions intersect with the FLCN-AMPK-mTORC1 axis, and the relevance of FNIP1 to Birt-Hogg-Dubé syndrome pathogenesis in humans.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of mammalian FLCN-FNIP1 in active/inactive states","AMPK-independent fiber-type mechanism uncharacterized","integration of Hsp90, SERCA, and STAT3 functions with canonical pathway untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,4,8,10,13,17]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,6,9]},{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[9]},{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[13,14]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[6,13,14]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,9,12]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,4,8,13,14,17]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[2,5,8,13]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[4,10,13,17]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[8,13]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,3,5]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,3,5]}],"complexes":["FLCN-FNIP1","FLCN-FNIP1-AMPK"],"partners":["FLCN","PRKAA1","PRKAA2","HSP90AA1","CSNK2A1","PPP5C","ATP2A2","STAT3"],"other_free_text":[]},"mechanistic_narrative":"FNIP1 is a multifunctional adaptor protein that integrates nutrient sensing, energy homeostasis, and organelle biogenesis by coupling AMPK signaling to mTORC1-TFEB-dependent transcriptional programs and by serving as a co-chaperone of Hsp90. FNIP1 forms a heterodimeric complex with folliculin (FLCN) that acts as a GAP for RagC/D GTPases, promoting mTORC1 lysosomal recruitment; AMPK phosphorylation of FNIP1 on multiple conserved serines (including S220) suppresses this GAP activity, enabling TFEB nuclear translocation and sequential waves of lysosomal and mitochondrial biogenesis [PMID:37079666, PMID:38324677]. FNIP1 independently functions as a negative regulator of AMPK in B cells, heart, and skeletal muscle, where its loss causes developmental arrest of B and iNKT cells, cardiomyopathy, and a shift to oxidative slow-twitch fibers via the AMPK–PGC-1α axis [PMID:22608497, PMID:27303042, PMID:25548157]. CK2-mediated phosphorylation of FNIP1 promotes its interaction with Hsp90 and incremental inhibition of Hsp90 ATPase activity, while PP5 dephosphorylation and O-GlcNAcylation target FNIP1 for ubiquitin-dependent degradation; additionally, FNIP1 binds SERCA to suppress Ca²⁺-dependent thermogenesis in adipocytes and binds phosphorylated STAT3 to limit its nuclear translocation [PMID:30699359, PMID:35412553, PMID:39262790]."},"prefetch_data":{"uniprot":{"accession":"Q8TF40","full_name":"Folliculin-interacting protein 1","aliases":[],"length_aa":1166,"mass_kda":130.6,"function":"Binding partner of the GTPase-activating protein FLCN: involved in the cellular response to amino acid availability by regulating the non-canonical mTORC1 signaling cascade controlling the MiT/TFE factors TFEB and TFE3 (PubMed:17028174, PubMed:18663353, PubMed:24081491, PubMed:37079666). Required to promote FLCN recruitment to lysosomes and interaction with Rag GTPases, leading to activation of the non-canonical mTORC1 signaling (PubMed:24081491). In low-amino acid conditions, component of the lysosomal folliculin complex (LFC) on the membrane of lysosomes, which inhibits the GTPase-activating activity of FLCN, thereby inactivating mTORC1 and promoting nuclear translocation of TFEB and TFE3 (By similarity). Upon amino acid restimulation, disassembly of the LFC complex liberates the GTPase-activating activity of FLCN, leading to activation of mTORC1 and subsequent inactivation of TFEB and TFE3 (PubMed:37079666). Together with FLCN, regulates autophagy: following phosphorylation by ULK1, interacts with GABARAP and promotes autophagy (PubMed:25126726). In addition to its role in mTORC1 signaling, also acts as a co-chaperone of HSP90AA1/Hsp90: following gradual phosphorylation by CK2, inhibits the ATPase activity of HSP90AA1/Hsp90, leading to activate both kinase and non-kinase client proteins of HSP90AA1/Hsp90 (PubMed:27353360, PubMed:30699359). Acts as a scaffold to load client protein FLCN onto HSP90AA1/Hsp90 (PubMed:27353360). Competes with the activating co-chaperone AHSA1 for binding to HSP90AA1, thereby providing a reciprocal regulatory mechanism for chaperoning of client proteins (PubMed:27353360). Also acts as a core component of the reductive stress response by inhibiting activation of mitochondria in normal conditions: in response to reductive stress, the conserved Cys degron is reduced, leading to recognition and polyubiquitylation by the CRL2(FEM1B) complex, followed by proteasomal (By similarity). Required for B-cell development (PubMed:32905580)","subcellular_location":"Lysosome membrane; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/Q8TF40/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FNIP1","classification":"Not Classified","n_dependent_lines":26,"n_total_lines":1208,"dependency_fraction":0.02152317880794702},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FNIP1","total_profiled":1310},"omim":[{"mim_id":"619705","title":"IMMUNODEFICIENCY 93 AND HYPERTROPHIC CARDIOMYOPATHY; IMD93","url":"https://www.omim.org/entry/619705"},{"mim_id":"612768","title":"FOLLICULIN-INTERACTING PROTEIN 2; FNIP2","url":"https://www.omim.org/entry/612768"},{"mim_id":"610594","title":"FOLLICULIN-INTERACTING PROTEIN 1; FNIP1","url":"https://www.omim.org/entry/610594"},{"mim_id":"607273","title":"FOLLICULIN; FLCN","url":"https://www.omim.org/entry/607273"},{"mim_id":"602742","title":"PROTEIN KINASE, AMP-ACTIVATED, NONCATALYTIC, GAMMA-1; PRKAG1","url":"https://www.omim.org/entry/602742"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FNIP1"},"hgnc":{"alias_symbol":["KIAA1961"],"prev_symbol":[]},"alphafold":{"accession":"Q8TF40","domains":[{"cath_id":"-","chopping":"412-549_991-1107","consensus_level":"high","plddt":82.8538,"start":412,"end":1107},{"cath_id":"3.30.450","chopping":"35-61_124-166_327-410","consensus_level":"medium","plddt":84.2696,"start":35,"end":410}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TF40","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TF40-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TF40-F1-predicted_aligned_error_v6.png","plddt_mean":54.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FNIP1","jax_strain_url":"https://www.jax.org/strain/search?query=FNIP1"},"sequence":{"accession":"Q8TF40","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TF40.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TF40/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TF40"}},"corpus_meta":[{"pmid":"17028174","id":"PMC_17028174","title":"Folliculin encoded by the BHD gene interacts with a binding protein, FNIP1, and AMPK, and is involved in AMPK and mTOR signaling.","date":"2006","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/17028174","citation_count":395,"is_preprint":false},{"pmid":"37079666","id":"PMC_37079666","title":"Induction of lysosomal and mitochondrial biogenesis by AMPK phosphorylation of FNIP1.","date":"2023","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/37079666","citation_count":165,"is_preprint":false},{"pmid":"27506764","id":"PMC_27506764","title":"Coupling of mitochondrial function and skeletal muscle fiber type by a miR-499/Fnip1/AMPK circuit.","date":"2016","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27506764","citation_count":111,"is_preprint":false},{"pmid":"18663353","id":"PMC_18663353","title":"Interaction of folliculin (Birt-Hogg-Dubé gene product) with a novel 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Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/28363698","citation_count":36,"is_preprint":false},{"pmid":"26631379","id":"PMC_26631379","title":"Lst4, the yeast Fnip1/2 orthologue, is a DENN-family protein.","date":"2015","source":"Open biology","url":"https://pubmed.ncbi.nlm.nih.gov/26631379","citation_count":28,"is_preprint":false},{"pmid":"35412553","id":"PMC_35412553","title":"FNIP1 regulates adipocyte browning and systemic glucose homeostasis in mice by shaping intracellular calcium dynamics.","date":"2022","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35412553","citation_count":26,"is_preprint":false},{"pmid":"29897930","id":"PMC_29897930","title":"Loss of Fnip1 alters kidney developmental transcriptional program and synergizes with TSC1 loss to promote mTORC1 activation and renal cyst formation.","date":"2018","source":"PloS 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through inhibiting STAT3 phosphorylation and nuclear translocation.","date":"2024","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/39262790","citation_count":1,"is_preprint":false},{"pmid":"41206543","id":"PMC_41206543","title":"Klebsiella pneumoniae causes mammary gland damage via FNIP1-mediated mitochondrial dysfunction.","date":"2025","source":"Journal of animal science","url":"https://pubmed.ncbi.nlm.nih.gov/41206543","citation_count":1,"is_preprint":false},{"pmid":"40699689","id":"PMC_40699689","title":"FNIP1 Deficiency: Pathophysiology and Clinical Manifestations of a Rare Syndromic Primary Immunodeficiency.","date":"2025","source":"Current issues in molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/40699689","citation_count":0,"is_preprint":false},{"pmid":"41959523","id":"PMC_41959523","title":"FNIP1 Modulates B Cell Receptor Signaling Strength by Coordinating Metabolism During Development.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41959523","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.11.603140","title":"Antagonistic Roles for MITF and TFE3 in Melanoma Plasticity","date":"2024-07-12","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.11.603140","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16968,"output_tokens":5486,"usd":0.066597},"stage2":{"model":"claude-opus-4-6","input_tokens":9060,"output_tokens":3545,"usd":0.200887},"total_usd":0.267484,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"FNIP1 was identified as a direct binding partner of folliculin (FLCN) and also interacts with AMPK. FNIP1 is phosphorylated by AMPK, and this phosphorylation is reduced by AMPK inhibitors, which also reduce FNIP1 expression. FLCN phosphorylation is diminished by rapamycin and amino acid starvation and facilitated by FNIP1 overexpression, placing FNIP1 in the AMPK and mTOR signaling pathways.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, in vitro phosphorylation assay, pharmacological inhibition\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — original discovery with reciprocal Co-IP, in vitro phosphorylation, and pharmacological validation; highly cited foundational paper\",\n      \"pmids\": [\"17028174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"FNIP1 interaction with FLCN is mediated mainly by the C-terminal domains of each protein. Knockdown of FNIP1 decreases S6K1 phosphorylation, indicating that the FLCN-FNIP1 complex positively regulates S6K1 phosphorylation (mTOR signaling).\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, western blot for S6K1 phosphorylation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP with domain mapping and functional knockdown readout, single lab\",\n      \"pmids\": [\"18663353\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Fnip1 knockout mice display a complete block in B cell development at the pre-B cell stage. AMPK and mTOR are dysregulated in Fnip1-null pre-B cells, resulting in excessive cell growth and enhanced apoptosis in response to metabolic stress, establishing Fnip1 as a metabolic checkpoint for B lymphocyte development.\",\n      \"method\": \"Genetic knockout mouse model, flow cytometry, immunoglobulin transgene rescue experiment, apoptosis assays\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype, multiple rescue experiments, replicated in second independent study same year\",\n      \"pmids\": [\"22608497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Conditional deletion of Flcn in B cells recapitulates the pro-B cell arrest of Fnip1-null mice. The B cell developmental arrest in Fnip1-null mice results from rapid caspase-induced pre-B cell death, and a Bcl2 transgene reconstitutes mature B-cell populations, demonstrating FLCN-FNIP1 complex functions through both mTOR-dependent and independent pathways in B cell differentiation.\",\n      \"method\": \"Conditional knockout mice, Bcl2 transgene rescue, caspase activity assays, flow cytometry\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic rescue strategies, conditional deletion epistasis, independent replication of B cell phenotype\",\n      \"pmids\": [\"22709692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Loss of Fnip1 in mice increases type I slow-twitch muscle fibers, increases AMPK activation, and increases PGC1α expression. Genetic disruption of PGC1α rescues normal levels of type I fiber markers in Fnip1-null mice, placing Fnip1 upstream of AMPK-PGC1α in the control of muscle fiber type specification.\",\n      \"method\": \"Knockout mouse model, genetic epistasis (Fnip1 KO × PGC1α KO double mutant), fiber type immunostaining, mitochondrial assays, biochemical analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with genetic epistasis rescue experiment defining pathway position\",\n      \"pmids\": [\"25548157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Fnip1-null mice show arrest of iNKT cell development at stage 2. Fnip1-null iNKT cells exhibit hyperactive mTOR, reduced mitochondrial number despite lower ATP levels, and increased apoptosis sensitivity, indicating Fnip1 maintains metabolic homeostasis required for iNKT cell maturation.\",\n      \"method\": \"Knockout mouse model, flow cytometry, TCR transgene and Bim KO rescue experiments, mitochondrial and metabolic assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined cellular phenotype, multiple rescue experiments, metabolic measurements\",\n      \"pmids\": [\"24785297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Structural analysis of yeast Fnip1/2 orthologue Lst4 confirms it contains a longin domain (first domain of the DENN module), and the Lst7 (folliculin orthologue)/Lst4 complex exists as a 1:1 heterodimer in solution. The Lst4 DENN domain mediates interaction with Lst7. The Lst7/Lst4 complex relocates to the vacuolar membrane in response to nutrient (carbon) starvation.\",\n      \"method\": \"Crystal structure, biochemical reconstitution, gel filtration, co-immunoprecipitation, fluorescence microscopy\",\n      \"journal\": \"Open biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus reconstituted complex biochemistry and localization imaging\",\n      \"pmids\": [\"26631379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"miR-499 directly targets Fnip1 mRNA. Inhibition of Fnip1 reactivates AMPK/PGC-1α signaling and mitochondrial oxidative metabolism in myocytes, establishing a miR-499/Fnip1/AMPK circuit that couples muscle fiber type and mitochondrial function.\",\n      \"method\": \"In vivo mouse models, miRNA target validation, siRNA knockdown in myocytes, metabolic assays, mdx mouse model\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo and in vitro approaches with direct target validation and defined signaling circuit\",\n      \"pmids\": [\"27506764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A loss-of-function mutation in Fnip1 causes profound B cell deficiency, and FNIP1-deficient mice develop cardiomyopathy with left ventricular hypertrophy and glycogen accumulation. γ2-specific AMPK activity is elevated in neonatal FNIP1-deficient myocardium, and AMPK-dependent ULK1 phosphorylation and autophagy are increased in FNIP1-deficient B cell progenitors, confirming FNIP1 as a negative regulator of AMPK.\",\n      \"method\": \"ENU-mutagenesis mouse model, cardiac phenotyping, kinase activity assays, autophagy assays, BCL2 rescue\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — independent loss-of-function model with multiple orthogonal biochemical readouts confirming AMPK regulation\",\n      \"pmids\": [\"27303042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CK2 phosphorylates FNIP1 on priming serine-938, triggering relay phosphorylation on S939, S941, S946, and S948, which promotes FNIP1 interaction with Hsp90 and leads to incremental inhibition of Hsp90 ATPase activity and gradual activation of Hsp90 client proteins. PP5 dephosphorylates FNIP1, enabling O-GlcNAc addition to S938 that antagonizes phosphorylation, prevents Hsp90 interaction, and promotes FNIP1 ubiquitination at K1119 and proteasomal degradation.\",\n      \"method\": \"In vitro phosphorylation assay, mutagenesis of phospho-sites, co-immunoprecipitation, ATPase activity assay, ubiquitination assay, client protein activation assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic assays combined with site-directed mutagenesis and multiple orthogonal biochemical readouts\",\n      \"pmids\": [\"30699359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FNIP1 controls skeletal muscle mitochondrial oxidative program through AMPK signaling; basal levels of FNIP1 are sufficient to inhibit AMPK but not mTORC1 activity. Surprisingly, FNIP1 actions on type I fiber program are independent of AMPK and its downstream PGC-1α, establishing separable AMPK-dependent and -independent functions of FNIP1.\",\n      \"method\": \"Transgenic and knockout mouse models (Fnip1Tg, Fnip1KO, Fnip1TgKO), primary muscle cell assays, genetic epistasis\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple gain- and loss-of-function genetic models with epistasis dissecting two separable pathways\",\n      \"pmids\": [\"33780446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Loss of FLCN or its binding partners FNIP1/FNIP2 in human renal tubular epithelial cells induces an interferon response independently of interferon, with STAT2 recruitment to chromatin and slowed cellular proliferation, identifying STAT1/2 signaling as a novel target downstream of the FLCN-FNIP complex in renal cells.\",\n      \"method\": \"CRISPR knockout in RPTEC/TERT1 cells, chromatin immunoprecipitation, transcriptomics, proliferation assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with ChIP and transcriptomic readout, but single lab study\",\n      \"pmids\": [\"33459596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FNIP1 binds to and promotes the activity of SERCA (the main Ca2+ pump responsible for cytosolic Ca2+ removal) in adipocytes. Loss of FNIP1 results in enhanced intracellular Ca2+ signals and activation of a Ca2+-dependent thermogenic program, establishing FNIP1 as a negative regulator of beige adipocyte thermogenesis through SERCA-Ca2+ dynamics.\",\n      \"method\": \"Adipocyte-specific FNIP1 knockout mice, co-immunoprecipitation, Ca2+ imaging, SERCA activity assays, mitochondrial respiration assays, metabolic phenotyping\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding demonstrated by Co-IP, SERCA activity assay, Ca2+ imaging, and in vivo KO phenotype with multiple orthogonal methods\",\n      \"pmids\": [\"35412553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"AMPK directly phosphorylates five conserved serine residues in FNIP1, suppressing the function of the FLCN-FNIP1 complex. FNIP1 phosphorylation by AMPK is required for nuclear translocation of TFEB and TFEB-dependent increases of PGC1α and ERRα mRNAs, linking mitochondrial damage to sequential waves of lysosomal and mitochondrial biogenesis.\",\n      \"method\": \"In vitro AMPK phosphorylation assay, phospho-site mutagenesis, TFEB nuclear translocation imaging, transcriptional reporter assays, mitochondrial biogenesis assays\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution, mutagenesis, and multiple functional readouts; highly cited study\",\n      \"pmids\": [\"37079666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEF2A and MEF2D transcription factors directly regulate transcription of FNIP1 and FNIP2. The FLCN-FNIP1/2 complex acts as a GTPase-activating protein (GAP) for RRAGC/RRAGD to promote mTORC1 recruitment to lysosomes and activation. SRC kinase phosphorylates MEF2D, enhancing its transcriptional activity and MTORC1 activation through FNIP1/2 upregulation.\",\n      \"method\": \"ChIP, transcriptional reporter assays, knockdown/overexpression, lysosomal fractionation, mTORC1 activity assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and functional assays establishing transcriptional regulation, single lab\",\n      \"pmids\": [\"37772772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Myofiber-specific FNIP1 deficiency stimulates PGC-1α to activate chemokine gene transcription, driving macrophage recruitment and functional muscle angiogenesis independently of AMPK.\",\n      \"method\": \"Muscle-specific knockout mouse model, hindlimb ischemia model, macrophage depletion, gene expression analysis, blood flow measurement\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean tissue-specific KO with mechanistic pathway dissection, single lab\",\n      \"pmids\": [\"37932296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FNIP1 is a substrate of the FEM1b ubiquitin ligase axis; the FEM1b-FNIP1 interaction is targetable by the small molecule EN106. FNIP1 alters mitochondrial morphology, reduces oxidative phosphorylation, and protects cells from ROS accumulation.\",\n      \"method\": \"In vitro experiments in HUVECs, pharmacological inhibition with EN106, cellular ROS and mitochondrial morphology assays\",\n      \"journal\": \"Bioactive materials\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — mechanistic description via pharmacological inhibition, limited biochemical detail on FEM1b-FNIP1 interaction\",\n      \"pmids\": [\"37521275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AMPK phosphorylation of FNIP1 at serine-220 (S220) controls mitochondrial electron transfer chain complex assembly, fuel utilization, and exercise performance in skeletal muscle. Using nonphosphorylatable (S220A) and phosphomimetic (S220D) transgenic mouse models, S220 phosphorylation was shown to regulate mitochondrial function independently of mTORC1-TFEB signaling.\",\n      \"method\": \"Phospho-site specific transgenic mouse models (S220A/S220D), in vitro AMPK phosphorylation, primary muscle cell biochemistry, exercise performance assays, electron transport chain complex assembly assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro phosphorylation combined with phospho-site mutagenesis knock-in mouse models and multiple functional readouts\",\n      \"pmids\": [\"38324677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Muscle-specific FNIP1 deficiency stimulates nuclear translocation of TFEB, which activates transcription of Igf2 at a conserved promoter-binding site, leading to IGF2 secretion that stimulates osteoclastogenesis through IGF2 receptor signaling, establishing a muscle-bone cross-talk axis.\",\n      \"method\": \"Muscle-specific FNIP1 knockout and rescue (AAV9-FNIP1), TFEB ChIP at Igf2 promoter, AAV9-IGF2 overexpression, osteoclast assays, bone phenotyping\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — ChIP identifying direct TFEB binding at Igf2 promoter, gain- and loss-of-function mouse models, mechanistic rescue experiments\",\n      \"pmids\": [\"38838134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FNIP1 binds to phosphorylated STAT3 (p-STAT3) and suppresses its expression. Loss of FNIP1 increases STAT3 phosphorylation and nuclear localization, and pharmacological inhibition of p-STAT3 rescues the excessive tumorigenesis caused by FNIP1 deletion in colorectal cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, in vivo and in vitro knockout models, STAT3 phosphorylation western blot, nuclear fractionation, p-STAT3 inhibitor rescue\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus functional rescue with inhibitor, single lab study\",\n      \"pmids\": [\"39262790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MITF suppresses melanoma mesenchymal phenotype by activating expression of FNIP1, FNIP2, and FLCN, components of the non-canonical mTORC1 pathway, thereby promoting cytoplasmic retention and lysosome-mediated degradation of TFE3.\",\n      \"method\": \"Transcriptional reporter assays, TFE3 localization imaging, FNIP1/FNIP2/FLCN expression manipulation in melanoma cell lines\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — preprint, indirect transcriptional regulation with localization readout, no direct biochemical mechanism for FNIP1 action\",\n      \"pmids\": [\"bio_10.1101_2024.07.11.603140\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Fnip1 modulates B cell receptor (BCR) signaling thresholds and metabolic programming by regulating the AMPK/FLCN/TFEB and CD19/PI3K/Akt/mTORC1 pathways, restricting TFEB nuclear access. Loss of Fnip1 in conditional knockout mice causes arrest at the transitional B220+CD93mid stage.\",\n      \"method\": \"Conditional knockout mouse model, BCR signaling assays, TFEB nuclear localization imaging, metabolic assays, MD4/mHEL/sHEL tolerance model\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with defined cellular phenotype and pathway analysis, preprint with multiple orthogonal approaches\",\n      \"pmids\": [\"41959523\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"FNIP1 is an adaptor protein that forms a complex with folliculin (FLCN) and interacts with AMPK; it is directly phosphorylated by AMPK on multiple serine residues (including S220 and five conserved sites), which suppresses the FLCN-FNIP1 GAP activity toward RagC/D GTPases, thereby controlling mTORC1 lysosomal recruitment, TFEB nuclear translocation, and downstream lysosomal/mitochondrial biogenesis; additionally, FNIP1 acts as a co-chaperone of Hsp90 (regulated by CK2 phosphorylation and PP5 dephosphorylation), interacts with SERCA to modulate intracellular Ca2+ dynamics in adipocytes, binds p-STAT3 to suppress its nuclear translocation, and functions as a negative regulator of AMPK activity in multiple tissues including muscle, B cells, and heart.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"FNIP1 is a multifunctional adaptor protein that integrates nutrient sensing, energy homeostasis, and organelle biogenesis by coupling AMPK signaling to mTORC1-TFEB-dependent transcriptional programs and by serving as a co-chaperone of Hsp90. FNIP1 forms a heterodimeric complex with folliculin (FLCN) that acts as a GAP for RagC/D GTPases, promoting mTORC1 lysosomal recruitment; AMPK phosphorylation of FNIP1 on multiple conserved serines (including S220) suppresses this GAP activity, enabling TFEB nuclear translocation and sequential waves of lysosomal and mitochondrial biogenesis [PMID:37079666, PMID:38324677]. FNIP1 independently functions as a negative regulator of AMPK in B cells, heart, and skeletal muscle, where its loss causes developmental arrest of B and iNKT cells, cardiomyopathy, and a shift to oxidative slow-twitch fibers via the AMPK–PGC-1α axis [PMID:22608497, PMID:27303042, PMID:25548157]. CK2-mediated phosphorylation of FNIP1 promotes its interaction with Hsp90 and incremental inhibition of Hsp90 ATPase activity, while PP5 dephosphorylation and O-GlcNAcylation target FNIP1 for ubiquitin-dependent degradation; additionally, FNIP1 binds SERCA to suppress Ca²⁺-dependent thermogenesis in adipocytes and binds phosphorylated STAT3 to limit its nuclear translocation [PMID:30699359, PMID:35412553, PMID:39262790].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Identifying FNIP1 as a FLCN-binding, AMPK-phosphorylated protein placed it at the intersection of AMPK and mTOR signaling, establishing the molecular framework for all subsequent pathway dissection.\",\n      \"evidence\": \"Co-immunoprecipitation, in vitro AMPK phosphorylation assay, and pharmacological inhibition in mammalian cells\",\n      \"pmids\": [\"17028174\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AMPK phosphorylation sites on FNIP1 not mapped\", \"functional consequence of phosphorylation unknown\", \"no in vivo model\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Mapping the FLCN–FNIP1 interaction to C-terminal domains and showing that FNIP1 knockdown reduces S6K1 phosphorylation established the complex as a positive regulator of mTOR signaling.\",\n      \"evidence\": \"Co-IP domain mapping and siRNA knockdown with S6K1 phosphorylation readout\",\n      \"pmids\": [\"18663353\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether mTOR regulation is direct or indirect was unresolved\", \"no structural information\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Fnip1 knockout mice revealed that FNIP1 is essential for B cell and iNKT cell development by maintaining metabolic homeostasis through AMPK/mTOR balance, extending the protein's role from biochemistry to an in vivo developmental checkpoint.\",\n      \"evidence\": \"Global Fnip1 KO mice, conditional Flcn deletion, Bcl2 transgene rescue, flow cytometry, apoptosis and metabolic assays\",\n      \"pmids\": [\"22608497\", \"22709692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FNIP1 directly suppresses AMPK activity was unclear\", \"mechanism linking metabolic dysregulation to apoptosis not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Genetic epistasis in Fnip1/PGC-1α double-knockout mice established that FNIP1 acts upstream of AMPK–PGC-1α to control skeletal muscle fiber type, revealing a tissue-specific metabolic function beyond immune cells; simultaneously, iNKT cell arrest confirmed generalized immune metabolic checkpoint function.\",\n      \"evidence\": \"Fnip1 KO × PGC-1α KO double mutant mice, fiber type immunostaining, mitochondrial assays; separate iNKT KO with TCR transgene and Bim KO rescue\",\n      \"pmids\": [\"25548157\", \"24785297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether muscle fiber phenotype involves mTORC1 or is solely AMPK-dependent was unresolved\", \"direct AMPK inhibition mechanism unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Crystal structure of the yeast FNIP1 orthologue Lst4 revealed a DENN/longin domain architecture mediating heterodimer formation with FLCN orthologue Lst7 and nutrient-regulated vacuolar membrane recruitment, providing the first structural framework for the complex.\",\n      \"evidence\": \"Crystal structure, gel filtration, co-IP, fluorescence microscopy in yeast\",\n      \"pmids\": [\"26631379\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian FNIP1 structure not solved\", \"GAP activity not yet assigned to the complex\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"An ENU-derived Fnip1 loss-of-function allele causing cardiomyopathy with elevated AMPK and autophagy independently confirmed FNIP1 as a negative regulator of AMPK, while miR-499 was identified as an upstream suppressor of Fnip1 mRNA linking muscle gene regulatory networks to AMPK control.\",\n      \"evidence\": \"ENU mutagenesis mouse, cardiac phenotyping, kinase assays; miR-499 target validation in vivo and in myocytes\",\n      \"pmids\": [\"27303042\", \"27506764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of AMPK inhibition by FNIP1 not defined\", \"cardiac pathology mechanism not fully dissected\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstration that CK2 phosphorylates FNIP1 to promote Hsp90 co-chaperone activity, counteracted by PP5 dephosphorylation and O-GlcNAcylation-triggered ubiquitination, revealed a second major molecular function for FNIP1 independent of FLCN and AMPK.\",\n      \"evidence\": \"In vitro phosphorylation, phospho-site mutagenesis, Hsp90 ATPase assay, ubiquitination assay\",\n      \"pmids\": [\"30699359\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological client proteins of FNIP1-regulated Hsp90 not identified\", \"relationship between Hsp90 co-chaperone and FLCN-AMPK functions unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Transgenic gain- and loss-of-function models showed that FNIP1 regulates mitochondrial oxidative programming through both AMPK-dependent and AMPK-independent mechanisms, resolving earlier ambiguity about pathway dependence; separately, FLCN-FNIP1 loss induced interferon-like STAT1/2 signaling in renal cells.\",\n      \"evidence\": \"Fnip1 transgenic/KO epistasis in muscle; CRISPR KO in RPTEC/TERT1 cells with ChIP and transcriptomics\",\n      \"pmids\": [\"33780446\", \"33459596\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AMPK-independent mechanism not molecularly identified\", \"whether STAT1/2 activation contributes to Birt-Hogg-Dubé renal pathology unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Discovery that FNIP1 binds and stimulates SERCA to suppress cytosolic Ca²⁺ and Ca²⁺-dependent thermogenesis in adipocytes identified a third major molecular activity beyond FLCN-GAP and Hsp90 co-chaperone functions.\",\n      \"evidence\": \"Adipocyte-specific FNIP1 KO mice, co-IP, Ca²⁺ imaging, SERCA activity assays\",\n      \"pmids\": [\"35412553\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of FNIP1-SERCA interaction unknown\", \"whether SERCA regulation occurs in non-adipose tissues not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification of five conserved AMPK phosphorylation sites on FNIP1 that suppress FLCN-FNIP1 GAP activity toward RagC/D, enabling TFEB nuclear translocation and sequential lysosomal then mitochondrial biogenesis, provided the definitive mechanistic link between AMPK activation and mTORC1-TFEB control; the FLCN-FNIP1/2 complex was confirmed as the RagC/D GAP regulated transcriptionally by MEF2A/D.\",\n      \"evidence\": \"In vitro AMPK phosphorylation, phospho-site mutagenesis, TFEB nuclear translocation imaging, transcriptional reporters; ChIP for MEF2 at FNIP1 promoter\",\n      \"pmids\": [\"37079666\", \"37772772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether all five sites contribute equally is untested\", \"structural basis of phosphorylation-dependent GAP inhibition unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Phospho-site-specific knock-in mice (S220A/S220D) demonstrated that AMPK phosphorylation of FNIP1-S220 controls mitochondrial ETC complex assembly and exercise performance independently of mTORC1-TFEB, revealing site-specific bifurcation of FNIP1 signaling outputs; additionally, FNIP1 deficiency drives TFEB-dependent Igf2 secretion mediating muscle-bone crosstalk and binds p-STAT3 to suppress tumorigenesis.\",\n      \"evidence\": \"Phospho-site transgenic mice with exercise and ETC assays; muscle-specific KO with TFEB ChIP at Igf2 promoter and AAV rescue; Co-IP of FNIP1 with p-STAT3 and STAT3 inhibitor rescue in CRC models\",\n      \"pmids\": [\"38324677\", \"38838134\", \"39262790\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrate/effector downstream of S220 phosphorylation for ETC assembly unidentified\", \"whether p-STAT3 binding involves FLCN is unknown\", \"physiological relevance of muscle-bone axis in human disease not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include the structural basis of how AMPK phosphorylation inhibits FLCN-FNIP1 GAP activity, the molecular identity of the AMPK-independent mechanism controlling fiber type, whether the Hsp90 co-chaperone and SERCA-binding functions intersect with the FLCN-AMPK-mTORC1 axis, and the relevance of FNIP1 to Birt-Hogg-Dubé syndrome pathogenesis in humans.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of mammalian FLCN-FNIP1 in active/inactive states\", \"AMPK-independent fiber-type mechanism uncharacterized\", \"integration of Hsp90, SERCA, and STAT3 functions with canonical pathway untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 4, 8, 10, 13, 17]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 6, 9]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [13, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [6, 13, 14]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 9, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 4, 8, 13, 14, 17]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [2, 5, 8, 13]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [4, 10, 13, 17]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [8, 13]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 3, 5]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 3, 5]}\n    ],\n    \"complexes\": [\n      \"FLCN-FNIP1\",\n      \"FLCN-FNIP1-AMPK\"\n    ],\n    \"partners\": [\n      \"FLCN\",\n      \"PRKAA1\",\n      \"PRKAA2\",\n      \"HSP90AA1\",\n      \"CSNK2A1\",\n      \"PPP5C\",\n      \"ATP2A2\",\n      \"STAT3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}