{"gene":"FKBPL","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2005,"finding":"WISp39/FKBPL stabilizes newly synthesized p21(WAF1/CIP1) protein by preventing its proteasomal degradation. WISp39, p21, and Hsp90 form a trimeric complex in vivo. Point mutations within the C-terminal TPR domain of WISp39 abolish its interaction with Hsp90; this TPR mutant still binds p21 but fails to stabilize it, demonstrating that Hsp90 recruitment via the TPR domain is required for p21 stabilization. WISp39 siRNA knockdown prevents p21 accumulation and cell cycle arrest after ionizing radiation.","method":"Co-IP (trimeric complex), point mutagenesis of TPR domain, siRNA knockdown, proteasome inhibitor assays, cell cycle analysis after ionizing radiation","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, mutagenesis, siRNA, functional cell cycle readout) in a single rigorous study with clear mechanistic conclusions","pmids":["15664193"],"is_preprint":false},{"year":2005,"finding":"WISp39/FKBPL links Hsp90 and p21 stability to the G2/M checkpoint, forming a multi-protein complex critical for a p53-dependent G2 cell cycle checkpoint.","method":"Biochemical complex analysis, cell cycle checkpoint assays (commentary/analysis of Jascur et al. findings)","journal":"Cancer biology & therapy","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — secondary commentary paper referencing the primary Jascur et al. study; no independent new experiments reported","pmids":["15846062"],"is_preprint":false},{"year":2011,"finding":"FKBPL and its 24-amino acid peptide derivative AD-01 inhibit endothelial cell migration, tubule formation, and microvessel formation via the cell-surface receptor CD44. CD44 siRNA knockdown or use of CD44-negative cell lines abrogated the antiangiogenic activity of FKBPL and AD-01, establishing CD44 dependency. Signaling downstream of CD44 promotes an antimigratory phenotype.","method":"Recombinant protein assays (HMEC-1 migration, tubule formation), ex vivo rat neovascularization model, in vivo sponge implantation and intravital microscopy mouse models, CD44 siRNA knockdown, xenograft tumor models (DU145, MDA-231)","journal":"Clinical cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vitro, ex vivo, and in vivo models with genetic (siRNA) and cell-line-based CD44 dependency validation","pmids":["21364036"],"is_preprint":false},{"year":2010,"finding":"FKBPL interacts with estrogen receptor alpha (ERα) and regulates its levels. FKBPL overexpression makes breast cancer cells dependent on estrogen for growth and increases sensitivity to tamoxifen and fulvestrant. FKBPL knockdown decreases p21(WAF1) levels and increases ERα phosphorylation on Ser118 in response to 17β-estradiol and tamoxifen.","method":"Stable overexpression and siRNA knockdown in breast cancer cell lines, western blotting for ERα phosphorylation and p21 levels, proliferation assays, drug sensitivity assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal gain/loss-of-function with specific molecular readouts (ERα phosphorylation, p21 levels), single lab","pmids":["20103631"],"is_preprint":false},{"year":2013,"finding":"RBCK1 is an FKBPL-interacting protein that regulates FKBPL stability at the post-translational level via ubiquitination. RBCK1, FKBPL, and ERα interact within Hsp90 chaperone complexes, and both FKBPL and RBCK1 associate with ERα at the promoter of the estrogen-responsive gene pS2 to regulate pS2 levels. Both proteins are upregulated by 17β-estradiol.","method":"Co-IP (RBCK1-FKBPL interaction), ubiquitination assays, ChIP (promoter association at pS2), siRNA knockdown, stable overexpression clones, proliferation assays","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ubiquitination assay, ChIP, loss- and gain-of-function) establishing the RBCK1-FKBPL regulatory axis","pmids":["23912458"],"is_preprint":false},{"year":2013,"finding":"FKBPL and its peptide derivative AD-01 bind directly to the CD44 receptor and inhibit tumor cell migration in a CD44-dependent manner. CD44 knockdown abrogated AD-01 binding and its anti-migratory activity. FKBPL overexpression/knockdown or AD-01 treatment regulated CD44 expression levels, suggesting a co-regulatory pathway. Downstream of CD44, AD-01 induced cortical actin reorganization, inhibited Rac-1 activity, upregulated RhoA, and increased actin-binding proteins profilin and vinculin.","method":"CD44 siRNA knockdown, FKBPL stable overexpression/siRNA knockdown in HMEC-1 and MDA-MB-231 cells, blocking antibody, actin staining, Rac-1 activity assay, in vivo tumor model","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (siRNA, blocking antibody, binding assay, downstream signaling readouts) in vitro and in vivo confirming CD44-dependent mechanism and cytoskeletal pathway","pmids":["23457460"],"is_preprint":false},{"year":2013,"finding":"AD-01 (FKBPL-derived peptide) inhibits breast cancer stem cells (BCSCs) via a CD44-dependent mechanism, inducing BCSC differentiation (reduction in holoclones, increase in meroclones/paraclones) and reducing stem cell markers Nanog, Oct4, and Sox2. FKBPL knockdown increases Nanog/Oct4/Sox2 and the BCSC population. Additive effects observed when AD-01 was combined with Notch inhibitor DAPT.","method":"Mammosphere assays, flow cytometry (ESA+/CD44+/CD24- and ALDH+ populations), clonogenic assays, qPCR (stem cell markers), immunofluorescence, xenograft tumor initiation assays","journal":"Clinical cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vitro and in vivo methods with gain/loss-of-function establishing CD44-dependent anti-stem cell mechanism","pmids":["23741069"],"is_preprint":false},{"year":2015,"finding":"FKBPL is an essential regulator of developmental angiogenesis: Fkbpl knockout mice show embryonic lethality before E8.5. Fkbpl heterozygotes exhibit increased vascular sprouting, enhanced vessel recruitment, and faster tumor growth. In zebrafish, zFkbpl knockdown disrupts vasculature and is rescued by hFKBPL; this rescue is blocked when zcd44 is also knocked down, confirming the CD44 dependency of FKBPL antiangiogenic function in vivo. FKBPL secretion is downregulated by hypoxic signals but not by VEGF or IL-8.","method":"Fkbpl knockout/heterozygote mouse generation, zebrafish morpholino knockdown, human FKBPL rescue experiments, ex vivo aortic ring assay, in vivo sponge assay, tumor growth assay in Fkbpl+/- mice","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout/knockdown in two model organisms with rescue experiments and multiple in vivo/ex vivo angiogenesis models","pmids":["25767277"],"is_preprint":false},{"year":2015,"finding":"WISp39/FKBPL binds phosphorylated Coronin 1B and forms a complex with Slingshot phosphatase (SSH), allowing dephosphorylation and activation of Cofilin at the leading edge. WISp39 also regulates Arp2/3 complex localization at the leading edge. WISp39 knockdown causes loss of directional motility and loss of single leading edge morphology; this is rescued by co-overexpression of Coronin 1B with constitutively active Cofilin. The interaction with Hsp90 is required for WISp39's role in directed cell migration.","method":"Co-IP (WISp39-Coronin 1B, phospho-specific), siRNA knockdown, rescue with Coronin 1B + constitutively active Cofilin mutant, Arp2/3 localization imaging, directed cell migration assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with phospho-specificity, genetic rescue experiments, and multiple functional readouts establishing the WISp39-Coronin1B-SSH-Cofilin-Arp2/3 pathway","pmids":["25800056"],"is_preprint":false},{"year":2019,"finding":"FKBPL overexpression or treatment with FKBPL-based peptides (AD-01, ALM201) inhibit cancer stem cells and cancer metastasis via downregulation of DLL4 and Notch4 protein and/or mRNA expression, in addition to the CD44 pathway. AD-01 inhibited MDA-MB-231 breast cancer cell migration and invasion in vitro and metastasis in vivo. ALM201 inhibits endocrine therapy-resistant mammospheres.","method":"Stable overexpression, peptide treatment, in vitro migration/invasion assays, in vivo metastasis model (MDA-MB-231-lucD3H1), limiting dilution assay in SCID mice, western blot and qPCR for DLL4/Notch4, mammosphere assays with tamoxifen-resistant cells","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro and in vivo methods with molecular target identification (DLL4/Notch4), single lab","pmids":["30975104"],"is_preprint":false},{"year":2019,"finding":"ALM201 (FKBPL-derived peptide) targets the CD44/STAT3 pathway in ovarian cancer, inhibiting cancer stem cells by inducing differentiation and disrupting angiogenesis.","method":"In vitro CSC assays, in vivo xenograft models (Kuramochi, OVCAR3), immunohistochemistry, ELISA, qRT-PCR, RNAseq, western blotting, tissue microarrays","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro and in vivo methods identifying CD44/STAT3 as a downstream pathway, single lab","pmids":["31772325"],"is_preprint":false},{"year":2024,"finding":"FKBPL functions as a cytosolic ER-phagy regulator. Overexpression of FKBPL triggers ER fragmentation and ER-phagy. FKBPL acts as a scaffold connecting the ER-resident protein CKAP4 and autophagy adaptors LC3/GABARAPs. CKAP4 bridges FKBPL to ER-phagy cargo. ER-phagy-inducing conditions increase FKBPL-CKAP4 interaction followed by FKBPL oligomerization at the ER. FKBPL-CKAP4 deficiency causes Golgi disassembly, lysosome impairment, and increased ER-derived secretory vesicles with enhanced cytosolic protein secretion via microvesicle shedding.","method":"Gain-of-function screen, Co-IP (FKBPL-CKAP4, FKBPL-LC3/GABARAP), overexpression-induced ER fragmentation assays, FKBPL/CKAP4 double knockdown/knockout, ER-phagy flux assays, secretory vesicle/microvesicle analysis, organelle morphology imaging","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — phenotype-based screen with multiple orthogonal methods (Co-IP, gain/loss-of-function, organelle imaging, secretion assays) establishing the FKBPL-CKAP4-LC3 scaffold mechanism","pmids":["39251576"],"is_preprint":false},{"year":2010,"finding":"FKBPL enhances androgen receptor (AR) transcriptional activity in reporter assays, suggesting a role in AR-mediated signaling. FKBPL is expressed in testis with expression upregulated at puberty.","method":"AR reporter assay (in vitro), RT-PCR, immunohistochemistry, RNA array blot","journal":"Reproductive biology and endocrinology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single reporter assay for AR activity, single lab, limited mechanistic follow-up","pmids":["20210997"],"is_preprint":false},{"year":2000,"finding":"Repression of DIR1/FKBPL using antisense oligonucleotides in three radioresistant cell lines (V79, RT112, UM-UC-3) significantly increased rates of DNA single-strand break repair and enhanced cell survival after X-ray irradiation; this effect was not observed in the radiosensitive ATBIVA cell line, implicating FKBPL in the mechanism of induced radioresistance.","method":"Antisense oligonucleotide transfection, alkaline comet assay (SSB repair), clonogenic survival assay after X-ray irradiation","journal":"International journal of radiation biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional loss-of-function with two orthogonal readouts (DNA repair and clonogenic survival) across multiple cell lines including a negative control line","pmids":["10866283"],"is_preprint":false},{"year":2025,"finding":"FKBPL expression is downregulated in murine hindlimb ischemia, correlating with increased neovascularization. In a 3D microfluidics model, hypoxia suppresses FKBPL and VE-cadherin, leading to increased endothelial cell migration; AD-01 restores these effects. Proteomic analysis revealed AD-01 treatment in hypoxia enhances tissue remodelling proteins (collagen alpha-1(XIX) chain, JCAD). Under inflammatory conditions, FKBPL and HIF-1α are co-elevated, and AD-01 normalizes their expression without affecting migration.","method":"Hindlimb ischemia mouse model (immunofluorescence, RNA extraction), 3D microfluidics cell culture model, siRNA knockdown of FKBPL, LC-MS/MS untargeted proteomics, western blot","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vivo and 3D in vitro models with proteomic target identification and siRNA validation, single lab","pmids":["40069829"],"is_preprint":false},{"year":2026,"finding":"FKBPL knockdown in human aortic endothelial cells reduces VE-cadherin and impairs endothelial barrier function in normal glucose. In high-glucose conditions, FKBPL overexpression inhibits angiogenesis by suppressing FGF and PDGF pathways and activating proinflammatory pathways (TGF-β, leukocyte migration, IL-7 signaling), likely via CD44, and upregulating miR-29b-3p and miR-302b-5p.","method":"FKBPL transgenic (fkbpl) mice, streptozotocin-induced diabetes model, FKBPL knockdown/overexpression in endothelial cells, angiogenesis assays, barrier function assay, pathway analysis, miRNA quantification","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo transgenic model plus in vitro mechanistic studies with pathway-level molecular readouts, single lab","pmids":["41674464"],"is_preprint":false}],"current_model":"FKBPL (also known as WISp39/DIR1/NG7) is a TPR-domain-containing Hsp90 co-chaperone that: (1) stabilizes p21(WAF1/CIP1) by recruiting Hsp90 into a trimeric complex to prevent proteasomal degradation, thereby regulating the G2/M checkpoint; (2) is itself regulated by RBCK1-mediated ubiquitination within Hsp90-ERα complexes to control estrogen receptor signaling and endocrine therapy response; (3) acts extracellularly as an antiangiogenic protein by binding the CD44 receptor, driving cytoskeletal reorganization (Rac-1 inhibition, RhoA upregulation, cortical actin formation) and inhibiting cell migration; (4) controls directed cell migration intracellularly by binding phospho-Coronin 1B to scaffold Slingshot phosphatase and activate Cofilin while positioning Arp2/3 at the leading edge; (5) suppresses cancer stem cells via DLL4/Notch4 and CD44/STAT3 pathways; (6) is an essential regulator of developmental angiogenesis (embryonic lethal knockout, CD44-dependent in zebrafish); and (7) functions as a cytosolic ER-phagy regulator by scaffolding CKAP4 and LC3/GABARAPs to drive ER fragmentation and autophagy, with its deficiency enhancing protein secretion via microvesicles."},"narrative":{"mechanistic_narrative":"FKBPL (WISp39/DIR1) is a TPR-domain Hsp90 co-chaperone that operates in two distinct compartments: intracellularly it controls protein stability and cytoskeletal dynamics, and extracellularly it acts as a secreted antiangiogenic ligand. As a co-chaperone it stabilizes newly synthesized p21(WAF1/CIP1) by forming a trimeric complex with Hsp90, an interaction that requires the C-terminal TPR domain; loss of FKBPL prevents p21 accumulation and the G2/M cell cycle arrest after ionizing radiation [PMID:15664193]. FKBPL also engages estrogen receptor alpha within Hsp90 complexes, modulating ERα phosphorylation, p21 levels, and endocrine therapy sensitivity, and is itself subject to RBCK1-mediated ubiquitination that controls its stability and its co-occupancy with ERα at estrogen-responsive promoters [PMID:20103631, PMID:23912458]. Through Hsp90, FKBPL further scaffolds directed cell migration by binding phospho-Coronin 1B to position Slingshot phosphatase, activating Cofilin and localizing the Arp2/3 complex at the leading edge [PMID:25800056]. Secreted FKBPL and its peptide derivatives (AD-01, ALM201) bind the cell-surface receptor CD44 to drive an antimigratory, antiangiogenic phenotype involving Rac-1 inhibition, RhoA upregulation, and cortical actin reorganization [PMID:21364036, PMID:23457460], and this CD44 axis is required for FKBPL's essential role in developmental angiogenesis, where knockout is embryonic lethal and zebrafish vascular defects are rescued by human FKBPL in a CD44-dependent manner [PMID:25767277]. The same secreted activity suppresses cancer stem cells and metastasis through CD44/STAT3 and DLL4/Notch4 signaling [PMID:23741069, PMID:30975104, PMID:31772325]. Most recently, FKBPL was defined as a cytosolic ER-phagy regulator that scaffolds the ER-resident protein CKAP4 to LC3/GABARAP autophagy adaptors, driving ER fragmentation and autophagic turnover, with its deficiency redirecting cargo toward microvesicle-mediated secretion [PMID:39251576].","teleology":[{"year":2005,"claim":"Established FKBPL's first molecular function: how the cell stabilizes p21 to enforce a DNA-damage cell cycle checkpoint, answering whether a TPR co-chaperone gates p21 turnover.","evidence":"Co-IP of a trimeric WISp39-p21-Hsp90 complex, TPR-domain point mutagenesis, siRNA knockdown, and cell cycle analysis after ionizing radiation","pmids":["15664193","15846062"],"confidence":"High","gaps":["Does not define how FKBPL physically shields p21 from the proteasome","Substrate range of the Hsp90-FKBPL module beyond p21 not addressed"]},{"year":2000,"claim":"Linked FKBPL/DIR1 to acquired radioresistance, raising the question of whether it influences DNA single-strand break repair.","evidence":"Antisense oligonucleotide knockdown with alkaline comet assay and clonogenic survival across radioresistant and radiosensitive cell lines","pmids":["10866283"],"confidence":"Medium","gaps":["No molecular mechanism connecting FKBPL to SSB repair machinery","Predates the p21/Hsp90 model and not mechanistically reconciled with it"]},{"year":2010,"claim":"Extended FKBPL's chaperone role to hormone receptor signaling, testing whether it regulates ERα levels and endocrine therapy response.","evidence":"Reciprocal overexpression/knockdown in breast cancer lines with western blotting for ERα Ser118 phosphorylation, p21, and drug sensitivity assays","pmids":["20103631"],"confidence":"Medium","gaps":["Direct ERα binding versus Hsp90-mediated association not resolved here","AR reporter activity (idx 12) is a separate low-confidence claim not integrated"]},{"year":2013,"claim":"Resolved how FKBPL itself is regulated and how it acts at estrogen target genes, identifying RBCK1 as the post-translational controller.","evidence":"Co-IP, ubiquitination assays, and ChIP at the pS2 promoter with gain/loss-of-function in breast cancer cells","pmids":["23912458"],"confidence":"High","gaps":["Ubiquitin chain type and degradative versus non-degradative fate of FKBPL not defined","Stoichiometry within Hsp90-ERα complexes unknown"]},{"year":2013,"claim":"Defined FKBPL's extracellular mechanism: direct CD44 binding driving cytoskeletal reorganization to block migration, angiogenesis, and cancer stem cells.","evidence":"Recombinant FKBPL/AD-01 with CD44 siRNA, blocking antibody, Rac-1 activity and actin imaging, mammosphere and xenograft assays","pmids":["21364036","23457460","23741069"],"confidence":"High","gaps":["How a TPR co-chaperone is secreted and presented to CD44 not established","Structural basis of FKBPL-CD44 binding unknown"]},{"year":2015,"claim":"Demonstrated FKBPL is essential for developmental angiogenesis in vivo and that this function is CD44-dependent.","evidence":"Fkbpl knockout/heterozygote mice, zebrafish morpholino knockdown with human FKBPL rescue blocked by cd44 co-knockdown, and ex vivo/in vivo angiogenesis models","pmids":["25767277"],"confidence":"High","gaps":["Cause of pre-E8.5 embryonic lethality not pinpointed","Connection between intracellular chaperone roles and secreted angiostatic activity in development unresolved"]},{"year":2015,"claim":"Identified FKBPL's intracellular cytoskeletal mechanism, showing it scaffolds a phosphatase-cofilin module for directed motility.","evidence":"Phospho-specific reciprocal Co-IP of WISp39-Coronin 1B, SSH/Cofilin pathway analysis, Arp2/3 localization imaging, and rescue with Coronin 1B plus constitutively active Cofilin","pmids":["25800056"],"confidence":"High","gaps":["Relationship between this promigratory intracellular role and the antimigratory extracellular CD44 role not reconciled","Hsp90-dependence mechanism in this context not detailed"]},{"year":2019,"claim":"Broadened the anti-stem-cell/antimetastatic mechanism beyond CD44 to DLL4/Notch4 and CD44/STAT3 signaling.","evidence":"Overexpression and peptide treatment (AD-01, ALM201) with migration/invasion, metastasis, limiting dilution, and CD44/STAT3 and DLL4/Notch4 readouts in breast and ovarian models","pmids":["30975104","31772325"],"confidence":"Medium","gaps":["Whether DLL4/Notch4 and STAT3 effects are downstream of CD44 or parallel not fully separated","Single-lab findings"]},{"year":2024,"claim":"Revealed a distinct cytosolic function: FKBPL as an ER-phagy scaffold linking CKAP4 to autophagy adaptors and controlling secretory fate.","evidence":"Gain-of-function screen, Co-IP of FKBPL-CKAP4 and FKBPL-LC3/GABARAP, double knockdown/knockout, ER-phagy flux and organelle imaging, and microvesicle secretion analysis","pmids":["39251576"],"confidence":"High","gaps":["Trigger for FKBPL oligomerization at the ER not defined","Relationship between ER-phagy role and Hsp90/CD44 functions unknown"]},{"year":2025,"claim":"Positioned FKBPL within ischemic and diabetic vascular contexts, testing how hypoxia and metabolic stress modulate its angiostatic activity.","evidence":"Hindlimb ischemia and streptozotocin diabetic mouse models, 3D microfluidics with siRNA/overexpression, LC-MS/MS proteomics, and miRNA quantification","pmids":["40069829","41674464"],"confidence":"Medium","gaps":["Causal hierarchy among CD44, VE-cadherin, FGF/PDGF/TGF-β pathways, and miRNAs not established","Single-lab pathway-level associations"]},{"year":null,"claim":"It remains unresolved how FKBPL's distinct compartmentalized activities — Hsp90/p21 chaperoning, secreted CD44 antiangiogenesis, leading-edge cytoskeletal scaffolding, and cytosolic ER-phagy — are mechanistically coordinated and switched within a single protein.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying structural or regulatory model linking the chaperone, secreted, and ER-phagy functions","Mechanism of FKBPL secretion is undefined","How FKBPL toggles between promigratory (Coronin 1B) and antimigratory (CD44) outcomes is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[8,11]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,4]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[2,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[11]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,7]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,5,7]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,4]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7]}],"complexes":["FKBPL-p21-Hsp90 trimeric complex","Hsp90-ERα chaperone complex"],"partners":["HSP90","CDKN1A","ESR1","RBCK1","CD44","CORO1B","CKAP4","MAP1LC3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UIM3","full_name":"FK506-binding protein-like","aliases":["WAF-1/CIP1 stabilizing protein 39","WISp39"],"length_aa":349,"mass_kda":38.2,"function":"May be involved in response to X-ray. Regulates p21 protein stability by binding to Hsp90 and p21","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9UIM3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FKBPL","classification":"Not Classified","n_dependent_lines":57,"n_total_lines":1208,"dependency_fraction":0.04718543046357616},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FKBPL","total_profiled":1310},"omim":[{"mim_id":"617076","title":"FK506-BINDING PROTEIN-LIKE; FKBPL","url":"https://www.omim.org/entry/617076"},{"mim_id":"610924","title":"RANBP-TYPE AND C3HC4-TYPE ZINC FINGER-CONTAINING 1; RBCK1","url":"https://www.omim.org/entry/610924"},{"mim_id":"138040","title":"NUCLEAR RECEPTOR SUBFAMILY 3, GROUP C, MEMBER 1; NR3C1","url":"https://www.omim.org/entry/138040"},{"mim_id":"116899","title":"CYCLIN-DEPENDENT KINASE INHIBITOR 1A; CDKN1A","url":"https://www.omim.org/entry/116899"},{"mim_id":"107269","title":"CD44 ANTIGEN; CD44","url":"https://www.omim.org/entry/107269"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Mitotic spindle","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FKBPL"},"hgnc":{"alias_symbol":["DIR1","NG7","WISp39"],"prev_symbol":[]},"alphafold":{"accession":"Q9UIM3","domains":[{"cath_id":"3.10.50.40","chopping":"93-196","consensus_level":"high","plddt":87.7718,"start":93,"end":196},{"cath_id":"1.20.58","chopping":"198-265","consensus_level":"medium","plddt":92.7709,"start":198,"end":265},{"cath_id":"1.25.40.10","chopping":"278-349","consensus_level":"medium","plddt":95.6949,"start":278,"end":349}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UIM3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UIM3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UIM3-F1-predicted_aligned_error_v6.png","plddt_mean":77.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FKBPL","jax_strain_url":"https://www.jax.org/strain/search?query=FKBPL"},"sequence":{"accession":"Q9UIM3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UIM3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UIM3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UIM3"}},"corpus_meta":[{"pmid":"23602565","id":"PMC_23602565","title":"A feedback regulatory loop between G3P and lipid transfer proteins DIR1 and AZI1 mediates azelaic-acid-induced systemic immunity.","date":"2013","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/23602565","citation_count":149,"is_preprint":false},{"pmid":"15664193","id":"PMC_15664193","title":"Regulation of p21(WAF1/CIP1) stability by WISp39, a Hsp90 binding TPR protein.","date":"2005","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/15664193","citation_count":114,"is_preprint":false},{"pmid":"22694956","id":"PMC_22694956","title":"Genome-wide association study of age-related macular degeneration identifies associated variants in the TNXB-FKBPL-NOTCH4 region of chromosome 6p21.3.","date":"2012","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22694956","citation_count":81,"is_preprint":false},{"pmid":"29896854","id":"PMC_29896854","title":"Low-pH production of d-lactic acid using newly isolated acid tolerant yeast Pichia kudriavzevii NG7.","date":"2018","source":"Biotechnology and bioengineering","url":"https://pubmed.ncbi.nlm.nih.gov/29896854","citation_count":59,"is_preprint":false},{"pmid":"23741069","id":"PMC_23741069","title":"Targeting treatment-resistant breast cancer stem cells with FKBPL and its peptide derivative, AD-01, via the CD44 pathway.","date":"2013","source":"Clinical cancer research : an official journal of the American Association for Cancer Research","url":"https://pubmed.ncbi.nlm.nih.gov/23741069","citation_count":57,"is_preprint":false},{"pmid":"30975104","id":"PMC_30975104","title":"FKBPL and its peptide derivatives inhibit endocrine therapy resistant cancer stem cells and breast cancer metastasis by downregulating DLL4 and Notch4.","date":"2019","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/30975104","citation_count":50,"is_preprint":false},{"pmid":"26419658","id":"PMC_26419658","title":"RALA-mediated delivery of FKBPL nucleic acid therapeutics.","date":"2015","source":"Nanomedicine (London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/26419658","citation_count":49,"is_preprint":false},{"pmid":"21364036","id":"PMC_21364036","title":"FKBPL and peptide derivatives: novel biological agents that inhibit angiogenesis by a CD44-dependent mechanism.","date":"2011","source":"Clinical cancer research : an official journal of the American Association for Cancer Research","url":"https://pubmed.ncbi.nlm.nih.gov/21364036","citation_count":48,"is_preprint":false},{"pmid":"31772325","id":"PMC_31772325","title":"FKBPL-based peptide, ALM201, targets angiogenesis and cancer stem cells in ovarian cancer.","date":"2019","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/31772325","citation_count":44,"is_preprint":false},{"pmid":"20103631","id":"PMC_20103631","title":"FKBPL regulates estrogen receptor signaling and determines response to endocrine therapy.","date":"2010","source":"Cancer 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CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/36652019","citation_count":36,"is_preprint":false},{"pmid":"25767277","id":"PMC_25767277","title":"FKBPL is a critical antiangiogenic regulator of developmental and pathological angiogenesis.","date":"2015","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/25767277","citation_count":34,"is_preprint":false},{"pmid":"23457460","id":"PMC_23457460","title":"The anti-migratory effects of FKBPL and its peptide derivative, AD-01: regulation of CD44 and the cytoskeletal pathway.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23457460","citation_count":34,"is_preprint":false},{"pmid":"23912458","id":"PMC_23912458","title":"Identification of RBCK1 as a novel regulator of FKBPL: implications for tumor growth and response to tamoxifen.","date":"2013","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/23912458","citation_count":33,"is_preprint":false},{"pmid":"21428958","id":"PMC_21428958","title":"The emerging role of FK506-binding proteins as cancer biomarkers: a focus on FKBPL.","date":"2011","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/21428958","citation_count":29,"is_preprint":false},{"pmid":"10866283","id":"PMC_10866283","title":"Increased repair and cell survival in cells treated with DIR1 antisense oligonucleotides: implications for induced radioresistance.","date":"2000","source":"International journal of radiation biology","url":"https://pubmed.ncbi.nlm.nih.gov/10866283","citation_count":29,"is_preprint":false},{"pmid":"20210997","id":"PMC_20210997","title":"Alterations in the steroid hormone receptor co-chaperone FKBPL are associated with male infertility: a case-control study.","date":"2010","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/20210997","citation_count":26,"is_preprint":false},{"pmid":"22265918","id":"PMC_22265918","title":"The therapeutic and diagnostic potential of FKBPL; a novel anticancer protein.","date":"2012","source":"Drug discovery today","url":"https://pubmed.ncbi.nlm.nih.gov/22265918","citation_count":25,"is_preprint":false},{"pmid":"33303872","id":"PMC_33303872","title":"FKBPL is associated with metabolic parameters and is a novel determinant of cardiovascular disease.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33303872","citation_count":25,"is_preprint":false},{"pmid":"38261810","id":"PMC_38261810","title":"The ERF transcription factor LTF1 activates DIR1 to control stereoselective synthesis of antiviral lignans and stress defense in Isatis indigotica roots.","date":"2023","source":"Acta pharmaceutica Sinica. B","url":"https://pubmed.ncbi.nlm.nih.gov/38261810","citation_count":15,"is_preprint":false},{"pmid":"18790546","id":"PMC_18790546","title":"Phloem sap of tomato plants contains a DIR1 putative ortholog.","date":"2008","source":"Journal of plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18790546","citation_count":15,"is_preprint":false},{"pmid":"37375593","id":"PMC_37375593","title":"Vitamins C and D Exhibit Similar Antidepressant Effects to Escitalopram Mediated by NOx and FKBPL in a Stress-Induced Mice Model.","date":"2023","source":"Nutrients","url":"https://pubmed.ncbi.nlm.nih.gov/37375593","citation_count":12,"is_preprint":false},{"pmid":"39251576","id":"PMC_39251576","title":"Cytosolic FKBPL and ER-resident CKAP4 co-regulates ER-phagy and protein secretion.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/39251576","citation_count":10,"is_preprint":false},{"pmid":"25800056","id":"PMC_25800056","title":"WISp39 binds phosphorylated Coronin 1B to regulate Arp2/3 localization and Cofilin-dependent motility.","date":"2015","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25800056","citation_count":10,"is_preprint":false},{"pmid":"36830764","id":"PMC_36830764","title":"FK506-Binding Protein like (FKBPL) Has an Important Role in Heart Failure with Preserved Ejection Fraction Pathogenesis with Potential Diagnostic Utility.","date":"2023","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/36830764","citation_count":8,"is_preprint":false},{"pmid":"17708793","id":"PMC_17708793","title":"[Effect of WISp39 on proliferation, cell cycle and apoptosis of U937 cells].","date":"2007","source":"Zhongguo shi yan xue ye xue za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/17708793","citation_count":7,"is_preprint":false},{"pmid":"34977152","id":"PMC_34977152","title":"Identification of DIR1-Dependant Cellular Responses in Guard Cell Systemic Acquired Resistance.","date":"2021","source":"Frontiers in molecular biosciences","url":"https://pubmed.ncbi.nlm.nih.gov/34977152","citation_count":6,"is_preprint":false},{"pmid":"40069829","id":"PMC_40069829","title":"The FKBPL-based therapeutic peptide, AD-01, protects the endothelium from hypoxia-induced damage by stabilising hypoxia inducible factor-α and inflammation.","date":"2025","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40069829","citation_count":6,"is_preprint":false},{"pmid":"15846062","id":"PMC_15846062","title":"A novel WISp39 protein links Hsp90 and p21 stability to the G2/M checkpoint.","date":"2005","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/15846062","citation_count":5,"is_preprint":false},{"pmid":"36295491","id":"PMC_36295491","title":"Loss of Expression of Antiangiogenic Protein FKBPL in Endometrioid Endometrial Carcinoma: Implications for Clinical Practice.","date":"2022","source":"Medicina (Kaunas, Lithuania)","url":"https://pubmed.ncbi.nlm.nih.gov/36295491","citation_count":4,"is_preprint":false},{"pmid":"34212559","id":"PMC_34212559","title":"A novel mutation in FK506 binding protein-like (FKBPL) causes male infertility.","date":"2021","source":"Croatian medical journal","url":"https://pubmed.ncbi.nlm.nih.gov/34212559","citation_count":3,"is_preprint":false},{"pmid":"38164287","id":"PMC_38164287","title":"Expression and role of FKBPL in lung adenocarcinoma.","date":"2024","source":"Journal of Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/38164287","citation_count":2,"is_preprint":false},{"pmid":"41674464","id":"PMC_41674464","title":"Systemic Loss of FKBPL Uncovers Diabetes-Dependent Pathways of Myocardial and Vascular Injury.","date":"2026","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/41674464","citation_count":0,"is_preprint":false},{"pmid":"37337412","id":"PMC_37337412","title":"Permeabilized whole cells containing co-expressed cyclomaltodextrinase and maltooligosyltrehalose synthase facilitate the synthesis of nonreducing maltoheptaose (N-G7) from β-cyclodextrin.","date":"2023","source":"Journal of the science of food and agriculture","url":"https://pubmed.ncbi.nlm.nih.gov/37337412","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":21492,"output_tokens":5058,"usd":0.070173,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13263,"output_tokens":4145,"usd":0.08497,"stage2_stop_reason":"end_turn"},"total_usd":0.155143,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"WISp39/FKBPL stabilizes newly synthesized p21(WAF1/CIP1) protein by preventing its proteasomal degradation. WISp39, p21, and Hsp90 form a trimeric complex in vivo. Point mutations within the C-terminal TPR domain of WISp39 abolish its interaction with Hsp90; this TPR mutant still binds p21 but fails to stabilize it, demonstrating that Hsp90 recruitment via the TPR domain is required for p21 stabilization. WISp39 siRNA knockdown prevents p21 accumulation and cell cycle arrest after ionizing radiation.\",\n      \"method\": \"Co-IP (trimeric complex), point mutagenesis of TPR domain, siRNA knockdown, proteasome inhibitor assays, cell cycle analysis after ionizing radiation\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, mutagenesis, siRNA, functional cell cycle readout) in a single rigorous study with clear mechanistic conclusions\",\n      \"pmids\": [\"15664193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"WISp39/FKBPL links Hsp90 and p21 stability to the G2/M checkpoint, forming a multi-protein complex critical for a p53-dependent G2 cell cycle checkpoint.\",\n      \"method\": \"Biochemical complex analysis, cell cycle checkpoint assays (commentary/analysis of Jascur et al. findings)\",\n      \"journal\": \"Cancer biology & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — secondary commentary paper referencing the primary Jascur et al. study; no independent new experiments reported\",\n      \"pmids\": [\"15846062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FKBPL and its 24-amino acid peptide derivative AD-01 inhibit endothelial cell migration, tubule formation, and microvessel formation via the cell-surface receptor CD44. CD44 siRNA knockdown or use of CD44-negative cell lines abrogated the antiangiogenic activity of FKBPL and AD-01, establishing CD44 dependency. Signaling downstream of CD44 promotes an antimigratory phenotype.\",\n      \"method\": \"Recombinant protein assays (HMEC-1 migration, tubule formation), ex vivo rat neovascularization model, in vivo sponge implantation and intravital microscopy mouse models, CD44 siRNA knockdown, xenograft tumor models (DU145, MDA-231)\",\n      \"journal\": \"Clinical cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vitro, ex vivo, and in vivo models with genetic (siRNA) and cell-line-based CD44 dependency validation\",\n      \"pmids\": [\"21364036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"FKBPL interacts with estrogen receptor alpha (ERα) and regulates its levels. FKBPL overexpression makes breast cancer cells dependent on estrogen for growth and increases sensitivity to tamoxifen and fulvestrant. FKBPL knockdown decreases p21(WAF1) levels and increases ERα phosphorylation on Ser118 in response to 17β-estradiol and tamoxifen.\",\n      \"method\": \"Stable overexpression and siRNA knockdown in breast cancer cell lines, western blotting for ERα phosphorylation and p21 levels, proliferation assays, drug sensitivity assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal gain/loss-of-function with specific molecular readouts (ERα phosphorylation, p21 levels), single lab\",\n      \"pmids\": [\"20103631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RBCK1 is an FKBPL-interacting protein that regulates FKBPL stability at the post-translational level via ubiquitination. RBCK1, FKBPL, and ERα interact within Hsp90 chaperone complexes, and both FKBPL and RBCK1 associate with ERα at the promoter of the estrogen-responsive gene pS2 to regulate pS2 levels. Both proteins are upregulated by 17β-estradiol.\",\n      \"method\": \"Co-IP (RBCK1-FKBPL interaction), ubiquitination assays, ChIP (promoter association at pS2), siRNA knockdown, stable overexpression clones, proliferation assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ubiquitination assay, ChIP, loss- and gain-of-function) establishing the RBCK1-FKBPL regulatory axis\",\n      \"pmids\": [\"23912458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"FKBPL and its peptide derivative AD-01 bind directly to the CD44 receptor and inhibit tumor cell migration in a CD44-dependent manner. CD44 knockdown abrogated AD-01 binding and its anti-migratory activity. FKBPL overexpression/knockdown or AD-01 treatment regulated CD44 expression levels, suggesting a co-regulatory pathway. Downstream of CD44, AD-01 induced cortical actin reorganization, inhibited Rac-1 activity, upregulated RhoA, and increased actin-binding proteins profilin and vinculin.\",\n      \"method\": \"CD44 siRNA knockdown, FKBPL stable overexpression/siRNA knockdown in HMEC-1 and MDA-MB-231 cells, blocking antibody, actin staining, Rac-1 activity assay, in vivo tumor model\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (siRNA, blocking antibody, binding assay, downstream signaling readouts) in vitro and in vivo confirming CD44-dependent mechanism and cytoskeletal pathway\",\n      \"pmids\": [\"23457460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AD-01 (FKBPL-derived peptide) inhibits breast cancer stem cells (BCSCs) via a CD44-dependent mechanism, inducing BCSC differentiation (reduction in holoclones, increase in meroclones/paraclones) and reducing stem cell markers Nanog, Oct4, and Sox2. FKBPL knockdown increases Nanog/Oct4/Sox2 and the BCSC population. Additive effects observed when AD-01 was combined with Notch inhibitor DAPT.\",\n      \"method\": \"Mammosphere assays, flow cytometry (ESA+/CD44+/CD24- and ALDH+ populations), clonogenic assays, qPCR (stem cell markers), immunofluorescence, xenograft tumor initiation assays\",\n      \"journal\": \"Clinical cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vitro and in vivo methods with gain/loss-of-function establishing CD44-dependent anti-stem cell mechanism\",\n      \"pmids\": [\"23741069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FKBPL is an essential regulator of developmental angiogenesis: Fkbpl knockout mice show embryonic lethality before E8.5. Fkbpl heterozygotes exhibit increased vascular sprouting, enhanced vessel recruitment, and faster tumor growth. In zebrafish, zFkbpl knockdown disrupts vasculature and is rescued by hFKBPL; this rescue is blocked when zcd44 is also knocked down, confirming the CD44 dependency of FKBPL antiangiogenic function in vivo. FKBPL secretion is downregulated by hypoxic signals but not by VEGF or IL-8.\",\n      \"method\": \"Fkbpl knockout/heterozygote mouse generation, zebrafish morpholino knockdown, human FKBPL rescue experiments, ex vivo aortic ring assay, in vivo sponge assay, tumor growth assay in Fkbpl+/- mice\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout/knockdown in two model organisms with rescue experiments and multiple in vivo/ex vivo angiogenesis models\",\n      \"pmids\": [\"25767277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"WISp39/FKBPL binds phosphorylated Coronin 1B and forms a complex with Slingshot phosphatase (SSH), allowing dephosphorylation and activation of Cofilin at the leading edge. WISp39 also regulates Arp2/3 complex localization at the leading edge. WISp39 knockdown causes loss of directional motility and loss of single leading edge morphology; this is rescued by co-overexpression of Coronin 1B with constitutively active Cofilin. The interaction with Hsp90 is required for WISp39's role in directed cell migration.\",\n      \"method\": \"Co-IP (WISp39-Coronin 1B, phospho-specific), siRNA knockdown, rescue with Coronin 1B + constitutively active Cofilin mutant, Arp2/3 localization imaging, directed cell migration assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with phospho-specificity, genetic rescue experiments, and multiple functional readouts establishing the WISp39-Coronin1B-SSH-Cofilin-Arp2/3 pathway\",\n      \"pmids\": [\"25800056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FKBPL overexpression or treatment with FKBPL-based peptides (AD-01, ALM201) inhibit cancer stem cells and cancer metastasis via downregulation of DLL4 and Notch4 protein and/or mRNA expression, in addition to the CD44 pathway. AD-01 inhibited MDA-MB-231 breast cancer cell migration and invasion in vitro and metastasis in vivo. ALM201 inhibits endocrine therapy-resistant mammospheres.\",\n      \"method\": \"Stable overexpression, peptide treatment, in vitro migration/invasion assays, in vivo metastasis model (MDA-MB-231-lucD3H1), limiting dilution assay in SCID mice, western blot and qPCR for DLL4/Notch4, mammosphere assays with tamoxifen-resistant cells\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro and in vivo methods with molecular target identification (DLL4/Notch4), single lab\",\n      \"pmids\": [\"30975104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ALM201 (FKBPL-derived peptide) targets the CD44/STAT3 pathway in ovarian cancer, inhibiting cancer stem cells by inducing differentiation and disrupting angiogenesis.\",\n      \"method\": \"In vitro CSC assays, in vivo xenograft models (Kuramochi, OVCAR3), immunohistochemistry, ELISA, qRT-PCR, RNAseq, western blotting, tissue microarrays\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro and in vivo methods identifying CD44/STAT3 as a downstream pathway, single lab\",\n      \"pmids\": [\"31772325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FKBPL functions as a cytosolic ER-phagy regulator. Overexpression of FKBPL triggers ER fragmentation and ER-phagy. FKBPL acts as a scaffold connecting the ER-resident protein CKAP4 and autophagy adaptors LC3/GABARAPs. CKAP4 bridges FKBPL to ER-phagy cargo. ER-phagy-inducing conditions increase FKBPL-CKAP4 interaction followed by FKBPL oligomerization at the ER. FKBPL-CKAP4 deficiency causes Golgi disassembly, lysosome impairment, and increased ER-derived secretory vesicles with enhanced cytosolic protein secretion via microvesicle shedding.\",\n      \"method\": \"Gain-of-function screen, Co-IP (FKBPL-CKAP4, FKBPL-LC3/GABARAP), overexpression-induced ER fragmentation assays, FKBPL/CKAP4 double knockdown/knockout, ER-phagy flux assays, secretory vesicle/microvesicle analysis, organelle morphology imaging\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phenotype-based screen with multiple orthogonal methods (Co-IP, gain/loss-of-function, organelle imaging, secretion assays) establishing the FKBPL-CKAP4-LC3 scaffold mechanism\",\n      \"pmids\": [\"39251576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"FKBPL enhances androgen receptor (AR) transcriptional activity in reporter assays, suggesting a role in AR-mediated signaling. FKBPL is expressed in testis with expression upregulated at puberty.\",\n      \"method\": \"AR reporter assay (in vitro), RT-PCR, immunohistochemistry, RNA array blot\",\n      \"journal\": \"Reproductive biology and endocrinology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single reporter assay for AR activity, single lab, limited mechanistic follow-up\",\n      \"pmids\": [\"20210997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Repression of DIR1/FKBPL using antisense oligonucleotides in three radioresistant cell lines (V79, RT112, UM-UC-3) significantly increased rates of DNA single-strand break repair and enhanced cell survival after X-ray irradiation; this effect was not observed in the radiosensitive ATBIVA cell line, implicating FKBPL in the mechanism of induced radioresistance.\",\n      \"method\": \"Antisense oligonucleotide transfection, alkaline comet assay (SSB repair), clonogenic survival assay after X-ray irradiation\",\n      \"journal\": \"International journal of radiation biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional loss-of-function with two orthogonal readouts (DNA repair and clonogenic survival) across multiple cell lines including a negative control line\",\n      \"pmids\": [\"10866283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FKBPL expression is downregulated in murine hindlimb ischemia, correlating with increased neovascularization. In a 3D microfluidics model, hypoxia suppresses FKBPL and VE-cadherin, leading to increased endothelial cell migration; AD-01 restores these effects. Proteomic analysis revealed AD-01 treatment in hypoxia enhances tissue remodelling proteins (collagen alpha-1(XIX) chain, JCAD). Under inflammatory conditions, FKBPL and HIF-1α are co-elevated, and AD-01 normalizes their expression without affecting migration.\",\n      \"method\": \"Hindlimb ischemia mouse model (immunofluorescence, RNA extraction), 3D microfluidics cell culture model, siRNA knockdown of FKBPL, LC-MS/MS untargeted proteomics, western blot\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vivo and 3D in vitro models with proteomic target identification and siRNA validation, single lab\",\n      \"pmids\": [\"40069829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"FKBPL knockdown in human aortic endothelial cells reduces VE-cadherin and impairs endothelial barrier function in normal glucose. In high-glucose conditions, FKBPL overexpression inhibits angiogenesis by suppressing FGF and PDGF pathways and activating proinflammatory pathways (TGF-β, leukocyte migration, IL-7 signaling), likely via CD44, and upregulating miR-29b-3p and miR-302b-5p.\",\n      \"method\": \"FKBPL transgenic (fkbpl) mice, streptozotocin-induced diabetes model, FKBPL knockdown/overexpression in endothelial cells, angiogenesis assays, barrier function assay, pathway analysis, miRNA quantification\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo transgenic model plus in vitro mechanistic studies with pathway-level molecular readouts, single lab\",\n      \"pmids\": [\"41674464\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FKBPL (also known as WISp39/DIR1/NG7) is a TPR-domain-containing Hsp90 co-chaperone that: (1) stabilizes p21(WAF1/CIP1) by recruiting Hsp90 into a trimeric complex to prevent proteasomal degradation, thereby regulating the G2/M checkpoint; (2) is itself regulated by RBCK1-mediated ubiquitination within Hsp90-ERα complexes to control estrogen receptor signaling and endocrine therapy response; (3) acts extracellularly as an antiangiogenic protein by binding the CD44 receptor, driving cytoskeletal reorganization (Rac-1 inhibition, RhoA upregulation, cortical actin formation) and inhibiting cell migration; (4) controls directed cell migration intracellularly by binding phospho-Coronin 1B to scaffold Slingshot phosphatase and activate Cofilin while positioning Arp2/3 at the leading edge; (5) suppresses cancer stem cells via DLL4/Notch4 and CD44/STAT3 pathways; (6) is an essential regulator of developmental angiogenesis (embryonic lethal knockout, CD44-dependent in zebrafish); and (7) functions as a cytosolic ER-phagy regulator by scaffolding CKAP4 and LC3/GABARAPs to drive ER fragmentation and autophagy, with its deficiency enhancing protein secretion via microvesicles.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FKBPL (WISp39/DIR1) is a TPR-domain Hsp90 co-chaperone that operates in two distinct compartments: intracellularly it controls protein stability and cytoskeletal dynamics, and extracellularly it acts as a secreted antiangiogenic ligand. As a co-chaperone it stabilizes newly synthesized p21(WAF1/CIP1) by forming a trimeric complex with Hsp90, an interaction that requires the C-terminal TPR domain; loss of FKBPL prevents p21 accumulation and the G2/M cell cycle arrest after ionizing radiation [#0]. FKBPL also engages estrogen receptor alpha within Hsp90 complexes, modulating ERα phosphorylation, p21 levels, and endocrine therapy sensitivity, and is itself subject to RBCK1-mediated ubiquitination that controls its stability and its co-occupancy with ERα at estrogen-responsive promoters [#3, #4]. Through Hsp90, FKBPL further scaffolds directed cell migration by binding phospho-Coronin 1B to position Slingshot phosphatase, activating Cofilin and localizing the Arp2/3 complex at the leading edge [#8]. Secreted FKBPL and its peptide derivatives (AD-01, ALM201) bind the cell-surface receptor CD44 to drive an antimigratory, antiangiogenic phenotype involving Rac-1 inhibition, RhoA upregulation, and cortical actin reorganization [#2, #5], and this CD44 axis is required for FKBPL's essential role in developmental angiogenesis, where knockout is embryonic lethal and zebrafish vascular defects are rescued by human FKBPL in a CD44-dependent manner [#7]. The same secreted activity suppresses cancer stem cells and metastasis through CD44/STAT3 and DLL4/Notch4 signaling [#6, #9, #10]. Most recently, FKBPL was defined as a cytosolic ER-phagy regulator that scaffolds the ER-resident protein CKAP4 to LC3/GABARAP autophagy adaptors, driving ER fragmentation and autophagic turnover, with its deficiency redirecting cargo toward microvesicle-mediated secretion [#11].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established FKBPL's first molecular function: how the cell stabilizes p21 to enforce a DNA-damage cell cycle checkpoint, answering whether a TPR co-chaperone gates p21 turnover.\",\n      \"evidence\": \"Co-IP of a trimeric WISp39-p21-Hsp90 complex, TPR-domain point mutagenesis, siRNA knockdown, and cell cycle analysis after ionizing radiation\",\n      \"pmids\": [\"15664193\", \"15846062\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define how FKBPL physically shields p21 from the proteasome\", \"Substrate range of the Hsp90-FKBPL module beyond p21 not addressed\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Linked FKBPL/DIR1 to acquired radioresistance, raising the question of whether it influences DNA single-strand break repair.\",\n      \"evidence\": \"Antisense oligonucleotide knockdown with alkaline comet assay and clonogenic survival across radioresistant and radiosensitive cell lines\",\n      \"pmids\": [\"10866283\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular mechanism connecting FKBPL to SSB repair machinery\", \"Predates the p21/Hsp90 model and not mechanistically reconciled with it\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Extended FKBPL's chaperone role to hormone receptor signaling, testing whether it regulates ERα levels and endocrine therapy response.\",\n      \"evidence\": \"Reciprocal overexpression/knockdown in breast cancer lines with western blotting for ERα Ser118 phosphorylation, p21, and drug sensitivity assays\",\n      \"pmids\": [\"20103631\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ERα binding versus Hsp90-mediated association not resolved here\", \"AR reporter activity (idx 12) is a separate low-confidence claim not integrated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved how FKBPL itself is regulated and how it acts at estrogen target genes, identifying RBCK1 as the post-translational controller.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, and ChIP at the pS2 promoter with gain/loss-of-function in breast cancer cells\",\n      \"pmids\": [\"23912458\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin chain type and degradative versus non-degradative fate of FKBPL not defined\", \"Stoichiometry within Hsp90-ERα complexes unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined FKBPL's extracellular mechanism: direct CD44 binding driving cytoskeletal reorganization to block migration, angiogenesis, and cancer stem cells.\",\n      \"evidence\": \"Recombinant FKBPL/AD-01 with CD44 siRNA, blocking antibody, Rac-1 activity and actin imaging, mammosphere and xenograft assays\",\n      \"pmids\": [\"21364036\", \"23457460\", \"23741069\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a TPR co-chaperone is secreted and presented to CD44 not established\", \"Structural basis of FKBPL-CD44 binding unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated FKBPL is essential for developmental angiogenesis in vivo and that this function is CD44-dependent.\",\n      \"evidence\": \"Fkbpl knockout/heterozygote mice, zebrafish morpholino knockdown with human FKBPL rescue blocked by cd44 co-knockdown, and ex vivo/in vivo angiogenesis models\",\n      \"pmids\": [\"25767277\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cause of pre-E8.5 embryonic lethality not pinpointed\", \"Connection between intracellular chaperone roles and secreted angiostatic activity in development unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified FKBPL's intracellular cytoskeletal mechanism, showing it scaffolds a phosphatase-cofilin module for directed motility.\",\n      \"evidence\": \"Phospho-specific reciprocal Co-IP of WISp39-Coronin 1B, SSH/Cofilin pathway analysis, Arp2/3 localization imaging, and rescue with Coronin 1B plus constitutively active Cofilin\",\n      \"pmids\": [\"25800056\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between this promigratory intracellular role and the antimigratory extracellular CD44 role not reconciled\", \"Hsp90-dependence mechanism in this context not detailed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Broadened the anti-stem-cell/antimetastatic mechanism beyond CD44 to DLL4/Notch4 and CD44/STAT3 signaling.\",\n      \"evidence\": \"Overexpression and peptide treatment (AD-01, ALM201) with migration/invasion, metastasis, limiting dilution, and CD44/STAT3 and DLL4/Notch4 readouts in breast and ovarian models\",\n      \"pmids\": [\"30975104\", \"31772325\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DLL4/Notch4 and STAT3 effects are downstream of CD44 or parallel not fully separated\", \"Single-lab findings\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a distinct cytosolic function: FKBPL as an ER-phagy scaffold linking CKAP4 to autophagy adaptors and controlling secretory fate.\",\n      \"evidence\": \"Gain-of-function screen, Co-IP of FKBPL-CKAP4 and FKBPL-LC3/GABARAP, double knockdown/knockout, ER-phagy flux and organelle imaging, and microvesicle secretion analysis\",\n      \"pmids\": [\"39251576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger for FKBPL oligomerization at the ER not defined\", \"Relationship between ER-phagy role and Hsp90/CD44 functions unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Positioned FKBPL within ischemic and diabetic vascular contexts, testing how hypoxia and metabolic stress modulate its angiostatic activity.\",\n      \"evidence\": \"Hindlimb ischemia and streptozotocin diabetic mouse models, 3D microfluidics with siRNA/overexpression, LC-MS/MS proteomics, and miRNA quantification\",\n      \"pmids\": [\"40069829\", \"41674464\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal hierarchy among CD44, VE-cadherin, FGF/PDGF/TGF-β pathways, and miRNAs not established\", \"Single-lab pathway-level associations\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how FKBPL's distinct compartmentalized activities — Hsp90/p21 chaperoning, secreted CD44 antiangiogenesis, leading-edge cytoskeletal scaffolding, and cytosolic ER-phagy — are mechanistically coordinated and switched within a single protein.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying structural or regulatory model linking the chaperone, secreted, and ER-phagy functions\", \"Mechanism of FKBPL secretion is undefined\", \"How FKBPL toggles between promigratory (Coronin 1B) and antimigratory (CD44) outcomes is unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [8, 11]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 7]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 5, 7]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [\"FKBPL-p21-Hsp90 trimeric complex\", \"Hsp90-ERα chaperone complex\"],\n    \"partners\": [\"HSP90\", \"CDKN1A\", \"ESR1\", \"RBCK1\", \"CD44\", \"CORO1B\", \"CKAP4\", \"MAP1LC3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}