{"gene":"TESK1","run_date":"2026-04-28T21:42:58","timeline":{"discoveries":[{"year":1995,"finding":"TESK1 is a serine/threonine kinase; protein expressed in COS cells exhibited kinase activity using myelin basic protein as substrate, and the protein contains an N-terminal kinase domain followed by a C-terminal proline-rich region.","method":"In vitro kinase assay with myelin basic protein as substrate; cDNA cloning and sequence analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro kinase assay with defined substrate, original characterization paper","pmids":["8537404"],"is_preprint":false},{"year":2001,"finding":"TESK1 has the potential to phosphorylate cofilin and induce actin cytoskeletal reorganization, and is highly expressed in testicular germ cells.","method":"Transgenic reporter (lacZ linked to TESK1 promoter) and biochemical phosphorylation assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — cofilin phosphorylation mentioned as established capability, supported by reporter expression data","pmids":["11511097"],"is_preprint":false},{"year":2002,"finding":"TESK1 interacts with human Sprouty4 (hSpry4); the interaction was confirmed by coimmunoprecipitation and the two proteins colocalize in cytoplasmic vesicles; the interaction increases upon growth factor stimulation.","method":"Yeast two-hybrid screen, coimmunoprecipitation, colocalization by microscopy","journal":"European journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP confirming yeast two-hybrid interaction, colocalization data","pmids":["12027893"],"is_preprint":false},{"year":2005,"finding":"TESK1 directly interacts with the focal adhesion protein actopaxin via their carboxyl termini; actopaxin binding inhibits TESK1 kinase activity in vitro; the interaction is negatively regulated by adhesion to fibronectin; loss of this interaction impairs cofilin phosphorylation upon matrix adhesion and retards cell spreading.","method":"Direct binding assay (pulldown), in vitro kinase assay, domain mapping, coimmunoprecipitation, cell spreading assay with cofilin phosphorylation readout","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding confirmed, in vitro kinase inhibition demonstrated, multiple orthogonal methods in single study","pmids":["15817463"],"is_preprint":false},{"year":2007,"finding":"Tesk1 binds endogenous Spry2 and relocalizes it to vesicles including endosomes, inhibiting Spry2 translocation to membrane ruffles upon growth factor stimulation; independently of its kinase activity, Tesk1 nullifies Spry2 inhibitory function by abrogating Spry2 interaction with Grb2 and by interfering with Spry2 serine dephosphorylation (impeding Spry2 binding to PP2A catalytic subunit); Tesk1 depletion reduces bFGF-induced neurite outgrowth in PC12 cells.","method":"Coimmunoprecipitation (endogenous proteins and mouse tissues), subcellular localization imaging, kinase-dead mutant analysis, Grb2 interaction assay, PP2A binding assay, siRNA knockdown with neurite outgrowth readout","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including endogenous Co-IP, domain/mutant analysis, knockdown with defined cellular phenotype","pmids":["17974561"],"is_preprint":false},{"year":2008,"finding":"TESK1 binds to and inhibits the kinase MARKK/TAO1, blocking MARKK-induced microtubule disruption; Spred1 binds TESK1 and inhibits TESK1, thereby making F-actin fibers dynamic by reducing cofilin phosphorylation; TESK1 phosphorylates cofilin to stabilize F-actin stress fibers; these three proteins (Spred1, MARKK, TESK1) form a regulatory triangle linking actin and microtubule cytoskeleton dynamics.","method":"Yeast two-hybrid, coimmunoprecipitation, overexpression/inhibition in CHO cells with cytoskeletal readouts (stress fiber formation, MT disruption), cofilin phosphorylation assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal interactions confirmed by Co-IP, multiple orthogonal cellular assays with defined mechanistic outcomes","pmids":["18216281"],"is_preprint":false},{"year":2004,"finding":"In Drosophila, the TESK1 ortholog Cdi (Center divider) acts downstream of Rac1 and upstream of Cofilin in a Rac1-Cdi-Cofilin pathway regulating spermatogenesis; genetic epistasis shows that Cdi expression suppresses dominant-negative Rac1 (Rac1N17) rough-eye phenotype, and Rac1 loss-of-function fertility defects are worsened by cdi loss-of-function.","method":"Genetic epistasis (gain-of-function screen, dominant-negative suppression, double mutant analysis in Drosophila)","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in Drosophila ortholog placing Cdi/TESK1 downstream of Rac1 and upstream of Cofilin","pmids":["15169836"],"is_preprint":false},{"year":2006,"finding":"In Drosophila, the TESK1 ortholog Cdi controls actin organization and adherens junction integrity (DE-cadherin and beta-catenin localization) in the eye epithelium via ADF/cofilin phosphorylation; gain- and loss-of-function of cdi alter apical actin organization and Sevenless RTK apical localization; the ADF/cofilin phosphatase Slingshot (ssh) antagonizes Cdi function.","method":"Gain- and loss-of-function genetics in Drosophila, localization of actin and adherens junction markers, EP modifier screen","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — genetic gain/loss-of-function with defined molecular and cellular phenotypes in Drosophila ortholog","pmids":["17118962"],"is_preprint":false},{"year":2018,"finding":"TESK1 phosphorylates cofilin-1 (CFL1) on the same serine residue as LIMK in glomerular podocytes; in TESK1 knockout podocytes, ROK inhibition (Y27632) effectively reduces phospho-CFL1 levels (whereas in wild-type cells TESK1 compensates for ROK inhibition); TESK1 KO abolishes the motility-promoting effect of ROK inhibition, demonstrating TESK1 regulates podocyte cytoskeletal dynamics.","method":"TESK1 knockout cells, pharmacological ROK inhibition (Y27632), phospho-cofilin western blot, podocyte motility assay","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined molecular (phospho-CFL1) and cellular (motility) phenotypes, genetic and pharmacological dissection","pmids":["30115939"],"is_preprint":false}],"current_model":"TESK1 is a serine/threonine kinase that phosphorylates cofilin on a conserved serine residue to stabilize F-actin stress fibers and regulate cell spreading, focal adhesion formation, and cytoskeletal dynamics; its activity is regulated by direct binding partners including actopaxin (which inhibits TESK1 at focal adhesions upon fibronectin engagement), Spred1 (which inhibits TESK1 to permit actin dynamics), and Sprouty proteins (which TESK1 sequesters to vesicles to modulate RTK-Ras-ERK signaling), while TESK1 itself inhibits MARKK/TAO1 to link actin and microtubule cytoskeleton regulation."},"narrative":{"teleology":[{"year":1995,"claim":"Identification of TESK1 as a novel serine/threonine kinase established the existence of a kinase with an unusual domain architecture — an N-terminal kinase domain and a C-terminal proline-rich region — whose biological substrates remained unknown.","evidence":"cDNA cloning from human testis and in vitro kinase assay using myelin basic protein as substrate in COS cells","pmids":["8537404"],"confidence":"High","gaps":["Physiological substrate not identified","Cellular function unknown","Regulation of kinase activity not explored"]},{"year":2001,"claim":"Demonstration that TESK1 phosphorylates cofilin and is highly expressed in testicular germ cells connected this kinase to actin cytoskeletal regulation and suggested a tissue-specific role in spermatogenesis.","evidence":"Biochemical phosphorylation assay and transgenic lacZ reporter for TESK1 promoter activity","pmids":["11511097"],"confidence":"Medium","gaps":["Specific serine residue on cofilin not confirmed in this study","Functional consequence of cofilin phosphorylation by TESK1 not directly tested in cells"]},{"year":2002,"claim":"Discovery that TESK1 interacts with Sprouty4 and relocalizes it to cytoplasmic vesicles in a growth-factor-stimulated manner revealed a kinase-independent scaffolding function linking TESK1 to RTK signaling.","evidence":"Yeast two-hybrid screen, reciprocal coimmunoprecipitation, and colocalization microscopy in mammalian cells","pmids":["12027893"],"confidence":"Medium","gaps":["Functional consequence for Ras-ERK signaling not tested","Whether kinase activity is required for Sprouty sequestration not determined"]},{"year":2004,"claim":"Genetic epistasis in Drosophila placed the TESK1 ortholog Cdi downstream of Rac1 and upstream of cofilin, establishing an in vivo signaling hierarchy for this kinase in actin-dependent spermatogenesis.","evidence":"Gain-of-function screen and double mutant analysis in Drosophila (Rac1N17 suppression, cdi/Rac1 double loss-of-function fertility defects)","pmids":["15169836"],"confidence":"Medium","gaps":["Direct biochemical link between Rac1 and Cdi not demonstrated","Mechanism of Rac1-dependent Cdi activation unclear"]},{"year":2005,"claim":"Identification of actopaxin as a direct TESK1-binding partner that inhibits TESK1 kinase activity established a mechanism coupling integrin-mediated adhesion to cofilin phosphorylation: fibronectin engagement releases actopaxin inhibition, permitting TESK1-dependent cofilin phosphorylation and cell spreading.","evidence":"Direct pulldown, in vitro kinase assay, coimmunoprecipitation, domain mapping, and cell spreading assay with phospho-cofilin readout","pmids":["15817463"],"confidence":"High","gaps":["How fibronectin adhesion disrupts the actopaxin–TESK1 complex is unknown","Other focal adhesion regulators of TESK1 not explored"]},{"year":2006,"claim":"Demonstration that Drosophila Cdi controls adherens junction integrity and apical actin organization in epithelia via cofilin phosphorylation extended the functional scope of TESK1 beyond spermatogenesis to epithelial morphogenesis and RTK apical localization.","evidence":"Gain- and loss-of-function genetics in Drosophila eye epithelium with DE-cadherin, β-catenin, and actin localization readouts","pmids":["17118962"],"confidence":"Medium","gaps":["Whether mammalian TESK1 similarly regulates adherens junctions not tested","Relationship between cofilin phosphorylation and junction assembly not mechanistically resolved"]},{"year":2007,"claim":"Detailed dissection of TESK1–Sprouty2 interaction revealed a kinase-independent mechanism: TESK1 sequesters Spry2 to endosomal vesicles, blocks Spry2–Grb2 binding, and prevents Spry2 dephosphorylation by PP2A, thereby nullifying Spry2 inhibition of RTK signaling and promoting bFGF-induced neurite outgrowth.","evidence":"Endogenous coimmunoprecipitation (mouse tissues and cells), kinase-dead mutant analysis, Grb2 and PP2A binding assays, siRNA knockdown with neurite outgrowth readout in PC12 cells","pmids":["17974561"],"confidence":"High","gaps":["Whether TESK1 regulates all Sprouty family members equivalently is unclear","Endosomal targeting mechanism for TESK1 not defined"]},{"year":2008,"claim":"Discovery that Spred1 inhibits TESK1, and that TESK1 reciprocally inhibits MARKK/TAO1, established a three-way regulatory circuit linking actin stabilization (via cofilin phosphorylation) and microtubule dynamics (via MARKK inhibition) through a single kinase node.","evidence":"Yeast two-hybrid, coimmunoprecipitation, overexpression/inhibition in CHO cells with stress fiber formation and microtubule disruption readouts","pmids":["18216281"],"confidence":"High","gaps":["Direct phosphorylation of MARKK/TAO1 by TESK1 not demonstrated","Physiological contexts where this triangle operates in vivo not identified"]},{"year":2018,"claim":"Genetic knockout of TESK1 in podocytes demonstrated that TESK1 is a functionally non-redundant cofilin kinase that compensates for ROK pathway inhibition, resolving the question of whether TESK1 and LIMK pathways are interchangeable in regulating cell motility.","evidence":"TESK1 knockout podocytes, pharmacological ROK inhibition (Y27632), phospho-cofilin western blot and motility assay","pmids":["30115939"],"confidence":"High","gaps":["Whether TESK1 loss affects podocyte function in vivo (e.g., proteinuria) is not tested","Relative contributions of TESK1 vs. LIMK to cofilin phosphorylation in other cell types unclear"]},{"year":null,"claim":"The upstream signals that directly activate TESK1 kinase activity (beyond relief of actopaxin inhibition) remain undefined, and no structural model exists for TESK1 or its complexes with regulators.","evidence":"","pmids":[],"confidence":"Low","gaps":["No activating kinase or post-translational modification identified for TESK1","No crystal or cryo-EM structure available","In vivo phenotype of mammalian TESK1 knockout not reported beyond cultured podocytes"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,3,5,8]}],"localization":[{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2,4]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,5]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,5]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[7]}],"complexes":[],"partners":["CFL1","SPRY2","SPRY4","PARVA","SPRED1","TAOK1"],"other_free_text":[]},"mechanistic_narrative":"TESK1 is a serine/threonine kinase that phosphorylates cofilin on its conserved inhibitory serine residue to stabilize F-actin stress fibers and regulate cell spreading, focal adhesion dynamics, and adherens junction integrity [PMID:8537404, PMID:30115939, PMID:17118962]. Its kinase activity toward cofilin is negatively regulated by the focal adhesion adaptor actopaxin (which dissociates from TESK1 upon fibronectin adhesion to permit cofilin phosphorylation and cell spreading) and by Spred1 (which inhibits TESK1 to keep actin fibers dynamic), while TESK1 itself inhibits MARKK/TAO1 to prevent microtubule disruption, forming a regulatory triangle linking actin and microtubule cytoskeleton control [PMID:15817463, PMID:18216281]. Independent of its kinase activity, TESK1 sequesters Sprouty proteins to cytoplasmic vesicles, disrupting Sprouty–Grb2 interaction and thereby modulating RTK-Ras-ERK signaling during processes such as neurite outgrowth [PMID:17974561, PMID:12027893]. In Drosophila, the TESK1 ortholog Cdi acts downstream of Rac1 and upstream of cofilin/Slingshot to control actin organization during spermatogenesis and epithelial morphogenesis [PMID:15169836, PMID:17118962]."},"prefetch_data":{"uniprot":{"accession":"Q15569","full_name":"Dual specificity testis-specific protein kinase 1","aliases":["Testicular protein kinase 1"],"length_aa":626,"mass_kda":67.7,"function":"Dual specificity protein kinase activity catalyzing autophosphorylation and phosphorylation of exogenous substrates on both serine/threonine and tyrosine residues (By similarity). Regulates the cellular cytoskeleton by enhancing actin stress fiber formation via phosphorylation of cofilin and by preventing microtubule breakdown via inhibition of TAOK1/MARKK kinase activity (By similarity). Inhibits podocyte motility via regulation of actin cytoskeletal dynamics and phosphorylation of CFL1 (By similarity). Positively regulates integrin-mediated cell spreading, via phosphorylation of cofilin (PubMed:15584898). Suppresses ciliogenesis via multiple pathways; phosphorylation of CFL1, suppression of ciliary vesicle directional trafficking to the ciliary base, and by facilitating YAP1 nuclear localization where it acts as a transcriptional corepressor of the TEAD4 target genes AURKA and PLK1 (PubMed:25849865). Probably plays a central role at and after the meiotic phase of spermatogenesis (By similarity)","subcellular_location":"Cytoplasm; Cytoplasm, perinuclear region; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Cell projection, lamellipodium","url":"https://www.uniprot.org/uniprotkb/Q15569/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TESK1","classification":"Not Classified","n_dependent_lines":11,"n_total_lines":1208,"dependency_fraction":0.009105960264900662},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TESK1","total_profiled":1310},"omim":[{"mim_id":"607984","title":"SPROUTY RTK SIGNALING ANTAGONIST 4; SPRY4","url":"https://www.omim.org/entry/607984"},{"mim_id":"604746","title":"TESTIS-ASSOCIATED ACTIN-MODELING KINASE 2; TESK2","url":"https://www.omim.org/entry/604746"},{"mim_id":"601782","title":"TESTIS-ASSOCIATED ACTIN-MODELING KINASE 1; TESK1","url":"https://www.omim.org/entry/601782"}],"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/TESK1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q15569","domains":[{"cath_id":"3.30.200.20","chopping":"49-131","consensus_level":"high","plddt":86.6542,"start":49,"end":131},{"cath_id":"1.10.510.10","chopping":"136-319_354-369_378-384","consensus_level":"high","plddt":90.7756,"start":136,"end":384}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15569","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15569-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15569-F1-predicted_aligned_error_v6.png","plddt_mean":61.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TESK1","jax_strain_url":"https://www.jax.org/strain/search?query=TESK1"},"sequence":{"accession":"Q15569","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15569.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15569/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15569"}},"corpus_meta":[{"pmid":"12027893","id":"PMC_12027893","title":"Human sprouty 4, a new ras antagonist on 5q31, interacts with the dual specificity kinase TESK1.","date":"2002","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12027893","citation_count":85,"is_preprint":false},{"pmid":"8537404","id":"PMC_8537404","title":"Identification and characterization of a novel protein kinase, TESK1, specifically expressed in testicular germ cells.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8537404","citation_count":70,"is_preprint":false},{"pmid":"18216281","id":"PMC_18216281","title":"Spred1 and TESK1--two new interaction partners of the kinase MARKK/TAO1 that link the microtubule and actin cytoskeleton.","date":"2008","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/18216281","citation_count":54,"is_preprint":false},{"pmid":"15817463","id":"PMC_15817463","title":"Actopaxin interacts with TESK1 to regulate cell spreading on fibronectin.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15817463","citation_count":42,"is_preprint":false},{"pmid":"9705840","id":"PMC_9705840","title":"Stage-specific expression of testis-specific protein kinase 1 (TESK1) in rat spermatogenic cells.","date":"1998","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9705840","citation_count":33,"is_preprint":false},{"pmid":"17974561","id":"PMC_17974561","title":"Tesk1 interacts with Spry2 to abrogate its inhibition of ERK phosphorylation downstream of receptor tyrosine kinase signaling.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17974561","citation_count":32,"is_preprint":false},{"pmid":"15169836","id":"PMC_15169836","title":"A screen for modifiers of RacGAP(84C) gain-of-function in the Drosophila eye revealed the LIM kinase Cdi/TESK1 as a downstream effector of Rac1 during spermatogenesis.","date":"2004","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/15169836","citation_count":21,"is_preprint":false},{"pmid":"25271995","id":"PMC_25271995","title":"Cloning and characterization of tesk1, a novel spermatogenesis-related gene, in the tongue sole (Cynoglossus semilaevis).","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25271995","citation_count":20,"is_preprint":false},{"pmid":"11511097","id":"PMC_11511097","title":"Cell-type-specific expression of a TESK1 promoter-linked lacZ gene in transgenic mice.","date":"2001","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/11511097","citation_count":19,"is_preprint":false},{"pmid":"29396473","id":"PMC_29396473","title":"Decreased TESK1-mediated cofilin 1 phosphorylation in the jejunum of IBS-D patients may explain increased female predisposition to epithelial dysfunction.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29396473","citation_count":18,"is_preprint":false},{"pmid":"10390152","id":"PMC_10390152","title":"Drosophila center divider gene is expressed in CNS midline cells and encodes a developmentally regulated protein kinase orthologous to human TESK1.","date":"1999","source":"DNA and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/10390152","citation_count":17,"is_preprint":false},{"pmid":"9469938","id":"PMC_9469938","title":"Structural organization and chromosomal localization of the mouse tesk1 (testis-specific protein kinase 1) gene.","date":"1998","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/9469938","citation_count":12,"is_preprint":false},{"pmid":"30115939","id":"PMC_30115939","title":"Regulation of cofilin phosphorylation in glomerular podocytes by testis specific kinase 1 (TESK1).","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30115939","citation_count":10,"is_preprint":false},{"pmid":"17118962","id":"PMC_17118962","title":"The Cdi/TESK1 kinase is required for Sevenless signaling and epithelial organization in the Drosophila eye.","date":"2006","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/17118962","citation_count":7,"is_preprint":false},{"pmid":"26869317","id":"PMC_26869317","title":"Expression analysis and characterization of an autosome-localized tesk1 gene in half-smooth tongue sole (Cynoglossus semilaevis).","date":"2016","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/26869317","citation_count":5,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8406,"output_tokens":2373,"usd":0.030406},"stage2":{"model":"claude-opus-4-6","input_tokens":5662,"output_tokens":2593,"usd":0.139703},"total_usd":0.170109,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"TESK1 is a serine/threonine kinase; protein expressed in COS cells exhibited kinase activity using myelin basic protein as substrate, and the protein contains an N-terminal kinase domain followed by a C-terminal proline-rich region.\",\n      \"method\": \"In vitro kinase assay with myelin basic protein as substrate; cDNA cloning and sequence analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro kinase assay with defined substrate, original characterization paper\",\n      \"pmids\": [\"8537404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"TESK1 has the potential to phosphorylate cofilin and induce actin cytoskeletal reorganization, and is highly expressed in testicular germ cells.\",\n      \"method\": \"Transgenic reporter (lacZ linked to TESK1 promoter) and biochemical phosphorylation assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cofilin phosphorylation mentioned as established capability, supported by reporter expression data\",\n      \"pmids\": [\"11511097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"TESK1 interacts with human Sprouty4 (hSpry4); the interaction was confirmed by coimmunoprecipitation and the two proteins colocalize in cytoplasmic vesicles; the interaction increases upon growth factor stimulation.\",\n      \"method\": \"Yeast two-hybrid screen, coimmunoprecipitation, colocalization by microscopy\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP confirming yeast two-hybrid interaction, colocalization data\",\n      \"pmids\": [\"12027893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"TESK1 directly interacts with the focal adhesion protein actopaxin via their carboxyl termini; actopaxin binding inhibits TESK1 kinase activity in vitro; the interaction is negatively regulated by adhesion to fibronectin; loss of this interaction impairs cofilin phosphorylation upon matrix adhesion and retards cell spreading.\",\n      \"method\": \"Direct binding assay (pulldown), in vitro kinase assay, domain mapping, coimmunoprecipitation, cell spreading assay with cofilin phosphorylation readout\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding confirmed, in vitro kinase inhibition demonstrated, multiple orthogonal methods in single study\",\n      \"pmids\": [\"15817463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Tesk1 binds endogenous Spry2 and relocalizes it to vesicles including endosomes, inhibiting Spry2 translocation to membrane ruffles upon growth factor stimulation; independently of its kinase activity, Tesk1 nullifies Spry2 inhibitory function by abrogating Spry2 interaction with Grb2 and by interfering with Spry2 serine dephosphorylation (impeding Spry2 binding to PP2A catalytic subunit); Tesk1 depletion reduces bFGF-induced neurite outgrowth in PC12 cells.\",\n      \"method\": \"Coimmunoprecipitation (endogenous proteins and mouse tissues), subcellular localization imaging, kinase-dead mutant analysis, Grb2 interaction assay, PP2A binding assay, siRNA knockdown with neurite outgrowth readout\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including endogenous Co-IP, domain/mutant analysis, knockdown with defined cellular phenotype\",\n      \"pmids\": [\"17974561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TESK1 binds to and inhibits the kinase MARKK/TAO1, blocking MARKK-induced microtubule disruption; Spred1 binds TESK1 and inhibits TESK1, thereby making F-actin fibers dynamic by reducing cofilin phosphorylation; TESK1 phosphorylates cofilin to stabilize F-actin stress fibers; these three proteins (Spred1, MARKK, TESK1) form a regulatory triangle linking actin and microtubule cytoskeleton dynamics.\",\n      \"method\": \"Yeast two-hybrid, coimmunoprecipitation, overexpression/inhibition in CHO cells with cytoskeletal readouts (stress fiber formation, MT disruption), cofilin phosphorylation assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal interactions confirmed by Co-IP, multiple orthogonal cellular assays with defined mechanistic outcomes\",\n      \"pmids\": [\"18216281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In Drosophila, the TESK1 ortholog Cdi (Center divider) acts downstream of Rac1 and upstream of Cofilin in a Rac1-Cdi-Cofilin pathway regulating spermatogenesis; genetic epistasis shows that Cdi expression suppresses dominant-negative Rac1 (Rac1N17) rough-eye phenotype, and Rac1 loss-of-function fertility defects are worsened by cdi loss-of-function.\",\n      \"method\": \"Genetic epistasis (gain-of-function screen, dominant-negative suppression, double mutant analysis in Drosophila)\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in Drosophila ortholog placing Cdi/TESK1 downstream of Rac1 and upstream of Cofilin\",\n      \"pmids\": [\"15169836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In Drosophila, the TESK1 ortholog Cdi controls actin organization and adherens junction integrity (DE-cadherin and beta-catenin localization) in the eye epithelium via ADF/cofilin phosphorylation; gain- and loss-of-function of cdi alter apical actin organization and Sevenless RTK apical localization; the ADF/cofilin phosphatase Slingshot (ssh) antagonizes Cdi function.\",\n      \"method\": \"Gain- and loss-of-function genetics in Drosophila, localization of actin and adherens junction markers, EP modifier screen\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic gain/loss-of-function with defined molecular and cellular phenotypes in Drosophila ortholog\",\n      \"pmids\": [\"17118962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TESK1 phosphorylates cofilin-1 (CFL1) on the same serine residue as LIMK in glomerular podocytes; in TESK1 knockout podocytes, ROK inhibition (Y27632) effectively reduces phospho-CFL1 levels (whereas in wild-type cells TESK1 compensates for ROK inhibition); TESK1 KO abolishes the motility-promoting effect of ROK inhibition, demonstrating TESK1 regulates podocyte cytoskeletal dynamics.\",\n      \"method\": \"TESK1 knockout cells, pharmacological ROK inhibition (Y27632), phospho-cofilin western blot, podocyte motility assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined molecular (phospho-CFL1) and cellular (motility) phenotypes, genetic and pharmacological dissection\",\n      \"pmids\": [\"30115939\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TESK1 is a serine/threonine kinase that phosphorylates cofilin on a conserved serine residue to stabilize F-actin stress fibers and regulate cell spreading, focal adhesion formation, and cytoskeletal dynamics; its activity is regulated by direct binding partners including actopaxin (which inhibits TESK1 at focal adhesions upon fibronectin engagement), Spred1 (which inhibits TESK1 to permit actin dynamics), and Sprouty proteins (which TESK1 sequesters to vesicles to modulate RTK-Ras-ERK signaling), while TESK1 itself inhibits MARKK/TAO1 to link actin and microtubule cytoskeleton regulation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TESK1 is a serine/threonine kinase that phosphorylates cofilin on its conserved inhibitory serine residue to stabilize F-actin stress fibers and regulate cell spreading, focal adhesion dynamics, and adherens junction integrity [PMID:8537404, PMID:30115939, PMID:17118962]. Its kinase activity toward cofilin is negatively regulated by the focal adhesion adaptor actopaxin (which dissociates from TESK1 upon fibronectin adhesion to permit cofilin phosphorylation and cell spreading) and by Spred1 (which inhibits TESK1 to keep actin fibers dynamic), while TESK1 itself inhibits MARKK/TAO1 to prevent microtubule disruption, forming a regulatory triangle linking actin and microtubule cytoskeleton control [PMID:15817463, PMID:18216281]. Independent of its kinase activity, TESK1 sequesters Sprouty proteins to cytoplasmic vesicles, disrupting Sprouty–Grb2 interaction and thereby modulating RTK-Ras-ERK signaling during processes such as neurite outgrowth [PMID:17974561, PMID:12027893]. In Drosophila, the TESK1 ortholog Cdi acts downstream of Rac1 and upstream of cofilin/Slingshot to control actin organization during spermatogenesis and epithelial morphogenesis [PMID:15169836, PMID:17118962].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Identification of TESK1 as a novel serine/threonine kinase established the existence of a kinase with an unusual domain architecture — an N-terminal kinase domain and a C-terminal proline-rich region — whose biological substrates remained unknown.\",\n      \"evidence\": \"cDNA cloning from human testis and in vitro kinase assay using myelin basic protein as substrate in COS cells\",\n      \"pmids\": [\"8537404\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrate not identified\", \"Cellular function unknown\", \"Regulation of kinase activity not explored\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstration that TESK1 phosphorylates cofilin and is highly expressed in testicular germ cells connected this kinase to actin cytoskeletal regulation and suggested a tissue-specific role in spermatogenesis.\",\n      \"evidence\": \"Biochemical phosphorylation assay and transgenic lacZ reporter for TESK1 promoter activity\",\n      \"pmids\": [\"11511097\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific serine residue on cofilin not confirmed in this study\", \"Functional consequence of cofilin phosphorylation by TESK1 not directly tested in cells\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Discovery that TESK1 interacts with Sprouty4 and relocalizes it to cytoplasmic vesicles in a growth-factor-stimulated manner revealed a kinase-independent scaffolding function linking TESK1 to RTK signaling.\",\n      \"evidence\": \"Yeast two-hybrid screen, reciprocal coimmunoprecipitation, and colocalization microscopy in mammalian cells\",\n      \"pmids\": [\"12027893\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence for Ras-ERK signaling not tested\", \"Whether kinase activity is required for Sprouty sequestration not determined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Genetic epistasis in Drosophila placed the TESK1 ortholog Cdi downstream of Rac1 and upstream of cofilin, establishing an in vivo signaling hierarchy for this kinase in actin-dependent spermatogenesis.\",\n      \"evidence\": \"Gain-of-function screen and double mutant analysis in Drosophila (Rac1N17 suppression, cdi/Rac1 double loss-of-function fertility defects)\",\n      \"pmids\": [\"15169836\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical link between Rac1 and Cdi not demonstrated\", \"Mechanism of Rac1-dependent Cdi activation unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of actopaxin as a direct TESK1-binding partner that inhibits TESK1 kinase activity established a mechanism coupling integrin-mediated adhesion to cofilin phosphorylation: fibronectin engagement releases actopaxin inhibition, permitting TESK1-dependent cofilin phosphorylation and cell spreading.\",\n      \"evidence\": \"Direct pulldown, in vitro kinase assay, coimmunoprecipitation, domain mapping, and cell spreading assay with phospho-cofilin readout\",\n      \"pmids\": [\"15817463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How fibronectin adhesion disrupts the actopaxin–TESK1 complex is unknown\", \"Other focal adhesion regulators of TESK1 not explored\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstration that Drosophila Cdi controls adherens junction integrity and apical actin organization in epithelia via cofilin phosphorylation extended the functional scope of TESK1 beyond spermatogenesis to epithelial morphogenesis and RTK apical localization.\",\n      \"evidence\": \"Gain- and loss-of-function genetics in Drosophila eye epithelium with DE-cadherin, β-catenin, and actin localization readouts\",\n      \"pmids\": [\"17118962\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether mammalian TESK1 similarly regulates adherens junctions not tested\", \"Relationship between cofilin phosphorylation and junction assembly not mechanistically resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Detailed dissection of TESK1–Sprouty2 interaction revealed a kinase-independent mechanism: TESK1 sequesters Spry2 to endosomal vesicles, blocks Spry2–Grb2 binding, and prevents Spry2 dephosphorylation by PP2A, thereby nullifying Spry2 inhibition of RTK signaling and promoting bFGF-induced neurite outgrowth.\",\n      \"evidence\": \"Endogenous coimmunoprecipitation (mouse tissues and cells), kinase-dead mutant analysis, Grb2 and PP2A binding assays, siRNA knockdown with neurite outgrowth readout in PC12 cells\",\n      \"pmids\": [\"17974561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TESK1 regulates all Sprouty family members equivalently is unclear\", \"Endosomal targeting mechanism for TESK1 not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Discovery that Spred1 inhibits TESK1, and that TESK1 reciprocally inhibits MARKK/TAO1, established a three-way regulatory circuit linking actin stabilization (via cofilin phosphorylation) and microtubule dynamics (via MARKK inhibition) through a single kinase node.\",\n      \"evidence\": \"Yeast two-hybrid, coimmunoprecipitation, overexpression/inhibition in CHO cells with stress fiber formation and microtubule disruption readouts\",\n      \"pmids\": [\"18216281\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct phosphorylation of MARKK/TAO1 by TESK1 not demonstrated\", \"Physiological contexts where this triangle operates in vivo not identified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Genetic knockout of TESK1 in podocytes demonstrated that TESK1 is a functionally non-redundant cofilin kinase that compensates for ROK pathway inhibition, resolving the question of whether TESK1 and LIMK pathways are interchangeable in regulating cell motility.\",\n      \"evidence\": \"TESK1 knockout podocytes, pharmacological ROK inhibition (Y27632), phospho-cofilin western blot and motility assay\",\n      \"pmids\": [\"30115939\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TESK1 loss affects podocyte function in vivo (e.g., proteinuria) is not tested\", \"Relative contributions of TESK1 vs. LIMK to cofilin phosphorylation in other cell types unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The upstream signals that directly activate TESK1 kinase activity (beyond relief of actopaxin inhibition) remain undefined, and no structural model exists for TESK1 or its complexes with regulators.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No activating kinase or post-translational modification identified for TESK1\", \"No crystal or cryo-EM structure available\", \"In vivo phenotype of mammalian TESK1 knockout not reported beyond cultured podocytes\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 3, 5, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"CFL1\",\n      \"SPRY2\",\n      \"SPRY4\",\n      \"PARVA\",\n      \"SPRED1\",\n      \"TAOK1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}