{"gene":"SLK","run_date":"2026-06-10T07:46:35","timeline":{"discoveries":[{"year":1999,"finding":"SLK overexpression activates c-Jun N-terminal kinase 1 (JNK1), and prolonged overexpression induces apoptosis in cultured fibroblasts. SLK colocalizes to distinct cytosolic domains, preferentially at the cell periphery.","method":"In vitro kinase assay, immunofluorescence, annexin-V/TUNEL staining","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — overexpression with functional readout and JNK1 activation, single lab but multiple assays","pmids":["10602516"],"is_preprint":false},{"year":2000,"finding":"Caspase 3 cleaves SLK in vitro and in vivo during apoptosis, releasing an activated N-terminal kinase domain that promotes apoptosis and cytoskeletal rearrangements, and a C-terminal domain (AT1-46 homology domain) that independently disassembles actin stress fibers. SLK overexpression also activates the JNK signaling pathway.","method":"Caspase 3 cleavage assay in vitro and in vivo, annexin V/TUNEL, dominant-domain overexpression, immunofluorescence","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro and in vivo caspase cleavage demonstrated, multiple functional domain readouts, replicated with multiple apoptotic stimuli","pmids":["10611247"],"is_preprint":false},{"year":2000,"finding":"SLK can phosphorylate and activate murine Plk1. Endogenous SLK activity increases during G2 phase progression. SLK protein levels decrease in quiescent and differentiating cells. Okadaic acid treatment induces phosphorylation-dependent enhancement of SLK activity.","method":"In vitro kinase assay (SLK phosphorylating Plk1), cell cycle synchronization with kinase activity measurement","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay demonstrating SLK→Plk1 phosphorylation, single lab with cell cycle activity measurements","pmids":["10886374"],"is_preprint":false},{"year":2002,"finding":"SLK associates with the microtubule network and co-precipitates with alpha-tubulin. SLK redistributes to podosome-like adhesion sites in fibronectin-stimulated fibroblasts but its kinase activity is not modulated by fibronectin. Ectopic expression of activated SLK induces actin stress fiber disassembly that is inhibited by dominant negative Rac1, and endogenous SLK colocalizes with Rac1 in spreading cells.","method":"Co-immunoprecipitation with alpha-tubulin, immunofluorescence, microinjection with dominant negative Rac1, adenoviral overexpression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — co-precipitation confirmed microtubule association, epistasis with dominant-negative Rac1 placed SLK upstream, single lab","pmids":["12151406"],"is_preprint":false},{"year":2005,"finding":"SLK phosphorylates and increases activity of apoptosis signal-regulating kinase-1 (ASK1), which in turn stimulates p38 MAPK phosphorylation (but not JNK or ERK). SLK undergoes homodimerization via its C-terminal domain, and dimerization enhances SLK kinase activity. SLK activity is stimulated by chemical anoxia/recovery (ischemia-reperfusion in cell culture).","method":"In vitro kinase assay, co-immunoprecipitation for dimerization, ASK1 phosphorylation assay, p38/JNK/ERK phosphorylation Western blot","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay showing ASK1 as substrate, dimerization confirmed by co-IP, single lab with multiple orthogonal methods","pmids":["16316999"],"is_preprint":false},{"year":2005,"finding":"SLK co-localizes with the mitotic spindle during mitosis. Expression of kinase-inactive SLK or SLK siRNA causes G2 accumulation with failure to down-regulate cyclin A, low phospho-H3 and low active p34/cdc2. Overexpression of active SLK induces ectopic spindle assembly and triggers cell cycle re-entry in Xenopus oocytes, placing SLK upstream of H1 kinase activation.","method":"Immunofluorescence, kinase-dead mutant/siRNA knockdown, cyclin expression Western blot, Xenopus oocyte microinjection","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD and KO with cell cycle phenotype, Xenopus oocyte functional assay, single lab","pmids":["16236704"],"is_preprint":false},{"year":2006,"finding":"v-Src expression down-regulates SLK kinase activity indirectly by inducing casein kinase II (CK2) to phosphorylate SLK at serine residues 347/348. CK2 directly phosphorylates SLK at these positions, and CK2 inhibition in v-Src-transformed cells restores normal SLK activity. CK2 and SLK co-localize in fibroblasts spreading on fibronectin.","method":"In vitro kinase assay, deletion analysis, CK2 inhibitor treatment, immunofluorescence co-localization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro phosphorylation of SLK by CK2 at defined sites confirmed by deletion analysis, single lab","pmids":["16837460"],"is_preprint":false},{"year":2008,"finding":"SLK phosphorylates RhoA on Ser188 downstream of angiotensin II type 2 receptor (AT2R) activation, independently of cAMP/cGMP-activated kinases. The signaling cascade involves SHP-1 and casein kinase II activating SLK, which then phosphorylates RhoA to induce GDI-mediated cytosolic sequestration of RhoA and inhibition of arterial contraction/vasodilation.","method":"In vitro kinase assay, site-directed mutagenesis of RhoA Ser188, signaling inhibitor experiments in vascular smooth muscle cells","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay with defined substrate site, signaling cascade dissected with multiple inhibitors, functional vascular readout","pmids":["18420945"],"is_preprint":false},{"year":2008,"finding":"SLK phosphorylates Plk1 on Thr210 in its activation segment, increasing Plk1 catalytic efficiency ~202-fold (k_cat increase 88-fold, K_M decrease 2.3-fold). The presence of a polo-box domain-binding phosphopeptide further amplifies the effect of Slk phosphorylation (combined 1515-fold increase in catalytic efficiency).","method":"In vitro reconstituted kinase assay with purified Plk1 and Slk, quantitative k_cat/K_M measurements using TCTP as substrate","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — quantitative in vitro reconstitution with purified proteins, kinetic parameters measured, mechanistic model validated","pmids":["18298087"],"is_preprint":false},{"year":2008,"finding":"SLK (LOSK) associates with centrosomes and microtubules. Inhibition of SLK activity (dominant-negative K63R or RNAi) results in loss of dynactin from centrosomes, inability of centrosomes to anchor/cap microtubules (though nucleation is preserved), and disorganization of the microtubule radial array. Cells with suppressed SLK cannot polarize the Golgi complex at the wound edge.","method":"Dominant-negative expression, RNAi knockdown, immunofluorescence of dynactin/centrosomes/microtubules","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — DN and RNAi with clear centrosomal/microtubule phenotype, single lab","pmids":["18287541"],"is_preprint":false},{"year":2008,"finding":"SLK is required for focal adhesion turnover and cell migration downstream of the FAK/c-Src complex. SLK co-localizes with paxillin, Rac1, and microtubules at the leading edge. SLK is activated by scratch wounding, dependent on FAK/c-Src/MAPK signaling, while recruitment to the leading edge is Src-dependent but FAK-independent.","method":"Knockdown, dominant-negative SLK, scratch wound kinase activity assay, co-localization immunofluorescence, signaling inhibitor dissection","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown with FA turnover phenotype, epistasis with FAK/Src inhibitors, single lab with multiple methods","pmids":["18382658"],"is_preprint":false},{"year":2009,"finding":"SLK is required for ErbB2/Neu-dependent cell migration. Heregulin treatment or activated Neu overexpression stimulates SLK activity via MEK, PI3K, PLCγ, Shc, FAK, and Src signaling. Phosphorylation of Neu at Y1201 or Y1226/7 is required for SLK activation and cancer cell migration/invasion.","method":"SLK knockdown, kinase-inactive SLK overexpression, signaling pathway inhibitors, migration/invasion assays, phospho-FAK analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD/dominant-negative with functional migration assays plus signaling pathway dissection, single lab","pmids":["19525980"],"is_preprint":false},{"year":2009,"finding":"SLK promotes p53 phosphorylation on Ser-33 and Ser-315, and stimulates p53 transcriptional activity. Mutation of both S33A and S315A abolishes SLK-induced p53 transactivation. SLK-induced p53 activation is attenuated by JNK inhibition. SLK overexpression amplifies ischemia-reperfusion-induced apoptosis in a p53-dependent manner.","method":"p53 reporter (luciferase), site-directed mutagenesis of p53, JNK inhibitor, dominant-negative SLK, pifithrin-alpha inhibitor","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay with mutagenesis defining required p53 phosphorylation sites, single lab","pmids":["19640899"],"is_preprint":false},{"year":2009,"finding":"SLK interacts directly with the transcriptional cofactors Ldb1/CLIM2 and Ldb2/CLIM1 via its C-terminal AT1-46 homology domain, as demonstrated in vitro and in vivo. Ldb1/2 co-localize with SLK in migrating cells, and both knockdown and overexpression of Ldb1/2 increase cell motility. Ldb1/2 are proposed to maintain SLK in an inactive state.","method":"In vitro binding assay, co-immunoprecipitation, immunofluorescence co-localization, siRNA knockdown migration assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct in vitro binding confirmed, reciprocal Co-IP, functional knockdown, single lab","pmids":["19675209"],"is_preprint":false},{"year":2011,"finding":"Controlled homodimerization of the SLK catalytic domain (via FK506-binding protein fusion) enhances kinase activity, activation-specific phosphorylation of JNK and p38, Bax promoter activity, and apoptosis compared to monomeric SLK.","method":"Regulated dimerization system (Fv-SLK + AP20187), in vitro kinase assay, Western blot for JNK/p38 phosphorylation, apoptosis assay","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — regulated dimerization system with in vitro kinase assay and downstream pathway readouts, single lab","pmids":["21677149"],"is_preprint":false},{"year":2011,"finding":"Phosphorylation of Thr-183 and Ser-189 in the SLK activation segment is required for kinase activity and downstream signaling. T183A, S189A, and T183A/S189A mutants show reduced kinase activity, fail to activate JNK/p38 or AP-1, and do not induce apoptosis. Homodimerization enhances SLK autophosphorylation at T183/S189; the T183A/S189A double mutant is not activated by dimerization.","method":"Site-directed mutagenesis of activation segment, in vitro kinase assay, JNK/p38 phosphorylation Western blot, AP-1 reporter, regulated dimerization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — activation segment mutagenesis combined with in vitro kinase assay, downstream signaling, and regulated dimerization in same study","pmids":["22203681"],"is_preprint":false},{"year":2012,"finding":"LOK and SLK are the relevant kinases that phosphorylate ezrin at the apical membrane of polarized epithelial cells, restricting microvilli to the apical domain. Both kinases are enriched in microvilli and locally activated there. Unregulated kinase activity causes ezrin mislocalization to the basolateral domain, while expression of kinase regulatory regions inhibits endogenous ezrin phosphorylation locally.","method":"Proteomic identification, RNAi knockdown, drug-resistant kinase variants, live imaging, subcellular fractionation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomic identification plus functional RNAi plus drug-resistant rescue variants, multiple orthogonal approaches, replicated","pmids":["23209304"],"is_preprint":false},{"year":2012,"finding":"SLK phosphorylates paxillin on Ser-250 in vitro, and this phosphorylation is required for paxillin redistribution and cell motility. S250A paxillin mutation prevents SLK-dependent phosphorylation and results in impaired migration and accumulation of phospho-FAK-Tyr397, indicating altered focal adhesion dynamics.","method":"In vitro kinase assay with paxillin S250 as substrate, S250A mutant in migration assay, phospho-FAK Western blot, focal adhesion turnover analysis","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay defining substrate phosphosite, mutagenesis confirming site requirement, functional migration readout","pmids":["23128389"],"is_preprint":false},{"year":2013,"finding":"SLK (LOSK) phosphorylates the p150(Glued) subunit of dynactin (isoform 1A only), targeting it to the centrosome to maintain microtubule radial organization. Phosphorylation is required only for centrosomal localization of p150(Glued), not for its microtubule-organizing properties. Artificial targeting of non-phosphorylatable p150(Glued) to the centrosome rescues microtubule organization in SLK-inhibited cells. Dynactin phosphorylation is also involved in Golgi reorientation in polarized cells.","method":"In vitro kinase assay (SLK phosphorylating p150(Glued)), isoform-specific phosphorylation analysis, artificial centrosomal targeting rescue experiment, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay identifying substrate, functional rescue by artificial targeting dissecting phosphorylation from localization, mechanistic clarity","pmids":["23985322"],"is_preprint":false},{"year":2014,"finding":"SLK directly and strongly activates ERM proteins (ezrin/radixin/moesin) at mitotic entry in mammalian cells. ERM activation by SLK promotes polarized association of LGN and NuMA at the mitotic cortex, which is required for correct spindle orientation. Impairing ERM activation in mouse embryonic neocortical apical progenitors severely disrupts spindle orientation in vivo.","method":"In vitro kinase assay, microfabricated adhesive substrates for spindle axis control, LGN/NuMA immunofluorescence at cortex, in vivo mouse cortex analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct in vitro kinase assay, functional spindle orientation assay on adhesive substrates, in vivo mouse cortex validation","pmids":["24958772"],"is_preprint":false},{"year":2015,"finding":"LMO4 directly binds to SLK and activates its kinase activity in vitro and in vivo. LMO4 co-precipitates with SLK after scratch wounding. Cre-mediated deletion of LMO4 inhibits cell migration, SLK activation, and recruitment of SLK and Ldb1 to the leading edge. Src/Yes/Fyn-deficient (SYF) cells with low LMO4 fail to recruit SLK to the leading edge; re-expression of wild-type LMO4 but not a mutant restores SLK localization and activity.","method":"In vitro kinase assay, Co-IP after wounding, conditional LMO4 knockout, SYF cells re-expression, immunofluorescence of leading edge localization","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay plus conditional KO with rescue, multiple methods, single lab","pmids":["25882817"],"is_preprint":false},{"year":2015,"finding":"SLK interacts with nucleoporin Tpr and cytoskeletal protein α-actinin-4 via its 350 amino acid C-terminal coiled-coil domain. Subsets of SLK colocalize with Tpr at the nuclear envelope and with α-actinin-4 in the cytoplasm. Tpr expression attenuates SLK autophosphorylation and blocks SLK-induced apoptosis and AP-1 activity, while α-actinin-4 does not affect SLK autophosphorylation.","method":"Mass spectrometry identification, protein complementation assay, Co-immunoprecipitation, immunofluorescence, autophosphorylation assay, apoptosis/AP-1 reporter","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — MS identification confirmed by Co-IP, domain mapping by PCA, functional effect of Tpr on SLK activity, single lab","pmids":["26094769"],"is_preprint":false},{"year":2016,"finding":"SLK/LOSK regulates cell motility through RhoA and the dynactin subunit p150(Glued). These two downstream effectors act independently of each other. SLK is an indispensable regulator of directional cell locomotion.","method":"SLK knockdown/inhibition, RhoA and dynactin functional assays, cell migration tracking","journal":"Cytoskeleton (Hoboken, N.J.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with migration phenotype, epistasis between RhoA and dynactin pathways, single lab","pmids":["26818812"],"is_preprint":false},{"year":2016,"finding":"Increased SLK expression/activity activates the HSF1-Hsp70 pathway via polo-like kinase-1 (Plk1). This induction depends on SLK kinase activity. The resulting Hsp70 upregulation attenuates the proapoptotic effect of SLK, representing a negative feedback.","method":"HSF1/Hsp70 reporter (luciferase), Plk1 pathway inhibitors, SLK kinase-dead mutant, shRNA knockdown of HSF1, Hsp70 inhibitor","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assays with Plk1 pathway dependency and kinase-activity requirement, single lab","pmids":["27216364"],"is_preprint":false},{"year":2017,"finding":"Controlled dimerization of the SLK catalytic domain enhances autophosphorylation at T183 and S189 (activation segment). Full-length SLK is also autophosphorylated at T183 and S189. Mutations in the coiled-coil region (particularly I848G) that impair dimerization significantly reduce ezrin phosphorylation by SLK. T183A, S189A, and T193A mutations reduce both autophosphorylation and exogenous substrate (ezrin) phosphorylation.","method":"Regulated dimerization, in vitro kinase assay with ezrin as substrate, autophosphorylation site mapping, coiled-coil dimerization-impairing mutagenesis, experimental membranous nephropathy rat model","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with defined substrate and activation segment mutagenesis plus dimerization domain mutagenesis, in vivo validation in rat disease model","pmids":["28475647"],"is_preprint":false},{"year":2017,"finding":"SLK depletion in NMuMG mammary epithelial cells significantly impairs TGFβ-induced migration and invasion and reduces Snai1 mRNA and vimentin protein expression, but does not affect Smad3 nuclear translocation. Kinase-inactive SLK does not impair tight junction breakdown and rescues Snai1 mRNA levels, indicating a kinase-activity-independent role for SLK in TGFβ-induced EMT.","method":"siRNA knockdown, dominant-negative kinase expression, Smad3 nuclear translocation assay, immunofluorescence, migration/invasion assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD plus kinase-dead rescue dissects kinase-independent function, single lab","pmids":["29228724"],"is_preprint":false},{"year":2021,"finding":"Crystal structures of SLK and STK10 bound to 3-anilino-4-arylmaleimide inhibitors were solved, defining the inhibitor binding mode in the ATP-binding site and rationalizing selectivity between SLK and STK10.","method":"X-ray crystallography of inhibitor-bound SLK and STK10, kinome-wide selectivity profiling, cellular target engagement assay","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure of inhibitor-SLK complex with cellular validation, single study but X-ray is Tier 1 method","pmids":["34463505"],"is_preprint":false},{"year":2024,"finding":"Expression of a CRISPR/Cas9-generated kinase-dead allele (SLKK63R) reveals that SLK does not form homodimers and that the kinase-defective allele does not act in a dominant-negative fashion. Heterozygous SLKK63R cells show 50% reduced kinase activity, altered Rac1 and RhoA activity, increased stress fiber formation, and delayed focal adhesion turnover. Homozygous SLKK63R is embryonic lethal.","method":"CRISPR/Cas9 knock-in of kinase-dead allele, dimerization assay, kinase activity assay, Rac1/RhoA activity pull-down, focal adhesion turnover imaging","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo CRISPR knock-in with multiple orthogonal functional readouts, dimerization refuted by direct assay, defines kinase-activity requirement","pmids":["38871226"],"is_preprint":false},{"year":2025,"finding":"The RNA-binding protein HNRNPL promotes skipping of exon 13 in SLK pre-mRNA, generating the short isoform SLK-S (lacking exon 13). SLK-S activates the ERK signaling pathway and enhances HCC cell invasion/metastasis, while the long isoform SLK-L (containing exon 13) suppresses these effects through ERK pathway inhibition. In vivo targeting of the HNRNPL/SLK-S/Rac1/ERK axis inhibits HCC metastasis.","method":"Splicing reporter assays, isoform-specific overexpression/knockdown, ERK pathway Western blot, invasion/migration assays, in vivo metastasis model","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional isoform characterization with pathway readout and in vivo validation, single lab","pmids":["41046074"],"is_preprint":false},{"year":2026,"finding":"Macrophage-secreted RNAseT2 binds directly to SLK in muscle stem cells, triggering SLK-mediated phosphorylation and activation of N-WASP (via paxillin phosphorylation), which enables actin bundle formation required for myoblast/muscle stem cell fusion.","method":"Binding assay (RNAseT2-SLK interaction), phosphorylation assays for N-WASP and paxillin, actin bundle imaging, in vivo mouse and zebrafish overexpression/KO","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding demonstrated, phosphorylation cascade defined, in vivo validation in two animal models (mouse and zebrafish)","pmids":["41980967"],"is_preprint":false}],"current_model":"SLK is a Ste20-family serine/threonine kinase that is activated by homodimerization (via C-terminal coiled-coils) and autophosphorylation of activation-segment residues T183 and S189; it phosphorylates a defined set of substrates—including ERM proteins (ezrin/radixin/moesin), paxillin (S250), RhoA (S188), Plk1 (T210), ASK1, p150(Glued) dynactin, and N-WASP—to control focal adhesion turnover, actin cytoskeletal remodeling, microtubule radial organization, mitotic spindle orientation, and cell migration downstream of FAK/Src/ErbB2 signaling, and its activity is negatively regulated by CK2-mediated phosphorylation at S347/348 and by binding partners Ldb1/2 and Tpr, while caspase-3 cleavage liberates distinct N-terminal (pro-apoptotic kinase) and C-terminal (actin-disassembly) functional domains."},"narrative":{"mechanistic_narrative":"SLK is a Ste20-family serine/threonine kinase that couples upstream adhesion and growth-factor signaling to actin and microtubule remodeling, focal adhesion turnover, mitotic progression, and apoptosis [PMID:18382658, PMID:22203681]. Catalytic activation requires phosphorylation of activation-segment residues Thr183 and Ser189; mutation of these sites abolishes kinase activity, downstream JNK/p38 and AP-1 signaling, and apoptotic induction [PMID:22203681, PMID:28475647]. Through these activities SLK phosphorylates a defined substrate set to control cytoskeletal architecture: it activates ERM proteins (ezrin/radixin/moesin) to restrict apical microvilli and, at mitotic entry, to polarize LGN/NuMA at the cortex for correct spindle orientation [PMID:23209304, PMID:24958772]; it phosphorylates paxillin on Ser250 to drive focal adhesion turnover and migration downstream of FAK/c-Src [PMID:23128389, PMID:18382658]; it phosphorylates the dynactin subunit p150(Glued) to target it to the centrosome and maintain the radial microtubule array and Golgi reorientation in polarized cells [PMID:23985322, PMID:18287541]; and it phosphorylates RhoA on Ser188 downstream of the angiotensin II type 2 receptor to promote GDI-mediated cytosolic sequestration and vasodilation [PMID:18420945]. SLK additionally phosphorylates and strongly activates Plk1 on Thr210 in its activation segment, increasing Plk1 catalytic efficiency, and its activity rises during G2 in a manner required for spindle assembly and cell cycle progression [PMID:18298087, PMID:16236704]. In the apoptotic arm, caspase-3 cleaves SLK to liberate an N-terminal pro-apoptotic kinase domain and a C-terminal domain that independently disassembles actin stress fibers, and SLK activates JNK/p38 and ASK1 and promotes p53 phosphorylation to amplify ischemia-reperfusion-induced apoptosis [PMID:10611247, PMID:16316999, PMID:19640899]. SLK activity is regulated by binding partners—LMO4 and RNAseT2 activate it while Ldb1/2 and the nucleoporin Tpr restrain it—and by inhibitory CK2 phosphorylation at Ser347/348 induced by v-Src [PMID:25882817, PMID:41980967, PMID:19675209, PMID:26094769, PMID:16837460]. A CRISPR kinase-dead knock-in establishes that SLK kinase activity controls Rac1/RhoA balance, stress fiber formation, and focal adhesion turnover, and is essential for development, homozygous loss being embryonic lethal [PMID:38871226].","teleology":[{"year":1999,"claim":"Established SLK as a signaling kinase that engages the stress/apoptotic JNK pathway and localizes to the cell periphery, framing it as more than an orphan kinase.","evidence":"In vitro kinase assay, immunofluorescence, and apoptosis staining in fibroblasts","pmids":["10602516"],"confidence":"Medium","gaps":["No direct JNK substrate or intermediary identified","Overexpression-based, no endogenous loss-of-function"]},{"year":2000,"claim":"Resolved how SLK partitions its pro-apoptotic and cytoskeletal functions by showing caspase-3 cleavage liberates a kinase domain and a separate actin-disassembling C-terminal domain.","evidence":"In vitro and in vivo caspase-3 cleavage assays with domain overexpression and apoptosis readouts","pmids":["10611247"],"confidence":"High","gaps":["Mechanism by which C-terminal domain disassembles actin not defined","In vivo relevance of cleavage products untested"]},{"year":2000,"claim":"Linked SLK to cell-cycle control by showing it phosphorylates Plk1 and its activity peaks in G2.","evidence":"In vitro kinase assay and cell-cycle synchronization with activity measurement","pmids":["10886374"],"confidence":"Medium","gaps":["Phosphosite on Plk1 not yet mapped","How SLK activity is timed to G2 unknown"]},{"year":2002,"claim":"Positioned SLK on the cytoskeleton, associating with microtubules and acting through Rac1 to drive stress fiber disassembly at adhesion sites.","evidence":"Co-IP with alpha-tubulin, dominant-negative Rac1 microinjection, adenoviral overexpression","pmids":["12151406"],"confidence":"Medium","gaps":["Direct cytoskeletal substrates not identified here","Relationship between microtubule binding and kinase activity unresolved"]},{"year":2005,"claim":"Identified ASK1 as an SLK substrate selectively driving p38, and showed C-terminal homodimerization enhances kinase activity, tying activation mechanism to stress signaling.","evidence":"In vitro kinase assay, co-IP for dimerization, MAPK phosphorylation blots under chemical anoxia","pmids":["16316999"],"confidence":"Medium","gaps":["ASK1 phosphosite not defined","Selectivity for p38 over JNK/ERK mechanism unexplained"]},{"year":2005,"claim":"Demonstrated SLK is required for mitotic progression and spindle assembly, placing it upstream of H1/cdc2 kinase activation.","evidence":"Kinase-dead/siRNA knockdown with cyclin and phospho-H3 readouts, Xenopus oocyte microinjection","pmids":["16236704"],"confidence":"Medium","gaps":["Direct mitotic substrate at spindle not identified in this study","Mechanism of G2 arrest molecularly incomplete"]},{"year":2006,"claim":"Defined a negative regulatory input: v-Src induces CK2 to phosphorylate SLK at Ser347/348, suppressing its activity.","evidence":"In vitro kinase assay, deletion analysis, CK2 inhibitor, co-localization","pmids":["16837460"],"confidence":"Medium","gaps":["Structural basis for inhibition by S347/348 phosphorylation unknown","Physiological contexts of CK2 regulation beyond v-Src untested"]},{"year":2008,"claim":"Identified RhoA Ser188 as a direct SLK substrate downstream of AT2R, explaining SLK control of vascular tone via RhoA sequestration.","evidence":"In vitro kinase assay, RhoA S188 mutagenesis, signaling inhibitors in vascular smooth muscle","pmids":["18420945"],"confidence":"High","gaps":["Direct SLK activation step downstream of SHP-1/CK2 not fully reconstituted","Tissue specificity of the AT2R-SLK-RhoA axis untested"]},{"year":2008,"claim":"Quantified the SLK-Plk1 relationship, showing SLK phosphorylates Plk1 Thr210 to increase catalytic efficiency ~202-fold, defining a mitotic activation cascade.","evidence":"Reconstituted kinase assay with purified proteins and kcat/KM measurements","pmids":["18298087"],"confidence":"High","gaps":["In vivo contribution of SLK to Plk1 activation versus other activators unquantified"]},{"year":2008,"claim":"Established SLK as a centrosomal regulator that phosphorylates p150(Glued) to anchor microtubules and polarize the Golgi for directed migration.","evidence":"Dominant-negative/RNAi with dynactin/centrosome/microtubule immunofluorescence","pmids":["18287541"],"confidence":"Medium","gaps":["p150(Glued) phosphosite not mapped in this study","Microtubule nucleation versus anchoring separation incomplete"]},{"year":2008,"claim":"Connected SLK to focal adhesion turnover and migration downstream of the FAK/c-Src complex, distinguishing activation (FAK/Src/MAPK) from leading-edge recruitment (Src-dependent, FAK-independent).","evidence":"Knockdown, dominant-negative SLK, scratch-wound activity assay, inhibitor dissection","pmids":["18382658"],"confidence":"Medium","gaps":["Direct focal-adhesion substrate not yet identified here","Recruitment receptor/adaptor at leading edge unknown"]},{"year":2009,"claim":"Extended migration control to ErbB2/Neu signaling, showing SLK activation requires specific Neu phosphotyrosines and multiple downstream effectors for invasion.","evidence":"Knockdown, kinase-inactive SLK, signaling inhibitors, migration/invasion assays","pmids":["19525980"],"confidence":"Medium","gaps":["Direct link between Neu phosphosites and SLK activation step unresolved","Pathway integration with FAK/Src axis not unified"]},{"year":2009,"claim":"Implicated SLK in p53-dependent apoptosis, showing it promotes p53 Ser33/Ser315 phosphorylation and transactivation in a JNK-dependent manner during ischemia-reperfusion.","evidence":"p53 reporter, p53 site mutagenesis, JNK and p53 inhibitors, dominant-negative SLK","pmids":["19640899"],"confidence":"Medium","gaps":["Whether SLK phosphorylates p53 directly or via JNK not separated","In vivo p53 dependence beyond cell model untested"]},{"year":2009,"claim":"Identified Ldb1/2 as direct C-terminal binding partners that hold SLK inactive, defining a transcriptional-cofactor brake on the kinase during migration.","evidence":"In vitro binding, reciprocal Co-IP, co-localization, siRNA migration assays","pmids":["19675209"],"confidence":"Medium","gaps":["Mechanism of inactivation by Ldb1/2 not structurally defined","Both knockdown and overexpression increase motility, leaving dose-response unclear"]},{"year":2011,"claim":"Showed controlled homodimerization of the catalytic domain is sufficient to enhance activity and drive JNK/p38 activation, Bax expression, and apoptosis, linking dimerization to function.","evidence":"Regulated dimerization system (Fv-SLK + AP20187) with kinase, MAPK, and apoptosis readouts","pmids":["21677149"],"confidence":"Medium","gaps":["Whether endogenous full-length SLK dimerizes not addressed here","Artificial dimerizer may not reflect native activation"]},{"year":2011,"claim":"Defined the molecular basis of SLK activation: Thr183/Ser189 activation-segment phosphorylation is required for activity and is enhanced by dimerization.","evidence":"Activation-segment mutagenesis, in vitro kinase assay, MAPK/AP-1 reporters, regulated dimerization","pmids":["22203681"],"confidence":"High","gaps":["Upstream kinase versus autophosphorylation contribution to T183/S189 not fully separated"]},{"year":2012,"claim":"Identified SLK (with LOK) as the kinase activating ezrin to restrict microvilli to the apical epithelial domain, defining an ERM substrate relationship in vivo context.","evidence":"Proteomic identification, RNAi, drug-resistant kinase variants, live imaging, fractionation","pmids":["23209304"],"confidence":"High","gaps":["Mechanism of local SLK activation at microvilli not defined","Relative contribution of LOK versus SLK unresolved"]},{"year":2012,"claim":"Mapped paxillin Ser250 as a direct SLK substrate required for paxillin redistribution and migration, mechanistically linking SLK to focal adhesion dynamics.","evidence":"In vitro kinase assay, S250A mutant migration assay, phospho-FAK Y397 blots","pmids":["23128389"],"confidence":"High","gaps":["How S250 phosphorylation alters paxillin interactions not defined"]},{"year":2013,"claim":"Resolved the centrosomal mechanism by showing SLK phosphorylates p150(Glued) isoform 1A specifically to target it to the centrosome, separable from its microtubule-organizing activity.","evidence":"In vitro kinase assay, isoform-specific analysis, artificial centrosomal targeting rescue","pmids":["23985322"],"confidence":"High","gaps":["Exact p150(Glued) phosphosite not specified","How phosphorylation drives centrosomal targeting unresolved"]},{"year":2014,"claim":"Established SLK as the mitotic ERM activator that polarizes LGN/NuMA for spindle orientation, with in vivo relevance in neocortical progenitors.","evidence":"In vitro kinase assay, micropatterned spindle-orientation assay, cortical LGN/NuMA IF, in vivo mouse cortex","pmids":["24958772"],"confidence":"High","gaps":["How SLK is activated specifically at mitotic entry unresolved","Redundancy with LOK in mitosis not addressed"]},{"year":2015,"claim":"Identified LMO4 as a direct activating partner that recruits SLK to the leading edge in a Src-dependent manner, defining a positive regulatory input for migration.","evidence":"In vitro kinase assay, Co-IP after wounding, conditional LMO4 KO, SYF cell rescue, IF","pmids":["25882817"],"confidence":"Medium","gaps":["Structural basis of LMO4-mediated activation unknown","Relationship between LMO4 activation and Ldb1/2 inhibition unintegrated"]},{"year":2015,"claim":"Mapped C-terminal coiled-coil interactions with Tpr and alpha-actinin-4, showing Tpr restrains SLK autophosphorylation and apoptosis at the nuclear envelope.","evidence":"Mass spectrometry, protein complementation, Co-IP, autophosphorylation and AP-1/apoptosis assays","pmids":["26094769"],"confidence":"Medium","gaps":["Mechanism of Tpr inhibition not structurally defined","Functional role of alpha-actinin-4 interaction unclear"]},{"year":2016,"claim":"Showed SLK directs cell motility through two independent effector arms, RhoA and p150(Glued) dynactin, unifying its cytoskeletal outputs.","evidence":"Knockdown/inhibition with RhoA and dynactin functional assays and migration tracking","pmids":["26818812"],"confidence":"Medium","gaps":["How the two arms are coordinated spatially not defined","Substrate-level basis of independence not dissected"]},{"year":2016,"claim":"Revealed a survival feedback loop in which SLK activates HSF1-Hsp70 via Plk1, attenuating its own pro-apoptotic effect.","evidence":"HSF1/Hsp70 reporters, Plk1 inhibitors, kinase-dead SLK, HSF1 shRNA, Hsp70 inhibitor","pmids":["27216364"],"confidence":"Medium","gaps":["Direct versus Plk1-relayed signal to HSF1 not separated","Physiological setting of feedback untested"]},{"year":2017,"claim":"Tied activation mechanism to substrate phosphorylation by showing dimerization-impairing coiled-coil mutations reduce ERM/ezrin phosphorylation, with in vivo disease relevance in membranous nephropathy.","evidence":"Regulated dimerization, in vitro ezrin kinase assay, coiled-coil and activation-segment mutagenesis, rat nephropathy model","pmids":["28475647"],"confidence":"High","gaps":["Whether endogenous SLK dimerizes natively not settled here"]},{"year":2017,"claim":"Uncovered a kinase-activity-independent role for SLK in TGFbeta-induced EMT, where SLK supports Snai1/vimentin expression without affecting Smad3 nuclear translocation.","evidence":"siRNA knockdown, kinase-dead rescue, Smad3 translocation, migration/invasion assays","pmids":["29228724"],"confidence":"Medium","gaps":["Scaffolding mechanism for kinase-independent function unknown","How SLK regulates Snai1 transcription unresolved"]},{"year":2021,"claim":"Provided structural definition of the SLK ATP-binding site via inhibitor co-crystal structures, rationalizing selectivity versus STK10.","evidence":"X-ray crystallography of inhibitor-bound SLK and STK10, selectivity profiling, target engagement","pmids":["34463505"],"confidence":"High","gaps":["Apo/active-state and full-length structure not determined","Regulatory C-terminal domain not structurally captured"]},{"year":2024,"claim":"Directly refuted obligate homodimerization in cells and showed via a CRISPR kinase-dead knock-in that SLK activity controls Rac1/RhoA balance, stress fibers, and focal adhesion turnover, and is essential for development.","evidence":"CRISPR/Cas9 kinase-dead knock-in, dimerization assay, kinase and Rac1/RhoA pull-downs, focal adhesion imaging","pmids":["38871226"],"confidence":"High","gaps":["How native SLK is activated if not by stable dimerization unresolved","Cause of embryonic lethality molecularly undefined"]},{"year":2025,"claim":"Showed isoform-level regulation: HNRNPL-driven exon 13 skipping generates SLK-S that activates ERK and promotes HCC metastasis, opposing the suppressive long isoform SLK-L.","evidence":"Splicing reporters, isoform-specific manipulation, ERK blots, invasion assays, in vivo metastasis model","pmids":["41046074"],"confidence":"Medium","gaps":["Mechanistic basis for opposing isoform effects on ERK not defined","Whether SLK-S/SLK-L differ in kinase activity unclear"]},{"year":2026,"claim":"Defined an extracellular activation input in muscle regeneration, where macrophage-secreted RNAseT2 binds SLK to drive paxillin/N-WASP phosphorylation and actin bundling for myoblast fusion.","evidence":"RNAseT2-SLK binding assay, N-WASP/paxillin phosphorylation, actin imaging, mouse and zebrafish models","pmids":["41980967"],"confidence":"High","gaps":["Mechanism of RNAseT2-induced SLK activation not structurally defined","Receptor mediating RNAseT2 access to intracellular SLK unclear"]},{"year":null,"claim":"How SLK is activated at specific subcellular sites and cell-cycle stages in the absence of stable homodimerization, and how its positive (LMO4, RNAseT2) and negative (Ldb1/2, Tpr, CK2) regulators are integrated, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model of native activation mechanism","Spatial coordination of competing regulators undefined","Full-length/active-state structure unavailable"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[7,8,16,17,18,19,29]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[8,15,17,24]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[3,9,21]},{"term_id":"GO:0098772","term_label":"molecular function regulator 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AOMS1","url":"https://www.omim.org/entry/605552"},{"mim_id":"604095","title":"ECTODYSPLASIN A RECEPTOR; EDAR","url":"https://www.omim.org/entry/604095"},{"mim_id":"601143","title":"DYNACTIN 1; DCTN1","url":"https://www.omim.org/entry/601143"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/38871226","citation_count":1,"is_preprint":false},{"pmid":"38163671","id":"PMC_38163671","title":"Role of the Ste20-like kinase SLK in podocyte adhesion.","date":"2024","source":"Physiological reports","url":"https://pubmed.ncbi.nlm.nih.gov/38163671","citation_count":1,"is_preprint":false},{"pmid":"41256636","id":"PMC_41256636","title":"Photoproximity labeling of c-Myc reveals SLK as a cancer specific co-regulator.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41256636","citation_count":1,"is_preprint":false},{"pmid":"40544320","id":"PMC_40544320","title":"ITGA5 drives glioblastoma progression through SLK-mediated activation of the PI3K-Akt pathway.","date":"2025","source":"Neurological research","url":"https://pubmed.ncbi.nlm.nih.gov/40544320","citation_count":0,"is_preprint":false},{"pmid":"41980967","id":"PMC_41980967","title":"Restorative macrophage-derived RNAseT2 stimulates muscle stem cell fusion via an SLK/N-WASP/actin bundling dependent axis.","date":"2026","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/41980967","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.22.666149","title":"Un-LOK-ing a new approach for conformational selective targeting of STK10 (LOK)","date":"2025-07-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.22.666149","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.01.24.634716","title":"Discovery of Chirally-dependent Protein O-2-Hydroxyglutarylation by D2HG and L2HG","date":"2025-01-27","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.24.634716","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.23.604488","title":"Synthetic dysmobility screening reveals a phosphorylation-independent facet of the SLK-Ezrin-F-actin signaling cascade","date":"2024-07-24","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.23.604488","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.29.24316326","title":"Unraveling the genetic landscape of susceptibility to multiple primary cancers","date":"2024-10-30","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.29.24316326","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.11.612435","title":"Macrophage-derived RNAseT2 stimulates muscle stem cell fusion via SLK/N-WASP/actin bundling","date":"2024-09-13","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.11.612435","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.11.29.626099","title":"Dysregulated RNA splicing induces regeneration failure in alcohol-associated liver disease","date":"2024-11-30","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.29.626099","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":28891,"output_tokens":7935,"usd":0.102849,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17112,"output_tokens":8020,"usd":0.14303,"stage2_stop_reason":"end_turn"},"total_usd":0.245879,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"SLK overexpression activates c-Jun N-terminal kinase 1 (JNK1), and prolonged overexpression induces apoptosis in cultured fibroblasts. SLK colocalizes to distinct cytosolic domains, preferentially at the cell periphery.\",\n      \"method\": \"In vitro kinase assay, immunofluorescence, annexin-V/TUNEL staining\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — overexpression with functional readout and JNK1 activation, single lab but multiple assays\",\n      \"pmids\": [\"10602516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Caspase 3 cleaves SLK in vitro and in vivo during apoptosis, releasing an activated N-terminal kinase domain that promotes apoptosis and cytoskeletal rearrangements, and a C-terminal domain (AT1-46 homology domain) that independently disassembles actin stress fibers. SLK overexpression also activates the JNK signaling pathway.\",\n      \"method\": \"Caspase 3 cleavage assay in vitro and in vivo, annexin V/TUNEL, dominant-domain overexpression, immunofluorescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro and in vivo caspase cleavage demonstrated, multiple functional domain readouts, replicated with multiple apoptotic stimuli\",\n      \"pmids\": [\"10611247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"SLK can phosphorylate and activate murine Plk1. Endogenous SLK activity increases during G2 phase progression. SLK protein levels decrease in quiescent and differentiating cells. Okadaic acid treatment induces phosphorylation-dependent enhancement of SLK activity.\",\n      \"method\": \"In vitro kinase assay (SLK phosphorylating Plk1), cell cycle synchronization with kinase activity measurement\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay demonstrating SLK→Plk1 phosphorylation, single lab with cell cycle activity measurements\",\n      \"pmids\": [\"10886374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SLK associates with the microtubule network and co-precipitates with alpha-tubulin. SLK redistributes to podosome-like adhesion sites in fibronectin-stimulated fibroblasts but its kinase activity is not modulated by fibronectin. Ectopic expression of activated SLK induces actin stress fiber disassembly that is inhibited by dominant negative Rac1, and endogenous SLK colocalizes with Rac1 in spreading cells.\",\n      \"method\": \"Co-immunoprecipitation with alpha-tubulin, immunofluorescence, microinjection with dominant negative Rac1, adenoviral overexpression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — co-precipitation confirmed microtubule association, epistasis with dominant-negative Rac1 placed SLK upstream, single lab\",\n      \"pmids\": [\"12151406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"SLK phosphorylates and increases activity of apoptosis signal-regulating kinase-1 (ASK1), which in turn stimulates p38 MAPK phosphorylation (but not JNK or ERK). SLK undergoes homodimerization via its C-terminal domain, and dimerization enhances SLK kinase activity. SLK activity is stimulated by chemical anoxia/recovery (ischemia-reperfusion in cell culture).\",\n      \"method\": \"In vitro kinase assay, co-immunoprecipitation for dimerization, ASK1 phosphorylation assay, p38/JNK/ERK phosphorylation Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay showing ASK1 as substrate, dimerization confirmed by co-IP, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"16316999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"SLK co-localizes with the mitotic spindle during mitosis. Expression of kinase-inactive SLK or SLK siRNA causes G2 accumulation with failure to down-regulate cyclin A, low phospho-H3 and low active p34/cdc2. Overexpression of active SLK induces ectopic spindle assembly and triggers cell cycle re-entry in Xenopus oocytes, placing SLK upstream of H1 kinase activation.\",\n      \"method\": \"Immunofluorescence, kinase-dead mutant/siRNA knockdown, cyclin expression Western blot, Xenopus oocyte microinjection\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD and KO with cell cycle phenotype, Xenopus oocyte functional assay, single lab\",\n      \"pmids\": [\"16236704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"v-Src expression down-regulates SLK kinase activity indirectly by inducing casein kinase II (CK2) to phosphorylate SLK at serine residues 347/348. CK2 directly phosphorylates SLK at these positions, and CK2 inhibition in v-Src-transformed cells restores normal SLK activity. CK2 and SLK co-localize in fibroblasts spreading on fibronectin.\",\n      \"method\": \"In vitro kinase assay, deletion analysis, CK2 inhibitor treatment, immunofluorescence co-localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro phosphorylation of SLK by CK2 at defined sites confirmed by deletion analysis, single lab\",\n      \"pmids\": [\"16837460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SLK phosphorylates RhoA on Ser188 downstream of angiotensin II type 2 receptor (AT2R) activation, independently of cAMP/cGMP-activated kinases. The signaling cascade involves SHP-1 and casein kinase II activating SLK, which then phosphorylates RhoA to induce GDI-mediated cytosolic sequestration of RhoA and inhibition of arterial contraction/vasodilation.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis of RhoA Ser188, signaling inhibitor experiments in vascular smooth muscle cells\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay with defined substrate site, signaling cascade dissected with multiple inhibitors, functional vascular readout\",\n      \"pmids\": [\"18420945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SLK phosphorylates Plk1 on Thr210 in its activation segment, increasing Plk1 catalytic efficiency ~202-fold (k_cat increase 88-fold, K_M decrease 2.3-fold). The presence of a polo-box domain-binding phosphopeptide further amplifies the effect of Slk phosphorylation (combined 1515-fold increase in catalytic efficiency).\",\n      \"method\": \"In vitro reconstituted kinase assay with purified Plk1 and Slk, quantitative k_cat/K_M measurements using TCTP as substrate\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — quantitative in vitro reconstitution with purified proteins, kinetic parameters measured, mechanistic model validated\",\n      \"pmids\": [\"18298087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SLK (LOSK) associates with centrosomes and microtubules. Inhibition of SLK activity (dominant-negative K63R or RNAi) results in loss of dynactin from centrosomes, inability of centrosomes to anchor/cap microtubules (though nucleation is preserved), and disorganization of the microtubule radial array. Cells with suppressed SLK cannot polarize the Golgi complex at the wound edge.\",\n      \"method\": \"Dominant-negative expression, RNAi knockdown, immunofluorescence of dynactin/centrosomes/microtubules\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — DN and RNAi with clear centrosomal/microtubule phenotype, single lab\",\n      \"pmids\": [\"18287541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SLK is required for focal adhesion turnover and cell migration downstream of the FAK/c-Src complex. SLK co-localizes with paxillin, Rac1, and microtubules at the leading edge. SLK is activated by scratch wounding, dependent on FAK/c-Src/MAPK signaling, while recruitment to the leading edge is Src-dependent but FAK-independent.\",\n      \"method\": \"Knockdown, dominant-negative SLK, scratch wound kinase activity assay, co-localization immunofluorescence, signaling inhibitor dissection\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown with FA turnover phenotype, epistasis with FAK/Src inhibitors, single lab with multiple methods\",\n      \"pmids\": [\"18382658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SLK is required for ErbB2/Neu-dependent cell migration. Heregulin treatment or activated Neu overexpression stimulates SLK activity via MEK, PI3K, PLCγ, Shc, FAK, and Src signaling. Phosphorylation of Neu at Y1201 or Y1226/7 is required for SLK activation and cancer cell migration/invasion.\",\n      \"method\": \"SLK knockdown, kinase-inactive SLK overexpression, signaling pathway inhibitors, migration/invasion assays, phospho-FAK analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD/dominant-negative with functional migration assays plus signaling pathway dissection, single lab\",\n      \"pmids\": [\"19525980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SLK promotes p53 phosphorylation on Ser-33 and Ser-315, and stimulates p53 transcriptional activity. Mutation of both S33A and S315A abolishes SLK-induced p53 transactivation. SLK-induced p53 activation is attenuated by JNK inhibition. SLK overexpression amplifies ischemia-reperfusion-induced apoptosis in a p53-dependent manner.\",\n      \"method\": \"p53 reporter (luciferase), site-directed mutagenesis of p53, JNK inhibitor, dominant-negative SLK, pifithrin-alpha inhibitor\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay with mutagenesis defining required p53 phosphorylation sites, single lab\",\n      \"pmids\": [\"19640899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SLK interacts directly with the transcriptional cofactors Ldb1/CLIM2 and Ldb2/CLIM1 via its C-terminal AT1-46 homology domain, as demonstrated in vitro and in vivo. Ldb1/2 co-localize with SLK in migrating cells, and both knockdown and overexpression of Ldb1/2 increase cell motility. Ldb1/2 are proposed to maintain SLK in an inactive state.\",\n      \"method\": \"In vitro binding assay, co-immunoprecipitation, immunofluorescence co-localization, siRNA knockdown migration assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct in vitro binding confirmed, reciprocal Co-IP, functional knockdown, single lab\",\n      \"pmids\": [\"19675209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Controlled homodimerization of the SLK catalytic domain (via FK506-binding protein fusion) enhances kinase activity, activation-specific phosphorylation of JNK and p38, Bax promoter activity, and apoptosis compared to monomeric SLK.\",\n      \"method\": \"Regulated dimerization system (Fv-SLK + AP20187), in vitro kinase assay, Western blot for JNK/p38 phosphorylation, apoptosis assay\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — regulated dimerization system with in vitro kinase assay and downstream pathway readouts, single lab\",\n      \"pmids\": [\"21677149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Phosphorylation of Thr-183 and Ser-189 in the SLK activation segment is required for kinase activity and downstream signaling. T183A, S189A, and T183A/S189A mutants show reduced kinase activity, fail to activate JNK/p38 or AP-1, and do not induce apoptosis. Homodimerization enhances SLK autophosphorylation at T183/S189; the T183A/S189A double mutant is not activated by dimerization.\",\n      \"method\": \"Site-directed mutagenesis of activation segment, in vitro kinase assay, JNK/p38 phosphorylation Western blot, AP-1 reporter, regulated dimerization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — activation segment mutagenesis combined with in vitro kinase assay, downstream signaling, and regulated dimerization in same study\",\n      \"pmids\": [\"22203681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LOK and SLK are the relevant kinases that phosphorylate ezrin at the apical membrane of polarized epithelial cells, restricting microvilli to the apical domain. Both kinases are enriched in microvilli and locally activated there. Unregulated kinase activity causes ezrin mislocalization to the basolateral domain, while expression of kinase regulatory regions inhibits endogenous ezrin phosphorylation locally.\",\n      \"method\": \"Proteomic identification, RNAi knockdown, drug-resistant kinase variants, live imaging, subcellular fractionation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomic identification plus functional RNAi plus drug-resistant rescue variants, multiple orthogonal approaches, replicated\",\n      \"pmids\": [\"23209304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SLK phosphorylates paxillin on Ser-250 in vitro, and this phosphorylation is required for paxillin redistribution and cell motility. S250A paxillin mutation prevents SLK-dependent phosphorylation and results in impaired migration and accumulation of phospho-FAK-Tyr397, indicating altered focal adhesion dynamics.\",\n      \"method\": \"In vitro kinase assay with paxillin S250 as substrate, S250A mutant in migration assay, phospho-FAK Western blot, focal adhesion turnover analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay defining substrate phosphosite, mutagenesis confirming site requirement, functional migration readout\",\n      \"pmids\": [\"23128389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SLK (LOSK) phosphorylates the p150(Glued) subunit of dynactin (isoform 1A only), targeting it to the centrosome to maintain microtubule radial organization. Phosphorylation is required only for centrosomal localization of p150(Glued), not for its microtubule-organizing properties. Artificial targeting of non-phosphorylatable p150(Glued) to the centrosome rescues microtubule organization in SLK-inhibited cells. Dynactin phosphorylation is also involved in Golgi reorientation in polarized cells.\",\n      \"method\": \"In vitro kinase assay (SLK phosphorylating p150(Glued)), isoform-specific phosphorylation analysis, artificial centrosomal targeting rescue experiment, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay identifying substrate, functional rescue by artificial targeting dissecting phosphorylation from localization, mechanistic clarity\",\n      \"pmids\": [\"23985322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SLK directly and strongly activates ERM proteins (ezrin/radixin/moesin) at mitotic entry in mammalian cells. ERM activation by SLK promotes polarized association of LGN and NuMA at the mitotic cortex, which is required for correct spindle orientation. Impairing ERM activation in mouse embryonic neocortical apical progenitors severely disrupts spindle orientation in vivo.\",\n      \"method\": \"In vitro kinase assay, microfabricated adhesive substrates for spindle axis control, LGN/NuMA immunofluorescence at cortex, in vivo mouse cortex analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct in vitro kinase assay, functional spindle orientation assay on adhesive substrates, in vivo mouse cortex validation\",\n      \"pmids\": [\"24958772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"LMO4 directly binds to SLK and activates its kinase activity in vitro and in vivo. LMO4 co-precipitates with SLK after scratch wounding. Cre-mediated deletion of LMO4 inhibits cell migration, SLK activation, and recruitment of SLK and Ldb1 to the leading edge. Src/Yes/Fyn-deficient (SYF) cells with low LMO4 fail to recruit SLK to the leading edge; re-expression of wild-type LMO4 but not a mutant restores SLK localization and activity.\",\n      \"method\": \"In vitro kinase assay, Co-IP after wounding, conditional LMO4 knockout, SYF cells re-expression, immunofluorescence of leading edge localization\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay plus conditional KO with rescue, multiple methods, single lab\",\n      \"pmids\": [\"25882817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SLK interacts with nucleoporin Tpr and cytoskeletal protein α-actinin-4 via its 350 amino acid C-terminal coiled-coil domain. Subsets of SLK colocalize with Tpr at the nuclear envelope and with α-actinin-4 in the cytoplasm. Tpr expression attenuates SLK autophosphorylation and blocks SLK-induced apoptosis and AP-1 activity, while α-actinin-4 does not affect SLK autophosphorylation.\",\n      \"method\": \"Mass spectrometry identification, protein complementation assay, Co-immunoprecipitation, immunofluorescence, autophosphorylation assay, apoptosis/AP-1 reporter\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — MS identification confirmed by Co-IP, domain mapping by PCA, functional effect of Tpr on SLK activity, single lab\",\n      \"pmids\": [\"26094769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SLK/LOSK regulates cell motility through RhoA and the dynactin subunit p150(Glued). These two downstream effectors act independently of each other. SLK is an indispensable regulator of directional cell locomotion.\",\n      \"method\": \"SLK knockdown/inhibition, RhoA and dynactin functional assays, cell migration tracking\",\n      \"journal\": \"Cytoskeleton (Hoboken, N.J.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with migration phenotype, epistasis between RhoA and dynactin pathways, single lab\",\n      \"pmids\": [\"26818812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Increased SLK expression/activity activates the HSF1-Hsp70 pathway via polo-like kinase-1 (Plk1). This induction depends on SLK kinase activity. The resulting Hsp70 upregulation attenuates the proapoptotic effect of SLK, representing a negative feedback.\",\n      \"method\": \"HSF1/Hsp70 reporter (luciferase), Plk1 pathway inhibitors, SLK kinase-dead mutant, shRNA knockdown of HSF1, Hsp70 inhibitor\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assays with Plk1 pathway dependency and kinase-activity requirement, single lab\",\n      \"pmids\": [\"27216364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Controlled dimerization of the SLK catalytic domain enhances autophosphorylation at T183 and S189 (activation segment). Full-length SLK is also autophosphorylated at T183 and S189. Mutations in the coiled-coil region (particularly I848G) that impair dimerization significantly reduce ezrin phosphorylation by SLK. T183A, S189A, and T193A mutations reduce both autophosphorylation and exogenous substrate (ezrin) phosphorylation.\",\n      \"method\": \"Regulated dimerization, in vitro kinase assay with ezrin as substrate, autophosphorylation site mapping, coiled-coil dimerization-impairing mutagenesis, experimental membranous nephropathy rat model\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with defined substrate and activation segment mutagenesis plus dimerization domain mutagenesis, in vivo validation in rat disease model\",\n      \"pmids\": [\"28475647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SLK depletion in NMuMG mammary epithelial cells significantly impairs TGFβ-induced migration and invasion and reduces Snai1 mRNA and vimentin protein expression, but does not affect Smad3 nuclear translocation. Kinase-inactive SLK does not impair tight junction breakdown and rescues Snai1 mRNA levels, indicating a kinase-activity-independent role for SLK in TGFβ-induced EMT.\",\n      \"method\": \"siRNA knockdown, dominant-negative kinase expression, Smad3 nuclear translocation assay, immunofluorescence, migration/invasion assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD plus kinase-dead rescue dissects kinase-independent function, single lab\",\n      \"pmids\": [\"29228724\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structures of SLK and STK10 bound to 3-anilino-4-arylmaleimide inhibitors were solved, defining the inhibitor binding mode in the ATP-binding site and rationalizing selectivity between SLK and STK10.\",\n      \"method\": \"X-ray crystallography of inhibitor-bound SLK and STK10, kinome-wide selectivity profiling, cellular target engagement assay\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure of inhibitor-SLK complex with cellular validation, single study but X-ray is Tier 1 method\",\n      \"pmids\": [\"34463505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Expression of a CRISPR/Cas9-generated kinase-dead allele (SLKK63R) reveals that SLK does not form homodimers and that the kinase-defective allele does not act in a dominant-negative fashion. Heterozygous SLKK63R cells show 50% reduced kinase activity, altered Rac1 and RhoA activity, increased stress fiber formation, and delayed focal adhesion turnover. Homozygous SLKK63R is embryonic lethal.\",\n      \"method\": \"CRISPR/Cas9 knock-in of kinase-dead allele, dimerization assay, kinase activity assay, Rac1/RhoA activity pull-down, focal adhesion turnover imaging\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo CRISPR knock-in with multiple orthogonal functional readouts, dimerization refuted by direct assay, defines kinase-activity requirement\",\n      \"pmids\": [\"38871226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The RNA-binding protein HNRNPL promotes skipping of exon 13 in SLK pre-mRNA, generating the short isoform SLK-S (lacking exon 13). SLK-S activates the ERK signaling pathway and enhances HCC cell invasion/metastasis, while the long isoform SLK-L (containing exon 13) suppresses these effects through ERK pathway inhibition. In vivo targeting of the HNRNPL/SLK-S/Rac1/ERK axis inhibits HCC metastasis.\",\n      \"method\": \"Splicing reporter assays, isoform-specific overexpression/knockdown, ERK pathway Western blot, invasion/migration assays, in vivo metastasis model\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional isoform characterization with pathway readout and in vivo validation, single lab\",\n      \"pmids\": [\"41046074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Macrophage-secreted RNAseT2 binds directly to SLK in muscle stem cells, triggering SLK-mediated phosphorylation and activation of N-WASP (via paxillin phosphorylation), which enables actin bundle formation required for myoblast/muscle stem cell fusion.\",\n      \"method\": \"Binding assay (RNAseT2-SLK interaction), phosphorylation assays for N-WASP and paxillin, actin bundle imaging, in vivo mouse and zebrafish overexpression/KO\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding demonstrated, phosphorylation cascade defined, in vivo validation in two animal models (mouse and zebrafish)\",\n      \"pmids\": [\"41980967\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLK is a Ste20-family serine/threonine kinase that is activated by homodimerization (via C-terminal coiled-coils) and autophosphorylation of activation-segment residues T183 and S189; it phosphorylates a defined set of substrates—including ERM proteins (ezrin/radixin/moesin), paxillin (S250), RhoA (S188), Plk1 (T210), ASK1, p150(Glued) dynactin, and N-WASP—to control focal adhesion turnover, actin cytoskeletal remodeling, microtubule radial organization, mitotic spindle orientation, and cell migration downstream of FAK/Src/ErbB2 signaling, and its activity is negatively regulated by CK2-mediated phosphorylation at S347/348 and by binding partners Ldb1/2 and Tpr, while caspase-3 cleavage liberates distinct N-terminal (pro-apoptotic kinase) and C-terminal (actin-disassembly) functional domains.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SLK is a Ste20-family serine/threonine kinase that couples upstream adhesion and growth-factor signaling to actin and microtubule remodeling, focal adhesion turnover, mitotic progression, and apoptosis [#10, #15]. Catalytic activation requires phosphorylation of activation-segment residues Thr183 and Ser189; mutation of these sites abolishes kinase activity, downstream JNK/p38 and AP-1 signaling, and apoptotic induction [#15, #24]. Through these activities SLK phosphorylates a defined substrate set to control cytoskeletal architecture: it activates ERM proteins (ezrin/radixin/moesin) to restrict apical microvilli and, at mitotic entry, to polarize LGN/NuMA at the cortex for correct spindle orientation [#16, #19]; it phosphorylates paxillin on Ser250 to drive focal adhesion turnover and migration downstream of FAK/c-Src [#17, #10]; it phosphorylates the dynactin subunit p150(Glued) to target it to the centrosome and maintain the radial microtubule array and Golgi reorientation in polarized cells [#18, #9]; and it phosphorylates RhoA on Ser188 downstream of the angiotensin II type 2 receptor to promote GDI-mediated cytosolic sequestration and vasodilation [#7]. SLK additionally phosphorylates and strongly activates Plk1 on Thr210 in its activation segment, increasing Plk1 catalytic efficiency, and its activity rises during G2 in a manner required for spindle assembly and cell cycle progression [#8, #5]. In the apoptotic arm, caspase-3 cleaves SLK to liberate an N-terminal pro-apoptotic kinase domain and a C-terminal domain that independently disassembles actin stress fibers, and SLK activates JNK/p38 and ASK1 and promotes p53 phosphorylation to amplify ischemia-reperfusion-induced apoptosis [#1, #4, #12]. SLK activity is regulated by binding partners—LMO4 and RNAseT2 activate it while Ldb1/2 and the nucleoporin Tpr restrain it—and by inhibitory CK2 phosphorylation at Ser347/348 induced by v-Src [#20, #29, #13, #21, #6]. A CRISPR kinase-dead knock-in establishes that SLK kinase activity controls Rac1/RhoA balance, stress fiber formation, and focal adhesion turnover, and is essential for development, homozygous loss being embryonic lethal [#27].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established SLK as a signaling kinase that engages the stress/apoptotic JNK pathway and localizes to the cell periphery, framing it as more than an orphan kinase.\",\n      \"evidence\": \"In vitro kinase assay, immunofluorescence, and apoptosis staining in fibroblasts\",\n      \"pmids\": [\"10602516\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct JNK substrate or intermediary identified\", \"Overexpression-based, no endogenous loss-of-function\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Resolved how SLK partitions its pro-apoptotic and cytoskeletal functions by showing caspase-3 cleavage liberates a kinase domain and a separate actin-disassembling C-terminal domain.\",\n      \"evidence\": \"In vitro and in vivo caspase-3 cleavage assays with domain overexpression and apoptosis readouts\",\n      \"pmids\": [\"10611247\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which C-terminal domain disassembles actin not defined\", \"In vivo relevance of cleavage products untested\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Linked SLK to cell-cycle control by showing it phosphorylates Plk1 and its activity peaks in G2.\",\n      \"evidence\": \"In vitro kinase assay and cell-cycle synchronization with activity measurement\",\n      \"pmids\": [\"10886374\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphosite on Plk1 not yet mapped\", \"How SLK activity is timed to G2 unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Positioned SLK on the cytoskeleton, associating with microtubules and acting through Rac1 to drive stress fiber disassembly at adhesion sites.\",\n      \"evidence\": \"Co-IP with alpha-tubulin, dominant-negative Rac1 microinjection, adenoviral overexpression\",\n      \"pmids\": [\"12151406\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct cytoskeletal substrates not identified here\", \"Relationship between microtubule binding and kinase activity unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified ASK1 as an SLK substrate selectively driving p38, and showed C-terminal homodimerization enhances kinase activity, tying activation mechanism to stress signaling.\",\n      \"evidence\": \"In vitro kinase assay, co-IP for dimerization, MAPK phosphorylation blots under chemical anoxia\",\n      \"pmids\": [\"16316999\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ASK1 phosphosite not defined\", \"Selectivity for p38 over JNK/ERK mechanism unexplained\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated SLK is required for mitotic progression and spindle assembly, placing it upstream of H1/cdc2 kinase activation.\",\n      \"evidence\": \"Kinase-dead/siRNA knockdown with cyclin and phospho-H3 readouts, Xenopus oocyte microinjection\",\n      \"pmids\": [\"16236704\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mitotic substrate at spindle not identified in this study\", \"Mechanism of G2 arrest molecularly incomplete\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined a negative regulatory input: v-Src induces CK2 to phosphorylate SLK at Ser347/348, suppressing its activity.\",\n      \"evidence\": \"In vitro kinase assay, deletion analysis, CK2 inhibitor, co-localization\",\n      \"pmids\": [\"16837460\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis for inhibition by S347/348 phosphorylation unknown\", \"Physiological contexts of CK2 regulation beyond v-Src untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified RhoA Ser188 as a direct SLK substrate downstream of AT2R, explaining SLK control of vascular tone via RhoA sequestration.\",\n      \"evidence\": \"In vitro kinase assay, RhoA S188 mutagenesis, signaling inhibitors in vascular smooth muscle\",\n      \"pmids\": [\"18420945\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct SLK activation step downstream of SHP-1/CK2 not fully reconstituted\", \"Tissue specificity of the AT2R-SLK-RhoA axis untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Quantified the SLK-Plk1 relationship, showing SLK phosphorylates Plk1 Thr210 to increase catalytic efficiency ~202-fold, defining a mitotic activation cascade.\",\n      \"evidence\": \"Reconstituted kinase assay with purified proteins and kcat/KM measurements\",\n      \"pmids\": [\"18298087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo contribution of SLK to Plk1 activation versus other activators unquantified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Established SLK as a centrosomal regulator that phosphorylates p150(Glued) to anchor microtubules and polarize the Golgi for directed migration.\",\n      \"evidence\": \"Dominant-negative/RNAi with dynactin/centrosome/microtubule immunofluorescence\",\n      \"pmids\": [\"18287541\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"p150(Glued) phosphosite not mapped in this study\", \"Microtubule nucleation versus anchoring separation incomplete\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected SLK to focal adhesion turnover and migration downstream of the FAK/c-Src complex, distinguishing activation (FAK/Src/MAPK) from leading-edge recruitment (Src-dependent, FAK-independent).\",\n      \"evidence\": \"Knockdown, dominant-negative SLK, scratch-wound activity assay, inhibitor dissection\",\n      \"pmids\": [\"18382658\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct focal-adhesion substrate not yet identified here\", \"Recruitment receptor/adaptor at leading edge unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended migration control to ErbB2/Neu signaling, showing SLK activation requires specific Neu phosphotyrosines and multiple downstream effectors for invasion.\",\n      \"evidence\": \"Knockdown, kinase-inactive SLK, signaling inhibitors, migration/invasion assays\",\n      \"pmids\": [\"19525980\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct link between Neu phosphosites and SLK activation step unresolved\", \"Pathway integration with FAK/Src axis not unified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Implicated SLK in p53-dependent apoptosis, showing it promotes p53 Ser33/Ser315 phosphorylation and transactivation in a JNK-dependent manner during ischemia-reperfusion.\",\n      \"evidence\": \"p53 reporter, p53 site mutagenesis, JNK and p53 inhibitors, dominant-negative SLK\",\n      \"pmids\": [\"19640899\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SLK phosphorylates p53 directly or via JNK not separated\", \"In vivo p53 dependence beyond cell model untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified Ldb1/2 as direct C-terminal binding partners that hold SLK inactive, defining a transcriptional-cofactor brake on the kinase during migration.\",\n      \"evidence\": \"In vitro binding, reciprocal Co-IP, co-localization, siRNA migration assays\",\n      \"pmids\": [\"19675209\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of inactivation by Ldb1/2 not structurally defined\", \"Both knockdown and overexpression increase motility, leaving dose-response unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed controlled homodimerization of the catalytic domain is sufficient to enhance activity and drive JNK/p38 activation, Bax expression, and apoptosis, linking dimerization to function.\",\n      \"evidence\": \"Regulated dimerization system (Fv-SLK + AP20187) with kinase, MAPK, and apoptosis readouts\",\n      \"pmids\": [\"21677149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether endogenous full-length SLK dimerizes not addressed here\", \"Artificial dimerizer may not reflect native activation\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined the molecular basis of SLK activation: Thr183/Ser189 activation-segment phosphorylation is required for activity and is enhanced by dimerization.\",\n      \"evidence\": \"Activation-segment mutagenesis, in vitro kinase assay, MAPK/AP-1 reporters, regulated dimerization\",\n      \"pmids\": [\"22203681\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream kinase versus autophosphorylation contribution to T183/S189 not fully separated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified SLK (with LOK) as the kinase activating ezrin to restrict microvilli to the apical epithelial domain, defining an ERM substrate relationship in vivo context.\",\n      \"evidence\": \"Proteomic identification, RNAi, drug-resistant kinase variants, live imaging, fractionation\",\n      \"pmids\": [\"23209304\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of local SLK activation at microvilli not defined\", \"Relative contribution of LOK versus SLK unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Mapped paxillin Ser250 as a direct SLK substrate required for paxillin redistribution and migration, mechanistically linking SLK to focal adhesion dynamics.\",\n      \"evidence\": \"In vitro kinase assay, S250A mutant migration assay, phospho-FAK Y397 blots\",\n      \"pmids\": [\"23128389\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How S250 phosphorylation alters paxillin interactions not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the centrosomal mechanism by showing SLK phosphorylates p150(Glued) isoform 1A specifically to target it to the centrosome, separable from its microtubule-organizing activity.\",\n      \"evidence\": \"In vitro kinase assay, isoform-specific analysis, artificial centrosomal targeting rescue\",\n      \"pmids\": [\"23985322\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact p150(Glued) phosphosite not specified\", \"How phosphorylation drives centrosomal targeting unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established SLK as the mitotic ERM activator that polarizes LGN/NuMA for spindle orientation, with in vivo relevance in neocortical progenitors.\",\n      \"evidence\": \"In vitro kinase assay, micropatterned spindle-orientation assay, cortical LGN/NuMA IF, in vivo mouse cortex\",\n      \"pmids\": [\"24958772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SLK is activated specifically at mitotic entry unresolved\", \"Redundancy with LOK in mitosis not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified LMO4 as a direct activating partner that recruits SLK to the leading edge in a Src-dependent manner, defining a positive regulatory input for migration.\",\n      \"evidence\": \"In vitro kinase assay, Co-IP after wounding, conditional LMO4 KO, SYF cell rescue, IF\",\n      \"pmids\": [\"25882817\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of LMO4-mediated activation unknown\", \"Relationship between LMO4 activation and Ldb1/2 inhibition unintegrated\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Mapped C-terminal coiled-coil interactions with Tpr and alpha-actinin-4, showing Tpr restrains SLK autophosphorylation and apoptosis at the nuclear envelope.\",\n      \"evidence\": \"Mass spectrometry, protein complementation, Co-IP, autophosphorylation and AP-1/apoptosis assays\",\n      \"pmids\": [\"26094769\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of Tpr inhibition not structurally defined\", \"Functional role of alpha-actinin-4 interaction unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed SLK directs cell motility through two independent effector arms, RhoA and p150(Glued) dynactin, unifying its cytoskeletal outputs.\",\n      \"evidence\": \"Knockdown/inhibition with RhoA and dynactin functional assays and migration tracking\",\n      \"pmids\": [\"26818812\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How the two arms are coordinated spatially not defined\", \"Substrate-level basis of independence not dissected\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed a survival feedback loop in which SLK activates HSF1-Hsp70 via Plk1, attenuating its own pro-apoptotic effect.\",\n      \"evidence\": \"HSF1/Hsp70 reporters, Plk1 inhibitors, kinase-dead SLK, HSF1 shRNA, Hsp70 inhibitor\",\n      \"pmids\": [\"27216364\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus Plk1-relayed signal to HSF1 not separated\", \"Physiological setting of feedback untested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Tied activation mechanism to substrate phosphorylation by showing dimerization-impairing coiled-coil mutations reduce ERM/ezrin phosphorylation, with in vivo disease relevance in membranous nephropathy.\",\n      \"evidence\": \"Regulated dimerization, in vitro ezrin kinase assay, coiled-coil and activation-segment mutagenesis, rat nephropathy model\",\n      \"pmids\": [\"28475647\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether endogenous SLK dimerizes natively not settled here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Uncovered a kinase-activity-independent role for SLK in TGFbeta-induced EMT, where SLK supports Snai1/vimentin expression without affecting Smad3 nuclear translocation.\",\n      \"evidence\": \"siRNA knockdown, kinase-dead rescue, Smad3 translocation, migration/invasion assays\",\n      \"pmids\": [\"29228724\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Scaffolding mechanism for kinase-independent function unknown\", \"How SLK regulates Snai1 transcription unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided structural definition of the SLK ATP-binding site via inhibitor co-crystal structures, rationalizing selectivity versus STK10.\",\n      \"evidence\": \"X-ray crystallography of inhibitor-bound SLK and STK10, selectivity profiling, target engagement\",\n      \"pmids\": [\"34463505\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Apo/active-state and full-length structure not determined\", \"Regulatory C-terminal domain not structurally captured\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Directly refuted obligate homodimerization in cells and showed via a CRISPR kinase-dead knock-in that SLK activity controls Rac1/RhoA balance, stress fibers, and focal adhesion turnover, and is essential for development.\",\n      \"evidence\": \"CRISPR/Cas9 kinase-dead knock-in, dimerization assay, kinase and Rac1/RhoA pull-downs, focal adhesion imaging\",\n      \"pmids\": [\"38871226\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How native SLK is activated if not by stable dimerization unresolved\", \"Cause of embryonic lethality molecularly undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed isoform-level regulation: HNRNPL-driven exon 13 skipping generates SLK-S that activates ERK and promotes HCC metastasis, opposing the suppressive long isoform SLK-L.\",\n      \"evidence\": \"Splicing reporters, isoform-specific manipulation, ERK blots, invasion assays, in vivo metastasis model\",\n      \"pmids\": [\"41046074\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic basis for opposing isoform effects on ERK not defined\", \"Whether SLK-S/SLK-L differ in kinase activity unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defined an extracellular activation input in muscle regeneration, where macrophage-secreted RNAseT2 binds SLK to drive paxillin/N-WASP phosphorylation and actin bundling for myoblast fusion.\",\n      \"evidence\": \"RNAseT2-SLK binding assay, N-WASP/paxillin phosphorylation, actin imaging, mouse and zebrafish models\",\n      \"pmids\": [\"41980967\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of RNAseT2-induced SLK activation not structurally defined\", \"Receptor mediating RNAseT2 access to intracellular SLK unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SLK is activated at specific subcellular sites and cell-cycle stages in the absence of stable homodimerization, and how its positive (LMO4, RNAseT2) and negative (Ldb1/2, Tpr, CK2) regulators are integrated, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model of native activation mechanism\", \"Spatial coordination of competing regulators undefined\", \"Full-length/active-state structure unavailable\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [7, 8, 16, 17, 18, 19, 29]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [8, 15, 17, 24]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [3, 9, 21]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [3, 9, 18]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [9, 18]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [10, 16]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [21]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 10, 11, 28]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [5, 8, 19]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [1, 12, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [19, 27, 29]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PLK1\", \"RHOA\", \"PXN\", \"DCTN1\", \"EZR\", \"LMO4\", \"TPR\", \"LDB1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}