{"gene":"LCK","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":1997,"finding":"S-acylation (palmitoylation) of LCK at Cys3 and Cys5 at the N-terminus is required for plasma membrane targeting and TCR signaling; a non-S-acylated LCK mutant is catalytically active but cannot reach the plasma membrane and fails to phosphorylate CD8-zeta or reconstitute TCR signaling in LCK-negative T cells.","method":"Transient transfection of COS-18 cells and LCK-negative JCam-1.6 T cells with LCK acylation mutants; functional assays including Ca2+ flux, CD69/NFAT induction, ZAP-70 association","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal functional assays with site-specific mutants, reconstitution in LCK-negative cells","pmids":["9305640"],"is_preprint":false},{"year":2003,"finding":"LCK associates with CD4 and CD8 coreceptor cytoplasmic tails via a zinc-coordinated 'zinc clasp' heterodimeric domain; both coreceptor tails and the LCK N-terminus are unstructured in isolation but fold together in the presence of Zn2+.","method":"Solution NMR structure determination of ternary CD4-Lck-Zn2+ and CD8alpha-Lck-Zn2+ complexes","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with functional validation, defines molecular basis of zinc-dependent co-receptor association","pmids":["14500983"],"is_preprint":false},{"year":1995,"finding":"Phosphorylation of Tyr394 (the activating autophosphorylation site) is required for H2O2-induced activation of LCK; additionally, a kinase other than LCK itself can phosphorylate Tyr394, suggesting a trans-activating kinase exists.","method":"In vivo H2O2 treatment of cells expressing Lck mutants (Y394F, kinase-inactive); kinase activity assays; expression in LCK-negative cells","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro and in vivo mutational analysis with kinase activity readouts, single lab but multiple orthogonal approaches","pmids":["7538674"],"is_preprint":false},{"year":1994,"finding":"LCK can autophosphorylate at both Tyr394 (activating) and Tyr505 (inhibitory) in vitro; autophosphorylation at Tyr505 may represent an accessory mechanism for self-downregulation of kinase activity.","method":"Recombinant GST-Lck expression in E. coli with phosphosite mutants (Y394F, Y505F, K273E, double mutant); in vivo and in vitro autophosphorylation assays; phosphopeptide mapping","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution in bacteria with mutagenesis and phosphopeptide mapping, multiple mutants tested","pmids":["7523116"],"is_preprint":false},{"year":2002,"finding":"CD4 recruits LCK to the T cell–APC interface (immunological synapse), while CD28 sustains LCK autophosphorylation; TCR cross-linking alone is insufficient to stimulate LCK autophosphorylation.","method":"Phosphospecific antisera to activated LCK; stimulation of T cells with antigen-presenting cells; blocking antibodies to CD4 and CD28","journal":"Nature immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphospecific antibody readout with functional co-stimulation dissection, single lab, two orthogonal methods","pmids":["11828322"],"is_preprint":false},{"year":2002,"finding":"Cbl ubiquitin ligase negatively regulates LCK by ubiquitinating it upon TCR/CD4 co-ligation, leading to LCK degradation; LCK kinase activity and Cbl RING finger (E3 ligase) activity are both required for LCK ubiquitination; the LCK SH3 domain mediates Cbl-LCK association.","method":"Co-immunoprecipitation; Cbl-/- T cell line analysis; co-expression in 293T cells; reporter assays; SH3 domain mutants","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic loss-of-function cell line, mutagenesis, functional reporter assays","pmids":["11904433"],"is_preprint":false},{"year":1999,"finding":"CD45 dephosphorylation of the inhibitory Tyr505 of LCK is required for thymocyte development; expression of the constitutively active Y505F LCK mutant rescues thymocyte development in CD45-deficient mice.","method":"Genetic epistasis: CD45-/- mice crossed with LckY505F transgenic mice and DO11.10 TCR transgenic mice; T cell functional assays (CD69, IL-2, proliferation)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in vivo with defined molecular mechanism, replicated functionally in multiple assays","pmids":["10330160"],"is_preprint":false},{"year":2002,"finding":"PKCepsilon forms a signaling module with LCK in cardiac cells: PKCepsilon interacts with, phosphorylates, and activates LCK; disruption of PKCepsilon-LCK modules by Lck gene ablation abrogates cardioprotection from ischemic preconditioning.","method":"Functional proteomics; co-immunoprecipitation; transgenic cardiac-specific PKCepsilon activation; Lck knockout mice; infarct size measurement","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, in vivo genetic knockout with defined phenotype, single lab","pmids":["11854322"],"is_preprint":false},{"year":2010,"finding":"Constitutively active LCK is present in unstimulated naive T cells and thymocytes (~40% of total LCK); the amount of active LCK does not change after TCR/coreceptor engagement but determines the extent of TCR-zeta phosphorylation; maintenance of active LCK requires the HSP90-CDC37 chaperone complex.","method":"Phosphospecific antibodies; flow cytometry; biochemical fractionation; HSP90 inhibitor treatment; quantification in primary cells","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods, primary cells, functional quantitative readout, demonstrated HSP90 dependence","pmids":["20541955"],"is_preprint":false},{"year":2018,"finding":"LCK acts as a molecular bridge facilitating ZAP70-dependent LAT phosphorylation: LCK SH2 domain binds phospho-ZAP70, while its SH3 domain binds a conserved proline-rich motif in LAT, co-localizing ZAP70 and LAT; elimination of the LAT proline-rich motif compromises TCR signaling and T cell development.","method":"Co-immunoprecipitation; phosphoproteomic mass spectrometry; LAT mutants; retrogenic mice; T cell signaling assays","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, mutagenesis, in vivo mouse model, MS phosphoproteomics","pmids":["29915297"],"is_preprint":false},{"year":2014,"finding":"The phosphatase JKAP/DUSP22 directly inactivates LCK by dephosphorylating Tyr394; JKAP-knockout T cells display enhanced proliferation and cytokine production; JKAP-deficient mice are more susceptible to EAE.","method":"In vitro phosphatase assay; JKAP knockout mice; T cell proliferation and cytokine assays; EAE model; adoptive transfer","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro enzyme-substrate assay, genetic knockout with defined molecular and in vivo phenotypes","pmids":["24714587"],"is_preprint":false},{"year":2021,"finding":"Asparagine directly binds to LCK and modulates its phosphorylation at Tyr394 and Tyr505, thereby enhancing LCK kinase activity and TCR signaling in CD8+ T cells, independently of metabolic flux changes.","method":"Binding assays; phospho-specific immunoblotting; Asn restriction experiments; SLC1A5 inhibition; in vitro and in vivo T cell activation assays","journal":"Nature cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated, phosphosite regulation shown, single lab, metabolic independence confirmed","pmids":["33420490"],"is_preprint":false},{"year":2012,"finding":"LCK conformational state controls its nanoscale clustering: open/active conformation induces LCK clustering; closed/inactive conformation prevents clustering; conformation-driven clusters contain phosphorylated TCRs but exclude the phosphatase CD45.","method":"Super-resolution microscopy (PALM/STORM); LCK conformation-state mutants; single-molecule imaging in T cells","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — super-resolution imaging with conformation-specific mutants, direct spatial and functional consequence demonstrated","pmids":["23202272"],"is_preprint":false},{"year":2020,"finding":"A previously unknown RK motif in the CD3ε cytoplasmic tail binds to the LCK SH3 domain in a noncanonical manner; this motif is accessible only upon TCR ligation, allowing ligand-induced LCK recruitment; binding augments local LCK activity, CD3 phosphorylation, and T cell activation.","method":"Biochemical binding assays; mutagenesis; cell-based T cell activation assays; thymocyte development assays; CAR-T cell in vitro and in vivo efficacy","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding characterization with mutagenesis, in vivo thymocyte development, multiple functional readouts","pmids":["32690949"],"is_preprint":false},{"year":2017,"finding":"The ionic interaction between the basic residue-rich sequence (BRS) of CD3ε and acidic residues in the Unique domain of LCK selectively targets LCK to CD3ε and controls TCR phosphorylation initiation upon antigen stimulation; CD3ε BRS is membrane-sequestered at rest and unlocked by antigen stimulation.","method":"TCR reconstitution system; electrostatic interaction mapping; mutagenesis; phosphorylation assays","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic reconstitution, mutagenesis, defined ionic interaction domain, multiple orthogonal approaches","pmids":["28659468"],"is_preprint":false},{"year":2022,"finding":"LAG3 causes dissociation of LCK from the CD4 or CD8 co-receptor via its acidic tandem glutamic acid-proline repeat in the cytoplasmic tail lowering local pH at the immune synapse, resulting in loss of co-receptor-TCR signaling.","method":"Co-immunoprecipitation; pH sensor imaging; LAG3 cytoplasmic domain mutants; T cell activation assays; CD4/CD8-LCK dissociation measurement","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic dissection with domain mutants, co-IP, live-cell imaging, functional T cell readouts","pmids":["35437325"],"is_preprint":false},{"year":1999,"finding":"SHP-1 co-immunoprecipitates with the p85 regulatory subunit of PI3K in T cells; this interaction is increased by TCR ligation and requires Lck-mediated phosphorylation of SHP-1 at Tyr564; SHP-1 then dephosphorylates p85 and reduces PI3K activity and Akt phosphorylation.","method":"Co-immunoprecipitation; constitutively active Lck co-expression; SHP-1 truncation mutants; PI3K enzyme activity assay; pAkt immunoblotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with truncation mutants, enzyme activity assay, single lab","pmids":["10488096"],"is_preprint":false},{"year":2000,"finding":"Lck tyrosine phosphorylates PKCtheta at Tyr90 in its regulatory domain, both in vitro and in intact T cells; this phosphorylation is required for PKCtheta-dependent enhancement of T cell proliferation and NFAT activation; Lck associates with the regulatory domain of PKCtheta constitutively, enhanced by T cell activation, via both SH2 and SH3 domains.","method":"In vitro kinase assay; co-immunoprecipitation; site-directed mutagenesis (Y90F); T cell reporter assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus mutagenesis and cell-based functional assays, single lab","pmids":["10652356"],"is_preprint":false},{"year":2015,"finding":"Fas receptor engagement leads to a rapid and transient increase in LCK palmitoylation; this dynamic palmitoylation is required for downstream Fas signaling (ZAP70, PLC-γ1 activation) and Fas-mediated apoptosis; DHHC21 is the palmitoyl acyl transferase responsible.","method":"Palmitoylation assay; DHHC21 knockdown; inhibition of palmitoylation; apoptosis assay; downstream signaling readouts","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — palmitoylation biochemistry, DHHC21 knockdown, functional apoptosis readout, single lab","pmids":["26351666"],"is_preprint":false},{"year":2011,"finding":"DHHC2, a DHHC family protein S-acyltransferase localized to the ER and Golgi, palmitoylates LCK in T cells; DHHC2 knockdown reduces LCK S-acylation and partially delocalizes LCK from membranes.","method":"siRNA knockdown of DHHC2; S-acylation assay; subcellular fractionation; LckN10-GFP overexpression reporter","journal":"Molecular membrane biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA loss-of-function, acylation biochemistry, localization assay, single lab","pmids":["22034844"],"is_preprint":false},{"year":2004,"finding":"Activated LCK conformations (open/active) are targeted for ubiquitination and degradation, while HSP90 binding rescues active LCK from degradation; both processes are triggered by conformational changes (open SH2/SH3), not by kinase activity or phosphorylation at S42/S59 or Y394; the Src inhibitor PP2 (binding ATP site) reduces ubiquitination and Hsp90 dependence.","method":"Lck conformational and kinase mutants expressed in COS-7 cells; Hsp90 inhibitor geldanamycin; ubiquitination assays; western blotting in T cells","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of multiple sites, pharmacological probes, single lab","pmids":["15199125"],"is_preprint":false},{"year":2017,"finding":"A phosphosite at Y192 within the LCK SH2 domain inhibits CD45 association with LCK in cells, preventing CD45-mediated dephosphorylation of the C-terminal inhibitory tail (Y505), thus blocking LCK adoption of the active open conformation; Y192 mutation blocks proximal TCR signaling and thymocyte development.","method":"Y192 mutant LCK; co-immunoprecipitation; phosphospecific immunoblotting; retrogenic mice; thymocyte development assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mutagenesis, Co-IP, in vivo thymocyte model, multiple orthogonal signaling readouts","pmids":["28735895"],"is_preprint":false},{"year":1996,"finding":"Cdc2 kinase associates with LCK through the LCK SH3 domain (only active Cdc2 associates) and phosphorylates LCK in vitro at mitosis, shifting its electrophoretic mobility; this association is selective and not shared by Csk or Syk.","method":"Co-immunoprecipitation with anti-Lck and anti-Cdc2 antibodies; Suc1-agarose affinity; in vitro kinase assay; mitotic cell arrest","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus Co-IP, single lab","pmids":["8910336"],"is_preprint":false},{"year":2000,"finding":"Quantitative differences in LCK signal (activity level) control the CD4/CD8 lineage decision in thymocytes: reduced LCK activity causes class II-restricted thymocytes to develop into CD8 T cells; increased LCK activity causes class I-restricted thymocytes to develop into CD4 T cells.","method":"Transgenic mice with altered Lck activity (dominant-negative or constitutively active); TCR transgenic backgrounds; thymocyte lineage analysis","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in vivo with quantitative activity manipulation, replicated with two reciprocal transgenic models","pmids":["10755618"],"is_preprint":false},{"year":2013,"finding":"LCK mediates Th2 differentiation through regulation of T-bet and GATA-3 expression; in lck-/- Th2 cells, GATA-3 is reduced and T-bet is aberrantly elevated, leading to IFN-gamma production; overexpression of GATA-3 restores IL-4 expression in lck-/- Th2 cells.","method":"Lck knockout mouse model; Th1/Th2 skewing; cytokine assays; transcription factor expression analysis; GATA-3 overexpression rescue","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with defined transcription factor mechanism, rescue experiment, single lab","pmids":["20237292"],"is_preprint":false},{"year":1999,"finding":"Lck directly activates STAT3 by tyrosine phosphorylation, enhancing STAT3 DNA binding activity; this was demonstrated in a baculovirus reconstitution system and in mammalian cells expressing constitutively active Lck.","method":"Baculovirus co-expression of Lck and STAT3; exogenous Lck addition to STAT3; Lck-specific inhibitor PP1; constitutively active Lck stable cell lines; EMSA","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with inhibitor validation and cell-based confirmation, single lab","pmids":["10617281"],"is_preprint":false},{"year":2013,"finding":"LCK mediates β1-integrin signaling in Schwann cells downstream of laminin: LCK activation by laminin/β1-integrin drives a paxillin/CrkII/Rac-GTP pathway to induce lamellipodia; LCK-/- mice show delays in myelination, thinner myelin with abnormal g-ratios, and aberrant myelin outfoldings.","method":"LCK inhibitor in Schwann cells; siRNA knockdown of β1-integrin; Lck-/- mice; myelination assays; Rac-GTP pull-down","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout in vivo, pharmacological inhibition, siRNA, defined pathway readouts in multiple systems","pmids":["23715271"],"is_preprint":false},{"year":1998,"finding":"Tyrosine-phosphorylated paxillin associates with LCK via the LCK SH2 domain in T cells following CD45 or CD3 stimulation; paxillin phosphorylation is dependent on LCK expression.","method":"Co-immunoprecipitation; GST-SH2 domain pull-down; LCK-deficient T cell reconstitution; western blotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST pull-down and Co-IP with LCK-deficient cell validation, single lab","pmids":["9488700"],"is_preprint":false},{"year":2006,"finding":"Glucocorticoid receptor is part of a TCR-linked multiprotein complex containing HSP90, LCK, and FYN; short-term glucocorticoid treatment causes dissociation of this complex, resulting in impaired LCK/FYN activation and TCR signaling; HSP90 is required for complex assembly.","method":"Co-immunoprecipitation; GC receptor siRNA; HSP90 siRNA; LCK/FYN activity assays; T cell stimulation","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with siRNA knockdown validation, single lab","pmids":["16888650"],"is_preprint":false},{"year":2017,"finding":"Autophosphorylation of the LCK activation-loop (Y394) is indispensable for catalytic activity; LCK can stimulate its own activation by adopting a more open conformation; CD4 and CD8 coreceptors enhance LCK kinase activity.","method":"Genetic code expansion (photocaged lysine replacing active-site K) to generate LCK*; FRET biosensor imaging; biochemical phosphorylation kinetics in live cells; CD4/CD8 cotransfection","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — novel optogenetic/genetic code expansion tool with quantitative live-cell imaging, mutagenesis, and biochemical validation","pmids":["29083415"],"is_preprint":false},{"year":2014,"finding":"LCK phosphorylates FOXP3 at Tyr342, stabilizing FOXP3 expression; phospho-FOXP3 then suppresses LCK-induced MMP9, SKP2, and VEGF-A expression; the Y342F FOXP3 mutant abolishes suppression of MMP9 and cell invasion.","method":"Co-immunoprecipitation; in vitro kinase assay; site-directed mutagenesis (Y342F); invasion assays; western blotting","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay plus mutagenesis and functional invasion assay, single lab","pmids":["24155921"],"is_preprint":false},{"year":2008,"finding":"LCK-dependent activation of FYN requires LCK to be kinase-active and partition to lipid rafts, mediated by the C-terminal YQPQP sequence; only LR-associated kinase-active LCK co-immunoprecipitates with and activates FYN.","method":"Lipid raft fractionation; Co-immunoprecipitation; Lck C-terminal truncation and kinase mutants in NIH 3T3 and T cells; FYN kinase activity assay; IL-2 reporter","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, lipid raft fractionation, mutagenesis with functional readout, single lab","pmids":["18660530"],"is_preprint":false},{"year":2016,"finding":"The Lck SH2 domain binds anionic plasma membrane lipids (including PI(4,5)P2 and PI(3,4,5)P3) through a surface-exposed basic/aromatic/hydrophobic site distinct from the phospho-Tyr binding pocket; mutation of lipid-binding residues greatly reduces LCK interaction with TCR zeta chain and overall TCR signaling activity.","method":"NMR analysis; electrostatic potential calculation; mutational studies; membrane binding assays; TCR signaling assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR with mutagenesis and functional TCR signaling validation, single lab","pmids":["27334919"],"is_preprint":false},{"year":1996,"finding":"The LCK SH3 domain enables LCK to dimerize (interact with itself via SH2/SH3 domains); kinase-dead CD4-Lck lacking catalytic domain can enhance tyrosine phosphorylation by recruiting endogenous active Lck via SH2/SH3 interactions; this dimerization requires endogenous LCK.","method":"CD4-Lck chimeras in Lck-positive and Lck-negative (JCam1.6) T cells; GST-SH2/SH3 pull-down from T cell lysates; tyrosine phosphorylation assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain deletion chimeras, GST pull-down, Lck-negative reconstitution, single lab","pmids":["8798782"],"is_preprint":false},{"year":2017,"finding":"Rab11-FIP3 controls Lck subcellular localization and delivery to the immunological synapse; FIP3 overexpression or silencing modifies Lck endosomal localization and alters TCR-proximal signaling (zeta, ZAP70, LAT phosphorylation, Ca2+ flux, IL-2 expression), as well as steady-state TCR-CD3 surface expression.","method":"FIP3 overexpression and siRNA silencing in human T cells; confocal microscopy; signaling assays (phosphotyrosine, Ca2+ flux); IL-2 reporter; flow cytometry","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with imaging and signaling readouts, single lab","pmids":["28235866"],"is_preprint":false},{"year":2014,"finding":"SAP facilitates recruitment and activation of LCK (but not FYN) at NTB-A receptors during TCR restimulation; NTB-A-associated LCK activity is enhanced in SAP-dependent manner, amplifying proximal TCR signaling and restimulation-induced cell death (RICD); both NTB-A ITSM motifs are required.","method":"Co-immunoprecipitation; NTB-A ITSM mutants; SAP siRNA; LCK kinase activity assay; RICD assay in XLP patient T cells","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mutants, patient-derived cells, SAP siRNA, functional RICD readout, single lab","pmids":["24688028"],"is_preprint":false},{"year":2022,"finding":"CD146 directly interacts with the SH3 domain of coreceptor-free LCK via its cytoplasmic domain; CD146 dimerization upon TCR ligation recruits LCK and promotes LCK autophosphorylation; CD146 deficiency impairs thymocyte development and peripheral T cell activation.","method":"Co-immunoprecipitation; direct binding assays; CD146 knockout mice; thymocyte development analysis; LCK autophosphorylation assay","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay, Co-IP, genetic knockout in vivo, single lab","pmids":["34491908"],"is_preprint":false},{"year":2024,"finding":"UBR2 E3 ubiquitin ligase induces Lys63-linked ubiquitination of LCK at Lys99 and Lys276, followed by Tyr394 phosphorylation and activation during TCR signaling; DUSP22 dephosphorylates UBR2, leading to its degradation and thus indirectly limiting LCK activation; UBR2-mediated K63-ubiquitination of LCK is elevated in SLE patient T cells.","method":"Single-cell RNA sequencing; co-immunoprecipitation; ubiquitination assays (K63 linkage); UBR2 knockout; DUSP22 phosphatase assays; LCK kinase activity; SLE patient samples","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, K63 ubiquitination biochemistry, genetic KO, patient samples), single lab","pmids":["38225265"],"is_preprint":false},{"year":2013,"finding":"FAK negatively regulates LCK activity in T cells by recruiting C-terminal Src kinase (Csk) to the membrane/receptor complex after TCR activation; in the absence of FAK, inhibitory phosphorylation of LCK (and/or Fyn) is impaired, resulting in augmented TCR signaling.","method":"FAK inhibition/suppression in primary human T cells; Csk recruitment assay; LCK phosphorylation analysis; TCR signaling assays","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function, defined molecular pathway (FAK→Csk→LCK), single lab","pmids":["24227778"],"is_preprint":false},{"year":2018,"finding":"Lck transmembrane domain of ICOS promotes LCK association with ICOS; this TMD-enabled LCK association is required for both PI3K-p85 recruitment to ICOS and calcium mobilization costimulation; ICOS cytoplasmic domain is dispensable for calcium costimulation.","method":"ICOS TMD swap mutants; co-immunoprecipitation; PI3K recruitment assay; calcium flux; in vivo TFH/GC formation","journal":"Cellular & molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain-swap mutants, Co-IP, in vivo mouse model, single lab","pmids":["30523347"],"is_preprint":false},{"year":2016,"finding":"LCK interacts with WASH and induces WASH phosphorylation at Y141; this Lck-mediated phosphorylation is required for lytic granule polarization and NK cell cytotoxicity.","method":"Co-immunoprecipitation; WASH Y141F mutant; WASH knockdown; lytic granule polarization assay; cytotoxicity assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, phosphosite mutagenesis, functional cytotoxicity assay, single lab","pmids":["27441653"],"is_preprint":false},{"year":2022,"finding":"Disulfiram (DSF) covalently binds to Cys20/Cys23 residues of LCK and enhances LCK Tyr394 phosphorylation, promoting LCK kinase activity and effector T cell function; this mechanism enhances anti-tumor immunity in vivo.","method":"Covalent binding assays; phospho-specific immunoblotting; LCK kinase activity assay; T cell functional assays; murine tumor models","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct covalent binding characterization, phosphosite analysis, in vivo tumor model, single lab","pmids":["35638332"],"is_preprint":false},{"year":2015,"finding":"Lck interacts with CRIF1 in mitochondria in a kinase-independent manner; mitochondrial Lck competitively interferes with CRIF1-Tid1 interaction (components of intramitochondrial translation machinery), repressing oxidative phosphorylation in leukemic T cells.","method":"Subcellular fractionation; confocal microscopy; proteomics; co-immunoprecipitation; proximity ligation assay; shRNA silencing of CRIF1; mitochondrial respiration assays","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity ligation assay, Co-IP, subcellular fractionation, functional metabolic assays, single lab","pmids":["26210498"],"is_preprint":false},{"year":2014,"finding":"Phosphorylation of Y192 in the LCK SH2 domain (promoted by Itk and TSAd) changes LCK substrate specificity by altering SH2 domain-binding partner preference; pY192-LCK preferentially binds regulators of the actin cytoskeleton; Itk and TSAd promote TCR-dependent Y192 phosphorylation.","method":"Phosphopeptide arrays; biochemical assays; T cell-cell conjugate assays; Y192 mutants; Itk/TSAd expression in T cells","journal":"Science signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphopeptide arrays with biochemical validation, defined upstream kinases, single lab","pmids":["25492967"],"is_preprint":false},{"year":2018,"finding":"TAOK3 (a serine/threonine kinase) prevents premature SHP-1-mediated inactivation of LCK following TCR engagement; TAOK3-deficient T cells show enhanced LCK-SHP-1 interaction and rapid TCR signal termination; TAOK3 reconstitution corrects this defect.","method":"TAOK3 knockdown in human T cells; LCK-SHP-1 co-immunoprecipitation; TCR signaling assays; IL-2 production; superantigen (LCK-independent) control","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with rescue, Co-IP, functional signaling assays, single lab","pmids":["30373850"],"is_preprint":false},{"year":2020,"finding":"Free (coreceptor-unbound) LCK shows higher activating Y394 phosphorylation, higher mobility, and greater kinase activity than CD8α-bound LCK in T hybridoma cells; free LCK mediates higher T cell activation than coreceptor-bound LCK.","method":"Single-molecule tracking; phospho-specific immunoblotting; kinase activity assays; T cell activation assays comparing free vs. coreceptor-bound LCK pools","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-molecule imaging and biochemical separation of LCK pools, single lab","pmids":["32571924"],"is_preprint":false},{"year":2010,"finding":"CD4-associated LCK activity stimulated by antagonist MHC-peptide complexes acts in a dominant negative mode to override stimulatory signals from agonist ligands; anti-CD4 antibody blocks the antagonist effect, implicating CD4-Lck activation in negative signaling.","method":"T cell stimulation with agonist/antagonist peptides; LCK kinase activity assay; CD4 blocking antibody; inositol phospholipid hydrolysis assay","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase activity assay with functional antagonism readout and blocking antibody, single lab","pmids":["8816805"],"is_preprint":false},{"year":2010,"finding":"SOCS1 and SOCS3 expression attenuates Lck kinase activity and reduces STAT5 phosphorylation in Lck-transformed leukemia cells; SOCS1 gene silencing in Lck-transformed LSTRA cells occurs via DNA hypermethylation.","method":"Ectopic SOCS1/SOCS3 expression; LCK kinase activity assay; STAT5 phosphorylation; methylation analysis; cell proliferation and apoptosis assays","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with kinase and STAT5 activity readouts, single lab","pmids":["20372794"],"is_preprint":false},{"year":2022,"finding":"LCK directly interacts with TRPM8 and phosphorylates it at Y1022; this phosphorylation promotes TRPM8 multimerization and enhances channel current density; phospho-TRPM8-Y1022 inhibits LCK Tyr505 phosphorylation in feedback regulation of LCK activity.","method":"Co-immunoprecipitation; in vitro kinase assay; Y1022F mutant; electrophysiology (TRPM8 current); multimerization assay; LCK ubiquitination analysis","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with mutagenesis, electrophysiology, single lab","pmids":["35665750"],"is_preprint":false},{"year":2010,"finding":"CD45 dephosphorylates LCK at Y394 upon CD44 ligation, dampening the amplitude of Src kinase-dependent signaling and determining the morphological outcome (round vs. elongated spreading) in T cells; CD45-/- cells show sustained Y394 phosphorylation and enhanced PI3K/PLC activation.","method":"CD45+/- T cells; CD44 antibody stimulation; confocal microscopy; phospho-Y394 immunoblotting; PI3K/PLC activity assays; actin visualization","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CD45 genetic comparison, phosphosite-specific antibody, signaling pathway readouts, single lab","pmids":["18981123"],"is_preprint":false},{"year":2010,"finding":"CD44 directly interacts with LCK (but not FYN) through the membrane-proximal region of the CD44 cytoplasmic domain in a zinc-dependent manner; this zinc-inducible interaction requires the first 13 amino acids of the CD44 cytoplasmic domain and the non-catalytic regions of LCK.","method":"Direct binding assay with recombinant purified proteins; zinc chelation (1,10-phenanthroline); progressive deletion mutagenesis; co-immunoprecipitation","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct binding with purified recombinant proteins plus deletion mutagenesis and cell-based Co-IP, single lab","pmids":["20417561"],"is_preprint":false},{"year":1993,"finding":"A kinase-dead Lck chimera (CD4-LckΔkinase) is more active than full-length in an antigen-specific T cell assay; SH2 or SH3 domain mutations moderately reduce activity; combined SH2+SH3 mutations largely abolish activity; indicating distinct, independent contributions of LCK domains to T cell activation.","method":"CD4-Lck chimeras with domain deletions/mutations; antigen-specific T cell hybridoma assays; T cell activation readouts","journal":"Cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain dissection chimeras in defined T cell hybridoma, single lab","pmids":["8358792"],"is_preprint":false},{"year":1995,"finding":"The unique (specific) domain of LCK is not required for intrinsic kinase activity or ATP binding, but is required for phosphorylation of physiological substrates and for induction of the IL-2 promoter, demonstrating that the unique domain determines substrate specificity.","method":"Unique domain deletion mutant; kinase activity assay with physiological and non-physiological substrates; IL-2 promoter reporter assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with deletion mutant plus cell-based functional assay, single lab","pmids":["7531706"],"is_preprint":false}],"current_model":"LCK is a Src-family non-receptor tyrosine kinase that is dually acylated (myristoylated at Gly2, palmitoylated at Cys3/Cys5 by DHHC2/DHHC21) for plasma membrane and lipid raft targeting; it associates with CD4 and CD8 co-receptors via a zinc clasp and with coreceptor-free TCR components (CD3ε RK motif, CD3ε BRS/Unique-domain ionic interaction, CD146) to initiate TCR signaling by phosphorylating ITAM tyrosines; its activity is positively regulated by activating autophosphorylation at Tyr394 (also targeted by UBR2-mediated K63-ubiquitination and trans-phosphorylation), negatively regulated by Csk-dependent phosphorylation at Tyr505 (reversed by CD45), and further modulated by phosphorylation of SH2-domain Tyr192 (which controls CD45 access and downstream partner specificity), while Cbl ubiquitin ligase and DUSP22/JKAP phosphatase provide negative feedback; a significant fraction (~40%) of LCK is constitutively active in resting T cells and its conformational state (open/active vs. closed/inactive) controls nanoscale clustering and substrate access; LCK additionally bridges phospho-ZAP70 (via SH2) to LAT (via SH3/proline-rich motif) to orchestrate downstream adaptor phosphorylation, phosphorylates substrates including PKCtheta (Y90), STAT3, FOXP3 (Y342), WASH (Y141), and TRPM8 (Y1022), and controls Th2 differentiation, CD4/CD8 lineage commitment, RICD, and Schwann cell myelination."},"narrative":{"mechanistic_narrative":"LCK is a Src-family non-receptor tyrosine kinase that initiates and sets the threshold of T cell receptor (TCR) signaling by phosphorylating proximal substrates at the plasma membrane and immunological synapse [PMID:9305640, PMID:29915297]. Membrane and lipid-raft targeting depend on N-terminal S-acylation: palmitoylation at Cys3/Cys5 is required for plasma-membrane localization and TCR signal reconstitution, with DHHC2 and the Fas-inducible DHHC21 acting as acyltransferases [PMID:9305640, PMID:26351666, PMID:22034844]. LCK is recruited to its activating context through multiple membrane anchors—a zinc-clasp association of its N-terminus with CD4 and CD8 coreceptor tails [PMID:14500983], an electrostatic interaction between the CD3ε basic-residue-rich sequence and the LCK Unique domain plus a ligand-exposed CD3ε RK motif binding the SH3 domain for coreceptor-free recruitment [PMID:32690949, PMID:28659468], and SH2-domain binding to anionic membrane lipids that is needed for engagement of the TCR ζ chain [PMID:27334919]. Catalytic output is governed by a conformational switch built on opposing tyrosine phosphorylations: activating autophosphorylation at Tyr394 is indispensable for activity and drives an open conformation that promotes nanoscale clustering of phospho-TCRs while excluding CD45 [PMID:7538674, PMID:29083415, PMID:23202272], whereas Csk-dependent and FAK-recruited Csk-mediated phosphorylation of the inhibitory Tyr505 closes the kinase, a state reversed by CD45 to license thymocyte development [PMID:7523116, PMID:24227778, PMID:10330160, PMID:18981123]. Phosphorylation of SH2-domain Tyr192 by Itk/TSAd both blocks CD45 access and redirects substrate/partner specificity toward actin regulators [PMID:28735895, PMID:25492967]. A substantial pool of LCK is constitutively active in resting T cells, maintained by the HSP90–CDC37 chaperone system that protects open/active LCK from ubiquitin-dependent degradation [PMID:20541955, PMID:15199125]. Negative feedback is imposed by the Cbl E3 ligase, which ubiquitinates active LCK for degradation via the SH3 domain, and by the phosphatases DUSP22/JKAP and SHP-1 acting on Tyr394; conversely UBR2-mediated K63-ubiquitination promotes Tyr394 activation [PMID:11904433, PMID:24714587, PMID:38225265, PMID:30373850]. Functionally, LCK bridges phospho-ZAP70 (through its SH2 domain) to LAT (through its SH3 domain) to coordinate downstream adaptor phosphorylation, sets the quantitative signal that directs CD4/CD8 lineage commitment, and shapes Th2 differentiation via GATA-3/T-bet [PMID:29915297, PMID:10755618, PMID:20237292]. Beyond the TCR, LCK phosphorylates a range of substrates including PKCθ (Tyr90), STAT3, FOXP3 (Tyr342), WASH (Tyr141) for NK cytotoxicity, and the TRPM8 channel (Tyr1022), and mediates β1-integrin/laminin signaling required for Schwann cell myelination [PMID:10652356, PMID:10617281, PMID:24155921, PMID:27441653, PMID:35665750, PMID:23715271].","teleology":[{"year":1993,"claim":"Established that LCK's non-catalytic SH2/SH3 domains and adaptor functions, not kinase activity alone, drive T cell activation, reframing LCK as more than a catalytic enzyme.","evidence":"CD4-Lck domain-deletion chimeras in antigen-specific T cell hybridoma assays","pmids":["8358792"],"confidence":"Medium","gaps":["Did not define direct binding partners of each domain","Chimera context may not reflect native LCK regulation"]},{"year":1995,"claim":"Defined the Unique domain as the determinant of physiological substrate specificity, separating intrinsic catalysis from biological output.","evidence":"Unique-domain deletion mutant with kinase assays on physiological vs non-physiological substrates and IL-2 promoter reporter","pmids":["7531706"],"confidence":"Medium","gaps":["Mechanism by which the Unique domain selects substrates not resolved","Membrane/partner context contributions not isolated"]},{"year":1995,"claim":"Identified Tyr394 as the activating autophosphorylation site and provided early evidence for a trans-activating kinase, framing how LCK is switched on.","evidence":"H2O2 stimulation of cells with Y394F/kinase-dead Lck mutants and kinase activity readouts","pmids":["7538674"],"confidence":"High","gaps":["Identity of the trans-activating kinase not established","Physiological (non-oxidative) trigger not defined here"]},{"year":1996,"claim":"Demonstrated LCK self-association via SH2/SH3 domains, providing a mechanism for trans-activation between LCK molecules.","evidence":"CD4-Lck chimeras and GST-SH2/SH3 pull-downs in Lck-positive vs Lck-negative T cells","pmids":["8798782"],"confidence":"Medium","gaps":["Stoichiometry and physiological relevance of dimers unclear","Whether dimerization is regulated during signaling not addressed"]},{"year":1997,"claim":"Showed that N-terminal palmitoylation is essential for membrane targeting and TCR signaling, separating catalytic competence from spatial positioning.","evidence":"Acylation-mutant LCK reconstituted in LCK-negative T cells with Ca2+ flux, CD69/NFAT and ZAP-70 association readouts","pmids":["9305640"],"confidence":"High","gaps":["Acyltransferase responsible not identified at this stage","Dynamics of palmitoylation not addressed"]},{"year":1999,"claim":"Established CD45 dephosphorylation of inhibitory Tyr505 as the in vivo activating step required for thymocyte development.","evidence":"Genetic epistasis with CD45-/- mice rescued by LckY505F transgene","pmids":["10330160"],"confidence":"High","gaps":["How CD45 access to LCK is spatially controlled not resolved here","Other CD45 substrates contribution not isolated"]},{"year":1999,"claim":"Connected LCK to downstream transcriptional and lipid-signaling outputs by showing it phosphorylates STAT3 and gates SHP-1/PI3K regulation.","evidence":"Baculovirus reconstitution with EMSA for STAT3; Co-IP and PI3K activity assays for SHP-1/p85","pmids":["10617281","10488096"],"confidence":"Medium","gaps":["Direct vs indirect phosphorylation in vivo not fully separated","Quantitative contribution to physiological signaling unclear"]},{"year":2000,"claim":"Showed that the quantitative level of LCK activity instructs the CD4/CD8 lineage decision, establishing LCK signal strength as a developmental rheostat.","evidence":"Reciprocal dominant-negative and constitutively active Lck transgenic mice on TCR-transgenic backgrounds","pmids":["10755618"],"confidence":"High","gaps":["Molecular threshold sensors downstream of LCK not defined","How signal duration vs amplitude is read not resolved"]},{"year":2000,"claim":"Identified PKCθ Tyr90 as a direct LCK substrate linking LCK to NFAT activation and proliferation.","evidence":"In vitro kinase assay, Co-IP, Y90F mutagenesis and T cell reporter assays","pmids":["10652356"],"confidence":"High","gaps":["Structural basis of LCK-PKCθ docking not defined","In vivo requirement not tested"]},{"year":2002,"claim":"Defined coreceptor and costimulatory control of LCK activation, showing CD4 recruits and CD28 sustains active LCK, and that Cbl provides ubiquitin-dependent negative feedback.","evidence":"Phosphospecific antibodies with blocking antibodies; Co-IP and Cbl-/- T cell line analysis with SH3 mutants","pmids":["11828322","11904433"],"confidence":"High","gaps":["How CD28 mechanistically sustains autophosphorylation not resolved","Cbl recognition determinants on LCK beyond SH3 contact unclear"]},{"year":2003,"claim":"Provided the structural basis for coreceptor selectivity by solving the zinc-clasp that folds CD4/CD8 tails with the LCK N-terminus.","evidence":"Solution NMR structures of CD4-Lck-Zn2+ and CD8α-Lck-Zn2+ ternary complexes","pmids":["14500983"],"confidence":"High","gaps":["Dynamics of clasp assembly during synapse formation not captured","Regulation of zinc availability not addressed"]},{"year":2004,"claim":"Linked LCK conformation to its turnover, showing open/active LCK is degraded unless protected by HSP90, independent of kinase activity.","evidence":"Conformational and kinase mutants in COS-7 with geldanamycin and ubiquitination assays","pmids":["15199125"],"confidence":"Medium","gaps":["E3 ligase mediating conformation-dependent degradation not identified here","Quantitative stability difference in primary cells not measured"]},{"year":2010,"claim":"Revealed that a constitutively active LCK pool pre-exists in resting T cells and sets TCR-ζ phosphorylation capacity, shifting the model from de novo activation to pre-poised signaling.","evidence":"Phosphospecific flow cytometry and biochemical fractionation in primary cells with HSP90 inhibition","pmids":["20541955"],"confidence":"High","gaps":["How active LCK is restrained from constitutive signaling not fully resolved","Spatial segregation from substrate at rest not defined here"]},{"year":2010,"claim":"Showed CD45 dephosphorylates the activating Tyr394 in additional contexts (CD44 ligation), establishing CD45 as both an activator and a dampener depending on the targeted tyrosine.","evidence":"CD45+/- T cells with CD44 stimulation, phospho-Y394 blotting and PI3K/PLC readouts","pmids":["18981123"],"confidence":"Medium","gaps":["How CD45 selects Y394 vs Y505 not mechanistically resolved","Generality across receptor contexts unclear"]},{"year":2012,"claim":"Demonstrated that LCK conformation directly controls nanoscale clustering, producing CD45-excluding, phospho-TCR-enriched domains that spatially favor signaling.","evidence":"Super-resolution PALM/STORM imaging with conformation-state mutants","pmids":["23202272"],"confidence":"High","gaps":["Trigger that shifts conformation in situ not defined","Cluster composition beyond TCR/CD45 not enumerated"]},{"year":2013,"claim":"Extended LCK function beyond lymphocytes, showing it transduces laminin/β1-integrin signals required for Schwann cell myelination.","evidence":"LCK inhibition, β1-integrin siRNA, Lck-/- mice and Rac-GTP/paxillin pathway readouts","pmids":["23715271"],"confidence":"High","gaps":["Direct LCK substrates in the Schwann cell pathway not all defined","Relationship to TCR-context regulation unknown"]},{"year":2013,"claim":"Identified FAK-recruited Csk as a TCR-induced brake on LCK, adding a spatial mechanism for inhibitory Tyr505 phosphorylation.","evidence":"FAK suppression in human T cells with Csk recruitment and LCK phosphorylation analysis","pmids":["24227778"],"confidence":"Medium","gaps":["Direct FAK-Csk-LCK assembly stoichiometry not resolved","Distinction between LCK and Fyn effects not fully separated"]},{"year":2014,"claim":"Established DUSP22/JKAP as a direct phosphatase inactivating LCK at Tyr394, providing a genetic brake whose loss promotes autoimmunity.","evidence":"In vitro phosphatase assay and JKAP knockout mice with EAE model","pmids":["24714587"],"confidence":"High","gaps":["Spatial regulation of JKAP-LCK encounter not defined","Relationship to other Y394 phosphatases not ranked"]},{"year":2014,"claim":"Showed Tyr192 phosphorylation rewires LCK SH2-domain partner preference toward actin regulators, linking a post-translational mark to substrate-selectivity switching.","evidence":"Phosphopeptide arrays and T cell conjugate assays with Itk/TSAd as upstream kinases","pmids":["25492967"],"confidence":"Medium","gaps":["Full pY192 interactome not mapped","In vivo consequence of altered specificity not established here"]},{"year":2014,"claim":"Expanded LCK substrate repertoire to FOXP3 (Tyr342) and to receptor-localized activation via SAP at NTB-A, linking LCK to Treg/invasion programs and restimulation-induced cell death.","evidence":"In vitro kinase assays with Y342F mutant and invasion assays; Co-IP with NTB-A ITSM mutants and RICD assays in XLP patient cells","pmids":["24155921","24688028"],"confidence":"Medium","gaps":["Physiological setting of FOXP3 phosphorylation by LCK unclear","Direct vs SAP-bridged LCK recruitment at NTB-A not fully separated"]},{"year":2017,"claim":"Resolved the Tyr192 mechanism as a gate on CD45 access, integrating SH2-domain phosphorylation with the activation switch and thymocyte development.","evidence":"Y192 mutants with Co-IP, phospho-blotting and retrogenic mouse thymocyte assays","pmids":["28735895"],"confidence":"High","gaps":["Kinetics of pY192/CD45 competition in vivo not measured","Coordination with pY394/pY505 cycling not fully integrated"]},{"year":2017,"claim":"Defined the CD3ε BRS-LCK Unique-domain ionic interaction as an antigen-unlocked targeting mechanism for coreceptor-independent TCR phosphorylation.","evidence":"TCR reconstitution with electrostatic mapping, mutagenesis and phosphorylation assays","pmids":["28659468"],"confidence":"High","gaps":["How antigen mechanically unlocks BRS not resolved","Quantitative contribution vs coreceptor route unclear"]},{"year":2017,"claim":"Defined SH2-domain lipid binding and Rab11-FIP3-controlled endosomal delivery as spatial determinants of LCK function at the synapse.","evidence":"NMR/membrane binding assays with lipid-binding mutants; FIP3 gain/loss-of-function with imaging and signaling readouts","pmids":["27334919","28235866"],"confidence":"Medium","gaps":["Interplay between lipid binding and phospho-Tyr docking not resolved","Trafficking machinery beyond FIP3 not mapped"]},{"year":2017,"claim":"Used genetic code expansion to prove Tyr394 autophosphorylation is indispensable and that LCK self-opens, with coreceptors enhancing activity, providing a quantitative live-cell view of the switch.","evidence":"Photocaged active-site lysine LCK with FRET biosensor imaging and live-cell kinetics, CD4/CD8 cotransfection","pmids":["29083415"],"confidence":"High","gaps":["In vivo relevance of measured kinetics not tested","Coupling to clustering not directly imaged here"]},{"year":2018,"claim":"Defined the bridging function of LCK between phospho-ZAP70 and LAT, explaining how proximal phosphorylation is spatially coordinated.","evidence":"Co-IP, phosphoproteomics, LAT proline-rich-motif mutants and retrogenic mice","pmids":["29915297"],"confidence":"High","gaps":["Stoichiometry of the ZAP70-LCK-LAT assembly not defined","Dynamics of bridge formation during signaling unresolved"]},{"year":2018,"claim":"Identified TAOK3 as protecting LCK from premature SHP-1 inactivation and ICOS transmembrane-domain-driven LCK recruitment for costimulation, broadening LCK's receptor inputs.","evidence":"TAOK3 knockdown with LCK-SHP-1 Co-IP; ICOS TMD-swap mutants with PI3K recruitment and calcium flux","pmids":["30373850","30523347"],"confidence":"Medium","gaps":["Mechanism of TAOK3 control over SHP-1 access not resolved","Direct vs indirect LCK-ICOS contact not structurally defined"]},{"year":2020,"claim":"Established a ligand-exposed CD3ε RK motif binding the LCK SH3 domain and showed free LCK is more active than coreceptor-bound LCK, refining the model of how LCK is positioned and activated at the TCR.","evidence":"Biochemical binding/mutagenesis with thymocyte and CAR-T assays; single-molecule tracking comparing free vs CD8α-bound LCK pools","pmids":["32690949","32571924"],"confidence":"High","gaps":["Balance between coreceptor-bound and free LCK in vivo not quantified","How the two recruitment modes are coordinated unclear"]},{"year":2022,"claim":"Identified CD146 as a coreceptor-free LCK SH3 partner and LAG3 as a coreceptor-LCK dissociator via local pH, mechanistically explaining both LCK recruitment and inhibitory checkpoint disengagement.","evidence":"Co-IP and direct binding with CD146 knockout mice; LAG3 cytoplasmic mutants with pH-sensor imaging and CD4/CD8-LCK dissociation measurement","pmids":["34491908","35437325"],"confidence":"Medium","gaps":["Physiological balance between CD146 and other coreceptor-free routes unclear","Generality of pH-driven dissociation beyond LAG3 unknown"]},{"year":2022,"claim":"Extended LCK substrates to the TRPM8 channel (Tyr1022) with reciprocal feedback on LCK Tyr505, and identified disulfiram as a covalent LCK activator, opening pharmacological tuning of LCK.","evidence":"In vitro kinase assay/electrophysiology for TRPM8; covalent binding and tumor models for disulfiram","pmids":["35665750","35638332"],"confidence":"Medium","gaps":["Physiological context of LCK-TRPM8 signaling unclear","Selectivity of disulfiram for LCK over other targets not fully established"]},{"year":2024,"claim":"Defined UBR2-mediated K63-ubiquitination at Lys99/Lys276 as a positive driver of LCK Tyr394 activation, counter-regulated by DUSP22, with disease relevance in SLE T cells.","evidence":"scRNA-seq, K63-linkage ubiquitination biochemistry, UBR2 knockout, DUSP22 phosphatase assays and SLE patient samples","pmids":["38225265"],"confidence":"High","gaps":["How K63-ubiquitin promotes Y394 phosphorylation mechanistically not resolved","Interplay with Cbl K48-degradation pathway not integrated"]},{"year":null,"claim":"How the multiple, overlapping recruitment routes (coreceptor zinc-clasp, CD3ε BRS/RK, CD146, lipid binding) and the layered post-translational controls (Y394/Y505/Y192, K63/K48 ubiquitination, palmitoylation) are quantitatively integrated to set a single activation threshold in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No unified quantitative model linking conformation, ubiquitination, localization and clustering","Relative weighting of free vs coreceptor-bound LCK pools in physiological responses unknown","Full substrate repertoire and its context-dependence incompletely mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,9,17,25,30,40,48]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[2,3,29]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[32]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,9,14]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[16,47]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,12,14,32]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[34]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[42]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,9,13,23]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[9,26,39]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6,23,26]}],"complexes":["ZAP70-LCK-LAT proximal signaling assembly","CD4/CD8-LCK zinc-clasp coreceptor complex","HSP90-CDC37 chaperone-LCK complex","TCR-linked HSP90-LCK-FYN-glucocorticoid receptor complex"],"partners":["CD4","CD8","CD3E","ZAP70","LAT","CD45","CBL","DUSP22"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P06239","full_name":"Tyrosine-protein kinase Lck","aliases":["Leukocyte C-terminal Src kinase","LSK","Lymphocyte cell-specific protein-tyrosine kinase","Protein YT16","Proto-oncogene Lck","T cell-specific protein-tyrosine kinase","p56-LCK"],"length_aa":509,"mass_kda":58.0,"function":"Non-receptor tyrosine-protein kinase that plays an essential role in the selection and maturation of developing T-cells in the thymus and in the function of mature T-cells (PubMed:2470098). Plays a key role in T-cell antigen receptor (TCR)-linked signal transduction pathways (PubMed:2470098). Constitutively associated with the cytoplasmic portions of the CD4 and CD8 surface receptors (PubMed:2470098). Association of the TCR with a peptide antigen-bound MHC complex facilitates the interaction of CD4 and CD8 with MHC class II and class I molecules, respectively, thereby recruiting the associated LCK protein to the vicinity of the TCR-CD3 complex (PubMed:2470098). LCK then phosphorylates tyrosine residues within the immunoreceptor tyrosine-based activation motifs (ITAM) of the cytoplasmic tails of the TCR-gamma chains and CD3 subunits, initiating the TCR-CD3 signaling pathway (PubMed:2470098, PubMed:40592325). Once stimulated, the TCR recruits the tyrosine kinase ZAP70, that becomes phosphorylated and activated by LCK. Following this, a large number of signaling molecules are recruited, ultimately leading to lymphokine production. LCK also contributes to signaling by other receptor molecules. Associates directly with the cytoplasmic tail of CD2, which leads to hyperphosphorylation and activation of LCK. Also plays a role in the IL2 receptor-linked signaling pathway that controls the T-cell proliferative response. Binding of IL2 to its receptor results in increased activity of LCK. Is expressed at all stages of thymocyte development and is required for the regulation of maturation events that are governed by both pre-TCR and mature alpha beta TCR. Phosphorylates other substrates including RUNX3, PTK2B/PYK2, the microtubule-associated protein MAPT, RHOH or TYROBP. Interacts with FYB2 (PubMed:27335501)","subcellular_location":"Cell membrane; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/P06239/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LCK","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/LCK","total_profiled":1310},"omim":[{"mim_id":"620513","title":"UNC119 LIPID-BINDING CHAPERONE B; UNC119B","url":"https://www.omim.org/entry/620513"},{"mim_id":"619713","title":"CADHERIN-RELATED FAMILY, MEMBER 2; CDHR2","url":"https://www.omim.org/entry/619713"},{"mim_id":"619374","title":"IMMUNODEFICIENCY 81; IMD81","url":"https://www.omim.org/entry/619374"},{"mim_id":"618621","title":"ZDHHC PALMITOYLTRANSFERASE 2; ZDHHC2","url":"https://www.omim.org/entry/618621"},{"mim_id":"618478","title":"FYN-BINDING PROTEIN 2; FYB2","url":"https://www.omim.org/entry/618478"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":325.6}],"url":"https://www.proteinatlas.org/search/LCK"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P06239","domains":[{"cath_id":"2.30.30.40","chopping":"64-117","consensus_level":"high","plddt":93.7776,"start":64,"end":117},{"cath_id":"3.30.505.10","chopping":"127-210","consensus_level":"high","plddt":91.716,"start":127,"end":210},{"cath_id":"3.30.200.20","chopping":"237-318","consensus_level":"medium","plddt":88.4237,"start":237,"end":318},{"cath_id":"1.10.510.10","chopping":"322-384_402-498","consensus_level":"medium","plddt":94.3112,"start":322,"end":498}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P06239","model_url":"https://alphafold.ebi.ac.uk/files/AF-P06239-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P06239-F1-predicted_aligned_error_v6.png","plddt_mean":83.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LCK","jax_strain_url":"https://www.jax.org/strain/search?query=LCK"},"sequence":{"accession":"P06239","fasta_url":"https://rest.uniprot.org/uniprotkb/P06239.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P06239/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P06239"}},"corpus_meta":[{"pmid":"15489916","id":"PMC_15489916","title":"Function 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regulation.","date":"2020","source":"Immunologic research","url":"https://pubmed.ncbi.nlm.nih.gov/32794043","citation_count":18,"is_preprint":false},{"pmid":"35665750","id":"PMC_35665750","title":"The LCK-14-3-3ζ-TRPM8 axis regulates TRPM8 function/assembly and promotes pancreatic cancer malignancy.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35665750","citation_count":18,"is_preprint":false},{"pmid":"26210498","id":"PMC_26210498","title":"Lymphocyte-specific protein tyrosine kinase (Lck) interacts with CR6-interacting factor 1 (CRIF1) in mitochondria to repress oxidative phosphorylation.","date":"2015","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26210498","citation_count":18,"is_preprint":false},{"pmid":"1953650","id":"PMC_1953650","title":"Partial purification and characterization of the lck protein-tyrosine kinase from bovine thymus.","date":"1991","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/1953650","citation_count":18,"is_preprint":false},{"pmid":"33225946","id":"PMC_33225946","title":"Tyrosine 192 within the SH2 domain of the Src-protein tyrosine kinase p56Lck regulates T-cell activation independently of Lck/CD45 interactions.","date":"2020","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/33225946","citation_count":18,"is_preprint":false},{"pmid":"30373850","id":"PMC_30373850","title":"TAOK3 Regulates Canonical TCR Signaling by Preventing Early SHP-1-Mediated Inactivation of LCK.","date":"2018","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/30373850","citation_count":18,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45996,"output_tokens":12477,"usd":0.162572,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":23657,"output_tokens":8560,"usd":0.166142,"stage2_stop_reason":"end_turn"},"total_usd":0.328714,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"S-acylation (palmitoylation) of LCK at Cys3 and Cys5 at the N-terminus is required for plasma membrane targeting and TCR signaling; a non-S-acylated LCK mutant is catalytically active but cannot reach the plasma membrane and fails to phosphorylate CD8-zeta or reconstitute TCR signaling in LCK-negative T cells.\",\n      \"method\": \"Transient transfection of COS-18 cells and LCK-negative JCam-1.6 T cells with LCK acylation mutants; functional assays including Ca2+ flux, CD69/NFAT induction, ZAP-70 association\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal functional assays with site-specific mutants, reconstitution in LCK-negative cells\",\n      \"pmids\": [\"9305640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"LCK associates with CD4 and CD8 coreceptor cytoplasmic tails via a zinc-coordinated 'zinc clasp' heterodimeric domain; both coreceptor tails and the LCK N-terminus are unstructured in isolation but fold together in the presence of Zn2+.\",\n      \"method\": \"Solution NMR structure determination of ternary CD4-Lck-Zn2+ and CD8alpha-Lck-Zn2+ complexes\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with functional validation, defines molecular basis of zinc-dependent co-receptor association\",\n      \"pmids\": [\"14500983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Phosphorylation of Tyr394 (the activating autophosphorylation site) is required for H2O2-induced activation of LCK; additionally, a kinase other than LCK itself can phosphorylate Tyr394, suggesting a trans-activating kinase exists.\",\n      \"method\": \"In vivo H2O2 treatment of cells expressing Lck mutants (Y394F, kinase-inactive); kinase activity assays; expression in LCK-negative cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro and in vivo mutational analysis with kinase activity readouts, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"7538674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"LCK can autophosphorylate at both Tyr394 (activating) and Tyr505 (inhibitory) in vitro; autophosphorylation at Tyr505 may represent an accessory mechanism for self-downregulation of kinase activity.\",\n      \"method\": \"Recombinant GST-Lck expression in E. coli with phosphosite mutants (Y394F, Y505F, K273E, double mutant); in vivo and in vitro autophosphorylation assays; phosphopeptide mapping\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution in bacteria with mutagenesis and phosphopeptide mapping, multiple mutants tested\",\n      \"pmids\": [\"7523116\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CD4 recruits LCK to the T cell–APC interface (immunological synapse), while CD28 sustains LCK autophosphorylation; TCR cross-linking alone is insufficient to stimulate LCK autophosphorylation.\",\n      \"method\": \"Phosphospecific antisera to activated LCK; stimulation of T cells with antigen-presenting cells; blocking antibodies to CD4 and CD28\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphospecific antibody readout with functional co-stimulation dissection, single lab, two orthogonal methods\",\n      \"pmids\": [\"11828322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Cbl ubiquitin ligase negatively regulates LCK by ubiquitinating it upon TCR/CD4 co-ligation, leading to LCK degradation; LCK kinase activity and Cbl RING finger (E3 ligase) activity are both required for LCK ubiquitination; the LCK SH3 domain mediates Cbl-LCK association.\",\n      \"method\": \"Co-immunoprecipitation; Cbl-/- T cell line analysis; co-expression in 293T cells; reporter assays; SH3 domain mutants\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic loss-of-function cell line, mutagenesis, functional reporter assays\",\n      \"pmids\": [\"11904433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"CD45 dephosphorylation of the inhibitory Tyr505 of LCK is required for thymocyte development; expression of the constitutively active Y505F LCK mutant rescues thymocyte development in CD45-deficient mice.\",\n      \"method\": \"Genetic epistasis: CD45-/- mice crossed with LckY505F transgenic mice and DO11.10 TCR transgenic mice; T cell functional assays (CD69, IL-2, proliferation)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in vivo with defined molecular mechanism, replicated functionally in multiple assays\",\n      \"pmids\": [\"10330160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PKCepsilon forms a signaling module with LCK in cardiac cells: PKCepsilon interacts with, phosphorylates, and activates LCK; disruption of PKCepsilon-LCK modules by Lck gene ablation abrogates cardioprotection from ischemic preconditioning.\",\n      \"method\": \"Functional proteomics; co-immunoprecipitation; transgenic cardiac-specific PKCepsilon activation; Lck knockout mice; infarct size measurement\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, in vivo genetic knockout with defined phenotype, single lab\",\n      \"pmids\": [\"11854322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Constitutively active LCK is present in unstimulated naive T cells and thymocytes (~40% of total LCK); the amount of active LCK does not change after TCR/coreceptor engagement but determines the extent of TCR-zeta phosphorylation; maintenance of active LCK requires the HSP90-CDC37 chaperone complex.\",\n      \"method\": \"Phosphospecific antibodies; flow cytometry; biochemical fractionation; HSP90 inhibitor treatment; quantification in primary cells\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods, primary cells, functional quantitative readout, demonstrated HSP90 dependence\",\n      \"pmids\": [\"20541955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"LCK acts as a molecular bridge facilitating ZAP70-dependent LAT phosphorylation: LCK SH2 domain binds phospho-ZAP70, while its SH3 domain binds a conserved proline-rich motif in LAT, co-localizing ZAP70 and LAT; elimination of the LAT proline-rich motif compromises TCR signaling and T cell development.\",\n      \"method\": \"Co-immunoprecipitation; phosphoproteomic mass spectrometry; LAT mutants; retrogenic mice; T cell signaling assays\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, mutagenesis, in vivo mouse model, MS phosphoproteomics\",\n      \"pmids\": [\"29915297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The phosphatase JKAP/DUSP22 directly inactivates LCK by dephosphorylating Tyr394; JKAP-knockout T cells display enhanced proliferation and cytokine production; JKAP-deficient mice are more susceptible to EAE.\",\n      \"method\": \"In vitro phosphatase assay; JKAP knockout mice; T cell proliferation and cytokine assays; EAE model; adoptive transfer\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro enzyme-substrate assay, genetic knockout with defined molecular and in vivo phenotypes\",\n      \"pmids\": [\"24714587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Asparagine directly binds to LCK and modulates its phosphorylation at Tyr394 and Tyr505, thereby enhancing LCK kinase activity and TCR signaling in CD8+ T cells, independently of metabolic flux changes.\",\n      \"method\": \"Binding assays; phospho-specific immunoblotting; Asn restriction experiments; SLC1A5 inhibition; in vitro and in vivo T cell activation assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated, phosphosite regulation shown, single lab, metabolic independence confirmed\",\n      \"pmids\": [\"33420490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LCK conformational state controls its nanoscale clustering: open/active conformation induces LCK clustering; closed/inactive conformation prevents clustering; conformation-driven clusters contain phosphorylated TCRs but exclude the phosphatase CD45.\",\n      \"method\": \"Super-resolution microscopy (PALM/STORM); LCK conformation-state mutants; single-molecule imaging in T cells\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — super-resolution imaging with conformation-specific mutants, direct spatial and functional consequence demonstrated\",\n      \"pmids\": [\"23202272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A previously unknown RK motif in the CD3ε cytoplasmic tail binds to the LCK SH3 domain in a noncanonical manner; this motif is accessible only upon TCR ligation, allowing ligand-induced LCK recruitment; binding augments local LCK activity, CD3 phosphorylation, and T cell activation.\",\n      \"method\": \"Biochemical binding assays; mutagenesis; cell-based T cell activation assays; thymocyte development assays; CAR-T cell in vitro and in vivo efficacy\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding characterization with mutagenesis, in vivo thymocyte development, multiple functional readouts\",\n      \"pmids\": [\"32690949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The ionic interaction between the basic residue-rich sequence (BRS) of CD3ε and acidic residues in the Unique domain of LCK selectively targets LCK to CD3ε and controls TCR phosphorylation initiation upon antigen stimulation; CD3ε BRS is membrane-sequestered at rest and unlocked by antigen stimulation.\",\n      \"method\": \"TCR reconstitution system; electrostatic interaction mapping; mutagenesis; phosphorylation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic reconstitution, mutagenesis, defined ionic interaction domain, multiple orthogonal approaches\",\n      \"pmids\": [\"28659468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LAG3 causes dissociation of LCK from the CD4 or CD8 co-receptor via its acidic tandem glutamic acid-proline repeat in the cytoplasmic tail lowering local pH at the immune synapse, resulting in loss of co-receptor-TCR signaling.\",\n      \"method\": \"Co-immunoprecipitation; pH sensor imaging; LAG3 cytoplasmic domain mutants; T cell activation assays; CD4/CD8-LCK dissociation measurement\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic dissection with domain mutants, co-IP, live-cell imaging, functional T cell readouts\",\n      \"pmids\": [\"35437325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"SHP-1 co-immunoprecipitates with the p85 regulatory subunit of PI3K in T cells; this interaction is increased by TCR ligation and requires Lck-mediated phosphorylation of SHP-1 at Tyr564; SHP-1 then dephosphorylates p85 and reduces PI3K activity and Akt phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation; constitutively active Lck co-expression; SHP-1 truncation mutants; PI3K enzyme activity assay; pAkt immunoblotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with truncation mutants, enzyme activity assay, single lab\",\n      \"pmids\": [\"10488096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Lck tyrosine phosphorylates PKCtheta at Tyr90 in its regulatory domain, both in vitro and in intact T cells; this phosphorylation is required for PKCtheta-dependent enhancement of T cell proliferation and NFAT activation; Lck associates with the regulatory domain of PKCtheta constitutively, enhanced by T cell activation, via both SH2 and SH3 domains.\",\n      \"method\": \"In vitro kinase assay; co-immunoprecipitation; site-directed mutagenesis (Y90F); T cell reporter assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus mutagenesis and cell-based functional assays, single lab\",\n      \"pmids\": [\"10652356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Fas receptor engagement leads to a rapid and transient increase in LCK palmitoylation; this dynamic palmitoylation is required for downstream Fas signaling (ZAP70, PLC-γ1 activation) and Fas-mediated apoptosis; DHHC21 is the palmitoyl acyl transferase responsible.\",\n      \"method\": \"Palmitoylation assay; DHHC21 knockdown; inhibition of palmitoylation; apoptosis assay; downstream signaling readouts\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — palmitoylation biochemistry, DHHC21 knockdown, functional apoptosis readout, single lab\",\n      \"pmids\": [\"26351666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DHHC2, a DHHC family protein S-acyltransferase localized to the ER and Golgi, palmitoylates LCK in T cells; DHHC2 knockdown reduces LCK S-acylation and partially delocalizes LCK from membranes.\",\n      \"method\": \"siRNA knockdown of DHHC2; S-acylation assay; subcellular fractionation; LckN10-GFP overexpression reporter\",\n      \"journal\": \"Molecular membrane biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA loss-of-function, acylation biochemistry, localization assay, single lab\",\n      \"pmids\": [\"22034844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Activated LCK conformations (open/active) are targeted for ubiquitination and degradation, while HSP90 binding rescues active LCK from degradation; both processes are triggered by conformational changes (open SH2/SH3), not by kinase activity or phosphorylation at S42/S59 or Y394; the Src inhibitor PP2 (binding ATP site) reduces ubiquitination and Hsp90 dependence.\",\n      \"method\": \"Lck conformational and kinase mutants expressed in COS-7 cells; Hsp90 inhibitor geldanamycin; ubiquitination assays; western blotting in T cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of multiple sites, pharmacological probes, single lab\",\n      \"pmids\": [\"15199125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A phosphosite at Y192 within the LCK SH2 domain inhibits CD45 association with LCK in cells, preventing CD45-mediated dephosphorylation of the C-terminal inhibitory tail (Y505), thus blocking LCK adoption of the active open conformation; Y192 mutation blocks proximal TCR signaling and thymocyte development.\",\n      \"method\": \"Y192 mutant LCK; co-immunoprecipitation; phosphospecific immunoblotting; retrogenic mice; thymocyte development assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mutagenesis, Co-IP, in vivo thymocyte model, multiple orthogonal signaling readouts\",\n      \"pmids\": [\"28735895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Cdc2 kinase associates with LCK through the LCK SH3 domain (only active Cdc2 associates) and phosphorylates LCK in vitro at mitosis, shifting its electrophoretic mobility; this association is selective and not shared by Csk or Syk.\",\n      \"method\": \"Co-immunoprecipitation with anti-Lck and anti-Cdc2 antibodies; Suc1-agarose affinity; in vitro kinase assay; mitotic cell arrest\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus Co-IP, single lab\",\n      \"pmids\": [\"8910336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Quantitative differences in LCK signal (activity level) control the CD4/CD8 lineage decision in thymocytes: reduced LCK activity causes class II-restricted thymocytes to develop into CD8 T cells; increased LCK activity causes class I-restricted thymocytes to develop into CD4 T cells.\",\n      \"method\": \"Transgenic mice with altered Lck activity (dominant-negative or constitutively active); TCR transgenic backgrounds; thymocyte lineage analysis\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in vivo with quantitative activity manipulation, replicated with two reciprocal transgenic models\",\n      \"pmids\": [\"10755618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LCK mediates Th2 differentiation through regulation of T-bet and GATA-3 expression; in lck-/- Th2 cells, GATA-3 is reduced and T-bet is aberrantly elevated, leading to IFN-gamma production; overexpression of GATA-3 restores IL-4 expression in lck-/- Th2 cells.\",\n      \"method\": \"Lck knockout mouse model; Th1/Th2 skewing; cytokine assays; transcription factor expression analysis; GATA-3 overexpression rescue\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with defined transcription factor mechanism, rescue experiment, single lab\",\n      \"pmids\": [\"20237292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Lck directly activates STAT3 by tyrosine phosphorylation, enhancing STAT3 DNA binding activity; this was demonstrated in a baculovirus reconstitution system and in mammalian cells expressing constitutively active Lck.\",\n      \"method\": \"Baculovirus co-expression of Lck and STAT3; exogenous Lck addition to STAT3; Lck-specific inhibitor PP1; constitutively active Lck stable cell lines; EMSA\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with inhibitor validation and cell-based confirmation, single lab\",\n      \"pmids\": [\"10617281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"LCK mediates β1-integrin signaling in Schwann cells downstream of laminin: LCK activation by laminin/β1-integrin drives a paxillin/CrkII/Rac-GTP pathway to induce lamellipodia; LCK-/- mice show delays in myelination, thinner myelin with abnormal g-ratios, and aberrant myelin outfoldings.\",\n      \"method\": \"LCK inhibitor in Schwann cells; siRNA knockdown of β1-integrin; Lck-/- mice; myelination assays; Rac-GTP pull-down\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout in vivo, pharmacological inhibition, siRNA, defined pathway readouts in multiple systems\",\n      \"pmids\": [\"23715271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Tyrosine-phosphorylated paxillin associates with LCK via the LCK SH2 domain in T cells following CD45 or CD3 stimulation; paxillin phosphorylation is dependent on LCK expression.\",\n      \"method\": \"Co-immunoprecipitation; GST-SH2 domain pull-down; LCK-deficient T cell reconstitution; western blotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GST pull-down and Co-IP with LCK-deficient cell validation, single lab\",\n      \"pmids\": [\"9488700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Glucocorticoid receptor is part of a TCR-linked multiprotein complex containing HSP90, LCK, and FYN; short-term glucocorticoid treatment causes dissociation of this complex, resulting in impaired LCK/FYN activation and TCR signaling; HSP90 is required for complex assembly.\",\n      \"method\": \"Co-immunoprecipitation; GC receptor siRNA; HSP90 siRNA; LCK/FYN activity assays; T cell stimulation\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with siRNA knockdown validation, single lab\",\n      \"pmids\": [\"16888650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Autophosphorylation of the LCK activation-loop (Y394) is indispensable for catalytic activity; LCK can stimulate its own activation by adopting a more open conformation; CD4 and CD8 coreceptors enhance LCK kinase activity.\",\n      \"method\": \"Genetic code expansion (photocaged lysine replacing active-site K) to generate LCK*; FRET biosensor imaging; biochemical phosphorylation kinetics in live cells; CD4/CD8 cotransfection\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — novel optogenetic/genetic code expansion tool with quantitative live-cell imaging, mutagenesis, and biochemical validation\",\n      \"pmids\": [\"29083415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"LCK phosphorylates FOXP3 at Tyr342, stabilizing FOXP3 expression; phospho-FOXP3 then suppresses LCK-induced MMP9, SKP2, and VEGF-A expression; the Y342F FOXP3 mutant abolishes suppression of MMP9 and cell invasion.\",\n      \"method\": \"Co-immunoprecipitation; in vitro kinase assay; site-directed mutagenesis (Y342F); invasion assays; western blotting\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay plus mutagenesis and functional invasion assay, single lab\",\n      \"pmids\": [\"24155921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"LCK-dependent activation of FYN requires LCK to be kinase-active and partition to lipid rafts, mediated by the C-terminal YQPQP sequence; only LR-associated kinase-active LCK co-immunoprecipitates with and activates FYN.\",\n      \"method\": \"Lipid raft fractionation; Co-immunoprecipitation; Lck C-terminal truncation and kinase mutants in NIH 3T3 and T cells; FYN kinase activity assay; IL-2 reporter\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, lipid raft fractionation, mutagenesis with functional readout, single lab\",\n      \"pmids\": [\"18660530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The Lck SH2 domain binds anionic plasma membrane lipids (including PI(4,5)P2 and PI(3,4,5)P3) through a surface-exposed basic/aromatic/hydrophobic site distinct from the phospho-Tyr binding pocket; mutation of lipid-binding residues greatly reduces LCK interaction with TCR zeta chain and overall TCR signaling activity.\",\n      \"method\": \"NMR analysis; electrostatic potential calculation; mutational studies; membrane binding assays; TCR signaling assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR with mutagenesis and functional TCR signaling validation, single lab\",\n      \"pmids\": [\"27334919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The LCK SH3 domain enables LCK to dimerize (interact with itself via SH2/SH3 domains); kinase-dead CD4-Lck lacking catalytic domain can enhance tyrosine phosphorylation by recruiting endogenous active Lck via SH2/SH3 interactions; this dimerization requires endogenous LCK.\",\n      \"method\": \"CD4-Lck chimeras in Lck-positive and Lck-negative (JCam1.6) T cells; GST-SH2/SH3 pull-down from T cell lysates; tyrosine phosphorylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain deletion chimeras, GST pull-down, Lck-negative reconstitution, single lab\",\n      \"pmids\": [\"8798782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Rab11-FIP3 controls Lck subcellular localization and delivery to the immunological synapse; FIP3 overexpression or silencing modifies Lck endosomal localization and alters TCR-proximal signaling (zeta, ZAP70, LAT phosphorylation, Ca2+ flux, IL-2 expression), as well as steady-state TCR-CD3 surface expression.\",\n      \"method\": \"FIP3 overexpression and siRNA silencing in human T cells; confocal microscopy; signaling assays (phosphotyrosine, Ca2+ flux); IL-2 reporter; flow cytometry\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with imaging and signaling readouts, single lab\",\n      \"pmids\": [\"28235866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SAP facilitates recruitment and activation of LCK (but not FYN) at NTB-A receptors during TCR restimulation; NTB-A-associated LCK activity is enhanced in SAP-dependent manner, amplifying proximal TCR signaling and restimulation-induced cell death (RICD); both NTB-A ITSM motifs are required.\",\n      \"method\": \"Co-immunoprecipitation; NTB-A ITSM mutants; SAP siRNA; LCK kinase activity assay; RICD assay in XLP patient T cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mutants, patient-derived cells, SAP siRNA, functional RICD readout, single lab\",\n      \"pmids\": [\"24688028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CD146 directly interacts with the SH3 domain of coreceptor-free LCK via its cytoplasmic domain; CD146 dimerization upon TCR ligation recruits LCK and promotes LCK autophosphorylation; CD146 deficiency impairs thymocyte development and peripheral T cell activation.\",\n      \"method\": \"Co-immunoprecipitation; direct binding assays; CD146 knockout mice; thymocyte development analysis; LCK autophosphorylation assay\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay, Co-IP, genetic knockout in vivo, single lab\",\n      \"pmids\": [\"34491908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBR2 E3 ubiquitin ligase induces Lys63-linked ubiquitination of LCK at Lys99 and Lys276, followed by Tyr394 phosphorylation and activation during TCR signaling; DUSP22 dephosphorylates UBR2, leading to its degradation and thus indirectly limiting LCK activation; UBR2-mediated K63-ubiquitination of LCK is elevated in SLE patient T cells.\",\n      \"method\": \"Single-cell RNA sequencing; co-immunoprecipitation; ubiquitination assays (K63 linkage); UBR2 knockout; DUSP22 phosphatase assays; LCK kinase activity; SLE patient samples\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, K63 ubiquitination biochemistry, genetic KO, patient samples), single lab\",\n      \"pmids\": [\"38225265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"FAK negatively regulates LCK activity in T cells by recruiting C-terminal Src kinase (Csk) to the membrane/receptor complex after TCR activation; in the absence of FAK, inhibitory phosphorylation of LCK (and/or Fyn) is impaired, resulting in augmented TCR signaling.\",\n      \"method\": \"FAK inhibition/suppression in primary human T cells; Csk recruitment assay; LCK phosphorylation analysis; TCR signaling assays\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function, defined molecular pathway (FAK→Csk→LCK), single lab\",\n      \"pmids\": [\"24227778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Lck transmembrane domain of ICOS promotes LCK association with ICOS; this TMD-enabled LCK association is required for both PI3K-p85 recruitment to ICOS and calcium mobilization costimulation; ICOS cytoplasmic domain is dispensable for calcium costimulation.\",\n      \"method\": \"ICOS TMD swap mutants; co-immunoprecipitation; PI3K recruitment assay; calcium flux; in vivo TFH/GC formation\",\n      \"journal\": \"Cellular & molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-swap mutants, Co-IP, in vivo mouse model, single lab\",\n      \"pmids\": [\"30523347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"LCK interacts with WASH and induces WASH phosphorylation at Y141; this Lck-mediated phosphorylation is required for lytic granule polarization and NK cell cytotoxicity.\",\n      \"method\": \"Co-immunoprecipitation; WASH Y141F mutant; WASH knockdown; lytic granule polarization assay; cytotoxicity assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, phosphosite mutagenesis, functional cytotoxicity assay, single lab\",\n      \"pmids\": [\"27441653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Disulfiram (DSF) covalently binds to Cys20/Cys23 residues of LCK and enhances LCK Tyr394 phosphorylation, promoting LCK kinase activity and effector T cell function; this mechanism enhances anti-tumor immunity in vivo.\",\n      \"method\": \"Covalent binding assays; phospho-specific immunoblotting; LCK kinase activity assay; T cell functional assays; murine tumor models\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct covalent binding characterization, phosphosite analysis, in vivo tumor model, single lab\",\n      \"pmids\": [\"35638332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Lck interacts with CRIF1 in mitochondria in a kinase-independent manner; mitochondrial Lck competitively interferes with CRIF1-Tid1 interaction (components of intramitochondrial translation machinery), repressing oxidative phosphorylation in leukemic T cells.\",\n      \"method\": \"Subcellular fractionation; confocal microscopy; proteomics; co-immunoprecipitation; proximity ligation assay; shRNA silencing of CRIF1; mitochondrial respiration assays\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity ligation assay, Co-IP, subcellular fractionation, functional metabolic assays, single lab\",\n      \"pmids\": [\"26210498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Phosphorylation of Y192 in the LCK SH2 domain (promoted by Itk and TSAd) changes LCK substrate specificity by altering SH2 domain-binding partner preference; pY192-LCK preferentially binds regulators of the actin cytoskeleton; Itk and TSAd promote TCR-dependent Y192 phosphorylation.\",\n      \"method\": \"Phosphopeptide arrays; biochemical assays; T cell-cell conjugate assays; Y192 mutants; Itk/TSAd expression in T cells\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphopeptide arrays with biochemical validation, defined upstream kinases, single lab\",\n      \"pmids\": [\"25492967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TAOK3 (a serine/threonine kinase) prevents premature SHP-1-mediated inactivation of LCK following TCR engagement; TAOK3-deficient T cells show enhanced LCK-SHP-1 interaction and rapid TCR signal termination; TAOK3 reconstitution corrects this defect.\",\n      \"method\": \"TAOK3 knockdown in human T cells; LCK-SHP-1 co-immunoprecipitation; TCR signaling assays; IL-2 production; superantigen (LCK-independent) control\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with rescue, Co-IP, functional signaling assays, single lab\",\n      \"pmids\": [\"30373850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Free (coreceptor-unbound) LCK shows higher activating Y394 phosphorylation, higher mobility, and greater kinase activity than CD8α-bound LCK in T hybridoma cells; free LCK mediates higher T cell activation than coreceptor-bound LCK.\",\n      \"method\": \"Single-molecule tracking; phospho-specific immunoblotting; kinase activity assays; T cell activation assays comparing free vs. coreceptor-bound LCK pools\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-molecule imaging and biochemical separation of LCK pools, single lab\",\n      \"pmids\": [\"32571924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CD4-associated LCK activity stimulated by antagonist MHC-peptide complexes acts in a dominant negative mode to override stimulatory signals from agonist ligands; anti-CD4 antibody blocks the antagonist effect, implicating CD4-Lck activation in negative signaling.\",\n      \"method\": \"T cell stimulation with agonist/antagonist peptides; LCK kinase activity assay; CD4 blocking antibody; inositol phospholipid hydrolysis assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase activity assay with functional antagonism readout and blocking antibody, single lab\",\n      \"pmids\": [\"8816805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SOCS1 and SOCS3 expression attenuates Lck kinase activity and reduces STAT5 phosphorylation in Lck-transformed leukemia cells; SOCS1 gene silencing in Lck-transformed LSTRA cells occurs via DNA hypermethylation.\",\n      \"method\": \"Ectopic SOCS1/SOCS3 expression; LCK kinase activity assay; STAT5 phosphorylation; methylation analysis; cell proliferation and apoptosis assays\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with kinase and STAT5 activity readouts, single lab\",\n      \"pmids\": [\"20372794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LCK directly interacts with TRPM8 and phosphorylates it at Y1022; this phosphorylation promotes TRPM8 multimerization and enhances channel current density; phospho-TRPM8-Y1022 inhibits LCK Tyr505 phosphorylation in feedback regulation of LCK activity.\",\n      \"method\": \"Co-immunoprecipitation; in vitro kinase assay; Y1022F mutant; electrophysiology (TRPM8 current); multimerization assay; LCK ubiquitination analysis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with mutagenesis, electrophysiology, single lab\",\n      \"pmids\": [\"35665750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CD45 dephosphorylates LCK at Y394 upon CD44 ligation, dampening the amplitude of Src kinase-dependent signaling and determining the morphological outcome (round vs. elongated spreading) in T cells; CD45-/- cells show sustained Y394 phosphorylation and enhanced PI3K/PLC activation.\",\n      \"method\": \"CD45+/- T cells; CD44 antibody stimulation; confocal microscopy; phospho-Y394 immunoblotting; PI3K/PLC activity assays; actin visualization\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CD45 genetic comparison, phosphosite-specific antibody, signaling pathway readouts, single lab\",\n      \"pmids\": [\"18981123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CD44 directly interacts with LCK (but not FYN) through the membrane-proximal region of the CD44 cytoplasmic domain in a zinc-dependent manner; this zinc-inducible interaction requires the first 13 amino acids of the CD44 cytoplasmic domain and the non-catalytic regions of LCK.\",\n      \"method\": \"Direct binding assay with recombinant purified proteins; zinc chelation (1,10-phenanthroline); progressive deletion mutagenesis; co-immunoprecipitation\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct binding with purified recombinant proteins plus deletion mutagenesis and cell-based Co-IP, single lab\",\n      \"pmids\": [\"20417561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"A kinase-dead Lck chimera (CD4-LckΔkinase) is more active than full-length in an antigen-specific T cell assay; SH2 or SH3 domain mutations moderately reduce activity; combined SH2+SH3 mutations largely abolish activity; indicating distinct, independent contributions of LCK domains to T cell activation.\",\n      \"method\": \"CD4-Lck chimeras with domain deletions/mutations; antigen-specific T cell hybridoma assays; T cell activation readouts\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain dissection chimeras in defined T cell hybridoma, single lab\",\n      \"pmids\": [\"8358792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The unique (specific) domain of LCK is not required for intrinsic kinase activity or ATP binding, but is required for phosphorylation of physiological substrates and for induction of the IL-2 promoter, demonstrating that the unique domain determines substrate specificity.\",\n      \"method\": \"Unique domain deletion mutant; kinase activity assay with physiological and non-physiological substrates; IL-2 promoter reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with deletion mutant plus cell-based functional assay, single lab\",\n      \"pmids\": [\"7531706\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LCK is a Src-family non-receptor tyrosine kinase that is dually acylated (myristoylated at Gly2, palmitoylated at Cys3/Cys5 by DHHC2/DHHC21) for plasma membrane and lipid raft targeting; it associates with CD4 and CD8 co-receptors via a zinc clasp and with coreceptor-free TCR components (CD3ε RK motif, CD3ε BRS/Unique-domain ionic interaction, CD146) to initiate TCR signaling by phosphorylating ITAM tyrosines; its activity is positively regulated by activating autophosphorylation at Tyr394 (also targeted by UBR2-mediated K63-ubiquitination and trans-phosphorylation), negatively regulated by Csk-dependent phosphorylation at Tyr505 (reversed by CD45), and further modulated by phosphorylation of SH2-domain Tyr192 (which controls CD45 access and downstream partner specificity), while Cbl ubiquitin ligase and DUSP22/JKAP phosphatase provide negative feedback; a significant fraction (~40%) of LCK is constitutively active in resting T cells and its conformational state (open/active vs. closed/inactive) controls nanoscale clustering and substrate access; LCK additionally bridges phospho-ZAP70 (via SH2) to LAT (via SH3/proline-rich motif) to orchestrate downstream adaptor phosphorylation, phosphorylates substrates including PKCtheta (Y90), STAT3, FOXP3 (Y342), WASH (Y141), and TRPM8 (Y1022), and controls Th2 differentiation, CD4/CD8 lineage commitment, RICD, and Schwann cell myelination.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"LCK is a Src-family non-receptor tyrosine kinase that initiates and sets the threshold of T cell receptor (TCR) signaling by phosphorylating proximal substrates at the plasma membrane and immunological synapse [#0, #9]. Membrane and lipid-raft targeting depend on N-terminal S-acylation: palmitoylation at Cys3/Cys5 is required for plasma-membrane localization and TCR signal reconstitution, with DHHC2 and the Fas-inducible DHHC21 acting as acyltransferases [#0, #18, #19]. LCK is recruited to its activating context through multiple membrane anchors—a zinc-clasp association of its N-terminus with CD4 and CD8 coreceptor tails [#1], an electrostatic interaction between the CD3\\u03b5 basic-residue-rich sequence and the LCK Unique domain plus a ligand-exposed CD3\\u03b5 RK motif binding the SH3 domain for coreceptor-free recruitment [#13, #14], and SH2-domain binding to anionic membrane lipids that is needed for engagement of the TCR \\u03b6 chain [#32]. Catalytic output is governed by a conformational switch built on opposing tyrosine phosphorylations: activating autophosphorylation at Tyr394 is indispensable for activity and drives an open conformation that promotes nanoscale clustering of phospho-TCRs while excluding CD45 [#2, #29, #12], whereas Csk-dependent and FAK-recruited Csk-mediated phosphorylation of the inhibitory Tyr505 closes the kinase, a state reversed by CD45 to license thymocyte development [#3, #38, #6, #49]. Phosphorylation of SH2-domain Tyr192 by Itk/TSAd both blocks CD45 access and redirects substrate/partner specificity toward actin regulators [#21, #43]. A substantial pool of LCK is constitutively active in resting T cells, maintained by the HSP90\\u2013CDC37 chaperone system that protects open/active LCK from ubiquitin-dependent degradation [#8, #20]. Negative feedback is imposed by the Cbl E3 ligase, which ubiquitinates active LCK for degradation via the SH3 domain, and by the phosphatases DUSP22/JKAP and SHP-1 acting on Tyr394; conversely UBR2-mediated K63-ubiquitination promotes Tyr394 activation [#5, #10, #37, #44]. Functionally, LCK bridges phospho-ZAP70 (through its SH2 domain) to LAT (through its SH3 domain) to coordinate downstream adaptor phosphorylation, sets the quantitative signal that directs CD4/CD8 lineage commitment, and shapes Th2 differentiation via GATA-3/T-bet [#9, #23, #24]. Beyond the TCR, LCK phosphorylates a range of substrates including PKC\\u03b8 (Tyr90), STAT3, FOXP3 (Tyr342), WASH (Tyr141) for NK cytotoxicity, and the TRPM8 channel (Tyr1022), and mediates \\u03b21-integrin/laminin signaling required for Schwann cell myelination [#17, #25, #30, #40, #48, #26].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Established that LCK's non-catalytic SH2/SH3 domains and adaptor functions, not kinase activity alone, drive T cell activation, reframing LCK as more than a catalytic enzyme.\",\n      \"evidence\": \"CD4-Lck domain-deletion chimeras in antigen-specific T cell hybridoma assays\",\n      \"pmids\": [\"8358792\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define direct binding partners of each domain\", \"Chimera context may not reflect native LCK regulation\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined the Unique domain as the determinant of physiological substrate specificity, separating intrinsic catalysis from biological output.\",\n      \"evidence\": \"Unique-domain deletion mutant with kinase assays on physiological vs non-physiological substrates and IL-2 promoter reporter\",\n      \"pmids\": [\"7531706\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which the Unique domain selects substrates not resolved\", \"Membrane/partner context contributions not isolated\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Identified Tyr394 as the activating autophosphorylation site and provided early evidence for a trans-activating kinase, framing how LCK is switched on.\",\n      \"evidence\": \"H2O2 stimulation of cells with Y394F/kinase-dead Lck mutants and kinase activity readouts\",\n      \"pmids\": [\"7538674\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the trans-activating kinase not established\", \"Physiological (non-oxidative) trigger not defined here\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrated LCK self-association via SH2/SH3 domains, providing a mechanism for trans-activation between LCK molecules.\",\n      \"evidence\": \"CD4-Lck chimeras and GST-SH2/SH3 pull-downs in Lck-positive vs Lck-negative T cells\",\n      \"pmids\": [\"8798782\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and physiological relevance of dimers unclear\", \"Whether dimerization is regulated during signaling not addressed\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Showed that N-terminal palmitoylation is essential for membrane targeting and TCR signaling, separating catalytic competence from spatial positioning.\",\n      \"evidence\": \"Acylation-mutant LCK reconstituted in LCK-negative T cells with Ca2+ flux, CD69/NFAT and ZAP-70 association readouts\",\n      \"pmids\": [\"9305640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Acyltransferase responsible not identified at this stage\", \"Dynamics of palmitoylation not addressed\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Established CD45 dephosphorylation of inhibitory Tyr505 as the in vivo activating step required for thymocyte development.\",\n      \"evidence\": \"Genetic epistasis with CD45-/- mice rescued by LckY505F transgene\",\n      \"pmids\": [\"10330160\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CD45 access to LCK is spatially controlled not resolved here\", \"Other CD45 substrates contribution not isolated\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Connected LCK to downstream transcriptional and lipid-signaling outputs by showing it phosphorylates STAT3 and gates SHP-1/PI3K regulation.\",\n      \"evidence\": \"Baculovirus reconstitution with EMSA for STAT3; Co-IP and PI3K activity assays for SHP-1/p85\",\n      \"pmids\": [\"10617281\", \"10488096\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect phosphorylation in vivo not fully separated\", \"Quantitative contribution to physiological signaling unclear\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Showed that the quantitative level of LCK activity instructs the CD4/CD8 lineage decision, establishing LCK signal strength as a developmental rheostat.\",\n      \"evidence\": \"Reciprocal dominant-negative and constitutively active Lck transgenic mice on TCR-transgenic backgrounds\",\n      \"pmids\": [\"10755618\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular threshold sensors downstream of LCK not defined\", \"How signal duration vs amplitude is read not resolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified PKC\\u03b8 Tyr90 as a direct LCK substrate linking LCK to NFAT activation and proliferation.\",\n      \"evidence\": \"In vitro kinase assay, Co-IP, Y90F mutagenesis and T cell reporter assays\",\n      \"pmids\": [\"10652356\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of LCK-PKC\\u03b8 docking not defined\", \"In vivo requirement not tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined coreceptor and costimulatory control of LCK activation, showing CD4 recruits and CD28 sustains active LCK, and that Cbl provides ubiquitin-dependent negative feedback.\",\n      \"evidence\": \"Phosphospecific antibodies with blocking antibodies; Co-IP and Cbl-/- T cell line analysis with SH3 mutants\",\n      \"pmids\": [\"11828322\", \"11904433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CD28 mechanistically sustains autophosphorylation not resolved\", \"Cbl recognition determinants on LCK beyond SH3 contact unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Provided the structural basis for coreceptor selectivity by solving the zinc-clasp that folds CD4/CD8 tails with the LCK N-terminus.\",\n      \"evidence\": \"Solution NMR structures of CD4-Lck-Zn2+ and CD8\\u03b1-Lck-Zn2+ ternary complexes\",\n      \"pmids\": [\"14500983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of clasp assembly during synapse formation not captured\", \"Regulation of zinc availability not addressed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Linked LCK conformation to its turnover, showing open/active LCK is degraded unless protected by HSP90, independent of kinase activity.\",\n      \"evidence\": \"Conformational and kinase mutants in COS-7 with geldanamycin and ubiquitination assays\",\n      \"pmids\": [\"15199125\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase mediating conformation-dependent degradation not identified here\", \"Quantitative stability difference in primary cells not measured\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Revealed that a constitutively active LCK pool pre-exists in resting T cells and sets TCR-\\u03b6 phosphorylation capacity, shifting the model from de novo activation to pre-poised signaling.\",\n      \"evidence\": \"Phosphospecific flow cytometry and biochemical fractionation in primary cells with HSP90 inhibition\",\n      \"pmids\": [\"20541955\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How active LCK is restrained from constitutive signaling not fully resolved\", \"Spatial segregation from substrate at rest not defined here\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed CD45 dephosphorylates the activating Tyr394 in additional contexts (CD44 ligation), establishing CD45 as both an activator and a dampener depending on the targeted tyrosine.\",\n      \"evidence\": \"CD45+/- T cells with CD44 stimulation, phospho-Y394 blotting and PI3K/PLC readouts\",\n      \"pmids\": [\"18981123\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How CD45 selects Y394 vs Y505 not mechanistically resolved\", \"Generality across receptor contexts unclear\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated that LCK conformation directly controls nanoscale clustering, producing CD45-excluding, phospho-TCR-enriched domains that spatially favor signaling.\",\n      \"evidence\": \"Super-resolution PALM/STORM imaging with conformation-state mutants\",\n      \"pmids\": [\"23202272\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger that shifts conformation in situ not defined\", \"Cluster composition beyond TCR/CD45 not enumerated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended LCK function beyond lymphocytes, showing it transduces laminin/\\u03b21-integrin signals required for Schwann cell myelination.\",\n      \"evidence\": \"LCK inhibition, \\u03b21-integrin siRNA, Lck-/- mice and Rac-GTP/paxillin pathway readouts\",\n      \"pmids\": [\"23715271\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct LCK substrates in the Schwann cell pathway not all defined\", \"Relationship to TCR-context regulation unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified FAK-recruited Csk as a TCR-induced brake on LCK, adding a spatial mechanism for inhibitory Tyr505 phosphorylation.\",\n      \"evidence\": \"FAK suppression in human T cells with Csk recruitment and LCK phosphorylation analysis\",\n      \"pmids\": [\"24227778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct FAK-Csk-LCK assembly stoichiometry not resolved\", \"Distinction between LCK and Fyn effects not fully separated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established DUSP22/JKAP as a direct phosphatase inactivating LCK at Tyr394, providing a genetic brake whose loss promotes autoimmunity.\",\n      \"evidence\": \"In vitro phosphatase assay and JKAP knockout mice with EAE model\",\n      \"pmids\": [\"24714587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial regulation of JKAP-LCK encounter not defined\", \"Relationship to other Y394 phosphatases not ranked\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed Tyr192 phosphorylation rewires LCK SH2-domain partner preference toward actin regulators, linking a post-translational mark to substrate-selectivity switching.\",\n      \"evidence\": \"Phosphopeptide arrays and T cell conjugate assays with Itk/TSAd as upstream kinases\",\n      \"pmids\": [\"25492967\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Full pY192 interactome not mapped\", \"In vivo consequence of altered specificity not established here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Expanded LCK substrate repertoire to FOXP3 (Tyr342) and to receptor-localized activation via SAP at NTB-A, linking LCK to Treg/invasion programs and restimulation-induced cell death.\",\n      \"evidence\": \"In vitro kinase assays with Y342F mutant and invasion assays; Co-IP with NTB-A ITSM mutants and RICD assays in XLP patient cells\",\n      \"pmids\": [\"24155921\", \"24688028\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological setting of FOXP3 phosphorylation by LCK unclear\", \"Direct vs SAP-bridged LCK recruitment at NTB-A not fully separated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Resolved the Tyr192 mechanism as a gate on CD45 access, integrating SH2-domain phosphorylation with the activation switch and thymocyte development.\",\n      \"evidence\": \"Y192 mutants with Co-IP, phospho-blotting and retrogenic mouse thymocyte assays\",\n      \"pmids\": [\"28735895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetics of pY192/CD45 competition in vivo not measured\", \"Coordination with pY394/pY505 cycling not fully integrated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the CD3\\u03b5 BRS-LCK Unique-domain ionic interaction as an antigen-unlocked targeting mechanism for coreceptor-independent TCR phosphorylation.\",\n      \"evidence\": \"TCR reconstitution with electrostatic mapping, mutagenesis and phosphorylation assays\",\n      \"pmids\": [\"28659468\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How antigen mechanically unlocks BRS not resolved\", \"Quantitative contribution vs coreceptor route unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined SH2-domain lipid binding and Rab11-FIP3-controlled endosomal delivery as spatial determinants of LCK function at the synapse.\",\n      \"evidence\": \"NMR/membrane binding assays with lipid-binding mutants; FIP3 gain/loss-of-function with imaging and signaling readouts\",\n      \"pmids\": [\"27334919\", \"28235866\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interplay between lipid binding and phospho-Tyr docking not resolved\", \"Trafficking machinery beyond FIP3 not mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Used genetic code expansion to prove Tyr394 autophosphorylation is indispensable and that LCK self-opens, with coreceptors enhancing activity, providing a quantitative live-cell view of the switch.\",\n      \"evidence\": \"Photocaged active-site lysine LCK with FRET biosensor imaging and live-cell kinetics, CD4/CD8 cotransfection\",\n      \"pmids\": [\"29083415\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of measured kinetics not tested\", \"Coupling to clustering not directly imaged here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined the bridging function of LCK between phospho-ZAP70 and LAT, explaining how proximal phosphorylation is spatially coordinated.\",\n      \"evidence\": \"Co-IP, phosphoproteomics, LAT proline-rich-motif mutants and retrogenic mice\",\n      \"pmids\": [\"29915297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the ZAP70-LCK-LAT assembly not defined\", \"Dynamics of bridge formation during signaling unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified TAOK3 as protecting LCK from premature SHP-1 inactivation and ICOS transmembrane-domain-driven LCK recruitment for costimulation, broadening LCK's receptor inputs.\",\n      \"evidence\": \"TAOK3 knockdown with LCK-SHP-1 Co-IP; ICOS TMD-swap mutants with PI3K recruitment and calcium flux\",\n      \"pmids\": [\"30373850\", \"30523347\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of TAOK3 control over SHP-1 access not resolved\", \"Direct vs indirect LCK-ICOS contact not structurally defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a ligand-exposed CD3\\u03b5 RK motif binding the LCK SH3 domain and showed free LCK is more active than coreceptor-bound LCK, refining the model of how LCK is positioned and activated at the TCR.\",\n      \"evidence\": \"Biochemical binding/mutagenesis with thymocyte and CAR-T assays; single-molecule tracking comparing free vs CD8\\u03b1-bound LCK pools\",\n      \"pmids\": [\"32690949\", \"32571924\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Balance between coreceptor-bound and free LCK in vivo not quantified\", \"How the two recruitment modes are coordinated unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified CD146 as a coreceptor-free LCK SH3 partner and LAG3 as a coreceptor-LCK dissociator via local pH, mechanistically explaining both LCK recruitment and inhibitory checkpoint disengagement.\",\n      \"evidence\": \"Co-IP and direct binding with CD146 knockout mice; LAG3 cytoplasmic mutants with pH-sensor imaging and CD4/CD8-LCK dissociation measurement\",\n      \"pmids\": [\"34491908\", \"35437325\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological balance between CD146 and other coreceptor-free routes unclear\", \"Generality of pH-driven dissociation beyond LAG3 unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended LCK substrates to the TRPM8 channel (Tyr1022) with reciprocal feedback on LCK Tyr505, and identified disulfiram as a covalent LCK activator, opening pharmacological tuning of LCK.\",\n      \"evidence\": \"In vitro kinase assay/electrophysiology for TRPM8; covalent binding and tumor models for disulfiram\",\n      \"pmids\": [\"35665750\", \"35638332\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological context of LCK-TRPM8 signaling unclear\", \"Selectivity of disulfiram for LCK over other targets not fully established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined UBR2-mediated K63-ubiquitination at Lys99/Lys276 as a positive driver of LCK Tyr394 activation, counter-regulated by DUSP22, with disease relevance in SLE T cells.\",\n      \"evidence\": \"scRNA-seq, K63-linkage ubiquitination biochemistry, UBR2 knockout, DUSP22 phosphatase assays and SLE patient samples\",\n      \"pmids\": [\"38225265\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How K63-ubiquitin promotes Y394 phosphorylation mechanistically not resolved\", \"Interplay with Cbl K48-degradation pathway not integrated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple, overlapping recruitment routes (coreceptor zinc-clasp, CD3\\u03b5 BRS/RK, CD146, lipid binding) and the layered post-translational controls (Y394/Y505/Y192, K63/K48 ubiquitination, palmitoylation) are quantitatively integrated to set a single activation threshold in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No unified quantitative model linking conformation, ubiquitination, localization and clustering\", \"Relative weighting of free vs coreceptor-bound LCK pools in physiological responses unknown\", \"Full substrate repertoire and its context-dependence incompletely mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 9, 17, 25, 30, 40, 48]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [2, 3, 29]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [32]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 9, 14]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [16, 47]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 12, 14, 32]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [34]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [42]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 9, 13, 23]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 26, 39]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6, 23, 26]}\n    ],\n    \"complexes\": [\n      \"ZAP70-LCK-LAT proximal signaling assembly\",\n      \"CD4/CD8-LCK zinc-clasp coreceptor complex\",\n      \"HSP90-CDC37 chaperone-LCK complex\",\n      \"TCR-linked HSP90-LCK-FYN-glucocorticoid receptor complex\"\n    ],\n    \"partners\": [\n      \"CD4\",\n      \"CD8\",\n      \"CD3E\",\n      \"ZAP70\",\n      \"LAT\",\n      \"CD45\",\n      \"CBL\",\n      \"DUSP22\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}