{"gene":"S100A6","run_date":"2026-06-10T07:46:28","timeline":{"discoveries":[{"year":2007,"finding":"S100A6 interacts specifically with the C1 and C2 extracellular immunoglobulin domains of RAGE (distinct from S100B which binds V and C1 domains), and extracellular S100A6 triggers apoptosis in SH-SY5Y neuroblastoma cells via activation of JNK (not PI3K/AKT or NF-κB), in a RAGE-dependent manner.","method":"In vitro binding assay with individual RAGE domain constructs, cell-based assay with ROS measurement, pathway inhibitor studies, and RAGE-blocking experiments in SH-SY5Y cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain-specific binding assays and cell-based pathway analysis in single lab with multiple orthogonal approaches","pmids":["17726019"],"is_preprint":false},{"year":2008,"finding":"S100A6 interacts with p53 in a calcium-dependent manner (shown by affinity chromatography and co-immunoprecipitation), enhances p53 transcriptional activity and nuclear accumulation under stress without affecting p53 DNA binding (by EMSA), and its presence increases cell susceptibility to hydrogen peroxide-induced apoptosis.","method":"Affinity chromatography, co-immunoprecipitation, EMSA, siRNA knockdown in HEp-2 cells, luciferase reporter assay, immunofluorescence for p53 localization","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal binding assays and multiple functional readouts in single lab","pmids":["18765292"],"is_preprint":false},{"year":2008,"finding":"S100A6 is induced by TNF-α via an NF-κB–dependent mechanism (p65 binds an NF-κB site at -460/-451 in the S100A6 promoter as shown by EMSA and ChIP); S100A6 limits TNF-α-induced cardiomyocyte apoptosis by interfering with p53 phosphorylation.","method":"Luciferase reporter assay, EMSA, chromatin immunoprecipitation (ChIP), siRNA knockdown, gene transfer overexpression in rat neonatal cardiac myocytes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (promoter deletion, EMSA, ChIP, siRNA, overexpression) in single rigorous study","pmids":["18753141"],"is_preprint":false},{"year":2000,"finding":"S100A6 and S100A11 are specific target proteins for S100B; Ca2+/Zn2+ stabilizes S100B–S100A6 heterocomplexes; the C-terminal residues Phe87/Phe88 of S100B are required for interaction with S100A6 (but not for S100B homodimerization); interaction confirmed in U373 astrocytoma cells by co-immunoprecipitation.","method":"Yeast two-hybrid screen, co-immunoprecipitation, site-directed mutagenesis of S100B (Phe87/88), deletion analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — yeast two-hybrid discovery plus mutagenesis and co-IP validation","pmids":["10913138"],"is_preprint":false},{"year":2003,"finding":"S100A6 binds Sgt1 (yeast homologue of CacyBP/SIP) in a calcium-regulated manner via Sgt1's C-terminal 71 residues; S100A6 does not affect Skp1–Sgt1 binding; S100A6 inhibits casein kinase II–mediated phosphorylation of the S100A6-binding domain of Sgt1; interaction confirmed by co-immunoprecipitation from HEp-2 cell extracts.","method":"Affinity chromatography, chemical cross-linking, co-immunoprecipitation, kinase phosphorylation assay with CK II","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple biochemical methods (affinity chromatography, cross-linking, co-IP, kinase assay) with domain-mapping and functional endpoint","pmids":["12746458"],"is_preprint":false},{"year":2000,"finding":"The S100A6-binding domain of CacyBP (residues 178–229) is necessary and sufficient for calcium-dependent binding to S100A6 with a Kd ~1 μM; NMR analysis revealed that CacyBP binding occurs at a discrete site on 15N-labeled S100A6.","method":"Limited proteolysis, deletion mutagenesis, fluorescence spectroscopy (Kd determination), NMR chemical shift perturbation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure plus mutagenesis and quantitative binding assays in one rigorous study","pmids":["10884380"],"is_preprint":false},{"year":2008,"finding":"S100A6 binds the TPR domain of Hop (Hsp70/Hsp90-organizing protein) and of kinesin light chain (KLC) in a Ca2+-dependent manner; this binding inhibits Hop–Hsp70 and Hop–Hsp90 interactions and displaces JIP-1 from KLC in vitro and in ionomycin-stimulated Cos-7 cells.","method":"GST pulldown, co-immunoprecipitation, in vitro binding inhibition assays, ionomycin stimulation of Cos-7 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — GST pulldown plus reciprocal co-IP plus cell stimulation experiments across multiple target proteins","pmids":["18669640"],"is_preprint":false},{"year":2009,"finding":"S100A6 binds annexin 2 in pancreatic cancer cells (confirmed by reciprocal immunoprecipitation); S100A6 promotes membrane localization of annexin 2; siRNA depletion of S100A6 reduces membrane annexin 2 levels and markedly reduces pancreatic cancer cell motility.","method":"Immunoprecipitation + 2D-gel electrophoresis + mass spectrometry, reciprocal co-immunoprecipitation, co-immunofluorescence, siRNA knockdown, Boyden chamber and wound healing motility assays","journal":"British journal of cancer","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomic screen, reciprocal co-IP, functional siRNA knockdown with defined readout","pmids":["19724273"],"is_preprint":false},{"year":1994,"finding":"Recombinant S100A6 (CACY) binds 2 Ca2+ per monomer with low affinity (K0.5 = 0.32 mM), shows positive cooperativity (nH = 1.33), and Ca2+ binding induces a conformational change shifting Tyr to a less polar environment; Mg2+ does not affect Ca2+ binding or fluorescence properties; S100A6 forms homodimers but not heterodimers with CAPL in vitro.","method":"Flow dialysis calcium binding assay, fluorescence spectroscopy, UV difference spectroscopy, gel filtration/analytical ultracentrifugation","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with quantitative biophysical measurements and multiple methods","pmids":["8204608"],"is_preprint":false},{"year":1996,"finding":"S100A6 (calcyclin) interacts with a novel 30 kDa target protein (p30, later identified as CacyBP) in a Ca2+-dependent manner with higher affinity than annexin II or GAPDH; p30 was purified from Ehrlich ascites tumor cells and found in mouse brain and spleen.","method":"Gel overlay with 125I-labeled calcyclin, Ca2+-dependent affinity chromatography, Phenyl-Sepharose and CM-cellulose chromatography, partial amino acid sequencing","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — radiolabeled overlay plus affinity purification in single study; CacyBP identity confirmed in later work","pmids":["8973570"],"is_preprint":false},{"year":1991,"finding":"S100A6 (calcyclin/2A9 product) purified from rabbit lung binds 2 Ca2+ per mole, does not activate calmodulin-dependent enzymes (CaM kinase II, MLCK, phosphodiesterase), and interacts in a Ca2+-dependent manner with a 50 kDa cytosolic binding protein present in lung, intestine, and spleen.","method":"Ca2+-dependent affinity chromatography (W-77 Sepharose), UV difference spectroscopy, equilibrium dialysis, calmodulin-dependent enzyme activity assays","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro biochemical reconstitution; negative result for CaM-dependent enzyme activation is explicit","pmids":["1898017"],"is_preprint":false},{"year":2002,"finding":"S100A6 translocation in endothelial cells in response to increased intracellular calcium is dependent on actin stress fibers (distinct from S100A13 which uses the Golgi-ER pathway), implicating actin cytoskeleton in S100A6 intracellular trafficking.","method":"Live cell imaging/immunofluorescence of S100A6 translocation, cytoskeletal disruption experiments, comparison with S100A13 in angiotensin II–stimulated endothelial cells","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiments with pathway perturbation; single lab, single publication","pmids":["12118070"],"is_preprint":false},{"year":2003,"finding":"Antisense-mediated reduction of S100A6 in pulmonary fibroblasts inhibits serum- and mechanical strain-induced cell proliferation, causes flattened cell morphology, and disrupts tropomyosin-labeled microfilament organization without reducing tropomyosin protein levels.","method":"Antisense RNA stable expression, proliferation assay, immunofluorescence of tropomyosin/microfilaments, cell morphology analysis","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with specific cytoskeletal and proliferative readouts; single lab","pmids":["12577318"],"is_preprint":false},{"year":2004,"finding":"The S100A6 gene promoter contains a functional antioxidant response element (ARE) at -290/-281 that overlaps an E-box; oxidative stress agents (cadmium ions) activate S100A6 transcription via this ARE; Nrf2 transcription factor binds to this ARE region as shown by DNA affinity chromatography and EMSA; mutation of ARE inhibits cadmium-stimulated promoter activity.","method":"Luciferase reporter assay, RT-PCR, Northern blot, EMSA, site-directed mutation of ARE, DNA affinity chromatography + Western blot for Nrf2","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (mutagenesis, EMSA, affinity chromatography, reporter assay) converging on Nrf2/ARE mechanism","pmids":["15878395"],"is_preprint":false},{"year":2010,"finding":"S100A6 deficiency (stable siRNA knockdown) in NIH 3T3 fibroblasts causes G0/G1 cell cycle arrest unresponsive to serum, senescence-like morphological and biochemical changes (elevated β-galactosidase, gelatinase activity), disrupted actin cytoskeleton, and impaired cell adhesion and migration.","method":"Stable siRNA expression, cell cycle analysis by flow cytometry, β-galactosidase senescence assay, gelatinase assay, phalloidin staining, adhesion and migration assays","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined KO phenotype with multiple orthogonal readouts; single lab","pmids":["20013795"],"is_preprint":false},{"year":2012,"finding":"S100A6 depletion by RNAi in primary human endothelial cells causes G2/M cell cycle arrest, decreases CDK1 and phospho-CDK1 levels, reduces cyclin A1 (CCNA1) and cyclin B (CCNB1) gene expression, and induces β-galactosidase expression (senescence marker).","method":"RNAi knockdown, flow cytometry cell cycle analysis, Western blotting, qRT-PCR, β-galactosidase staining","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined KO phenotype with multiple molecular endpoints; single lab","pmids":["23095053"],"is_preprint":false},{"year":2016,"finding":"S100A6 suppresses antiproliferative STAT1 signaling in endothelial cells; S100A6 silencing combined with VEGFA stimulation revealed interferon-inducible transmembrane protein 1 and PIAS proteins as key components linking S100A6 to STAT1 suppression.","method":"siRNA knockdown in human endothelial cells, gene expression time-series analysis, bioinformatic pathway modeling, experimental validation of STAT1 pathway components","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic transcriptomics plus experimental validation; single lab","pmids":["27386938"],"is_preprint":false},{"year":2012,"finding":"S100A6 forms amyloid fibrils under acidic conditions; Ca2+ inhibits fibrillation (promoting anti-parallel β-sheet conformations that repress fibril formation) by a mechanism reversible upon chelation; S100A6 oligomers (not fibrils) are cytotoxic (reducing cell viability ~40%); native S100A6 seeds SOD1 aggregation, shortening its nucleation phase.","method":"Thioflavin-T kinetics, electron microscopy, FT-IR spectroscopy, cell viability assay, seeding aggregation kinetics with SOD1, computational aggregation prediction","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple biophysical and biochemical methods with mechanistic controls (chelation reversal, Ca2+ dose) in single rigorous study","pmids":["23076148"],"is_preprint":false},{"year":2017,"finding":"S100A6 overexpression in rat neonatal cardiomyocytes improves calcium transients and protects against hypoxia-reoxygenation-induced apoptosis via enhanced calcineurin activity; in vivo S100A6 gene therapy (via ultrasound-targeted microbubble destruction) reduced infarct size and improved left ventricular systolic function after ischemia-reperfusion.","method":"S100A6 overexpression and siRNA knockdown in cardiomyocytes, calcium transient imaging, calcineurin activity assay, in vivo gene delivery + coronary ligation/reperfusion model in Fischer-344 rats","journal":"Journal of the American Heart Association","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro functional assay plus in vivo model; single lab, calcineurin mechanism identified but not deeply dissected","pmids":["28174168"],"is_preprint":false},{"year":2019,"finding":"Extracellular S100A6 competes with zinc ions for binding to Aβ, reducing amyloid plaque burden in APP/PS1 mouse brain sections; exogenous S100A6 decreased plaque-associated zinc content and protected COS-7 cells against zinc toxicity.","method":"In vitro incubation of brain sections with recombinant S100A6, co-culture with S100A6-expressing cells, Aβ plaque quantification, zinc chelator (clioquinol) control experiments, cell viability assay","journal":"Aging and disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ex vivo tissue and in vitro cell experiments with biochemical controls; single lab","pmids":["31440382"],"is_preprint":false},{"year":2020,"finding":"S100A6 knockout in mouse hematopoietic stem cells (HSCs) reduces self-renewal and regenerative capacity, decreases phospho-Akt and Hsp90 levels, impairs mitochondrial respiratory capacity and mitochondrial calcium buffering; Akt activator SC79 rescues intracellular/mitochondrial calcium levels and colony-forming and Hsp90 activity.","method":"S100A6 KO mouse model, flow cytometry, transcriptomics, proteomics, Seahorse mitochondrial assay, calcium imaging, pharmacological Akt activation rescue experiments","journal":"Leukemia","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse with transcriptomics, proteomics, and multiple functional readouts plus pharmacological rescue in single comprehensive study","pmids":["32555370"],"is_preprint":false},{"year":2013,"finding":"S100A6 overexpression in HCC cells causes down-regulation of E-cadherin, nuclear accumulation of β-catenin, and promotes proliferation and migration via activation of the PI3K/AKT pathway; intracellular (not extracellular) S100A6 is sufficient to rescue proliferation and migration defects after S100A6 silencing.","method":"siRNA knockdown, recombinant S100A6 with cell-penetrating peptide re-expression, Western blotting for E-cadherin/β-catenin, PI3K inhibitor (LY294002) treatment, proliferation and migration assays","journal":"Journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — orthogonal gain/loss-of-function with pathway inhibitor; single lab","pmids":["24281831"],"is_preprint":false},{"year":2013,"finding":"S100A6 promotes colorectal carcinoma cell proliferation via ERK pathway and migration via p38 MAPK pathway; ERK inhibitor partially attenuates S100A6-induced proliferation and p38 inhibitor suppresses S100A6-induced migration.","method":"Adenoviral overexpression, recombinant S100A6 protein treatment, RNAi knockdown, kinase inhibitors (ERK, p38), in vitro proliferation/migration assays, nude mouse xenograft","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple gain/loss-of-function approaches with pathway-specific inhibitors; single lab","pmids":["24378749"],"is_preprint":false},{"year":2022,"finding":"Liver-derived S100A6 (a hepatokine) inhibits glucose-stimulated insulin secretion (GSIS) from β cells via activation of RAGE and diminution of mitochondrial respiration; hepatic S100A6 transcription is driven by ChREBP; ectopic hepatic ChREBP overexpression suppresses GSIS in an S100A6-dependent manner; depletion of hepatic S100A6 improves GSIS and glycemia in mice.","method":"High-fat diet mouse model, hepatic S100A6 depletion (siRNA/KO), GSIS assay, RAGE pathway assay, Seahorse mitochondrial respiration, ChREBP overexpression in liver, human NAFLD patient serum measurements","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo and in vitro approaches (KO, overexpression, RAGE pathway, mitochondrial assay, human validation) in single comprehensive study","pmids":["35899967"],"is_preprint":false},{"year":2024,"finding":"Secreted S100A6 from tumor cells promotes lymphangiogenesis in human lymphatic endothelial cells (HLECs) by upregulating VEGF-D expression and secretion via the RAGE/NF-κB/VEGF-D signaling pathway, thereby driving lymph node metastasis of liver cancer.","method":"Single-cell RNA-seq analysis, HLEC co-culture experiments, S100A6 overexpression/knockdown, RAGE/NF-κB pathway inhibition, VEGF-D ELISA, in vivo lymphatic metastasis model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro mechanistic pathway studies and in vivo model; single lab","pmids":["38350547"],"is_preprint":false},{"year":1991,"finding":"S100A6 (2A9/calcyclin) mRNA is low in quiescent vascular smooth muscle cells and increases 2–4 h after serum re-addition (cell cycle entry); this regulation occurs post-transcriptionally as no change in transcription rate was detected by nuclear run-off assay.","method":"Northern blotting, serum deprivation/re-addition synchronization, nuclear run-off transcription assay","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — explicit nuclear run-off assay establishes post-transcriptional regulation; single lab","pmids":["1757477"],"is_preprint":false},{"year":2021,"finding":"c-Myc directly binds the S100A6 promoter to activate S100A6 transcription in keratinocytes; high-glucose-induced c-Myc upregulates S100A6 to inhibit HaCaT keratinocyte differentiation via WNT/β-catenin pathway; knockdown of S100A6 rescues the differentiation dysfunction caused by c-Myc overexpression or high glucose.","method":"ChIP assay, luciferase reporter assay, siRNA knockdown, overexpression, Western blotting for differentiation markers, organotypic culture","journal":"Frontiers in endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-confirmed direct promoter binding plus rescue experiments; single lab","pmids":["34060533"],"is_preprint":false},{"year":2012,"finding":"S100A6 interaction with wild-type CacyBP/SIP (but not with a truncated mutant lacking the S100-binding domain) negatively regulates CacyBP/SIP-mediated inhibition of gastric cancer cell proliferation and tumorigenesis; S100A6 binding to CacyBP/SIP modulates β-catenin protein expression and Tcf/LEF transcriptional activation.","method":"Co-immunoprecipitation of endogenous S100A6 with CacyBP/SIP, truncation mutant expression, MTT/FACS/clonogenic assay, tumor xenograft","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with domain deletion mutant and functional readouts; single lab","pmids":["22295074"],"is_preprint":false},{"year":2014,"finding":"S100A6 overexpression in keratinocytes suppresses loricrin expression, accelerates proliferation, and blocks epidermal differentiation in organotypic culture; S100A6 expression is regulated during differentiation via ΔNp63 and retinoic acid (not by DNA methylation) as shown by bisulfite treatment, luciferase assay, and ChIP.","method":"Stable knockdown and overexpression in HaCaT cells, organotypic (3D) culture, bisulfite sequencing, luciferase reporter, ChIP for ΔNp63, retinoic acid treatment","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — 2D and 3D functional models plus mechanistic epigenetic/transcriptional dissection; single lab","pmids":["25450463"],"is_preprint":false},{"year":2019,"finding":"S100A6 promotes B lymphocyte infiltration through the blood-brain barrier endothelial layer; recombinant S100A6 protein treatment of an in vitro transendothelial migration model significantly increased B cell penetration, partially recapitulating the effect of autoimmune encephalitis serum.","method":"In vitro leukocyte transendothelial migration assay, recombinant S100A6 protein treatment, genome-wide DNA methylation assay, qPCR","journal":"Frontiers in genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single assay with recombinant protein; no receptor/pathway identified for the BBB penetration effect","pmids":["31850060"],"is_preprint":false}],"current_model":"S100A6 (calcyclin) is a dimeric, Ca2+- and Zn2+-binding EF-hand protein that undergoes Ca2+-induced conformational changes exposing hydrophobic surfaces, enabling it to interact with diverse intracellular targets—including p53 (enhancing nuclear accumulation and transcriptional activity), CacyBP/SIP (regulating β-catenin ubiquitination and cell proliferation), Sgt1 (inhibiting its CK II-mediated phosphorylation), Hop/KLC (disrupting chaperone and cargo-adaptor complexes in a Ca2+-dependent manner), and annexin 2 (promoting cancer cell motility)—while extracellularly it signals through RAGE (C1/C2 domains) to activate JNK and apoptosis, acts as a hepatokine that impairs β-cell insulin secretion via RAGE/mitochondrial respiration, competes for zinc to reduce Aβ aggregation, and promotes lymphangiogenesis via RAGE/NF-κB/VEGF-D; intracellularly S100A6 supports cell cycle progression (regulating CDK1 levels and suppressing STAT1 signaling), cytoskeletal dynamics via actin stress fibers, and HSC self-renewal through the Akt–Hsp90–mitochondrial calcium axis, while its transcription is regulated by NF-κB (TNF-α stimulus), Nrf2/ARE (oxidative stress), c-Myc, and ΔNp63."},"narrative":{"mechanistic_narrative":"S100A6 (calcyclin) is a small, homodimeric EF-hand protein that binds two Ca2+ per monomer with low affinity and positive cooperativity, undergoing a Ca2+-induced conformational change that shifts buried aromatic residues into a less polar environment and creates target-binding surfaces, while remaining functionally distinct from calmodulin (it does not activate calmodulin-dependent enzymes) [PMID:8204608, PMID:1898017]. Through this Ca2+-switch it engages a panel of intracellular partners: CacyBP/SIP, whose binding occurs at a discrete site mapped by NMR with ~1 μM affinity and which links S100A6 to β-catenin/Tcf-LEF signaling and proliferation control [PMID:10884380, PMID:8973570, PMID:22295074]; the CacyBP yeast homolog Sgt1, where S100A6 binding blocks casein kinase II phosphorylation [PMID:12746458]; p53, which it binds Ca2+-dependently to enhance nuclear accumulation and transcriptional activity under stress [PMID:18765292]; the TPR-domain proteins Hop and kinesin light chain, where binding disrupts Hop–Hsp70/Hsp90 chaperone assembly and displaces JIP-1 from KLC [PMID:18669640]; and annexin 2, whose membrane localization S100A6 promotes to drive cancer cell motility [PMID:19724273]. S100A6 supports cell cycle progression and represses senescence, with its loss causing G0/G1 or G2/M arrest, reduced CDK1 and cyclins, and suppression of antiproliferative STAT1 signaling [PMID:20013795, PMID:23095053, PMID:27386938]; its trafficking and migratory functions depend on the actin/microfilament cytoskeleton [PMID:12118070, PMID:12577318]. Its expression is induced through multiple stress-responsive transcription factors—NF-κB downstream of TNF-α [PMID:18753141], Nrf2 via an antioxidant response element under oxidative stress [PMID:15878395], c-Myc [PMID:34060533], and ΔNp63 in keratinocyte differentiation [PMID:25450463]. Extracellularly, S100A6 signals through the C1/C2 immunoglobulin domains of RAGE to activate JNK-dependent apoptosis [PMID:17726019], and RAGE engagement also underlies its activity as a hepatokine that suppresses glucose-stimulated insulin secretion via diminished mitochondrial respiration [PMID:35899967] and its promotion of VEGF-D–driven lymphangiogenesis via NF-κB [PMID:38350547]. Additional roles include cardiomyocyte protection through calcineurin and improved calcium handling [PMID:28174168], maintenance of hematopoietic stem cell self-renewal through an Akt–Hsp90–mitochondrial calcium axis [PMID:32555370], and competition with zinc for Aβ to reduce amyloid plaque burden [PMID:31440382].","teleology":[{"year":1991,"claim":"Establishing that S100A6 is a genuine Ca2+-binding protein with its own target spectrum, rather than a calmodulin mimic, defined it as a distinct calcium effector.","evidence":"Ca2+-dependent affinity chromatography and calmodulin-dependent enzyme assays on S100A6 purified from rabbit lung, plus serum-stimulation Northern/run-off analysis in smooth muscle cells","pmids":["1898017","1757477"],"confidence":"Medium","gaps":["The identity of the 50 kDa cytosolic binding partner was not resolved","The post-transcriptional mechanism controlling cell-cycle-coupled mRNA levels was not defined"]},{"year":1994,"claim":"Quantitative biophysics established the Ca2+-binding stoichiometry, affinity, cooperativity, and conformational switch that mechanistically underlies S100A6 target engagement.","evidence":"Flow dialysis, fluorescence and UV difference spectroscopy, and ultracentrifugation on recombinant S100A6","pmids":["8204608"],"confidence":"High","gaps":["The low Ca2+ affinity (sub-millimolar) leaves the physiological trigger concentration unclear","No target was bound in this study to link the conformational change to function"]},{"year":2003,"claim":"Identification of the CacyBP/SIP family (p30, CacyBP, Sgt1) as Ca2+-regulated S100A6 partners with mapped binding domains gave the protein a defined intracellular effector pathway.","evidence":"Gel overlay, affinity purification, NMR chemical-shift perturbation, deletion mutagenesis, cross-linking, and CK II kinase assays","pmids":["8973570","10884380","12746458"],"confidence":"High","gaps":["The downstream consequence of inhibiting Sgt1 phosphorylation for substrate ubiquitination was not established in these studies","Binding was characterized in vitro and in cell extracts, not in a reconstituted ubiquitination system"]},{"year":2008,"claim":"S100A6 was shown to be a Ca2+-dependent regulator of p53 activity and of TPR-domain proteins, broadening its mechanism from a single-target protein to a hub disrupting chaperone and cargo-adaptor complexes.","evidence":"Affinity chromatography, co-IP, EMSA, luciferase reporters, GST pulldowns, and ionomycin stimulation across HEp-2 and Cos-7 cells","pmids":["18765292","18669640"],"confidence":"High","gaps":["How p53 enhancement reconciles with the separate report that S100A6 limits p53 phosphorylation in cardiomyocytes was not resolved","Physiological contexts where Hop/KLC disruption matters were not defined"]},{"year":2008,"claim":"Defining NF-κB (TNF-α), Nrf2/ARE (oxidative stress), c-Myc, and ΔNp63 as upstream regulators placed S100A6 within stress- and differentiation-responsive transcriptional programs.","evidence":"Promoter deletion, EMSA, ChIP, DNA affinity chromatography, and reporter assays in cardiomyocytes, keratinocytes, and cell lines","pmids":["18753141","15878395","34060533","25450463"],"confidence":"High","gaps":["The integration of these inputs in a single cell type was not addressed","Whether these regulators act combinatorially on the promoter is unknown"]},{"year":2009,"claim":"Linking S100A6 to annexin 2 membrane localization connected its Ca2+-binding activity to cancer cell motility via a defined cytoskeletal/membrane mechanism.","evidence":"Proteomic identification, reciprocal co-IP, co-immunofluorescence, siRNA, and motility assays in pancreatic cancer cells","pmids":["19724273"],"confidence":"High","gaps":["The structural basis of the annexin 2 interaction was not mapped","Whether the interaction is direct was not established by reconstitution"]},{"year":2012,"claim":"Loss-of-function studies established S100A6 as a positive regulator of cell cycle progression that opposes senescence, identifying CDK1/cyclin and STAT1 nodes.","evidence":"Stable siRNA/RNAi, flow cytometry cell cycle analysis, β-galactosidase assays, Western blotting, and transcriptomics in fibroblasts and endothelial cells","pmids":["20013795","23095053","27386938"],"confidence":"Medium","gaps":["The direct molecular link between S100A6 and CDK1 levels was not defined","Whether STAT1 suppression is a direct or indirect effect was not resolved"]},{"year":2012,"claim":"Biophysical aggregation studies revealed that S100A6 itself forms cytotoxic oligomers and seeds SOD1 aggregation, with Ca2+ as a protective conformational switch.","evidence":"Thioflavin-T kinetics, electron microscopy, FT-IR, seeding assays, and cell viability measurements","pmids":["23076148"],"confidence":"High","gaps":["Whether S100A6 fibrillation occurs at physiological pH in vivo was not addressed","The cellular relevance of SOD1 seeding was not demonstrated in vivo"]},{"year":2019,"claim":"Extracellular S100A6 was shown to act as a zinc competitor that reduces Aβ plaque burden, defining a protective extracellular role distinct from RAGE signaling.","evidence":"Incubation of recombinant S100A6 with APP/PS1 brain sections, co-culture, plaque/zinc quantification, and viability assays","pmids":["31440382"],"confidence":"Medium","gaps":["The effect was ex vivo/in vitro and not tested by systemic delivery in vivo","Whether endogenous S100A6 reaches relevant extracellular concentrations in brain is unknown"]},{"year":2024,"claim":"Tissue-level studies established physiological extracellular RAGE-dependent roles for S100A6 as a hepatokine suppressing insulin secretion and as a tumor-secreted lymphangiogenic factor.","evidence":"KO/depletion and overexpression in mouse HSCs, liver, and tumor models with Seahorse, GSIS, RAGE/NF-κB pathway, and VEGF-D readouts plus human sample validation","pmids":["32555370","35899967","38350547"],"confidence":"High","gaps":["Whether the same RAGE-coupled mechanism operates across these tissues was not directly compared","The molecular basis linking RAGE to mitochondrial respiration was not fully dissected"]},{"year":null,"claim":"How the multiple intracellular partner interactions, extracellular RAGE signaling, transcriptional inputs, and aggregation propensity are integrated into a unified, context-specific function for S100A6 remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model reconciles the competing partner-binding surfaces in a cellular context","The determinants directing S100A6 to intracellular versus secreted roles are unknown","Whether the pro-apoptotic and pro-survival activities reflect cell-type-specific partner availability is undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,4,6,27]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,23,24]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[11,12]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[19]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[9,10,11]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[11,12,14]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,19,23,24]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[14,15,25]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,23,24]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[2,13]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,1,18]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[1,2,13,26,28]}],"complexes":["S100A6 homodimer","S100B–S100A6 heterocomplex"],"partners":["RAGE","TP53","CACYBP","SGT1","STIP1","KLC1","ANXA2","S100B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P06703","full_name":"Protein S100-A6","aliases":["Calcyclin","Growth factor-inducible protein 2A9","MLN 4","Prolactin receptor-associated protein","PRA","S100 calcium-binding protein A6"],"length_aa":90,"mass_kda":10.2,"function":"May function as calcium sensor and modulator, contributing to cellular calcium signaling. May function by interacting with other proteins, such as TPR-containing proteins, and indirectly play a role in many physiological processes such as the reorganization of the actin cytoskeleton and in cell motility. Binds 2 calcium ions. 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international","url":"https://pubmed.ncbi.nlm.nih.gov/19712129","citation_count":23,"is_preprint":false},{"pmid":"34060533","id":"PMC_34060533","title":"c-Myc Upregulated by High Glucose Inhibits HaCaT Differentiation by S100A6 Transcriptional Activation.","date":"2021","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/34060533","citation_count":23,"is_preprint":false},{"pmid":"29800549","id":"PMC_29800549","title":"Therapeutic effects of recombinant human S100A6 and soluble receptor for advanced glycation end products(sRAGE) on CCl4-induced liver fibrosis in mice.","date":"2018","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29800549","citation_count":23,"is_preprint":false},{"pmid":"3838511","id":"PMC_3838511","title":"Characterisation of rat 9-kDa cholecalcin (CaBP) messenger RNA using a complementary DNA. Absence of homology with 28-kDa cholecalcin mRNA.","date":"1985","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/3838511","citation_count":23,"is_preprint":false},{"pmid":"28343163","id":"PMC_28343163","title":"S100A6 - focus on recent developments.","date":"2017","source":"Biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/28343163","citation_count":22,"is_preprint":false},{"pmid":"18201235","id":"PMC_18201235","title":"Expression of S100A6 protein in a broad spectrum of cutaneous tumors using tissue microarrays.","date":"2008","source":"Journal of cutaneous pathology","url":"https://pubmed.ncbi.nlm.nih.gov/18201235","citation_count":22,"is_preprint":false},{"pmid":"38350547","id":"PMC_38350547","title":"S100A6 drives lymphatic metastasis of liver cancer via activation of the RAGE/NF-kB/VEGF-D pathway.","date":"2024","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/38350547","citation_count":21,"is_preprint":false},{"pmid":"36674873","id":"PMC_36674873","title":"S100A6 Protein-Expression and Function in Norm and Pathology.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36674873","citation_count":20,"is_preprint":false},{"pmid":"25450463","id":"PMC_25450463","title":"S100A6 expression in keratinocytes and its impact on epidermal differentiation.","date":"2014","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25450463","citation_count":20,"is_preprint":false},{"pmid":"8545895","id":"PMC_8545895","title":"Detection of HLA IgG antibodies by two enzyme-linked immunoassays, solubilized HLA class I and PRA-STAT. Comparison with the AHG PRA.","date":"1995","source":"Transplantation","url":"https://pubmed.ncbi.nlm.nih.gov/8545895","citation_count":20,"is_preprint":false},{"pmid":"37509175","id":"PMC_37509175","title":"The Role of S100A6 in Human Diseases: Molecular Mechanisms and Therapeutic Potential.","date":"2023","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/37509175","citation_count":19,"is_preprint":false},{"pmid":"7645757","id":"PMC_7645757","title":"Distribution of OMP-, PGP 9.5- and CaBP-like immunoreactive chemoreceptor neurons in the developing human olfactory epithelium.","date":"1995","source":"Anatomy and embryology","url":"https://pubmed.ncbi.nlm.nih.gov/7645757","citation_count":19,"is_preprint":false},{"pmid":"31850060","id":"PMC_31850060","title":"S100A6 Promotes B Lymphocyte Penetration Through the Blood-Brain Barrier in Autoimmune Encephalitis.","date":"2019","source":"Frontiers in 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deposition in the shell gland on levels of messenger ribonucleic acid of CaBP-D28K and of vitamin D3 receptor in the shell gland of the laying hen.","date":"1995","source":"General and comparative endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/8536923","citation_count":17,"is_preprint":false},{"pmid":"1757477","id":"PMC_1757477","title":"Regulation of expression of the growth-state-related genes 2F1 and 2A9 during entry of quiescent smooth muscle cells into the cell cycle.","date":"1991","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1757477","citation_count":16,"is_preprint":false},{"pmid":"34950858","id":"PMC_34950858","title":"Toxoplasma gondii SAG1 targeting host cell S100A6 for parasite invasion and host immunity.","date":"2021","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/34950858","citation_count":16,"is_preprint":false},{"pmid":"23993025","id":"PMC_23993025","title":"Aberrant expression of S100A6 and matrix metalloproteinase 9, but not S100A2, S100A4, and S100A7, is associated with epidermal carcinogenesis.","date":"2013","source":"Journal of dermatological science","url":"https://pubmed.ncbi.nlm.nih.gov/23993025","citation_count":16,"is_preprint":false},{"pmid":"28646023","id":"PMC_28646023","title":"Amlexanox Downregulates S100A6 to Sensitize KMT2A/AFF1-Positive Acute Lymphoblastic Leukemia to TNFα Treatment.","date":"2017","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/28646023","citation_count":16,"is_preprint":false},{"pmid":"25120023","id":"PMC_25120023","title":"High-level S100A6 promotes metastasis and predicts the outcome of T1-T2 stage in clear cell renal cell carcinoma.","date":"2015","source":"Cell biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/25120023","citation_count":16,"is_preprint":false},{"pmid":"11200185","id":"PMC_11200185","title":"Regulation of cell specific expression of calcyclin (S100A6) in nerve cells and other tissues.","date":"2000","source":"Acta neurobiologiae experimentalis","url":"https://pubmed.ncbi.nlm.nih.gov/11200185","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52949,"output_tokens":7624,"usd":0.136603,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17093,"output_tokens":4526,"usd":0.099308,"stage2_stop_reason":"end_turn"},"total_usd":0.235911,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"S100A6 interacts specifically with the C1 and C2 extracellular immunoglobulin domains of RAGE (distinct from S100B which binds V and C1 domains), and extracellular S100A6 triggers apoptosis in SH-SY5Y neuroblastoma cells via activation of JNK (not PI3K/AKT or NF-κB), in a RAGE-dependent manner.\",\n      \"method\": \"In vitro binding assay with individual RAGE domain constructs, cell-based assay with ROS measurement, pathway inhibitor studies, and RAGE-blocking experiments in SH-SY5Y cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-specific binding assays and cell-based pathway analysis in single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"17726019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"S100A6 interacts with p53 in a calcium-dependent manner (shown by affinity chromatography and co-immunoprecipitation), enhances p53 transcriptional activity and nuclear accumulation under stress without affecting p53 DNA binding (by EMSA), and its presence increases cell susceptibility to hydrogen peroxide-induced apoptosis.\",\n      \"method\": \"Affinity chromatography, co-immunoprecipitation, EMSA, siRNA knockdown in HEp-2 cells, luciferase reporter assay, immunofluorescence for p53 localization\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding assays and multiple functional readouts in single lab\",\n      \"pmids\": [\"18765292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"S100A6 is induced by TNF-α via an NF-κB–dependent mechanism (p65 binds an NF-κB site at -460/-451 in the S100A6 promoter as shown by EMSA and ChIP); S100A6 limits TNF-α-induced cardiomyocyte apoptosis by interfering with p53 phosphorylation.\",\n      \"method\": \"Luciferase reporter assay, EMSA, chromatin immunoprecipitation (ChIP), siRNA knockdown, gene transfer overexpression in rat neonatal cardiac myocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (promoter deletion, EMSA, ChIP, siRNA, overexpression) in single rigorous study\",\n      \"pmids\": [\"18753141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"S100A6 and S100A11 are specific target proteins for S100B; Ca2+/Zn2+ stabilizes S100B–S100A6 heterocomplexes; the C-terminal residues Phe87/Phe88 of S100B are required for interaction with S100A6 (but not for S100B homodimerization); interaction confirmed in U373 astrocytoma cells by co-immunoprecipitation.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation, site-directed mutagenesis of S100B (Phe87/88), deletion analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — yeast two-hybrid discovery plus mutagenesis and co-IP validation\",\n      \"pmids\": [\"10913138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"S100A6 binds Sgt1 (yeast homologue of CacyBP/SIP) in a calcium-regulated manner via Sgt1's C-terminal 71 residues; S100A6 does not affect Skp1–Sgt1 binding; S100A6 inhibits casein kinase II–mediated phosphorylation of the S100A6-binding domain of Sgt1; interaction confirmed by co-immunoprecipitation from HEp-2 cell extracts.\",\n      \"method\": \"Affinity chromatography, chemical cross-linking, co-immunoprecipitation, kinase phosphorylation assay with CK II\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple biochemical methods (affinity chromatography, cross-linking, co-IP, kinase assay) with domain-mapping and functional endpoint\",\n      \"pmids\": [\"12746458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The S100A6-binding domain of CacyBP (residues 178–229) is necessary and sufficient for calcium-dependent binding to S100A6 with a Kd ~1 μM; NMR analysis revealed that CacyBP binding occurs at a discrete site on 15N-labeled S100A6.\",\n      \"method\": \"Limited proteolysis, deletion mutagenesis, fluorescence spectroscopy (Kd determination), NMR chemical shift perturbation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure plus mutagenesis and quantitative binding assays in one rigorous study\",\n      \"pmids\": [\"10884380\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"S100A6 binds the TPR domain of Hop (Hsp70/Hsp90-organizing protein) and of kinesin light chain (KLC) in a Ca2+-dependent manner; this binding inhibits Hop–Hsp70 and Hop–Hsp90 interactions and displaces JIP-1 from KLC in vitro and in ionomycin-stimulated Cos-7 cells.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation, in vitro binding inhibition assays, ionomycin stimulation of Cos-7 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — GST pulldown plus reciprocal co-IP plus cell stimulation experiments across multiple target proteins\",\n      \"pmids\": [\"18669640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"S100A6 binds annexin 2 in pancreatic cancer cells (confirmed by reciprocal immunoprecipitation); S100A6 promotes membrane localization of annexin 2; siRNA depletion of S100A6 reduces membrane annexin 2 levels and markedly reduces pancreatic cancer cell motility.\",\n      \"method\": \"Immunoprecipitation + 2D-gel electrophoresis + mass spectrometry, reciprocal co-immunoprecipitation, co-immunofluorescence, siRNA knockdown, Boyden chamber and wound healing motility assays\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomic screen, reciprocal co-IP, functional siRNA knockdown with defined readout\",\n      \"pmids\": [\"19724273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Recombinant S100A6 (CACY) binds 2 Ca2+ per monomer with low affinity (K0.5 = 0.32 mM), shows positive cooperativity (nH = 1.33), and Ca2+ binding induces a conformational change shifting Tyr to a less polar environment; Mg2+ does not affect Ca2+ binding or fluorescence properties; S100A6 forms homodimers but not heterodimers with CAPL in vitro.\",\n      \"method\": \"Flow dialysis calcium binding assay, fluorescence spectroscopy, UV difference spectroscopy, gel filtration/analytical ultracentrifugation\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with quantitative biophysical measurements and multiple methods\",\n      \"pmids\": [\"8204608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"S100A6 (calcyclin) interacts with a novel 30 kDa target protein (p30, later identified as CacyBP) in a Ca2+-dependent manner with higher affinity than annexin II or GAPDH; p30 was purified from Ehrlich ascites tumor cells and found in mouse brain and spleen.\",\n      \"method\": \"Gel overlay with 125I-labeled calcyclin, Ca2+-dependent affinity chromatography, Phenyl-Sepharose and CM-cellulose chromatography, partial amino acid sequencing\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — radiolabeled overlay plus affinity purification in single study; CacyBP identity confirmed in later work\",\n      \"pmids\": [\"8973570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"S100A6 (calcyclin/2A9 product) purified from rabbit lung binds 2 Ca2+ per mole, does not activate calmodulin-dependent enzymes (CaM kinase II, MLCK, phosphodiesterase), and interacts in a Ca2+-dependent manner with a 50 kDa cytosolic binding protein present in lung, intestine, and spleen.\",\n      \"method\": \"Ca2+-dependent affinity chromatography (W-77 Sepharose), UV difference spectroscopy, equilibrium dialysis, calmodulin-dependent enzyme activity assays\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro biochemical reconstitution; negative result for CaM-dependent enzyme activation is explicit\",\n      \"pmids\": [\"1898017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"S100A6 translocation in endothelial cells in response to increased intracellular calcium is dependent on actin stress fibers (distinct from S100A13 which uses the Golgi-ER pathway), implicating actin cytoskeleton in S100A6 intracellular trafficking.\",\n      \"method\": \"Live cell imaging/immunofluorescence of S100A6 translocation, cytoskeletal disruption experiments, comparison with S100A13 in angiotensin II–stimulated endothelial cells\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiments with pathway perturbation; single lab, single publication\",\n      \"pmids\": [\"12118070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Antisense-mediated reduction of S100A6 in pulmonary fibroblasts inhibits serum- and mechanical strain-induced cell proliferation, causes flattened cell morphology, and disrupts tropomyosin-labeled microfilament organization without reducing tropomyosin protein levels.\",\n      \"method\": \"Antisense RNA stable expression, proliferation assay, immunofluorescence of tropomyosin/microfilaments, cell morphology analysis\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with specific cytoskeletal and proliferative readouts; single lab\",\n      \"pmids\": [\"12577318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The S100A6 gene promoter contains a functional antioxidant response element (ARE) at -290/-281 that overlaps an E-box; oxidative stress agents (cadmium ions) activate S100A6 transcription via this ARE; Nrf2 transcription factor binds to this ARE region as shown by DNA affinity chromatography and EMSA; mutation of ARE inhibits cadmium-stimulated promoter activity.\",\n      \"method\": \"Luciferase reporter assay, RT-PCR, Northern blot, EMSA, site-directed mutation of ARE, DNA affinity chromatography + Western blot for Nrf2\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (mutagenesis, EMSA, affinity chromatography, reporter assay) converging on Nrf2/ARE mechanism\",\n      \"pmids\": [\"15878395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"S100A6 deficiency (stable siRNA knockdown) in NIH 3T3 fibroblasts causes G0/G1 cell cycle arrest unresponsive to serum, senescence-like morphological and biochemical changes (elevated β-galactosidase, gelatinase activity), disrupted actin cytoskeleton, and impaired cell adhesion and migration.\",\n      \"method\": \"Stable siRNA expression, cell cycle analysis by flow cytometry, β-galactosidase senescence assay, gelatinase assay, phalloidin staining, adhesion and migration assays\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined KO phenotype with multiple orthogonal readouts; single lab\",\n      \"pmids\": [\"20013795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"S100A6 depletion by RNAi in primary human endothelial cells causes G2/M cell cycle arrest, decreases CDK1 and phospho-CDK1 levels, reduces cyclin A1 (CCNA1) and cyclin B (CCNB1) gene expression, and induces β-galactosidase expression (senescence marker).\",\n      \"method\": \"RNAi knockdown, flow cytometry cell cycle analysis, Western blotting, qRT-PCR, β-galactosidase staining\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined KO phenotype with multiple molecular endpoints; single lab\",\n      \"pmids\": [\"23095053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"S100A6 suppresses antiproliferative STAT1 signaling in endothelial cells; S100A6 silencing combined with VEGFA stimulation revealed interferon-inducible transmembrane protein 1 and PIAS proteins as key components linking S100A6 to STAT1 suppression.\",\n      \"method\": \"siRNA knockdown in human endothelial cells, gene expression time-series analysis, bioinformatic pathway modeling, experimental validation of STAT1 pathway components\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic transcriptomics plus experimental validation; single lab\",\n      \"pmids\": [\"27386938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"S100A6 forms amyloid fibrils under acidic conditions; Ca2+ inhibits fibrillation (promoting anti-parallel β-sheet conformations that repress fibril formation) by a mechanism reversible upon chelation; S100A6 oligomers (not fibrils) are cytotoxic (reducing cell viability ~40%); native S100A6 seeds SOD1 aggregation, shortening its nucleation phase.\",\n      \"method\": \"Thioflavin-T kinetics, electron microscopy, FT-IR spectroscopy, cell viability assay, seeding aggregation kinetics with SOD1, computational aggregation prediction\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple biophysical and biochemical methods with mechanistic controls (chelation reversal, Ca2+ dose) in single rigorous study\",\n      \"pmids\": [\"23076148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"S100A6 overexpression in rat neonatal cardiomyocytes improves calcium transients and protects against hypoxia-reoxygenation-induced apoptosis via enhanced calcineurin activity; in vivo S100A6 gene therapy (via ultrasound-targeted microbubble destruction) reduced infarct size and improved left ventricular systolic function after ischemia-reperfusion.\",\n      \"method\": \"S100A6 overexpression and siRNA knockdown in cardiomyocytes, calcium transient imaging, calcineurin activity assay, in vivo gene delivery + coronary ligation/reperfusion model in Fischer-344 rats\",\n      \"journal\": \"Journal of the American Heart Association\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro functional assay plus in vivo model; single lab, calcineurin mechanism identified but not deeply dissected\",\n      \"pmids\": [\"28174168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Extracellular S100A6 competes with zinc ions for binding to Aβ, reducing amyloid plaque burden in APP/PS1 mouse brain sections; exogenous S100A6 decreased plaque-associated zinc content and protected COS-7 cells against zinc toxicity.\",\n      \"method\": \"In vitro incubation of brain sections with recombinant S100A6, co-culture with S100A6-expressing cells, Aβ plaque quantification, zinc chelator (clioquinol) control experiments, cell viability assay\",\n      \"journal\": \"Aging and disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ex vivo tissue and in vitro cell experiments with biochemical controls; single lab\",\n      \"pmids\": [\"31440382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"S100A6 knockout in mouse hematopoietic stem cells (HSCs) reduces self-renewal and regenerative capacity, decreases phospho-Akt and Hsp90 levels, impairs mitochondrial respiratory capacity and mitochondrial calcium buffering; Akt activator SC79 rescues intracellular/mitochondrial calcium levels and colony-forming and Hsp90 activity.\",\n      \"method\": \"S100A6 KO mouse model, flow cytometry, transcriptomics, proteomics, Seahorse mitochondrial assay, calcium imaging, pharmacological Akt activation rescue experiments\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse with transcriptomics, proteomics, and multiple functional readouts plus pharmacological rescue in single comprehensive study\",\n      \"pmids\": [\"32555370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"S100A6 overexpression in HCC cells causes down-regulation of E-cadherin, nuclear accumulation of β-catenin, and promotes proliferation and migration via activation of the PI3K/AKT pathway; intracellular (not extracellular) S100A6 is sufficient to rescue proliferation and migration defects after S100A6 silencing.\",\n      \"method\": \"siRNA knockdown, recombinant S100A6 with cell-penetrating peptide re-expression, Western blotting for E-cadherin/β-catenin, PI3K inhibitor (LY294002) treatment, proliferation and migration assays\",\n      \"journal\": \"Journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — orthogonal gain/loss-of-function with pathway inhibitor; single lab\",\n      \"pmids\": [\"24281831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"S100A6 promotes colorectal carcinoma cell proliferation via ERK pathway and migration via p38 MAPK pathway; ERK inhibitor partially attenuates S100A6-induced proliferation and p38 inhibitor suppresses S100A6-induced migration.\",\n      \"method\": \"Adenoviral overexpression, recombinant S100A6 protein treatment, RNAi knockdown, kinase inhibitors (ERK, p38), in vitro proliferation/migration assays, nude mouse xenograft\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple gain/loss-of-function approaches with pathway-specific inhibitors; single lab\",\n      \"pmids\": [\"24378749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Liver-derived S100A6 (a hepatokine) inhibits glucose-stimulated insulin secretion (GSIS) from β cells via activation of RAGE and diminution of mitochondrial respiration; hepatic S100A6 transcription is driven by ChREBP; ectopic hepatic ChREBP overexpression suppresses GSIS in an S100A6-dependent manner; depletion of hepatic S100A6 improves GSIS and glycemia in mice.\",\n      \"method\": \"High-fat diet mouse model, hepatic S100A6 depletion (siRNA/KO), GSIS assay, RAGE pathway assay, Seahorse mitochondrial respiration, ChREBP overexpression in liver, human NAFLD patient serum measurements\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo and in vitro approaches (KO, overexpression, RAGE pathway, mitochondrial assay, human validation) in single comprehensive study\",\n      \"pmids\": [\"35899967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Secreted S100A6 from tumor cells promotes lymphangiogenesis in human lymphatic endothelial cells (HLECs) by upregulating VEGF-D expression and secretion via the RAGE/NF-κB/VEGF-D signaling pathway, thereby driving lymph node metastasis of liver cancer.\",\n      \"method\": \"Single-cell RNA-seq analysis, HLEC co-culture experiments, S100A6 overexpression/knockdown, RAGE/NF-κB pathway inhibition, VEGF-D ELISA, in vivo lymphatic metastasis model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro mechanistic pathway studies and in vivo model; single lab\",\n      \"pmids\": [\"38350547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"S100A6 (2A9/calcyclin) mRNA is low in quiescent vascular smooth muscle cells and increases 2–4 h after serum re-addition (cell cycle entry); this regulation occurs post-transcriptionally as no change in transcription rate was detected by nuclear run-off assay.\",\n      \"method\": \"Northern blotting, serum deprivation/re-addition synchronization, nuclear run-off transcription assay\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — explicit nuclear run-off assay establishes post-transcriptional regulation; single lab\",\n      \"pmids\": [\"1757477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"c-Myc directly binds the S100A6 promoter to activate S100A6 transcription in keratinocytes; high-glucose-induced c-Myc upregulates S100A6 to inhibit HaCaT keratinocyte differentiation via WNT/β-catenin pathway; knockdown of S100A6 rescues the differentiation dysfunction caused by c-Myc overexpression or high glucose.\",\n      \"method\": \"ChIP assay, luciferase reporter assay, siRNA knockdown, overexpression, Western blotting for differentiation markers, organotypic culture\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-confirmed direct promoter binding plus rescue experiments; single lab\",\n      \"pmids\": [\"34060533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"S100A6 interaction with wild-type CacyBP/SIP (but not with a truncated mutant lacking the S100-binding domain) negatively regulates CacyBP/SIP-mediated inhibition of gastric cancer cell proliferation and tumorigenesis; S100A6 binding to CacyBP/SIP modulates β-catenin protein expression and Tcf/LEF transcriptional activation.\",\n      \"method\": \"Co-immunoprecipitation of endogenous S100A6 with CacyBP/SIP, truncation mutant expression, MTT/FACS/clonogenic assay, tumor xenograft\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with domain deletion mutant and functional readouts; single lab\",\n      \"pmids\": [\"22295074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"S100A6 overexpression in keratinocytes suppresses loricrin expression, accelerates proliferation, and blocks epidermal differentiation in organotypic culture; S100A6 expression is regulated during differentiation via ΔNp63 and retinoic acid (not by DNA methylation) as shown by bisulfite treatment, luciferase assay, and ChIP.\",\n      \"method\": \"Stable knockdown and overexpression in HaCaT cells, organotypic (3D) culture, bisulfite sequencing, luciferase reporter, ChIP for ΔNp63, retinoic acid treatment\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — 2D and 3D functional models plus mechanistic epigenetic/transcriptional dissection; single lab\",\n      \"pmids\": [\"25450463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"S100A6 promotes B lymphocyte infiltration through the blood-brain barrier endothelial layer; recombinant S100A6 protein treatment of an in vitro transendothelial migration model significantly increased B cell penetration, partially recapitulating the effect of autoimmune encephalitis serum.\",\n      \"method\": \"In vitro leukocyte transendothelial migration assay, recombinant S100A6 protein treatment, genome-wide DNA methylation assay, qPCR\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single assay with recombinant protein; no receptor/pathway identified for the BBB penetration effect\",\n      \"pmids\": [\"31850060\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"S100A6 (calcyclin) is a dimeric, Ca2+- and Zn2+-binding EF-hand protein that undergoes Ca2+-induced conformational changes exposing hydrophobic surfaces, enabling it to interact with diverse intracellular targets—including p53 (enhancing nuclear accumulation and transcriptional activity), CacyBP/SIP (regulating β-catenin ubiquitination and cell proliferation), Sgt1 (inhibiting its CK II-mediated phosphorylation), Hop/KLC (disrupting chaperone and cargo-adaptor complexes in a Ca2+-dependent manner), and annexin 2 (promoting cancer cell motility)—while extracellularly it signals through RAGE (C1/C2 domains) to activate JNK and apoptosis, acts as a hepatokine that impairs β-cell insulin secretion via RAGE/mitochondrial respiration, competes for zinc to reduce Aβ aggregation, and promotes lymphangiogenesis via RAGE/NF-κB/VEGF-D; intracellularly S100A6 supports cell cycle progression (regulating CDK1 levels and suppressing STAT1 signaling), cytoskeletal dynamics via actin stress fibers, and HSC self-renewal through the Akt–Hsp90–mitochondrial calcium axis, while its transcription is regulated by NF-κB (TNF-α stimulus), Nrf2/ARE (oxidative stress), c-Myc, and ΔNp63.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"S100A6 (calcyclin) is a small, homodimeric EF-hand protein that binds two Ca2+ per monomer with low affinity and positive cooperativity, undergoing a Ca2+-induced conformational change that shifts buried aromatic residues into a less polar environment and creates target-binding surfaces, while remaining functionally distinct from calmodulin (it does not activate calmodulin-dependent enzymes) [#8, #10]. Through this Ca2+-switch it engages a panel of intracellular partners: CacyBP/SIP, whose binding occurs at a discrete site mapped by NMR with ~1 \\u03bcM affinity and which links S100A6 to \\u03b2-catenin/Tcf-LEF signaling and proliferation control [#5, #9, #27]; the CacyBP yeast homolog Sgt1, where S100A6 binding blocks casein kinase II phosphorylation [#4]; p53, which it binds Ca2+-dependently to enhance nuclear accumulation and transcriptional activity under stress [#1]; the TPR-domain proteins Hop and kinesin light chain, where binding disrupts Hop\\u2013Hsp70/Hsp90 chaperone assembly and displaces JIP-1 from KLC [#6]; and annexin 2, whose membrane localization S100A6 promotes to drive cancer cell motility [#7]. S100A6 supports cell cycle progression and represses senescence, with its loss causing G0/G1 or G2/M arrest, reduced CDK1 and cyclins, and suppression of antiproliferative STAT1 signaling [#14, #15, #16]; its trafficking and migratory functions depend on the actin/microfilament cytoskeleton [#11, #12]. Its expression is induced through multiple stress-responsive transcription factors\\u2014NF-\\u03baB downstream of TNF-\\u03b1 [#2], Nrf2 via an antioxidant response element under oxidative stress [#13], c-Myc [#26], and \\u0394Np63 in keratinocyte differentiation [#28]. Extracellularly, S100A6 signals through the C1/C2 immunoglobulin domains of RAGE to activate JNK-dependent apoptosis [#0], and RAGE engagement also underlies its activity as a hepatokine that suppresses glucose-stimulated insulin secretion via diminished mitochondrial respiration [#23] and its promotion of VEGF-D\\u2013driven lymphangiogenesis via NF-\\u03baB [#24]. Additional roles include cardiomyocyte protection through calcineurin and improved calcium handling [#18], maintenance of hematopoietic stem cell self-renewal through an Akt\\u2013Hsp90\\u2013mitochondrial calcium axis [#20], and competition with zinc for A\\u03b2 to reduce amyloid plaque burden [#19].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Establishing that S100A6 is a genuine Ca2+-binding protein with its own target spectrum, rather than a calmodulin mimic, defined it as a distinct calcium effector.\",\n      \"evidence\": \"Ca2+-dependent affinity chromatography and calmodulin-dependent enzyme assays on S100A6 purified from rabbit lung, plus serum-stimulation Northern/run-off analysis in smooth muscle cells\",\n      \"pmids\": [\"1898017\", \"1757477\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The identity of the 50 kDa cytosolic binding partner was not resolved\", \"The post-transcriptional mechanism controlling cell-cycle-coupled mRNA levels was not defined\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Quantitative biophysics established the Ca2+-binding stoichiometry, affinity, cooperativity, and conformational switch that mechanistically underlies S100A6 target engagement.\",\n      \"evidence\": \"Flow dialysis, fluorescence and UV difference spectroscopy, and ultracentrifugation on recombinant S100A6\",\n      \"pmids\": [\"8204608\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The low Ca2+ affinity (sub-millimolar) leaves the physiological trigger concentration unclear\", \"No target was bound in this study to link the conformational change to function\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identification of the CacyBP/SIP family (p30, CacyBP, Sgt1) as Ca2+-regulated S100A6 partners with mapped binding domains gave the protein a defined intracellular effector pathway.\",\n      \"evidence\": \"Gel overlay, affinity purification, NMR chemical-shift perturbation, deletion mutagenesis, cross-linking, and CK II kinase assays\",\n      \"pmids\": [\"8973570\", \"10884380\", \"12746458\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The downstream consequence of inhibiting Sgt1 phosphorylation for substrate ubiquitination was not established in these studies\", \"Binding was characterized in vitro and in cell extracts, not in a reconstituted ubiquitination system\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"S100A6 was shown to be a Ca2+-dependent regulator of p53 activity and of TPR-domain proteins, broadening its mechanism from a single-target protein to a hub disrupting chaperone and cargo-adaptor complexes.\",\n      \"evidence\": \"Affinity chromatography, co-IP, EMSA, luciferase reporters, GST pulldowns, and ionomycin stimulation across HEp-2 and Cos-7 cells\",\n      \"pmids\": [\"18765292\", \"18669640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How p53 enhancement reconciles with the separate report that S100A6 limits p53 phosphorylation in cardiomyocytes was not resolved\", \"Physiological contexts where Hop/KLC disruption matters were not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defining NF-\\u03baB (TNF-\\u03b1), Nrf2/ARE (oxidative stress), c-Myc, and \\u0394Np63 as upstream regulators placed S100A6 within stress- and differentiation-responsive transcriptional programs.\",\n      \"evidence\": \"Promoter deletion, EMSA, ChIP, DNA affinity chromatography, and reporter assays in cardiomyocytes, keratinocytes, and cell lines\",\n      \"pmids\": [\"18753141\", \"15878395\", \"34060533\", \"25450463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The integration of these inputs in a single cell type was not addressed\", \"Whether these regulators act combinatorially on the promoter is unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linking S100A6 to annexin 2 membrane localization connected its Ca2+-binding activity to cancer cell motility via a defined cytoskeletal/membrane mechanism.\",\n      \"evidence\": \"Proteomic identification, reciprocal co-IP, co-immunofluorescence, siRNA, and motility assays in pancreatic cancer cells\",\n      \"pmids\": [\"19724273\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The structural basis of the annexin 2 interaction was not mapped\", \"Whether the interaction is direct was not established by reconstitution\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Loss-of-function studies established S100A6 as a positive regulator of cell cycle progression that opposes senescence, identifying CDK1/cyclin and STAT1 nodes.\",\n      \"evidence\": \"Stable siRNA/RNAi, flow cytometry cell cycle analysis, \\u03b2-galactosidase assays, Western blotting, and transcriptomics in fibroblasts and endothelial cells\",\n      \"pmids\": [\"20013795\", \"23095053\", \"27386938\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The direct molecular link between S100A6 and CDK1 levels was not defined\", \"Whether STAT1 suppression is a direct or indirect effect was not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Biophysical aggregation studies revealed that S100A6 itself forms cytotoxic oligomers and seeds SOD1 aggregation, with Ca2+ as a protective conformational switch.\",\n      \"evidence\": \"Thioflavin-T kinetics, electron microscopy, FT-IR, seeding assays, and cell viability measurements\",\n      \"pmids\": [\"23076148\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether S100A6 fibrillation occurs at physiological pH in vivo was not addressed\", \"The cellular relevance of SOD1 seeding was not demonstrated in vivo\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extracellular S100A6 was shown to act as a zinc competitor that reduces A\\u03b2 plaque burden, defining a protective extracellular role distinct from RAGE signaling.\",\n      \"evidence\": \"Incubation of recombinant S100A6 with APP/PS1 brain sections, co-culture, plaque/zinc quantification, and viability assays\",\n      \"pmids\": [\"31440382\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The effect was ex vivo/in vitro and not tested by systemic delivery in vivo\", \"Whether endogenous S100A6 reaches relevant extracellular concentrations in brain is unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Tissue-level studies established physiological extracellular RAGE-dependent roles for S100A6 as a hepatokine suppressing insulin secretion and as a tumor-secreted lymphangiogenic factor.\",\n      \"evidence\": \"KO/depletion and overexpression in mouse HSCs, liver, and tumor models with Seahorse, GSIS, RAGE/NF-\\u03baB pathway, and VEGF-D readouts plus human sample validation\",\n      \"pmids\": [\"32555370\", \"35899967\", \"38350547\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the same RAGE-coupled mechanism operates across these tissues was not directly compared\", \"The molecular basis linking RAGE to mitochondrial respiration was not fully dissected\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple intracellular partner interactions, extracellular RAGE signaling, transcriptional inputs, and aggregation propensity are integrated into a unified, context-specific function for S100A6 remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model reconciles the competing partner-binding surfaces in a cellular context\", \"The determinants directing S100A6 to intracellular versus secreted roles are unknown\", \"Whether the pro-apoptotic and pro-survival activities reflect cell-type-specific partner availability is undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 4, 6, 27]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 23, 24]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [11, 12]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [9, 10, 11]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [11, 12, 14]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 19, 23, 24]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [14, 15, 25]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 23, 24]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [2, 13]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 1, 18]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [1, 2, 13, 26, 28]}\n    ],\n    \"complexes\": [\n      \"S100A6 homodimer\",\n      \"S100B\\u2013S100A6 heterocomplex\"\n    ],\n    \"partners\": [\n      \"RAGE\",\n      \"TP53\",\n      \"CACYBP\",\n      \"SGT1\",\n      \"STIP1\",\n      \"KLC1\",\n      \"ANXA2\",\n      \"S100B\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}