{"gene":"STIM2","run_date":"2026-06-10T07:46:43","timeline":{"discoveries":[{"year":2007,"finding":"STIM2 functions as a feedback regulator that stabilizes basal cytosolic and ER Ca2+ levels by activating Ca2+ influx through Orai1 in response to smaller decreases in ER Ca2+ than those required for STIM1 activation. siRNA screen identified STIM2 as the strongest positive regulator of basal Ca2+ concentration.","method":"siRNA screen of human signaling proteome, Ca2+ imaging, functional rescue assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic siRNA screen plus functional Ca2+ measurements; independently replicated across multiple subsequent studies","pmids":["18160041"],"is_preprint":false},{"year":2006,"finding":"STIM2 acts as an inhibitor of STIM1-mediated store-operated Ca2+ entry (SOC). STIM2 is expressed only intracellularly (not at plasma membrane unlike STIM1), translocates into puncta upon store depletion only when coexpressed with STIM1, co-localizes with STIM1 in puncta, and physically interacts with STIM1 by co-immunoprecipitation. STIM2 inhibits SOCE at a step downstream of puncta formation.","method":"Overexpression in HEK293/PC12/A7r5/Jurkat cells, subcellular localization by immunofluorescence, co-immunoprecipitation, functional Ca2+ entry assays","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, localization studies, functional assays in multiple cell lines; findings replicated by multiple subsequent studies","pmids":["16860747"],"is_preprint":false},{"year":2007,"finding":"Biophysical characterization of STIM2 EF-SAM domain reveals a Ca2+-binding affinity (Kd ~0.5 mM) similar to STIM1, but apo-STIM2 EF-SAM is more structurally stable and does not readily aggregate compared to apo-STIM1 EF-SAM, which may account for STIM2's distinct functional properties and lower activation threshold.","method":"CD spectroscopy, biophysical characterization of recombinant EF-SAM domain in vitro","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with direct biophysical measurements on purified domain; single lab but multiple methods (CD, aggregation assays)","pmids":["18166150"],"is_preprint":false},{"year":2007,"finding":"STIM2 activates CRAC channels via two distinct modes: a store-operated mode triggered by ER Ca2+ depletion via IP3, and a store-independent mode activated by cell dialysis during whole-cell patch-clamp. Both modes are regulated by calmodulin (CaM); CaM inhibition can be reversed by 2-APB. The aminoglycoside antibiotic G418 specifically and potently inhibits STIM2-dependent CRAC channel activation.","method":"Whole-cell patch-clamp, Ca2+ imaging, pharmacological manipulation with calmodulin inhibitors and 2-APB, G418 treatment","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — electrophysiological recordings plus pharmacological dissection; single lab, multiple orthogonal methods","pmids":["17905723"],"is_preprint":false},{"year":2008,"finding":"STIM2 deficiency in mouse T cells and fibroblasts results in a smaller impairment of store-operated Ca2+ influx compared to STIM1 deficiency, but both STIM1 and STIM2 are required for cytokine production and nuclear translocation of NFAT. T cell-specific deletion of both STIM1 and STIM2 causes lymphoproliferative phenotype and reduced regulatory T cell numbers.","method":"Conditional knockout mice, Ca2+ imaging, NFAT nuclear translocation assays, flow cytometry, cytokine measurement","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple orthogonal readouts; replicated by multiple subsequent studies","pmids":["18327260"],"is_preprint":false},{"year":2009,"finding":"STIM2, but not STIM1, is essential for capacitive Ca2+ entry (CCE) and ischemia-induced cytosolic Ca2+ accumulation in neurons. Neurons from Stim2-/- mice showed increased survival under hypoxic conditions in culture and in acute hippocampal slices, and Stim2-/- mice were protected from neurological damage in focal cerebral ischemia in vivo.","method":"Stim2 knockout mice, Ca2+ imaging in neurons, hippocampal slice preparations, focal cerebral ischemia model in vivo","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with both in vitro and in vivo phenotypic readouts; STIM1 vs STIM2 specificity tested","pmids":["19843959"],"is_preprint":false},{"year":2010,"finding":"STIM1 and STIM2 interact physically (FRET between CFP-STIM1 and YFP-STIM2 increases upon SOCE activation; confirmed by co-immunoprecipitation of endogenous proteins), both contribute to SOCE and myoblast differentiation, and both are required for ER Ca2+ refilling during excitation-contraction coupling in human myotubes. The two proteins co-localize into clusters during SOCE activation.","method":"FRET live cell imaging, co-immunoprecipitation of endogenous proteins, siRNA silencing, Ca2+ imaging, myoblast differentiation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — FRET plus reciprocal co-IP of endogenous proteins plus functional assays; single lab, multiple orthogonal methods","pmids":["20436167"],"is_preprint":false},{"year":2011,"finding":"STIM1 and STIM2 are localized in acidic Ca2+ stores (lysosome-related organelles and dense granules) in human platelets. Depletion of acidic Ca2+ stores enhances STIM1-STIM2 association, association of both with Orai1, co-immunoprecipitation of STIM1 with hTRPC1 and hTRPC6, and association of Orai1 with TRPC proteins. Depletion also enhances STIM2-SERCA3 association.","method":"Immunomagnetic sorting of organelle fractions, co-immunoprecipitation, Ca2+ imaging with bafilomycin A1 (vacuolar H+-ATPase inhibitor)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — subcellular fractionation and co-IP; single lab, multiple interaction partners tested","pmids":["21321120"],"is_preprint":false},{"year":2011,"finding":"In rat cortical neurons, thapsigargin-induced ER store depletion redistributes endogenous STIM1 and STIM2 to membrane fractions and increases STIM1/ORAI1 and STIM2/ORAI1 complexes. STIM1/ORAI1 mainly activates SOCE, whereas STIM2/ORAI1 regulates resting ER Ca2+ levels and Ca2+ leakage; SOCE inhibitors ML-9 and 2-APB affect STIM1/ORAI1 but not STIM2/ORAI1.","method":"Subcellular fractionation, YFP-STIM overexpression, Ca2+ imaging with Fura-2, pharmacological inhibitors","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — membrane fractionation plus functional Ca2+ assays; single lab, multiple methods","pmids":["21541286"],"is_preprint":false},{"year":2011,"finding":"A cytosolic preSTIM2 protein is produced by inefficient signal peptide cleavage. This preSTIM2 localizes to the inner leaflet of the plasma membrane where it interacts with ORAI1 to regulate basal Ca2+ concentration and Ca2+-dependent gene transcription in a store-independent manner. A third peptide fragment from the STIM2 signal peptide is released into cytosol and regulates gene transcription in a Ca2+-independent manner.","method":"Signal peptide mutagenesis, subcellular fractionation, co-immunoprecipitation with ORAI1, Ca2+ imaging, transcription reporter assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of signal peptide plus localization and functional studies; single lab, multiple methods","pmids":["21383014"],"is_preprint":false},{"year":2012,"finding":"Polyamines regulate intestinal epithelial restitution by altering the STIM1/STIM2 ratio. Increased polyamines stimulate STIM1 but inhibit STIM2 expression, while polyamine depletion decreases STIM1 and increases STIM2. Induced STIM1/STIM2 heteromers (by polyamine depletion or STIM2 overexpression) suppress STIM1 membrane translocation, reduce TRPC1-mediated Ca2+ influx, and inhibit cell migration.","method":"ODC overexpression, ODC inhibitor treatment, co-immunoprecipitation of STIM1/STIM2 complexes, Ca2+ imaging, cell migration wound-healing assay","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP of STIM1/STIM2 heteromers plus functional migration assays; single lab","pmids":["22592407"],"is_preprint":false},{"year":2013,"finding":"Endogenous STIM2 forms a calcium-sensitive, thapsigargin-insensitive complex with ORAI1 in cortical neurons. The number of STIM2-ORAI1 complexes increases when intracellular Ca2+ is decreased by BAPTA-AM or low-calcium medium but does not increase with thapsigargin. This indicates that small drops in ER Ca2+ (triggered by decreased intracellular Ca2+) are sufficient to initiate STIM2-ORAI1 complex formation in neurons.","method":"Co-immunoprecipitation, Proximity Ligation Assay (PLA), Ca2+ imaging with Fura-2","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — endogenous protein PLA plus co-IP plus functional Ca2+ imaging; single lab","pmids":["23711249"],"is_preprint":false},{"year":2013,"finding":"STIM2 drives Ca2+ oscillations in mast cells, T cells, and HEK293 cells by mediating store-operated Ca2+ entry at low levels of store depletion (mild ER Ca2+ reduction). siRNA silencing of STIM2 or inhibition by G418 suppresses SOCE and Ca2+ oscillations at low agonist concentrations without interfering with STIM1-mediated signals at full store depletion, indicating STIM2 is preferentially activated by physiological low-level stimulation.","method":"siRNA silencing, G418 pharmacological inhibition, Ca2+ oscillation measurements in multiple cell types","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA plus pharmacological inhibition in multiple cell types; single lab","pmids":["23359669"],"is_preprint":false},{"year":2014,"finding":"STIM2-mediated neuronal store-operated Ca2+ influx (nSOC) is required for stabilization of mushroom dendritic spines in hippocampal neurons through continuous activation of CaMKII. The STIM2-nSOC-CaMKII pathway is compromised in PS1-M146V knockin AD neurons, aging neurons, and sporadic AD brains due to STIM2 downregulation. STIM2 overexpression rescues synaptic nSOC, CaMKII activity, and mushroom spine loss.","method":"PS1 knockin mouse model, spine morphology analysis, Ca2+ imaging, CaMKII activity assay, STIM2 overexpression rescue","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic model plus functional rescue with multiple orthogonal readouts (Ca2+ imaging, CaMKII activity, spine morphology); replicated in subsequent papers","pmids":["24698269"],"is_preprint":false},{"year":2014,"finding":"STIM2 in native HEK293 cells specifically regulates endogenous non-CRAC Imin channels (a store-operated channel distinct from CRAC), whereas STIM1 blocks Imin channel activation. Changes in the ratio of active STIM2 to STIM1 can switch Imin channel regulation between store-operated and store-independent modes. STIM1 and STIM2 also differ in regulation of other channels: TRPC3-containing INS channels are induced by STIM1, and TRPC1-composed Imax channels are activated by both.","method":"Single-channel patch-clamp recordings, STIM1/STIM2 selective activation, overexpression studies","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-channel electrophysiology with selective activation; single lab","pmids":["25533457"],"is_preprint":false},{"year":2015,"finding":"STIM2.1, an alternatively spliced isoform retaining an additional exon in the channel-activating domain region, is an inhibitor of SOCE. STIM2.1 shows impaired interaction with Orai1 and prevents Orai1 activation, but shows increased affinity towards calmodulin compared to STIM2.2. Knockdown of STIM2.1 increases SOCE in naive CD4+ T cells while STIM2.2 knockdown decreases SOCE.","method":"siRNA knockdown in naive T cells, Orai1 co-immunoprecipitation, calmodulin binding assays, Ca2+ imaging","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal knockdown with opposite SOCE phenotypes, plus binding studies; single lab, multiple methods","pmids":["25896806"],"is_preprint":false},{"year":2015,"finding":"STIM2β (equivalent to STIM2.1), a conserved alternatively spliced isoform of STIM2, is a potent inhibitor of SOCE. Although STIM2β does not strongly bind Orai1 by itself, it is recruited to Orai1 channels by forming heterodimers with other STIM isoforms. Mutational analysis and Orai1-STIM2β chimeras indicate it inhibits SOCE through a sequence-specific allosteric interaction with Orai1.","method":"Overexpression and mutagenesis, heterodimer formation assay, Orai1-STIM2β chimeric constructs, Ca2+ entry measurements","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — mutagenesis plus chimeric protein approach plus functional readout; independent replication of STIM2.1 inhibitory function (consistent with PMID 25896806)","pmids":["26033257"],"is_preprint":false},{"year":2015,"finding":"STIM2 enhances agonist-mediated SOCE by promoting STIM1 clustering at ER-PM junctions at low stimulus intensities. STIM2 lacking five C-terminal amino acids failed to promote STIM1 puncta formation at low agonist concentrations. Coexpression of STIM2 with STIM1ΔK (lacking polybasic region) resulted in co-clustering, suggesting STIM2 recruits STIM1 to ER-PM junctions when ER Ca2+ stores are mildly depleted. STIM2 knockout in mouse salivary glands diminished fluid secretion and SOCE in acinar cells stimulated with low muscarinic agonist concentrations.","method":"Conditional STIM2 deletion in salivary glands, C-terminal deletion mutants of STIM2, live cell imaging of STIM1 puncta, Ca2+ imaging, NFAT nuclear translocation assay","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO in vivo plus C-terminal mutagenesis plus live imaging; multiple orthogonal methods","pmids":["25587190"],"is_preprint":false},{"year":2015,"finding":"STIM2 regulates PKA-dependent phosphorylation of the AMPA receptor subunit GluA1 and controls GluA1 surface delivery (both exocytosis and endocytosis). cAMP triggers rapid migration of STIM2 to ER-PM contact sites and promotes GluA1 recruitment to these junctions and STIM2 localization in dendritic spines. STIM2 regulates GluA1 phosphorylation by coupling PKA to AMPARs in a SOCE-independent manner.","method":"Biochemical assays, live-cell imaging, STIM2 KO neurons, PKA phosphorylation assays, surface GluA1 trafficking assays","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO neurons plus biochemical interaction studies plus imaging; single lab","pmids":["25609091"],"is_preprint":false},{"year":2015,"finding":"Expression of STIM2 protects hippocampal mushroom spines from Aβ42 oligomer-induced toxicity by rescuing CaMKII activity. Aβ42 oligomer application (in vitro and in vivo by hippocampal injection) reduces mushroom spines and synaptic CaMKII activity; STIM2 overexpression rescues both.","method":"In vitro hippocampal cultures with Aβ42 oligomers, in vivo Aβ42 injection into hippocampus, dendritic spine morphology analysis, CaMKII activity measurement, STIM2 overexpression","journal":"Molecular neurodegeneration","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — both in vitro and in vivo models with functional rescue; single lab","pmids":["26275606"],"is_preprint":false},{"year":2016,"finding":"STIM2 is required for stable expression of both LTP and LTD at CA3-CA1 hippocampal synapses. Stim2 cKO mice showed altered dendritic spine density/shape in CA1, reduced surface delivery of GluA1 in response to LTP-inducing stimuli, and impaired GluA1 endocytosis following chemically-induced LTD.","method":"Stim2 conditional KO mice, electrophysiology (LTP and LTD induction), dendritic spine imaging, GluA1 surface trafficking assays","journal":"Neurobiology of learning and memory","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with electrophysiology plus spine morphology plus receptor trafficking; single lab","pmids":["27544849"],"is_preprint":false},{"year":2017,"finding":"STIM2 forms an ER Ca2+-dependent complex with microtubule plus-end binding protein EB3 via a Ser-x-Ile-Pro amino acid motif. Disruption of STIM2-EB3 interaction results in loss of mushroom spines in hippocampal neurons. EB3 overexpression rescues mushroom spine deficiency in PS1-M146V-KI AD neurons and rescues spine loss caused by STIM2 depletion, whereas STIM2 overexpression cannot rescue spines after EB3 knockdown.","method":"Co-immunoprecipitation, STIM2-EB3 interaction domain mapping, EB3 and STIM2 overexpression/knockdown, dendritic spine morphology in hippocampal neurons","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with interaction domain mapping plus epistasis (EB3 downstream of STIM2 for spine maintenance); single lab","pmids":["29247211"],"is_preprint":false},{"year":2018,"finding":"STIM2 is constitutively localized within ER-PM junctions in Ca2+-replete cells and induces the activated conformation of STIM1 by trapping STIM1 and triggering remodeling of STIM1 C-terminus, causing STIM1/Orai1 coupling in cells with relatively high ER-[Ca2+]. This enhancement of Orai1 function controls NFAT activation at low agonist concentrations.","method":"Conformational FRET sensors for STIM1 and STIM2, protein interaction studies, functional Ca2+ entry and NFAT activation assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — FRET-based conformational sensors plus protein interaction and functional studies; single lab, multiple orthogonal methods","pmids":["29642009"],"is_preprint":false},{"year":2018,"finding":"STIM2 interacts directly with AMPK and CaMKK2. Increased intracellular calcium promotes colocalization and interaction of AMPK with STIM2. STIM2 deficiency attenuates calcium-induced but not energy stress-induced AMPK activation, acting as a scaffold for CaMKK2-AMPK signaling.","method":"Co-immunoprecipitation, co-localization microscopy, STIM2 knockout cells, AMPK phosphorylation assays with calcium vs. energy stress stimuli","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus KO with specific stimuli to distinguish calcium vs. energy stress pathways; single lab","pmids":["30335546"],"is_preprint":false},{"year":2018,"finding":"Cross-talk between N-terminal Ca2+-sensing and C-terminal flexibility of STIM2 determines its distinct activation dynamics. The increased flexibility of the STIM2 C-terminus (compared to STIM1) contributes to its selective store-independent activation by 2-APB. STIM1/STIM2 chimeric constructs and the E470G mutation in STIM1 (equivalent to a STIM2 residue) can switch STIM2 from slow/weak to fast/potent Orai channel activator, and vice versa.","method":"CRISPR/Cas9 knockouts, STIM1/STIM2 chimeric constructs, point mutagenesis, FRET-based activity sensors, Ca2+ imaging","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — chimeric protein engineering plus mutagenesis plus FRET sensors plus CRISPR KOs; multiple orthogonal methods in single study","pmids":["30444880"],"is_preprint":false},{"year":2019,"finding":"Cross-talk between N-terminal and C-terminal domains of STIM2 determines its enhanced sensitivity compared to STIM1. The increased flexibility of the STIM2 C-terminus contributes to store-independent activation by 2-APB, but coordination of N-terminal sensitivity with C-terminal flexibility is required for specific STIM2 store-independent activation. STIM1 variants with enhanced C-terminal flexibility alone were insufficient to support store-independent activation.","method":"CRISPR/Cas9 STIM1-/-, STIM2-/-, and STIM1/2-/- knockouts in HEK293 and HCT116 cells, STIM1/STIM2 chimeras, C-terminal stabilizing/disrupting variants, Ca2+ imaging","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — CRISPR KOs plus chimeric constructs plus mutagenesis; multiple cell lines and multiple orthogonal methods","pmids":["30824535"],"is_preprint":false},{"year":2020,"finding":"STIM2 recruits Orai1/STIM1 to the AKAP79 signaling complex at ER-PM junctions, coupling Orai1 Ca2+ entry to NFAT1 activation. STIM2 knockdown had little effect on Orai1/STIM1 clustering or global Ca2+ increases but significantly attenuated NFAT1 activation and AKAP79-Orai1 assembly. The polybasic domain of STIM2 (replacing that of STIM1ΔK) eliminated the requirement of STIM2 for NFAT1 activation.","method":"Co-immunoprecipitation, Ca2+ imaging, NFAT1 nuclear translocation assay, siRNA knockdown, domain-swap mutants (STIM1ΔK, polybasic domain chimeras)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple Co-IPs plus domain-swap mutagenesis plus functional readout; multiple orthogonal methods in single study","pmids":["32601188"],"is_preprint":false},{"year":2020,"finding":"Oxidative stress modifies STIM2 at cysteine 313, the main redox sensor of STIM2. Oxidative modifications of C313 alter STIM2 activation dynamics and hinder STIM2-mediated gating of ORAI1, suppressing SOCE. Mutation of C313 abolishes the oxidative suppression of SOCE. MD simulations indicate C313 oxidation affects the STIM2 activation conformation.","method":"Redox proteomics (in vitro and in vivo), C313 mutagenesis, FLIM/FRET microscopy, patch-clamp, molecular dynamics simulations","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — site-specific mutagenesis plus structural dynamics (FLIM/FRET + MD) plus functional electrophysiology; multiple orthogonal methods","pmids":["33086068"],"is_preprint":false},{"year":2021,"finding":"STIM2 regulates TRPC1 channel activity at partial store depletion conditions. STIM2 overexpression increases both basal TRPC1 activity and number of silent TRPC1 channels at the plasma membrane. After store depletion, STIM2 directly activates TRPC1 even without calcium entry; however, this effect is abrogated by co-expression with non-permeable Orai1 E106Q mutant, indicating Ca2+ entry through Orai triggers TRPC1 activation, while subsequent STIM2-mediated regulation is independent of Ca2+ entry.","method":"Single-channel patch-clamp recordings, Orai1 knockout/knockdown, dominant-negative Orai1 E106Q, STIM2 overexpression","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-channel electrophysiology plus dominant-negative and KO experiments; single lab","pmids":["34157631"],"is_preprint":false},{"year":2022,"finding":"IP3R function and local ER Ca2+ are the main drivers of immobile STIM2 cluster formation at ER-PM junctions under basal conditions. Endogenous STIM2 is constitutively present in mobile and immobile clusters; immobile clusters associate with ER-PM junctions and recruit Orai1 under basal conditions. ER-PM junction formation (via E-Syt2/3) is required but not sufficient for STIM2 clustering. Ambient PIP2-PLC activity determines IP3R function, STIM2 immobilization, and basal Ca2+ entry.","method":"Endogenous STIM2 fluorescent tagging via gene editing, live cell imaging, IP3R functional manipulation, E-Syt2/3 knockout, PLC inhibition, Orai1 recruitment assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous protein tagging plus multiple genetic perturbations plus live imaging; multiple orthogonal methods","pmids":["35022238"],"is_preprint":false},{"year":2024,"finding":"In cardiomyocytes (NRVMs), STIM2 splice variants differentially regulate SOCE: STIM2.1 suppresses Orai1-mediated SOCE while STIM2.2 enhances SOCE also involving TRPC1 and TRPC4. STIM2 is present in mitochondria-associated ER membranes (MAMs) and interacts with IP3Rs, VDAC, MCU, and mitofusin-2. STIM2.1 overexpression abolishes mitochondrial Ca2+ uptake, linking STIM2 to mitochondrial Ca2+ homeostasis.","method":"siRNA knockdown, overexpression of splice variants, SOCE patch-clamp (ISOC), super-resolution confocal microscopy, Rhod-2 mitochondrial Ca2+ imaging, co-immunoprecipitation of MAM complexes","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods including electrophysiology, super-resolution imaging, and co-IP; single lab","pmids":["38537434"],"is_preprint":false},{"year":2023,"finding":"STIM2 regulates NMDA receptor endocytosis in cortical neurons. Short-term NMDAR overactivation increased STIM2-GluN2A and STIM2-GluN2B interactions. STIM2 silencing inhibited post-activation NMDAR translocation from the plasma membrane and synaptic spines and increased NMDAR currents, suggesting STIM2 promotes NMDAR endocytosis after overactivation to protect against excessive Ca2+ influx.","method":"Co-immunoprecipitation, STIM2 siRNA silencing, NMDAR current measurements, NMDAR surface trafficking assays, immunofluorescence in primary cortical neurons","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus functional silencing with electrophysiology and trafficking readouts; single lab","pmids":["37989792"],"is_preprint":false},{"year":2023,"finding":"ORAI3 and STIM2 interact under basal conditions in PC-3 prostate cancer cells. STIM2 expression increases during M phase while STIM1 expression and SOCE amplitude decrease. The ORAI3-STIM2 complex allows successful progression through mitosis by preventing mitotic catastrophe; ORAI3 silencing increased SOCE and induced mitotic arrest-related death.","method":"Co-immunoprecipitation of ORAI3-STIM2, cell cycle synchronization, SOCE measurements, cell death assays","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus cell cycle-synchronized functional assays; single lab","pmids":["37597301"],"is_preprint":false},{"year":2025,"finding":"STIM2 loss in colorectal cancer cells causes SERCA2-dependent increase in ER Ca2+ content, transcriptional and metabolic rewiring, and activates the ATF4/BiP ER stress response pathway independently of Orai channels. STIM2-deficient CRC xenografts showed increased tumor size, invasion, and metastasis.","method":"CRISPR/shRNA STIM2 loss-of-function, xenograft tumor models, SERCA2 rescue experiments, ER Ca2+ measurements, transcriptomic analysis, Orai-independent ER stress pathway assessment","journal":"Science signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus in vivo xenograft plus rescue experiments; single lab, multiple methods","pmids":["40554601"],"is_preprint":false},{"year":2025,"finding":"In hippocampal neurons, a substantial fraction of STIM2 (but not STIM1) defines ER-PM contacts under resting conditions and is dependent on constitutive NMDAR activity. STIM1 is only transiently recruited to ER-PM junctions during strong NMDAR activation. STIM2 clusters are not enriched at KV2.1-organized junctions, and their activity-dependent confinement is independent of CaV1.2 activity.","method":"Single-particle tracking of endogenous STIM1 and STIM2, pharmacological NMDAR and CaV1.2 manipulation, live cell imaging in hippocampal neurons","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-particle tracking of endogenous proteins with pharmacological dissection; single lab","pmids":["40966085"],"is_preprint":false},{"year":2012,"finding":"STIM2, but not STIM1, is required for TRPC2-independent regulation of basal Ca2+ entry in rat thyroid FRTL-5 cells. Knockdown of TRPC2 causes STIM2 to arrange into puncta in resting cells (not seen in controls) and enhances basal Ca2+ entry. PKCδ knockdown mimics TRPC2 loss by increasing STIM2 punctum formation. Basal Ca2+ entry in TRPC2-knockdown cells is dependent on Orai1.","method":"shRNA knockdown of TRPC2, siRNA knockdown of PKCδ, immunofluorescence (STIM2 puncta), Ca2+ imaging, Orai1 mutant expression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic knockdowns plus localization and functional assays; single lab","pmids":["23144458"],"is_preprint":false}],"current_model":"STIM2 is an ER-resident Ca2+ sensor with a lower activation threshold than STIM1 that constitutively occupies ER-PM junctions where, upon mild ER Ca2+ depletion driven by IP3R activity, it recruits STIM1 and Orai1 to stabilize basal cytosolic and ER Ca2+ concentrations; it also forms heterodimers with STIM1 to modulate Orai1 gating and NFAT activation, activates non-CRAC channels (TRPC1, Imin), is subject to inhibitory redox modification at Cys313 and alternative splicing (STIM2.1/β isoform inhibits via calmodulin binding and impaired Orai1 interaction), interacts with AMPK/CaMKK2 to scaffold calcium-dependent energy sensing, and in neurons additionally regulates dendritic spine stability through the nSOC-CaMKII axis, EB3 association, and AMPAR/NMDAR trafficking."},"narrative":{"mechanistic_narrative":"STIM2 is an ER-resident Ca2+ sensor that functions as the principal feedback regulator stabilizing basal cytosolic and ER Ca2+ levels by activating Ca2+ influx through Orai1 in response to smaller ER Ca2+ decreases than those required for STIM1 [PMID:18160041]. Its lower activation threshold derives from biophysical and conformational distinctions: its EF-SAM domain is more structurally stable than that of STIM1 [PMID:18166150], and a cross-talk between N-terminal Ca2+ sensing and increased C-terminal flexibility tunes its slow/weak versus fast/potent gating of Orai, switchable by STIM1/STIM2 chimeras and point mutations [PMID:30444880, PMID:30824535]. Mechanistically, STIM2 is constitutively localized at ER-PM junctions in Ca2+-replete cells, where IP3R activity and local ER Ca2+ drive formation of immobile clusters that recruit Orai1 under basal conditions [PMID:29642009, PMID:35022238]. Upon mild store depletion it traps STIM1 and remodels its C-terminus to induce the active conformation, enhancing Orai1 coupling and NFAT activation at low agonist concentrations [PMID:29642009, PMID:25587190], and it scaffolds Orai1/STIM1 to the AKAP79 complex to couple Ca2+ entry to NFAT1 [PMID:32601188]. STIM2 physically interacts with STIM1 and forms heteromers that modulate SOCE [PMID:16860747, PMID:20436167, PMID:22592407]. Beyond CRAC channels, STIM2 differentially regulates non-CRAC store-operated channels including Imin and TRPC1 [PMID:25533457, PMID:34157631]. Its activity is negatively controlled by oxidative modification at Cys313 [PMID:33086068] and by alternative splicing: the STIM2.1/β isoform inhibits SOCE through increased calmodulin affinity, impaired direct Orai1 interaction, and allosteric inhibition via heterodimer recruitment to Orai1 [PMID:25896806, PMID:26033257]. STIM2 is required for store-operated Ca2+ entry and NFAT-dependent cytokine production in T cells [PMID:18327260], and is essential for capacitive Ca2+ entry and ischemia-induced neuronal Ca2+ accumulation, such that its loss is neuroprotective in cerebral ischemia [PMID:19843959]. In neurons it stabilizes mushroom dendritic spines through a neuronal SOC–CaMKII axis that is compromised in Alzheimer's disease models [PMID:24698269, PMID:26275606], acts through an ER Ca2+-dependent complex with the microtubule plus-end protein EB3 [PMID:29247211], and controls AMPAR (GluA1) and NMDAR trafficking to regulate synaptic plasticity [PMID:25609091, PMID:27544849, PMID:37989792]. STIM2 additionally scaffolds CaMKK2-AMPK to mediate calcium-dependent energy sensing [PMID:30335546].","teleology":[{"year":2006,"claim":"Established that STIM2 is functionally and spatially distinct from STIM1, acting as an intracellular inhibitor of STIM1-mediated store-operated Ca2+ entry that physically partners with STIM1.","evidence":"Overexpression, immunofluorescence localization, reciprocal co-IP and Ca2+ entry assays across multiple cell lines","pmids":["16860747"],"confidence":"High","gaps":["Did not resolve the threshold difference quantitatively","Step of inhibition downstream of puncta formation left mechanistically undefined"]},{"year":2007,"claim":"Defined STIM2's core physiological role as a feedback sensor that stabilizes basal Ca2+ by responding to smaller ER depletions than STIM1, answering why two STIM paralogs exist.","evidence":"Genome-wide siRNA screen of signaling proteome plus Ca2+ imaging and rescue assays","pmids":["18160041"],"confidence":"High","gaps":["Molecular basis of the lower threshold not established","Did not address tissue-specific roles"]},{"year":2007,"claim":"Provided a biophysical basis for STIM2's distinct activation by showing its EF-SAM domain, despite similar Ca2+ affinity, is more stable and aggregation-resistant than STIM1.","evidence":"CD spectroscopy and aggregation assays on recombinant EF-SAM domains in vitro","pmids":["18166150"],"confidence":"High","gaps":["In vitro domain behavior not directly linked to full-length cellular gating","Did not test C-terminal contributions"]},{"year":2007,"claim":"Demonstrated STIM2 activates CRAC channels through both store-operated and store-independent modes under calmodulin control, expanding its regulatory repertoire.","evidence":"Whole-cell patch-clamp with calmodulin inhibitors, 2-APB, and G418 pharmacology","pmids":["17905723"],"confidence":"High","gaps":["CaM binding site not mapped","Physiological trigger of store-independent mode unclear"]},{"year":2008,"claim":"Established in vivo that STIM2 is required, alongside STIM1, for NFAT-dependent cytokine production and immune homeostasis in T cells.","evidence":"Conditional knockout mice with Ca2+ imaging, NFAT translocation, flow cytometry and cytokine readouts","pmids":["18327260"],"confidence":"High","gaps":["Relative contribution at physiological agonist levels not dissected","Mechanism of NFAT coupling not yet resolved"]},{"year":2009,"claim":"Showed STIM2-specific control of neuronal capacitive Ca2+ entry has pathological consequences, with STIM2 loss conferring neuroprotection in ischemia.","evidence":"Stim2 knockout mice, neuronal Ca2+ imaging, hippocampal slices and in vivo focal cerebral ischemia","pmids":["19843959"],"confidence":"High","gaps":["Downstream effectors of ischemic Ca2+ accumulation not identified","Channel composition mediating neuronal CCE not defined"]},{"year":2010,"claim":"Confirmed dynamic STIM1-STIM2 physical interaction during SOCE activation and their joint requirement in muscle Ca2+ handling and differentiation.","evidence":"FRET live imaging, endogenous reciprocal co-IP, siRNA and myoblast differentiation assays in human myotubes","pmids":["20436167"],"confidence":"High","gaps":["Stoichiometry of heteromers not determined","Functional consequence of heteromerization on gating not quantified"]},{"year":2011,"claim":"Extended STIM2 localization and interaction networks to acidic Ca2+ stores and platelet contexts, linking it to Orai1, TRPC and SERCA3.","evidence":"Organelle fractionation, co-IP and Ca2+ imaging with bafilomycin A1 in human platelets","pmids":["21321120"],"confidence":"Medium","gaps":["Direct vs indirect associations not distinguished","Single-lab subcellular fractionation"]},{"year":2011,"claim":"Showed STIM2/Orai1 complexes preferentially govern resting ER Ca2+ and leak in neurons, pharmacologically separable from STIM1/Orai1 SOCE.","evidence":"Subcellular fractionation, YFP-STIM overexpression, Fura-2 imaging and SOCE inhibitors in rat cortical neurons","pmids":["21541286"],"confidence":"Medium","gaps":["Overexpression-based, endogenous behavior less defined","Basis of differential inhibitor sensitivity unexplained"]},{"year":2011,"claim":"Revealed a non-canonical cytosolic preSTIM2 from inefficient signal peptide cleavage that regulates basal Ca2+ and transcription store-independently.","evidence":"Signal peptide mutagenesis, fractionation, co-IP with ORAI1 and transcription reporter assays","pmids":["21383014"],"confidence":"Medium","gaps":["Physiological abundance of preSTIM2 unclear","Mechanism of plasma-membrane targeting not fully defined"]},{"year":2012,"claim":"Linked STIM1/STIM2 ratio to physiological cell migration, showing STIM2 heteromers suppress STIM1 translocation and TRPC1-mediated influx.","evidence":"ODC manipulation of polyamines, STIM1/STIM2 co-IP, Ca2+ imaging and wound-healing migration assays","pmids":["22592407"],"confidence":"Medium","gaps":["Direct transcriptional vs post-translational control by polyamines not separated","Single-system epithelial context"]},{"year":2012,"claim":"Demonstrated STIM2-specific control of basal Orai1-dependent Ca2+ entry gated by TRPC2 and PKCδ in thyroid cells.","evidence":"TRPC2 shRNA, PKCδ siRNA, STIM2 puncta imaging, Ca2+ imaging and Orai1 mutant expression in FRTL-5 cells","pmids":["23144458"],"confidence":"Medium","gaps":["Mechanism by which TRPC2/PKCδ restrains STIM2 clustering unknown","Single cell type"]},{"year":2013,"claim":"Established that STIM2 preferentially mediates SOCE and Ca2+ oscillations under mild, physiological store depletion without engaging STIM1-dependent responses.","evidence":"siRNA, G418 inhibition and Ca2+ oscillation measurements across mast cells, T cells and HEK293; endogenous PLA/co-IP of STIM2-ORAI1 in neurons","pmids":["23359669","23711249"],"confidence":"Medium","gaps":["Quantitative depletion threshold not defined","Single-lab studies"]},{"year":2014,"claim":"Distinguished STIM2 from STIM1 in regulating non-CRAC Imin and TRPC channels, showing the active STIM2/STIM1 ratio switches channel modes.","evidence":"Single-channel patch-clamp with selective STIM1/STIM2 activation in native HEK293 cells","pmids":["25533457"],"confidence":"Medium","gaps":["Molecular determinants of channel selectivity not mapped","Single lab"]},{"year":2014,"claim":"Defined a neuronal STIM2-nSOC-CaMKII axis essential for mushroom spine stability and showed its disruption underlies spine loss in Alzheimer's models.","evidence":"PS1-M146V knockin mice, spine morphology, Ca2+ imaging, CaMKII assays and STIM2 overexpression rescue","pmids":["24698269","26275606"],"confidence":"High","gaps":["Channel composition of synaptic nSOC not fully defined","Link between STIM2 downregulation and amyloid pathology causality incomplete"]},{"year":2015,"claim":"Identified STIM2.1/STIM2β splice isoform as a dominant inhibitor of SOCE acting via calmodulin and impaired/allosteric Orai1 interaction recruited through heterodimers.","evidence":"Reciprocal siRNA knockdown in T cells, Orai1 co-IP, calmodulin binding, mutagenesis and Orai1-STIM2β chimeras","pmids":["25896806","26033257"],"confidence":"High","gaps":["Regulation of splice-isoform ratio in vivo not established","Structural basis of allosteric inhibition not resolved"]},{"year":2015,"claim":"Showed STIM2 promotes STIM1 clustering at ER-PM junctions at low stimulus intensity in vivo, with C-terminal residues required for recruitment and secretory function.","evidence":"Conditional STIM2 deletion in salivary glands, C-terminal deletion mutants, live STIM1 puncta imaging and NFAT assays","pmids":["25587190"],"confidence":"High","gaps":["Exact recruitment interface not defined","How threshold integrates with STIM1 polybasic domain unclear"]},{"year":2015,"claim":"Uncovered a SOCE-independent neuronal function: STIM2 couples PKA to AMPAR GluA1, controlling its phosphorylation and surface trafficking.","evidence":"STIM2 KO neurons, biochemical PKA phosphorylation assays, live imaging and GluA1 surface trafficking assays","pmids":["25609091"],"confidence":"Medium","gaps":["Direct STIM2-PKA-GluA1 binding architecture not defined","Single lab"]},{"year":2016,"claim":"Established STIM2 as required for stable LTP and LTD via control of GluA1 trafficking, connecting its synaptic role to plasticity.","evidence":"Stim2 conditional KO mice, LTP/LTD electrophysiology, spine imaging and GluA1 trafficking assays","pmids":["27544849"],"confidence":"Medium","gaps":["Whether plasticity defect is SOCE-dependent not separated","Behavioral consequences not assessed here"]},{"year":2017,"claim":"Identified an ER Ca2+-dependent STIM2-EB3 complex acting downstream of STIM2 to maintain mushroom spines, placing microtubule dynamics in the pathway.","evidence":"Co-IP, interaction-motif mapping, epistasis via EB3/STIM2 overexpression and knockdown in hippocampal neurons","pmids":["29247211"],"confidence":"Medium","gaps":["How EB3 enacts spine maintenance downstream not defined","Single lab"]},{"year":2018,"claim":"Resolved the mechanism of STIM2's threshold advantage: it is constitutive at ER-PM junctions and traps/remodels STIM1 to drive Orai1 coupling and NFAT at high ER-Ca2+.","evidence":"Conformational FRET sensors for STIM1/STIM2, interaction and functional Ca2+/NFAT assays","pmids":["29642009"],"confidence":"High","gaps":["Trapping interface not structurally defined","Quantitative occupancy at junctions not measured"]},{"year":2018,"claim":"Defined the structural determinant of STIM2's distinct dynamics as cross-talk between N-terminal sensing and C-terminal flexibility, switchable by chimeras and single residues.","evidence":"CRISPR KOs, STIM1/STIM2 chimeras, E470G mutation, FRET sensors and Ca2+ imaging across HEK293/HCT116","pmids":["30444880","30824535"],"confidence":"High","gaps":["High-resolution structure of the activating conformation not solved","How redox and splicing intersect with C-terminal flexibility not unified"]},{"year":2018,"claim":"Revealed a SOCE-independent metabolic role: STIM2 scaffolds CaMKK2-AMPK to selectively mediate calcium-induced AMPK activation.","evidence":"Co-IP, colocalization, STIM2 KO cells and AMPK phosphorylation under calcium vs energy stress","pmids":["30335546"],"confidence":"Medium","gaps":["Direct binding regions not mapped","Physiological metabolic outputs not characterized"]},{"year":2020,"claim":"Showed STIM2 selectively couples Orai1 Ca2+ entry to NFAT1 by recruiting the channel to the AKAP79 complex through its polybasic domain, independent of bulk clustering.","evidence":"Co-IP, Ca2+ imaging, NFAT1 translocation, siRNA and polybasic domain-swap mutants","pmids":["32601188"],"confidence":"High","gaps":["How AKAP79 selectivity is achieved over STIM1 not fully defined","Single lab"]},{"year":2020,"claim":"Identified Cys313 as STIM2's main redox sensor, providing a mechanism by which oxidative stress suppresses STIM2-mediated Orai1 gating.","evidence":"Redox proteomics, C313 mutagenesis, FLIM/FRET, patch-clamp and MD simulations","pmids":["33086068"],"confidence":"High","gaps":["In vivo physiological redox triggers not defined","Interplay with splice isoform inhibition unexplored"]},{"year":2021,"claim":"Clarified STIM2's regulation of TRPC1, showing Orai-mediated Ca2+ entry initiates TRPC1 activation while subsequent STIM2 regulation is Ca2+-entry-independent.","evidence":"Single-channel patch-clamp, Orai1 KO/knockdown and dominant-negative Orai1 E106Q with STIM2 overexpression","pmids":["34157631"],"confidence":"Medium","gaps":["Direct STIM2-TRPC1 interface not mapped","Overexpression-based, single lab"]},{"year":2022,"claim":"Established the upstream logic of basal STIM2 clustering: IP3R-driven local ER Ca2+, set by PIP2-PLC activity, immobilizes endogenous STIM2 at ER-PM junctions to recruit Orai1.","evidence":"Endogenous STIM2 gene-edited tagging, live imaging, IP3R manipulation, E-Syt2/3 KO, PLC inhibition and Orai1 recruitment assays","pmids":["35022238"],"confidence":"High","gaps":["Molecular link between local Ca2+ and immobilization not defined","Generalizability beyond the studied cell type"]},{"year":2023,"claim":"Extended STIM2 partnerships to ORAI3 in mitosis, where the basal ORAI3-STIM2 complex restrains SOCE to permit mitotic progression in prostate cancer cells.","evidence":"Co-IP, cell-cycle synchronization, SOCE measurements and cell death assays in PC-3 cells","pmids":["37597301"],"confidence":"Medium","gaps":["Mechanism of cell-cycle-dependent STIM2/STIM1 switch unclear","Single cell line"]},{"year":2023,"claim":"Showed STIM2 promotes NMDAR endocytosis after overactivation, providing a neuroprotective brake on excessive Ca2+ influx.","evidence":"Co-IP of STIM2-GluN2A/GluN2B, STIM2 silencing, NMDAR currents and surface trafficking in cortical neurons","pmids":["37989792"],"confidence":"Medium","gaps":["Direct vs adaptor-mediated NMDAR interaction not resolved","Single lab"]},{"year":2024,"claim":"Connected STIM2 splice variants to mitochondrial Ca2+ homeostasis via MAM-localized complexes, with STIM2.1 abolishing mitochondrial Ca2+ uptake.","evidence":"siRNA, splice-variant overexpression, ISOC patch-clamp, super-resolution imaging, Rhod-2 imaging and MAM co-IPs in cardiomyocytes","pmids":["38537434"],"confidence":"Medium","gaps":["Direct interaction partners within MAM not validated reciprocally","Single lab, cardiomyocyte-specific"]},{"year":2025,"claim":"Revealed an Orai-independent tumor-suppressive function: STIM2 loss raises ER Ca2+ via SERCA2, rewires metabolism and triggers the ATF4/BiP ER stress pathway, promoting CRC progression.","evidence":"CRISPR/shRNA loss-of-function, xenografts, SERCA2 rescue, ER Ca2+ and transcriptomic analyses","pmids":["40554601"],"confidence":"Medium","gaps":["Mechanism by which STIM2 restrains SERCA2 not defined","Single lab"]},{"year":2025,"claim":"Showed that resting ER-PM contact definition by STIM2 in neurons depends on constitutive NMDAR activity, distinguishing STIM2 from transiently recruited STIM1.","evidence":"Single-particle tracking of endogenous STIM1/STIM2 with NMDAR and CaV1.2 pharmacology in hippocampal neurons","pmids":["40966085"],"confidence":"Medium","gaps":["Molecular coupling between NMDAR activity and STIM2 confinement unknown","Single lab"]},{"year":null,"claim":"How STIM2's various regulatory inputs — redox modification, alternative splicing, calmodulin, C-terminal flexibility, and junctional scaffolding partners — are integrated structurally to set its activation threshold and channel selectivity remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of the active STIM2 conformation or STIM2-Orai1 interface","Quantitative integration of splice/redox/CaM inputs not modeled","In vivo physiological triggers distinguishing STIM2 from STIM1 incompletely defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[0,2,11,22,29]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,22,24]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,15,16,27,28]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[22,23,26]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,1,22,29]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[9,17,22,29,34]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[30]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,22,26]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,4,17]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[13,18,20,31]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[27,33]}],"complexes":["STIM1-STIM2 heteromer","STIM2-Orai1 complex","AKAP79-Orai1-STIM signaling complex","MAM Ca2+ complex (IP3R/VDAC/MCU/mitofusin-2)"],"partners":["STIM1","ORAI1","EB3","AMPK","CAMKK2","AKAP79","TRPC1","ORAI3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9P246","full_name":"Stromal interaction molecule 2","aliases":[],"length_aa":746,"mass_kda":84.0,"function":"Plays a role in mediating store-operated Ca(2+) entry (SOCE), a Ca(2+) influx following depletion of intracellular Ca(2+) stores. Functions as a highly sensitive Ca(2+) sensor in the endoplasmic reticulum which activates both store-operated and store-independent Ca(2+)-influx. Regulates basal cytosolic and endoplasmic reticulum Ca(2+) concentrations. Upon mild variations of the endoplasmic reticulum Ca(2+) concentration, translocates from the endoplasmic reticulum to the plasma membrane where it probably activates the Ca(2+) release-activated Ca(2+) (CRAC) channels ORAI1, ORAI2 and ORAI3. May inhibit STIM1-mediated Ca(2+) influx","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q9P246/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/STIM2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000109689","cell_line_id":"CID001890","localizations":[{"compartment":"er","grade":3},{"compartment":"membrane","grade":1},{"compartment":"vesicles","grade":1}],"interactors":[{"gene":"STIM1","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID001890","total_profiled":1310},"omim":[{"mim_id":"617189","title":"TRANSMEMBRANE PROTEIN 110; TMEM110","url":"https://www.omim.org/entry/617189"},{"mim_id":"610841","title":"STROMAL INTERACTION MOLECULE 2; STIM2","url":"https://www.omim.org/entry/610841"},{"mim_id":"610277","title":"ORAI CALCIUM RELEASE-ACTIVATED CALCIUM MODULATOR 1; ORAI1","url":"https://www.omim.org/entry/610277"},{"mim_id":"605921","title":"STROMAL INTERACTION MOLECULE 1; STIM1","url":"https://www.omim.org/entry/605921"},{"mim_id":"185070","title":"STORMORKEN SYNDROME; STRMK","url":"https://www.omim.org/entry/185070"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"choroid plexus","ntpm":59.3}],"url":"https://www.proteinatlas.org/search/STIM2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9P246","domains":[{"cath_id":"1.10.150.50","chopping":"64-210","consensus_level":"high","plddt":85.0346,"start":64,"end":210},{"cath_id":"1.10.287.3550","chopping":"350-462","consensus_level":"high","plddt":85.9112,"start":350,"end":462}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P246","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P246-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P246-F1-predicted_aligned_error_v6.png","plddt_mean":65.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=STIM2","jax_strain_url":"https://www.jax.org/strain/search?query=STIM2"},"sequence":{"accession":"Q9P246","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P246.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P246/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P246"}},"corpus_meta":[{"pmid":"18160041","id":"PMC_18160041","title":"STIM2 is a feedback regulator that stabilizes basal cytosolic and endoplasmic reticulum Ca2+ levels.","date":"2007","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/18160041","citation_count":593,"is_preprint":false},{"pmid":"18327260","id":"PMC_18327260","title":"Dual functions for the endoplasmic reticulum calcium sensors STIM1 and STIM2 in T cell activation and tolerance.","date":"2008","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/18327260","citation_count":501,"is_preprint":false},{"pmid":"24698269","id":"PMC_24698269","title":"Reduced synaptic STIM2 expression and impaired store-operated calcium entry cause destabilization of mature spines in mutant presenilin mice.","date":"2014","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/24698269","citation_count":234,"is_preprint":false},{"pmid":"19843959","id":"PMC_19843959","title":"STIM2 regulates capacitive Ca2+ entry in neurons and plays a key role in hypoxic neuronal cell death.","date":"2009","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/19843959","citation_count":229,"is_preprint":false},{"pmid":"21530328","id":"PMC_21530328","title":"The calcium sensors STIM1 and STIM2 control B cell regulatory function through interleukin-10 production.","date":"2011","source":"Immunity","url":"https://pubmed.ncbi.nlm.nih.gov/21530328","citation_count":221,"is_preprint":false},{"pmid":"16860747","id":"PMC_16860747","title":"STIM2 is an inhibitor of STIM1-mediated store-operated Ca2+ Entry.","date":"2006","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/16860747","citation_count":210,"is_preprint":false},{"pmid":"18166150","id":"PMC_18166150","title":"Biophysical characterization of the EF-hand and SAM domain containing Ca2+ sensory region of STIM1 and STIM2.","date":"2007","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/18166150","citation_count":135,"is_preprint":false},{"pmid":"17905723","id":"PMC_17905723","title":"STIM2 protein mediates distinct store-dependent and store-independent modes of CRAC channel activation.","date":"2007","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/17905723","citation_count":134,"is_preprint":false},{"pmid":"21541286","id":"PMC_21541286","title":"Differential roles for STIM1 and STIM2 in store-operated calcium entry in rat neurons.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21541286","citation_count":120,"is_preprint":false},{"pmid":"25896806","id":"PMC_25896806","title":"A STIM2 splice variant negatively regulates store-operated calcium entry.","date":"2015","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/25896806","citation_count":108,"is_preprint":false},{"pmid":"21061435","id":"PMC_21061435","title":"T-cell-specific deletion of STIM1 and STIM2 protects mice from EAE by impairing the effector functions of Th1 and Th17 cells.","date":"2010","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/21061435","citation_count":106,"is_preprint":false},{"pmid":"25673771","id":"PMC_25673771","title":"Upregulated expression of STIM2, TRPC6, and Orai2 contributes to the transition of pulmonary arterial smooth muscle cells from a contractile to proliferative phenotype.","date":"2015","source":"American journal of physiology. 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\"method\": \"siRNA screen of human signaling proteome, Ca2+ imaging, functional rescue assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic siRNA screen plus functional Ca2+ measurements; independently replicated across multiple subsequent studies\",\n      \"pmids\": [\"18160041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"STIM2 acts as an inhibitor of STIM1-mediated store-operated Ca2+ entry (SOC). STIM2 is expressed only intracellularly (not at plasma membrane unlike STIM1), translocates into puncta upon store depletion only when coexpressed with STIM1, co-localizes with STIM1 in puncta, and physically interacts with STIM1 by co-immunoprecipitation. STIM2 inhibits SOCE at a step downstream of puncta formation.\",\n      \"method\": \"Overexpression in HEK293/PC12/A7r5/Jurkat cells, subcellular localization by immunofluorescence, co-immunoprecipitation, functional Ca2+ entry assays\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, localization studies, functional assays in multiple cell lines; findings replicated by multiple subsequent studies\",\n      \"pmids\": [\"16860747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Biophysical characterization of STIM2 EF-SAM domain reveals a Ca2+-binding affinity (Kd ~0.5 mM) similar to STIM1, but apo-STIM2 EF-SAM is more structurally stable and does not readily aggregate compared to apo-STIM1 EF-SAM, which may account for STIM2's distinct functional properties and lower activation threshold.\",\n      \"method\": \"CD spectroscopy, biophysical characterization of recombinant EF-SAM domain in vitro\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with direct biophysical measurements on purified domain; single lab but multiple methods (CD, aggregation assays)\",\n      \"pmids\": [\"18166150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"STIM2 activates CRAC channels via two distinct modes: a store-operated mode triggered by ER Ca2+ depletion via IP3, and a store-independent mode activated by cell dialysis during whole-cell patch-clamp. Both modes are regulated by calmodulin (CaM); CaM inhibition can be reversed by 2-APB. The aminoglycoside antibiotic G418 specifically and potently inhibits STIM2-dependent CRAC channel activation.\",\n      \"method\": \"Whole-cell patch-clamp, Ca2+ imaging, pharmacological manipulation with calmodulin inhibitors and 2-APB, G418 treatment\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — electrophysiological recordings plus pharmacological dissection; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"17905723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"STIM2 deficiency in mouse T cells and fibroblasts results in a smaller impairment of store-operated Ca2+ influx compared to STIM1 deficiency, but both STIM1 and STIM2 are required for cytokine production and nuclear translocation of NFAT. T cell-specific deletion of both STIM1 and STIM2 causes lymphoproliferative phenotype and reduced regulatory T cell numbers.\",\n      \"method\": \"Conditional knockout mice, Ca2+ imaging, NFAT nuclear translocation assays, flow cytometry, cytokine measurement\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple orthogonal readouts; replicated by multiple subsequent studies\",\n      \"pmids\": [\"18327260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"STIM2, but not STIM1, is essential for capacitive Ca2+ entry (CCE) and ischemia-induced cytosolic Ca2+ accumulation in neurons. Neurons from Stim2-/- mice showed increased survival under hypoxic conditions in culture and in acute hippocampal slices, and Stim2-/- mice were protected from neurological damage in focal cerebral ischemia in vivo.\",\n      \"method\": \"Stim2 knockout mice, Ca2+ imaging in neurons, hippocampal slice preparations, focal cerebral ischemia model in vivo\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with both in vitro and in vivo phenotypic readouts; STIM1 vs STIM2 specificity tested\",\n      \"pmids\": [\"19843959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"STIM1 and STIM2 interact physically (FRET between CFP-STIM1 and YFP-STIM2 increases upon SOCE activation; confirmed by co-immunoprecipitation of endogenous proteins), both contribute to SOCE and myoblast differentiation, and both are required for ER Ca2+ refilling during excitation-contraction coupling in human myotubes. The two proteins co-localize into clusters during SOCE activation.\",\n      \"method\": \"FRET live cell imaging, co-immunoprecipitation of endogenous proteins, siRNA silencing, Ca2+ imaging, myoblast differentiation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET plus reciprocal co-IP of endogenous proteins plus functional assays; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20436167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"STIM1 and STIM2 are localized in acidic Ca2+ stores (lysosome-related organelles and dense granules) in human platelets. Depletion of acidic Ca2+ stores enhances STIM1-STIM2 association, association of both with Orai1, co-immunoprecipitation of STIM1 with hTRPC1 and hTRPC6, and association of Orai1 with TRPC proteins. Depletion also enhances STIM2-SERCA3 association.\",\n      \"method\": \"Immunomagnetic sorting of organelle fractions, co-immunoprecipitation, Ca2+ imaging with bafilomycin A1 (vacuolar H+-ATPase inhibitor)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — subcellular fractionation and co-IP; single lab, multiple interaction partners tested\",\n      \"pmids\": [\"21321120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In rat cortical neurons, thapsigargin-induced ER store depletion redistributes endogenous STIM1 and STIM2 to membrane fractions and increases STIM1/ORAI1 and STIM2/ORAI1 complexes. STIM1/ORAI1 mainly activates SOCE, whereas STIM2/ORAI1 regulates resting ER Ca2+ levels and Ca2+ leakage; SOCE inhibitors ML-9 and 2-APB affect STIM1/ORAI1 but not STIM2/ORAI1.\",\n      \"method\": \"Subcellular fractionation, YFP-STIM overexpression, Ca2+ imaging with Fura-2, pharmacological inhibitors\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — membrane fractionation plus functional Ca2+ assays; single lab, multiple methods\",\n      \"pmids\": [\"21541286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A cytosolic preSTIM2 protein is produced by inefficient signal peptide cleavage. This preSTIM2 localizes to the inner leaflet of the plasma membrane where it interacts with ORAI1 to regulate basal Ca2+ concentration and Ca2+-dependent gene transcription in a store-independent manner. A third peptide fragment from the STIM2 signal peptide is released into cytosol and regulates gene transcription in a Ca2+-independent manner.\",\n      \"method\": \"Signal peptide mutagenesis, subcellular fractionation, co-immunoprecipitation with ORAI1, Ca2+ imaging, transcription reporter assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of signal peptide plus localization and functional studies; single lab, multiple methods\",\n      \"pmids\": [\"21383014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Polyamines regulate intestinal epithelial restitution by altering the STIM1/STIM2 ratio. Increased polyamines stimulate STIM1 but inhibit STIM2 expression, while polyamine depletion decreases STIM1 and increases STIM2. Induced STIM1/STIM2 heteromers (by polyamine depletion or STIM2 overexpression) suppress STIM1 membrane translocation, reduce TRPC1-mediated Ca2+ influx, and inhibit cell migration.\",\n      \"method\": \"ODC overexpression, ODC inhibitor treatment, co-immunoprecipitation of STIM1/STIM2 complexes, Ca2+ imaging, cell migration wound-healing assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP of STIM1/STIM2 heteromers plus functional migration assays; single lab\",\n      \"pmids\": [\"22592407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Endogenous STIM2 forms a calcium-sensitive, thapsigargin-insensitive complex with ORAI1 in cortical neurons. The number of STIM2-ORAI1 complexes increases when intracellular Ca2+ is decreased by BAPTA-AM or low-calcium medium but does not increase with thapsigargin. This indicates that small drops in ER Ca2+ (triggered by decreased intracellular Ca2+) are sufficient to initiate STIM2-ORAI1 complex formation in neurons.\",\n      \"method\": \"Co-immunoprecipitation, Proximity Ligation Assay (PLA), Ca2+ imaging with Fura-2\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — endogenous protein PLA plus co-IP plus functional Ca2+ imaging; single lab\",\n      \"pmids\": [\"23711249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"STIM2 drives Ca2+ oscillations in mast cells, T cells, and HEK293 cells by mediating store-operated Ca2+ entry at low levels of store depletion (mild ER Ca2+ reduction). siRNA silencing of STIM2 or inhibition by G418 suppresses SOCE and Ca2+ oscillations at low agonist concentrations without interfering with STIM1-mediated signals at full store depletion, indicating STIM2 is preferentially activated by physiological low-level stimulation.\",\n      \"method\": \"siRNA silencing, G418 pharmacological inhibition, Ca2+ oscillation measurements in multiple cell types\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA plus pharmacological inhibition in multiple cell types; single lab\",\n      \"pmids\": [\"23359669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"STIM2-mediated neuronal store-operated Ca2+ influx (nSOC) is required for stabilization of mushroom dendritic spines in hippocampal neurons through continuous activation of CaMKII. The STIM2-nSOC-CaMKII pathway is compromised in PS1-M146V knockin AD neurons, aging neurons, and sporadic AD brains due to STIM2 downregulation. STIM2 overexpression rescues synaptic nSOC, CaMKII activity, and mushroom spine loss.\",\n      \"method\": \"PS1 knockin mouse model, spine morphology analysis, Ca2+ imaging, CaMKII activity assay, STIM2 overexpression rescue\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic model plus functional rescue with multiple orthogonal readouts (Ca2+ imaging, CaMKII activity, spine morphology); replicated in subsequent papers\",\n      \"pmids\": [\"24698269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"STIM2 in native HEK293 cells specifically regulates endogenous non-CRAC Imin channels (a store-operated channel distinct from CRAC), whereas STIM1 blocks Imin channel activation. Changes in the ratio of active STIM2 to STIM1 can switch Imin channel regulation between store-operated and store-independent modes. STIM1 and STIM2 also differ in regulation of other channels: TRPC3-containing INS channels are induced by STIM1, and TRPC1-composed Imax channels are activated by both.\",\n      \"method\": \"Single-channel patch-clamp recordings, STIM1/STIM2 selective activation, overexpression studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-channel electrophysiology with selective activation; single lab\",\n      \"pmids\": [\"25533457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"STIM2.1, an alternatively spliced isoform retaining an additional exon in the channel-activating domain region, is an inhibitor of SOCE. STIM2.1 shows impaired interaction with Orai1 and prevents Orai1 activation, but shows increased affinity towards calmodulin compared to STIM2.2. Knockdown of STIM2.1 increases SOCE in naive CD4+ T cells while STIM2.2 knockdown decreases SOCE.\",\n      \"method\": \"siRNA knockdown in naive T cells, Orai1 co-immunoprecipitation, calmodulin binding assays, Ca2+ imaging\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal knockdown with opposite SOCE phenotypes, plus binding studies; single lab, multiple methods\",\n      \"pmids\": [\"25896806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"STIM2β (equivalent to STIM2.1), a conserved alternatively spliced isoform of STIM2, is a potent inhibitor of SOCE. Although STIM2β does not strongly bind Orai1 by itself, it is recruited to Orai1 channels by forming heterodimers with other STIM isoforms. Mutational analysis and Orai1-STIM2β chimeras indicate it inhibits SOCE through a sequence-specific allosteric interaction with Orai1.\",\n      \"method\": \"Overexpression and mutagenesis, heterodimer formation assay, Orai1-STIM2β chimeric constructs, Ca2+ entry measurements\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mutagenesis plus chimeric protein approach plus functional readout; independent replication of STIM2.1 inhibitory function (consistent with PMID 25896806)\",\n      \"pmids\": [\"26033257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"STIM2 enhances agonist-mediated SOCE by promoting STIM1 clustering at ER-PM junctions at low stimulus intensities. STIM2 lacking five C-terminal amino acids failed to promote STIM1 puncta formation at low agonist concentrations. Coexpression of STIM2 with STIM1ΔK (lacking polybasic region) resulted in co-clustering, suggesting STIM2 recruits STIM1 to ER-PM junctions when ER Ca2+ stores are mildly depleted. STIM2 knockout in mouse salivary glands diminished fluid secretion and SOCE in acinar cells stimulated with low muscarinic agonist concentrations.\",\n      \"method\": \"Conditional STIM2 deletion in salivary glands, C-terminal deletion mutants of STIM2, live cell imaging of STIM1 puncta, Ca2+ imaging, NFAT nuclear translocation assay\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO in vivo plus C-terminal mutagenesis plus live imaging; multiple orthogonal methods\",\n      \"pmids\": [\"25587190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"STIM2 regulates PKA-dependent phosphorylation of the AMPA receptor subunit GluA1 and controls GluA1 surface delivery (both exocytosis and endocytosis). cAMP triggers rapid migration of STIM2 to ER-PM contact sites and promotes GluA1 recruitment to these junctions and STIM2 localization in dendritic spines. STIM2 regulates GluA1 phosphorylation by coupling PKA to AMPARs in a SOCE-independent manner.\",\n      \"method\": \"Biochemical assays, live-cell imaging, STIM2 KO neurons, PKA phosphorylation assays, surface GluA1 trafficking assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO neurons plus biochemical interaction studies plus imaging; single lab\",\n      \"pmids\": [\"25609091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Expression of STIM2 protects hippocampal mushroom spines from Aβ42 oligomer-induced toxicity by rescuing CaMKII activity. Aβ42 oligomer application (in vitro and in vivo by hippocampal injection) reduces mushroom spines and synaptic CaMKII activity; STIM2 overexpression rescues both.\",\n      \"method\": \"In vitro hippocampal cultures with Aβ42 oligomers, in vivo Aβ42 injection into hippocampus, dendritic spine morphology analysis, CaMKII activity measurement, STIM2 overexpression\",\n      \"journal\": \"Molecular neurodegeneration\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — both in vitro and in vivo models with functional rescue; single lab\",\n      \"pmids\": [\"26275606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"STIM2 is required for stable expression of both LTP and LTD at CA3-CA1 hippocampal synapses. Stim2 cKO mice showed altered dendritic spine density/shape in CA1, reduced surface delivery of GluA1 in response to LTP-inducing stimuli, and impaired GluA1 endocytosis following chemically-induced LTD.\",\n      \"method\": \"Stim2 conditional KO mice, electrophysiology (LTP and LTD induction), dendritic spine imaging, GluA1 surface trafficking assays\",\n      \"journal\": \"Neurobiology of learning and memory\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with electrophysiology plus spine morphology plus receptor trafficking; single lab\",\n      \"pmids\": [\"27544849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"STIM2 forms an ER Ca2+-dependent complex with microtubule plus-end binding protein EB3 via a Ser-x-Ile-Pro amino acid motif. Disruption of STIM2-EB3 interaction results in loss of mushroom spines in hippocampal neurons. EB3 overexpression rescues mushroom spine deficiency in PS1-M146V-KI AD neurons and rescues spine loss caused by STIM2 depletion, whereas STIM2 overexpression cannot rescue spines after EB3 knockdown.\",\n      \"method\": \"Co-immunoprecipitation, STIM2-EB3 interaction domain mapping, EB3 and STIM2 overexpression/knockdown, dendritic spine morphology in hippocampal neurons\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with interaction domain mapping plus epistasis (EB3 downstream of STIM2 for spine maintenance); single lab\",\n      \"pmids\": [\"29247211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"STIM2 is constitutively localized within ER-PM junctions in Ca2+-replete cells and induces the activated conformation of STIM1 by trapping STIM1 and triggering remodeling of STIM1 C-terminus, causing STIM1/Orai1 coupling in cells with relatively high ER-[Ca2+]. This enhancement of Orai1 function controls NFAT activation at low agonist concentrations.\",\n      \"method\": \"Conformational FRET sensors for STIM1 and STIM2, protein interaction studies, functional Ca2+ entry and NFAT activation assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET-based conformational sensors plus protein interaction and functional studies; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"29642009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"STIM2 interacts directly with AMPK and CaMKK2. Increased intracellular calcium promotes colocalization and interaction of AMPK with STIM2. STIM2 deficiency attenuates calcium-induced but not energy stress-induced AMPK activation, acting as a scaffold for CaMKK2-AMPK signaling.\",\n      \"method\": \"Co-immunoprecipitation, co-localization microscopy, STIM2 knockout cells, AMPK phosphorylation assays with calcium vs. energy stress stimuli\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus KO with specific stimuli to distinguish calcium vs. energy stress pathways; single lab\",\n      \"pmids\": [\"30335546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cross-talk between N-terminal Ca2+-sensing and C-terminal flexibility of STIM2 determines its distinct activation dynamics. The increased flexibility of the STIM2 C-terminus (compared to STIM1) contributes to its selective store-independent activation by 2-APB. STIM1/STIM2 chimeric constructs and the E470G mutation in STIM1 (equivalent to a STIM2 residue) can switch STIM2 from slow/weak to fast/potent Orai channel activator, and vice versa.\",\n      \"method\": \"CRISPR/Cas9 knockouts, STIM1/STIM2 chimeric constructs, point mutagenesis, FRET-based activity sensors, Ca2+ imaging\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — chimeric protein engineering plus mutagenesis plus FRET sensors plus CRISPR KOs; multiple orthogonal methods in single study\",\n      \"pmids\": [\"30444880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cross-talk between N-terminal and C-terminal domains of STIM2 determines its enhanced sensitivity compared to STIM1. The increased flexibility of the STIM2 C-terminus contributes to store-independent activation by 2-APB, but coordination of N-terminal sensitivity with C-terminal flexibility is required for specific STIM2 store-independent activation. STIM1 variants with enhanced C-terminal flexibility alone were insufficient to support store-independent activation.\",\n      \"method\": \"CRISPR/Cas9 STIM1-/-, STIM2-/-, and STIM1/2-/- knockouts in HEK293 and HCT116 cells, STIM1/STIM2 chimeras, C-terminal stabilizing/disrupting variants, Ca2+ imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — CRISPR KOs plus chimeric constructs plus mutagenesis; multiple cell lines and multiple orthogonal methods\",\n      \"pmids\": [\"30824535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"STIM2 recruits Orai1/STIM1 to the AKAP79 signaling complex at ER-PM junctions, coupling Orai1 Ca2+ entry to NFAT1 activation. STIM2 knockdown had little effect on Orai1/STIM1 clustering or global Ca2+ increases but significantly attenuated NFAT1 activation and AKAP79-Orai1 assembly. The polybasic domain of STIM2 (replacing that of STIM1ΔK) eliminated the requirement of STIM2 for NFAT1 activation.\",\n      \"method\": \"Co-immunoprecipitation, Ca2+ imaging, NFAT1 nuclear translocation assay, siRNA knockdown, domain-swap mutants (STIM1ΔK, polybasic domain chimeras)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple Co-IPs plus domain-swap mutagenesis plus functional readout; multiple orthogonal methods in single study\",\n      \"pmids\": [\"32601188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Oxidative stress modifies STIM2 at cysteine 313, the main redox sensor of STIM2. Oxidative modifications of C313 alter STIM2 activation dynamics and hinder STIM2-mediated gating of ORAI1, suppressing SOCE. Mutation of C313 abolishes the oxidative suppression of SOCE. MD simulations indicate C313 oxidation affects the STIM2 activation conformation.\",\n      \"method\": \"Redox proteomics (in vitro and in vivo), C313 mutagenesis, FLIM/FRET microscopy, patch-clamp, molecular dynamics simulations\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — site-specific mutagenesis plus structural dynamics (FLIM/FRET + MD) plus functional electrophysiology; multiple orthogonal methods\",\n      \"pmids\": [\"33086068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"STIM2 regulates TRPC1 channel activity at partial store depletion conditions. STIM2 overexpression increases both basal TRPC1 activity and number of silent TRPC1 channels at the plasma membrane. After store depletion, STIM2 directly activates TRPC1 even without calcium entry; however, this effect is abrogated by co-expression with non-permeable Orai1 E106Q mutant, indicating Ca2+ entry through Orai triggers TRPC1 activation, while subsequent STIM2-mediated regulation is independent of Ca2+ entry.\",\n      \"method\": \"Single-channel patch-clamp recordings, Orai1 knockout/knockdown, dominant-negative Orai1 E106Q, STIM2 overexpression\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-channel electrophysiology plus dominant-negative and KO experiments; single lab\",\n      \"pmids\": [\"34157631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IP3R function and local ER Ca2+ are the main drivers of immobile STIM2 cluster formation at ER-PM junctions under basal conditions. Endogenous STIM2 is constitutively present in mobile and immobile clusters; immobile clusters associate with ER-PM junctions and recruit Orai1 under basal conditions. ER-PM junction formation (via E-Syt2/3) is required but not sufficient for STIM2 clustering. Ambient PIP2-PLC activity determines IP3R function, STIM2 immobilization, and basal Ca2+ entry.\",\n      \"method\": \"Endogenous STIM2 fluorescent tagging via gene editing, live cell imaging, IP3R functional manipulation, E-Syt2/3 knockout, PLC inhibition, Orai1 recruitment assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous protein tagging plus multiple genetic perturbations plus live imaging; multiple orthogonal methods\",\n      \"pmids\": [\"35022238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In cardiomyocytes (NRVMs), STIM2 splice variants differentially regulate SOCE: STIM2.1 suppresses Orai1-mediated SOCE while STIM2.2 enhances SOCE also involving TRPC1 and TRPC4. STIM2 is present in mitochondria-associated ER membranes (MAMs) and interacts with IP3Rs, VDAC, MCU, and mitofusin-2. STIM2.1 overexpression abolishes mitochondrial Ca2+ uptake, linking STIM2 to mitochondrial Ca2+ homeostasis.\",\n      \"method\": \"siRNA knockdown, overexpression of splice variants, SOCE patch-clamp (ISOC), super-resolution confocal microscopy, Rhod-2 mitochondrial Ca2+ imaging, co-immunoprecipitation of MAM complexes\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods including electrophysiology, super-resolution imaging, and co-IP; single lab\",\n      \"pmids\": [\"38537434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"STIM2 regulates NMDA receptor endocytosis in cortical neurons. Short-term NMDAR overactivation increased STIM2-GluN2A and STIM2-GluN2B interactions. STIM2 silencing inhibited post-activation NMDAR translocation from the plasma membrane and synaptic spines and increased NMDAR currents, suggesting STIM2 promotes NMDAR endocytosis after overactivation to protect against excessive Ca2+ influx.\",\n      \"method\": \"Co-immunoprecipitation, STIM2 siRNA silencing, NMDAR current measurements, NMDAR surface trafficking assays, immunofluorescence in primary cortical neurons\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus functional silencing with electrophysiology and trafficking readouts; single lab\",\n      \"pmids\": [\"37989792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ORAI3 and STIM2 interact under basal conditions in PC-3 prostate cancer cells. STIM2 expression increases during M phase while STIM1 expression and SOCE amplitude decrease. The ORAI3-STIM2 complex allows successful progression through mitosis by preventing mitotic catastrophe; ORAI3 silencing increased SOCE and induced mitotic arrest-related death.\",\n      \"method\": \"Co-immunoprecipitation of ORAI3-STIM2, cell cycle synchronization, SOCE measurements, cell death assays\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus cell cycle-synchronized functional assays; single lab\",\n      \"pmids\": [\"37597301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"STIM2 loss in colorectal cancer cells causes SERCA2-dependent increase in ER Ca2+ content, transcriptional and metabolic rewiring, and activates the ATF4/BiP ER stress response pathway independently of Orai channels. STIM2-deficient CRC xenografts showed increased tumor size, invasion, and metastasis.\",\n      \"method\": \"CRISPR/shRNA STIM2 loss-of-function, xenograft tumor models, SERCA2 rescue experiments, ER Ca2+ measurements, transcriptomic analysis, Orai-independent ER stress pathway assessment\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus in vivo xenograft plus rescue experiments; single lab, multiple methods\",\n      \"pmids\": [\"40554601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In hippocampal neurons, a substantial fraction of STIM2 (but not STIM1) defines ER-PM contacts under resting conditions and is dependent on constitutive NMDAR activity. STIM1 is only transiently recruited to ER-PM junctions during strong NMDAR activation. STIM2 clusters are not enriched at KV2.1-organized junctions, and their activity-dependent confinement is independent of CaV1.2 activity.\",\n      \"method\": \"Single-particle tracking of endogenous STIM1 and STIM2, pharmacological NMDAR and CaV1.2 manipulation, live cell imaging in hippocampal neurons\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-particle tracking of endogenous proteins with pharmacological dissection; single lab\",\n      \"pmids\": [\"40966085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"STIM2, but not STIM1, is required for TRPC2-independent regulation of basal Ca2+ entry in rat thyroid FRTL-5 cells. Knockdown of TRPC2 causes STIM2 to arrange into puncta in resting cells (not seen in controls) and enhances basal Ca2+ entry. PKCδ knockdown mimics TRPC2 loss by increasing STIM2 punctum formation. Basal Ca2+ entry in TRPC2-knockdown cells is dependent on Orai1.\",\n      \"method\": \"shRNA knockdown of TRPC2, siRNA knockdown of PKCδ, immunofluorescence (STIM2 puncta), Ca2+ imaging, Orai1 mutant expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic knockdowns plus localization and functional assays; single lab\",\n      \"pmids\": [\"23144458\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"STIM2 is an ER-resident Ca2+ sensor with a lower activation threshold than STIM1 that constitutively occupies ER-PM junctions where, upon mild ER Ca2+ depletion driven by IP3R activity, it recruits STIM1 and Orai1 to stabilize basal cytosolic and ER Ca2+ concentrations; it also forms heterodimers with STIM1 to modulate Orai1 gating and NFAT activation, activates non-CRAC channels (TRPC1, Imin), is subject to inhibitory redox modification at Cys313 and alternative splicing (STIM2.1/β isoform inhibits via calmodulin binding and impaired Orai1 interaction), interacts with AMPK/CaMKK2 to scaffold calcium-dependent energy sensing, and in neurons additionally regulates dendritic spine stability through the nSOC-CaMKII axis, EB3 association, and AMPAR/NMDAR trafficking.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"STIM2 is an ER-resident Ca2+ sensor that functions as the principal feedback regulator stabilizing basal cytosolic and ER Ca2+ levels by activating Ca2+ influx through Orai1 in response to smaller ER Ca2+ decreases than those required for STIM1 [#0]. Its lower activation threshold derives from biophysical and conformational distinctions: its EF-SAM domain is more structurally stable than that of STIM1 [#2], and a cross-talk between N-terminal Ca2+ sensing and increased C-terminal flexibility tunes its slow/weak versus fast/potent gating of Orai, switchable by STIM1/STIM2 chimeras and point mutations [#24, #25]. Mechanistically, STIM2 is constitutively localized at ER-PM junctions in Ca2+-replete cells, where IP3R activity and local ER Ca2+ drive formation of immobile clusters that recruit Orai1 under basal conditions [#22, #29]. Upon mild store depletion it traps STIM1 and remodels its C-terminus to induce the active conformation, enhancing Orai1 coupling and NFAT activation at low agonist concentrations [#22, #17], and it scaffolds Orai1/STIM1 to the AKAP79 complex to couple Ca2+ entry to NFAT1 [#26]. STIM2 physically interacts with STIM1 and forms heteromers that modulate SOCE [#1, #6, #10]. Beyond CRAC channels, STIM2 differentially regulates non-CRAC store-operated channels including Imin and TRPC1 [#14, #28]. Its activity is negatively controlled by oxidative modification at Cys313 [#27] and by alternative splicing: the STIM2.1/\\u03b2 isoform inhibits SOCE through increased calmodulin affinity, impaired direct Orai1 interaction, and allosteric inhibition via heterodimer recruitment to Orai1 [#15, #16]. STIM2 is required for store-operated Ca2+ entry and NFAT-dependent cytokine production in T cells [#4], and is essential for capacitive Ca2+ entry and ischemia-induced neuronal Ca2+ accumulation, such that its loss is neuroprotective in cerebral ischemia [#5]. In neurons it stabilizes mushroom dendritic spines through a neuronal SOC\\u2013CaMKII axis that is compromised in Alzheimer's disease models [#13, #19], acts through an ER Ca2+-dependent complex with the microtubule plus-end protein EB3 [#21], and controls AMPAR (GluA1) and NMDAR trafficking to regulate synaptic plasticity [#18, #20, #31]. STIM2 additionally scaffolds CaMKK2-AMPK to mediate calcium-dependent energy sensing [#23].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established that STIM2 is functionally and spatially distinct from STIM1, acting as an intracellular inhibitor of STIM1-mediated store-operated Ca2+ entry that physically partners with STIM1.\",\n      \"evidence\": \"Overexpression, immunofluorescence localization, reciprocal co-IP and Ca2+ entry assays across multiple cell lines\",\n      \"pmids\": [\"16860747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the threshold difference quantitatively\", \"Step of inhibition downstream of puncta formation left mechanistically undefined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined STIM2's core physiological role as a feedback sensor that stabilizes basal Ca2+ by responding to smaller ER depletions than STIM1, answering why two STIM paralogs exist.\",\n      \"evidence\": \"Genome-wide siRNA screen of signaling proteome plus Ca2+ imaging and rescue assays\",\n      \"pmids\": [\"18160041\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of the lower threshold not established\", \"Did not address tissue-specific roles\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Provided a biophysical basis for STIM2's distinct activation by showing its EF-SAM domain, despite similar Ca2+ affinity, is more stable and aggregation-resistant than STIM1.\",\n      \"evidence\": \"CD spectroscopy and aggregation assays on recombinant EF-SAM domains in vitro\",\n      \"pmids\": [\"18166150\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro domain behavior not directly linked to full-length cellular gating\", \"Did not test C-terminal contributions\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated STIM2 activates CRAC channels through both store-operated and store-independent modes under calmodulin control, expanding its regulatory repertoire.\",\n      \"evidence\": \"Whole-cell patch-clamp with calmodulin inhibitors, 2-APB, and G418 pharmacology\",\n      \"pmids\": [\"17905723\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CaM binding site not mapped\", \"Physiological trigger of store-independent mode unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Established in vivo that STIM2 is required, alongside STIM1, for NFAT-dependent cytokine production and immune homeostasis in T cells.\",\n      \"evidence\": \"Conditional knockout mice with Ca2+ imaging, NFAT translocation, flow cytometry and cytokine readouts\",\n      \"pmids\": [\"18327260\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution at physiological agonist levels not dissected\", \"Mechanism of NFAT coupling not yet resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed STIM2-specific control of neuronal capacitive Ca2+ entry has pathological consequences, with STIM2 loss conferring neuroprotection in ischemia.\",\n      \"evidence\": \"Stim2 knockout mice, neuronal Ca2+ imaging, hippocampal slices and in vivo focal cerebral ischemia\",\n      \"pmids\": [\"19843959\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors of ischemic Ca2+ accumulation not identified\", \"Channel composition mediating neuronal CCE not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Confirmed dynamic STIM1-STIM2 physical interaction during SOCE activation and their joint requirement in muscle Ca2+ handling and differentiation.\",\n      \"evidence\": \"FRET live imaging, endogenous reciprocal co-IP, siRNA and myoblast differentiation assays in human myotubes\",\n      \"pmids\": [\"20436167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of heteromers not determined\", \"Functional consequence of heteromerization on gating not quantified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended STIM2 localization and interaction networks to acidic Ca2+ stores and platelet contexts, linking it to Orai1, TRPC and SERCA3.\",\n      \"evidence\": \"Organelle fractionation, co-IP and Ca2+ imaging with bafilomycin A1 in human platelets\",\n      \"pmids\": [\"21321120\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect associations not distinguished\", \"Single-lab subcellular fractionation\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed STIM2/Orai1 complexes preferentially govern resting ER Ca2+ and leak in neurons, pharmacologically separable from STIM1/Orai1 SOCE.\",\n      \"evidence\": \"Subcellular fractionation, YFP-STIM overexpression, Fura-2 imaging and SOCE inhibitors in rat cortical neurons\",\n      \"pmids\": [\"21541286\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Overexpression-based, endogenous behavior less defined\", \"Basis of differential inhibitor sensitivity unexplained\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealed a non-canonical cytosolic preSTIM2 from inefficient signal peptide cleavage that regulates basal Ca2+ and transcription store-independently.\",\n      \"evidence\": \"Signal peptide mutagenesis, fractionation, co-IP with ORAI1 and transcription reporter assays\",\n      \"pmids\": [\"21383014\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological abundance of preSTIM2 unclear\", \"Mechanism of plasma-membrane targeting not fully defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Linked STIM1/STIM2 ratio to physiological cell migration, showing STIM2 heteromers suppress STIM1 translocation and TRPC1-mediated influx.\",\n      \"evidence\": \"ODC manipulation of polyamines, STIM1/STIM2 co-IP, Ca2+ imaging and wound-healing migration assays\",\n      \"pmids\": [\"22592407\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct transcriptional vs post-translational control by polyamines not separated\", \"Single-system epithelial context\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated STIM2-specific control of basal Orai1-dependent Ca2+ entry gated by TRPC2 and PKCδ in thyroid cells.\",\n      \"evidence\": \"TRPC2 shRNA, PKCδ siRNA, STIM2 puncta imaging, Ca2+ imaging and Orai1 mutant expression in FRTL-5 cells\",\n      \"pmids\": [\"23144458\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which TRPC2/PKCδ restrains STIM2 clustering unknown\", \"Single cell type\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established that STIM2 preferentially mediates SOCE and Ca2+ oscillations under mild, physiological store depletion without engaging STIM1-dependent responses.\",\n      \"evidence\": \"siRNA, G418 inhibition and Ca2+ oscillation measurements across mast cells, T cells and HEK293; endogenous PLA/co-IP of STIM2-ORAI1 in neurons\",\n      \"pmids\": [\"23359669\", \"23711249\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative depletion threshold not defined\", \"Single-lab studies\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Distinguished STIM2 from STIM1 in regulating non-CRAC Imin and TRPC channels, showing the active STIM2/STIM1 ratio switches channel modes.\",\n      \"evidence\": \"Single-channel patch-clamp with selective STIM1/STIM2 activation in native HEK293 cells\",\n      \"pmids\": [\"25533457\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular determinants of channel selectivity not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined a neuronal STIM2-nSOC-CaMKII axis essential for mushroom spine stability and showed its disruption underlies spine loss in Alzheimer's models.\",\n      \"evidence\": \"PS1-M146V knockin mice, spine morphology, Ca2+ imaging, CaMKII assays and STIM2 overexpression rescue\",\n      \"pmids\": [\"24698269\", \"26275606\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Channel composition of synaptic nSOC not fully defined\", \"Link between STIM2 downregulation and amyloid pathology causality incomplete\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified STIM2.1/STIM2β splice isoform as a dominant inhibitor of SOCE acting via calmodulin and impaired/allosteric Orai1 interaction recruited through heterodimers.\",\n      \"evidence\": \"Reciprocal siRNA knockdown in T cells, Orai1 co-IP, calmodulin binding, mutagenesis and Orai1-STIM2β chimeras\",\n      \"pmids\": [\"25896806\", \"26033257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Regulation of splice-isoform ratio in vivo not established\", \"Structural basis of allosteric inhibition not resolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed STIM2 promotes STIM1 clustering at ER-PM junctions at low stimulus intensity in vivo, with C-terminal residues required for recruitment and secretory function.\",\n      \"evidence\": \"Conditional STIM2 deletion in salivary glands, C-terminal deletion mutants, live STIM1 puncta imaging and NFAT assays\",\n      \"pmids\": [\"25587190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact recruitment interface not defined\", \"How threshold integrates with STIM1 polybasic domain unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Uncovered a SOCE-independent neuronal function: STIM2 couples PKA to AMPAR GluA1, controlling its phosphorylation and surface trafficking.\",\n      \"evidence\": \"STIM2 KO neurons, biochemical PKA phosphorylation assays, live imaging and GluA1 surface trafficking assays\",\n      \"pmids\": [\"25609091\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct STIM2-PKA-GluA1 binding architecture not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established STIM2 as required for stable LTP and LTD via control of GluA1 trafficking, connecting its synaptic role to plasticity.\",\n      \"evidence\": \"Stim2 conditional KO mice, LTP/LTD electrophysiology, spine imaging and GluA1 trafficking assays\",\n      \"pmids\": [\"27544849\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether plasticity defect is SOCE-dependent not separated\", \"Behavioral consequences not assessed here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified an ER Ca2+-dependent STIM2-EB3 complex acting downstream of STIM2 to maintain mushroom spines, placing microtubule dynamics in the pathway.\",\n      \"evidence\": \"Co-IP, interaction-motif mapping, epistasis via EB3/STIM2 overexpression and knockdown in hippocampal neurons\",\n      \"pmids\": [\"29247211\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How EB3 enacts spine maintenance downstream not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Resolved the mechanism of STIM2's threshold advantage: it is constitutive at ER-PM junctions and traps/remodels STIM1 to drive Orai1 coupling and NFAT at high ER-Ca2+.\",\n      \"evidence\": \"Conformational FRET sensors for STIM1/STIM2, interaction and functional Ca2+/NFAT assays\",\n      \"pmids\": [\"29642009\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trapping interface not structurally defined\", \"Quantitative occupancy at junctions not measured\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined the structural determinant of STIM2's distinct dynamics as cross-talk between N-terminal sensing and C-terminal flexibility, switchable by chimeras and single residues.\",\n      \"evidence\": \"CRISPR KOs, STIM1/STIM2 chimeras, E470G mutation, FRET sensors and Ca2+ imaging across HEK293/HCT116\",\n      \"pmids\": [\"30444880\", \"30824535\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure of the activating conformation not solved\", \"How redox and splicing intersect with C-terminal flexibility not unified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed a SOCE-independent metabolic role: STIM2 scaffolds CaMKK2-AMPK to selectively mediate calcium-induced AMPK activation.\",\n      \"evidence\": \"Co-IP, colocalization, STIM2 KO cells and AMPK phosphorylation under calcium vs energy stress\",\n      \"pmids\": [\"30335546\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding regions not mapped\", \"Physiological metabolic outputs not characterized\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed STIM2 selectively couples Orai1 Ca2+ entry to NFAT1 by recruiting the channel to the AKAP79 complex through its polybasic domain, independent of bulk clustering.\",\n      \"evidence\": \"Co-IP, Ca2+ imaging, NFAT1 translocation, siRNA and polybasic domain-swap mutants\",\n      \"pmids\": [\"32601188\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How AKAP79 selectivity is achieved over STIM1 not fully defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified Cys313 as STIM2's main redox sensor, providing a mechanism by which oxidative stress suppresses STIM2-mediated Orai1 gating.\",\n      \"evidence\": \"Redox proteomics, C313 mutagenesis, FLIM/FRET, patch-clamp and MD simulations\",\n      \"pmids\": [\"33086068\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological redox triggers not defined\", \"Interplay with splice isoform inhibition unexplored\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Clarified STIM2's regulation of TRPC1, showing Orai-mediated Ca2+ entry initiates TRPC1 activation while subsequent STIM2 regulation is Ca2+-entry-independent.\",\n      \"evidence\": \"Single-channel patch-clamp, Orai1 KO/knockdown and dominant-negative Orai1 E106Q with STIM2 overexpression\",\n      \"pmids\": [\"34157631\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct STIM2-TRPC1 interface not mapped\", \"Overexpression-based, single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established the upstream logic of basal STIM2 clustering: IP3R-driven local ER Ca2+, set by PIP2-PLC activity, immobilizes endogenous STIM2 at ER-PM junctions to recruit Orai1.\",\n      \"evidence\": \"Endogenous STIM2 gene-edited tagging, live imaging, IP3R manipulation, E-Syt2/3 KO, PLC inhibition and Orai1 recruitment assays\",\n      \"pmids\": [\"35022238\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between local Ca2+ and immobilization not defined\", \"Generalizability beyond the studied cell type\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended STIM2 partnerships to ORAI3 in mitosis, where the basal ORAI3-STIM2 complex restrains SOCE to permit mitotic progression in prostate cancer cells.\",\n      \"evidence\": \"Co-IP, cell-cycle synchronization, SOCE measurements and cell death assays in PC-3 cells\",\n      \"pmids\": [\"37597301\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of cell-cycle-dependent STIM2/STIM1 switch unclear\", \"Single cell line\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed STIM2 promotes NMDAR endocytosis after overactivation, providing a neuroprotective brake on excessive Ca2+ influx.\",\n      \"evidence\": \"Co-IP of STIM2-GluN2A/GluN2B, STIM2 silencing, NMDAR currents and surface trafficking in cortical neurons\",\n      \"pmids\": [\"37989792\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs adaptor-mediated NMDAR interaction not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected STIM2 splice variants to mitochondrial Ca2+ homeostasis via MAM-localized complexes, with STIM2.1 abolishing mitochondrial Ca2+ uptake.\",\n      \"evidence\": \"siRNA, splice-variant overexpression, ISOC patch-clamp, super-resolution imaging, Rhod-2 imaging and MAM co-IPs in cardiomyocytes\",\n      \"pmids\": [\"38537434\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct interaction partners within MAM not validated reciprocally\", \"Single lab, cardiomyocyte-specific\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed an Orai-independent tumor-suppressive function: STIM2 loss raises ER Ca2+ via SERCA2, rewires metabolism and triggers the ATF4/BiP ER stress pathway, promoting CRC progression.\",\n      \"evidence\": \"CRISPR/shRNA loss-of-function, xenografts, SERCA2 rescue, ER Ca2+ and transcriptomic analyses\",\n      \"pmids\": [\"40554601\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which STIM2 restrains SERCA2 not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed that resting ER-PM contact definition by STIM2 in neurons depends on constitutive NMDAR activity, distinguishing STIM2 from transiently recruited STIM1.\",\n      \"evidence\": \"Single-particle tracking of endogenous STIM1/STIM2 with NMDAR and CaV1.2 pharmacology in hippocampal neurons\",\n      \"pmids\": [\"40966085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular coupling between NMDAR activity and STIM2 confinement unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How STIM2's various regulatory inputs — redox modification, alternative splicing, calmodulin, C-terminal flexibility, and junctional scaffolding partners — are integrated structurally to set its activation threshold and channel selectivity remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure of the active STIM2 conformation or STIM2-Orai1 interface\", \"Quantitative integration of splice/redox/CaM inputs not modeled\", \"In vivo physiological triggers distinguishing STIM2 from STIM1 incompletely defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [0, 2, 11, 22, 29]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 22, 24]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 15, 16, 27, 28]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [22, 23, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 1, 22, 29]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [9, 17, 22, 29, 34]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [30]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 22, 26]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 4, 17]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [13, 18, 20, 31]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [27, 33]}\n    ],\n    \"complexes\": [\"STIM1-STIM2 heteromer\", \"STIM2-Orai1 complex\", \"AKAP79-Orai1-STIM signaling complex\", \"MAM Ca2+ complex (IP3R/VDAC/MCU/mitofusin-2)\"],\n    \"partners\": [\"STIM1\", \"ORAI1\", \"EB3\", \"AMPK\", \"CaMKK2\", \"AKAP79\", \"TRPC1\", \"ORAI3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":10,"faith_total":10,"faith_pct":100.0}}