{"gene":"CALU","run_date":"2026-06-14T21:01:36+00:00","timeline":{"discoveries":[{"year":1997,"finding":"Calumenin is a Ca2+-binding protein with six EF-hand motifs retained in the endoplasmic reticulum; the C-terminal tetrapeptide HDEF is responsible for ER retention, with the Phe residue being a novel component of the ER retention signal.","method":"Retention assay, immunostaining with confocal laser microscope, deglycosylation assay, Ca2+-binding assay with purified protein","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (retention assay, immunostaining, deglycosylation, direct Ca2+-binding with purified protein) in a single rigorous study","pmids":["9218460"],"is_preprint":false},{"year":1998,"finding":"Recombinant human calumenin binds Ca2+ through all 7 EF-hand domains with low affinity (Kd ~1/1.6×10³ M⁻¹ per site), consistent with a role in Ca2+-dependent ER processes.","method":"Microdialysis Ca2+-binding experiments with recombinant human calumenin expressed in E. coli","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro binding assay with purified recombinant protein, single lab but well-characterized method","pmids":["9675259"],"is_preprint":false},{"year":1999,"finding":"Human calumenin localizes to both the ER and Golgi complex in multiple human cell lines, and a glycosylated, endoglycosidase H-resistant form is secreted into the culture medium, indicating transit through the Golgi and extracellular release.","method":"Immunofluorescence, immunoelectron microscopy, endoglycosidase H treatment, Western blot of conditioned medium","journal":"Experimental cell research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal localization and biochemical methods in several cell lines, single lab","pmids":["10222138"],"is_preprint":false},{"year":2000,"finding":"Calumenin binds serum amyloid P component (SAP) in a Ca2+-dependent manner; this interaction was identified by affinity chromatography and verified by surface plasmon resonance.","method":"Affinity chromatography with immobilized recombinant calumenin, amino acid sequencing of eluate, surface plasmon resonance","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal pull-down plus SPR confirmation, but single lab and functional consequence not fully established","pmids":["10631319"],"is_preprint":false},{"year":2006,"finding":"Calumenin-2 interacts with ryanodine receptor 1 (RyR1) in rabbit skeletal sarcoplasmic reticulum in a Ca2+-dependent manner; the second EF-hand domain of calumenin is essential for this interaction. Overexpression of calumenin-2 in C2C12 myotubes increases caffeine-induced Ca2+ release but decreases depolarization-induced Ca2+ release.","method":"GST pull-down, co-immunoprecipitation, EF-hand deletion constructs, adenovirus-mediated overexpression, Ca2+ imaging","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal methods (GST pull-down, co-IP, deletion mutagenesis, functional Ca2+ imaging), single lab","pmids":["16527250"],"is_preprint":false},{"year":2008,"finding":"Calumenin overexpression in neonatal rat cardiomyocytes prolongs time to 50% Ca2+ baseline (T50) by inhibiting SERCA2-mediated Ca2+ uptake into the SR; co-immunoprecipitation demonstrates a direct interaction between calumenin and SERCA2.","method":"Adenovirus-mediated overexpression, Ca2+ transient measurement, oxalate-supported Ca2+ uptake assay, co-immunoprecipitation","journal":"Molecules and cells","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP, functional Ca2+ assay, Ca2+ uptake assay), single lab","pmids":["18562801"],"is_preprint":false},{"year":2009,"finding":"Calumenin (calu-1) in C. elegans is required for fertility, locomotion, body size, defecation, and pharyngeal pumping; genetic analysis suggests calu-1 regulates pharyngeal pumping together with the IP3 receptor (itr-1).","method":"Mutant analysis, genetic epistasis (calu-1 and itr-1 double mutant analysis), behavioral assays","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in vivo with multiple phenotypic readouts, single lab","pmids":["19695248"],"is_preprint":false},{"year":2009,"finding":"Calumenin interacts with SERCA2 in mouse cardiac SR; the binding is favored in the E1 state of SERCA2 (reduced by thapsigargin, vanadate, or ATP). GST pull-down with deletion fragments maps the interaction to residues 132–222 of calumenin and residues 853–892 (L4 luminal domain) of SERCA2. Calumenin knockdown (80%) in HL-1 cells enhances Ca2+ transient amplitude and increases Ca2+ sensitivity of SERCA2.","method":"GST pull-down with deletion fragments, co-immunoprecipitation, immunocytochemistry, siRNA knockdown, oxalate-supported Ca2+ uptake assay, state-specific SERCA2 inhibitors","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — domain mapping by GST pull-down, co-IP, functional Ca2+ uptake with KD, and state-dependent interaction, multiple orthogonal methods","pmids":["19740751"],"is_preprint":false},{"year":2012,"finding":"Calumenin-1/2 secretion requires microtubule integrity and is mediated by motor proteins Kif5b and cytoplasmic dynein; the export signal maps to amino acids 20–46, and asparagine at position 131 is required for protein stabilization.","method":"Time-lapse live-cell imaging of calu-1/2-EGFP, microtubule disruption, dominant-negative motor protein expression, deletion mapping","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging plus motor protein and domain mutant experiments, single lab","pmids":["22514732"],"is_preprint":false},{"year":2012,"finding":"Calumenin is identified as a binding partner of G551D-CFTR by co-immunoprecipitation and mass spectrometry, and is more abundant in the G551D-CFTR complex than in the wild-type CFTR complex; the interaction was confirmed by surface plasmon resonance.","method":"Co-immunoprecipitation, 2D-gel electrophoresis, mass spectrometry, surface plasmon resonance, immunofluorescence","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP/MS plus SPR confirmation, single lab, functional role in CFTR maturation inferred but not fully demonstrated","pmids":["22768251"],"is_preprint":false},{"year":2013,"finding":"Calumenin overexpression in neonatal rat ventricular cardiomyocytes reduces ER stress markers (GRP78, p-PERK, p-eIF2α) and ER-initiated apoptosis markers (CHOP, p-JNK) during tunicamycin-induced ER stress, and reduces apoptosis as measured by TUNEL assay.","method":"Recombinant adenovirus-mediated overexpression (7.5-fold), Western blot for ER stress markers, TUNEL assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional overexpression with multiple marker readouts, single lab","pmids":["24012670"],"is_preprint":false},{"year":2013,"finding":"Calumenin isoform Calu-15 promotes filopodia formation and cell migration by: (1) shuttling between nucleus and cytoplasm via interaction with importin α, Ran GTPase, and CRM1; (2) requiring CK2-dependent phosphorylation of Thr-73 for nuclear import; and (3) binding the GDF-15 promoter in the nucleus to increase GDF-15 transcription.","method":"Alternative splicing cloning, co-immunoprecipitation (importin α, Ran, CRM1), CK2 inhibition, Thr-73 point mutation, chromatin immunoprecipitation, promoter-reporter assay, filopodia imaging","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP, mutagenesis, ChIP, reporter assay), single lab, specific to Calu-15 isoform","pmids":["24136234"],"is_preprint":false},{"year":2014,"finding":"Extracellular calumenin binds and stabilizes fibulin-1, protecting it from MMP-13-mediated proteolysis; this suppresses ERK1/2 signaling and inhibits cell migration. The minimal functional domain maps to residues 74–138 and 214–280. Calumenin/fibulin-1 also interact with fibronectin and signal through syndecan-4 and α5β1-integrin to suppress pERK1/2.","method":"Co-immunoprecipitation, siRNA knockdown, in vitro MMP-13 cleavage protection assay, ERK1/2 phosphorylation Western blot, migration assay, domain deletion mapping","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, in vitro MMP protection, signaling readouts, receptor blocking), replicated across multiple cell types in single study","pmids":["24632605"],"is_preprint":false},{"year":2014,"finding":"Calumenin reduces F508del-CFTR aggregation in vitro, similar to an intrinsically disordered protein (IDP), and shows altered trafficking in bronchial cells expressing F508del-CFTR, indicating a direct role in mutant CFTR folding/processing.","method":"Aggregation assay (recombinant calumenin + F508del-CFTR), fluorescence microscopy-based trafficking analysis, biophysical characterization","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — in vitro aggregation assay plus imaging, single lab, functional mechanism not fully resolved","pmids":["25120007"],"is_preprint":false},{"year":2015,"finding":"CALU polymorphism rs1043550 (A29809G) reduces calumenin mRNA stability by ~30% as shown by a luciferase reporter assay in vascular cells; reduced calumenin availability correlates with impaired gamma-carboxylation of matrix-Gla-protein and altered vascular calcification.","method":"Luciferase reporter system (mRNA stability assay), immunohistochemistry, clinical genotyping, extracellular matrix mineralization assay in hVSMC","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay for mRNA stability plus cell culture model, single lab","pmids":["25823396"],"is_preprint":false},{"year":2015,"finding":"Calumenin and reticulocalbin interact with fibulin-1C, C1 esterase inhibitor, and GRP75 (Grp75); calumenin binds fibulin-1C with Kd ~50–60 nM and C1 esterase inhibitor with Kd ~150 nM; the calumenin–C1 esterase inhibitor interaction is Ca2+-dependent (detectable at 3.5 mM, absent at 0.1 mM Ca2+).","method":"Affinity purification, co-immunoprecipitation, mass spectrometry, surface plasmon resonance","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP/MS plus SPR quantification, single lab","pmids":["26161649"],"is_preprint":false},{"year":2016,"finding":"Calumenin undergoes Ca2+-induced folding: in low Ca2+, the protein is largely disordered; upon Ca2+ addition it adopts a compact, predominantly alpha-helical trilobal structure. This conformational switch is reversible.","method":"Circular dichroism spectroscopy, small-angle X-ray scattering (SAXS), analytical size-exclusion chromatography, surface plasmon resonance","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple biophysical methods (CD, SAXS, SEC, SPR) in a single rigorous study demonstrating Ca2+-dependent folding","pmids":["26991433"],"is_preprint":false},{"year":2017,"finding":"Calumenin modulates SERCA pump activity and is a key regulator of ER Ca2+ homeostasis in bronchial epithelial cells expressing both wild-type and F508del-CFTR; reducing calumenin expression partially restores F508del-CFTR activity.","method":"siRNA knockdown, ER Ca2+ measurement, SERCA activity assay, CFTR functional assay","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional knockdown with Ca2+ and CFTR activity readouts, single lab","pmids":["28189267"],"is_preprint":false},{"year":2026,"finding":"Calumenin acts as a chaperone for vimentin proteostasis in lung fibroblasts: it collaborates with the TRiC chaperonin complex to facilitate proper vimentin folding, and recruits the CCT2 subunit to degrade misfolded vimentin aggregates. Fibroblast-specific knockout of calumenin promotes vimentin aggregate accumulation and profibrotic factor (migracytosis) secretion, exacerbating fibroblast senescence and lung aging. External profibrotic stimuli trigger calcium transients that induce calumenin degradation.","method":"CRISPR-based genetic screen, fibroblast-specific knockout mouse, co-immunoprecipitation (TRiC/CCT2), live-cell imaging, Ca2+ imaging, Western blot, electron microscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR screen plus fibroblast-specific KO with multiple orthogonal methods (co-IP, imaging, Ca2+ measurement), multiple phenotypic readouts","pmids":["41557802"],"is_preprint":false}],"current_model":"Calumenin is a Ca2+-dependent folding sensor and multi-functional chaperone of the secretory pathway (ER/SR lumen) that, upon Ca2+ binding, transitions from a disordered to a compact trilobal structure, enabling it to regulate SERCA2 (inhibiting SR Ca2+ uptake), RyR1/RyR2 (modulating Ca2+ release), CFTR maturation, vimentin proteostasis (via TRiC/CCT2 recruitment), and extracellular functions including fibulin-1 stabilization (protecting it from MMP-13 cleavage) to suppress ERK1/2-dependent cell migration; additionally, the Calu-15 splice isoform undergoes CK2-dependent phosphorylation at Thr-73 for nuclear import and transcriptionally upregulates GDF-15 to promote filopodia formation."},"narrative":{"mechanistic_narrative":"Calumenin (CALU) is a Ca2+-binding protein of the secretory pathway that functions as a Ca2+-dependent folding sensor and multi-functional chaperone regulating Ca2+ handling, protein proteostasis, and extracellular signaling [PMID:9218460, PMID:26991433]. It is retained in the ER via a C-terminal HDEF tetrapeptide and binds Ca2+ through multiple low-affinity EF-hand motifs, and upon Ca2+ binding it switches reversibly from a largely disordered state to a compact, alpha-helical trilobal fold that underlies its activity [PMID:9218460, PMID:9675259, PMID:26991433]. A fraction transits the Golgi and is secreted, with export depending on microtubule integrity and the motors Kif5b and cytoplasmic dynein [PMID:10222138, PMID:22514732]. In the SR/ER lumen, calumenin directly binds SERCA2 in its E1 state to inhibit Ca2+ uptake and binds RyR1 in a Ca2+-dependent manner to modulate Ca2+ release, thereby tuning intracellular Ca2+ homeostasis [PMID:18562801, PMID:19740751, PMID:16527250]. Through this Ca2+/SERCA control it also governs ER Ca2+ levels in bronchial epithelium, where its reduction partially restores F508del-CFTR activity, and it physically associates with mutant CFTR to influence its folding and trafficking [PMID:22768251, PMID:25120007, PMID:28189267]. Calumenin further acts as a chaperone for vimentin proteostasis by collaborating with the TRiC chaperonin and recruiting CCT2 to clear misfolded vimentin aggregates, with loss promoting fibroblast senescence and lung aging [PMID:41557802]. Extracellularly, calumenin binds and stabilizes fibulin-1, protecting it from MMP-13 cleavage and suppressing ERK1/2-dependent cell migration via syndecan-4 and α5β1-integrin signaling [PMID:24632605]. A distinct Calu-15 splice isoform undergoes CK2-dependent Thr-73 phosphorylation enabling nuclear import and transcriptional upregulation of GDF-15 to promote filopodia formation [PMID:24136234].","teleology":[{"year":1997,"claim":"Established calumenin as an ER-resident Ca2+-binding protein and defined a novel ER retention signal, framing it as a luminal Ca2+-handling factor.","evidence":"Retention assay, immunostaining, deglycosylation, and direct Ca2+-binding with purified protein","pmids":["9218460"],"confidence":"High","gaps":["Functional role beyond Ca2+ binding not addressed","Affinity and stoichiometry of Ca2+ sites not quantified here"]},{"year":1998,"claim":"Quantified calumenin's Ca2+ binding as multi-site low-affinity, consistent with a buffering/sensing role rather than high-affinity signaling.","evidence":"Microdialysis Ca2+-binding with recombinant human protein","pmids":["9675259"],"confidence":"High","gaps":["Conformational consequences of binding not resolved","In vivo relevance of low affinity untested"]},{"year":1999,"claim":"Showed calumenin is not strictly ER-confined but transits the Golgi and is secreted, opening an extracellular dimension to its function.","evidence":"Immunofluorescence, immunoEM, endoglycosidase H, Western blot of conditioned medium","pmids":["10222138"],"confidence":"High","gaps":["Extracellular function unknown at this stage","Mechanism of escape from HDEF retention unclear"]},{"year":2000,"claim":"Identified the first Ca2+-dependent binding partner (SAP), establishing calumenin as a Ca2+-regulated interaction protein.","evidence":"Affinity chromatography, sequencing, and surface plasmon resonance","pmids":["10631319"],"confidence":"Medium","gaps":["Functional consequence of SAP binding not established","Single lab, no in vivo validation"]},{"year":2006,"claim":"Linked calumenin to excitation-contraction coupling by mapping a Ca2+-dependent RyR1 interaction and demonstrating functional modulation of Ca2+ release.","evidence":"GST pull-down, co-IP, EF-hand deletion, overexpression, Ca2+ imaging in C2C12 myotubes","pmids":["16527250"],"confidence":"High","gaps":["Direct vs indirect RyR1 contact not resolved","Physiological role in intact muscle untested"]},{"year":2008,"claim":"Established a direct calumenin–SERCA2 interaction that inhibits SR Ca2+ uptake, defining a cardiac Ca2+-handling function.","evidence":"Adenoviral overexpression, Ca2+ transients, oxalate-supported uptake, co-IP in cardiomyocytes","pmids":["18562801"],"confidence":"High","gaps":["Interaction interface not mapped here","Endogenous loss-of-function not tested"]},{"year":2009,"claim":"Mapped the calumenin–SERCA2 interface and showed state-specific (E1) binding plus knockdown enhancement of Ca2+ transients, establishing mechanism and direction of regulation.","evidence":"GST pull-down with deletion fragments, co-IP, siRNA knockdown, state-specific inhibitors, Ca2+ uptake in HL-1 cells","pmids":["19740751"],"confidence":"High","gaps":["Structural basis of E1 preference not resolved","Regulation by Ca2+ occupancy of EF-hands unclear"]},{"year":2009,"claim":"Demonstrated organismal requirement for calumenin in C. elegans and genetic interaction with the IP3 receptor, connecting it to whole-animal Ca2+ physiology.","evidence":"Mutant analysis and genetic epistasis with itr-1, behavioral assays","pmids":["19695248"],"confidence":"Medium","gaps":["Molecular mechanism of IP3R interplay unknown","Mammalian relevance not tested"]},{"year":2012,"claim":"Defined the cellular machinery and signals for calumenin secretion, showing microtubule- and motor-dependent export.","evidence":"Live-cell imaging, microtubule disruption, dominant-negative motors, deletion mapping","pmids":["22514732"],"confidence":"Medium","gaps":["How export bypasses ER retention not explained","Single lab"]},{"year":2012,"claim":"Connected calumenin to disease-relevant CFTR processing by identifying it as a partner enriched in the G551D-CFTR complex.","evidence":"Co-IP, 2D-gel, mass spectrometry, SPR, immunofluorescence","pmids":["22768251"],"confidence":"Medium","gaps":["Functional effect on CFTR maturation inferred, not demonstrated","Direct vs complex-mediated binding unclear"]},{"year":2013,"claim":"Revealed a cytoprotective role: calumenin overexpression suppresses ER stress and apoptosis pathways in cardiomyocytes.","evidence":"Adenoviral overexpression, ER-stress and apoptosis marker Westerns, TUNEL","pmids":["24012670"],"confidence":"Medium","gaps":["Loss-of-function ER-stress phenotype untested","Mechanism linking Ca2+ regulation to ER stress not dissected"]},{"year":2013,"claim":"Uncovered a non-canonical nuclear/transcriptional pathway through the Calu-15 isoform driving filopodia formation via GDF-15 upregulation.","evidence":"Splice cloning, co-IP (importin α/Ran/CRM1), CK2 inhibition, Thr-73 mutation, ChIP, reporter assays, filopodia imaging","pmids":["24136234"],"confidence":"Medium","gaps":["Isoform-specific physiological role in vivo unknown","Generality beyond Calu-15 unclear"]},{"year":2014,"claim":"Defined an extracellular tumor-suppressive function: calumenin stabilizes fibulin-1 against MMP-13 to suppress ERK1/2-dependent migration through receptor signaling.","evidence":"Co-IP, siRNA, in vitro MMP-13 protection, ERK Westerns, migration assays, domain mapping","pmids":["24632605"],"confidence":"High","gaps":["In vivo relevance to tumor progression not established here","Stoichiometry of fibulin-1/fibronectin complex unresolved"]},{"year":2014,"claim":"Showed calumenin behaves like an intrinsically disordered chaperone reducing F508del-CFTR aggregation, linking biophysics to mutant CFTR handling.","evidence":"In vitro aggregation assay with recombinant calumenin, trafficking imaging","pmids":["25120007"],"confidence":"Medium","gaps":["Mechanism of trafficking change not resolved","Whether effect is direct chaperoning unclear"]},{"year":2015,"claim":"Provided a clinical/regulatory link by showing a CALU polymorphism reduces mRNA stability and correlates with altered vascular calcification.","evidence":"Luciferase mRNA-stability reporter, IHC, genotyping, mineralization assay in hVSMC","pmids":["25823396"],"confidence":"Medium","gaps":["Causality between calumenin level and calcification not proven","Mechanistic link to gamma-carboxylation correlative"]},{"year":2015,"claim":"Quantified high-affinity extracellular/luminal partner interactions (fibulin-1C, C1 esterase inhibitor, GRP75), refining calumenin's interactome and Ca2+-dependence.","evidence":"Affinity purification, co-IP, mass spectrometry, SPR","pmids":["26161649"],"confidence":"Medium","gaps":["Functional consequence of C1 inhibitor and GRP75 binding unknown","Single lab"]},{"year":2016,"claim":"Provided the structural basis for calumenin function: a reversible Ca2+-induced disorder-to-compact-trilobal-fold transition that gates its activity.","evidence":"CD, SAXS, analytical SEC, SPR","pmids":["26991433"],"confidence":"High","gaps":["High-resolution structure not determined","How fold change maps onto partner binding not directly shown"]},{"year":2017,"claim":"Integrated calumenin's SERCA regulation with CFTR rescue, showing knockdown restores F508del-CFTR activity via ER Ca2+ control.","evidence":"siRNA knockdown, ER Ca2+ and SERCA activity assays, CFTR functional assay in bronchial cells","pmids":["28189267"],"confidence":"Medium","gaps":["Therapeutic translation untested","Direct vs Ca2+-mediated CFTR effect not fully separated"]},{"year":2026,"claim":"Established calumenin as a proteostasis chaperone for vimentin via TRiC/CCT2, with loss driving fibroblast senescence and lung aging, expanding its role beyond Ca2+ handling.","evidence":"CRISPR screen, fibroblast-specific KO mouse, co-IP (TRiC/CCT2), live-cell and Ca2+ imaging, EM","pmids":["41557802"],"confidence":"High","gaps":["How Ca2+-induced calumenin degradation is triggered mechanistically unresolved","Generality of vimentin chaperoning across cell types untested"]},{"year":null,"claim":"How calumenin's Ca2+-gated conformational switch is mechanistically coupled to its diverse outputs (SERCA/RyR regulation, CFTR folding, vimentin chaperoning, fibulin-1 stabilization) remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model linking fold state to partner selection","Tissue-specific division of labor among functions unclear","No high-resolution structure of any calumenin-partner complex"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[13,18]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,7,4]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[11]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[12]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,17]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[2]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,12]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[10,16]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[13,18]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[12]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5,7]}],"complexes":["TRiC/CCT chaperonin (associated)","calumenin/fibulin-1/fibronectin extracellular complex"],"partners":["ATP2A2","RYR1","FBLN1","CFTR","CCT2","SERPING1","HSPA9","APCS"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43852","full_name":"Calumenin","aliases":["Crocalbin","IEF SSP 9302"],"length_aa":315,"mass_kda":37.1,"function":"Involved in regulation of vitamin K-dependent carboxylation of multiple N-terminal glutamate residues. Seems to inhibit gamma-carboxylase GGCX. Binds 7 calcium ions with a low affinity (By similarity)","subcellular_location":"Endoplasmic reticulum membrane; Golgi apparatus; Secreted; Melanosome; Sarcoplasmic reticulum lumen","url":"https://www.uniprot.org/uniprotkb/O43852/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CALU","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SAR1B","stoichiometry":0.2},{"gene":"TMED2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CALU","total_profiled":1310},"omim":[{"mim_id":"603420","title":"CALUMENIN; CALU","url":"https://www.omim.org/entry/603420"},{"mim_id":"602544","title":"PARKIN RBR E3 UBIQUITIN PROTEIN LIGASE; PRKN","url":"https://www.omim.org/entry/602544"},{"mim_id":"190070","title":"KRAS PROTOONCOGENE, GTPase; KRAS","url":"https://www.omim.org/entry/190070"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Endoplasmic reticulum","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CALU"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O43852","domains":[{"cath_id":"-","chopping":"43-207_250-297","consensus_level":"medium","plddt":83.8542,"start":43,"end":297}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43852","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43852-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43852-F1-predicted_aligned_error_v6.png","plddt_mean":79.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CALU","jax_strain_url":"https://www.jax.org/strain/search?query=CALU"},"sequence":{"accession":"O43852","fasta_url":"https://rest.uniprot.org/uniprotkb/O43852.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43852/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43852"}},"corpus_meta":[{"pmid":"9218460","id":"PMC_9218460","title":"Calumenin, a Ca2+-binding protein retained in the endoplasmic reticulum with a novel carboxyl-terminal sequence, HDEF.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9218460","citation_count":95,"is_preprint":false},{"pmid":"10222138","id":"PMC_10222138","title":"Human calumenin localizes to the secretory pathway and is secreted to the medium.","date":"1999","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/10222138","citation_count":84,"is_preprint":false},{"pmid":"24012670","id":"PMC_24012670","title":"Calumenin has a role in the alleviation of ER stress in neonatal rat cardiomyocytes.","date":"2013","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/24012670","citation_count":56,"is_preprint":false},{"pmid":"9675259","id":"PMC_9675259","title":"Molecular cloning of a cDNA encoding human calumenin, expression in Escherichia coli and analysis of its Ca2+-binding activity.","date":"1998","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/9675259","citation_count":56,"is_preprint":false},{"pmid":"25963840","id":"PMC_25963840","title":"Identification and evaluation of metastasis-related proteins, oxysterol binding protein-like 5 and calumenin, in lung tumors.","date":"2015","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/25963840","citation_count":55,"is_preprint":false},{"pmid":"19740751","id":"PMC_19740751","title":"Characterization of calumenin-SERCA2 interaction in mouse cardiac sarcoplasmic reticulum.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19740751","citation_count":52,"is_preprint":false},{"pmid":"34150647","id":"PMC_34150647","title":"The Epithelial to Mesenchymal Transition Related Gene Calumenin Is an Adverse Prognostic Factor of Bladder Cancer Correlated With Tumor Microenvironment Remodeling, Gene Mutation, and Ferroptosis.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34150647","citation_count":48,"is_preprint":false},{"pmid":"16527250","id":"PMC_16527250","title":"Calumenin, a multiple EF-hands Ca2+-binding protein, interacts with ryanodine receptor-1 in rabbit skeletal sarcoplasmic reticulum.","date":"2006","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/16527250","citation_count":44,"is_preprint":false},{"pmid":"10631319","id":"PMC_10631319","title":"Calumenin interacts with serum amyloid P component.","date":"2000","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/10631319","citation_count":39,"is_preprint":false},{"pmid":"24632605","id":"PMC_24632605","title":"Extracellular calumenin suppresses ERK1/2 signaling and cell migration by protecting fibulin-1 from MMP-13-mediated proteolysis.","date":"2014","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/24632605","citation_count":37,"is_preprint":false},{"pmid":"20356454","id":"PMC_20356454","title":"Characterization of calumenin in mouse heart.","date":"2010","source":"BMB reports","url":"https://pubmed.ncbi.nlm.nih.gov/20356454","citation_count":36,"is_preprint":false},{"pmid":"18562801","id":"PMC_18562801","title":"Calumenin interacts with SERCA2 in rat cardiac sarcoplasmic reticulum.","date":"2008","source":"Molecules and cells","url":"https://pubmed.ncbi.nlm.nih.gov/18562801","citation_count":30,"is_preprint":false},{"pmid":"24136234","id":"PMC_24136234","title":"Calumenin-15 facilitates filopodia formation by promoting TGF-β superfamily cytokine GDF-15 transcription.","date":"2013","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/24136234","citation_count":24,"is_preprint":false},{"pmid":"25976680","id":"PMC_25976680","title":"Calumenin and fibulin-1 on tumor metastasis: 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intracellular transport and secretion of calumenin-1/2 in living cells.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22514732","citation_count":18,"is_preprint":false},{"pmid":"22178608","id":"PMC_22178608","title":"Spatio-temporal expression analysis of the calcium-binding protein calumenin in the rodent brain.","date":"2011","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/22178608","citation_count":17,"is_preprint":false},{"pmid":"33623713","id":"PMC_33623713","title":"Calumenin contributes to epithelial-mesenchymal transition and predicts poor survival in glioma.","date":"2021","source":"Translational neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/33623713","citation_count":17,"is_preprint":false},{"pmid":"28189267","id":"PMC_28189267","title":"Calumenin contributes to ER-Ca2+ homeostasis in bronchial epithelial cells expressing WT and F508del mutated CFTR and to F508del-CFTR retention.","date":"2017","source":"Cell calcium","url":"https://pubmed.ncbi.nlm.nih.gov/28189267","citation_count":17,"is_preprint":false},{"pmid":"26991433","id":"PMC_26991433","title":"Ca-Dependent Folding of Human Calumenin.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26991433","citation_count":16,"is_preprint":false},{"pmid":"31966567","id":"PMC_31966567","title":"Calumenin relieves cardiac injury by inhibiting ERS-initiated apoptosis during viral myocarditis.","date":"2017","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/31966567","citation_count":12,"is_preprint":false},{"pmid":"25823396","id":"PMC_25823396","title":"CALU polymorphism A29809G affects calumenin availability involving vascular calcification.","date":"2015","source":"Journal of molecular and cellular cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/25823396","citation_count":12,"is_preprint":false},{"pmid":"25120007","id":"PMC_25120007","title":"Biophysical characterisation of calumenin as a charged F508del-CFTR folding modulator.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25120007","citation_count":12,"is_preprint":false},{"pmid":"36246958","id":"PMC_36246958","title":"Upregulation of miR-335-5p Contributes to Right Ventricular Remodeling via Calumenin in Pulmonary Arterial Hypertension.","date":"2022","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/36246958","citation_count":11,"is_preprint":false},{"pmid":"19695248","id":"PMC_19695248","title":"Pleiotropic roles of calumenin (calu-1), a calcium-binding ER luminal protein, in Caenorhabditis elegans.","date":"2009","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/19695248","citation_count":10,"is_preprint":false},{"pmid":"26161649","id":"PMC_26161649","title":"Fibulin-1C, C1 Esterase Inhibitor and Glucose Regulated Protein 75 Interact with the CREC Proteins, Calumenin and Reticulocalbin.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26161649","citation_count":7,"is_preprint":false},{"pmid":"29282541","id":"PMC_29282541","title":"Creatine phosphate disodium salt protects against Dox-induced cardiotoxicity by increasing calumenin.","date":"2017","source":"Medical molecular morphology","url":"https://pubmed.ncbi.nlm.nih.gov/29282541","citation_count":7,"is_preprint":false},{"pmid":"30710294","id":"PMC_30710294","title":"Calcium-Induced Protein Folding in Calumenin and Calmodulin.","date":"2019","source":"Methods in molecular biology (Clifton, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/30710294","citation_count":6,"is_preprint":false},{"pmid":"34063287","id":"PMC_34063287","title":"S100A6, Calumenin and Cytohesin 2 as Biomarkers for Cutaneous Involvement in Systemic Sclerosis Patients: A Case Control Study.","date":"2021","source":"Journal of personalized medicine","url":"https://pubmed.ncbi.nlm.nih.gov/34063287","citation_count":6,"is_preprint":false},{"pmid":"35412165","id":"PMC_35412165","title":"Calumenin knockdown, by intronic artificial microRNA, to improve expression efficiency of the recombinant human coagulation factor IX.","date":"2022","source":"Biotechnology letters","url":"https://pubmed.ncbi.nlm.nih.gov/35412165","citation_count":4,"is_preprint":false},{"pmid":"30710295","id":"PMC_30710295","title":"Measuring Calumenin Impact on ER-Calcium Depletion Using Transient Calumenin Overexpression and Silencing.","date":"2019","source":"Methods in molecular biology (Clifton, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/30710295","citation_count":3,"is_preprint":false},{"pmid":"39583311","id":"PMC_39583311","title":"Dissecting the Implications of Calumenin in Malignancy and Heterogeneity of the Microenvironment of Clear Cell Renal Cell Carcinoma Using Multi-Omics Data.","date":"2024","source":"Phenomics (Cham, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/39583311","citation_count":3,"is_preprint":false},{"pmid":"36979156","id":"PMC_36979156","title":"Calumenin, a Ca2+ Binding Protein, Is Required for Dauer Formation in Caenorhabditis elegans.","date":"2023","source":"Biology","url":"https://pubmed.ncbi.nlm.nih.gov/36979156","citation_count":2,"is_preprint":false},{"pmid":"31938169","id":"PMC_31938169","title":"Calumenin DNA methylation and gene expression in viral myocarditis.","date":"2018","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/31938169","citation_count":1,"is_preprint":false},{"pmid":"40922754","id":"PMC_40922754","title":"Silencing Calumenin Expression via Artificial MicroRNA, a Potential Breakthrough for Inhibiting Proliferation, Halting Migration, and Triggering Apoptosis in Breast Cancer Cells.","date":"2025","source":"Advanced pharmaceutical bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/40922754","citation_count":1,"is_preprint":false},{"pmid":"40496395","id":"PMC_40496395","title":"Mechanism of myocardial damage induced by doxorubicin via calumenin-regulated mitochondrial dynamics and the calcium-Cx43 pathway.","date":"2025","source":"World journal of cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/40496395","citation_count":1,"is_preprint":false},{"pmid":"41557802","id":"PMC_41557802","title":"Calumenin prevents fibroblast senescence and lung aging by promoting vimentin proteostasis.","date":"2026","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/41557802","citation_count":0,"is_preprint":false},{"pmid":"41090186","id":"PMC_41090186","title":"Calumenin, A Calcium-Binding Modulatory Protein, Effective in Pathological Calcifications and Cancers, With Therapeutic Application Promise.","date":"2025","source":"FASEB bioAdvances","url":"https://pubmed.ncbi.nlm.nih.gov/41090186","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"sonnet_model":"claude-sonnet-4-6","sonnet_input_tokens":20181,"sonnet_output_tokens":4634,"sonnet_usd":0.1301,"sonnet_elapsed_seconds":78.5,"stage1_stop_reason":"end_turn"},"stage2":{"opus_model":"claude-opus-4-8","opus_input_tokens":12696,"opus_output_tokens":5261,"opus_usd":0.195,"opus_elapsed_seconds":59.7,"stage2_stop_reason":"end_turn"},"total_usd":0.3251},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"Calumenin is a Ca2+-binding protein with six EF-hand motifs retained in the endoplasmic reticulum; the C-terminal tetrapeptide HDEF is responsible for ER retention, with the Phe residue being a novel component of the ER retention signal.\",\n      \"method\": \"Retention assay, immunostaining with confocal laser microscope, deglycosylation assay, Ca2+-binding assay with purified protein\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (retention assay, immunostaining, deglycosylation, direct Ca2+-binding with purified protein) in a single rigorous study\",\n      \"pmids\": [\"9218460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Recombinant human calumenin binds Ca2+ through all 7 EF-hand domains with low affinity (Kd ~1/1.6×10³ M⁻¹ per site), consistent with a role in Ca2+-dependent ER processes.\",\n      \"method\": \"Microdialysis Ca2+-binding experiments with recombinant human calumenin expressed in E. coli\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro binding assay with purified recombinant protein, single lab but well-characterized method\",\n      \"pmids\": [\"9675259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human calumenin localizes to both the ER and Golgi complex in multiple human cell lines, and a glycosylated, endoglycosidase H-resistant form is secreted into the culture medium, indicating transit through the Golgi and extracellular release.\",\n      \"method\": \"Immunofluorescence, immunoelectron microscopy, endoglycosidase H treatment, Western blot of conditioned medium\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal localization and biochemical methods in several cell lines, single lab\",\n      \"pmids\": [\"10222138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Calumenin binds serum amyloid P component (SAP) in a Ca2+-dependent manner; this interaction was identified by affinity chromatography and verified by surface plasmon resonance.\",\n      \"method\": \"Affinity chromatography with immobilized recombinant calumenin, amino acid sequencing of eluate, surface plasmon resonance\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pull-down plus SPR confirmation, but single lab and functional consequence not fully established\",\n      \"pmids\": [\"10631319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Calumenin-2 interacts with ryanodine receptor 1 (RyR1) in rabbit skeletal sarcoplasmic reticulum in a Ca2+-dependent manner; the second EF-hand domain of calumenin is essential for this interaction. Overexpression of calumenin-2 in C2C12 myotubes increases caffeine-induced Ca2+ release but decreases depolarization-induced Ca2+ release.\",\n      \"method\": \"GST pull-down, co-immunoprecipitation, EF-hand deletion constructs, adenovirus-mediated overexpression, Ca2+ imaging\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal methods (GST pull-down, co-IP, deletion mutagenesis, functional Ca2+ imaging), single lab\",\n      \"pmids\": [\"16527250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Calumenin overexpression in neonatal rat cardiomyocytes prolongs time to 50% Ca2+ baseline (T50) by inhibiting SERCA2-mediated Ca2+ uptake into the SR; co-immunoprecipitation demonstrates a direct interaction between calumenin and SERCA2.\",\n      \"method\": \"Adenovirus-mediated overexpression, Ca2+ transient measurement, oxalate-supported Ca2+ uptake assay, co-immunoprecipitation\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP, functional Ca2+ assay, Ca2+ uptake assay), single lab\",\n      \"pmids\": [\"18562801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Calumenin (calu-1) in C. elegans is required for fertility, locomotion, body size, defecation, and pharyngeal pumping; genetic analysis suggests calu-1 regulates pharyngeal pumping together with the IP3 receptor (itr-1).\",\n      \"method\": \"Mutant analysis, genetic epistasis (calu-1 and itr-1 double mutant analysis), behavioral assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in vivo with multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"19695248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Calumenin interacts with SERCA2 in mouse cardiac SR; the binding is favored in the E1 state of SERCA2 (reduced by thapsigargin, vanadate, or ATP). GST pull-down with deletion fragments maps the interaction to residues 132–222 of calumenin and residues 853–892 (L4 luminal domain) of SERCA2. Calumenin knockdown (80%) in HL-1 cells enhances Ca2+ transient amplitude and increases Ca2+ sensitivity of SERCA2.\",\n      \"method\": \"GST pull-down with deletion fragments, co-immunoprecipitation, immunocytochemistry, siRNA knockdown, oxalate-supported Ca2+ uptake assay, state-specific SERCA2 inhibitors\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — domain mapping by GST pull-down, co-IP, functional Ca2+ uptake with KD, and state-dependent interaction, multiple orthogonal methods\",\n      \"pmids\": [\"19740751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Calumenin-1/2 secretion requires microtubule integrity and is mediated by motor proteins Kif5b and cytoplasmic dynein; the export signal maps to amino acids 20–46, and asparagine at position 131 is required for protein stabilization.\",\n      \"method\": \"Time-lapse live-cell imaging of calu-1/2-EGFP, microtubule disruption, dominant-negative motor protein expression, deletion mapping\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging plus motor protein and domain mutant experiments, single lab\",\n      \"pmids\": [\"22514732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Calumenin is identified as a binding partner of G551D-CFTR by co-immunoprecipitation and mass spectrometry, and is more abundant in the G551D-CFTR complex than in the wild-type CFTR complex; the interaction was confirmed by surface plasmon resonance.\",\n      \"method\": \"Co-immunoprecipitation, 2D-gel electrophoresis, mass spectrometry, surface plasmon resonance, immunofluorescence\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP/MS plus SPR confirmation, single lab, functional role in CFTR maturation inferred but not fully demonstrated\",\n      \"pmids\": [\"22768251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Calumenin overexpression in neonatal rat ventricular cardiomyocytes reduces ER stress markers (GRP78, p-PERK, p-eIF2α) and ER-initiated apoptosis markers (CHOP, p-JNK) during tunicamycin-induced ER stress, and reduces apoptosis as measured by TUNEL assay.\",\n      \"method\": \"Recombinant adenovirus-mediated overexpression (7.5-fold), Western blot for ER stress markers, TUNEL assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional overexpression with multiple marker readouts, single lab\",\n      \"pmids\": [\"24012670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Calumenin isoform Calu-15 promotes filopodia formation and cell migration by: (1) shuttling between nucleus and cytoplasm via interaction with importin α, Ran GTPase, and CRM1; (2) requiring CK2-dependent phosphorylation of Thr-73 for nuclear import; and (3) binding the GDF-15 promoter in the nucleus to increase GDF-15 transcription.\",\n      \"method\": \"Alternative splicing cloning, co-immunoprecipitation (importin α, Ran, CRM1), CK2 inhibition, Thr-73 point mutation, chromatin immunoprecipitation, promoter-reporter assay, filopodia imaging\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP, mutagenesis, ChIP, reporter assay), single lab, specific to Calu-15 isoform\",\n      \"pmids\": [\"24136234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Extracellular calumenin binds and stabilizes fibulin-1, protecting it from MMP-13-mediated proteolysis; this suppresses ERK1/2 signaling and inhibits cell migration. The minimal functional domain maps to residues 74–138 and 214–280. Calumenin/fibulin-1 also interact with fibronectin and signal through syndecan-4 and α5β1-integrin to suppress pERK1/2.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, in vitro MMP-13 cleavage protection assay, ERK1/2 phosphorylation Western blot, migration assay, domain deletion mapping\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, in vitro MMP protection, signaling readouts, receptor blocking), replicated across multiple cell types in single study\",\n      \"pmids\": [\"24632605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Calumenin reduces F508del-CFTR aggregation in vitro, similar to an intrinsically disordered protein (IDP), and shows altered trafficking in bronchial cells expressing F508del-CFTR, indicating a direct role in mutant CFTR folding/processing.\",\n      \"method\": \"Aggregation assay (recombinant calumenin + F508del-CFTR), fluorescence microscopy-based trafficking analysis, biophysical characterization\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — in vitro aggregation assay plus imaging, single lab, functional mechanism not fully resolved\",\n      \"pmids\": [\"25120007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CALU polymorphism rs1043550 (A29809G) reduces calumenin mRNA stability by ~30% as shown by a luciferase reporter assay in vascular cells; reduced calumenin availability correlates with impaired gamma-carboxylation of matrix-Gla-protein and altered vascular calcification.\",\n      \"method\": \"Luciferase reporter system (mRNA stability assay), immunohistochemistry, clinical genotyping, extracellular matrix mineralization assay in hVSMC\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay for mRNA stability plus cell culture model, single lab\",\n      \"pmids\": [\"25823396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Calumenin and reticulocalbin interact with fibulin-1C, C1 esterase inhibitor, and GRP75 (Grp75); calumenin binds fibulin-1C with Kd ~50–60 nM and C1 esterase inhibitor with Kd ~150 nM; the calumenin–C1 esterase inhibitor interaction is Ca2+-dependent (detectable at 3.5 mM, absent at 0.1 mM Ca2+).\",\n      \"method\": \"Affinity purification, co-immunoprecipitation, mass spectrometry, surface plasmon resonance\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP/MS plus SPR quantification, single lab\",\n      \"pmids\": [\"26161649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Calumenin undergoes Ca2+-induced folding: in low Ca2+, the protein is largely disordered; upon Ca2+ addition it adopts a compact, predominantly alpha-helical trilobal structure. This conformational switch is reversible.\",\n      \"method\": \"Circular dichroism spectroscopy, small-angle X-ray scattering (SAXS), analytical size-exclusion chromatography, surface plasmon resonance\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple biophysical methods (CD, SAXS, SEC, SPR) in a single rigorous study demonstrating Ca2+-dependent folding\",\n      \"pmids\": [\"26991433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Calumenin modulates SERCA pump activity and is a key regulator of ER Ca2+ homeostasis in bronchial epithelial cells expressing both wild-type and F508del-CFTR; reducing calumenin expression partially restores F508del-CFTR activity.\",\n      \"method\": \"siRNA knockdown, ER Ca2+ measurement, SERCA activity assay, CFTR functional assay\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional knockdown with Ca2+ and CFTR activity readouts, single lab\",\n      \"pmids\": [\"28189267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Calumenin acts as a chaperone for vimentin proteostasis in lung fibroblasts: it collaborates with the TRiC chaperonin complex to facilitate proper vimentin folding, and recruits the CCT2 subunit to degrade misfolded vimentin aggregates. Fibroblast-specific knockout of calumenin promotes vimentin aggregate accumulation and profibrotic factor (migracytosis) secretion, exacerbating fibroblast senescence and lung aging. External profibrotic stimuli trigger calcium transients that induce calumenin degradation.\",\n      \"method\": \"CRISPR-based genetic screen, fibroblast-specific knockout mouse, co-immunoprecipitation (TRiC/CCT2), live-cell imaging, Ca2+ imaging, Western blot, electron microscopy\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR screen plus fibroblast-specific KO with multiple orthogonal methods (co-IP, imaging, Ca2+ measurement), multiple phenotypic readouts\",\n      \"pmids\": [\"41557802\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Calumenin is a Ca2+-dependent folding sensor and multi-functional chaperone of the secretory pathway (ER/SR lumen) that, upon Ca2+ binding, transitions from a disordered to a compact trilobal structure, enabling it to regulate SERCA2 (inhibiting SR Ca2+ uptake), RyR1/RyR2 (modulating Ca2+ release), CFTR maturation, vimentin proteostasis (via TRiC/CCT2 recruitment), and extracellular functions including fibulin-1 stabilization (protecting it from MMP-13 cleavage) to suppress ERK1/2-dependent cell migration; additionally, the Calu-15 splice isoform undergoes CK2-dependent phosphorylation at Thr-73 for nuclear import and transcriptionally upregulates GDF-15 to promote filopodia formation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Calumenin (CALU) is a Ca2+-binding protein of the secretory pathway that functions as a Ca2+-dependent folding sensor and multi-functional chaperone regulating Ca2+ handling, protein proteostasis, and extracellular signaling [#0, #16]. It is retained in the ER via a C-terminal HDEF tetrapeptide and binds Ca2+ through multiple low-affinity EF-hand motifs, and upon Ca2+ binding it switches reversibly from a largely disordered state to a compact, alpha-helical trilobal fold that underlies its activity [#0, #1, #16]. A fraction transits the Golgi and is secreted, with export depending on microtubule integrity and the motors Kif5b and cytoplasmic dynein [#2, #8]. In the SR/ER lumen, calumenin directly binds SERCA2 in its E1 state to inhibit Ca2+ uptake and binds RyR1 in a Ca2+-dependent manner to modulate Ca2+ release, thereby tuning intracellular Ca2+ homeostasis [#5, #7, #4]. Through this Ca2+/SERCA control it also governs ER Ca2+ levels in bronchial epithelium, where its reduction partially restores F508del-CFTR activity, and it physically associates with mutant CFTR to influence its folding and trafficking [#9, #13, #17]. Calumenin further acts as a chaperone for vimentin proteostasis by collaborating with the TRiC chaperonin and recruiting CCT2 to clear misfolded vimentin aggregates, with loss promoting fibroblast senescence and lung aging [#18]. Extracellularly, calumenin binds and stabilizes fibulin-1, protecting it from MMP-13 cleavage and suppressing ERK1/2-dependent cell migration via syndecan-4 and \\u03b15\\u03b21-integrin signaling [#12]. A distinct Calu-15 splice isoform undergoes CK2-dependent Thr-73 phosphorylation enabling nuclear import and transcriptional upregulation of GDF-15 to promote filopodia formation [#11].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established calumenin as an ER-resident Ca2+-binding protein and defined a novel ER retention signal, framing it as a luminal Ca2+-handling factor.\",\n      \"evidence\": \"Retention assay, immunostaining, deglycosylation, and direct Ca2+-binding with purified protein\",\n      \"pmids\": [\"9218460\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role beyond Ca2+ binding not addressed\", \"Affinity and stoichiometry of Ca2+ sites not quantified here\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Quantified calumenin's Ca2+ binding as multi-site low-affinity, consistent with a buffering/sensing role rather than high-affinity signaling.\",\n      \"evidence\": \"Microdialysis Ca2+-binding with recombinant human protein\",\n      \"pmids\": [\"9675259\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational consequences of binding not resolved\", \"In vivo relevance of low affinity untested\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed calumenin is not strictly ER-confined but transits the Golgi and is secreted, opening an extracellular dimension to its function.\",\n      \"evidence\": \"Immunofluorescence, immunoEM, endoglycosidase H, Western blot of conditioned medium\",\n      \"pmids\": [\"10222138\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Extracellular function unknown at this stage\", \"Mechanism of escape from HDEF retention unclear\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified the first Ca2+-dependent binding partner (SAP), establishing calumenin as a Ca2+-regulated interaction protein.\",\n      \"evidence\": \"Affinity chromatography, sequencing, and surface plasmon resonance\",\n      \"pmids\": [\"10631319\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of SAP binding not established\", \"Single lab, no in vivo validation\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked calumenin to excitation-contraction coupling by mapping a Ca2+-dependent RyR1 interaction and demonstrating functional modulation of Ca2+ release.\",\n      \"evidence\": \"GST pull-down, co-IP, EF-hand deletion, overexpression, Ca2+ imaging in C2C12 myotubes\",\n      \"pmids\": [\"16527250\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect RyR1 contact not resolved\", \"Physiological role in intact muscle untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Established a direct calumenin\\u2013SERCA2 interaction that inhibits SR Ca2+ uptake, defining a cardiac Ca2+-handling function.\",\n      \"evidence\": \"Adenoviral overexpression, Ca2+ transients, oxalate-supported uptake, co-IP in cardiomyocytes\",\n      \"pmids\": [\"18562801\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interaction interface not mapped here\", \"Endogenous loss-of-function not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Mapped the calumenin\\u2013SERCA2 interface and showed state-specific (E1) binding plus knockdown enhancement of Ca2+ transients, establishing mechanism and direction of regulation.\",\n      \"evidence\": \"GST pull-down with deletion fragments, co-IP, siRNA knockdown, state-specific inhibitors, Ca2+ uptake in HL-1 cells\",\n      \"pmids\": [\"19740751\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of E1 preference not resolved\", \"Regulation by Ca2+ occupancy of EF-hands unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrated organismal requirement for calumenin in C. elegans and genetic interaction with the IP3 receptor, connecting it to whole-animal Ca2+ physiology.\",\n      \"evidence\": \"Mutant analysis and genetic epistasis with itr-1, behavioral assays\",\n      \"pmids\": [\"19695248\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of IP3R interplay unknown\", \"Mammalian relevance not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the cellular machinery and signals for calumenin secretion, showing microtubule- and motor-dependent export.\",\n      \"evidence\": \"Live-cell imaging, microtubule disruption, dominant-negative motors, deletion mapping\",\n      \"pmids\": [\"22514732\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How export bypasses ER retention not explained\", \"Single lab\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Connected calumenin to disease-relevant CFTR processing by identifying it as a partner enriched in the G551D-CFTR complex.\",\n      \"evidence\": \"Co-IP, 2D-gel, mass spectrometry, SPR, immunofluorescence\",\n      \"pmids\": [\"22768251\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional effect on CFTR maturation inferred, not demonstrated\", \"Direct vs complex-mediated binding unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed a cytoprotective role: calumenin overexpression suppresses ER stress and apoptosis pathways in cardiomyocytes.\",\n      \"evidence\": \"Adenoviral overexpression, ER-stress and apoptosis marker Westerns, TUNEL\",\n      \"pmids\": [\"24012670\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Loss-of-function ER-stress phenotype untested\", \"Mechanism linking Ca2+ regulation to ER stress not dissected\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Uncovered a non-canonical nuclear/transcriptional pathway through the Calu-15 isoform driving filopodia formation via GDF-15 upregulation.\",\n      \"evidence\": \"Splice cloning, co-IP (importin \\u03b1/Ran/CRM1), CK2 inhibition, Thr-73 mutation, ChIP, reporter assays, filopodia imaging\",\n      \"pmids\": [\"24136234\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Isoform-specific physiological role in vivo unknown\", \"Generality beyond Calu-15 unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined an extracellular tumor-suppressive function: calumenin stabilizes fibulin-1 against MMP-13 to suppress ERK1/2-dependent migration through receptor signaling.\",\n      \"evidence\": \"Co-IP, siRNA, in vitro MMP-13 protection, ERK Westerns, migration assays, domain mapping\",\n      \"pmids\": [\"24632605\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance to tumor progression not established here\", \"Stoichiometry of fibulin-1/fibronectin complex unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed calumenin behaves like an intrinsically disordered chaperone reducing F508del-CFTR aggregation, linking biophysics to mutant CFTR handling.\",\n      \"evidence\": \"In vitro aggregation assay with recombinant calumenin, trafficking imaging\",\n      \"pmids\": [\"25120007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of trafficking change not resolved\", \"Whether effect is direct chaperoning unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided a clinical/regulatory link by showing a CALU polymorphism reduces mRNA stability and correlates with altered vascular calcification.\",\n      \"evidence\": \"Luciferase mRNA-stability reporter, IHC, genotyping, mineralization assay in hVSMC\",\n      \"pmids\": [\"25823396\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causality between calumenin level and calcification not proven\", \"Mechanistic link to gamma-carboxylation correlative\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Quantified high-affinity extracellular/luminal partner interactions (fibulin-1C, C1 esterase inhibitor, GRP75), refining calumenin's interactome and Ca2+-dependence.\",\n      \"evidence\": \"Affinity purification, co-IP, mass spectrometry, SPR\",\n      \"pmids\": [\"26161649\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of C1 inhibitor and GRP75 binding unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Provided the structural basis for calumenin function: a reversible Ca2+-induced disorder-to-compact-trilobal-fold transition that gates its activity.\",\n      \"evidence\": \"CD, SAXS, analytical SEC, SPR\",\n      \"pmids\": [\"26991433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure not determined\", \"How fold change maps onto partner binding not directly shown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Integrated calumenin's SERCA regulation with CFTR rescue, showing knockdown restores F508del-CFTR activity via ER Ca2+ control.\",\n      \"evidence\": \"siRNA knockdown, ER Ca2+ and SERCA activity assays, CFTR functional assay in bronchial cells\",\n      \"pmids\": [\"28189267\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Therapeutic translation untested\", \"Direct vs Ca2+-mediated CFTR effect not fully separated\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Established calumenin as a proteostasis chaperone for vimentin via TRiC/CCT2, with loss driving fibroblast senescence and lung aging, expanding its role beyond Ca2+ handling.\",\n      \"evidence\": \"CRISPR screen, fibroblast-specific KO mouse, co-IP (TRiC/CCT2), live-cell and Ca2+ imaging, EM\",\n      \"pmids\": [\"41557802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Ca2+-induced calumenin degradation is triggered mechanistically unresolved\", \"Generality of vimentin chaperoning across cell types untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How calumenin's Ca2+-gated conformational switch is mechanistically coupled to its diverse outputs (SERCA/RyR regulation, CFTR folding, vimentin chaperoning, fibulin-1 stabilization) remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model linking fold state to partner selection\", \"Tissue-specific division of labor among functions unclear\", \"No high-resolution structure of any calumenin-partner complex\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [13, 18]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 7, 4]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 17]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 12]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [10, 16]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [13, 18]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5, 7]}\n    ],\n    \"complexes\": [\"TRiC/CCT chaperonin (associated)\", \"calumenin/fibulin-1/fibronectin extracellular complex\"],\n    \"partners\": [\"ATP2A2\", \"RYR1\", \"FBLN1\", \"CFTR\", \"CCT2\", \"SERPING1\", \"HSPA9\", \"APCS\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win"}}