Affinage

CALM3

Calmodulin-3 · UniProt P0DP25

Length
149 aa
Mass
16.8 kDa
Annotated
2026-06-09
16 papers in source corpus 9 papers cited in narrative 9 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CALM3 encodes one of the calmodulin proteins and functions principally as a Ca2+-sensing regulator of cardiac ion channels, where pathogenic missense variants cause dominant arrhythmogenic disease (PMID:26969752, PMID:35225649). Disease-associated substitutions reduce the Ca2+-binding affinity of calmodulin—for example E141G lowers affinity ~11-fold and N138K reduces C-terminal domain affinity ~10-fold—and this defect translates into dysregulation of distinct effectors: loss of CaV1.2 (ICaL) inactivation, modest accentuation of NaV1.5 late current, potentiation of the IKs current, or RyR2-dependent spontaneous arrhythmogenic Ca2+ waves (PMID:26969752, PMID:27516456, PMID:35225649). The pathogenic effect is functionally dominant, as even a 1:3 ratio of mutant A103V-CaM to wild-type CaM is sufficient to provoke Ca2+ disturbances, and these variants underlie long QT syndrome and CPVT-type Ca2+ release phenotypes (PMID:27516456, PMID:35225649). Suppression of mutant CALM3 transcript with replacement by wild-type calmodulin cDNA rescues the prolonged action potential duration in patient iPSC-derived cardiomyocytes, establishing the mutant transcript as the disease driver (PMID:39069900). CALM3 is the lowest translational contributor among the three calmodulin genes in the human left ventricle (~11% of calmodulin protein), a low output that correlates with weaker negative selection against its missense variants and milder clinical phenotypes (PMID:41846582). Beyond the heart, the longest Calm3 mRNA isoform retains a 3'-UTR intron bound by Staufen2, which directs activity-dependent dendritic localization of the transcript without altering its stability (PMID:28765142).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 1998 Medium

    Establishing that the three calmodulin genes are differentially regulated, this work showed CALM3 is transcribed at least 5-fold more actively than CALM1 or CALM2 in proliferating cells and identified the 5'-UTR as required for full promoter activity.

    Evidence Nuclear run-on transcription assay and luciferase reporter transfections with CALM gene 5'-flanking sequences in human teratoma cells

    PMID:9681195

    Open questions at the time
    • Transcriptional behavior in non-proliferating or cardiac tissue not addressed
    • Does not link transcription rate to functional protein output
  2. 2016 High

    Linking CALM3 missense variants to a defined molecular lesion, these studies demonstrated that pathogenic substitutions reduce calmodulin Ca2+-binding affinity and dysregulate cardiac channels in a dominant fashion, distinguishing channel-specific mechanisms (CaV1.2/NaV1.5 vs RyR2).

    Evidence In vitro Ca2+-binding assays, whole-cell patch-clamp of CaV1.2/NaV1.5/ICaL, RyR2 binding and Ca2+-wave imaging in permeabilized cardiomyocytes

    PMID:26969752 PMID:27516456

    Open questions at the time
    • In vivo arrhythmia phenotype not established
    • Structural basis of effector selectivity not resolved
    • Why affinity loss maps to distinct channels for different variants unexplained
  3. 2017 High

    Revealing a non-cardiac role for Calm3 RNA, this work showed an intron-retaining 3'-UTR isoform is delivered to dendrites by Staufen2 in an activity-dependent manner, implicating CALM3 in localized neuronal mRNA transport.

    Evidence Stau2 iCLIP, FISH dendritic localization imaging, Stau2 knockdown, and NMDA stimulation in neurons

    PMID:28765142

    Open questions at the time
    • Local translation of the dendritic isoform not demonstrated
    • Functional consequence for synaptic calmodulin signaling unknown
  4. 2022 High

    Explaining phenotypic variability, the N138K variant was shown to combine milder ICaL impairment with unexpected IKs potentiation, accounting for a milder LQTS presentation than severe de novo CaM variants.

    Evidence Stoichiometric Ca2+ titrations, patch-clamp of ICaL and IKs, and membrane-expression fluorescence assays for CaV1.2 and Kv7.1

    PMID:35225649

    Open questions at the time
    • Mechanism of IKs potentiation by mutant CaM not defined
    • Clinical penetrance link is correlative
  5. 2024 Medium

    Demonstrating therapeutic tractability and confirming the mutant transcript as the causal driver, a suppression-and-replacement construct knocking down CALM3 and replacing it with WT calmodulin rescued the action potential phenotype in patient cardiomyocytes.

    Evidence CALM3-specific shRNA knockdown plus shRNA-immune CALM1 cDNA, APD90 voltage-dye measurement in CALM3-D130G patient iPSC-derived cardiomyocytes

    PMID:39069900

    Open questions at the time
    • Single patient genotype tested
    • In vivo efficacy and safety not established
    • Long-term durability unknown
  6. 2024 Low

    Extending CALM3 function to development, knockdown studies indicated CALM3 facilitates neuronal differentiation of mesenchymal stem cells and is negatively regulated by miR-543.

    Evidence siRNA knockdown of CALM3, RT-qPCR and western blot of neuronal markers, and miRNA mimic transfection in hUC-MSCs

    PMID:39444227

    Open questions at the time
    • Single lab with mRNA-level readout and no direct biochemical mechanism
    • Effect is partial reversal only
    • Relevance to physiological neurogenesis unclear
  7. 2026 Medium

    Quantifying CALM3's contribution, ribosome profiling established that CALM3 produces only ~11% of ventricular calmodulin protein, providing a translational basis for the weaker selection against and milder phenotype of CALM3 variants.

    Evidence Paired RNA-seq and ribosome profiling of human left ventricle, gnomAD selection analysis, and International Calmodulinopathy Registry clinical data

    PMID:41846582

    Open questions at the time
    • Observational/bioinformatic rather than experimental
    • Causal link between low translation and mild phenotype is inferential

Open questions

Synthesis pass · forward-looking unresolved questions
  • How a single calmodulin variant selectively dysregulates one channel versus another, and the structural and recruitment basis for effector specificity, remains unresolved.
  • No structural model linking affinity loss to specific channel targeting
  • In vivo cardiac consequences of CALM3 variants not modeled
  • Physiological role of dendritic CALM3 isoform unestablished

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 3 GO:0140299 molecular sensor activity 2
Localization
GO:0005829 cytosol 2
Pathway
R-HSA-162582 Signal Transduction 3 R-HSA-397014 Muscle contraction 2
Partners
CACNA1CKCNQ1RYR2SCN5ASTAU2

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2016 The CALM3-encoded calmodulin variant E141G reduces Ca2+-binding affinity 11-fold and causes a functionally dominant loss of inactivation in the cardiac L-type calcium channel CaV1.2, mild accentuation of NaV1.5 late current, but no effect on intracellular RyR2-mediated calcium release. In vitro Ca2+-binding affinity assays, whole-cell patch-clamp of CaV1.2 and NaV1.5, intracellular Ca2+ release measurements in cardiomyocytes Circulation. Cardiovascular genetics High 26969752
2016 The CALM3 variant A103V modestly reduces CaM Ca2+-binding affinity (~3-fold), does not alter CaM binding to RyR2, but promotes spontaneous arrhythmogenic Ca2+ waves and sparks in permeabilized cardiomyocytes via RyR2 dysregulation; even a 1:3 ratio of A103V-CaM:WT-CaM is sufficient to evoke these Ca2+ disturbances, demonstrating functional dominance. A103V has significantly less effect on L-type Ca2+ current inactivation and does not alter action potential duration compared with LQTS-associated CaM variants. In vitro Ca2+-binding affinity measurement, RyR2-CaM binding assay, Ca2+ handling assays in permeabilized cardiomyocytes, patch-clamp of L-type Ca2+ current, action potential recording in intact cardiomyocytes Circulation. Arrhythmia and electrophysiology High 27516456
2022 The CALM3 variant N138K reduces Ca2+-binding affinity of the CaM C-terminal domain 10-fold compared with WT-CaM, slows CaV1.2 (ICaL) inactivation, and unexpectedly potentiates IKs (slow delayed rectifier K+ current) density; this combined effect (milder ICaL impairment + IKs augmentation) explains the milder LQTS phenotype compared with previously reported severe de novo CaM variants. Stoichiometric Ca2+ titrations and equilibrium titrations, whole-cell patch-clamp (ICaL and IKs), optical fluorescence assays for Cav1.2 and Kv7.1 membrane expression Circulation. Arrhythmia and electrophysiology High 35225649
2017 The longest isoform of Calm3 mRNA, which contains a retained intron in its 3'-UTR, is localized to neuronal dendrites; Staufen2 (Stau2) binds this retained intron and mediates dendritic localization without affecting mRNA stability. NMDA-mediated synaptic activity specifically promotes dendritic localization of this Calm3 isoform, while inhibition of synaptic activity reduces it. iCLIP (individual-nucleotide resolution CLIP) for Stau2 binding mapping, fluorescence in situ hybridization/imaging for dendritic mRNA localization, Stau2 knockdown, NMDA stimulation and activity inhibition experiments in neurons EMBO reports High 28765142
2024 A suppression-and-replacement (SupRep) gene therapy construct containing CALM3-specific shRNA (94% knockdown efficiency) plus a shRNA-immune CALM1 cDNA replacement shortens the pathologically prolonged action potential duration (APD90) in CALM3-D130G patient-derived iPSC-derived cardiomyocytes, demonstrating that knocking down mutant CALM3 transcript and replacing with WT calmodulin is sufficient to rescue the electrophysiological phenotype. shRNA knockdown efficiency assay (RT-qPCR in TSA201 cells), voltage-sensing dye APD90 measurement in patient iPSC-derived cardiomyocytes Circulation. Arrhythmia and electrophysiology Medium 39069900
1998 CALM3 is at least 5-fold more actively transcribed than CALM1 or CALM2 in proliferating human teratoma cells; the 5'-untranslated regions of the CALM genes are necessary to recover full promoter activation in transient transfection reporter assays. Nuclear run-on transcription assay, mRNA quantification, luciferase reporter transfection assays with CALM gene 5'-flanking sequences including or excluding 5'-UTR Cell calcium Medium 9681195
2026 Ribosome profiling of human left ventricular tissue shows that CALM3 accounts for only ~11% of calmodulin protein produced in the ventricles (vs. ~44.8% for CALM1 and ~44.2% for CALM2), and CALM3 mRNA constitutes ~21.3% of calmodulin-coding mRNA; this lower translational contribution correlates with less negative selection against CALM3 missense variants and a lower frequency of cardiac events in CALM3 variant carriers compared with CALM1 and CALM2 variant carriers. GTEx RNA-seq data analysis, paired RNA-seq and ribosome profiling of human left ventricle, gnomAD variant analysis, International Calmodulinopathy Registry clinical data Europace Medium 41846582
1997 Screening of the CALM3 gene by PCR-SSCP and RT-PCR in Alzheimer's disease patients detected point mutations only in intronic flanking regions of exons 3 and 4; no structural changes were found in the regions encoding the Ca2+-binding domains of CALM3, and no alterations in CALM3 transcripts were detected in apoE ε4 allele carriers. PCR-SSCP analysis of genomic DNA, RT-PCR of CALM3 transcripts from patient lymphoblasts Neuroscience letters Low 9237482
2024 Knockdown of CALM3 in human umbilical cord mesenchymal stem cells (hUC-MSCs) partially reversed DMSO/BHA/DMEM-induced upregulation of neuronal differentiation markers (NSE, NeuN, NF-M mRNA), indicating that CALM3 expression facilitates neuronal differentiation of these cells. hsa-miR-543 negatively regulates CALM3 expression and exerts an opposing effect on neuronal differentiation. siRNA knockdown of CALM3, RT-qPCR for neuronal markers and CALM3 mRNA, western blotting for CALM3 protein, miRNA mimic transfection International journal of developmental neuroscience Low 39444227

Source papers

Stage 0 corpus · 16 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2016 Spectrum and Prevalence of CALM1-, CALM2-, and CALM3-Encoded Calmodulin Variants in Long QT Syndrome and Functional Characterization of a Novel Long QT Syndrome-Associated Calmodulin Missense Variant, E141G. Circulation. Cardiovascular genetics 110 26969752
1993 Localization of the human bona fide calmodulin genes CALM1, CALM2, and CALM3 to chromosomes 14q24-q31, 2p21.1-p21.3, and 19q13.2-q13.3. Genomics 80 8314583
2016 Novel CPVT-Associated Calmodulin Mutation in CALM3 (CALM3-A103V) Activates Arrhythmogenic Ca Waves and Sparks. Circulation. Arrhythmia and electrophysiology 71 27516456
1998 Characterization of the human CALM2 calmodulin gene and comparison of the transcriptional activity of CALM1, CALM2 and CALM3. Cell calcium 62 9681195
2017 A retained intron in the 3'-UTR of Calm3 mRNA mediates its Staufen2- and activity-dependent localization to neuronal dendrites. EMBO reports 61 28765142
2014 The novel regulations of MEF2A, CAMKK2, CALM3, and TNNI3 in ventricular hypertrophy induced by arsenic exposure in rats. Toxicology 27 25089838
2022 Novel CALM3 Variant Causing Calmodulinopathy With Variable Expressivity in a 4-Generation Family. Circulation. Arrhythmia and electrophysiology 21 35225649
2017 ACE2, CALM3 and TNNI3K polymorphisms as potential disease modifiers in hypertrophic and dilated cardiomyopathies. Molecular and cellular biochemistry 19 28744816
2024 Single Construct Suppression and Replacement Gene Therapy for the Treatment of All CALM1-, CALM2-, and CALM3-Mediated Arrhythmia Disorders. Circulation. Arrhythmia and electrophysiology 12 39069900
1997 Mutation analysis of chromosome 19 calmodulin (CALM3) gene in Alzheimer's disease patients. Neuroscience letters 7 9237482
2020 Molecular docking studies of a-mangostin with oral cancer targets ARRB1, FLNA, CALM3 and HTT. Bioinformation 4 33214751
2014 Comprehensive analysis of the association of EGFR, CALM3 and SMARCD1 gene polymorphisms with BMD in Caucasian women. PloS one 2 25396734
2019 Correction to: ACE2, CALM3 and TNNI3K polymorphisms as potential disease modifiers in hypertrophic and dilated cardiomyopathies. Molecular and cellular biochemistry 1 30488312
2026 CALM1, CALM2, and CALM3 expression and translation efficiency provide insight into the severity of calmodulinopathy. Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology 0 41846582
2025 Flaxseed (Linum usitatissimum) Modulates Oxytocin Signaling Pathway via CALM3-mediated Calcium Signaling: A Protein-protein Interaction Network and Functional Enrichment Analysis. Basic and clinical neuroscience 0 42238753
2024 Role of hsa-miR-543-KIF5C/CALM3 pathway in neuron differentiation of embryonic mesenchymal stem cells. International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience 0 39444227

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