CaV1.2 β-subunit coordinates CaMKII-triggered cardiomyocyte death and afterdepolarizations
Excessive activation of calmodulin kinase II (CaMKII) causes arrhythmias and heart failure, but the cellular mechanisms for CaMKII-targeted proteins causing disordered cell membrane excitability and myocardial dysfunction remain uncertain. Failing human cardiomyocytes exhibit increased CaMKII and vo...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 107; no. 11; pp. 4996 - 5000 |
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Main Authors | , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
National Academy of Sciences
16.03.2010
National Acad Sciences |
Subjects | |
Online Access | Get full text |
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Summary: | Excessive activation of calmodulin kinase II (CaMKII) causes arrhythmias and heart failure, but the cellular mechanisms for CaMKII-targeted proteins causing disordered cell membrane excitability and myocardial dysfunction remain uncertain. Failing human cardiomyocytes exhibit increased CaMKII and voltage-gated Ca²⁺ channel (CaV1.2) activity, and enhanced expression of a specific CaV1.2 β-subunit protein isoform (β₂a). We recently identified CaV1.2 β₂a residues critical for CaMKII phosphorylation (Thr 498) and binding (Leu 493), suggesting the hypothesis that these amino acids are crucial for cardiomyopathic consequences of CaMKII signaling. Here we show WT β₂a expression causes cellular Ca²⁺ overload, arrhythmia-triggering cell membrane potential oscillations called early afterdepolarizations (EADs), and premature death in paced adult rabbit ventricular myocytes. Prevention of intracellular Ca²⁺ release by ryanodine or global cellular CaMKII inhibition reduced EADs and improved cell survival to control levels in WT β₂a-expressing ventricular myocytes. In contrast, expression of β₂a T498A or L493A mutants mimicked the protective effects of ryanodine or global cellular CaMKII inhibition by reducing Ca²⁺ entry through CaV1.2 and inhibiting EADs. Furthermore, CaV1.2 currents recorded from cells overexpressing CaMKII phosphorylation- or binding-incompetent β₂a subunits were incapable of entering a CaMKII-dependent high-activity gating mode (mode 2), indicating that β₂a Thr 498 and Leu 493 are required for CaV1.2 activation by CaMKII in native cells. These data show that CaMKII binding and phosphorylation sites on β₂a are concise but pivotal components of a molecular and biophysical and mechanism for EADs and impaired survival in adult cardiomyocytes. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Author contributions: O.M.K., L.S.S., T.J.H., P.J.M., and M.E.A. designed research; O.M.K., X.G., Y.W., Z.G., B.C., T.J.H., and P.J.M. performed research; X.G., M.-L.J., Z.G., I.M.G., E.D.L., and R.J.C. contributed new reagents/analytic tools; O.M.K., Y.W., B.C., L.S.S., T.J.H., P.J.M., and M.E.A. analyzed data; and O.M.K., T.J.H., and M.E.A. wrote the paper. Edited by Clara Franzini-Armstrong, University of Pennsylvania Medical Center, Philadelphia, PA, and approved February 2, 2010 (received for review November 30, 2009) |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.0913760107 |