Single-channel gating and regulation of human L-type calcium channels in cardiomyocytes of transgenic mice |
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Authors: | Groner Ferdi Rubio Marta Schulte-Euler Patrick Matthes Jan Khan Ismail F Y Bodi Ilona Koch Sheryl E Schwartz Arnold Herzig Stefan |
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Affiliation: | Department of Pharmacology, University of Cologne, 50931, K?ln, Germany. |
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Abstract: | Overexpression of human cardiac L-type Ca(2+) channel pores (hCa(v)1.2) in mice causes heart failure. Earlier studies showed Ca(v)1.2-mRNA increase by 2.8-fold, but whole-cell current density enhancement by =1.5-fold only. Three possible explanations were examined: (1) poor translation of hCa(v)1.2 and of its accessory subunits, (2) altered sarcolemmal insertion of functional channels, and (3) lower single-channel activity of overexpressed channels. Western blots revealed a 2.7-fold increase of Ca(v)1.2 protein in transgenic myocytes, but less enhanced expression of beta(1a) and beta(1b) subunits. beta(2) and alpha(2)/delta were significantly lowered. Density of functional channels was increased by 3.0-fold. Single-channel gating was impaired in transgenic cardiomyocytes: open probability and ensemble average currents were reduced by 60%. Furthermore, channels of transgenic myocytes were not stimulated by 8-Br-cAMP, in contrast to wild-types. Expression of malcomposed, dysfunctional L-type Ca(2+) channels in murine cardiomyocytes overexpressing hCa(v)1.2 explains the moderate enhancement of whole-cell currents and illustrates compensatory mechanisms in a transgenic disease model. |
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Keywords: | Human cardiac L-type Ca2+ channel Transgenic mouse Single-channel |
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