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Ahnak1 modulates L-type Ca(2+) channel inactivation of rodent cardiomyocytes

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Item Type:Article
Title:Ahnak1 modulates L-type Ca(2+) channel inactivation of rodent cardiomyocytes
Creators Name:Alvarez, J.L. and Petzhold, D. and Pankonien, I. and Behlke, J. and Kouno, M. and Vassort, G. and Morano, I. and Haase, H.
Abstract:Ahnak1, a giant 700 kDa protein, has been implicated in Ca(2+) signalling in various cells. Previous work suggested that the interaction between ahnak1 and Cavbeta(2) subunit plays a role in L-type Ca(2+) current (I (CaL)) regulation. Here, we performed structure-function studies with the most C-terminal domain of ahnak1 (188 amino acids) containing a PxxP consensus motif (designated as 188-PSTP) using ventricular cardiomyocytes isolated from rats, wild-type (WT) mice and ahnak1-deficient mice. In vitro binding studies revealed that 188-PSTP conferred high-affinity binding to Cavbeta(2) (K (d) approximately 60 nM). Replacement of proline residues by alanines (188-ASTA) decreased Cavbeta(2) affinity about 20-fold. Both 188-PSTP and 188-ASTA were functional in ahnak1-expressing rat and mouse cardiomyocytes during whole-cell patch clamp. Upon intracellular application, they increased the net Ca(2+) influx by enhancing I (CaL) density and/or increasing I (CaL) inactivation time course without altering voltage dependency. Specifically, 188-ASTA, which failed to affect I (CaL) density, markedly slowed I (CaL) inactivation resulting in a 50-70% increase in transported Ca(2+) during a 0 mV depolarising pulse. Both ahnak1 fragments also slowed current inactivation with Ba(2+) as charge carrier. By contrast, neither 188-PSTP nor 188-ASTA affected any I (CaL) characteristics in ahnak1-deficient mouse cardiomyocytes. Our results indicate that the presence of endogenous ahnak1 is required for tuning the voltage-dependent component of I (CaL) inactivation by ahnak1 fragments. We suggest that ahnak1 modulates the accessibility of molecular determinants in Cavbeta(2) and/or scaffolds selectively different beta-subunit isoforms in the heart.
Keywords:Ahnak1-Deficient Mice, Recombinant Ahnak1 C-Terminus, Calcium Current Kinetics, Calcium Channel Beta2 Subunit, Animals, Mice, Rats
Source:Pfluegers Archiv European Journal of Physiology
Page Range:719-730
Date:September 2010
Additional Information:The original publication is available at www.springerlink.com
Official Publication:https://doi.org/10.1007/s00424-010-0853-x
PubMed:View item in PubMed

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