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L-type calcium channel targeting and local signalling in cardiac myocytes

Robin M. Shaw, Henry M. Colecraft
DOI: http://dx.doi.org/10.1093/cvr/cvt021 First published online: 15 February 2013

Abstract

In the heart, Ca2+ influx via CaV1.2 L-type calcium channels (LTCCs) is a multi-functional signal that triggers muscle contraction, controls action potential duration, and regulates gene expression. The use of LTCC Ca2+ as a multi-dimensional signalling molecule in the heart is complicated by several aspects of cardiac physiology. Cytosolic Ca2+ continuously cycles between ∼100 nM and ∼1 μM with each heartbeat due to Ca2+ linked signalling from LTCCs to ryanodine receptors. This rapid cycling raises the question as to how cardiac myocytes distinguish the Ca2+ fluxes originating through L-type channels that are dedicated to contraction from Ca2+ fluxes originating from other L-type channels that are used for non-contraction-related signalling. In general, disparate Ca2+ sources in cardiac myocytes such as current through differently localized LTCCs as well as from IP3 receptors can signal selectively to Ca2+-dependent effectors in local microdomains that can be impervious to the cytoplasmic Ca2+ transients that drive contraction. A particular challenge for diversified signalling via cardiac LTCCs is that they are voltage-gated and, therefore, open and presumably flood their microdomains with Ca2+ with each action potential. Thus spatial localization of Cav1.2 channels to different types of microdomains of the ventricular cardiomyocyte membrane as well as the existence of particular macromolecular complexes in each Cav1.2 microdomain are important to effect different types of Cav1.2 signalling. In this review we examine aspects of Cav1.2 structure, targeting and signalling in two specialized membrane microdomains—transverse tubules and caveolae.

  • L-type calcium channel
  • T-tubule
  • Caveolae
  • Channel trafficking
  • Calcium signalling
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