Ca2+ influx through single L-type Ca2+ channels provides the trigger for the larger release of Ca2+ from sarcoplasmic reticulum (SR) stores that leads to muscle contraction. As such, factors that influence L-type Ca2+ channel gating are key determinants of cardiac excitation- contraction (EC) coupling. Chief among such factors are the alpha1 and beta subunit composition of the channel, and up-regulation of channel activity by protein kinase A (PKA)-mediated phosphorylation. Observed changes in the density or complement of alpha1 and beta subunits in heart failure (HF) may underlie altered L-type Ca2+ channel gating, and reduced sensitivity to PKA modulation. Therefore, such changes in channel subunit expression loom as candidate molecular mechanisms for observed EC coupling abnormalities, and loss of beneficial effects of beta-adrenergic agonists in HF. However, fundamental ambiguities regarding the exact identity and configuration of alpha1C (Cav1.2) and beta subunits of cardiac L-type channels hinder efforts to rigorously assess how their differential expression and dysregulation may contribute to cardiac pathophysiology. These gaps in knowledge seriously limit opportunities for development of novel therapeutic strategies against HF. Hence, the long-term objective of this proposal is to deepen understanding of the molecular identity and configuration of cardiac L-type channel subunits, and to bridge this basic knowledge to a new appreciation of the functional operation and modulation of these new channels in heart. Electrophysiology, recombinant Ca2+ channels, and molecular manipulation of native heart Ca2+ channels, and molecular manipulation of cardiac L-type channel structure and function. 1. Clarify the role of a post-translationally cleaved C-terminus fragment of alpha1C in turning the gating of cardiac L-type channels. 2. Elucidate molecular determinants and mechanisms of PKA modulation of cardiac L-type channels. 3. Determine functional consequences of molecular diversity of Ca2+ channel beta2 subunits generated by alternative splicing. 4. Determine the functionally dominant beta2 splice variant expressed in heart utilizing an antisense strategy.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Cardiovascular and Pulmonary Research A Study Section (CVA)
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Przywara, Dennis
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Johns Hopkins University
Biomedical Engineering
Schools of Medicine
United States
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Liu, Nan; Yang, Yaxiong; Ge, Lin et al. (2017) Cooperative and acute inhibition by multiple C-terminal motifs of L-type Ca2+ channels. Elife 6:
Yang, Tingting; Hendrickson, Wayne A; Colecraft, Henry M (2014) Preassociated apocalmodulin mediates Ca2+-dependent sensitization of activation and inactivation of TMEM16A/16B Ca2+-gated Cl- channels. Proc Natl Acad Sci U S A 111:18213-8
Shaw, Robin M; Colecraft, Henry M (2013) L-type calcium channel targeting and local signalling in cardiac myocytes. Cardiovasc Res 98:177-86
Subramanyam, Prakash; Chang, Donald D; Fang, Kun et al. (2013) Manipulating L-type calcium channels in cardiomyocytes using split-intein protein transsplicing. Proc Natl Acad Sci U S A 110:15461-6
Yang, Tingting; He, Lin-Ling; Chen, Ming et al. (2013) Bio-inspired voltage-dependent calcium channel blockers. Nat Commun 4:2540
Yang, Tingting; Colecraft, Henry M (2013) Regulation of voltage-dependent calcium channels by RGK proteins. Biochim Biophys Acta 1828:1644-54
Yang, Tingting; Puckerin, Akil; Colecraft, Henry M (2012) Distinct RGK GTPases differentially use ýý1- and auxiliary ýý-binding-dependent mechanisms to inhibit CaV1.2/CaV2.2 channels. PLoS One 7:e37079
Fang, Kun; Colecraft, Henry M (2011) Mechanism of auxiliary ýý-subunit-mediated membrane targeting of L-type (Ca(V)1.2) channels. J Physiol 589:4437-55
Xu, Xianghua; Marx, Steven O; Colecraft, Henry M (2010) Molecular mechanisms, and selective pharmacological rescue, of Rem-inhibited CaV1.2 channels in heart. Circ Res 107:620-30
Yang, Tingting; Xu, Xianghua; Kernan, Timothy et al. (2010) Rem, a member of the RGK GTPases, inhibits recombinant CaV1.2 channels using multiple mechanisms that require distinct conformations of the GTPase. J Physiol 588:1665-81

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