Cardiac CaV1.2 channels require β subunits for β-adrenergic–mediated modulation but not trafficking
Lin Yang, … , Henry M. Colecraft, Steven O. Marx
Lin Yang, … , Henry M. Colecraft, Steven O. Marx
Published February 1, 2019; First published November 13, 2018
Citation Information: J Clin Invest. 2019;129(2):647-658. https://doi.org/10.1172/JCI123878.
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Categories: Research Article Cardiology Muscle biology

Cardiac CaV1.2 channels require β subunits for β-adrenergic–mediated modulation but not trafficking

Abstract

Ca2+ channel β-subunit interactions with pore-forming α-subunits are long-thought to be obligatory for channel trafficking to the cell surface and for tuning of basal biophysical properties in many tissues. Unexpectedly, we demonstrate that transgenic expression of mutant α1C subunits lacking capacity to bind CaVβ can traffic to the sarcolemma in adult cardiomyocytes in vivo and sustain normal excitation-contraction coupling. However, these β-less Ca2+ channels cannot be stimulated by β-adrenergic pathway agonists, and thus adrenergic augmentation of contractility is markedly impaired in isolated cardiomyocytes and in hearts. Similarly, viral-mediated expression of a β-subunit–sequestering peptide sharply curtailed β-adrenergic stimulation of WT Ca2+ channels, identifying an approach to specifically modulate β-adrenergic regulation of cardiac contractility. Our data demonstrate that β subunits are required for β-adrenergic regulation of CaV1.2 channels and positive inotropy in the heart, but are dispensable for CaV1.2 trafficking to the adult cardiomyocyte cell surface, and for basal function and excitation-contraction coupling.

Authors

Lin Yang, Alexander Katchman, Jared Kushner, Alexander Kushnir, Sergey I. Zakharov, Bi-xing Chen, Zunaira Shuja, Prakash Subramanyam, Guoxia Liu, Arianne Papa, Daniel Roybal, Geoffrey S. Pitt, Henry M. Colecraft, Steven O. Marx

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Figure 5

Attenuated β-adrenergic–stimulated inotropy in AID-mutant α1C transgenic mice.

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Attenuated β-adrenergic–stimulated inotropy in AID-mutant α1C transgenic...
(A and B) Cells with robust shortening induced by 1 Hz electrical stimulation in the presence of 300 nM nisoldipine were used. Isoproterenol (200 nM) was superfused with 300 nM nisoldipine. (C) Plot of isoproterenol-induced fold change in sarcomere length compared with before isoproterenol. Mean ± SEM; n = 17 for pWT α1C cardiomyocytes and n = 19 cardiomyocytes for AID-mutant α1C. ***P < 0.001 by t test. (D) Plot of isoproterenol-induced percentage of change in τrelaxation of sarcomere length compared with before isoproterenol. Mean ± SEM; n = 23 cardiomyocytes from 3 mice and n = 32 cardiomyocytes from 3 mice. P = 0.16 by t test. (E and F) Representative traces depicted effect of perfusion of 300 nM nisoldipine on left ventricular contraction in isolated Langendorff-perfused hearts resected from NTG mice and pWT α1C transgenic mice. (G and H) Representative traces of nisoldipine-resistant LV pressure before and during isoproterenol infusion, in hearts resected from pWT α1C and AID-mutant α1C transgenic mice. (I) Quantitative summary of dP/dtmax before and during isoproterenol infusion. n = 7 pWT α1C transgenic mice; n = 11 AID-mutant α1C transgenic mice. *P < 0.05 by t test.