cMyBP-C phosphorylation modulates the time-dependent slowing of unloaded shortening in murine skinned myocardium.

Autor:	Giles J; Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, and the University of Wisconsin Cardiovascular Research Center, Madison, WI., Fitzsimons DP; Department of Animal, Veterinary and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID., Patel JR; Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, and the University of Wisconsin Cardiovascular Research Center, Madison, WI., Knudtsen C; Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, and the University of Wisconsin Cardiovascular Research Center, Madison, WI., Neuville J; Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, and the University of Wisconsin Cardiovascular Research Center, Madison, WI., Moss RL; Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, and the University of Wisconsin Cardiovascular Research Center, Madison, WI.
Jazyk:	angličtina
Zdroj:	The Journal of general physiology [J Gen Physiol] 2021 Mar 01; Vol. 153 (3).
DOI:	10.1085/jgp.202012782
Abstrakt:	In myocardium, phosphorylation of cardiac myosin-binding protein-C (cMyBP-C) is thought to modulate the cooperative activation of the thin filament by binding to myosin and/or actin, thereby regulating the probability of cross-bridge binding to actin. At low levels of Ca2+ activation, unloaded shortening velocity (Vo) in permeabilized cardiac muscle is comprised of an initial high-velocity phase and a subsequent low-velocity phase. The velocities in these phases scale with the level of activation, culminating in a single high-velocity phase (Vmax) at saturating Ca2+. To test the idea that cMyBP-C phosphorylation contributes to the activation dependence of Vo, we measured Vo before and following treatment with protein kinase A (PKA) in skinned trabecula isolated from mice expressing either wild-type cMyBP-C (tWT), nonphosphorylatable cMyBP-C (t3SA), or phosphomimetic cMyBP-C (t3SD). During maximal Ca2+ activation, Vmax was monophasic and not significantly different between the three groups. Although biphasic shortening was observed in all three groups at half-maximal activation under control conditions, the high- and low-velocity phases were faster in the t3SD myocardium compared with values obtained in either tWT or t3SA myocardium. Treatment with PKA significantly accelerated both the high- and low-velocity phases in tWT myocardium but had no effect on Vo in either the t3SD or t3SA myocardium. These results can be explained in terms of a model in which the level of cMyBP-C phosphorylation modulates the extent and rate of cooperative spread of myosin binding to actin. (© 2021 Giles et al.)
Databáze:	MEDLINE
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