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.
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1 March 2021
Article|
February 10 2021
cMyBP-C phosphorylation modulates the time-dependent slowing of unloaded shortening in murine skinned myocardium
Jasmine Giles
,
Jasmine Giles
1
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
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Daniel P. Fitzsimons
,
Daniel P. Fitzsimons
2
Department of Animal, Veterinary and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID
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Jitandrakumar R. Patel
,
Jitandrakumar R. Patel
1
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
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Chloe Knudtsen
,
Chloe Knudtsen
1
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
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Zander Neuville
,
Zander Neuville
1
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
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Richard L. Moss
1
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
Correspondence to Richard L. Moss: rlmoss@wisc.edu
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Jasmine Giles
1
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
Daniel P. Fitzsimons
2
Department of Animal, Veterinary and Food Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID
Jitandrakumar R. Patel
1
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
Chloe Knudtsen
1
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
Zander Neuville
1
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
Richard L. Moss
1
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
Correspondence to Richard L. Moss: rlmoss@wisc.edu
This work is part of a special collection on myofilament function and disease.
Received:
September 30 2020
Accepted:
January 14 2021
Online Issn: 1540-7748
Print Issn: 0022-1295
Funding:
National Institutes of Health
(RO1 HL139883)
© 2021 Giles et al.
2021
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).
J Gen Physiol (2021) 153 (3): e202012782.
Article history
Received:
September 30 2020
Accepted:
January 14 2021
Citation
Jasmine Giles, Daniel P. Fitzsimons, Jitandrakumar R. Patel, Chloe Knudtsen, Zander Neuville, Richard L. Moss; cMyBP-C phosphorylation modulates the time-dependent slowing of unloaded shortening in murine skinned myocardium. J Gen Physiol 1 March 2021; 153 (3): e202012782. doi: https://doi.org/10.1085/jgp.202012782
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