Cardiac myosin binding protein-C phosphorylation in a {beta}-myosin heavy chain background.
BACKGROUND
Cardiac myosin binding protein-C (cMyBP-C) phosphorylation modulates cardiac contractility. When expressed in cMyBP-C-null (cMyBP-C((t/t))) hearts, a cMyBP-C phosphomimetic (cMyBP-C(AllP+)) rescued cardiac dysfunction and protected the hearts from ischemia/reperfusion injury. However, cMyBP-C function may be dependent on the myosin isoform type. Because these replacements were performed in the mouse heart, which contains predominantly alpha-myosin heavy chain (alpha-MyHC), the applicability of the data to humans, whose cardiomyocytes contain predominantly beta-MyHC, is unclear. We determined the effect(s) of cMyBP-C phosphorylation in a beta-MyHC transgenic mouse heart in which >80% of the alpha-MyHC was replaced by beta-MyHC, which is the predominant myosin isoform in human cardiac muscle.


RESULTS
To determine the effects of cMyBP-C phosphorylation in a beta-MyHC background, transgenic mice expressing normal cMyBP-C (cMyBP-C(WT)), nonphosphorylatable cMyBP-C (cMyBP-C(AllP)(-)), or cMyBP-C(AllP+) were bred into the beta-MyHC background (beta). These mice were then crossed into the cMyBP-C((t/t)) background to ensure the absence of endogenous cMyBP-C. cMyBP-C((t/t)/beta) and cMyBP-C(AllP)(-)(:(t/t)/beta) mice died prematurely because of heart failure, confirming that cMyBP-C phosphorylation is essential in the beta-MyHC background. cMyBP-C(AllP+:(t/t)/beta) and cMyBP-C(WT:(t/t)/beta) hearts showed no morbidity and mortality, and cMyBP-C(AllP+:(t/t)/beta) hearts were significantly cardioprotected from ischemia/reperfusion injury.


CONCLUSIONS
cMyBP-C phosphorylation is necessary for basal myocardial function in the beta-MyHC background and can preserve function after ischemia/reperfusion injury. Our studies justify exploration of cMyBP-C phosphorylation as a therapeutic target in the human heart.
Sadayappan
Sakthivel
S
Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Ohio, USA.
Gulick
James
J
Klevitsky
Raisa
R
Lorenz
John N
JN
Sargent
Michelle
M
Molkentin
Jeffery D
JD
Robbins
Jeffrey
J
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003326:Coronary Circulation / Q000502:physiology; D003432:Cross-Linking Reagents / Q000378:metabolism; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology; D006334:Heart Function Tests; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000502:physiology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000502:physiology; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D017434:Protein Structure, Tertiary; D024723:Ventricular Myosins / Q000235:genetics* / Q000378:metabolism*; D000099163:Myosin Binding Protein C
D017301:Ca(2+) Mg(2+)-ATPase; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D018995:Myosin Heavy Chains; D024723:Ventricular Myosins; D000099163:Myosin Binding Protein C