title: Cardiac myosin binding protein-C Ser302phosphorylation regulates cardiac β-adrenergic reserve.
abstract: Phosphorylation of cardiac myosin binding protein-C (MyBP-C) modulates cardiac contractile function; however, the specific roles of individual serines (Ser) within the M-domain that are targets for β-adrenergic signaling are not known. Recently, we demonstrated that significant accelerations in in vivo pressure development following β-agonist infusion can occur in transgenic (TG) mouse hearts expressing phospho-ablated Ser282(that is, TGS282A) but not in hearts expressing phospho-ablation of all three serines [that is, Ser273, Ser282, and Ser302(TG3SA)], suggesting an important modulatory role for other Ser residues. In this regard, there is evidence that Ser302phosphorylation may be a key contributor to the β-agonist-induced positive inotropic responses in the myocardium, but its precise functional role has not been established. Thus, to determine the in vivo and in vitro functional roles of Ser302phosphorylation, we generated TG mice expressing nonphosphorylatable Ser302(that is, TGS302A). Left ventricular pressure-volume measurements revealed that TGS302Amice displayed no accelerations in the rate of systolic pressure rise and an inability to maintain systolic pressure following dobutamine infusion similar to TG3SAmice, implicating Ser302phosphorylation as a critical regulator of enhanced systolic performance during β-adrenergic stress. Dynamic strain-induced cross-bridge (XB) measurements in skinned myocardium isolated from TGS302Ahearts showed that the molecular basis for impaired β-adrenergic-mediated enhancements in systolic function is due to the absence of protein kinase A-mediated accelerations in the rate of cooperative XB recruitment. These results demonstrate that Ser302phosphorylation regulates cardiac contractile reserve by enhancing contractile responses during β-adrenergic stress.
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Ranganath
authors.initials: R
authors.lastname: Mamidi
authors.affiliation: Center for Translational Medicine, Temple University, Philadelphia, PA 19140, USA.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Gresham
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Jiayang
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Julian E
authors.initials: JE
authors.lastname: Stelzer
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000187:drug effects* / Q000235:genetics; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D016277:Ventricular Function, Left / Q000187:drug effects* / Q000235:genetics; D000099163:Myosin Binding Protein C
chemical_list: D000318:Adrenergic beta-Agonists; D002352:Carrier Proteins; D000099163:Myosin Binding Protein C
keywords: cardiac contractile function; contractile reserve; cross-bridge kinetics; hemodynamic function