Biochemical and Biophysical Research Communications, Vol.433, No.2, 188-193, 2013
Alpha(1)-adrenenoceptor stimulation inhibits cardiac excitation-contraction coupling through tyrosine phosphorylation of beta(1)-adrenoceptor
Adrenoceptor stimulation is a key determinant of cardiac excitation-contraction coupling mainly through the activation of serine/threonine kinases. However, little is known about the role of protein tyrosine kinases (PTKs) activated by adrenergic signaling on cardiac excitation-contraction coupling. A cytoplasmic tyrosine residue in beta(1)-adrenoceptor is estimated to regulate G(s)-protein binding affinity from crystal structure studies, but the signaling pathway leading to the phosphorylation of these residues is unknown. Here we show alpha(1)-adrenergic signaling inhibits beta-adrenergically activated Ca2+ current, Ca2+ transients and contractile force through phosphorylation of tyrosine residues in beta(1)-adrenoceptor by PTK. Our results indicate that inhibition of beta-adrenoceptor-mediated Ca2+ elevation by alpha(1)-adrenoceptor-PTK signaling serves as an important regulatory feedback mechanism when the catecholamine level increases to protect cardiomyocytes from cytosolic Ca2+ overload. (C) 2013 Elsevier Inc. All rights reserved.