Phosphorylation of the L-type calcium channel beta subunit is involved in beta-adrenergic signal transduction in canine myocardium.
Cyclic AMP-mediated phosphorylation of calcium channel subunits was studied in vitro and in vivo in preparations from dog heart. Calcium channels in native cardiac membranes were phosphorylated by cAMP-dependent protein kinase (PKA) solubilized with digitonin and subsequently immunoprecipitated using a polyclonal antibody generated against the deduced carboxy-terminal sequence of the cardiac beta subunit. A 62 kDa protein was identified as the major PKA-substrate in the immunoprecipitates. In the intact myocardium, this putative beta subunit was found to be phosphorylated in response to cAMP elevating agents. In contrast, no phosphorylation of a protein with an electrophoretic mobility similar to the alpha 1 subunit was detected, although 1,4-dihydropyridine receptor sites were recovered in the immunoprecipitates. Thus, we suggest that PKA-mediated phosphorylation of the beta subunit is the major mechanism for beta-adrenergic regulation of cardiac L-type calcium channel activity.
Haase
H
H
Max Delbrück Centre for Molecular Medicine, Molecular Cardiology, Berlin-Buch, Germany.
Karczewski
P
P
Beckert
R
R
Krause
E G
EG
D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004285:Dogs; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D015220:Calcium Channels; D011943:Receptors, Adrenergic, beta; D017868:Cyclic AMP-Dependent Protein Kinases