Cyclic AMP-dependent protein kinase phosphorylates residues in the C-terminal domain of the cardiac L-type calcium channel alpha1 subunit.
The molecular basis of the regulation of cardiac L-type calcium channel activity by cAMP-dependent protein kinase (cA-PK) remains unclear. Direct cA-PK-dependent phosphorylation of the bovine ventricular alpha1 subunit in vitro has been demonstrated in microsomal membranes, detergent extracts and partially purified (+)-[3H]PN 200-110 receptor preparations. Two 32P-labeled phosphopeptides, derived from cyanogen bromide cleavage, of 4.7 and 9.5 kDa were immunoprecipitated specifically by site-directed antibodies against the rabbit cardiac alpha1 subunit amino acid sequences 1602-1616 and 1681-1694, respectively, consistent with phosphorylation at the cA-PK consensus sites at Ser(1627) and Ser(1700). No phosphopeptide products consistent with phosphorylation at three other C-terminal cA-PK consensus phosphorylation sites (Ser(1575), Ser(1848) and Ser(1928)) were identified using similar procedures suggesting that these sites are poor substrates for this kinase. Ser(1627) and Ser(1700) may represent sites of cA-PK phosphorylation involved in the physiological regulation of cardiac L-type calcium channel function.
Leach
R N
RN
Department of Medicine and Therapeutics, University of Leicester, Clinical Sciences Building, Leicester Royal Infirmary, UK.
Brickley
K
K
Norman
R I
RI
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D003488:Cyanogen Bromide; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006352:Heart Ventricles / Q000648:ultrastructure; D007163:Immunosorbent Techniques; D017275:Isradipine / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011817:Rabbits
D015220:Calcium Channels; D010446:Peptide Fragments; D010768:Phosphoserine; D017868:Cyclic AMP-Dependent Protein Kinases; D003488:Cyanogen Bromide; D017275:Isradipine