Multifunctional Ca2+/Calmodulin-Dependent Protein Kinase Mediates Ca2+-Induced Enhancement of the L-type Ca2+ Current in Rabbit Ventricular Myocytes

• Published in: Circulation research Vol. 75; no. 5; pp. 854 - 861
• Main Authors: Anderson, Mark E, Braun, Andrew P, Schulman, Howard, Premack, Brett A
• Format: Journal Article
• Language: English
• Published: Hagerstown American Heart Association, Inc 01.11.1994; Lippincott Williams & Wilkins Ovid Technologies
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.75.5.854

The intracellular mechanism underlying the Ca-induced enhancement of the L-type Ca current (1Ca) was examined in adult rabbit cardiac ventricular myocytes by using patch-clamp methodology. Internal Ca was elevated by flash photolysis of the Ca chelator Nitr 5, and intracellular Ca levels were simultaneously monitored by Fluo 3 fluorescence. Flash photolysis of Nitr 5 produced a rapid (<l-second) elevation of internal Ca, which led to enhancement (39% to 51% above control) of the peak inward Ca current after a delay of 20 to 120 seconds. Internal dialysis of myocytes with synthetic inhibitory peptides derived from the pseudosubstrate (peptide 273-302) and calmodulin binding (peptide 291-317) regions within the regulatory domain of multifunctional Ca/calmodulin-dependent protein kinase (CaM kinase) blocked enhancement of ICa produced by elevation of internal Ca but not that produced by β-adrenergic stimulation. These inhibitory peptides also had no effect on the elevation of internal Ca produced by flash photolysis of Nitr 5. A pseudosubstrate inhibitory peptide derived from protein kinase C had no significant effect on Ca-dependent enhancement of ICa. We conclude that CaM kinase mediates the Ca -induced enhancement of ICa in mammalian cardiac myocytes by a mechanism likely involving direct phosphorylation of the L-type Ca channel complex or an associated regulatory protein.