Effects of calcium channel antagonists on the phosphorylation of major protein kinase C substrates in the rat hippocampus.
K(+)-induced depolarization of rat hippocampal slices resulted in significant increases in the phosphorylation state of myristoylated, alanine-rich C kinase substrate (MARCKS; also known as 87K, pp80) and neuromodulin [also known as growth associated protein 43 (GAP43), B50, F1] as determined by back-phosphorylation using protein kinase C. The effect of organic and inorganic Ca2+ antagonists on the phosphorylation of these major protein kinase C substrates in the rat hippocampus was studied to determine whether Ca2+ influx through L- or N-type voltage-sensitive Ca2+ channels was required for the phosphorylation changes observed. The depolarization-induced changes appeared to be dependent on extracellular Ca2+, based on evidence indicating that the chelation of extracellular Ca2+ with ethylene glycol-bis (beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) inhibited these changes. In addition, pretreatment of the slices with 500 microM Cd2+, but not 300 nM nimodipine, 10 microM omega-conotoxin GVIA or 10 microM MK-801, blocked the K(+)-induced change in phosphorylation. These results suggest that K(+)-induced changes in the phosphorylation of MARCKS and neuromodulin are mediated by Ca(2+)-dependent mechanisms other than, or in addition to, those sensitive to the organic Ca2+ channel antagonists employed.
Hoffman
F J
FJ
Miles Research Center, Miles Inc., West Haven, CT 06516.
Janis
R A
RA
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D019922:GAP-43 Protein; D006624:Hippocampus / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity
D002121:Calcium Channel Blockers; D019922:GAP-43 Protein; D047908:Intracellular Signaling Peptides and Proteins; C000619712:Marcks protein, rat; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011506:Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D011493:Protein Kinase C