Abbreviations used : cAMP, cyclic AMP ; cGMP, cyclic GMP ; DMEM, Dulbecco's modified Eagle's medium ; H7, 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine ; H89, N[2-[(p-bromocinnamyl)amino]-ethyl -5-isoquinolinesulfonamide ; I-V, current-voltage ; L-channel, L-type Ca2+ channel ; PP1, phosphoprotein phosphatase-1 ; PP2A, phosphoprotein phosphatase-2A.
Regulation of the L-Type Ca2+ Channel Current in Rat Pinealocytes
Role of Basal Phosphorylation
Article first published online: 18 JAN 2002
Journal of Neurochemistry
Volume 72, Issue 1, pages 73–80, January 1999
How to Cite
Chik, C. L., Li, B., Karpinski, E. and Ho, A. K. (1999), Regulation of the L-Type Ca2+ Channel Current in Rat Pinealocytes. Journal of Neurochemistry, 72: 73–80. doi: 10.1046/j.1471-4159.1999.0720073.x
- Issue published online: 18 JAN 2002
- Article first published online: 18 JAN 2002
- Calyculin A;
- Protein kinase C;
- Ca2+ channels;
- Pineal gland
Abstract : In the present study, the role of phosphoprotein phosphatase in the regulation of L-type Ca2+ channel currents in rat pinealocytes was investigated using the whole-cell version of the patch-clamp technique. The effects of three phosphatase inhibitors, calyculin A, tautomycin, and okadaic acid, were compared. Although all three inhibitors were effective in inhibiting the L-type Ca2+ channel current, calyculin A was more potent than either tautomycin or okadaic acid, suggesting the involvement of phosphoprotein phosphatase-1. To determine the kinase involved in the regulation of these channels, cells were pretreated with H7 (a nonspecific kinase inhibitor), H89 (a specific inhibitor of cyclic AMP-dependent kinase), KT5823 (a specific inhibitor of cyclic GMP-dependent kinase), or calphostin C (a specific inhibitor of protein kinase C). Pretreatment with either H7 or calphostin C decreased the inhibitory effect of calyculin A on the L-type Ca2+ channel current. In contrast, pretreatment with H89 or KT5823 had no effect on the inhibition caused by calyculin A. Based on these observations, we conclude that basal phosphatase activity, probably phosphoprotein phosphatase-1, plays an important role in the regulation of L-type Ca2+ channel currents in rat pinealocytes by counteracting protein kinase C-mediated phosphorylation.