title: On the regulation of the expressed L-type calcium channel by cAMP-dependent phosphorylation.
abstract: The Ca2+ channel subunits alpha 1C-a and alpha 1C-b were stably expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293 cells. The peak Ba2+ current (IBa) of these cells was not affected significantly by internal dialysis with 0.1 mM cAMP-dependent protein kinase inhibitor peptide (mPKI), 25 microM cAMP-dependent protein kinase catalytic subunit (PKA), or a combination of 25 microM PKA and 1 microM okadaic acid. The activity of the alpha 1C-b channel subunit expressed stably in HEK 293 cells was depressed by 1 microM H 89 and was not increased by superfusion with 5 microM forskolin plus 20 microM isobutyl-methylxanthine (IBMX). The alpha 1C-a.beta 2.alpha 2/delta complex was transiently expressed in HEK 293 cells; it was inhibited by internal dialysis of the cells with 1 microM H 89, but was not affected by internal dialysis with mPKI, PKA or microcystin. Internal dialysis of cells expressing the alpha 1C-a.beta 2.alpha 2/delta channel with 10 microM PKA did not induce facilitation after a 150-ms prepulse to +50 mV. The Ca2+ current (ICa) of cardiac myocytes increased threefold during internal dialysis with 5 microM PKA or 25 microM microcystin and during external superfusion with 0.1 microM isoproterenol or 5 microM forskolin plus 50 microM IBMX. These results indicate that the L-type Ca2+ channel expressed is not modulated by cAMP-dependent phosphorylation to the same extent as in native cardiac myocytes.
mesh_terms: D000818:Animals; D001464:Barium / Q000378:metabolism; D016466:CHO Cells; D015220:Calcium Channels / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology; D002417:Cattle; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004594:Electrophysiology; D005260:Female; D006801:Humans; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D012326:RNA Splicing
chemical_list: D015220:Calcium Channels; D001464:Barium; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases