On the regulation of the expressed L-type calcium channel by cAMP-dependent phosphorylation |
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Authors: | Xiangang Zong Jürgen Schreieck Gerhard Mehrke Andera Welling Angela Schuster Eva Bosse Veit Flockerzi Franz Hofmann |
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Affiliation: | (1) Institut für Pharmakologie und Toxikologie der TUM, Biedersteiner Strasse 29, D-80802 Munich, Germany;(2) Present address: Pharmakologisches Institut, Abteilung Molekulare Pharmakologie, Medizinische Fakultät, Universität Heidelberg, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany |
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Abstract: | The Ca2+ channel subunits 1C-a and 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 M cAMP-dependent protein kinase catalytic subunit (PKA), or a combination of 25 M PKA and 1 M okadaic acid. The activity of the 1C-b channel subunit expressed stably in HEK 293 cells was depressed by 1 M H 89 and was not increased by superfusion with 5 M forskolin plus 20 M isobutylmethylxanthine (IBMX). The 1C-a·2·2/ complex was transiently expressed in HEK 293 cells; it was inhibited by internal dialysis of the cells with 1 M H 89, but was not affected by internal dialysis with mPKI, PKA or microcystin. Internal dialysis of cells expressing the 1C-a·2·2/ channel with 10 M 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 M PKA or 25 M microcystin and during external superfusion with 0.1 M isoproterenol or 5 M forskolin plus 50 M 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. |
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Keywords: | L-Type calcium channels cAMP-dependent regulation of calcium channels Transient and stable expression of calcium channels CHO cells HEK 293 cells |
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