Molecular Mechanisms for the Activation of Voltage-Independent Ca 2+ Channels by Endothelin-1 in Chinese Hamster Ovary Cells Stably Expressing Human Endothelin A Receptors
2002; American Society for Pharmacology and Experimental Therapeutics; Volume: 62; Issue: 1 Linguagem: Inglês
10.1124/mol.62.1.75
ISSN1521-0111
AutoresYoshifumi Kawanabe, Yasuo Okamoto, Soichi Miwa, Nobuo Hashimoto, Tomoh Masaki,
Tópico(s)Receptor Mechanisms and Signaling
ResumoWe demonstrated recently that in Chinese hamster ovary cells stably expressing human recombinant endothelin A receptors (CHO-ET A R), endothelin-1 (ET-1) activates two types of Ca 2+ -permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and a store-operated Ca 2+ channel (SOCC), which can be distinguished by Ca 2+ channel blockers such as 1-{β-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenylethyl}-1 H -imidazole hydrochloride (SK&F 96365) and ( R , S )-(3,4-dihydro-6,7-dimethoxy-isochinolin-1-yl)-2-phenyl- N , N -di[2-(2,3,4-trimethoxyphenyl)ethyl]acetamid mesylate (LOE 908). We also reported that CHO-ET A R couples with G 12 in addition to G q and G s . The purpose of the present study was to identify the G proteins involved in the activation of these Ca 2+ channels by ET-1, using mutated ET A Rs with coupling to either G q or G s /G 12 (designated ET A RΔ385 and SerET A R, respectively) and a dominant-negative mutant of G 12 (G 12 G228A). ET A RΔ385 is truncated immediately downstream of Cys 385 in the C terminus as palmitoylation sites, whereas SerET A R is unpalmitoylated because of substitution of all the cysteine residues to serine (Cys 383 Cys 385–388 → Ser 383 Ser 385–388 ). In CHO-ET A RΔ385, stimulation with ET-1 activated only SOCC. In CHO-SerET A R or CHO-ET A R pretreated withU73122, an inhibitor of phospholipase C (PLC), ET-1 activated only NSCC-1. Dibutyryl cAMP alone did not activate any Ca 2+ channels in the resting and ET-1–stimulated CHO-SerET A R. Microinjection of G 12 G228A abolished the activation of NSCC-1 and NSCC-2 in CHO-ET A R and that of NSCC-1 in CHO-SerET A R. These results indicate that ET A R activates three types of Ca 2+ channels via different G protein-related pathways. NSCC-1 is activated via a G 12 -dependent pathway, NSCC-2 via G q /PLC- and G 12 -dependent pathways, and SOCC via a G q /PLC-dependent pathway.
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