Molecular mechanisms for the activation of voltage-independent Ca2+ channels by endothelin-1 in chinese hamster ovary cells stably expressing human endothelin(A) receptors.
We 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 Ca2+-permeable nonselective cation channels (designated NSCC-1 and NSCC-2) and a store-operated Ca2+ channel (SOCC), which can be distinguished by Ca(2+) channel blockers such as 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenylethyl]-1H-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 G12 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 Ca2+ channels by ET-1, using mutated ET(A)Rs with coupling to either G(q) or G(s)/G12 (designated ET(A)RDelta385 and SerET(A)R, respectively) and a dominant-negative mutant of G12 (G12G228A). ET(A)RDelta385 is truncated immediately downstream of Cys385 in the C terminus as palmitoylation sites, whereas SerET(A)R is unpalmitoylated because of substitution of all the cysteine residues to serine (Cys383Cys385-388 --> Ser383Ser385-388). In CHO-ET(A)RDelta385, stimulation with ET-1 activated only SOCC. In CHO-SerET(A)R or CHO-ET(A)R pretreated with U73122, an inhibitor of phospholipase C (PLC), ET-1 activated only NSCC-1. Dibutyryl cAMP alone did not activate any Ca2+ channels in the resting and ET-1-stimulated CHO-SerET(A)R. Microinjection of G12G228A 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 Ca2+ channels via different G protein-related pathways. NSCC-1 is activated via a G12-dependent pathway, NSCC-2 via G(q)/PLC- and G12-dependent pathways, and SOCC via a G(q)/PLC-dependent pathway.
Kawanabe
Yoshifumi
Y
Department of Neurosurgery, Kyoto University Faculty of Medicine, Kyoto, Japan. ykawanabe@rics.bwh.harvard.edu
Okamoto
Yasuo
Y
Miwa
Soichi
S
Hashimoto
Nobuo
N
Masaki
Tomoh
T
D019943:Amino Acid Substitution; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D006224:Cricetinae; D019332:Endothelin-1 / Q000378:metabolism; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D017353:Gene Deletion; D020962:Heterotrimeric GTP-Binding Proteins / Q000494:pharmacology; D006801:Humans; D009154:Mutation; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000096:biosynthesis* / Q000235:genetics; D014162:Transfection; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D015220:Calcium Channels; D019332:Endothelin-1; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D003994:Bucladesine; D010738:Type C Phospholipases; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020962:Heterotrimeric GTP-Binding Proteins; D002118:Calcium