Endothelin-1 decreases [Ca2+]i via Na+/Ca2+ exchanger in CHO cells stably expressing endothelin ETA receptor.
Endothelin ET(A) receptor couples to Gq/11 protein that transduces a variety of receptor signals to modulate diverse cellular responses including Ca2+ mobilization. Stimulation of endothelin ETA receptor with endothelin-1 is generally believed to induce an increase in intracellular Ca2+ concentration ([Ca2+]i) via Gq/11 protein. Here we provide the first convincing evidence that endothelin-1 elicited Gq/11 protein-dependent and -independent 'decrease' in [Ca2+]i via Na+/Ca2+ exchanger (NCX) in Chinese hamster ovary (CHO) cells stably expressing human endothelin ETA receptor. In the cells treated with 1 microM thapsigargin, an inhibitor of endoplasmic Ca2+ pump, that induces an increase in [Ca2+]i via capacitative Ca2+ entry, endothelin-1 induced a decrease in [Ca2+]i which was partially inhibited by YM-254890, a specific inhibitor of Gq/11, indicating that Gq/11-dependent and independent pathways are involved in the decrease. The endothelin-1-induced decrease in [Ca2+]i was markedly suppressed by 3',4'-dichlorobenzamil hydrochloride, a potent NCX inhibitor, and also by a replacement of extracellular Na+ with Li+, which was not transported by NCX, indicating a major role of NCX operating in the forward mode in the endothelin-1-induced decrease in [Ca2+]i. Molecular approach with RT-PCR demonstrated the expression of mRNA for NCX1, NCX2 and NCX3. These results suggest that stimulation of endothelin ETA receptor with endothelin-1 activates the forward mode NCX through Gq/11-dependent and -independent mechanisms: the NCX exports Ca2+ out of the cell depending on Na+ gradient across the cell membrane, resulting in the decrease in [Ca2+]i.
Horinouchi
Takahiro
T
Department of Cellular Pharmacology, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
Nishimoto
Arata
A
Nishiya
Tadashi
T
Lu
Lingyun
L
Kajita
Emi
E
Miwa
Soichi
S
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D006224:Cricetinae; D003412:Cricetulus; D019332:Endothelin-1 / Q000494:pharmacology*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000037:antagonists & inhibitors; D010456:Peptides, Cyclic / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D044022:Receptor, Endothelin A / Q000235:genetics / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
D019332:Endothelin-1; D010456:Peptides, Cyclic; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D019831:Sodium-Calcium Exchanger; C475455:YM-254890; C041470:3',4'-dichlorobenzamil; D019284:Thapsigargin; D000584:Amiloride; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D000252:Calcium-Transporting ATPases; D002118:Calcium