Endothelin ETB receptors couple to two distinct signaling pathways in porcine kidney epithelial LLC-PK1 cells.
We characterized the endothelin (ET) receptor subtypes responsible for signal transduction in cultured porcine kidney epithelial LLC-PK1 cells. Both ET-1 (IC50, 43 pM) and ET-3 (IC50, 46 pM) inhibited the binding of [125I]ET-1 to LLC-PK1 cells to a similar extent. The binding affinity of LLC-PK1 cells was about 10,000 times higher for the ETB antagonist BQ-788 [N-cis-2,6-dimethyl-piperidinocarbonyl-L-tau-metylleucyl-D-+ ++Nin- methoxycarbonyltryptophanyl-D-norleucine] (IC50, 1.3 nM) than for the ETA antagonist BQ-123 [cyclo-(D-Trp-D-Asp-Pro-D-Val-Leu)] (IC50, 14 microM). ET-1 enhanced cyclic GMP (cGMP) production, but reduced vasopressin- and forskolin-stimulated cyclic AMP (cAMP) production. Both effects of ET-1 were antagonized by BQ-788, but not by BQ-123. The cAMP decrease, but not the cGMP increase, in response to ET-1 was inhibited by pertussis toxin, suggesting that the former response is mediated by pertussis toxin-sensitive Gi, whereas the latter is mediated by a pertussis toxin-insensitive G-protein. Therefore, the ETB receptors in LLC-PK1 cells couple to the two types of signal transduction cascades to reduce cAMP production and stimulate cGMP production via distinct G-proteins. ET-1 and probably also ET-3 may play a role in the regulation of renal epithelial transport by decreasing cAMP and increasing cGMP.
Ozaki
S
S
Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., Japan.
Ihara
M
M
Saeki
T
T
Fukami
T
T
Ishikawa
K
K
Yano
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors; D005576:Colforsin / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000096:biosynthesis; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006020:Glycopeptides / Q000494:pharmacology; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D018374:LLC-PK1 Cells; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011485:Protein Binding; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000378:metabolism*; D015398:Signal Transduction; D013552:Swine
D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D006020:Glycopeptides; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D001127:Arginine Vasopressin; D005576:Colforsin; C086539:BQ 788; D000242:Cyclic AMP; D006152:Cyclic GMP; C072247:cyclo(Trp-Asp-Pro-Val-Leu); C008890:phosphoramidon