Endothelin-1 stimulation of proteoglycan synthesis in vascular smooth muscle is mediated by endothelin receptor transactivation of the transforming growth factor-[beta] type I receptor.
We utilized human vascular smooth muscle cells to address the question if a G-protein-coupled receptor, the endothelin (ET) receptor, could transactivate a serine/threonine kinase receptor, specifically the transforming growth factor (TGF)-[beta] receptor, T[beta]RI. Functionality of the interaction was addressed by studying endothelin-1-stimulated proteoglycan synthesis. Signaling molecules were assessed by Western blotting and proteoglycan synthesis by [35S]sulfate and 35S-met/cys incorporation and molecular size by SDS-PAGE. Endothelin-1 treatment led to a time- and concentration-dependent increase in cytosolic phosphoSmad2C, which was inhibited by the mixed endothelin receptor antagonist bosentan and the T[beta]RI antagonist SB431542. Endothelin-1 treatment led to a time-dependent increase in nuclear phosphoSmad2C. Endothelin-1-stimulated proteoglycan synthesis was partially inhibited (40%) by SB431542 and completely blocked by bosentan. The effect of endothelin-1 to stimulate an increase in glycosaminoglycan size on biglycan was also blocked in a concentration-dependent manner by SB431542. These data extend the current paradigm of G-protein coupled receptor signaling to include the transactivation of the serine kinase receptor for TGF-[beta] (T[beta]RI). This response should be considered in the context of response to endothelin-1, and the options for therapeutically targeting endothelin-1 are accordingly broadened to include downstream signaling otherwise associated with TGF-[beta] receptor activation.
Little
Peter J
PJ
Diabetes and Cell Biology Laboratory, BakerIDI Heart and Diabetes Institute, Melbourne, Victoria, Australia. peter.little@bakeridi.edu.au
Burch
Micah L
ML
Getachew
Robel
R
Al-aryahi
Sefaa
S
Osman
Narin
N
D001549:Benzamides / Q000494:pharmacology; D000077300:Bosentan; D002478:Cells, Cultured; D004149:Dioxoles / Q000494:pharmacology; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism* / Q000494:pharmacology; D006025:Glycosaminoglycans / Q000096:biosynthesis; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011509:Proteoglycans / Q000096:biosynthesis*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D017466:Receptors, Endothelin / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D015533:Transcriptional Activation / Q000502:physiology*
C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; D001549:Benzamides; D004149:Dioxoles; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D006025:Glycosaminoglycans; D011509:Proteoglycans; D017466:Receptors, Endothelin; D018125:Receptors, Transforming Growth Factor beta; D013449:Sulfonamides; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077300:Bosentan