Abstract
Alpha-thrombin, a key enzyme of the coagulation cascade, is also a potent mitogen for human vascular smooth muscle cells (HVSMC). Here it is demonstrated that the alpha-thrombin-mediated reduction of intracellular cAMP levels is sensitive to pertussis toxin (PTX). cAMP-elevating agents inhibited alpha-thrombin- and serum-induced mitogenesis, thus cAMP confers an anti-mitogenic signal on HVSMC. The PTX-dependent ADP-ribosylation of a 41 kDa Gi alpha protein(s) was significantly inhibited (up to 55%) by thrombin. HVSMC membranes had an intrinsic GTP'ase activity which was significantly increased (up to 36%) by thrombin. PTX treatment did not alter thrombin-induced elevation of GTP'ase activity. Thrombin stimulated phosphatidyl inositol (PI) turnover in a PTX-insensitive manner. This suggested that PTX insensitive G proteins such as Gq are also activated by thrombin. This study on HVSMC provides additional evidence for the involvement of different families of G proteins in thrombin signalling.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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1-Methyl-3-isobutylxanthine / pharmacology
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Adenosine Diphosphate Ribose / metabolism
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Alprostadil / pharmacology
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Cell Division / drug effects
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Cells, Cultured
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Colforsin / pharmacology
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Cyclic AMP / physiology*
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GTP Phosphohydrolases / metabolism
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GTP-Binding Proteins / antagonists & inhibitors
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GTP-Binding Proteins / physiology*
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Guanosine Triphosphate / metabolism
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Humans
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Muscle, Smooth, Vascular / drug effects*
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Muscle, Smooth, Vascular / physiology
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Pertussis Toxin*
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Phosphatidylinositols / physiology
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Poly(ADP-ribose) Polymerases / metabolism
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Saponins / pharmacology
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Signal Transduction / physiology*
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Thrombin / physiology*
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Virulence Factors, Bordetella / pharmacology*
Substances
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Phosphatidylinositols
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Saponins
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Virulence Factors, Bordetella
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Colforsin
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Adenosine Diphosphate Ribose
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Guanosine Triphosphate
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Cyclic AMP
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Poly(ADP-ribose) Polymerases
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Pertussis Toxin
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Thrombin
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GTP Phosphohydrolases
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GTP-Binding Proteins
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Alprostadil
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1-Methyl-3-isobutylxanthine