tautomycin and tetrafluoroaluminate

Prolonged treatment with guanosine 5'-[gamma-thio]triphosphate (GTP gamma S; 5-16 h, 50 microM) of smooth muscle permeabilized with Staphylococcus aureus alpha-toxin down-regulated (abolished) the acute Ca2+ sensitization of force by GTP gamma S, AIF-4, phenylephrine, and endothelin, but not the response to phorbol dibutyrate or a phosphatase inhibitor, tautomycin. Down-regulation also abolished the GTP gamma S-induced increase in myosin light chain phosphorylation at constant [Ca2+] and was associated with extensive translocation of p21rhoA to the particulate fraction, prevented its immunoprecipitation, and inhibited its ADP ribosylation without affecting the immunodetectable content of G-proteins (p21rhoA, p21ras, G alpha q/11, G alpha i3, and G beta) or protein kinase C (types alpha, beta 1, beta 2, delta, epsilon, eta, theta, and zeta). We conclude that the loss of GTP gamma S- and agonist-induced Ca2+ sensitization through prolonged treatment with GTP gamma S is not due to a decrease in the total content of either trimeric (G alpha q/11, G alpha i3, and G beta) or monomeric (p21rhoA and p21ras) G-protein or protein kinase C but may be related to a structural change of p21rhoA and/or to down-regulation of its (yet to be identified) effector.

Topics: Aluminum Compounds; Animals; Antifungal Agents; Bacterial Toxins; Calcium; Detergents; Down-Regulation; Endothelins; Fluorides; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Hemolysin Proteins; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Myosin Light Chains; Phenylephrine; Phorbol 12,13-Dibutyrate; Phosphoric Monoester Hydrolases; Phosphorylation; Portal Vein; Precipitin Tests; Protein Kinase C; Proto-Oncogene Proteins p21(ras); Pyrans; Rabbits; rhoA GTP-Binding Protein; Solubility; Spiro Compounds; Time Factors