title: Down-regulation of G-protein-mediated Ca2+ sensitization in smooth muscle.
abstract: 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.
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville 22906-0011, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Gong
authors.forename: H
authors.initials: H
authors.lastname: Fujihara
authors.forename: L A
authors.initials: LA
authors.lastname: Walker
authors.forename: A V
authors.initials: AV
authors.lastname: Somlyo
authors.forename: A P
authors.initials: AP
authors.lastname: Somlyo
mesh_terms: D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D001427:Bacterial Toxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D003902:Detergents; D015536:Down-Regulation; D016232:Endothelins / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D011169:Portal Vein / Q000187:drug effects / Q000378:metabolism; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011714:Pyrans; D011817:Rabbits; D012995:Solubility; D013141:Spiro Compounds; D013997:Time Factors; D020742:rhoA GTP-Binding Protein
chemical_list: D017607:Aluminum Compounds; D000935:Antifungal Agents; D001427:Bacterial Toxins; D003902:Detergents; D016232:Endothelins; D006460:Hemolysin Proteins; D018994:Myosin Light Chains; D011714:Pyrans; D013141:Spiro Compounds; C021091:staphylococcal alpha-toxin; C053079:tautomycin; D010656:Phenylephrine; C050992:tetrafluoroaluminate; D015240:Phorbol 12,13-Dibutyrate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011493:Protein Kinase C; D010744:Phosphoric Monoester Hydrolases; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D020742:rhoA GTP-Binding Protein; D005459:Fluorides; D002118:Calcium