Involvement of botulinum C3-sensitive GTP-binding proteins in alpha 1-adrenoceptor subtypes mediating Ca(2+)-sensitization.
The mechanisms of alpha 1-adrenoceptor agonist-mediated sensitization of the contractile apparatus of smooth muscle to Ca2+ were studied in beta-escin-permeabilized thoracic arterial smooth muscle of rabbit. Addition of norepinephrine (10 microM) plus guanosine 5'-triphosphate (GTP, 50 microM) significantly enhanced Ca2+ sensitivity as compared with the addition of 0.3 microM Ca2+ alone (pCa6.5). In beta-escin-skinned smooth muscle of chloroethylclonidine-treated tissues, the enhancement of Ca(2+)-contraction produced by norepinephrine or clonidine was completely inhibited by guanosine 5'-O-(beta-thiodiphosphate) (GDP beta-S, 1 mM). In addition, Clostridium botulinum C3, which inactivates low molecular weight GTP-binding protein families, abolished norepinephrine- or clonidine-induced Ca(2+)-sensitization, but did not affect clonidine-induced translocation of protein kinase C to the membrane. The norepinephrine-enhanced Ca2+ sensitivity was partially reversed by a pretreatment with a selective myosin light chain kinase inhibitor (8R*, 9S*, 11S*)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-14-n- propoxy-2,3,9,10-tetrahydro-8,11-epoxy,1H,8H,11H-2,7b,11a- triazadibenzo[a,g]cycloocta[cde]trinden-1-one (KT5926, 500 nM), but those of clonidine and in the chloroethylclonidine-treated tissues norepinephrine were not. These results suggest that Ca(2+)-sensitization produced by the activation of the alpha 1-adrenoceptor subtypes is linked via a low molecular weight GTP-binding protein (Rho), and the regulations of phosphorylation in contractile elements.
Kokubu
N
N
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Satoh
M
M
Takayanagi
I
I
D036002:ADP Ribose Transferases / Q000378:metabolism; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles; D003000:Clonidine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D011817:Rabbits; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D000470:Alkaloids; D002227:Carbazoles; D007211:Indoles; D018340:Receptors, Adrenergic, alpha-1; D013873:Thionucleotides; C063769:KT 5926; D006153:Guanosine Diphosphate; C023427:guanosine 5'-O-(2-thiodiphosphate); D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011493:Protein Kinase C; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D003000:Clonidine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D009638:Norepinephrine