title: Increased expression of G12 and G13 proteins in bronchial smooth muscle of airway hyperresponsive rats.
abstract: OBJECTIVE
  To obtain information on the activation pathway of the monomeric G protein, RhoA, in bronchial smooth muscle, the expression of G alpha12 and G alpha13 in bronchial smooth muscle of the rat was determined. The levels of these G proteins were also compared between antigen-induced airway hyperresponsive and normal control groups.
  
  
  METHODS
  Actively sensitized rats were repeatedly challenged by antigen inhalation. Twenty-four hours after the final antigen challenge, membrane preparations of bronchial smooth muscles were prepared. Immunoblottings were performed, and the density ratios of G alpha12/beta-actin and G alpha13/beta-actin were calculated to quantify the levels of these G-protein alpha subunits.
  
  
  RESULTS
  Both G alpha12 and G alpha13 proteins were expressed in rat bronchial smooth muscle. The levels of bronchial G alpha12 and G alpha13 proteins in the repeatedly antigen challenged rats were significantly increased as compared with those in control animals; the magnitude of upregulation in the airway-hyperresponsive group was 89% and 68% in the control group, respectively.
  
  
  CONCLUSIONS
  G alpha12 and G alpha13 proteins were expressed in rat bronchial smooth muscle. Considering the probable involvement of G12 and G13 proteins in Ca2+ sensitization through Rho protein, the augmented expression of such G proteins after repeated antigen challenge may be responsible for the hyperresponsiveness of bronchial smooth muscle contraction in rats.
authors.affiliation: Department of Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan. chiba@hoshi.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Chiba
authors.forename: M
authors.initials: M
authors.lastname: Misawa
mesh_terms: D000818:Animals; D001980:Bronchi / Q000378:metabolism*; D016535:Bronchial Hyperreactivity / Q000378:metabolism*; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020962:Heterotrimeric GTP-Binding Proteins / Q000096:biosynthesis*; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020962:Heterotrimeric GTP-Binding Proteins