Increased expression of G12 and G13 proteins in bronchial smooth muscle of airway hyperresponsive rats.
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.
Chiba
Y
Y
Department of Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan. chiba@hoshi.ac.jp
Misawa
M
M
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
D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020962:Heterotrimeric GTP-Binding Proteins