Exp Mol Med.  1999 Jun;31(2):89-94.

Cholera toxin mediated regulation of the expression of Gq alpha and G11 alpha GTP binding proteins

• Shah BH

Abstract

Previously it has been shown that persistent activation of the stimulatory adenylyl cyclase pathway with cholera toxin (CT) downregulates the Gs alpha polypeptide (80%) in a cAMP-independent manner in C6 glioma cells (Shah, 1997). This study was conducted to examine the short and long term effects of CT on the regulation of pertussis toxin-sensitive and -insensitive G proteins and their transcripts in C6 glioma cells. Treatment of C6 cells with CT (100 ng/ml) up to 16 h had no effect on either Gi or Gq/11 alpha proteins. However, prolonged exposure (24-48 h) caused increased expression of Gi (20-30%) and Gq/11 alpha proteins (40%). Urea gradient gels, which can separate Gq alpha and G11 alpha proteins, revealed that prolonged CT treatment increased the expression of both of these G proteins. The CT-mediated enhanced expression of Gq alpha and G11 alpha proteins was accompanied by increased mRNA levels of these proteins as determined by RT/PCR. Cyclic-AMP elevating agents like forskolin (10 microM) and db-cAMP (1 mM) mimicked the effect of CT on Gi but not Gq/11 alpha proteins. These studies show long term cAMP-dependent regulation of Gi and cAMP-independent expression of Gq/11 alpha proteins in C6 glioma cells.

Keyword

G-proteins; cholera toxin; C6 glioma cells; forskolin; dibutyryl cAMP; protein kinase A.

MeSH Terms

Animal
Blotting, Western
Bucladesine/pharmacology
Cholera Toxin/pharmacology*
Cyclic AMP-Dependent Protein Kinases/metabolism
Forskolin/pharmacology
GTP-Binding Proteins/genetics*
GTP-Binding Proteins/biosynthesis
Gene Expression Regulation*
Glioma
Membrane Proteins/analysis
RNA, Messenger/metabolism
RNA, Messenger/genetics
Rats
Reverse Transcriptase Polymerase Chain Reaction