Cholera toxin mediated regulation of the expression of Gq alpha and G11 alpha GTP binding proteins.
- Author:
Bukhtiar H SHAH
1
Author Information
1. Department of Physiology and Pharmacology, Aga Khan University, Karachi, Pakistan.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
G-proteins;
cholera toxin;
C6 glioma cells;
forskolin;
dibutyryl cAMP;
protein kinase A.
- MeSH:
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
- From:Experimental & Molecular Medicine
1999;31(2):89-94
- CountryRepublic of Korea
- Language:English
-
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.
