Cyclic AMP regulates G oα protein and mRNA levels by modulating the transcriptional rate of G oα gene

Abstract

In rat astroglial cells, four G oα transcripts were found: G o2α mRNA (5.7 kb) and three G o1α mRNAs (4.0, 3.0 and 2.3 kb). However, G o2α but little G oα1 proteins were present in membrane-enriched fractions. Culturing astroglial cells with forskolin (10 μM) or isoproterenol (10 μM) a β-adrenergic agonist increased transiently in a time-dependent manner the levels of G oα proteins. The degradation rate of G oα proteins was slightly decreased by the cAMP treatment. In parallel, forskolin (10 μM) treatment increased transiently the amounts of both G o1α and G o2α mRNAs. The relative transcription rate of G oα gene was increased by 1.7-fold in forskolin-treated cells whereas the half-lives of G o1α and G o2α mRNAs were not significantly changed. These results suggest that cAMP regulates the transcription rate of G oα gene and this is compatible with the existence of a cAMP responsive element in the promoter of the G oα gene.