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Cyclic AMP Regulation of G iα2 and G iα3 mRNAs and Proteins in Astroglial Cells
Author(s) -
El Jamali Amina,
Rachdaoui Nadia,
Dib Karim,
Corrèze Claude
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.71062271.x
Subject(s) - forskolin , messenger rna , northern blot , western blot , microbiology and biotechnology , biology , gene expression , medicine , second messenger system , endocrinology , g protein , chemistry , gene , signal transduction , biochemistry , stimulation
Culture of rat astrocytes in the presence of 10 µ M forskolin, isoproterenol, a nonselective β‐adrenergic agonist, or 8‐bromo‐cyclic AMP increased transiently in a time‐dependent manner the levels of G iα2 and G iα3 mRNAs as measured by northern blot analysis. G iα1 mRNA was not expressed in these cells. After 6–9 h of culture with forskolin or isoproterenol the amounts of G iα2 and G iα3 mRNAs were maximal (150–300% over control). In cells challenged with 8‐bromo‐cyclic AMP, the level of G iα2 mRNA level was maximal after 1 h of culture, while the maximal for G iα3 mRNA was reached after 6 h of culture. For prolonged exposure times (24 h) to these agents the levels of G iα2 and G iα3 mRNAs decreased to the values observed in control cells. The forskolin‐induced increase in G iα2 protein expression measured by western blot analysis was similar to the increase in G iα2 mRNA amount. In contrast, forskolin induced only a modest increase in the quantity of G iα3 protein (150% over control) despite a large increase of G iα3 mRNA content. Transcription rates and RNA stability were measured simultaneously after isolation of newly synthesized mRNA was performed. The half‐lives of G iα mRNAs were ∼0.7 and 3 h for G iα2 and G iα3 , respectively. Culturing astrocytes in the presence of forskolin resulted in an increase in the half‐lives of G iα2 mRNA and G iα3 mRNA by five‐ and twofold, respectively. The relative transcription rate of the G iα3 gene was slightly increased by ∼1.3–1.5‐fold in forskolin‐treated cells but not that of G iα2 gene. These results suggest that cyclic AMP enhanced G iα2 and G iα3 mRNA expression by both transcriptional and posttranscriptional mechanisms, with an increase of G iα mRNA stability as one of the major checkpoints.