G12 requirement for thrombin-stimulated gene expression and DNA synthesis in 1321N1 astrocytoma cells.
Thrombin stimulation of 1321N1 astrocytoma cells leads to Ras-dependent AP-1-mediated transcriptional activation and to DNA replication. In contrast to what has been observed in most cell systems, in 1321N1 cells these responses are pertussis toxin-insensitive. The pertussis toxin-insensitive G-protein G12 has been implicated in cell growth and transformation in different cell systems. We have examined the potential role of this protein in AP-1-mediated transcriptional activation and DNA synthesis in 1321N1 cells. Transient expression of an activated (GTPase-deficient) mutant of G alpha 12 increased AP-1-dependent gene expression. This response was inhibited by co-expression of a dominant negative Ala-15 Ras protein. To determine whether the pertussis toxin-insensitive G12 protein is involved in the thrombin-stimulated DNA synthesis, an inhibitory antibody against the C-terminal sequence of G alpha 12 subunit was microinjected into 1321N1 cells. Microinjection of the anti-G alpha 12 resulted in a concentration-dependent inhibition of thrombin-stimulated DNA synthesis. In contrast, microinjection of nonimmune IgG or an antibody directed against the C terminus of G alpha o did not reduce the mitogenic response to thrombin. Furthermore, microinjection of the anti-G alpha 12 antibody had no effect on fibroblast growth factor-stimulated DNA synthesis. These results demonstrate a specific role for G alpha 12 in the mitogenic response to thrombin in human astroglial cells.[1]References
- G12 requirement for thrombin-stimulated gene expression and DNA synthesis in 1321N1 astrocytoma cells. Aragay, A.M., Collins, L.R., Post, G.R., Watson, A.J., Feramisco, J.R., Brown, J.H., Simon, M.I. J. Biol. Chem. (1995) [Pubmed]
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