Akt/Protein Kinase B Up-regulates Bcl-2 Expression through cAMP-response Element-binding Protein

• Published in: The Journal of biological chemistry Vol. 275; no. 15; pp. 10761 - 10766
• Main Authors: Pugazhenthi, Subbiah, Nesterova, Albina, Sable, Carol, Heidenreich, Kim A., Boxer, Linda M., Heasley, Lynn E., Reusch, Jane E.-B.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14-04-2000; American Society for Biochemistry and Molecular Biology
• Subjects: Akt gene; Animals; cyclic AMP response element-binding protein; Cyclic AMP Response Element-Binding Protein - physiology; Insulin-Like Growth Factor I - pharmacology; luciferase; luciferase reporter gene; PC12 Cells; Phosphatidylinositol 3-Kinases - physiology; Phosphorylation; Promoter Regions, Genetic; Protein-Serine-Threonine Kinases; Proto-Oncogene Proteins - physiology; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2 - biosynthesis; Proto-Oncogene Proteins c-bcl-2 - genetics; Rats; Up-Regulation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.275.15.10761

In our previous study we showed that insulin-like growth factor-I induces a cAMP-response element (CRE) site-containing Bcl-2 promoter through a novel signaling pathway involving mitogen-activated protein kinase kinase 6/p38β mitogen-activated protein kinase/MAP kinase-activated protein kinase-3/cAMP-response element-binding protein (CREB) (Pugazhenthi, S., Miller, E., Sable, C., Young, P., Heidenreich, K. A., Boxer, L. M., and Reusch, J. E.-B. (1999)J. Biol. Chem. 274, 27529–27535). In the present investigation, we define a second pathway contributing to CREB-dependent up-regulation of Bcl-2 expression as a novel anti-apoptotic function of Akt signaling. To examine the role of Akt on Bcl-2 expression, a series of transient transfections using a luciferase reporter gene driven by the promoter region of Bcl-2 containing a CRE were carried out. Pharmacological inhibition of phosphatidylinositol (PI) 3-kinase, the upstream kinase of Akt, with LY294002 led to a 45% decrease in Bcl-2 promoter activity. The reporter activity was enhanced 2.3-fold by overexpression of active p110 subunit of PI 3-kinase and inhibited 44% by the dominant negative p85 subunit of PI 3-kinase. Cotransfection with 3-phosphoinositide-dependent kinase (PDK1), which is required for the full activation of Akt, resulted in enhanced luciferase activity. Insulin-like growth factor-I-mediated induction of Bcl-2 promoter activity was decreased significantly (p < 0.01) by the dominant negative forms of p85 subunit of PI 3-kinase, PDK1, and Akt. These data indicate that regulation of Bcl-2 expression by IGF-I involves a signaling cascade mediated by PI 3-kinase/PDK1/Akt/CREB. Furthermore, we measured the Bcl-2 mRNA in PC12 cells overexpressing Akt by real-time quantitative reverse transcription-polymerase chain reaction using the TaqManTMfluorogenic probe system. We observed a 2.1-fold increase in Bcl-2 mRNA levels in the Akt cell line compared with control PC12 cells, supporting the observation that enhanced CREB activity by Akt signaling leads to increased Bcl-2 promoter activity and cell survival.