The Pro-apoptotic Protein Bim Is a Convergence Point for cAMP/Protein Kinase A- and Glucocorticoid-promoted Apoptosis of Lymphoid Cells

• Published in: The Journal of biological chemistry Vol. 279; no. 20; pp. 20858 - 20865
• Main Authors: Zhang, Lingzhi, Insel, Paul A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 14.05.2004
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - physiology; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Binding Sites; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Cycle; Cell Line, Tumor; Cyclic AMP - analogs & derivatives; Cyclic AMP - pharmacology; Cyclic AMP-Dependent Protein Kinases - metabolism; Dexamethasone - pharmacology; Flow Cytometry; Gene Expression Regulation, Neoplastic - genetics; Glucocorticoids - pharmacology; Humans; Isoproterenol - pharmacology; Kinetics; Lymphoma, T-Cell - pathology; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Recombinant Proteins - metabolism; RNA, Messenger - genetics; Thionucleotides - pharmacology; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M310643200

The mechanisms by which cAMP mediates apoptosis are not well understood. In the current studies, we used wild-type (WT) S49 T-lymphoma cells and the kin – variant (which lacks protein kinase A (PKA)) to examine cAMP/PKA-mediated apoptosis. The cAMP analog, 8-CPT-cAMP, increased phosphorylation of the cAMP response element-binding protein (CREB), activated caspase-3, and induced apoptosis in WT but not in kin – S49 cells. Using an array of 96 apoptosis-related genes, we found that treatment of WT cells with 8-CPT-cAMP for 24 h induced expression of mRNA for the pro-apoptotic gene, Bim . Real-time PCR analysis indicated that 8-CPT-cAMP increased Bim RNA in WT cells in <2 h and maintained this increase for >24 h. Bim protein expression increased in WT but not kin – cells treated with 8-CPT-cAMP or with the β-adrenergic receptor agonist isoproterenol. Both apoptosis and Bim expression were reversible with removal of 8-CPT-cAMP after <6 h. The glucocorticoid dexamethasone also promoted apoptosis and Bim expression in S49 cells. In contrast, both UV light and anti-mouse Fas monoclonal antibody promoted apoptosis in S49 cells but did not induce Bim expression. 8-CPT-cAMP also induced Bim expression and enhanced dexamethasone-promoted apoptosis in human T-cell leukemia CEM-C7–14 (glucocorticoid-sensitive) and CEM-C1–15 (glucocorticoid-resistant) cells; increased Bim expression in 8-CPT-cAMP-treated CEM-C1–15 cells correlated with conversion of the cells from resistance to sensitivity to glucocorticoid-promoted apoptosis. Induction of Bim appears to be a key event in cAMP-promoted apoptosis in both murine and human T-cell lymphoma and leukemia cells and thus appears to be a convergence point for the killing of such cells by glucocorticoids and agents that elevate cAMP.