The pro-apoptotic protein Bim is a convergence point for cAMP/protein kinase A- and glucocorticoid-promoted apoptosis of lymphoid cells.
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 beta-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.
Department of Pharmacology, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0636, USA.
Lingzhi
L
Zhang
Paul A
PA
Insel
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D016399:Lymphoma, T-Cell / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology; D014162:Transfection
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D002352:Carrier Proteins; D005938:Glucocorticoids; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D003907:Dexamethasone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol