Insulin-like growth factor-I induces bcl-2 promoter through the transcription factor cAMP-response element-binding protein.
Insulin-like growth factor-I (IGF-I) is known to prevent apoptosis induced by diverse stimuli. The present study examined the effect of IGF-I on the promoter activity of bcl-2, a gene with antiapoptotic function. A luciferase reporter driven by the promoter region of bcl-2 from -1640 to -1287 base pairs upstream of the translation start site containing a cAMP-response element was used in transient transfection assays. Treatment of PC12 cells with IGF-I enhanced the bcl-2 promoter activity by 2.3-fold, which was inhibited significantly (p < 0.01) by SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK). Cotransfection of the bcl-2 promoter with MAPK kinase 6 and the beta isozyme of p38 MAPK resulted in 2-3-fold increase in the reporter activity. The dominant negative form of MAPKAP-K3, a downstream kinase activated by p38 MAPK, and the dominant negative form of cAMP-response element-binding protein, inhibited the reporter gene activation by IGF-I and p38beta MAPK significantly (p < 0.01). IGF-I increased the activity of p38beta MAPK introduced into the cells by adenoviral infection. Thus, we have characterized a novel signaling pathway (MAPK kinase 6/p38beta MAPK/MAPKAP-K3) that defines a transcriptional mechanism for the induction of the antiapoptotic protein Bcl-2 by IGF-I through the nuclear transcription factor cAMP-response element-binding protein in PC12 cells.
Pugazhenthi
S
S
Section of Endocrinology, Veterans Affairs Medical Center, Denver, Colorado 80220, USA.
Miller
E
E
Sable
C
C
Young
P
P
Heidenreich
K A
KA
Boxer
L M
LM
Reusch
J E
JE
D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D019254:Genes, bcl-2 / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007700:Kinetics; D008156:Luciferases / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016716:PC12 Cells; D011401:Promoter Regions, Genetic / Q000235:genetics*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D017384:Sequence Deletion; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
D017362:Cyclic AMP Response Element-Binding Protein; D011993:Recombinant Fusion Proteins; D007334:Insulin-Like Growth Factor I; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases