Insulin-like growth factor-1 increases skeletal muscle dihydropyridine receptor alpha 1S transcriptional activity by acting on the cAMP-response element-binding protein element of the promoter region.
Previous work from our laboratory has shown that insulin-like growth factor 1 (IGF-1) increases the expression of the skeletal muscle dihydropyridine receptor (DHPR) alpha(1) subunit by regulating DHPR alpha(1S) nuclear transcription. In this study, we investigated the mechanism by which IGF-1 enhances expression of the DHPR alpha(1S) gene. To this end, the promoter region of the mouse DHPR alpha(1S) gene was recently cloned and sequenced and various promoter deletion-luciferase reporter constructs were used. These constructs were transfected into C2C12 cells and IGF-1 effects were measured by recording luciferase activity. IGF-1 significantly enhanced DHPR alpha(1S) transcription in those constructs carrying cAMP-response element-binding protein (CREB) binding site but not in CREB core binding site mutants. Gel mobility shift assay using a double stranded oligonucleotide for the CREB site in the promoter region, and competition experiments with excess unlabeled or mutated promoter oligonucleotide, and unlabeled consensus CREB oligonucleotide demonstrated that IGF-1 induces CREB binding to the DHPR alpha(1S) promoter. IGF-1-mediated enhancement in charge movement was prevented by incubating the cells with antisense but not with sense oligonucleotides against CREB. These results support the conclusion that IGF-1 regulates DHPR alpha(1S) transcription in muscle cells by acting on the CREB element of the promoter.
Zheng
Zhenlin
Z
Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
Wang
Zhong-Min
ZM
Delbono
Osvaldo
O
D000818:Animals; D001483:Base Sequence; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000235:genetics*; D003001:Cloning, Molecular; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000502:physiology*; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*
D020746:Calcium Channels, L-Type; D017362:Cyclic AMP Response Element-Binding Protein; D020319:Oligodeoxyribonucleotides, Antisense; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D008156:Luciferases