Exendin-4 induction of Egr-1 expression in INS-1 beta-cells: interaction of SRF, not YY1, with SRE site of rat Egr-1 promoter.
Glucagon-like peptide-1 (GLP-1) induces several immediate early response genes such as c-fos, c-jun, and early growth response-1 (Egr-1), which are involved in cell proliferation and differentiation. We recently reported that exendin-4 (EX-4), a potent GLP-1 agonist, upregulated Egr-1 expression via phosphorylation of CREB, a transcription factor in INS-1 beta-cells. This study was designed to investigate the role of another transcription factors, serum response factor (SRF) and Yin Yang-1 (YY1), in EX-4-induced Egr-1 expression. EX-4 significantly increased Egr-1 mRNA and subsequently its protein level. EX-4-induced Egr-1 expression was inhibited by pretreatment with a PKA inhibitor, H-89, and an MEK inhibitor, PD 98059. The siRNA-mediated inhibition of PKA and ERK1 resulted in significant reduction of EX-4-induced Egr-1 expression. Promoter analyses showed that SRE clusters were essential for Egr-1 transcription, and YY1 overexpression did not affect Egr-1 promoter activity. EMSA results demonstrated that EX-4-induced transient increase in DNA-protein complex on SRE site, and that both SRF and phospho-SRF were bound to this site. Treatment of either YY1 consensus oligonucleotide or YY1 antibody did not effect the change of density or migration of the DNA-protein complex. Collectively, EX-4-induced Egr-1 expression is largely dependent on cAMP-mediated extracellular signal-regulated kinase activation, and EX-4 induces Egr-1 transcription via the interaction of SRF and phospho-SRF to SRE sites.
Kim
Myung-Jun
MJ
Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, South Korea.
Kang
Jung-Hoon
JH
Chang
Seo-Yoon
SY
Jang
Hyun-Jong
HJ
Ryu
Gyeong Ryul
GR
Ko
Seung Hyun
SH
Jeong
In-Kyung
IK
Kim
Myung-Suk
MS
Jo
Yang-Hyeok
YH
D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D000077270:Exenatide; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020218:Response Elements / Q000235:genetics*; D026362:Serum Response Factor / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014688:Venoms / Q000494:pharmacology*; D050986:YY1 Transcription Factor / Q000378:metabolism*
D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D010455:Peptides; D012333:RNA, Messenger; D026362:Serum Response Factor; D014688:Venoms; D050986:YY1 Transcription Factor; C494700:Yy1 protein, rat; D000077270:Exenatide; D000242:Cyclic AMP; D048049:Extracellular Signal-Regulated MAP Kinases