title: Molecular mechanisms of early growth response protein-1 (EGR-1) expression by quercetin in INS-1 beta-cells.
abstract: Early growth response-1 (EGR-1), one of immediate early response genes, is involved in diverse cellular response. We recently reported that quercetin increased catalytic subunit of γ-glutamylcysteine ligase (GCLC) via the interaction of EGR-1 to GCLC promoter in INS-1 beta-cells. Therefore, this study investigated molecular mechanisms of quercetin-induced EGR-1 expression in INS-1 cells. Quercetin significantly induced EGR-1 protein and its mRNA expressions. This induction of EGR-1 was completely blocked by pretreatment with a PKA inhibitor, H89 and partially blocked by a p38 inhibitor, SB203580. Additionally, the siRNA-mediated inhibition of PKAα and p38 resulted in significant reduction of quercetin-induced EGR-1 promoter activity. Also, quercetin-induced EGR-1 protein expression was significantly decreased in the cells transfected with PKAα siRNA. Study using truncated EGR-1 promoter constructs showed that serum response element (SRE) sites, not cAMP response element site, were essential for EGR-1 transcription. However, electrophoretic mobility shift assay showed that quercetin did not affect the band intensity of DNA-protein complex on SRE site of EGR-1 promoter. Also, immune-shift assay using serum response factor (SRF) and phospho-SRF antibodies showed no difference between control and quercetin-treated groups. Collectively, quercetin-induced EGR-1 expression is largely dependent on PKA and partly on p38 MAPK pathway, and SRE sites of EGR-1 promoter are involved in quercetin-induced EGR-1 transcriptional activity.
authors.affiliation: Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
authors.forename: Seo-Yoon
authors.initials: SY
authors.lastname: Chang
authors.forename: Jae Min
authors.initials: JM
authors.lastname: Cho
authors.forename: Dong-Bin
authors.initials: DB
authors.lastname: Kim
authors.forename: Hyun-Jong
authors.initials: HJ
authors.lastname: Jang
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Ko
authors.forename: Yang-Hyeok
authors.initials: YH
authors.lastname: Jo
authors.forename: Myung-Jun
authors.initials: MJ
authors.lastname: Kim
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D055785:Gene Knockdown Techniques; D005721:Glutamate-Cysteine Ligase / Q000235:genetics; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011794:Quercetin / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D027602:Serum Response Element; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011794:Quercetin; D017868:Cyclic AMP-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D005721:Glutamate-Cysteine Ligase; C544143:GCLC protein, rat