Angiotensin II stimulates transcription of insulin-like growth factor I receptor in vascular smooth muscle cells: role of nuclear factor-kappaB.
Increased expression of the IGF-I receptor (IGF-IR) is associated with proliferation and survival of vascular smooth muscle cells (VSMCs). In cultured VSMCs, we reported that angiotensin II (Ang II) increases transcription and expression of IGF-IR. Now, we show that mesenteric arteries of rats infused with Ang II develop thickening and increased IGF-IR expression. To determine how Ang II transcriptionally regulates IGF-IR expression in VSMCs, we generated 5'-end deletions of the IGF-IR promoter and measured Ang II-induced promoter-luciferase activity in VSMCs. Activities from these promoter sequences suggested that the Ang II-responsive region is located between -270 and -135 of the IGF-IR promoter. Using a DNase I foot printing analysis, we identified two putative nuclear factor-kappaB (NF-kappaB)-like sequences located in the same region of the IGF-IR promoter. When we mutated either of these NF-kappaB-like sites, Ang II-induced IGF-IR promoter activity decreased sharply. Electrophoretic mobility gel shift, anti-p50 of NF-kappaB supershift and chromatin immunoprecipitation assays demonstrated that both the p65 and p50 subunits of NF-kappaB will bind to this Ang II response element in the IGF-IR promoter. When we blocked the Ras/MAPK kinase 1 pathway or the inhibitory-kappaB kinase pathway, both Ang II-induced IGF-IR promoter activity and expression of IGF-IR protein significantly declined. Our results indicate that the mechanism by which Ang II stimulates IGF-IR expression in VSMCs involves NF-kappaB binding to NF-kappaB sites in the IGF-IR promoter, leading to expression of IGF-IR through both Ras/MAPK kinase 1-and inhibitory-kappaB kinase-dependent pathways. Because IGF-IR is a major factor associated with thickening of mesenteric vessels, our results provide potential therapeutic targets.
Ma
Yewei
Y
Department of Medicine, One Baylor Plaza, N520, Baylor College of Medicine, Houston, Texas 77030, USA.
Zhang
Liping
L
Peng
Tao
T
Cheng
Jizhong
J
Taneja
Shilpa
S
Zhang
Jiqiang
J
Delafontaine
Patrice
P
Du
Jie
J
D000804:Angiotensin II / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D003850:Deoxyribonuclease I / Q000378:metabolism; D017353:Gene Deletion; D017930:Genes, Reporter; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051996:Transcription Factor RelA / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D051996:Transcription Factor RelA; D000804:Angiotensin II; D008156:Luciferases; D017526:Receptor, IGF Type 1; D003850:Deoxyribonuclease I