title: Response gene to complement 32 is essential for fibroblast activation in renal fibrosis.
abstract: Response gene to complement 32 (RGC-32) is a downstream target of transforming growth factor-β (TGF-β). TGF-β is known to play a pathogenic role in renal fibrosis. In this study, we investigated RGC-32 function in renal fibrosis following unilateral ureteral obstruction (UUO) in mice, a model of progressive tubulointerstitial fibrosis. RGC-32 is normally expressed only in blood vessels of mouse kidney. However, UUO induces RGC-32 expression in renal interstitial cells at the early stage of kidney injury, suggesting that RGC-32 is involved in interstitial fibroblast activation. Indeed, expression of smooth muscle α-actin (α-SMA), an indicator of fibroblast activation, is limited to the interstitial cells at the early stage, and became apparent later in both interstitial and tubular cells. RGC-32 knockdown by shRNA significantly inhibits UUO-induced renal structural damage, α-SMA expression and collagen deposition, suggesting that RGC-32 is essential for the onset of renal interstitial fibrosis. In vitro studies indicate that RGC-32 mediates TGF-β-induced fibroblast activation. Mechanistically, RGC-32 interacts with Smad3 and enhances Smad3 binding to the Smad binding element in α-SMA promoter as demonstrated by DNA affinity assay. In the chromatin setting, Smad3, but not Smad2, binds to α-SMA promoter in fibroblasts. RGC-32 appears to be essential for Smad3 interaction with the promoters of fibroblast activation-related genes in vivo. Functionally, RGC-32 is crucial for Smad3-mediated α-SMA promoter activity. Taken together, we identify RGC-32 as a novel fibrogenic factor contributing to the pathogenesis of renal fibrosis through fibroblast activation.
authors: Department of Physiology & Pharmacology, University of Georgia, Athens, Georgia 30602.
authors: Zuguo
authors: Z
authors: Li
authors: Department of Physiology & Pharmacology, University of Georgia, Athens, Georgia 30602.
authors: Wei-Bing
authors: WB
authors: Xie
authors: Center for Molecular Physiology Research, Children's National Medical Center, Washington, D. C. 20010.
authors: Crisanto S
authors: CS
authors: Escano
authors: Center for Molecular Physiology Research, Children's National Medical Center, Washington, D. C. 20010.
authors: Laureano D
authors: LD
authors: Asico
authors: Department of Physiology & Pharmacology, University of Georgia, Athens, Georgia 30602.
authors: Qiyun
authors: Q
authors: Xie
authors: Center for Molecular Physiology Research, Children's National Medical Center, Washington, D. C. 20010; Georgetown University Medical Center, Washington, D. C. 20007.
authors: Pedro A
authors: PA
authors: Jose
authors: Department of Physiology & Pharmacology, University of Georgia, Athens, Georgia 30602. Electronic address: sc229@uga.edu.
authors: Shi-You
authors: SY
authors: Chen
mesh_terms: D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D002460:Cell Line; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D005355:Fibrosis; D005786:Gene Expression Regulation; D006801:Humans; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D007674:Kidney Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D009687:Nuclear Proteins; C520017:Rgc-32 protein, mouse; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D003094:Collagen