Regulation of c-fos Gene Induction and Mitogenic Effect of Transforming Growth factor-β1 in Rat Articular Chondrocyte

Endocrine Journal

MAKOTO OSAKI²  KATSURO IWASAKI²  HIROYUKI SHINDO²  YOUICHI MIYAZAKI²  AKIHIKO YONEKURA²  SHUNICHI YAMASHITA¹  TOMOO TSUKAZAKI² 

[1] Department of Nature Medicine, Atomic Bomb Disease Institute, Nagasaki University School of Medicine;Department of Orthopaedic Surgery, Nagasaki University School of Medicine

关键词: Articular chondrocyte;    TGF-β1;    c-fos gene;   

DOI  :  10.1507/endocrj.46.253

学科分类：内分泌与代谢学

来源: Japan Endocrine Society

【 摘 要 】

References(29)Cited-By(7)We have previously reported that type I transforming growth factor beta (TGF-β1) is a potent stimulator of cell growth in articular chondrocytes. In this study, we examined the mechanism of TGF-β1 induced cellular proliferation by using cultured rat articular chondrocytes (CRAC). A time-course study of [3H]thymidine incorporation upon TGF-β1 (1ng/mL) or 10% fetal bovine serum stimulation revealed that TGF-β1 directly stimulates DNA synthesis in CRAG. Pretreatment with H7, an inhibitor for protein kinase C (PKC), completely blocks TGF-β1-induced proliferation. Since TGF-β1 has been shown to transduce signals through MAP kinase cascades, we investigated the induction of several protooncogenes by Northern blotting. TGF-β1 addition causes an immediate and transient induction of c-fos but not myc or jun mRNA. Furthermore, this c-fos expression is not inhibited by cycloheximide, but is completely abolished by pretreatment with TPA, so that the c-fos gene is a direct target of TGF-β1 signalling and PKC is involved in this c-fos induction. To refine our understanding of TGF-β1 regulation of the c-fos promoter region, we performed chloramphenicol acetyltransferase (CAT) assays. A serial deletion analysis of the c-fos promoter region reveals a TGF-β1 responsive element in a region between -403 and - 329bp upstream of the transcription initiation site. We attempted gel shift assays on this response element with CRAC nuclear extracts. Although this region contains a sis-inducible binding element, we fail to detect specific DNA- protein complexes. Our results, however, suggest that TGF-β1 acts as a primary mitogen in CRAC and this mitogenic activity requires PKC activation. Finally, the subsequent induction of c-fos expression occurs through an as yet unidentified transactivation mechanism.

【 授权许可】

Unknown