steroids up-regulate p66shc longevity protein in growth regulation by inhibiting its ubiquitination类固醇调控p66shc长寿蛋白通过抑制生长调节它的泛素化.pdf

Steroids Up-Regulate p66Shc Longevity Protein in Growth Regulation by Inhibiting Its Ubiquitination 1 1 1 1 1 Santosh Kumar , Satyendra Kumar , Mythilypriya Rajendran , Syed Mahfuzul Alam , Fen-Fen Lin , Pi- Wan Cheng1,2, Ming-Fong Lin1,2* 1 Department of Biochemistry and Molecular Biology, College of Medicine, University of Nebraska Medical Center, Omaha, Nebraska, United States of America, 2 Eppley Institute for Cancer Research, University of Nebraska Medical Center, Omaha, Nebraska, United States of America Abstract Background: p66Shc, an isoform of Shc adaptor proteins, mediates diverse signals, including cellular stress and mouse longevity. p66Shc protein level is elevated in several carcinomas and steroid-treated human cancer cells. Several lines of evidence indicate that p66Shc plays a critical role in steroid-related carcinogenesis, and steroids play a role in its elevated levels in those cells without known mechanism. Methods and Findings: In this study, we investigated the molecular mechanism by which steroid hormones up-regulate p66Shc protein level. In steroid-treated human prostate and ovarian cancer cells, p66Shc protein levels were elevated, correlating with increased cell proliferation. These steroid effects on p66Shc protein and cell growth were competed out by the respective antagonist. Further, actinomycin D and cyclohexamide could only partially block the elevated p66Shc protein level by steroids. Treatment with proteasomal inhibitors, but not lysosomal protease inhibitor, resulted in elevated p66Shc protein levels, even higher than that by steroids. Using prostate cancer cells as a model, immunoprecipitation revealed that androgens and proteasomal inhibitors reduce the ubiquitinated p66Sh