Identification of TBC7 having TBC domain as a novel binding protein to TSC1–TSC2 complex

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• 作者：Akio Nakashima ; Ken-ichi Yoshino ; Takafumi Miyamoto ; Satoshi Eguchi ; Noriko Oshiro ; Ushio Kikkawa ; Kazuyoshi Yonezawa
• 关键词：TSC1 ; TSC2 ; TBC7 ; Rheb ; mTOR ; Protein phosphorylation ; Ubiquitination
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2007
• 出版时间：14 September 2007
• 年：2007
• 卷：361
• 期：1
• 页码：218-223
• 全文大小：418 K

文摘

TBC7, a TBC (Tre-2/Bub2/Cdc16) 1 domain protein, was identified as a novel binding protein to the TSC1–TSC2 tumor suppressor complex by peptide mass fingerprinting analysis of the proteins immunoprecipitated with FLAG-epitope tagged TSC1 and TSC2 from the transfected mammalian cells. The in vivo and in vitro association of TBC7 and the TSC1–TSC2 complex was confirmed by the co-immunoprecipitation and pull-down analysis, respectively, and TBC7 was revealed to bind to the C-terminal half region of TSC1, which is distinct from the binding site with TSC2. The immunofluorescence microscopy and subcellular fractionation showed that TBC7 co-localizes with the tumor suppressor complex in the endomembrane. Overexpression of TBC7 enhanced ubiquitination of TSC1 and increased phosphorylation of S6 protein by S6 kinase, that is located in the mTOR-signaling pathway. These results indicate TBC7 could take a part in the negative regulation of the tumor suppressor complex through facilitating the downregulation of TSC1.