Identification of TBC7 having TBC domain as a novel binding protein to TSC1-TSC2 complex.
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.
Biosignal Research Center, Kobe University, Kobe 657-8501, Japan.
Akio
A
Nakashima
Ken-ichi
K
Yoshino
Takafumi
T
Miyamoto
Satoshi
S
Eguchi
Noriko
N
Oshiro
Ushio
U
Kikkawa
Kazuyoshi
K
Yonezawa
D001665:Binding Sites; D002352:Carrier Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D015536:Down-Regulation; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C522923:TBC1D7 protein, human; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases