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Mol Cell. 2012 Aug 24;47(4):535-46. doi: 10.1016/j.molcel.2012.06.009. Epub 2012 Jul 12.

TBC1D7 is a third subunit of the TSC1-TSC2 complex upstream of mTORC1.

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  • 1Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, MA 02115, USA.

Abstract

The tuberous sclerosis complex (TSC) tumor suppressors form the TSC1-TSC2 complex, which limits cell growth in response to poor growth conditions. Through its GTPase-activating protein (GAP) activity toward Rheb, this complex inhibits the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1), a key promoter of cell growth. Here, we identify and biochemically characterize TBC1D7 as a stably associated and ubiquitous third core subunit of the TSC1-TSC2 complex. We demonstrate that the TSC1-TSC2-TBC1D7 (TSC-TBC) complex is the functional complex that senses specific cellular growth conditions and possesses Rheb-GAP activity. Sequencing analyses of samples from TSC patients suggest that TBC1D7 is unlikely to represent TSC3. TBC1D7 knockdown decreases the association of TSC1 and TSC2 leading to decreased Rheb-GAP activity, without effects on the localization of TSC2 to the lysosome. Like the other TSC-TBC components, TBC1D7 knockdown results in increased mTORC1 signaling, delayed induction of autophagy, and enhanced cell growth under poor growth conditions.

Copyright © 2012 Elsevier Inc. All rights reserved.

PMID:
22795129
[PubMed - indexed for MEDLINE]
PMCID:
PMC3693578
Free PMC Article

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