Akt substrate TBC1D1 regulates GLUT1 expression through the mTOR pathway in 3T3-L1 adipocytes
Authors
Zhou, Qiong L.Jiang, Zhen Y.
Holik, John
Chawla, Anil
Hagan, G. Nana
Leszyk, John D.
Czech, Michael P.
UMass Chan Affiliations
Department of Biochemistry and Molecular PharmacologyProgramme in Molecular Medicine
Document Type
Journal ArticlePublication Date
2008-01-25Keywords
3T3-L1 CellsAdipocytes
Animals
Antibodies
Cricetinae
GTPase-Activating Proteins
*Gene Expression Regulation
Glucose Transporter Type 1
Insulin
Mice
Mutation
Nuclear Proteins
Phosphorylation
Protein Kinases
Proto-Oncogene Proteins c-akt
Ribosomal Protein S6 Kinases, 70-kDa
*Signal Transduction
Substrate Specificity
Life Sciences
Medicine and Health Sciences
Metadata
Show full item recordAbstract
Multiple studies have suggested that the protein kinase Akt/PKB (protein kinase B) is required for insulin-stimulated glucose transport in skeletal muscle and adipose cells. In an attempt to understand links between Akt activation and glucose transport regulation, we applied mass spectrometry-based proteomics and bioinformatics approaches to identify potential Akt substrates containing the phospho-Akt substrate motif RXRXXpS/T. The present study describes the identification of the Rab GAP (GTPase-activating protein)-domain containing protein TBC1D1 [TBC (Tre-2/Bub2/Cdc16) domain family, member 1], which is closely related to TBC1D4 [TBC domain family, member 4, also denoted AS160 (Akt substrate of 160 kDa)], as an Akt substrate that is phosphorylated at Thr(590). RNAi (RNA interference)-mediated silencing of TBC1D1 elevated basal deoxyglucose uptake by approx. 61% in 3T3-L1 mouse embryo adipocytes, while the suppression of TBC1D4 and RapGAP220 under the same conditions had little effect on basal and insulin-stimulated deoxyglucose uptake. Silencing of TBC1D1 strongly increased expression of the GLUT1 glucose transporter but not GLUT4 in cultured adipocytes, whereas the decrease in TBC1D4 had no effect. Remarkably, loss of TBC1D1 in 3T3-L1 adipocytes activated the mTOR (mammalian target of rapamycin)-p70 S6 protein kinase pathway, and the increase in GLUT1 expression in the cells treated with TBC1D1 siRNA (small interfering RNA) was blocked by the mTOR inhibitor rapamycin. Furthermore, overexpression of the mutant TBC1D1-T590A, lacking the putative Akt/PKB phosphorylation site, inhibited insulin stimulation of p70 S6 kinase phosphorylation at Thr(389), a phosphorylation induced by mTOR. Taken together, our data suggest that TBC1D1 may be involved in controlling GLUT1 glucose transporter expression through the mTOR-p70 S6 kinase pathway.Source
Biochem J. 2008 May 1;411(3):647-55. Link to article on publisher's siteDOI
10.1042/BJ20071084Permanent Link to this Item
http://hdl.handle.net/20.500.14038/39273PubMed ID
18215134Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1042/BJ20071084
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