PMID:19740738

Citation	Peck, GR, Chavez, JA, Roach, WG, Budnik, BA, Lane, WS, Karlsson, HK, Zierath, JR and Lienhard, GE (2009) Insulin-stimulated phosphorylation of the Rab GTPase-activating protein TBC1D1 regulates GLUT4 translocation. J. Biol. Chem. 284:30016-23
Abstract	Insulin stimulates the translocation of the glucose transporter GLUT4 from intracellular locations to the plasma membrane in adipose and muscle cells. Prior studies have shown that Akt phosphorylation of the Rab GTPase-activating protein, AS160 (160-kDa Akt substrate; also known as TBC1D4), triggers GLUT4 translocation, most likely by suppressing its Rab GTPase-activating protein activity. However, the regulation of a very similar protein, TBC1D1 (TBC domain family, member 1), which is mainly found in muscle, in insulin-stimulated GLUT4 translocation has been unclear. In the present study, we have identified likely Akt sites of insulin-stimulated phosphorylation of TBC1D1 in C2C12 myotubes. We show that a mutant of TBC1D1, in which several Akt sites have been converted to alanine, is considerably more inhibitory to insulin-stimulated GLUT4 translocation than wild-type TBC1D1. This result thus indicates that similar to AS160, Akt phosphorylation of TBC1D1 enables GLUT4 translocation. We also show that in addition to Akt activation, activation of the AMP-dependent protein kinase partially relieves the inhibition of GLUT4 translocation by TBC1D1. Finally, we show that the R125W variant of TBC1D1, which has been genetically associated with obesity, is equally inhibitory to insulin-stimulated GLUT4 translocation, as is wild-type TBC1D1, and that healthy and type 2 diabetic individuals express approximately the same level of TBC1D1 in biopsies of vastus lateralis muscle. In conclusion, phosphorylation of TBC1D1 is required for GLUT4 translocation. Thus, the regulation of TBC1D1 resembles that of its paralog, AS160.
Links	PubMed PMC2781555 Online version:10.1074/jbc.M109.035568
Keywords	3T3-L1 Cells; Animals; Diabetes Mellitus, Type 2/metabolism; GTPase-Activating Proteins/metabolism; Glucose Transporter Type 4/metabolism; Insulin/pharmacology; Mice; Muscle, Skeletal/chemistry; Nuclear Proteins/analysis; Nuclear Proteins/metabolism; Phosphorylation; Protein Transport/drug effects; Proto-Oncogene Proteins c-akt/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
MOUSE:AAPK2	enables	GO:0004674: protein serine/threonine kinase activity	ECO:0000269: experimental evidence used in manual assertion		F		Seeded From UniProt	complete

References

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