The v-SNARE Vti1a regulates insulin-stimulated glucose transport and Acrp30 secretion in 3T3-L1 adipocytes.
Regulated exocytosis in adipocytes mediates key functions, exemplified by insulin-stimulated secretion of peptides such as adiponectin and recycling of intracellular membranes containing GLUT4 glucose transporters to the cell surface. Using a proteomics approach, the v-SNARE Vti1a (vps10p tail interacting 1a) was identified by mass spectrometry in purified GLUT4-containing membranes. Insulin treatment of 3T3-L1 adipocytes decreased the amounts of both Vti1a and GLUT4 in these membranes, confirming that Vti1a is a component of insulin-sensitive GLUT4-containing vesicles. In the basal state, endogenous Vti1a colocalizes exclusively with perinuclear GLUT4. Although Vti1a has previously been reported to be a v-SNARE localized in the trans-Golgi network, treatment with brefeldin A failed to significantly modify Vti1a or GLUT4 localization while completely dispersing Golgi and trans-Golgi network marker proteins. Furthermore, depletion of Vti1a protein in cultured adipocytes through small interfering RNA-based gene silencing significantly inhibited both adiponectin secretion and insulin-stimulated deoxyglucose uptake. Taken together, these results suggest that the v-SNARE Vti1a may regulate a step common to both GLUT4 and Acrp30 trafficking in 3T3-L1 adipocytes.
Bose
Avirup
A
Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
Guilherme
Adilson
A
Huang
Shaohui
S
Hubbard
Andrea C
AC
Lane
Charles R
CR
Soriano
Neil A
NA
Czech
Michael P
MP
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D052242:Adiponectin / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D040901:Proteomics; D050766:Qb-SNARE Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D021601:trans-Golgi Network
D052242:Adiponectin; C499919:Adipoq protein, mouse; D051275:Glucose Transporter Type 4; D007004:Hypoglycemic Agents; D007328:Insulin; D050766:Qb-SNARE Proteins; D034741:RNA, Small Interfering; C495693:Slc2a4 protein, mouse; C491418:Vti1a protein, mouse; D005947:Glucose