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The SUMO Conjugating Enzyme Ubc9 is a Regulator of GLUT4 Turnover and Targeting to the Insulin-Responsive Storage Compartment in 3T3-L1 Adipocytes
Ist Teil von
Diabetes (New York, N.Y.), 2007-08, Vol.56 (8), p.1977-1985
Ort / Verlag
Alexandria, VA: American Diabetes Association
Erscheinungsjahr
2007
Quelle
MEDLINE
Beschreibungen/Notizen
The SUMO Conjugating Enzyme Ubc9 is a Regulator of GLUT4 Turnover and Targeting to the Insulin-Responsive Storage Compartment
in 3T3-L1 Adipocytes
Li-Bin Liu ,
Waka Omata ,
Itaru Kojima and
Hiroshi Shibata
From the Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
Address correspondence and reprint requests to Hiroshi Shibata, MD, PhD, Department of Cell Biology, Institute for Molecular
and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan. E-mail: hshibata{at}showa.gunma-u.ac.jp
Abstract
The small ubiquitin-related modifier (SUMO) conjugating enzyme Ubc9 has been shown to upregulate GLUT4 in L6 myoblast cells,
although the mechanism of action has remained undefined. Here we investigated the physiological significance of Ubc9 in GLUT4
turnover and subcellular targeting by adenovirus vector–mediated overexpression and by small interfering RNA (siRNA)-mediated
gene silencing of Ubc9 in 3T3-L1 adipocytes. Overexpression of Ubc9 resulted in an inhibition of GLUT4 degradation and promoted
its targeting to the unique insulin-responsive GLUT4 storage compartment (GSC), leading to an increase in GLUT4 amount and
insulin-responsive glucose transport in 3T3-L1 adipocytes. Overexpression of Ubc9 also antagonized GLUT4 downregulation and
its selective loss in GSC induced by long-term insulin stimulation. By contrast, siRNA-mediated depletion of Ubc9 accelerated
GLUT4 degradation and decreased the amount of the transporter, concurrent with its selective loss in GSC, which resulted in
attenuated insulin-responsive glucose transport. Intriguingly, overexpression of the catalytically inactive mutant Ubc9-C93A
produced effects indistinguishable from those with wild-type Ubc9, suggesting that Ubc9 regulates GLUT4 turnover and targeting
to GSC by a mechanism independent of its catalytic activity. Thus, Ubc9 is a pivotal regulator of the insulin sensitivity
of glucose transport in adipocytes.
ALLM, N-acetyl-Leu-Leu-Met-CHO
C/EBP, CCAAT/enhancer-binding protein
CHO, Chinese hamster ovary
CHO-IR, CHO cells expressing the insulin receptor
CHO-IR-GLUT4, CHO cells expressing the insulin receptor and GLUT4
DMEM, Dulbecco's modified Eagle's medium
FBS, fetal bovine serum
GFP, green florescent protein
GSC, GLUT4 storage compartment
IRAP, insulin-regulated aminopeptidase
LDM, low density membrane
M6PR, mannose-6-phosphate receptor
PPAR, peroxisome proliferator–activated receptor
siRNA, small interfering RNA
SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor
SUMO, small ubiquitin-related modifier
TGN, trans-Golgi network
Footnotes
Published ahead of print at http://diabetes.diabetesjournals.org on 29 May 2007. DOI: 10.2337/db06-1100.
L.-B.L. and W.O. contributed equally to this work.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore
be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Accepted May 19, 2007.
Received August 8, 2006.
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