Glycogen: a carbohydrate source for GLUT-1 glycosylation during glucose deprivation of 3T3-L1 adipocytes.
In 3T3-L1 adipocytes, the glycosylation of the GLUT-1 transporter is altered beyond 12 h of glucose deprivation. To determine whether glycogen degradation provides substrate for normal protein glycosylation during this delay, we measured the glycogen content of 3T3-L1 adipocytes. From an initial value of 0.537 +/- 0.097 mumol glucose/10(6) cells, glycogen was depleted in a time-dependent manner in response to glucose deprivation, exhibiting a half-time of 6 h. Surprisingly, fructose did not prevent glycogen depletion. However, in such glycogen-depleted adipocytes, the alteration of GLUT-1 glycosylation in response to glucose deprivation was more rapid than in normal adipocytes. Chinese hamster ovary (CHO) cells, which synthesize abbreviated dolichol-linked oligosaccharides within minutes of glucose deprivation (J. I. Rearick, A. Chapman, and S. Kornfeld. J. Biol. Chem. 256: 6255-6261, 1981), contained only 1% of the level of glycogen found in 3T3-L1 adipocytes. Glycosylation of GLUT-1 was altered in CHO cells within 3 h of glucose deprivation. These data demonstrate that, during glucose stress, glycogen may serve as a buffer for oligosaccharide biosynthesis and provide a potential explanation for varying sensitivities of different cell types to glucose deprivation.
McMahon
R J
RJ
Department of Biochemistry and Molecular Biology, University of Florida, Gainesville 32610, USA.
Frost
S C
SC
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D050260:Carbohydrate Metabolism; D006224:Cricetinae; D005632:Fructose / Q000494:pharmacology; D005947:Glucose / Q000172:deficiency*; D051272:Glucose Transporter Type 1; D006003:Glycogen / Q000172:deficiency / Q000378:metabolism*; D006031:Glycosylation / Q000187:drug effects; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*
D051272:Glucose Transporter Type 1; D009004:Monosaccharide Transport Proteins; C495678:Slc2a1 protein, mouse; D005632:Fructose; D006003:Glycogen; D005947:Glucose