Stimulation of glucose transporter (GLUT1) mRNA and protein expression by inhibitors of glycosylation.
Glucose deprivation increases the steady-state levels of mRNA for the rat brain/HepG2-type glucose transporter (GLUT1) in L6 myocytes. Glucose deprivation also inhibits N-linked glycosylation. We therefore investigated a possible relationship between inhibition of glycosylation and GLUT1 expression in cultured L6 myocytes by determining the effects on GLUT1 expression of known inhibitors of glycosylation, namely tunicamycin, 2-deoxyglucose and glucosamine. All conditions prevented incorporation of [3H]mannose into TCA-precipitable myocyte protein and resulted in a 2- to 5-fold increase in the level of GLUT1 mRNA detected on Northern blots. Glucose deprivation and tunicamycin treatment caused an approx. 2-fold increase in GLUT1 mRNA half-life. GLUT1 protein, detected on immunoblots, accumulated 10- to 20-fold in response to all glycosylation inhibitors, with apparent molecular masses of 40 kDa after glucose deprivation, 42 kDa after 2-deoxyglucose and 38 kDa after glucosamine or tunicamycin treatments, compared to 45-50 kDa in glucose-fed cells. However, glucose deprivation was the only condition in which the rate of 2-deoxy-[3H]glucose uptake increased (3- to 5-fold). These results demonstrate a direct correlation between inhibition of glycosylation and the induction of GLUT1 mRNA and protein expression and suggest that the stability of GLUT1 mRNA is controlled by a signal associated with glycosylation.
Maher
F
F
Burnet Clinical Research Unit, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.
Harrison
L C
LC
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D003847:Deoxyglucose / Q000378:metabolism / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D005944:Glucosamine / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism / Q000502:physiology; D006023:Glycoproteins / Q000096:biosynthesis; D006031:Glycosylation / Q000187:drug effects; D015151:Immunoblotting; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis* / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis*; D014415:Tunicamycin / Q000494:pharmacology
D006023:Glycoproteins; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D014415:Tunicamycin; D003847:Deoxyglucose; D005947:Glucose; D005944:Glucosamine