Proliferative and nutritional dependent regulation of glyceraldehyde-3-phosphate dehydrogenase expression in the rat liver.
Glyceraldehyde-3-phosphate dehydrogenase is a multifunctional protein possessing numerous cytoplasmic and nuclear functions associated with cellular proliferation. Despite the emerging role of glyceraldehyde-3-phosphate dehydrogenase in regulating the proliferative process, there is a paucity of data regarding its expression and intracellular distribution in non-malignant proliferating hepatocytes. Thus the aim of the present study was to document the intracellular distribution of glyceraldehyde-3-phosphate dehydrogenase protein in proliferating hepatocytes derived from regenerating rat livers, and glyceraldehyde-3-phosphate dehydrogenase gene expression in fasted and re-fed rats following partial hepatectomy (PHx). Glyceraldehyde-3-phosphate dehydrogenase mRNA and protein expression were documented by Northern and Western blot analyses, respectively, at various times following 70% PHx in adult Sprague-Dawley rats. At 24 h post-surgery, glyceraldehyde-3-phosphate dehydrogenase mRNA expression was significantly increased in both PHx and sham operated rats (P < 0.001), respectively. Despite the increase in glyceraldehyde-3-phosphate dehydrogenase mRNA expression in both groups, only PHx rats had a significant increase in the nuclear fraction of glyceraldehyde-3-phosphate dehydrogenase protein (threefold increase compared to sham and baseline levels, P < 0.01), cytoplasmic levels of glyceraldehyde-3-phosphate dehydrogenase protein remained unaltered in both groups. In terms of the effects of feeding and fasting on rats there were no significant differences in glyceraldehyde-3-phosphate dehydrogenase mRNA levels, whether fasted or refed, in rats that had undergone PHx, 8 h earlier. On the other hand, glyceraldehyde-3-phosphate dehydrogenase mRNA levels were significantly increased in refed compared to fasted sham operated rats 8 h following surgery. Serum insulin concentrations were higher in the refed PHx and sham groups compared to their fasted counterparts. The results of this study indicate that although glyceraldehyde-3-phosphate dehydrogenase mRNA are altered to the same extent in PHx and sham-operated rats following surgery, increases in the nuclear fraction of glyceraldehyde-3-phosphate dehydrogenase protein only occur in PHx rats. The results also indicate that glyceraldehyde-3-phosphate dehydrogenase expression is affected by the nutritional status of animals undergoing abdominal sham surgery.
Corbin
I R
IR
Liver Diseases Unit, Department of Medicine & Pharmacology, University of Manitoba, Winnipeg, Canada.
Gong
Y
Y
Zhang
M
M
Minuk
G Y
GY
D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000201:enzymology; D005215:Fasting; D005786:Gene Expression Regulation; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000096:biosynthesis* / Q000235:genetics; D022781:Hepatocytes / Q000201:enzymology; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008103:Liver Cirrhosis / Q000201:enzymology; D008115:Liver Regeneration; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley
D012333:RNA, Messenger; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases