Increased expression of N-acetylglucosaminyltransferase-V in human hepatoma cells by retinoic acid and 1alpha,25-dihydroxyvitamin D3.
UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6N-acetylglucosaminyltransferase-V activities were determined in human hepatoma cell lines of Hep3B and HepG2, and also compared with those of normal liver tissues and primary hepatocytes. When GlcNAcbeta1-2Manalpha1-3(GlcNAcbeta1-2Manalpha1-4)(Manbeta1-4GlcNAc-2-amino pyridine (GlcN,GlcN-biant-PA) and UDP-GlcNAc were used as substrates, the enzymes displayed optimum temperatures of 50 degrees C, optimum pHs of 6.5 in each case, K(m) values for UDP-GlcNAc to be 5.8 (Hep3B) and 4.5 mM (HepG2) and K(m) values for GlcN,GlcN-biant-PA (mM) to be 1.28 (Hep3B) and 2.4 (HepG2). This indicates that values of Hep3B GlcNAc-transferase-V were distinguishable with HepG2 enzyme. Furthermore, Hep3B enzyme in membrane fraction showed about 1.5-fold higher specific activity (1.423 pmol/(h mg) than that (1.066 pmol/(h mg)) of HepG2. Normal hepatocytes are characterized by very low level of GlcNAc-transferase-V activity whereas hepatoma cells contained high activities. Treatment of hepatoma cells with retinoic acid and 1alpha,2,5-dihydroxyvitamin D(3) (Vit-D(3)) resulted in an increase in GlcNAc-transferase-V activity, while treatment with dimethyl sulfoxide and cytosine-arabinoside resulted in decrease in the enzyme activity. Although retinoic acid (RA) treated cells shows a changed GlcNAc-transferase-V mRNA expression, expression of marker proteins such as alpha-fetoprotein and albumin was not changed. This is the first demonstration of GlcNAc-transferase-V activity in RA and Vit-D(3)-treated hepatoma cell lines.
National Research Laboratory for Glycobiology, Korean Ministry of Science and Technology, Kyungju, Kyungbuk 780-714, South Korea. chkimbio@dongguk.ac.kr
Cheorl-Ho
CH
Kim
D000418:Albumins / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology*; D003561:Cytarabine / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology*; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism*; D011725:Pyridines / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*
D000418:Albumins; D011725:Pyridines; D003561:Cytarabine; D014212:Tretinoin; D017351:N-Acetylglucosaminyltransferases; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase; D002117:Calcitriol; D004121:Dimethyl Sulfoxide