Effects of homoharringtonine on protein glycosylation in human bladder carcinoma cell T-24.
Rates of [3H]glucosamine and mannose incorporation into glycoproteins and dolichol-linked oligosaccharides in exponentially growing T-24 bladder cancer cells were examined after exposure to homoharringtonine (HHT). Two-h treatment of HHT (10 ng/ml) reduced [3H]glucosamine and mannose incorporation into the glycoproteins to 61% and 32% of controls. Concomitantly, respective sugar incorporation into dolichol-linked oligosaccharides was elevated 29% and 30% above control. The maximal inhibition of glycoprotein biosynthesis and stimulation of the lipid-linked oligosaccharides occurred within 2 to 4 h after exposure to 50 ng/ml of the drug. Prolonged drug exposure (greater than 8 h) resulted in generalized suppression of glycoprotein biosynthesis and lipid-linked oligosaccharide formation. The kinetic study indicated that the time course on reduction of glycoprotein biosynthesis and accumulation of dolichol-linked oligosaccharides paralleled the decline in protein synthesis. Further, the inhibition of glycoprotein synthesis and stimulation of dolichol-linked oligosaccharides were reversible 4 h after drug withdrawal. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis autoradiographic analysis of the [3H]mannose-labeled glycoprotein revealed no pronounced difference between HHT-treated and control cells. These data suggest that the inhibition of glycosylation results from combined decrease of acceptors for glycoprotein biosynthesis with a simultaneous accumulation of the dolichol-linked oligosaccharides. Collectively these data may account for many of the HHT-induced bioresponses.
Ling
Y H
YH
Department of Surgery, University of Louisville, Kentucky 40292.
Tseng
M T
MT
Harty
J I
JI
D000470:Alkaloids / Q000494:pharmacology*; D002295:Carcinoma, Transitional Cell / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D003520:Cyclophosphamide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000096:biosynthesis; D006031:Glycosylation; D006248:Harringtonines / Q000494:pharmacology*; D000077863:Homoharringtonine; D006801:Humans; D011506:Proteins / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014415:Tunicamycin / Q000494:pharmacology; D001749:Urinary Bladder Neoplasms / Q000378:metabolism*
D000470:Alkaloids; D006023:Glycoproteins; D006248:Harringtonines; D011506:Proteins; D014415:Tunicamycin; D000077863:Homoharringtonine; D003520:Cyclophosphamide