Effect of alpha-D-mannopyranosylmethyl-p-nitrophenyltriazene on hepatic degradation and processing of the N-linked oligosaccharide chains of alpha 1-acid glycoprotein.
The effects of alpha-D-mannopyranosylmethyl-p-nitrophenyltriazene (alpha-ManMNT) on the degradation and biosynthesis of oligosaccharide chains on alpha 1-acid glycoprotein (AGP) were studied. Addition of the triazene to a perfused liver prevented the complete degradation of endocytosed N-acetyl[14C]glucosamine-labeled asialo-AGP and caused the accumulation of Man2GlcNAc1 fragments in the lysosome-enriched fraction of the liver homogenate. This compound also reduced the reincorporation of lysosomally derived [14C]GlcNAc into newly secreted glycoproteins. Cultured hepatocytes treated with the inhibitor synthesized and secreted fully glycosylated AGP. However, the N-linked oligosaccharide chains on AGP secreted by the alpha-ManMNT-treated hepatocytes remained sensitive to digestion with endoglycosidase H, were resistant to neuraminidase, and consisted of Man9-7GlcNAc2 structures as analyzed by high resolution Bio-Gel P-4 chromatography. As measured by their resistance to cleavage by endoglycosidase H, the normal processing of all six carbohydrate chains on AGP to the complex form did not completely resume until nearly 24 h after triazene treatment. Since alpha-ManMNT is likely to irreversibly inactivate alpha-D-mannosidases, the return of normal AGP secretory forms after 24 h probably resulted from synthesis of new processing enzymes.
Docherty
P A
PA
Kuranda
M J
MJ
Aronson
N N
NN
BeMiller
J N
JN
Myers
R W
RW
Bohn
J A
JA
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002850:Chromatography, Gel; D006026:Glycoside Hydrolases / Q000378:metabolism; D006596:Hexosaminidases / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009439:Neuraminidase / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism*; D009961:Orosomucoid / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D017026:Swainsonine; D014226:Triazenes / Q000494:pharmacology*
D000470:Alkaloids; D009844:Oligosaccharides; D009961:Orosomucoid; D014226:Triazenes; C047982:mannopyranosylmethyl-4-nitrophenyltriazene; D006026:Glycoside Hydrolases; D006596:Hexosaminidases; D009439:Neuraminidase; D017026:Swainsonine