Document Detail


Glycosylation of thyroid-stimulating hormone in pituitary tumor cells: influence of high mannose oligosaccharide units on subunit aggregation, combination, and intracellular degradation.
MedLine Citation:
PMID:  6403327     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We have studied the glycosylation of TSH in cell culture and have examined the influence of carbohydrate on subunit aggregation, intracellular degradation, and combination. Dispersed mouse thyrotropic tumor cells were labeled by pulse-chase methods with [35S]methionine and various 3H-labeled carbohydrates; cell lysates and media were precipitated with antisera to TSH alpha and TSH beta, and the products were analyzed by sodium dodecyl sulfate gradient gel electrophoresis without or with preexposure to Endoglycosidase (Endo) H. At early pulses, both intracellular alpha and beta were mainly composed of one Endo H-sensitive (high mannose) carbohydrate unit and a small amount of nonglycosylated forms; alpha only had the posttranslational addition of a second high mannose unit. With increasing chase times up to 18 h, intracellular subunits showed a slow but progressive increase in Endo H-resistant (complex) forms, and media subunits were completely resistant. Preincubation of cells with tunicamycin caused production of nonglycosylated subunits that showed a high degree of aggregation, especially after heating at 37 C under nonreducing conditions. Unlike glycosylated subunits, which were not degraded, nonglycosylated subunits were 50-65% degraded intracellularly before secretion; the degradation caused by tunicamycin was specific for TSH subunits and not noted for other 35S-labeled proteins. Incubation of various 35S-labeled alpha forms with excess unlabeled TSH beta showed high combining activity for intracellular alpha with two high mannose units, intermediate activity for media alpha with two complex units, and low activity for intracellular alpha with one high mannose unit or nonglycosylated media alpha. These data suggest that the initial glycosylation with high mannose carbohydrate units prevents intracellular aggregation and degradation of TSH subunits and enhances attainment of the conformation necessary for alpha- and beta-subunit combination.
Authors:
B D Weintraub; B S Stannard; L Meyers
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Endocrinology     Volume:  112     ISSN:  0013-7227     ISO Abbreviation:  Endocrinology     Publication Date:  1983 Apr 
Date Detail:
Created Date:  1983-05-05     Completed Date:  1983-05-05     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1331-45     Citation Subset:  AIM; IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Electrophoresis, Polyacrylamide Gel
Female
Glycoside Hydrolases / metabolism
Macromolecular Substances
Mannose / metabolism*
Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase
Mice
Molecular Weight
Oligosaccharides / metabolism*
Thyrotropin / metabolism*
Tunicamycin / pharmacology
Chemical
Reg. No./Substance:
0/Macromolecular Substances; 0/Oligosaccharides; 11089-65-9/Tunicamycin; 31103-86-3/Mannose; 9002-71-5/Thyrotropin; EC 3.2.1.-/Glycoside Hydrolases; EC 3.2.1.96/Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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