Alterations in the Glycosylation of Secreted Thyrotropin during Ontogenesis

• Published in: The Journal of biological chemistry Vol. 264; no. 11; pp. 6104 - 6110
• Main Authors: Gyves, P W, Gesundheit, N, Stannard, B S, DeCherney, G S, Weintraub, B D
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.04.1989
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)83319-1

We have examined the carbohydrate structure of thyrotropin (TSH) secreted in vitro by pituitaries from prenatal, perinatal, and mature rats using concanavalin A (ConA)-agarose chromatography and anionexchange high performance liquid chromatography (HPLC). [3H]Glucosamine-labeled TSH was immunoprecipitated and treated with either Pronase to generate glycopeptides or a mixture of endo-β-N-acetylglucosaminidase F and peptide:N-glycosidase F to release oligosaccharides. The percentage of secreted TSH glycopeptides not bound to ConA was greater in mature animals (47 ± 3%) than in either prenatal (29 ± 3%) or perinatal animals (29 ±6%), suggesting more multiantennary oligosaccharides in the older animals. These structural changes were characterized further by performing anion-exchange HPLC on released oligosaccharides. Secreted TSH from prenatal rats predominantly contained oligosaccharides with 1 and 2 negative charges, while TSH from mature rats contained these structures as well as 15% with 3 negative charges. In addition, the ratio of sialylated to sulfated oligosaccharides was greater in mature compared to prenatal animals for species with 1 negative charge (1.9-fold) as well as for species with 2 negative charges (4.3-fold). We also correlated the structural alterations noted by ConA analysis with anion-exchange HPLC. Oligosaccharides that bound to ConA and were eluted with a-methylglucoside, when analyzed by anion-exchange HPLC, consisted of species with 1 and 2 negative charges, whereas oligosaccharides that were unbound to ConA were predominantly species with three negative charges. Together, these data suggest that with maturation of the hypothalamic-pituitary-thyroid axis secreted TSH contains more negatively charged multiantennary oligosaccharides with increased sialylation and decreased sulfation.