Differential processing and regulation of thyroid-stimulating hormone subunit carbohydrate chains in thyrotropic tumors and in normal and hypothyroid pituitaries

• Published in: Biochemistry (Easton) Vol. 24; no. 20; pp. 5626 - 5631
• Main Authors: Ronin, Catherine, Stannard, Bethel S, Weintraub, Bruce D
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.09.1985
• Subjects: Animals; Applied sciences; Biological and medical sciences; Endocrinopathies; Exact sciences and technology; Female; Galactose - metabolism; Hypothyroidism - metabolism; Macromolecular Substances; Male; Mannose - metabolism; Medical sciences; Mice; Mice, Inbred Strains; Oligosaccharides - biosynthesis; Other techniques and industries; Pituitary Gland - metabolism; Pituitary Neoplasms - metabolism; Protein Processing, Post-Translational; Rats; Rats, Inbred Strains; Reference Values; Thyroid. Thyroid axis (diseases); Thyrotropin - genetics; Tritium; Endocrinopathy; Human; TSH-RH; Secretory tumor; Molecular processing; Pituitary gland; Hypothyroidism
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00341a051

Thyroid-stimulating hormone (TSH) alpha- and beta-subunit glycosylation was investigated in mouse thyrotropic tumor and in normal and hypothyroid pituitary cells for various periods of time in the presence of [3H]mannose or [3H]galactose. After sequential precipitation with anti-alpha and anti-beta sera, subunits were treated with Pronase followed by endo-beta-N-acetylglucosaminidase H (Endo H) and analyzed by paper chromatography. In primary cultures of thyrotropic tumor cells incubated for 60 min with [3H]mannose, primarily Man9GlcNAc and Man8GlcNAc were found on TSH + alpha subunits, whereas Glc1Man9GlcNAc and Man9GlcNAc were prominent on free beta subunits. After preincubation of cells for 16 h in the presence or absence of glucose followed by a 60-min pulse of [3H]mannose, there was an 8-fold increase in labeled TSH + alpha but only a minimal change in free beta or total proteins. In the absence of glucose, there was a selective accumulation of Man8GlcNAc on TSH + alpha but not on free beta or total proteins; however, there was no detectable accumulation of Endo H resistant forms during glucose starvation on TSH subunits or total proteins. Normal mouse and rat pituitary minces incubated for 60 min with either [3H]mannose or [3H]galactose showed no glucose-containing species on TSH subunits, but equal amounts of Man9GlcNAc and Man8GlcNAc on TSH + alpha, and mostly Man9GlcNAc on free beta subunits. In contrast, hypothyroid mouse and rat pituitaries exhibited an increase in Glc1Man9NAc and Glc1Man8GlcNAc on free beta but not on TSH + alpha or total proteins.