Differential processing and regulation of thyroid-stimulating hormone subunit carbohydrate chains in thyrotropic tumors and in normal and hypothyroid pituitaries.
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.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D005260:Female; D005690:Galactose / Q000378:metabolism; D007037:Hypothyroidism / Q000378:metabolism*; D046911:Macromolecular Substances; D008297:Male; D008358:Mannose / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D009844:Oligosaccharides / Q000096:biosynthesis; D010902:Pituitary Gland / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013972:Thyrotropin / Q000235:genetics*; D014316:Tritium
D046911:Macromolecular Substances; D009844:Oligosaccharides; D014316:Tritium; D013972:Thyrotropin; D008358:Mannose; D005690:Galactose