Lutropin molecules synthesized by rat gonadotroph primary cultures in the presence of swainsonine: their oligosaccharides and biological potencies.
The biosynthesis of lutropin (luteinizing hormone, LH) containing abnormally processed oligosaccharides has been studied in rat gonadotroph-enriched primary culture in the presence of swainsonine, an inhibitor of the N-linked oligosaccharide processing in the Golgi complex. The inhibitor led to time- and dose-dependent accumulation of highly alkaline LH molecules (pI 9.6, 10.0) with high binding affinity for concanavalin A (ConA), and concomitant decreases of less alkaline components (pI 8.0, 8.5, 8.8) with less affinity for the lectin. The accumulation of LH molecules was much amplified after gonadotrophin-releasing hormone (GnRH) stimulation. The characterization of the oligosaccharide structure performed by means of enzyme treatment and serial chromatography on immobilized ConA, Ricinin communis agglutinin-120 (RCA-120), and wheat germ agglutinin (WGA) showed that swainsonine-induced LH contained principally the hybrid-type oligosaccharide, which was processed by the addition of terminal sialic acid residues on one branch of each N-linked oligosaccharide in both subunits. Small amounts of LH molecules containing asialo or partially sialylated hybrid oligosaccharides were also synthesized. The data for in vitro steroidogenic activities of swainsonine-induced LH indicated that terminal sialic acid on one branch of the hybrid-type oligosaccharides decreased the full agonist activity by approximately 50%.
D000118:Acetylglucosaminidase / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D037102:Lectins / Q000378:metabolism; D007985:Leydig Cells / Q000378:metabolism; D007986:Luteinizing Hormone / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D008361:Mannosidases / Q000037:antagonists & inhibitors; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D009844:Oligosaccharides / Q000096:biosynthesis / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology; D037121:Plant Lectins; D051381:Rats; D011919:Rats, Inbred Strains; D012685:Sepharose; D017026:Swainsonine; D013739:Testosterone / Q000378:metabolism; D013997:Time Factors; D014909:Wheat Germ Agglutinins / Q000378:metabolism
D000470:Alkaloids; D037102:Lectins; D009844:Oligosaccharides; D010906:Pituitary Hormone-Releasing Hormones; D037121:Plant Lectins; C017707:Ricinus communis agglutinin-1; D014909:Wheat Germ Agglutinins; D013739:Testosterone; D007986:Luteinizing Hormone; D012685:Sepharose; D008361:Mannosidases; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D017026:Swainsonine