Stannard B S, Gesundheit N, Thotakura N R, Gyves P W, Ronin C, Weintraub B D
Molecular, Cellular and Nutritional Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892.
Biochem Biophys Res Commun. 1989 Dec 15;165(2):788-94. doi: 10.1016/s0006-291x(89)80035-x.
We examined the effect of various inhibitors of oligosaccharide processing on the content and secretion of newly synthesized thyroid-stimulating hormone (TSH) from dispersed hypothyroid rodent pituitary cells. 1-deoxynojirimycin and N-methyl-1-deoxynojirimycin, both inhibitors of glucosidases I and II, decreased intracellular TSH (to 60-76% of control) and secreted TSH (to 60-63% of control) after a 1-hour incubation (pulse) with [35S]methionine and an 8-hour incubation (chase) in isotope-free media. In contrast, deoxymannojirimycin and swainsonine, inhibitors of mannosidase I and II, respectively, increased both intracellular TSH (to 267-309% of control) and secreted TSH (to 192% of control) at 8 hours. TSH oligosaccharides synthesized in the presence of these glucosidase and mannosidase inhibitors were largely sensitive to endo-beta-N-acetylglucosaminidase H (endo H), confirming inhibition of processing. Despite differences in oligosaccharide structure, the in vitro bioactivities of these secreted TSH isoforms were nearly identical. These data confirm and extend previous work performed with 1-deoxynojirimycin suggesting that glucosylated high mannose forms of TSH are more susceptible to intracellular degradation. The novel finding that deoxymannojirimycin and swainsonine increase secreted and total TSH above control levels suggests that non-glucosylated high mannose forms as well as hybrid-type oligosaccharides may facilitate secretion and direct TSH away from a natural degradation pathway.
我们研究了多种寡糖加工抑制剂对来自甲状腺功能减退啮齿动物垂体分散细胞新合成的促甲状腺激素（TSH）含量和分泌的影响。1-脱氧野尻霉素和N-甲基-1-脱氧野尻霉素，这两种葡糖苷酶I和II的抑制剂，在与[35S]甲硫氨酸孵育1小时（脉冲）并在无同位素培养基中孵育8小时（追踪）后，降低了细胞内TSH（降至对照的60 - 76%）和分泌的TSH（降至对照的60 - 63%）。相比之下，分别作为甘露糖苷酶I和II抑制剂的脱氧甘露野尻霉素和苦马豆素，在8小时时增加了细胞内TSH（增至对照的267 - 309%）和分泌的TSH（增至对照的192%）。在这些葡糖苷酶和甘露糖苷酶抑制剂存在下合成的TSH寡糖对内切β-N-乙酰葡糖胺糖苷酶H（内切H）大多敏感，证实了加工过程受到抑制。尽管寡糖结构存在差异，但这些分泌的TSH同工型的体外生物活性几乎相同。这些数据证实并扩展了先前用1-脱氧野尻霉素进行的研究工作，表明糖基化的高甘露糖形式的TSH更容易受到细胞内降解的影响。脱氧甘露野尻霉素和苦马豆素使分泌的和总的TSH高于对照水平这一新发现表明，非糖基化的高甘露糖形式以及杂合型寡糖可能促进分泌并使TSH偏离自然降解途径。
