Heifetz A, Snyder J M
J Biol Chem. 1981 May 25;256(10):4957-67.
In order to study the regulation of sulfated glycoconjugate biosynthesis during human fetal lung development, an in vitro organ culture system was utilized. Tissue explants of human fetal lung maintained in organ culture undergo hydrocortisone-potentiated morphological differentiation. Human fetal lung tissue synthesized several classes of sulfated glycoconjugates, including sulfated glycosaminoglycans, sulfated lipids, and a class of glycoproteins containing sulfated oligosaccharide chains. These sulfated oligosaccharides were not released from the polypeptides under alkaline conditions that cleave O-glycosidically linked chains and were not degraded by a variety of chemical and enzymatic treatments which degraded sulfated glycosaminoglycans. Explants maintained in culture during a 6-day period incorporated increasing levels of 35SO4 into glycoconjugates with increases of 7-fold into heparin and heparan sulfate, 3-fold into sulfated glycoproteins, and 2-fold into sulfated lipids. In comparison, incorporation of [3H]mannose into glycoconjugates increased 4-fold, and the incorporation of [3H]thymidine into DNA increased 2- to 3-fold during this culture period. Tissues maintained in culture in the presence of hydrocortisone (10(-7) M) showed an enhanced incorporation of 35SO4 into heparin and heparan sulfate and into sulfated glycoproteins during the culture period compared to cultures maintained in the absence of hydrocortisone. However, the levels of 35SO4 incorporated into lipids, [3H]mannose incorporated into glycoproteins, and [3H]thymidine incorporated into DNA were markedly decreased in cultures maintained in the presence of 10(-7) M hydrocortisone. Only small differences in the synthesis of chondroitin sulfates and dermatan sulfate were observed during the 6-day period that lung tissues were maintained in culture in the presence or absence of hydrocortisone. Thus, the biosynthesis of specific sulfated glycoconjugates by human fetal lung tissues is probably regulated by both developmental events and by circulating steroids.
为了研究人类胎儿肺发育过程中硫酸化糖缀合物生物合成的调控机制，采用了体外器官培养系统。在器官培养中维持的人胎儿肺组织外植体经历了氢化可的松增强的形态分化。人胎儿肺组织合成了几类硫酸化糖缀合物，包括硫酸化糖胺聚糖、硫酸化脂质以及一类含有硫酸化寡糖链的糖蛋白。这些硫酸化寡糖在碱性条件下不会从多肽上释放出来，因为碱性条件会切断O-糖苷键连接的链，并且它们也不会被多种降解硫酸化糖胺聚糖的化学和酶处理所降解。在6天的培养期内，培养的外植体将越来越多的35SO4掺入糖缀合物中，其中肝素和硫酸乙酰肝素增加了7倍，硫酸化糖蛋白增加了3倍，硫酸化脂质增加了2倍。相比之下，在此培养期内，[3H]甘露糖掺入糖缀合物增加了4倍，[3H]胸腺嘧啶掺入DNA增加了2至3倍。与无氢化可的松培养的组织相比，在氢化可的松（10(-7) M）存在下培养的组织在培养期内显示出35SO4掺入肝素、硫酸乙酰肝素和硫酸化糖蛋白的量增加。然而，在10(-7) M氢化可的松存在下培养的组织中，掺入脂质的35SO4水平、掺入糖蛋白的[3H]甘露糖水平以及掺入DNA的[3H]胸腺嘧啶水平均显著降低。在有或无氢化可的松存在的情况下，肺组织在培养6天期间，硫酸软骨素和硫酸皮肤素的合成仅观察到微小差异。因此，人胎儿肺组织中特定硫酸化糖缀合物的生物合成可能受发育事件和循环类固醇的共同调控。
