Fra A M, Alberini C, Bet P, Finazzi D, Valetti C, Sitia R
Istituto Scientifico San Raffaele, Milano, Italy.
Ann Biol Clin (Paris). 1991;49(5):283-6.
Cells have means to ensure that only properly folded and assembled molecules are transported to their final destination, a phenomenon referred to as "quality control" of protein synthesis. Thus, plasma cells secrete only the polymeric form of IgM, retaining and degrading intracellularly assembly intermediates. Due to the failure to polymerize secretory IgM, B lymphocytes do not secrete IgM, while they express the membrane form of IgM on their surface. The selective retention of IgM assembly intermediates is due to disulphide interchange reactions which involve the C terminal cysteine of secretory microseconds chains and unknown protein(s) of the endoplasmic reticulum (ER). Assembly inhibits these reactions, as does addition of reducing agents. In the latter condition, assembly intermediates, otherwise retained and degraded in the ER, are transported to the Golgi, glycosylated and secreted. The developmental control of immunoglobulin secretion is discussed in the more general context of "quality control" of newly synthesized protein within the exocytic compartment.
细胞有办法确保只有正确折叠和组装的分子才能被运输到它们的最终目的地，这一现象被称为蛋白质合成的“质量控制”。因此，浆细胞只分泌聚合形式的IgM，将细胞内的组装中间体保留并降解。由于分泌型IgM无法聚合，B淋巴细胞不分泌IgM，而它们在表面表达膜形式的IgM。IgM组装中间体的选择性保留是由于二硫键交换反应，该反应涉及分泌型微秒链的C末端半胱氨酸和内质网（ER）的未知蛋白质。组装会抑制这些反应，添加还原剂也会抑制。在后一种情况下，原本在内质网中保留并降解的组装中间体被运输到高尔基体，进行糖基化并分泌。免疫球蛋白分泌的发育控制将在胞吐区室中新合成蛋白质“质量控制”的更一般背景下进行讨论。
