Plasma cell immunoglobulin M molecules. Their biosynthesis, assembly, and intracellular transport
Plasma cell immunoglobulin M molecules. Their biosynthesis, assembly, and intracellular transport
复制标题
浆细胞免疫球蛋白 M 分子。
DOI：
--
复制
发表时间：
1979
影响因子：
7.8
通讯作者：
Pierre Vassalli
中科院分区：
文献类型：
--
作者：
A. Tartakoff;Pierre Vassalli
分泌免疫球蛋白M（IgM）的鼠浆母细胞已被用于探索细胞内转运（ICT）过程中发生的多肽H和L链（糖基化、链组装和聚合步骤）连续修饰的细胞学位点以及这些事件之间的相互关系。脉冲追踪生物合成标记方案（使用氨基酸和糖）、亚细胞分级分离和电子显微镜放射自显影的组合与糖基化抑制剂和阻断IG离开粗面内质网（RER）或高尔基体池的试剂（羧基氰化物间氯苯腙[CCCP]和莫能菌素）联合使用。这些数据与以下结论一致：（1）糖的添加和修饰发生在三个主要步骤中：（a）将核心糖整体添加到新生H链，（B）在RER中部分修剪这些寡糖链，（c）在莫能菌素敏感的高尔基池和细胞表面之间的非常远的隔室中准集中添加末端糖（半乳糖，岩藻糖和唾液酸）。(2)H和L链组装发生在新生H链和RER中存在的游离轻链库之间，随后是链间二硫键合和单体在RER中快速组装成含J链的五聚体。在聚合反应中也形成少量的各种明显非强制性的中间体。(3)链组装、聚合和分泌不需要添加碳水化合物，因为完全未糖基化的链（在脱氧葡萄糖或衣霉素存在下合成）经历聚合并分泌（尽管速率降低）。(4)表面8s IgM分子不代表IgM分泌途径中的一个步骤。
Immunoglobulin M (IgM)-secreting murine plasmablasts have been used to explore the cytologic site(s) of the successive modifications of the polypeptide H and L chains (steps of glycosylation, chain assembly, and polymerization) which occur during intracellular transport (ICT) and the interrelationships between these events. A combination of pulse- chase biosynthetic labeling protocols (using amino acids and sugars), subcellular fractionation, and electron microscope autoradiography was used in conjunction with inhibitors of glycosylation and agents (carboxyl cyanide m-chlorophenyl hydrazone [CCCP] and monensin) which block Ig exit from the rough endoplasmic reticulum (RER) or Golgi cisternae. The data are consistent with the following conclusions: (1) Sugar addition and modification occur in three main steps: (a) en bloc addition of core sugars to nascent H chains, (b) partial trimming of these oligosaccharide chains in the RER, (c) quasiconcerted addition of terminal sugars (galactose, fucose, and sialic acid) in a very distal compartment between monensin-sensitive Golgi cisternae and the cell surface. (2) H and L chain assembly occurs between nascent H chains and a pool of free light chains present in the RER, followed by interchain disulfide bonding and rapid assembly of monomers into J chain- containing pentamers in the RER. Small amounts of various apparently non-obligatory intermediates in polymerization are also formed. (3) Carbohydrate addition is not required for chain assembly, polymerization, and secretion since completely unglycosylated chains (synthesized in the presence of deoxyglucose or tunicamycin) undergo polymerization and are secreted (although at a reduced rate). (4) Surface 8s IgM molecules do not represent a step in the IgM secretory pathway.