Evidence for a glycoprotein "signal" involved in transport between subcellular organelles. Two membrane glycoproteins encoded by murine leukemia virus reach the cell surface at different rates.
Evidence for a glycoprotein "signal" involved in transport between subcellular organelles. Two membrane glycoproteins encoded by murine leukemia virus reach the cell surface at different rates.
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DOI：
10.1016/s0021-9258(19)45335-0
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发表时间：
1982-12
期刊：
影响因子：
--
通讯作者：
T. Fitting;D. Kabat
中科院分区：
文献类型：
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作者：
T. Fitting;D. Kabat
我们分析了由小鼠白血病病毒编码的两种质膜糖蛋白的合成和细胞内转运，一种是表观M（r）= 70，000的env基因编码的糖蛋白（gp 70（env）），另一种是表观M（r）= 93，000的gag基因编码的糖蛋白（gp 93（gag））。这些糖蛋白通过细胞外抗体吸附技术从感染细胞的表面特异性分离，其中蛋白质用L-[35 S]甲硫氨酸脉冲标记，并且可以动力学研究它们在质膜中的到达和周转（Krangel，MS，Orr，HT，and Strominger，JL（1979）Cell 18，979-991）。此外，这些糖蛋白的前体和产物形式进行了分析，在全细胞裂解液中，在分级膜亚细胞器，并在释放的病毒体。而gp 93（gag）在L-[35 S]甲硫氨酸掺入60 min内定量转移到质膜中，gp 70（env）在那时仅部分转移，并且在210分钟后仍在质膜中积累。这种差异是由gp 70（env）加工中的缓慢步骤引起的，该步骤似乎发生在粗面内质网中，并且在粗面内质网之前（在几分钟内）或与较大的糖蛋白前体gPr 90（env）的部分蛋白水解裂解一致。一旦越过该动力学屏障，gp 70（env）在15分钟内通过高尔基体快速加工至质膜。env基因编码的糖蛋白从前体库通过动力学屏障的转移是随机发生的，而不是以蛋白质合成的线性或队列顺序发生的。gp 93（gag）和gp 70（env）转运动力学之间的差异表明，细胞内转运是一个选择性的，而不是被动的流动过程，膜糖蛋白的结构特征（信号）决定其转移速率。转运系统的这些特征，以及其在池中花费的时间的随机性，支持一个简单的模型：转运需要与分子结合，这些分子与具有不同亲和力的不同糖蛋白相互作用。某些糖蛋白的结合亲和力可以通过共价改变如部分蛋白水解或糖基化来调节。
We analyzed the synthesis and intracellular transport of two plasma membrane glycoproteins encoded by murine leukemia virus, an env gene-encoded glycoprotein with an apparent M (r)= 70,000 (gp70 (env)) and a gag gene-encoded glycoprotein with an apparent M (r)= 93,000 (gp93 (gag)). These glycoproteins were specifically isolated from the surfaces of infected cells by an extracellular antibody adsorption technique in which proteins are pulse labeled with L-[35 S] methionine and their arrival and turnover in plasma membranes can be kinetically studied (Krangel, MS, Orr, HT, and Strominger, JL (1979) Cell 18, 979-991). In addition, precursor and product forms of these glycoproteins were analyzed in whole cell lysates, in fractionated membranous subcellular organelles, and in released virions. Whereas gp93 (gag) is transferred quantitatively into plasma membranes within 60 min of L-[35 S] methionine incorporation, gp70 (env) is only partially transferred at that time and is still accumulating in plasma membranes after 210 min. This difference is caused by a slow step in gp70 (env) processing which appears to occur in the rough endoplasmic reticulum and which precedes (within several minutes) or coincides with partial proteolytic cleavage of a larger glycoprotein precursor gPr90 (env). Once past this kinetic barrier, gp70 (env) is rapidly processed within 15 min via the Golgi apparatus to the plasma membranes. Transfer of env gene-encoded glycoproteins past the kinetic barrier from the precursor pool occurs randomly rather than in the linear or cohort order in which the proteins were synthesized. The differences between gp93 (gag) and gp70 (env) transport kinetics indicate that intracellular transport is a selective rather than passive flow process and that structural characteristics (signals) of membrane glycoproteins determine their rates of transfer. These characteristics of the transport system, and its randomness with respect to time spent in the pool, support a simple model: that transport requires binding to molecule (s) which interact with different glycoproteins with distinct affinities. Binding affinities of certain glycoproteins may be modulated by covalent alterations such as partial proteolysis or glycosylation.