Folding of insulin receptor monomers is facilitated by the molecular chaperones calnexin and calreticulin and impaired by rapid dimerization.
Folding of insulin receptor monomers is facilitated by the molecular chaperones calnexin and calreticulin and impaired by rapid dimerization.
复制标题
DOI：
10.1083/jcb.141.3.637
复制
发表时间：
1998-05-04
影响因子：
7.8
通讯作者：
Steiner, DF
中科院分区：
文献类型：
--
作者：
Bass, J;Chiu, G;Argon, Y;Steiner, DF
许多复杂的膜蛋白在转运到细胞表面之前在ER中经历亚基折叠和组装。胰岛素和胰岛素样生长因子I的受体，都是整合的膜蛋白和受体酪氨酸激酶（RTK）家族的成员，是不寻常的，因为它们在从ER输出之前需要同源二聚化。为了更好地了解分子伴侣机制在活细胞中的内源性膜蛋白组装，我们已经研究了折叠，组装和运输的人胰岛素受体（HIR），二聚体RTK。利用脉冲追踪标记和非还原SDS-PAGE分析，我们探索了受体生物合成过程中几个连续成熟步骤的分子基础。在正常生长条件下，新合成的受体单体经历二硫键形成，同时与同源伴侣钙连接蛋白（Cnx）和钙网蛋白（Crt）相关。葡萄糖微调抑制剂栗精胺（CST）消除了与Cnx/Crt的结合，但也意外地加速了受体同源二聚化，导致错误折叠的寡聚前受体，其加工被延迟，并且细胞表面表达也降低了约30%。未成熟二聚化受体保留在ER中，并且更积极地与70 kD同源物结合蛋白的热休克蛋白相关。在CST处理的细胞中，受体错误折叠后无序寡聚化。总之，这些研究证明了Cnx/Crt在体内HIR折叠中的分子伴侣功能，并且还提供了折叠效率和同源二聚化平衡的证据。
Many complex membrane proteins undergo subunit folding and assembly in the ER before transport to the cell surface. Receptors for insulin and insulin-like growth factor I, both integral membrane proteins and members of the family of receptor tyrosine kinases (RTKs), are unusual in that they require homodimerization before export from the ER. To better understand chaperone mechanisms in endogenous membrane protein assembly in living cells, we have examined the folding, assembly, and transport of the human insulin receptor (HIR), a dimeric RTK. Using pulse-chase labeling and nonreducing SDS-PAGE analysis, we have explored the molecular basis of several sequential maturation steps during receptor biosynthesis. Under normal growth conditions, newly synthesized receptor monomers undergo disulfide bond formation while associated with the homologous chaperones calnexin (Cnx) and calreticulin (Crt). An inhibitor of glucose trimming, castanospermine (CST), abolished binding to Cnx/Crt but also unexpectedly accelerated receptor homodimerization resulting in misfolded oligomeric proreceptors whose processing was delayed and cell surface expression was also decreased by ∼30%. Prematurely-dimerized receptors were retained in the ER and more avidly associated with the heat shock protein of 70 kD homologue binding protein. In CST-treated cells, receptor misfolding followed disordered oligomerization. Together, these studies demonstrate a chaperone function for Cnx/Crt in HIR folding in vivo and also provide evidence that folding efficiency and homodimerization are counterbalanced.
登录
查看更多内容
影响因子：
19
作者：
Helenius, Ari;Marquardt, Thorsten;Braakman, Ineke
通讯作者：
Braakman, Ineke
影响因子：
4.8
作者：
Isidoro, C;Maggioni, C;Sitia, R
通讯作者：
Sitia, R
影响因子：
64.5
作者：
HEBERT, DN;FOELLMER, B;HELENIUS, A
通讯作者：
HELENIUS, A
影响因子：
11.4
作者：
MOLLOY, SS;THOMAS, L;THOMAS, G
通讯作者：
THOMAS, G
影响因子：
7.8
作者：
LODISH, HF;KONG, N
通讯作者：
KONG, N