Separate roles and different routing of calnexin and ERp57 in endoplasmic reticulum quality control revealed by interactions with asialoglycoprotein receptor chains
Separate roles and different routing of calnexin and ERp57 in endoplasmic reticulum quality control revealed by interactions with asialoglycoprotein receptor chains
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DOI：
10.1091/mbc.e03-12-0899
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发表时间：
2004-05-01
影响因子：
3.3
通讯作者：
Lederkremer, GZ
中科院分区：
文献类型：
--
作者：
Frenkel, Z;Shenkman, M;Lederkremer, GZ
巯基氧化还原酶内质网（ER）p57通过与伴侣蛋白/凝集素钙连接蛋白或钙网蛋白的三元复合物与新合成的糖蛋白相互作用。在蛋白酶体抑制钙连接蛋白和钙网蛋白集中在我们最近描述的中心内质网衍生的质量控制室。令人惊讶的是，ERp 57仍然在内质网模式。使用去唾液酸糖蛋白受体H2 a和H2 b作为模型，我们在脉冲追踪实验中确定这两种糖蛋白最初与钙连接蛋白和ERp 57结合。然而，H2 b，这将退出到高尔基体，从钙连接蛋白解离，并保持结合了较长的时间，以ERp 57，而相反的是真正的内质网相关的降解底物H2 a，将去内质网衍生的质量控制室。在15 ℃时，ERp 57与H2 b共定位于内质网-高尔基体中间室标记物附近。翻译后抑制葡萄糖切除延长关联的H2 a前体钙连接蛋白，但不ERp 57。用低浓度（15 μ g/ml）的葡萄糖苷酶抑制剂栗精胺预孵育可阻止H2 a与ERp 57的结合，但不能与钙连接蛋白结合。这种低浓度的栗精胺加速了H2 a的降解，表明ERp 57保护糖蛋白而不是钙连接蛋白免于降解。我们的研究结果表明，早期分子伴侣介导的分选事件与钙连接蛋白参与的内质网相关的降解和ERp 57的分子结合的质量控制保留给予最初的保护降解，后来协助成熟的分子，将退出高尔基体。
The thiol oxidoreductase endoplasmic reticulum (ER)p57 interacts with newly synthesized glycoproteins through ternary complexes with the chaperones/lectins calnexin or calreticulin. On proteasomal inhibition calnexin and calreticulin concentrate in the pericentriolar endoplasmic reticulum-derived quality control compartment that we recently described. Surprisingly, ERp57 remained in an endoplasmic reticulum pattern. Using asialoglycoprotein receptor H2a and H2b as models, we determined in pulse-chase experiments that both glycoproteins initially bind to calnexin and ERp57. However, H2b, which will exit to the Golgi, dissociated from calnexin and remained bound for a longer period to ERp57, whereas the opposite was true for the endoplasmic reticulum-associated degradation substrate H2a that will go to the endoplasmic reticulum-derived quality control compartment. At 15degreesC, ERp57 colocalized with H2b adjacent to an endoplasmic reticulum-Golgi intermediate compartment marker. Posttranslational inhibition of glucose excision prolonged association of H2a precursor to calnexin but not to ERp57. Preincubation with a low concentration (15 mug/ml) of the glucosidase inhibitor castanospermine prevented the association of H2a to ERp57 but not to calnexin. This low concentration of castanospermine accelerated the degradation of H2a, suggesting that ERp57 protects the glycoprotein from degradation and not calnexin. Our results suggest an early chaperone-mediated sorting event with calnexin being involved in the quality control retention of molecules bound for endoplasmic reticulum-associated degradation and ERp57 giving initial protection from degradation and later assisting the maturation of molecules that will exit to the Golgi.