Competitive Inhibition of the Endoplasmic Reticulum Signal Peptidase by Non-cleavable Mutant Preprotein Cargos
Competitive Inhibition of the Endoplasmic Reticulum Signal Peptidase by Non-cleavable Mutant Preprotein Cargos
复制标题
不可切割的突变前蛋白货物对内质网信号肽酶的竞争性抑制
DOI：
10.1074/jbc.m115.692350
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发表时间：
2015-11-20
影响因子：
4.8
通讯作者：
Liu, Ming
中科院分区：
文献类型：
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作者：
Cui, Jingqiu;Chen, Wei;Liu, Ming
当内质网(ER)膜转运时，分泌蛋白被蛋白水解酶(Spase)处理以去除它们的信号肽。这一过程对随后的折叠、细胞内运输和分泌蛋白的成熟至关重要。原核生物Spase已被证明是一个很有前途的抗生素靶点。相反，到目前为止，还没有真核细胞Spase抑制剂的报道。在这里，我们报告说，在天然信号肽裂解位点之后立即引入Pro不仅阻止了前蛋白的切割，而且在反式情况下，也损害了内质网中共表达的前蛋白的加工和成熟。具体地说，我们发现一个变异的前胰岛素原PPI-F25P被转移到ER膜上，在那里它与催化Spase亚单位SEC11A结合，以剂量依赖的方式抑制Spase的活性。对甲状旁腺前激素的类似变体也得到了类似的发现，表明Spase的抑制并不严格依赖于下游成熟蛋白的序列或结构。我们进一步表明，抑制内质网中的Spase会损害病毒多肽的细胞内处理和随后的成熟。这些观察结果表明，真核SPase(包括人类同源基因)原则上是抗病毒药物设计的合适治疗靶点。
Upon translocation across the endoplasmic reticulum (ER) membrane, secretory proteins are proteolytically processed to remove their signal peptide by signal peptidase (SPase). This process is critical for subsequent folding, intracellular trafficking, and maturation of secretory proteins. Prokaryotic SPase has been shown to be a promising antibiotic target. In contrast, to date, no eukaryotic SPase inhibitors have been reported. Here we report that introducing a proline immediately following the natural signal peptide cleavage site not only blocks preprotein cleavage but also, in trans, impairs the processing and maturation of co-expressed preproteins in the ER. Specifically, we find that a variant preproinsulin, pPI-F25P, is translocated across the ER membrane, where it binds to the catalytic SPase subunit SEC11A, inhibiting SPase activity in a dose-dependent manner. Similar findings were obtained with an analogous variant of preproparathyroid hormone, demonstrating that inhibition of the SPase does not depend strictly on the sequence or structure of the downstream mature protein. We further show that inhibiting SPase in the ER impairs intracellular processing of viral polypeptides and their subsequent maturation. These observations suggest that eukaryotic SPases (including the human ortholog) are, in principle, suitable therapeutic targets for antiviral drug design.