Abstract：
The signal peptide (SP) of integrated membrane proteins is removed cotranslationally or posttranslationally in the endoplasmic reticulum, while GP64, a membrane fusion protein of Bombyx mori nucleopolyhedrovirus (BmNPV), retains its SP in the mature protein and virion. In this study, we revealed that uncleaved SP is a key determinant with additional functions in infection. First, uncleaved SP endows BmNPV with strong virulence; second, SP retention-induced BmNPV infection depends on cholesterol recognition amino acid consensus domain 1 (CRAC1) and CRAC2. In contrast, the recombinant virus with SP-cleaved GP64 has reduced infectivity, and only CRAC2 is required for BmNPV infection. Furthermore, we showed that cholesterol in the plasma membrane is an important fusion receptor that interacts with CRAC2 of GP64. Our study suggested that BmNPV GP64 is a key cholesterol-binding protein and uncleaved SP determines GP64\'s unique dependence on the CRAC domains. IMPORTANCE BmNPV is a severe pathogen that mainly infects silkworms. GP64 is the key membrane fusion protein that mediates BmNPV infection, and some studies have indicated that cholesterol and lipids are involved in BmNPV infection. A remarkable difference from other membrane fusion proteins is that BmNPV GP64 retains its SP in the mature protein, but the cause is still unclear. In this study, we investigated the reason why BmNPV retains this SP, and its effects on protein targeting, virulence, and CRAC dependence were revealed by comparison of recombinant viruses harboring SP-cleaved or uncleaved GP64. Our study provides a basis for understanding the dependence of BmNPV infection on cholesterol/lipids and host specificity.
摘要：
整合膜蛋白的信号肽（SP）在内质网中被共翻译或翻译后去除，而家蚕核型多角体病毒(BmNPV)的膜融合蛋白GP64,将其SP保留在成熟蛋白质和病毒体中。在这项研究中,我们发现，未切割的SP是感染中具有其他功能的关键决定因素。首先,未裂解的SP赋予BmNPV强毒力；第二，SP滞留诱导的BmNPV感染取决于胆固醇识别氨基酸共有结构域1(CRAC1)和CRAC2。相比之下,具有SP切割的GP64的重组病毒具有降低的感染性，BmNPV感染仅需要CRAC2。此外，我们表明，质膜中的胆固醇是与GP64的CRAC2相互作用的重要融合受体。我们的研究表明，BmNPVGP64是一种关键的胆固醇结合蛋白，未裂解的SP决定了GP64对CRAC结构域的独特依赖性。重要性BmNPV是一种严重的病原体，主要感染家蚕。GP64是介导BmNPV感染的关键膜融合蛋白,一些研究表明，胆固醇和脂质参与BmNPV感染。与其他膜融合蛋白的显著区别在于BmNPVGP64在成熟蛋白中保留了其SP,但原因尚不清楚。在这项研究中,我们调查了BmNPV保留该SP的原因，以及它对蛋白质靶向的影响，毒力,通过比较包含SP切割或未切割的GP64的重组病毒，揭示了CRAC依赖性。我们的研究为理解BmNPV感染对胆固醇/脂质和宿主特异性的依赖性提供了基础。
