Department of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA.
Virginia Maryland College of Veterinary Medicine, College Park, MD 20742, USA.
Viruses. 2021 Aug 11;13(8):1587. doi: 10.3390/v13081587.
The capsid precursor P1 constitutes the N-terminal part of the enterovirus polyprotein. It is processed into VP0, VP3, and VP1 by the viral proteases, and VP0 is cleaved autocatalytically into VP4 and VP2. We observed that poliovirus VP0 is recognized by an antibody against a cellular autophagy protein, LC3A. The LC3A-like epitope overlapped the VP4/VP2 cleavage site. Individually expressed VP0-EGFP and P1 strongly colocalized with a marker of selective autophagy, p62/SQSTM1. To assess the role of capsid proteins in autophagy development we infected different cells with poliovirus or encapsidated polio replicon coding for only the replication proteins. We analyzed the processing of LC3B and p62/SQSTM1, markers of the initiation and completion of the autophagy pathway and investigated the association of the viral antigens with these autophagy proteins in infected cells. We observed cell-type-specific development of autophagy upon infection and found that only the virion signal strongly colocalized with p62/SQSTM1 early in infection. Collectively, our data suggest that activation of autophagy is not required for replication, and that capsid proteins contain determinants targeting them to p62/SQSTM1-dependent sequestration. Such a strategy may control the level of capsid proteins so that viral RNAs are not removed from the replication/translation pool prematurely.
衣壳前体 P1 构成肠道病毒多蛋白的 N 端部分。它被病毒蛋白酶加工成 VP0、VP3 和 VP1，而 VP0 则自动切割成 VP4 和 VP2。我们观察到脊髓灰质炎病毒 VP0 被一种针对细胞自噬蛋白 LC3A 的抗体识别。LC3A 样表位与 VP4/VP2 切割位点重叠。单独表达的 VP0-EGFP 和 P1 与选择性自噬的标志物 p62/SQSTM1 强烈共定位。为了评估衣壳蛋白在自噬发展中的作用，我们用脊髓灰质炎病毒或编码仅复制蛋白的包膜脊髓灰质炎复制子感染不同的细胞。我们分析了 LC3B 和 p62/SQSTM1 的加工，这是自噬途径起始和完成的标志物，并研究了病毒抗原在感染细胞中与这些自噬蛋白的关联。我们观察到感染后细胞类型特异性自噬的发展，并发现只有病毒信号在感染早期与 p62/SQSTM1 强烈共定位。总的来说，我们的数据表明，自噬的激活不是复制所必需的，并且衣壳蛋白包含将它们靶向到 p62/SQSTM1 依赖性隔离的决定因素。这种策略可能控制衣壳蛋白的水平，从而使病毒 RNA 不会过早从复制/翻译池中被清除。
