Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.
Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.
J Virol. 2022 Jul 27;96(14):e0066522. doi: 10.1128/jvi.00665-22. Epub 2022 Jun 28.
Human astrovirus VA1 has been associated with neurological disease in immunocompromised patients, and its recent propagation in cell culture has opened the possibility to study its biology. Unlike classical human astroviruses, VA1 growth was found to be independent of trypsin during virus replication . In this work, we show that despite its independence on trypsin activation for cell infection, the VA1 capsid precursor protein, of 86 kDa (VP86), is processed intracellularly, and this proteolytic processing is important for astrovirus VA1 infectivity. Antibodies raised against different regions of the capsid precursor showed that the polyprotein can be processed starting at either its amino- or carboxy-terminal end, and they allowed us to identify those proteins of about 33 (VP33) and 38 (VP38) kDa constitute the core and the spike proteins of the mature infectious virus particles, respectively. The amino-terminal end of the spike protein was found to be Thr-348. Whether the protease involved in intracellular cleavage of the capsid precursor is of viral or cellular origin remains to be determined, but the cleavage is independent of caspases. Also, trypsin is able to degrade the capsid precursor but has no effect on VP33 and VP38 proteins when assembled into virus particles. These studies provide the basis for advancement of the knowledge of astrovirus VA1 cell entry and replication. Human astrovirus VA1 has been associated with neurological disease in immunocompromised patients. Its recent propagation in cell culture has facilitated the study of its biology. In this work, we show that despite the ability of this virus to grow in the absence of trypsin, a marked feature of human classical astroviruses, the capsid precursor protein of astrovirus VA1 is cleaved intracellularly to yield the mature infectious particles, formed by two polypeptides, VP33 that constitutes the core domain of the virus particle, and VP38 that forms the spike of the virus. These studies provide a platform to advance our knowledge on astrovirus VA1 cell entry and replication.
人类星状病毒 VA1 与免疫功能低下患者的神经疾病有关，其最近在细胞培养中的繁殖为研究其生物学特性提供了可能。与经典的人类星状病毒不同，VA1 的生长在病毒复制过程中不依赖于胰蛋白酶。在这项工作中，我们表明，尽管 VA1 衣壳前体蛋白（VP86）在感染细胞时不依赖于胰蛋白酶激活，但它在细胞内被加工，这种蛋白水解加工对于星状病毒 VA1 的感染性很重要。针对衣壳前体不同区域的抗体表明，多蛋白可以从其氨基或羧基末端开始加工，并且它们使我们能够鉴定出大约 33（VP33）和 38（VP38）kDa 的蛋白质分别构成成熟感染性病毒颗粒的核心和刺突蛋白。刺突蛋白的氨基末端被发现为 Thr-348。参与衣壳前体细胞内切割的蛋白酶是病毒还是细胞起源仍有待确定，但切割过程不依赖于半胱天冬酶。此外，胰蛋白酶能够降解衣壳前体，但当组装成病毒颗粒时，对 VP33 和 VP38 蛋白没有影响。这些研究为星状病毒 VA1 细胞进入和复制的知识进展提供了基础。
