RESUMEN
Human astroviruses (HAstV) are a frequent cause of gastroenteritis in young children and immunocompromised patients. To understand the early steps of HAstV infection in the highly permissive Caco-2 cell line, the binding and entry processes of the virus were characterized. The half-time of virus binding to the cell surface was about 10 min, while virus decapsidation took around 130 min. Drugs affecting clathrin-mediated endocytosis, endosome acidification, and actin filament polymerization, as well as those that reduce the presence of cholesterol in the cell membrane, decreased the infectivity of the virus. The infection was also reduced by silencing the expression of the clathrin heavy chain (CHC) by RNA interference or by overexpression of dominant-negative mutants of dynamin 2 and Eps15. Furthermore, the entry of HAstV apparently depends on the maturation of endosomes, since the infection was reduced by silencing the expression of Rab7, a small GTPase involved in the early- to late-endosome maturation. Altogether, our results suggest that HAstV enters Caco-2 cells using a clathrin-dependent pathway and reaches late endosomes to enter cells. Here, we have characterized the mechanism used by human astroviruses, important agents of gastroenteritis in children, to gain entry into their host cells. Using a combination of biochemical and genetic tools, we found that these viruses enter Caco-2 cells using a clathrin-dependent endocytic pathway, where they most likely need to travel to late endosomes to reach the cytoplasm and begin their replication cycle.
Asunto(s)
Mamastrovirus/fisiología , Internalización del Virus , Proteínas Adaptadoras del Transporte Vesicular/genética , Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Antivirales/farmacología , Infecciones por Astroviridae/genética , Infecciones por Astroviridae/metabolismo , Infecciones por Astroviridae/virología , Línea Celular , Clatrina/genética , Clatrina/metabolismo , Dinaminas/genética , Dinaminas/metabolismo , Endorribonucleasas/metabolismo , Proteínas Fúngicas/metabolismo , Silenciador del Gen , Humanos , Mamastrovirus/efectos de los fármacos , Mutación , Acoplamiento Viral , Liberación del Virus , Replicación Viral/efectos de los fármacos , Desencapsidación Viral , Proteínas de Unión al GTP rab/genética , Proteínas de Unión al GTP rab/metabolismo , Proteínas de Unión a GTP rab7RESUMEN
While recently we have learned much about the viral and cellular proteins involved in the initial attachment of rotaviruses to MA104 cells, the mechanism by which these viruses reach the interior of the cell is poorly understood. For this study, we observed the effects of drugs and of dominant-negative mutants, known to impair clathrin-mediated endocytosis and endocytosis mediated by caveolae, on rotavirus cell infection. Rotaviruses were able to enter cells in the presence of compounds that inhibit clathrin-mediated endocytosis as well as cells overexpressing a dominant-negative form of Eps15, a protein crucial for the assembly of clathrin coats. We also found that rotaviruses infected cells in which caveolar uptake was blocked; treatment with the cholesterol binding agents nystatin and filipin, as well as transfection of cells with dominant-negative caveolin-1 and caveolin-3 mutants, had no effect on rotavirus infection. Interestingly, cells treated with methyl-beta-cyclodextrin, a drug that sequesters cholesterol from membranes, and cells expressing a dominant-negative mutant of the large GTPase dynamin, which is known to function in several membrane scission events, were not infected by rotaviruses, indicating that cholesterol and dynamin play a role in the entry of rotaviruses.