Cell Entry of Avian Reovirus Follows a Caveolin-1-mediated and Dynamin-2-dependent Endocytic Pathway That Requires Activation of p38 Mitogen-activated Protein Kinase (MAPK) and Src Signaling Pathways as Well as Microtubules and Small GTPase Rab5 Protein

Abstract

Very little is known about the mechanism of cell entry of avian reovirus (ARV). The aim of this study was to explore the mechanism of ARV entry and subsequent infection. Cholesterol mainly affected the early steps of the ARV life cycle, because the presence of cholesterol before and during viral adsorption greatly blocked ARV infectivity. Although we have demonstrated that ARV facilitating p38 MAPK is beneficial for virus replication, its mechanism remains unknown. Here, we show that ARV-induced phosphorylation of caveolin-1 (Tyr 14 ), dynamin-2 expression, and Rac1 activation through activation of p38 MAPK and Src in the early stage of the virus life cycle is beneficial for virus entry and productive infection. The strong inhibition by dynasore, a specific inhibitor of dynamin-2, and depletion of endogenous caveolin-1 or dynamin-2 by siRNAs as well as the caveolin-1 colocalization study implicate caveolin-1-mediated and dynamin-2-dependent endocytosis as a significant avenue of ARV entry. By means of pharmacological inhibitors, dominant negative mutants, and siRNA of various cellular proteins and signaling molecules, phosphorylation of caveolin-1, dynamin-2 expression, and Rac1 activation were suppressed, suggesting that by orchestrating p38 MAPK, Src, and Rac1 signaling cascade in the target cells, ARV creates an appropriate intracellular environment facilitating virus entry and productive infection. Furthermore, disruption of microtubules, Rab5, or endosome acidification all inhibited ARV infection, suggesting that microtubules and small GTPase Rab5, which regulate transport to early endosome, are crucial for survival of ARV and that exposure of the virus to acidic pH is required for productive infection.

Pyridinyl imidazole inhibitors of p38 MAP kinase impair viral entry and reduce cytokine induction by Zaire ebolavirus in human dendritic cells

“…For example, p38 MAPK activation and signaling is important for viral entry of reovirus and respiratory virus (Huang et al, 2011; Marchant et al, 2010). p38 MAPK signaling has also been implicated as playing a role in the viral transcription and translation of a number of viruses including hepatitis C virus, avian reovirus, porcine circovirus type 2, porcine reproductive and respiratory syndrome virus, rotavirus, Kaposi sarcoma-associated herpesvirus, encephalomyocarditis virus and HIV-1 (Cohen et al, 1997; George et al, 2012; Hirasawa et al, 2003; Jafri et al, 2007; Ji et al, 2009; Lee and Lee, 2012; Pan et al, 2006; Wei et al, 2009); and inhibition of p38 MAPK signaling has been shown to directly inhibit virus infection (Chang et al, 2008; Ludwig et al, 2003; Wei et al, 2009).…”

Hijacking of RIG-I Signaling Proteins into Virus-Induced Cytoplasmic Structures Correlates with the Inhibition of Type I Interferon Responses

“…In addition, the endosomal pathway has been shown to promote internalization and/or virus replication (60)(61)(62)(63). Indeed, entry into Rab5 ϩ early endosomes has been previously described for Uukuniemi virus, another member of the genus Phlebovirus (64).…”

Molecular characterization of avian reovirus isolates in Tunisia

“…The σC protein plays a role for virus attachment [16] and as apoptosis inducer [17]. It has been demonstrated that cell entry of avian reovirus follows a caveolin-1-mediated and dynamin-2-dependent endocytic pathways that require activation of p38 MAPK and Src signaling pathways [18]. It has also been suggested that it represents the target for type-specific neutralizing antibodies.…”