Fibronectin Facilitates Enterovirus 71 Infection by Mediating Viral Entry

Abstract

Fibronectin (FN) is a high-molecular-weight extracellular matrix protein that contains the RGDS motif, which is required to bind to integrins. Synthetic RGDS peptides have been reported to compete with FN to bind to the cell surface and inhibit the function of FN. Here, we identified that synthetic RGDS peptides significantly inhibit human enterovirus 71 (EV71) infection in cell cultures. In addition, mice treated with RGDS peptides and infected with EV71 had a significantly higher survival rate and a lower viral load than the control group. Because RGDS peptides affect the function of FN, we questioned whether FN may play a role in virus infection. Our study indicates that overexpression of FN enhanced EV71 infection. In contrast, knockout of FN significantly reduced viral yield and decreased the viral binding to host cells. Furthermore, EV71 entry, rather than intracellular viral replication, was blocked by FN inhibitor pretreatment. Next, we found that FN could interact with the EV71 capsid protein VP1, and further truncated-mutation assays indicated that the D2 domain of FN could interact with the N-terminal fragment of VP1. Taken together, our results demonstrate that the host factor FN binds to EV71 particles and facilitates EV71 entry, providing a potential therapy target for EV71 infection. Hand, foot, and mouth disease outbreaks have occurred frequently in recent years, sometimes causing severe neurological complications and even death in infants and young children worldwide. Unfortunately, no effective antiviral drugs are available for human enterovirus 71 (EV71), one of the viruses that cause hand, foot, and mouth disease. The infection process and the host factors involved remain unknown, although several receptors have been identified. In this study, we found that the host factor fibronectin (FN) facilitated EV71 replication by interacting with EV71 particles and further mediated their entry. The RGDS peptide, an FN inhibitor, significantly inhibited EV71 replication in both RD cells and mice. In conclusion, our research identified a new host factor involved in EV71 infection, providing a new potential antiviral target for EV71 treatment.

Cellular receptors for enterovirus A71

“…Most of these alternative attachment receptors cannot initiate uncoating. The involvement of attachment receptors is demonstrated during infection of cultured cells, and most were reported in only a single publication [39][40][41][43][44][45]. Therefore, neither the mode of internalization nor the uncoating activity has been confirmed.…”

“…Fibronectin is a high molecular weight glycoprotein that plays important roles in cell adhesion, growth, migration, and differentiation [124]. He et al [44] found that overexpression of fibronectin enhanced EV-A71 infection, and that knockout of fibronectin reduced viral binding to host cells and decreased viral yield. A short peptide containing an Arg-Gly-Asp (RGD) motif, which is known to inhibit interaction between integrin and fibronectin, inhibited EV-A71 infection in cultured cells and in neonatal mice.…”

“…During EV-A71 infection, hSCARB2 plays pivotal roles in attachment, internalization, and uncoating, but it is not the only receptor that supports infection. In studies using cultured cells, it has been shown that other molecules such as P-selectin glycoprotein ligand-1 (PSGL-1) [38], annexin II (Anx2) [39], vimentin [40], nucleolin [41], heparan sulfate (HS) proteoglycan [42], sialylated glycan [43], fibronectin [44], and prohibitin [45] support viral attachment to the cell surface but cannot induce conformational changes in the virion that lead to uncoating; therefore, they are called "attachment receptors" (Fig. 2).…”

miR‐545 promoted enterovirus 71 replication via directly targeting phosphatase and tensin homolog and tumor necrosis factor receptor‐associated factor 6

“…Recently, miRNAs were found to play important roles in the viral replication of EV71. In the present study, we found that upregulation of miR-545 was induced by EV71 infection in HEK293 and RD cells, where these two lines have been commonly used as an in vitro cell model for EV71 infection(He et al, 2018;B. Wang, Zhang, & Zhao, 2013;Yue et al, 2017).…”

Involvement of VCP/UFD1/Nucleolin in the viral entry of Enterovirus A species

“…SCARB2 binds EVA71 on the southern rim of the canyon (Zhou et al, 2019) and expelles the pocket factor from the EVA71 virion, hence destabilizing the capsid and triggering the uncoating process (Dang et al, 2014). In addition, other host factors on the cell surface are reported to facilitate EVA71 entry, such as Annexin A2, fibronectin, vimentin and nucleolin (Du et al, 2014;He et al, 2018;Su et al, 2015;Yang et al, 2011). These receptors were identified as binding receptors to capture EVA71 on the cell surface.…”