Identification of a Human SCARB2 Region That Is Important for Enterovirus 71 Binding and Infection

Abstract

We previously identified human scavenger receptor class B, member 2 (SCARB2), as a cellular receptor for enterovirus 71 (EV71). Expression of human SCARB2 (hSCARB2) permitted mouse L929 cells to efficiently bind to virions and to produce both viral proteins and progeny viruses upon EV71 infection. Mouse Scarb2 (mScarb2) exhibited 85.8% amino acid identity and 99.9% similarity to hSCARB2. The expression of mScarb2 in L929 cells conferred partial susceptibility. Very few virions bound to mScarb2-expressing cells. The viral titer in L929 cells expressing mScarb2 was approximately 40-to 100-fold lower than that in L929 cells expressing hSCARB2. Using hSCARB2-mScarb2 chimeric mutants, we attempted to map the region that was important for efficient EV71 infection. L929 cells expressing chimeras that carried amino acids 142 to 204 from the human sequence were susceptible to EV71, while chimeras that carried the mouse sequence in this region were not. Moreover, this region was also critical for binding to virions. The determination of this region in hSCARB2 that is important for EV71 binding and infection greatly contributes to the understanding of virus-receptor interactions. Further studies will clarify the early steps of EV71 infection.Enterovirus 71 (EV71), together with coxsackievirus A16 (CVA16), belongs to human enterovirus species A of the genus Enterovirus within the family Picornaviridae (28). The virus contains a single-stranded, positive-sense RNA surrounded by an icosahedral capsid assembled from 60 copies of each of the four structural proteins: VP1, VP2, VP3, and VP4 (32). EV71 was first isolated from patients with neurological diseases, including fatal encephalitis and aseptic meningitis, in California from 1969 to 1972 (33). Later studies revealed that EV71 is associated with hand-foot-and-mouth disease (HFMD) in young children and infants (6, 13). Although HFMD is generally considered a mildly infectious disease, HFMD caused by EV71, but not by other enteroviruses, is sometimes involved with severe neurological diseases, including brain stem encephalitis and acute flaccid paralysis (23). In recent years, epidemic or sporadic outbreaks of neurovirulent EV71 infections have been reported mainly in Southeast or East Asia, including Taiwan, Malaysia, Singapore, Japan, and China (1,8,11,17,27,38 Human RD cells are highly susceptible to EV71 infection, whereas mouse L929 cells exhibit very low susceptibility. We previously reported the identification of EV71 receptors by genetic complementation of L929 cells with genes transferred from human RD cells (37). Briefly, we established two EV71-susceptible cell lines that carried a portion of human genomic DNA. By identifying the integrated human DNA in one of the transformants, Ltr051 cells, we have shown that scavenger receptor class B, member 2 (SCARB2), is a cellular receptor for EV71. SCARB2 serves as a receptor for all EV71 isolates tested. EV71 infection in the SCARB2-expressing L929 cell line is as efficient as that in the RD cell line (37). We have also f...

Cell Surface Nucleolin Facilitates Enterovirus 71 Binding and Infection

“…In addition, EV71 can interact with sialylated, desialylated, or deglycosylated SCARB2 (9,15). These findings suggest that sialylation may be a common modification for EV71 receptors, and the removal of sialic acids does not affect the binding of EV71 to receptors.…”

“…EV71 strains can be divided into different subgenotypes based on sequence homology (14). Human SCARB2 (hSCARB2) mediates the entry of EV71 strains or genotypes tested (15). SCARB2 not only facilitates the infection of EV71 but is also involved in virus internalization and the viral RNA uncoating of EV71 (16).…”

Impact of SCARB2 on pro-inflammatory cytokines in tissues of EV71-infected mice

“…Taken together, we assume that in EV71 infected mice, the elevated local mSCARB2 may regulate the early innate immune response to EV71, or even modulate pro-inflammatory cytokines induction; mSCARB2 may also act as the invasive receptor for the enterovirus 71 although no experimental evidence has ever been provided to support this hypotheses, because human SCARB2 (hSCARB2) have been identified as cellular receptors for EV71, and mSCARB2 exhibited 85.8% amino acid identity and 99.9% similarity to hSCARB2 [39,40]. The elevated expression of mSCARB2 in EV71-infected mice may play other roles, which are not clear now.…”

Antiviral activity of acid beta-glucosidase 1 on enterovirus 71, a causative agent of hand, foot and mouth disease

“…The SCARB2 binding site for GBA1 partly overlaps with that of EV71 [22][23][24]. It is likely that exogenous GBA1 physically competes with EV71 to bind to SCARB2, leading to the inhibition of EV71 infection.…”

“…This result may be explained by the observation that U251MG cells are poorly susceptible to EV71 infection owing to their low surface levels of SCARB2; thus, ectopic GBA1 can sufficiently downregulate SCARB-2 expression such that U251MG cells can survive the screen. In addition, SCARB2 may be the only receptor available to EV71 in U251MG cells [23].…”