Date Published: July 25, 2013
Publisher: Public Library of Science
Author(s): Yorihiro Nishimura, Hyunwook Lee, Susan Hafenstein, Chikako Kataoka, Takaji Wakita, Jeffrey M. Bergelson, Hiroyuki Shimizu, Carolyn B. Coyne.
Some strains of enterovirus 71 (EV71), but not others, infect leukocytes by binding to a specific receptor molecule: the P-selectin glycoprotein ligand-1 (PSGL-1). We find that a single amino acid residue within the capsid protein VP1 determines whether EV71 binds to PSGL-1. Examination of capsid sequences of representative EV71 strains revealed that the PSGL-1-binding viruses had either a G or a Q at residue 145 within the capsid protein VP1 (VP1-145G or Q), whereas PSGL-1-nonbinding viruses had VP1-145E. Using site-directed mutagenesis we found that PSGL-1-binding strains lost their capacity to bind when VP1-145G/Q was replaced by E; conversely, nonbinding strains gained the capacity to bind PSGL-1 when VP1-145E was replaced with either G or Q. Viruses with G/Q at VP1-145 productively infected a leukocyte cell line, Jurkat T-cells, whereas viruses with E at this position did not. We previously reported that EV71 binds to the N-terminal region of PSGL-1, and that binding depends on sulfated tyrosine residues within this region. We speculated that binding depends on interaction between negatively charged sulfate groups and positively charged basic residues in the virus capsid. VP1-145 on the virus surface is in close proximity to conserved lysine residues at VP1-242 and VP1-244. Comparison of recently published crystal structures of EV71 isolates with either Q or E at VP1-145 revealed that VP1-145 controls the orientation of the lysine side-chain of VP1-244: with VP1-145Q the lysine side chain faces outward, but with VP1-145E, the lysine side chain is turned toward the virus surface. Mutation of VP1-244 abolished virus binding to PSGL-1, and mutation of VP1-242 greatly reduced binding. We propose that conserved lysine residues on the virus surface are responsible for interaction with sulfated tyrosine residues at the PSGL-1 N-terminus, and that VP1-145 acts as a switch, controlling PSGL-1 binding by modulating the exposure of VP1-244K.
Enterovirus 71 (EV71) is a small, non-enveloped positive-stranded RNA virus that belongs to the human enterovirus species A of the genus Enterovirus in the family Picornaviridae. The viral RNA genome is enclosed in a capsid composed of four structural proteins, VP1, VP2, VP3, and VP4 , , . EV71 is a major causative agent of hand, foot, and mouth disease (reviewed in , , , ), a febrile illness that commonly affects young children. Although hand, foot, and mouth disease is usually mild and self-limited, EV71 infection may also cause severe diseases including poliomyelitis-like paralysis, brainstem encephalitis, and fatal cardiorespiratory failure. Recent EV71 outbreaks in the Asia-Pacific region have involved millions of children, and have caused thousands of deaths , .
The results we report here demonstrate that a single amino acid, VP1-145, is the critical determinant of EV71 tropism for PSGL-1. We found that the presence of a G or Q residue at this position permitted viruses belonging to a variety of genogroups to bind PSGL-1, whereas viruses with E at this position did not bind PSGL-1. Similarly, viruses with G or Q, but not E at VP1-145, were found to replicate in Jurkat T lymphocytes, supporting the idea that VP1-145, by controlling interaction with PSGL-1, plays an important role in virus tropism for human leukocytes.