The poliovirus receptor: identification of domains and amino acid residues critical for virus binding.

The N-terminal domain 1 of the human poliovirus receptor (hPVR), a three-domain, immunoglobulin-like molecule, was previously shown to be necessary and sufficient to confer poliovirus (PV) susceptibility to mouse cells. However, studies with truncated versions of hPVR suggested that the C-terminal hPVR domains may contribute to receptor function. We describe sets of hybrid receptors, constructed between hPVR and hICAM-1 (human intercellular adhesion molecule-1) that were tested in mouse cells for hPVR functionally. Whereas the context in which hPVR is expressed is of minor importance, all three domains of hPVR are required to reach wild-type function. Single and multiple amino acid exchanges were introduced into the first hPVR domain in order to localize regions that were involved in virus-receptor interactions. The mutations were analyzed for their ability to bind PV1 (Mahoney) or monoclonal antibodies as well as their ability to support viral replication in either the hPVR alpha or hybrid hPVR-hICAM-1 receptor context. When placed into a model of the V domain of hPVR, the effect of the mutations indicated that the C'C"D as well as the DE region harbored amino acids that contacted the PV1(M) surface in the process of receptor-virus complex formation. The binding of the virus to the receptor and subsequent uptake into the cells were linked; no hPVR mutants were observed that bound the virus but blocked infection. N-glycosylation of the four sites in domains 1 and 2 is not required for hPVR function, but glycosylation in domain 1 has a greater effect on receptor function than that of domain 2.