The poliovirus receptor protein is produced both as membrane-bound and secreted forms

Both genomic and complementary DNA clones encoding poliovirus receptors were isolated from genomic and complementary DNA libraries prepared from HeLa S3 cells, respectively. Nucleotide sequence analysis of these cloned DNAs revealed that the poliovirus receptor gene is ∼ 20 kb long and contains seven introns in the coding region, and that at least four mRNA isoforms referring to the coding sequence are generated by alternative splicing and appear to encode four different molecules, that is, PVRα, PVRβ, PVRγ and PVRδ. The predicted amino acid sequences indicate that PVRα and PVRδ, corresponding to the previously described cDNA clones H20A and H20B, respectively, are integral membrane proteins while the other two molecules described here for the first time lack a putative transmembrane domain. Mouse cell transformants carrying PVRα were permissive for poliovirus infection, but those carrying PVRβ were hardly permissive. In contrast to PVRα, PVRβ was not detected on the surface of the mouse cell transformants but was detected in the culture fluid by an immunological method using a monoclonal antibody against poliovirus receptor. Three types of splicing products for PVRα, PVRβ and PVRγ were detected by polymerase chain reactions using appropriate primers in poly(A)⁺ RNAs of the brain, leukocyte, liver, lung and placenta of humans; the choice of primers used did not permit detection of PVRδ. In situ hybridization using a cDNA fragment as a probe demonstrated that the PVR gene is located at the band q13.1 → q13.2 of human chromosome 19.