Poliovirus receptor (hPVR/CD155) is a cell surface glycoprotein that belongs to the immunoglobulin superfamily but its natural function remains unknown. Two membrane-bound isoforms, hPVR alpha and hPVR delta, are known to date, and they differ only in the amino acid sequence of their cytoplasmic domains. To gain an insight into the possible function of the cytoplasmic domains, we examined the localization of introduced hPVR alpha and hPVR delta in polarized epithelial cells deficient of native hPVRs. Basolateral sorting of hPVR alpha was observed in Madine-Darby canine kidney cells expressing mu 1B, but not in LLC-PK1 porcine kidney cells deficient in mu 1B. Distribution of hPVR delta, however, occurred both on the apical and basolateral plasma membranes of these two cell lines. Basolateral sorting of hPVR alpha was also seen in LLC-PK1 cells that expressed an intact exogenous mu 1B, but not in the cells that expressed a mutant mu 1B lacking binding ability to tyrosine-containing signals. These results indicate that mu 1B is involved in the distribution of hPVR alpha to the basolateral membrane. Comparative distribution analysis of hPVR alpha using a series of mutants with truncations and substitutions in the cytoplasmic tail demonstrated that determinant for the basolateral sorting resided in the tyrosine-containing motif of the cytoplasmic tail. Furthermore, yeast two hybrid analysis strongly suggested that the tyrosine motif directly interacted with mu 1B protein. Thus, basolateral sorting of hPVR alpha appears to involve the interaction with mu 1B through a tyrosine motif existing in the cytoplasmic domain.