The poliovirus receptor CD155 mediates cell-to-matrix contacts by specifically binding to vitronectin.

The human receptor for poliovirus (CD155) is an immunoglobulin-like molecule with unknown normal function(s). Here we provide evidence that CD155 binds specifically to vitronectin with a dissociation constant (K(d)) of 72 nM as determined by surface plasmon resonance. Based on sequence homology to the CD155 gene, three poliovirus receptor-related genes (PRR1, PRR2, and PRR3) were cloned recently. PRR proteins were reported by others to mediate homophilic cell adhesion. Neither PRR1 nor PRR2 binds poliovirus and it is assumed that their physiological functions differ from that of CD155. Indeed, mPRR2 was found to bind to vitronectin only weakly, while its self-adhesion activity is characterized by a K(d) of 310 nM. Moreover, there is no evidence for CD155 self-adhesion. Both CD155 and vitronectin colocalize to follicular dendritic cells and B cells inside the germinal centers of secondary lymphoid tissue (tonsils)-an observation suggesting that the CD155/vitronectin interaction is required for the establishment of a proper immune response in this particular context.