MOUSE HOMOLOG OF POLIOVIRUS RECEPTOR-RELATED GENE-2 PRODUCT, MPRR2, MEDIATES HOMOPHILIC CELL-AGGREGATION

Poliovirus receptor (PVR) is a cell surface glycoprotein that belongs to the immunoglobulin superfamily. Although MPH was initially reported as the mouse homolog of human PVR, recent data strongly suggest that MPH is the mouse homolog of human PRR2, a PVR-related gene 2 product, and not that of human PVT,. Thus MPH is renamed. mPRR2 in this study. Physiological functions of the PVR-related gene products have not been elucidated, although PVR has been well, characterized as the poliovir us receptor. In this study, a possible function of mPRR2 (MPH), which is not a functional receptor for poliovirus, was investigated. Mouse L cells expressing mPRR2 were prepared. Those mouse cells showed a high er activity of cell aggregation than the parental mouse L cells, Enhan cement of cell aggregation was also observed for insect Sf9 cells infe cted with recombinant baculovirus carrying mPRR2 cDNA. On the other ha nd, L cells expressing human PVR. or monkey PVR (AGM alpha 1 or AGM al pha 2) did not show increased cell aggregation. The cell aggregation a ctivity of L cells expressing mPRR2 was inhibited by the addition of a nti-mPRR2 monoclonal antibodies or a soluble mPRR2 molecule produced b y the baculovirus expression system. An immunofluorescence study revea led that MPRR2 protein was localized to the cell-cell contact sites be tween cells expressing mPRR2. A similar localization of mPRR2 was obse rved for intrinsic mPRR2 molecules of the mouse neuroblastoma cell lin e NS20Y. The contact site-specific localization of mPRR2 was not obser ved on the border between mPRR2-expressing and nonexpressing HeLa cell s. Furthermore, mPRR2 proteins directly bound to each other in vitro, mPRR2 was detected on various types of cultured cells of mouse origin aid in various mouse tissues. These results suggest that mPRR2 is an i ntercellular adhesion molecular with a homophilic binding manner. (C) 1997 Academic Press.