XPR Background Information
The xenotropic and polytropic retrovirus receptor (XPR) is a cell surface receptor that mediates infection by polytropic and xenotropic murine leukemia viruses, designated P-MLV and X-MLV respectively (1). In non-murine cells these receptors facilitate infection of both P-MLV and X-MLV retroviruses, while in mouse cells, XPR selectively permits infection by P-MLV only (2). XPR is classified with other mammalian type C oncoretroviruses receptors, which include the chemokine receptors that are required for HIV and simian immunodeficiency virus infection (3). XPR contains several hydrophobic domains indicating that it transverses the cell membrane multiple times, and it may function as a phosphate transporter and participate in G protein-coupled signal transduction (4). Expression of XPR is detected in a wide variety of human tissues, including pancreas, kidney and heart, and it shares homology with proteins identified in nematode, fly, and plant, and with the yeast SYG1 (suppressor of yeast G alpha deletion) protein (5,6).
