The first step in virus infection is the binding of viruses to cellular receptors, and cell or species specificities of virus infection are determined in part by the virus receptors. The cDNAs of a candidate gene of BLV receptor (BLVR) were cloned as a gene coding a protein which binds to BLV Env protein, and transfection of the BLVR cDNA into mouse NIH3T3 cells greatly increased the susceptibility of the cells to BLV infection. Although the reported bovine BLVR cDNA was supposed to be a type I transmembrane protein which has signal peptides and a transmembrane (TM) domain, the mouse cDNA (mBLVR1) we cloned lacked the corresponding transmembrane and cytoplasmic regions of the predicted bovine BLVR protein and was closely related to the delta subunit of adaptor-related protein complex, AP-3, not associated with the cell surface. Thus the mouse BLVR homologue appeared to be the mouse AP-3 delta subunit itself or closely related to it, but the bovine BLVR gene seemed slightly different from the adaptor subunit gene family.
(Lab. of Immunogenetics, Department of Immunology)