A NOVEL MEMBRANE-PROTEIN IS A MOUSE MAMMARY-TUMOR VIRUS RECEPTOR

Mouse mammary tumor virus (MMTV) infects a number of different cell ty pes, including mammary gland and lymphoid cells, in vivo. To identify the cellular receptor for this virus, a mouse cDNA expression library was transfected into Cos-7 monkey kidney cells, and those transfected cells able to bind virus were selected by using antibody against the v irus's cell surface envelope protein, gp52. One clone isolated from a library prepared from neu born thymus RNA, called MTVR, was able to co nfer virus binding to both monkey and human cells; this binding was bl ocked by anti-MTVR antibody, Moreover, transfection of MTVR into CV1 c ells rendered them susceptible to infection by a murine leukemia virus -based retrovirus vector pseudotyped with the MMTV envelope protein. A n epitope-tagged MTVR cofractionated with cellular membranes, Coimmuno -precipitation of the MMTV envelope protein and a MTVR-rabbit Fc fusio n protein showed that these two proteins bound to each other, The MTVR sequence clone is unique, shows no homology to known membrane protein s, and is transcribed in many tissues.