Unpublished data. 7. virus-based retrovirus vector pseudotyped with the MMTV envelope protein. An epitope-tagged MTVR cofractionated with cellular membranes. Coimmunoprecipitation of the MMTV envelope protein and a MTVR-rabbit Fc fusion protein showed that these two proteins bound to each other. The MTVR sequence Atreleuton clone is unique, shows no homology to known membrane proteins, and is transcribed in many cells. Mouse mammary tumor computer virus (MMTV) is definitely a causative agent of mammary carcinomas in vivo and is acquired as an exogenous computer virus when newborns suckle within the milk of viremic mothers (14). Like additional retroviruses, MMTV encodes an envelope protein, consisting of two chains generated by control a precursor polyprotein, a cell surface (SU) website of 52 kDa and a transmembrane website of 36 kDa (22). It is the SU protein that binds the cellular receptor for the computer virus, since anti-SU antibody blocks MMTV illness of cultured cells (10). Although the ultimate target for Atreleuton MMTV is the mammary gland, cells of the immune system play a role in milk-borne computer virus illness (2, 7, 9; for a review, see research 16). MMTV encodes a superantigen protein in its long terminal repeat that is presented from the major histocompatibility complex class II proteins and interacts with the V portion of the T-cell receptor (examined in research 16). During the course of milk-borne MMTV transmission, the computer virus is definitely 1st acquired by B cells in the Peyers patches (2, 9). These B cells act as antigen-presenting cells and present the superantigen to T cells. Subsequent to the activation of the B and T cells, both types become MMTV infected and are capable of dropping virions, at least in vitro (5). Whether both B and T cells transmit computer virus to the mammary gland has not yet been resolved, since adoptive transfer studies of the different lymphocyte subsets from infected mice into nude mice indicated that only T cells transmitted computer virus (20), whereas related studies with immunocompetent mice showed that transfer of either B or T cells resulted in transmission of the computer virus to both cell types of an uninfected sponsor (21). In spite of our knowledge of the cell types involved in transmission of MMTV from milk to the mammary gland, the molecular methods involved in this process have not yet been elucidated. For example, it is not known how the computer virus gets into the cells of the lymphoid system or how it is transferred to mammary gland cells. One crucial component of this technique is the cellular receptor, the molecule(s) present within the cell surface that binds to the viral envelope protein. Atreleuton Previously, it has been shown the MMTV receptor maps to chromosome 16 in the mouse (10). It was also reported that MMTV virions could bind to cells from many different cells, but that mammary gland and spleen were able to bind higher amounts than salivary gland, ovary, adrenal gland, and liver (3). If this binding activity represents computer virus interaction with the actual MMTV receptor, mammary gland and lymphoid cells might be probably the most efficiently infected because they have the highest receptor levels. To identify the cellular receptor for MMTV, we used computer virus binding to cells transfected having a mouse cDNA manifestation library to enrich for clones that coded for this receptor. Using this method, we isolated the gene for any novel membrane-associated protein that confers both MMTV binding and infectability. This gene, which is also found Rabbit polyclonal to Fyn.Fyn a tyrosine kinase of the Src family.Implicated in the control of cell growth.Plays a role in the regulation of intracellular calcium levels.Required in brain development and mature brain function with important roles in the regulation of axon growth, axon guidance, and neurite extension.Blocks axon outgrowth and attraction induced by NTN1 by phosphorylating its receptor DDC.Associates with the p85 subunit of phosphatidylinositol 3-kinase and interacts with the fyn-binding protein.Three alternatively spliced isoforms have been described.Isoform 2 shows a greater ability to mobilize cytoplasmic calcium than isoform 1.Induced expression aids in cellular transformation and xenograft metastasis. in humans and additional mammals, not only is likely to be important for MMTV illness of mice but also must play a role in normal cell function. MATERIALS AND METHODS Receptor cloning. A cDNA library was prepared from RNA isolated from your thymi of Swiss Webster mice in the pcDNA1 vector (Stratagene, Inc., La Jolla, Calif.), comprising the cytomegalovirus (CMV) promoter and simian computer virus 40 source of replication, using the Superscript plasmid system (Gibco/BRL, Bethesda, Md.). A total of 2 106 self-employed clones were transfected into Cos-7 cells by spheroplast fusion (1). After transfection, the cells were incubated 1st with MMTV(C3H) particles (0.5 g/ml) at 37C for 1 h and then washed and incubated with monospecific.