title: Identification and characterization of a mouse mammary tumor virus protein uniquely expressed on the surface of BALB/cV mammary tumor cells.
abstract: A unique subline of BALB/c mice, designated BALB/cV, exhibits an intermediate mammary tumor incidence (47%) and harbors a distinct milk-transmitted mouse mammary tumor virus (MMTV). The BALB/cV subline was used to study the molecular basis of potential virus-host interactions involving cell surface-expressed MMTV proteins. Cell surface iodination identified virus-specific proteins expressed on BALB/cV primary mammary tumor cells grown in culture. In contrast to (C3H)MMTV-producing cell lines which expressed MMTV gp52, BALB/cV tumor cells lacked gp52 and expressed instead a 68K, env-related protein. The 68Kenv protein was also detected on the surface of metabolically labeled BALB/cV tumor cells by an external immunoprecipitation technique. The expression of 68Kenv was restricted to mammary tissues of BALB/cV mice that also expressed other MMTV proteins. Biochemical analysis established that 68Kenv was not modified by N-linked glycosylation. 125I-labeled 68Kenv was rapidly released into the media of tumor cell cultures and was recovered both in the form of a soluble protein and in a 100,000 g pellet. The biologic function of this cell surface-expressed viral protein remains unknown.
mesh_terms: D000118:Acetylglucosaminidase; D000818:Animals; D002462:Cell Membrane / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D007106:Immune Sera; D007124:Immunoenzyme Techniques; D008325:Mammary Neoplasms, Experimental / Q000382:microbiology*; D008324:Mammary Tumor Virus, Mouse / Q000378:metabolism*; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008565:Membrane Proteins / Q000032:analysis*; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D014764:Viral Proteins / Q000032:analysis*
chemical_list: D007106:Immune Sera; D008565:Membrane Proteins; D014764:Viral Proteins; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase