Regulation of the mouse mammary tumor virus (MMTV) binding site in cultured mammary tissue.
The mouse mammary tumor virus (MMTV) initiates infection when the envelope protein, gp52, binds to a cell surface protein and triggers internalization. The hormonal regulation of this protein was studied both in vitro and in vivo. In mammary gland explant culture, levels of the MMTV binding protein were maintained only when prolactin was present in the medium. The further addition of progesterone induced levels to 164% of controls, while estradiol was without effect. These results were reproduced in ovariectomized mice which, in addition, demonstrated a need for estradiol in the maintenance of basal levels. Two growth-promoting agents were also tested in vitro: dibutyryl cAMP decreased levels to 31% of controls, while epidermal growth factor had no effect. Scatchard analyses revealed that all of these changes reflected alterations in binding protein concentration and not affinity. These results suggest that the expression of MMTV from mammary epithelium and the elevation of its binding protein are coordinated.
Bolander
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Department of Biological Sciences, University of South Carolina, Columbia 29208.
D000818:Animals; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D002478:Cells, Cultured; D004958:Estradiol / Q000502:physiology; D005260:Female; D007700:Kinetics; D008321:Mammary Glands, Animal / Q000166:cytology / Q000382:microbiology*; D008324:Mammary Tumor Virus, Mouse / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D009924:Organ Culture Techniques; D010052:Ovariectomy; D011374:Progesterone / Q000502:physiology; D011991:Receptors, Virus / Q000378:metabolism*; D014779:Virus Replication
D000957:Antigens, Viral, Tumor; D011991:Receptors, Virus; C040612:glycoprotein 52 antigen, Mouse mammary tumor virus; D011374:Progesterone; D004958:Estradiol