Segregation of steroid receptor coactivator-1 from steroid receptors in mammary epithelium.
Steroid receptor coactivator-1 (SRC-1) family members interact with steroid receptors, including estrogen receptor alpha (ERalpha) and progesterone receptor (PR), to enhance ligand-dependent transcription. However, the expression of ERalpha and SRC-1 was found to be segregated in distinct subsets of cells within the epithelium of the estrogen-responsive rat mammary gland. This finding was in contrast to the finding for the stroma, where significant numbers of cells coexpressed ERalpha and SRC-1. Treatment of animals with estrogen induced PR expression in the ERalpha-expressing mammary epithelial cells in the absence of detectable SRC-1 and did not affect the segregated pattern of SRC-1 and ERalpha expression. PR was neither expressed nor induced by estrogen treatment in stroma, despite the coexpression of ERalpha and SRC-1. These results suggest that SRC-1 is not necessary for ERalpha-mediated induction of PR in mammary epithelial cells and is also not sufficient for PR induction in stromal cells expressing both ERalpha and SRC-1. Furthermore, the expression of SRC-1 in a subpopulation of mammary epithelial cells distinct from those expressing ERalpha or PR raises the possibility that SRC-1 has cell type-specific functions other than simply to act as coactivator for ERalpha or PR in the mammary epithelium.
Shim
W S
WS
Department of Internal Medicine, Division of Hematology/Oncology, University of Virginia Health Sciences Center, Charlottesville, VA 22908, USA.
DiRenzo
J
J
DeCaprio
J A
JA
Santen
R J
RJ
Brown
M
M
Jeng
M H
MH
D000818:Animals; D004847:Epithelial Cells / Q000737:chemistry; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D051548:Histone Acetyltransferases; D007150:Immunohistochemistry; D008321:Mammary Glands, Animal / Q000737:chemistry* / Q000187:drug effects; D056920:Nuclear Receptor Coactivator 1; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000302:isolation & purification; D011980:Receptors, Progesterone / Q000302:isolation & purification; D011987:Receptors, Steroid / Q000302:isolation & purification*; D017154:Stromal Cells / Q000737:chemistry; D014157:Transcription Factors / Q000302:isolation & purification*
D004967:Estrogens; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D011987:Receptors, Steroid; D014157:Transcription Factors; D051548:Histone Acetyltransferases; D056920:Nuclear Receptor Coactivator 1