Differential expression of p160 steroid receptor coactivators in the rat testis and epididymis.
OBJECTIVE
Androgens are critical for the development and maintenance of male sexual characteristics. Their action is mediated through the androgen receptor (AR). Ligand-bound AR interacts with coactivator proteins that mediate transcriptional activation. Such coactivators include three members of the 160 kDa proteins (p160s): SRC-1, TIF2/GRIP1, and p/CIP/RAC3/ACTR/AIB1/TRAM-1. The aim of this study was to investigate the expression of the three p160 coactivators and their association with AR in testis and epididymis.


METHODS
We determined the localization of these three p160 coactivators in immature and mature rat testis, and epididymis by immunohistochemistry using the specific monoclonal antibodies. We also performed double immunofluorescence staining to examine whether p160s are colocalized with AR in these tissues.


RESULTS
In seminiferous tubules of mature rat testis, SRC-1 and TRAM-1 immunoreactivity was found predominantly in spermatogonia and spermatocytes. In contrast, TIF2 was expressed predominantly in Sertoli cells. AR was coexpressed with TIF2 in this cell type. In immature rat testis, however, all three coactivators were expressed in both germ cells and Sertoli cells. In the epididymis, SRC-1 and TIF2 immunoreactivities were localized in nuclei of epithelial cells. However, TRAM-1 immunostaining was observed in the luminal portion of the cytoplasm with greater intensity than in the nucleus, especially in the caput epididymidis.


CONCLUSIONS
The cell-type-specific expression of p160 coactivators suggests specific roles in male reproductive organs. Further, the strong cytoplasmic localization of TRAM-1 protein in epithelial cells of epididymis suggests that TRAM-1 may have additional role(s) in transcriptional regulation.
Igarashi-Migitaka
Junko
J
Department of Anatomy and Cell Biology, St Marianna University School of Medicine, Kawasaki, Kanagawa 216-8511, Japan.
Takeshita
Akira
A
Koibuchi
Noriyuki
N
Yamada
Shozo
S
Ohtani-Kaneko
Ritsuko
R
Hirata
Kazuaki
K
D000375:Aging / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D002460:Cell Line; D004822:Epididymis / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D051548:Histone Acetyltransferases; D007150:Immunohistochemistry; D008297:Male; D056920:Nuclear Receptor Coactivator 1; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism*; D056921:Nuclear Receptor Coactivator 3; D051381:Rats; D017207:Rats, Sprague-Dawley; D011944:Receptors, Androgen / Q000378:metabolism; D013737:Testis / Q000378:metabolism*; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism*
D000911:Antibodies, Monoclonal; C498003:Ncoa2 protein, rat; D051958:Nuclear Receptor Coactivator 2; D011944:Receptors, Androgen; D014157:Transcription Factors; D051548:Histone Acetyltransferases; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3