Estrogen receptors alpha and beta (ERalpha and ERbeta) and androgen receptor (AR) in human sperm: localization of ERbeta and AR in mitochondria of the midpiece.
BACKGROUND
The central role of estrogens and androgens in the male reproductive system has focused attention on the presence and distribution of their cognate receptors [estrogen receptor (ER) alpha, ERbeta and androgen receptor (AR)] in male reproductive tissues and cells. Since the presence of steroid hormone receptors in mitochondria of mammalian cells has been well documented, we investigated the possibility of mitochondrial localization of sex steroid hormone receptors in sperm.


RESULTS
Applying immunofluorescence labelling and confocal laser scanning microscopy we show that the estrogen receptor beta and the AR of human sperm are specifically enriched in the midpiece, at the site of the mitochondria, which were visualized by labelling with the vital dye CMX. Nuclear and mitochondrial localization of AR was also detected in LnCap human prostate cancer cells. Differentially, most of the ERalpha immunostaining is in the form of a compact zone at a region corresponding to the equatorial segment of the upper post-acrosomal region of the sperm head. Immunoblotting experiments using sperm extracts revealed the presence of a 66 and a 45 kDa protein reacting with the ERalpha antibody, one 64 kDa protein reacting with the ERbeta antibody and a 110 and a 90 kDa protein reacting with the antibody against AR.


CONCLUSIONS
Our findings suggest that the differential localization of AR and ER isoforms in human sperm reveals distinct roles of these receptors in the physiology of sperm cells and, perhaps, also in the process of fertilization.
Solakidi
S
S
National Hellenic Research Foundation, Institute of Biological Research and Biotechnology, Laboratory of Molecular Endocrinology, 48 Vas Constantinou Ave, 11635 Athens, Greece.
Psarra
A-M G
AM
Nikolaropoulos
S
S
Sekeris
C E
CE
D015153:Blotting, Western; D045744:Cell Line, Tumor; D047628:Estrogen Receptor alpha / Q000096:biosynthesis*; D047629:Estrogen Receptor beta / Q000096:biosynthesis*; D005306:Fertilization; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D009930:Organic Chemicals / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000473:pathology; D020033:Protein Isoforms; D011944:Receptors, Androgen / Q000096:biosynthesis*; D012984:Software; D013094:Spermatozoa / Q000378:metabolism* / Q000473:pathology
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005456:Fluorescent Dyes; D009930:Organic Chemicals; D020033:Protein Isoforms; D011944:Receptors, Androgen; C107472:red dye CMXRos