The expression of the new epididymal luminal protein of PDZ domain containing 1 is decreased in asthenozoospermia

Spermatozoa are not mature until they transit the epididymis where they acquire motility and the ability to fertilize an egg through sequential modifications. The epididymis has three functional regions, caput, corpus, and cauda, and the luminal proteins of the epididymis play important roles in the above modifications. However, the proteins with differential enrichment between the caput and cauda are still largely unknown. To reveal the functions of the caput and cauda during sperm maturation, luminal proteins from caput and cauda of mice were analyzed by isobaric tag for relative and absolute quantitation （iTRAQ）. Overall, 128 differentially enriched proteins were found, of which 46 were caput enriched and 82 were cauda enriched. Bioinformatic analysis showed that lipid metabolism was active in the caput; while anion- and cation-binding activity and phosphorus and organophosphate metabolism were active in the cauda. A new epididymal luminal protein, the caput-enriched PDZ domain containing 1 （Pdzkl）, also named Na^＋/H^＋ exchange regulatory cofactor 3 （NHERF3）, which plays a critical role in cholesterol metabolism and carnitine transport, was found in the lipid metabolism. Western blotting and immunofluorescence analyses showed that Pdzkl was expressed in the epididymis but not in the testis, and localized at the middle piece of the sperm tail. Pdzkl protein level was also reduced in the spermatozoa in case of asthenozoospermic patients compared with that in normozoospermic men, suggesting that Pdzkl may participate in sperm maturation regulation and may be associated with male infertility. These results may provide new insights into the mechanisms of sperm maturation and male infertility.

Extracellular Vesicles in Mouse Testes Elevate the Level of Serum Testosterone

Objective:Testosterone plays an essential role in maintaining spermatogenesis and male fertility,and the primary known source of testosterone is testicular Leydig cells,which are regulated by luteinizing hormone(LH).However,whether any other ways of testosterone secretion exist still remains unknown.Methods:Transmission electron microscopy was used to detect testicular extracellular vesicles(EVs),which were isolated by an ultracentrifuge process.Separately,the concentrations of follicle-stimulating hormone(FSH),LH,and testosterone were measured by enzyme-linked immunosorbent assay.Results:Some EVs were found by tail vein injection to be present in mouse testes that elevate the circulating testosterone and LH levels in the blood,but do not affect FSH.Separately,they also promote testosterone production in the TM3 Leydig cell line in vitro.To determine whether the EVs from spermatogonia were involved in the secretion of testosterone,we used spermatogonial stem/progenitor cell line C18-4 cells and revealed that C18-4 cells promote production of testosterone in the TM3 Leydig cell line using the EVs.Conclusions:EVs in mouse testes likely originate from spermatogonia and involved in the regulation of the serum testosterone.Our results provide a new mechanism for the regulation of testosterone production.