No abstract

Efferent ductules and epididymis are involved in water and solute transport, which is indispensable for storage and maintenance of the sperm viability. The reabsorption process involves proteins such as aquaporins (AQP), which has been described in the male genital system of limited species, including primate, rodents, cats and dogs. To contribute with information about AQPs in the male system, here we investigated the distribution of AQP1 and AQP9 in the tropical bat Artibeus lituratus, along the annual reproductive cycle. A. lituratus is a seasonal breeder with natural variation in components of the androgen and estrogen responsive system, thus being a good model for exploring the AQPs modulation. AQP1 was found restricted to differentiating spermatids, efferent ductules epithelium and venular endothelia along the male tract. AQP9 was detected throughout the epididymis being more abundant in the cauda and ductus deferens, but was not found in testis, rete testis and efferent ductules. Contrasting with AQP1 which appear to be constitutively expressed, there was seasonal variation in AQP9 expression, which was reduced in regressed epididymis. The AQP9 does not appear to be modulated by estradiol or androgens, but possibly by other factor related to luminal sperm. The establishment of specific function for aquaporins in the male tract remains undetermined; however, the cellular distribution presently found are compatible with the main function of AQP1, as a selective water channel, and AQP9, which is a conduct for water and a plethora of neutral solutes present in the epididymis milieu such as glycerol and urea.

Background: The Hermes body (HB) previously called the cytoplasmic droplet is a focal distension of the flagellar cytoplasm of epididymal spermatozoa consisting mainly of isolated flattened Golgi cisternae. Objective: To define a functional role for the HB of epididymal spermatozoa. Methods: Isolated fractions of HBs of epididymal spermatozoa were prepared and by quantitative tandem mass spectrometry revealed 1511 proteins. Results: The glucose transporter GLUT-3 was the most abundant protein followed by hexokinase 1, which along with the presence of all glycolytic enzymes suggested a role for the HB in glycolysis. Several TMED/p24 Golgi trafficking proteins were abundant with TMED7/p27 and TMED2/p24 defining the identity of the flattened cisternae within the HB as Golgi, along with the known Golgi proteins, GBF1, GOLPH3, Man2a1, and ManIIX. The Golgi trafficking protein TMED7/p27 via small 50-nm vesicles emanating from the Golgi cisternae was proposed to transport GLUT-3 to the plasma membrane for ATP production related to sperm motility. The internal membranes revealed abundant proteins not only of Golgi cisternae, but also of endoplasmic reticulum and endosomes. COPI and COPII coats, clathrin, SNAREs, annexins, atlastins, and GTPases were identified for vesicular trafficking and membrane fusion, in addition to ribosomes, stress proteins for protection, proteasome proteins involved in degradation, and cytoskeletal elements for migration of the HB along the flagellum. The biogenesis of the HB occurring at step 19 spermatids of the testis just prior to their release was uncovered as a key step in germ cell differentiation, where several proteins were expressed, some for the first time. Conclusion: As epididymal spermatozoa undergo remodeling of their protein makeup through selective degradation of sperm proteins during epididymal transit, then remodeling as a consequence of new protein synthesis is not excluded by our observations.

Seminiferous tubules of the testis and epididymal tubules in adult rodents are enveloped by contractile myoid cells, which move sperm and fluids along the male reproductive tract. Myoid cells in the testis influence Sertoli cells by paracrine signaling, but their role in the epididymis is unknown. Electron microscopy revealed that elongated myoid cells formed several concentric layers arranged in a loose configuration. The edges of some myoid cells in a given layer closely approximated one another, and extended small foot-like processes to cells of overlying layers. Gap junction proteins, connexins 32 and 43, were detected within the myoid cell layers by immunohistochemistry. These myoid cells also had caveolae that contained caveolin-1 and cavin-1 (also known as PTRF). The number of caveolae per unit area of plasma membrane was significantly reduced in caveolin-1-deficient mice (Cav1(-/-) ). Morphometric analyses of Cav1-null testes revealed an enlargement in whole-tubule and epithelial profile areas, whereas these parameters were slightly reduced in the epididymis. Although sperm are non-motile as they pass through the proximal epididymis, statistical analyses of cauda epididymidis sperm concentrations revealed no significant differences between wild-type and Cav1(-/-) mice. Motility analyses, however, indicated that sperm velocity parameters were reduced while beat cross frequency was higher in gametes of Cav1(-/-) mice. Thus while caveolae and their associated proteins are not necessary for myoid cell contractility, they appear to be crucial for signaling with the epididymal epithelium to regulate the proper acquisition of sperm motility. Mol. Reprod. Dev. 83: 526-540, 2016. © 2016 Wiley Periodicals, Inc.

GCN2 (general control nonderepressible 2) is a serine/threonine-protein kinase that controls messenger RNA translation in response to amino acid availability and ribosome stalling. Here, we show that GCN2 controls erythrocyte clearance and iron recycling during stress. Our data highlight the importance of liver macrophages as the primary cell type mediating these effects. During different stress conditions, such as hemolysis, amino acid deficiency or hypoxia, GCN2 knockout ( GCN2 −/− ) mice displayed resistance to anemia compared with wild-type ( GCN2 +/+ ) mice. GCN2 −/− liver macrophages exhibited defective erythrophagocytosis and lysosome maturation. Molecular analysis of GCN2 −/− cells demonstrated that the ATF4-NRF2 pathway is a critical downstream mediator of GCN2 in regulating red blood cell clearance and iron recycling.