Cathepsin D in Human Reproductive Tissues: Cellular Localization in Testis and Epididymis and Surface Distribution in Different Sperm Conditions

Abstract

Mammalian sperm surface antigens are acquired either during spermatogenesis or sperm maturation in the epididymis. These antigens, many of which are hydrolytic enzymes, are actively synthesized and secreted by the resident epithelial cells and adsorbed to the sperm membrane as part of posttesticular sperm modification. In this study, we aimed to investigate the expression of cathepsin-D (CAT-D) in human reproductive tissues and its distribution on the sperm surface in different sperm conditions. Immunohistochemical results revealed the expression of CAT-D in the somatic Sertoli and Leydig cells without showing any immunoreactivity in any germ cells, despite their engagement of the acrosomal system. A strong immunoreactivity of anti-CAT-D was also detected in the epididymal epithelium, chiefly in the principal cells, which are known to actively synthesize and secrete proteins into the epididymal lumen. The absence of CAT-D in the clear cells was unexpected because these cells are known to engage the endosomal machinery. We further showed that CAT-D was anchored on the sperm surface confined to the postacrosomal region without any lateral redistribution within the membrane during sperm capacitation. However, the enzyme underwent changes to be an active form of a 29/30-kd doublet during sperm capacitation. Using CAT-D as a marker, we were able to demonstrate here localization of the enzyme in human reproductive tissues, as well as reveal membrane modification in human sperm during maturation and capacitation processes.

Proteomic Analysis of Chinook Salmon (Oncorhynchus tshawytscha) Ovarian Fluid

“…Cathepsin D is detected on the sperm surface in humans and undergoes modification to an active form during capacitation [60], in which process it likely plays an important role in the conversion of proacrosine to acrosin [61]. Cathepsin D concentrations in cauda epididymis fluid also correlate strongly with fertility scores of cattle [62], but cathepsin D concentrations in seminal plasma showed no clear relationship with sperm count and morphology in humans [63].…”

Cathepsin D in prawn reproductive system: its localization and function in actin degradation

“…3C, 3D) with the band density of about 1.7-2. 7× 10 3 arbitrary units suggesting self-biogenesis of MrCAT-D transcripts by developing germ cells in the testis which was rather different from mouse and human cases reported earlier (Saewu et al, 2012;Asuvapongpatana et al, 2013). The single 212-bp β-actin band, as internal controls, was evenly distributed in all tissues studied confirming an equal amount of RNA loaded in each tissue.…”

“…For substrate interaction, CAT-D requires hydrophobic amino acid cluster at the cleavage site (P1 and P1 positions) and substrate preference P2 site, whereas, the polar amino acid is of preference at the P2 position (Pimenta et al, 2001). In the reproductive system, we have reported its existence in mammalian male reproductive tissues and its surface localization which is acquired from its adsorption from epididymal fluid as part of sperm maturation process (Asuvapongpatana et al, 2013;Saewu et al, 2012). In a few original works of mammalian reproductions, the unique localization of CAT-D as a cell-or region-specific fashion has been revealed in testis and epididymis (Igdoura, Morales & Hermo, 1995;Hermo & Andonian, 2003), despite the fact that CAT-D is abundantly detected in the lysosomes of all somatic cells (Benes, Vetvicka & Fusek, 2008;Masson et al, 2010).…”

“…In a few original works of mammalian reproductions, the unique localization of CAT-D as a cell-or region-specific fashion has been revealed in testis and epididymis (Igdoura, Morales & Hermo, 1995;Hermo & Andonian, 2003), despite the fact that CAT-D is abundantly detected in the lysosomes of all somatic cells (Benes, Vetvicka & Fusek, 2008;Masson et al, 2010). In testis, CAT-D is specifically localized in lysosomes of Sertoli cells, while it has not been detected in spermatogenic cells, particularly acrosome which is physiologically homologous to lysosomes (Huo et al, 2008;Asuvapongpatana et al, 2013;Saewu et al, 2012). It has been proposed functionally that hydrolytic proteases in Sertoli cell cytoplasm such as cathepsins and other serine proteases exert their function to cleave integrin-ECM interaction to release testicular sperm into the adluminal compartment (Yanagimachi, 1994;Cheng & Mruk, 2011) .…”

Leveraging Comparative Genomics to Identify and Functionally Characterize Genes Associated with Sperm Phenotypes inPython bivittatus(Burmese Python)

“…Similar results have been observed in humans. For example, cathepsin D expression has been observed in human Sertoli cells and Leydig cells and was shown to be anchored to the sperm surface in the postacrosomal region [ 64 ]. Evidence that cathepsin D may exhibit an evolutionarily conserved role in sperm physiology comes from a recent study in which cathepsin D was identified as a seminal plasma protein in carp [ 65 ].…”