Quantitative study of testicular angiotensin-converting enzyme on the surface of human spermatozoa

Localization and Distribution of Testicular Angiotensin I Converting Enzyme (ACE) in Neck and Mid-Piece of Spermatozoa from Infertile Men in Relation to Sperm Motility

Testicular angiotensin converting enzyme (ACE) is known to play an essential role in the male reproduction and fertility. Data about tACE in cases of male infertility are quite scarce, and in this respect we aimed to study localization and distribution of tACE protein in the neck and mid-piece of spermatozoa from pathological samples in relation to sperm motility. The enzyme expression during capacitation and acrosome reaction was quantitatively assessed. In human ejaculated spermatozoa tACE is localized on sperm plasma membrane of the head, the neck and mid-piece of the tail. The immunoreactivity becomes stronger in capacitated spermatozoa followed by a decrease in acrosome reacted sperm. In different cases of semen pathology (oligozoospermia, asthenozoospermia and teratozoospermia) fluorescent signals in the neck and mid-piece are in punctate manner whereas in normozoospermia they were uniformly distributed. The expression area of tACE the neck and mid-piece was decreased in ejaculated and capacitated sperm from pathological semen samples compared to normospermia. Significant positive correlation was established between tACE area and progressive sperm motility, whereas with immotile sperm the correlation was negative. Our data suggest that proper distribution of tACE in the neck and mid-piece is required for normal sperm motility that could be used as a novel biomarker for male infertility.

Identification of lipid raft glycoproteins obtained from boar spermatozoa

The surface of the spermatozoa is coated with glycoproteins the redistribution of which during in vitro capacitation plays a key role in the subsequent fertilization process. Lipid rafts are membrane microdomains involved in signal transduction through receptors and include or recruit specific types of proteins and glycoproteins. Few studies have focused on identifying glycoproteins resident in the lipid rafts of spermatozoa. Proteins associated with lipid rafts modify their localization during capacitation. The objective of the study was to identify the glycoproteins associated with lipid rafts of capacitated boar spermatozoa through a lectin-binding assay coupled to mass spectrometry approach. From the proteomic profiles generated by the raft proteins extractions, we observed that after capacitation the intensity of some bands increased while that of others decreased. To determine whether the proteins obtained from lipid rafts are glycosylated, lectin blot assays were performed. Protein bands with a good resolution and showing significant glycosylation modifications after capacitation were analyzed by mass spectrometry. The bands of interest had an apparent molecular weight of 64, 45, 36, 34, 24, 18 and 15 kDa. We sequenced the 7 bands and 20 known or potential glycoproteins were identified. According to us, for ten of them this is the first time that their association with sperm lipid rafts is described (ADAM5, SPMI, SPACA1, Seminal plasma protein pB1, PSP-I, MFGE8, tACE, PGK2, SUCLA2, MDH1). Moreover, LYDP4, SPAM-1, HSP60, ZPBP1, AK1 were previously reported in lipid rafts of mouse and human spermatozoa but not in boar spermatozoa. We also found and confirmed the presence of ACR, ACRBP, AWN, AQN3 and PRDX5 in lipid rafts of boar spermatozoa. This paper provides an overview of the glycosylation pattern in lipid rafts of boar spermatozoa before and after capacitation. Further glycomic analysis is needed to determine the type and the variation of glycan chains of the lipid rafts glycoproteins on the surface of spermatozoa during capacitation and acrosome reaction.