[Capacitation and acrosome reaction are associated with changes in sialic acid location and head morphometry in human sperm]

Characterization of Human Spermatic Subpopulations by ConA-Binding Sites and Tyrosine Phosphorylation during in vitro Capacitation and Acrosome Reaction

Spermatozoa capacitation is a time-dependent physiological process essential for acquiring the fertilizing capacity. In this context, reorganization of spermatozoa surface sugars and tyrosine phosphorylation are some of the most important biochemical changes involved in capacitation. However, the relationship between these 2 biomarkers remains poorly defined. By cytofluorescence we simultaneously characterized the head concanavalin A (ConA)-binding sites and the flagellar tyrosine phosphorylation before capacitation, during different capacitation times (1 and 4 h), and after acrosome reaction induction in human spermatozoa. The results showed a strong connection between ConA-label patterns and tyrosine phosphorylation according to the spermatozoa capacitation time and acrosomal status. Specifically, the spermatozoa subpopulation with phosphotyrosine presented proper sugar location (label in acrosomal and postacrosomal region) just after 1 h of capacitation, while cells without phosphotyrosine needed 4 h to do it. Moreover, after induction of spermatozoa acrosome reaction, phosphorylation was significantly correlated (p < 0.05) with the relocation of ConA-binding residues to the equatorial region, regardless of capacitation time. Overall, these observations provide novel insights regarding spermatozoa subpopulations based on essential physiological events like capacitation and acrosome reaction, which could have potential implications in the improvement of spermatozoa selection techniques.