PARTICIPATION OF CA2+ IN HUMAN SPERM CAPACITATION

BATTISTONE MA; DA ROS VG; BRUKMAN N; VISCONTI PE; CUASNICÚ PS

Chascomus

Jornada; 15a Jornadas Multidisciplinarias de la Sociedad Argentina de Biología; 2013

Recent studies from our group revealed that the increase in tyrosine (Tyr) phosphorylation during human sperm capacitation involves both PKA activation and Src family kinase (SFK)-induced inactivation of serine/threonine (Ser/Thr) phosphatases (PP1ɣ2). Considering that in the absence of extracellular Ca2+ in the capacitating medium, human sperm exhibit an increase in Tyr phosphorylation, in the present work we investigated the role of Ca2+ as a modulator of kinases and/or phosphatases. Results showed that a decrease in extracellular Ca2+ did not modify PKA substrate phosphorylation. Moreover, using specific inhibitors, we observed that the effect of the absence of Ca2+ in Tyr phosphorylation depended on the activity of Ser/Thr phosphatase PP2B and calmodulin, a Ca2+ binding protein, and occurs independently of SFK/phosphatase. In conclusion, our results support the participation of different pathways in human sperm Tyr phosphorylation: one depending on PKA activation, one involving Ser/Thr phosphatase down-regulation and one regulated by extracellular Ca2+, which cross-talk at different levels. These results will contribute to a better understanding of the molecular mechanisms involved in human sperm capacitation.