Increase hyperactivation and protein tyrosine phosphorylation in human sperm incubated at higher temperature during capacitation

PUGA MOLINA LC; LA SPINA F; TREVIÑO C; TORRES NI; MATAMOROS-VOLANTE A; BUFFONE MG; LUQUE GM; ROMAROWSKI A; HERRERA-RODRIGUEZ F

rehovot

Congreso; The Batsheva de Rothschild Seminar on Challenges and Frontiers in Mammalian Reproduction; 2016

Sperm acquire the ability to fertilize in the female genital tract in a process called capacitation. From a molecular point of view, bicarbonate and calcium-dependent activation of the soluble adenylyl cyclase and the subsequent activation of a cAMP-dependent pathway lead to a PKA-dependent increase in protein tyrosine phosphorylation. During capacitation sperm undergo a change in the motility pattern called hyperactivation which is characterized by asymmetrical flagelar beating and it is critical to fertilization. The increase in intracellular calcium concentration through the sperm-specific CatSper ion channels is crucial for hyperactivation. In preliminary results we observed that human sperm incubated under capacitating conditions but at higher temperature displayed a strong increase in percentage of hyperactivated cells. Using CASA we measured that sperm incubated at 40°C significantly increased the percentage of hyperactivation from 30 min of capacitation onwards, in comparison with those incubated at 37°C. We also observed that the capacitation-associated increase in protein tyrosine phosphorylation (pY) occurs within the first hour of incubation which is strikingly different to what it is usually observed in human sperm. The addition of inhibitors of cAMP/PKA pathway completely abolished this increment. Due to the existence of other ion channels that are sensitive to changes in temperature, like the TRP (Transient receptor potential) family which are considered to be polymodal cellular sensors, we used a pharmacological approach to determine the participation of TRPV1 channels in this event. By using a specific agonist of TRPV1 at 37°C, we detected that hyperactivation is induced at similar levels to those obtain with 40°C without agonist. On the other hand, incubation of sperm at 40°C with TRPV1 antagonist resulted in a decrease in hyperactivated cells compared to 40°C only. All together, these results suggest that hyperactivation induced by temperature is related with an activation of TRPV1 channels.