MARCKS regulates calcium mobilization in intact human sperm.

RODRÍGUEZ PEÑA MJ, MAYORGA LS, MICHAUT MA

Potrero de los Funes

Congreso; SAIB; 2011

SAIB

Acrosomal exocytosis (AE) is a regulated Ca2+-dependent secretion event required for sperm-egg interaction. To achieve this exocytosis, a Ca2+ efflux from the acrosome is required. This calcium mobilization is activated by IP -sensitive channels. PIP is 3 2 a precursor of IP Our previous results, using the model of 3. permeabilized human sperm, indicated that MARCKS plays a regulatory role on PIP concentration and, in consequence, might 2 also regulate Ca2+ mobilization from the acrosome. To test this hypothesis in a more physiological model, we used intact human sperm and AE was stimulated by calcium ionophore and progesterone. To analyze MARCKS function in intact sperm, we assayed the commercial MARCKS peptide corresponding to the effector domain conjugated with rhodamine (ED-TMR). The EDTMR is a polybasic peptide and it has been described as a permeable peptide. Our results showed that ED-TMR peptide was able to translocate into intact sperm and inhibit the AE stimulated by A23187 and progesterone in a concentration-dependent manner. When calcium mobilization was assayed by spectrofluorometry, the preincubation of human sperm with ED-TMR abolished the increase in calcium levels caused by progesterone. Altogether, these results validate the hypothesis that MARCKS regulates Ca2+ mobilization through the regulation of PIP concentration in intact 2 human sperm.