MARCKS REGULATES CALCIUM MOBILIZATION IN INTACT HUMAN SPERM

RODRIGUEZ PEÑA, MARCELO J.; MAYORGA, LUIS S.; MICHAUT, MARCELA A.

Potrero de los Funes, San Luis

Congreso; 47 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2011

Argentine Society for Biochemistry and Molecular Biology

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. PIP2  is  a precursor of  IP3. Our previous results, using the model of  permeabilized human sperm, indicated  that MARCKS plays a regulatory role on PIP2 concentration and, in consequence, might  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 ED-TMR 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 PIP2 concentration  in intact  human sperm.