Ceramide 1-phosphate promotes intracellular calcium increase and acrosomal exocytosis in human sperm

VAQUER, CINTIA C; SUHAIMAN, LAILA; PELLETÁN, LEONARDO E; BELMONTE, SILVIA A

Rosario

Congreso; L Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2014

SAIB

The acrosome is a large membrane-limited granule that overlies the sperm nucleus. In response to physiological stimuli, sperm undergo exocytosis of this granule termed the acrosome reaction (AR). Ceramide´s role in exocitosis is still in discussion, since it´s been reported that in some systems it positively regulates membrane fusion while in others has the opposite effect. Here, by using biochemical and exocytosis assays we evaluated the role of ceramide and its metabolites in our model. Western blot analysis of sperm extracts showed the presence of enzymes of the sphingolipid metabolism such as neutral and alkaline ceramidase, and neutral sphingomyelinase. Measurements of AR by flow cytometry demonstrated that C6-ceramide induces exocytosis. Using a ceramidase inhibitor, in order to increase endogenous ceramide levels, resulted in an induction of the AR. Exocytosis and biochemical assays led us to the conclusion that probably ceramide 1-phosphate (C1P) is regulating AR after a ceramide increase. Human sperm loaded with Fluo3-AM, a fluorescent calcium sensor, responded bothe to C6-ceramide and C1P with a transient increase in calcium concentration whose profile were similar to that elicited by progesterone. Further, C1P triggered exocitosis as efficiently as progesterone. Here, we identified C1P as a possible mediator of membrane fusion during acrosomal exocytosis.