Ceramide promotes intracellular calcium increase in human sperm and triggers the exocytosis of the acrosome

VAQUER, CINTIA C; PACHECO GUIÑAZÚ, ANAHI B; SUHAIMAN, LAILA; DE BLAS, GERARDO A; BELMONTE, SILVIA A

Con Con

Congreso; 29a Reunión Anual Sociedad Chilena de Reproducción y Desarrollo; 2018

Sociedad Chilena de Reproducción y Desarrollo

Theacrosome is a membrane-limited granule that overlies the sperm nucleus. Inresponse to physiological stimuli, sperm undergo a calcium-dependent exocytosisof this granule termed: acrosome reaction (AR). Ceramide´s role in exocytosisis not well defined, since it´s been shown that in some cases it positivelyregulates membrane fusion while in others has the opposite effect. Also, is notwell characterized if its effects on secretion are exerted by itself or byrelated metabolites. We evaluated the role of ceramide and its metabolites inthe AR by using biochemical and exocytosis assays. WB and IFI analysisdemonstrated the presence of enzymes of the sphingolipid metabolism in humansperm. Both, C6-ceramide (C6-Cer) treatment or endogenous ceramide increaseinduce AR in capacitated sperm in a percentage similar to progesterone. Humansperm loaded with Fluo3-AM, a calcium sensor, responded to C6-Cer with atransient increase in calcium concentration whose profile was similar to thatelicited by progesterone. Furthermore, ceramide increase promotes calciummobilization from internal stores (ryanodine receptors) however it requiresextracellular calcium influx through SOCCs to accomplish acrosome release. Theceramide or progesterone-elicited AR was inhibited by NVP-231, a ceramidekinase blocker, indicating that both inducers require ceramide 1-phosphate(C1P) in the pathway leading to AR. Further, the inhibition was reverted byadding C1P. These findings led us to the conclusion that probably C1P isregulating AR after a ceramide increase. Here, we identified ceramide and C1Pas novel molecules integrated in a signaling cascade leading to membrane fusionduring acrosomal exocytosis