MAYORGA Luis Segundo
congresos y reuniones científicas
Ceramide regulates acrosomal exocytosis in human sperm.
VAQUER, CC; SUHAIMAN, L; PELLETÁN, LE; MAYORGA LS; BELMONTE SA
Congreso; SAIB 48º; 2012
Sphingolipid metabolism involves multiple metabolic steps that constitute a complex network. Ceramide is a metabolic hub because is generated either via de novo pathway or the sphingomyelin and it occupies a central position in sphingolipid biosynthesis and catabolism. Ceramide positively regulates membrane fusion in some biological systems even though has the opposite effect in other cell types. Regulated secretion is a central issue; for instance, mammalian sperm acrosomal exocytosis (AE) is essential for egg fertilization. Since we demonstrated that sphingosine-1-phosphate, an almost immediate product of ceramide breakdown, induces AE we wondered if ceramide has any effect on exocitosis and if it is so whether it is produced by itself or through the synthesis of bioactive lipids. By using Western blot of sperm extracts, we found a ~84 kDa band corresponding to neutral ceramidase, a hydrolase that removes the fatty acyl groups from ceramides at neutral pH. It binds to sperm membranes in a calcium independent manner. The alkaline ceramidase (~31 kDa), was also present in human sperm. Neutral sphingomyelinase, which generates ceramide, is present in sperm extracts (~48 kDa). Functional assays demonstrated ceramide regulation of AE. Here, we present the first piece of evidence indicating the presence of sphingolipids metabolism enzymes in human sperm and the importance of ceramides inAE.