The pair ceramide-1-phosphate/ceramide kinase regulates intracellular calcium concentration during sperm exocytosis

VAQUER, CINTIA CELINA; SUHAIMAN, LAILA; PAVAROTTI MARTÍN A; DE BLAS, GERARDO ANDRÉS; BELMONTE, SILVIA ALEJANDRA

Mendoza

Congreso; LVII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2023

SAIB

Before fertilization, spermatozoa must undergo calcium-regulated acrosome exocytosis in response to physiological stimuli such as progesterone and zona pellucida. Our laboratory has elucidated the signaling cascades accomplished by different sphingolipids during human sperm exocytosis. Recently, we established that ceramide increases intracellular calcium by activating different channels and stimulating sperm exocytosis. However, whether ceramide induces exocytosis on its own, activation of the CerK/C1P pathway, or both is still an unsolved issue. Here, by using functional assays, we demonstrate that C1P addition induces exocytosis in intact, capacitated human sperm. Real-time imaging in single-cell and calcium measurements in sperm population show that C1P needs extracellular calcium to induce intracellular calcium increase. The sphingolipid triggers cation-influx through Catsper, VOC, and SOC channels. However, requires calcium efflux from internal stores through IP3R and RyR to achieve sperm secretion. For the first time, we report the presence of the ceramide kinase (CerK) in spermatozoa, the enzyme that catalyzes C1P synthesis. Furthermore, CerK exhibited calcium-stimulated enzymatic activity during sperm secretion. Exocytosis assays using a CerK inhibitor demonstrate that ceramide induces sperm exocytosis, partly due to C1P synthesis. Importantly, progesterone requires C1P to trigger the acrosome exocytosis. This is the first report, implicating the bioactive sphingolipid C1P in the physiological pathway of the sperm acrosome reaction.