The Pair Ceramide 1-phosphate/Ceramide Kinase Regulates Intracellular Calcium and Progesterone-induced Human Sperm Acrosomal Exocytosis

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

Frontiers in Cell and Development

Frontiers Media

Año: 2023

Before fertilization, spermatozoa must undergo calcium-regulated acrosomeexocytosis in response to physiological stimuli such as progesterone and zonapellucida. Our laboratory has elucidated the signaling cascades accomplished bydifferent sphingolipids during human sperm acrosomal exocytosis. Recently, weestablished that ceramide increases intracellular calcium by activating variouschannels and stimulating the acrosome reaction. However, whether ceramideinduces exocytosis on its own, activation of the ceramide kinase/ceramide 1-phosphate (CERK/C1P) pathway or both is still an unsolved issue. Here, wedemonstrate that C1P addition induces exocytosis in intact, capacitated humansperm. Real-time imaging in single-cell and calcium measurements in spermpopulation showed that C1P needs extracellular calcium to induce [Ca2+]iincrease. The sphingolipid triggered the cation influx through voltage-operatedcalcium (VOC) and store-operated calcium (SOC) channels. However, it requirescalcium efflux from internal stores through inositol 3-phosphate receptors (IP3R)and ryanodine receptors (RyR) to achieve calcium rise and the acrosome reaction.We report the presence of the CERK in human spermatozoa, the enzyme thatcatalyzes C1P synthesis. Furthermore, CERK exhibited calcium-stimulatedenzymatic activity during the acrosome reaction. Exocytosis assays using aCERK inhibitor demonstrated that ceramide induces acrosomal exocytosis,mainly due to C1P synthesis. Strikingly, progesterone required CERK activity toinduce intracellular calcium increase and acrosome exocytosis. This is the firstreport, implicating the bioactive sphingolipid C1P in the physiologicalprogesterone pathway leading to the sperm acrosome reaction.