Induction of calcium oscillations in human sperm by physiological concentration profiles of progesterone and nitric oxide: the role of protein S-nitrosylation and their biological significance. (360G-Wellcome-078905_Z_05_Z)

The mechanisms by which messengers from the egg cumulus complex activate humansperm to be fully competent to fertilise are a crucial aspect of male fertility. Both nitric oxide (NO) and progesterone are secreted by the cumulus and in this proposal we focus on how these two messengers are presented to sperm, how their effects converge to cause oscillations in intracellular calcium concentration and the consequences for sperm function. Our key goals are: 1) To model the concentration profiles of NO and progesterone encountered by sperm as they approach the egg to reveal the likely properties of calcium oscillations in vivo. Different NO donors and progesterone infusion rates will be used to achieve this. 2) To determine within this context if NO acts through protein S-nitrosylation and/or by activation of soluble guanylyl cyclase (sGC). S-Nitrosylation targets will beidentified by the biotin switch assay and proteomics. Specific inhibitors andactivators will be used to probe the role of sGC3) To characterise the physiological consequences of the calcium oscillations. We will concentrate on motility. A complementary package of sophisticated and innovative imaging methods will be employed to look for changes in flagellar waveform concurrent with the calcium oscillations.