UC Riverside

Biomechanical operation of axonemal dynein motors requires high ATP concentrations; however, the source of this high-energy molecule was not yet known in sperm of the viral vector mosquito, Culex pipiens. Proteomic analysis of Culex sperm identified glycogen phosphorylase, ATP synthase beta subunit, and arginine kinase as relatively abundant. Quantification of glycogen consumption following sperm activation by trypsin revealed an increase in catabolism from aerobic to anaerobic respiration. A glycogen phosphorylase inhibitor reduced glycogen consumption in a dose-dependent manor, but its effect on sperm velocity was complex. Inhibition of glycolysis significantly reduced velocity at all time points and extracellular glucose was not necessary until 10 minutes. Inhibition of the electron transport chain also significantly reduced velocity at all time points without a significant difference upon extracellular glucose removal. Arginine kinase inhibition produced significant velocity reduction after 10 minutes. Additionally, extracellular calcium was confirmed to be both necessary and sufficient for sustained flagellar motility—and forward sperm velocity robustly increased at 2 minutes when a membrane-permeant cAMP derivative was introduced. These results suggest that trypsin activation of Culex sperm requires the mobilization of glycogen stores for aerobic respiration providing the energy necessary for axonemal function.