Human sperm phosphoproteome reveals differential phosphoprotein signatures that regulate human sperm motility.J Proteomics 2020; 215:103654JP
Human sperm motility is essential for fertilization and among pathologies underlying male infertility is asthenozoospermia. Nevertheless, mechanisms regulating sperm motility are not completely unraveled. This work investigates phosphoproteins underlying human sperm motility by using differential phosphoproteomic in two human sperm subpopulations: high (HM) and low (LM) motility, obtained by centrifugation in a density gradient. Phosphoproteomics (HPLC-MS/MS triple TOF), comparing human LM and HM phosphoproteomes, identified 210 phosphopeptides with different abundance that correspond with 119 sperm proteins. Analysis showed that 40% of phosphoproteins in LM spermatozoa are involved in metabolism, (catabolism, protein transport, lipid biosynthesis), 25% in spermatogenesis and sperm function, 8% in immune system and 6% in DNA repair. In HM spermatozoa, 48% of phosphoproteins are related to spermatogenesis and sperm function (motility), whereas 8% are associated to metabolism. GSK3α resulted one of the most abundant phosphoproteins in HM spermatozoa. Western blot confirmed that GSK3α phosphorylation is higher in HM spermatozoa. Summarizing, this study i) identified phosphoproteins in two human spermatozoa populations, ii) supports that human spermatozoa rely in protein phosphorylation, such as GSK3 α, to regulate sperm motility, iv) raises the challenge of using some identified human sperm phosphorylated proteins (GSK3α) as targets to develop into clinically relevant biomarkers.