Acetylproteomic Analysis Reveals Functional Implications of Lysine Acetylation in Human Spermatozoa (sperm)

Abstract

Male infertility is a medical condition that has been on the rise globally. Lysine acetylation of human sperm, an essential posttranslational modification involved in the etiology of sperm abnormality, is not fully understood. Therefore, we first generated a qualified pan-anti-acetyllysine monoclonal antibody to characterize the global lysine acetylation of uncapacitated normal human sperm with a proteomics approach. With high enrichment ratios that were up to 31%, 973 lysine-acetylated sites that matched to 456 human sperm proteins, including 671 novel lysine acetylation sites and 205 novel lysine-acetylated proteins, were identified. These proteins exhibited conserved motifs XXXKYXXX, XXXKFXXX, and XXXKHXXX, were annotated to function in multiple metabolic processes, and were localized predominantly in the mitochondrion and cytoplasmic fractions. Between the uncapacitated and capacitated sperm, different acetylation profiles in regard to functional proteins involved in sperm capacitation, sperm-egg recognition, sperm-egg plasma fusion, and fertilization were observed, indicating that acetylation of functional proteins may be required during sperm capacitation. Bioinformatics analysis revealed association of acetylated proteins with diseases and drugs. Novel acetylation of voltage-dependent anion channel proteins was also found. With clinical sperm samples, we observed differed lysine acetyltransferases and lysine deacetylases expression between normal sperm and abnormal sperm of asthenospermia or necrospermia. Furthermore, with sperm samples impaired by epigallocatechin gallate to mimic asthenospermia, we observed that inhibition of sperm motility was partly through the blockade of voltage-dependent anion channel 2 Lys-74 acetylation combined with reduced ATP levels and mitochondrial membrane potential. Taken together, we obtained a qualified pananti-acetyllysine monoclonal antibody, analyzed the acetylproteome of uncapacitated human sperm, and revealed associations between functional protein acetylation and sperm functions. Molecular & Cellular

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“…Moreover, as portrayed from the study, diabetic animal had depleted spermatogenic epithelial cells and cytoplasmic vacuolations with detachment of spermatogenic cells from the basement membrane. These abnormalities were related to the necrospermia and astenospermia [44,45]. This finding is line with recent study which reported that the necrosis of spermatogenic epithelium cells was connected to the low sperm count, reduced sperm motility and depleted daily sperm production [46].…”

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“…Lysine acetylation is essential for sperm motility and fertilization as shown by the interference in such processes by histone acetylase inhibitors and anti-acetyllysine antibodies [106]. Lysine acetylproteome was compared between uncapacitated and capacitated sperm [107,108]; different acetylation profiles were observed for functional proteins involved in sperm capacitation, sperm-egg recognition, sperm-egg plasma fusion, and fertilization. Phosphorylation, as resulting from the balance between the catalytic action of kinases [109] and phosphatases [110], is also of key importance in the mechanisms of sperm maturation and capacitation.…”

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