Regulation of Phosphorylation of Glycogen Synthase Kinase 3 & alpha; and the Correlation with Sperm Motility in Human

Abstract

Purpose: To unravel the mechanism regulating the phosphorylation of glycogen synthase kinase 3 (GSK3) and the correlation between the inhibitory phosphorylation of GSK3 & alpha; and sperm motility in human.Materials and Methods: The phosphorylation and priming phosphorylated substrate-specific kinase activity of GSK3 were ex-amined in human spermatozoa with various motility conditions.Results: In human spermatozoa, GSK3 & alpha;/& beta; was localized in the head, midpiece, and principal piece of tail and p-GSK3 & alpha;(Ser21) was enriched in the midpiece. The ratio of p-GSK3 & alpha;(Ser21)/GSK3 & alpha; was positively coupled with normal sperm motility criteria of World Health Organization. In high-motility spermatozoa, p-GSK3 & alpha;(Ser21) phosphotyrosine (p-Tyr) proteins but p-GSK3 & alpha;(Tyr279) markedly increased together with decreased kinase activity of GSK3 after incubation in Ca2+ containing medium. In high-motility spermatozoa, p-GSK3 & alpha;(Ser21) levels were negatively coupled with kinase activity of GSK3, and which was deregulated in low-motility spermatozoa. In high-motility spermatozoa, 6-bromo-indirubin-3'-oxime, an inhibitor of kinase activity of GSK3 increased p-GSK3 & alpha;(Ser21) and p-Tyr proteins. p-GSK3 & alpha;(Ser21) and p-Tyr protein levels were decreased by inhibition of PKA and Akt. Calyculin A, a protein phosphatase-1/2A inhibitor, markedly increased the p-GSK3 & alpha;(Ser21) and p-Tyr proteins, and significantly increased the motility of low-motility human spermatozoa.Conclusions: Down regulation of kinase activity of GSK3 & alpha; by inhibitory phosphorylation was positively coupled with human sperm motility, and which was regulated by Ca2+, PKA, Akt, and PP1. Small-molecule inhibitors of GSK3 and PP1 can be considered to potentiate human sperm motility.