Na+/K+ATPase as a Signaling Molecule During Bovine Sperm Capacitation1

Abstract

A heteromeric integral membrane protein, Na+/K+ATPase is composed of two polypeptides, alpha and beta, and is active in many cell types, including testis and spermatozoa. It is a well-known ion transporter, but binding of ouabain, a specific inhibitor of Na+/K+ATPase, to Na+/K+ATPase in somatic cells initiates responses that are similar to signaling events associated with bovine sperm capacitation. The objectives of the present study were to demonstrate the presence of Na+/K+ATPase in bovine sperm and to investigate its role in the regulation of bovine sperm capacitation. The presence of Na+/K+ATPase in sperm from mature Holstein bulls was demonstrated by immunoblotting and immunocytochemistry using a monoclonal antibody developed in mouse against the beta 1 polypeptide of Na+/K+ATPase. Binding of ouabain to Na+/K+ATPase inhibited motility (decreased progressive motility, average path velocity, and curvilinear velocity) and induced tyrosine phosphorylation and capacitation but did not increase intracellular calcium levels in spermatozoa. Furthermore, binding of ouabain to Na+/K+ATPase induced depolarization of sperm plasma membrane. Therefore, binding of ouabain to Na+/K+ATPase induced sperm capacitation through depolarization of sperm plasma membrane and signaling via the tyrosine phosphorylation pathway without an appreciable increase in intracellular calcium. To our knowledge, this is the first report concerning the signaling role of Na+/K+ATPase in mammalian sperm capacitation.

Activity of the Na,K-ATPase α4 isoform is important for membrane potential, intracellular Ca2+, and pH to maintain motility in rat spermatozoa

“…Specifically, ouabain has been reported to elicit a series of responses in bull spermatozoa. In this species, ouabain does not modify total motility or amplitude of lateral head displacement, but it decreases progressive motility, and curvilinear and average path velocities (Thundathil et al 2006). On the other hand, McGrady (1979) found ouabain to cause a general decrease in bull sperm flagellar wave.…”

“…Besides its effects on sperm motility, ouabain has also been shown to produce capacitation in bull sperm through mechanisms that are independent of increases in intracellular Ca 2C (Thundathil et al 2006), but that involve activation of kinases and protein phosphorylation events in the cells (Newton et al 2009). Our experiments were designed to investigate the rapid effects of ouabain and did not include long-term consequences on sperm capacitation.…”

Protein biomarkers for male artificial insemination subfertility in bovine spermatozoa

“…A model has been proposed for the induction of bull sperm capacitation by the interaction between Na + /K + ‐ATPase and its inhibitor, “ouabain.”100, 101 It is likely that the inhibition of the Na + /K + ‐ATPase activity with ouabain promotes an increase of the intracellular Ca 2+ (by the suppression of the Na + /Ca 2+ exchanger activity), PKA activation, and tyrosine phosphorylation, leading to capacitation. Moreover, the interaction between Na + /K + ‐ATPase and ouabain might activate the extracellular signal‐regulated kinases 1/2, phospholipase C, protein kinase C and protein tyrosine kinase signaling cascades, leading to capacitation.…”

“…Moreover, the interaction between Na + /K + ‐ATPase and ouabain might activate the extracellular signal‐regulated kinases 1/2, phospholipase C, protein kinase C and protein tyrosine kinase signaling cascades, leading to capacitation. This ion transporter, Na + /K + ‐ATPase,100, 102 is generated in the testes and subsequently is localized in the head (postacrosomal region) and middle piece of the ejaculated spermatozoa. In the experiment in which the testicular temperature was elevated in bulls (Holstein) by scrotal insulation,101 its generation was awfully disturbed in the testes and its content was largely decreased in the spermatozoa.…”

Effect of hydrogen peroxide on the main kinetic parameters of ATP hydrolysis by ouabain sensitive Na+, K+-ATP-ase in spermatozoa of infertile men

“…Ензим регулює рухливість клітин, проліферацію клітин, синтез глікогену, внутрішньоклітинний кальцієвий рівень, гомеостаз йонів натрію, сигналізацію кальцію, апоптоз тощо [3][4][5]. Сигнальні функції ензиму були продемонстровані в різних типах клітин, зокрема в сперматозоїдах [1].…”