The Sodium Pump Regulates Sperm and Sertoli Cell Function
Abstract
Abnormalities in sperm function at the submicroscopic level (not detectable during routine semen evaluation) influence bull fertility and therefore the efficiency of cattle production. New knowledge regarding the molecular basis of spermatogenesis and sperm function will enable us to develop evidence-based approaches for improving fertility. The overall aim of this thesis was to investigate role of Na/K-ATPase (the sodium pump) isoforms in sperm function, Sertoli cell function and male fertility. In fresh bovine sperm, I identified two distinct pools (raft and non-raft) of the testis-specific isoform of Na/K-ATPase (ATP1A4) in the plasma membrane. The raft pool of ATP1A4 interacted with caveolin-1 and EGFR, whereas the non-raft pool of ATP1A4 interacted with EGFR, Src and ERK1/2 in capacitated sperm. In addition, a comprehensive analysis revealed that the ATP1A4 interactome differed between raft and non-raft fractions of capacitated sperm. Specifically, ATP1A4 interacted and co-localised with plakoglobin (member of β-catenin family of proteins involved in cell adhesion) in the equatorial segment of capacitated sperm; this suggests a potential role for these proteins in sperm-oolemma fusion. During investigation of ATP1A4 involvement in lipid rafts, I determined that ATP1A4 content and activity were increased during capacitation, perhaps due to translation of ATP1A4 mRNA in mitochondrial or mitochondrial-type ribosomes. In frozen-thawed sperm, content and activity of ATP1A4 was greater in high- versus low-fertility bulls and significantly correlated with fertility. Additionally, ATP1A4-induced ROS, calcium, actin polymerization and tyrosine phosphorylation were also involved in regulating post-thaw sperm function in these bulls. My results also demonstrated that prepubertal rat Sertoli cells expressed ATP1A1 (the ubiquitous isoform of Na/K-ATPase) and that ATP1A1-ouabain interaction regulated formation (modulation of claudin 11 and connexin 43 expression) and function (transepithelial electric resistance) of Sertoli cell junctional complexes through Src-EGFR-ERK1/2- CREB pathway in a dose-dependent manner. Overall, results demonstrated that isoforms of Na/K-ATPase have unique roles in controlling several aspects of sperm and Sertoli cell physiology, acting through its well-established enzyme activity and signaling functions. Consequently, isoforms of Na/K-ATPase are potential candidates for reversible male contraception and a biomarker for male fertility.
Description
Keywords
Animal Physiology, Biology--Cell, Veterinary Science
Citation
Rajamanickam, G. D. (2016). The Sodium Pump Regulates Sperm and Sertoli Cell Function (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/28384