Testis-Specific Isoform of Na/K-ATPase (ATP1A4) Interactome in Raft and Non-Raft Membrane Fractions from Capacitated Bovine Sperm

Abstract

The plasma membrane of sperm contains highly dynamic lipid microdomains (rafts), which house signaling proteins with a role in regulating capacitation. We reported that ATP1A4, the testis-specific isoform of Na/K-ATPase, interacted with caveolin-1, Src, epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinases 1/2 (ERK1/2) in raft and non-raft domains of the plasma membrane of bovine sperm during capacitation. The objective of the present study was to use a proteomic approach to characterize the ATP1A4 interactome in rafts and non-rafts from capacitated bovine sperm. The non-raft interactome included hexokinase 1, plakophilin 1, desmoglein 1, 14-3-3 protein ζ/δ, cathepsin D and heat shock protein beta1 proteins exclusively, whereas glutathione S-transferase and annexin A2 were unique to raft interactome. However, a disintegrin and metalloprotease 32 (ADAM 32), histone H4, actin, acrosin, serum albumin and plakoglobin were identified in both raft and non-raft fractions of capacitated sperm. Based on gene ontology studies, these differentially interacted proteins were implicated in cell–cell adhesion, signal transduction, fertilization, metabolism, proteolysis and DNA replication, in addition to acting as transport/carrier and cytoskeletal proteins. Overall, we identified proteins not previously reported to interact with ATP1A4; furthermore, we inferred that ATP1A4 may have a role in sperm capacitation.