Figure 1. A hypothetical model for ATP1A4-mediated raft and non-raft signaling pathways during bovine sperm capacitation. Interactions between Na/K-ATPase isoform and Cav1, can activate phospholipase C (PLC), thereby generating inositol 1,4,5-triphosphate (IP3) and diacyl glycerol (DAG), via hydrolysis of phosphatidylinositol 4,5- bisphosphate which in turn activates protein kinase C (PKC). IP3 binds to its cognate receptor (IP3R), leading to an increase in intracellular calcium, whereas PKC mediates conversion of globular actin (G-actin) to filamentous-actin (F-actin) through other mediator proteins. Within non-rafts, Na/K-ATPase-ouabain interaction involves Src and EGFR. Signals from non-raft interactions are relayed downstream, leading to activation of ERK1/2 and protein tyrosine kinase (PTK)-mediated tyrosine phosphorylation of proteins. Increase in F-actin, intracellular calcium, and protein tyrosine phosphorylation contribute to capacitation-associated changes in sperm.
