FAK regulates actin polymerization during capacitation via the ERK2/GEF- H1/RhoA signaling pathway

Abstract

Actin polymerization is a crucial process during capacitation. We have recently described the participation of FAK in actin polymerization in guinea pig spermatozoa. However, the mechanism by which FAK achieves these processes is unknown. Our data showed that ERK2 is activated during the first minutes of capacitation; its inhibition blocked actin polymerization and the acrosome reaction. Additionally, the present study found that FAK is involved in ERK2 activation since FAK was phosphorylated in Tyr925 and bound to Grb2 and that the inhibition of FAK results in a significant decrease in ERK2 activation. We also confirmed the presence of GEF-H1, which was able to associate with RhoA during capacitation. RhoA activation and its participation in actin polymerization were also analyzed. FAK or ERK1/2 inhibition impeded GEF-H1 phosphorylation, RhoA activation, and the association between GEF-H1 and RhoA. Finally, we observed the presence of fibronectin on the sperm surface, its role in sperm-sperm interaction, and the participation of β-integrin in the activation of ERK2. Our results show that the signaling pathway Fibronectin/Integrin/FAK/Grb2/MEK1/2/ERK2/GEF-H1/RhoA regulates the actin polymerization associated with spermatozoa capacitation.