Several focal adhesion proteins are known to co-operate with integrins to link the extracellular matrix to the actin cytoskeleton. As a result, many intracellular signaling pathways are activated and several focal adhesion complexes are formed. However, how these proteins function in mammalian spermatozoa remains unknown. We confirm the presence of focal adhesion proteins in guinea pig spermatozoa, and we explore their role during capacitation and the acrosome reaction, and their relationship with the actin cytoskeleton. Our results suggest the presence of a focal adhesion complex formed by β1-integrin, FAK, paxillin, vinculin, talin, and α-actinin in the acrosomal region. Inhibition of FAK during capacitation affected the protein tyrosine phosphorylation associated with capacitation that occurs within the first few minutes of capacitation, caused the acrosome reaction to become increasingly Ca2+ dependent, and inhibited the polymerization of actin. The integration of vinculin and talin into the complex and the activation of FAK and paxillin during capacitation suggests that the complex assembles at this time. We identify that vinculin and α-actinin increase their interaction with F-actin while it remodels during capacitation and that during capacitation, focal adhesion complexes are structured. FAK contributes to acrosome integrity, likely by regulating the polymerization and the remodeling of the actin cytoskeleton.
- Received February 12, 2016.
- Accepted July 4, 2016.
- © 2016. Published by The Company of Biologists Ltd
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