The sperm protein fertilin β (or ADAM 2) is crucial for binding between sperm and egg. Its counterpart on the egg is the α6β1 integrin, a surprising finding given that α6β1 is known as a laminin receptor, and integrins are primarily known for their binding to the extracellular matrix. Now Chen et al. (page ) find that distinct states of α6β1 can bind to either fertilin β or laminin. “This may be a paradigm for switching between cell–cell and cell–matrix interactions,” says senior author Judith White.
After treatment with phorbol esters or manganese ions, macrophages transfected with α6 bind more to laminin and less to sperm. Eggs treated the same way bind less to sperm or fertilin β–coated beads, but only the manganese treatment increases laminin binding. This may reflect a difference in the complement of integrin-associated proteins in macrophages and eggs.
Binding of fertilin β to eggs is...
