Mouse egg integrin α6β1functions as a sperm receptor

SummaryBinding between sperm and egg plasma membranes is an essential step in fertilization. Whereas fertilin, a mammalian sperm surface protein, is involved in this crucial interaction, sperm receptors on the egg plasma membrane have not been identified. Because fertilin contains a predicted integrin ligand domain, we investigated the expression and function of integrin subunits in unfertilized mouse eggs. Polymerase chain reactions detected mRNAs for α5, α6, αv, β1, β3, and β5. Immunofluorescence revealed α6β1 and αvβ3 on the plasma membrane. GoH3, a function-blocking anti-α6 monoclonal antibody, abolished sperm binding, but a nonfunction-blocking anti-a6 monoclonal antibody, a function-blocking anti-αvβ3 polyclonal antibody, and an RGD peptide had no effect. Somatic cells bound sperm avidly, but only if they expressed α6β1. A peptide analog of the fertilin integrin ligand domain inhibited sperm binding to eggs and α6β1+ cells and diminished GoH3 staining of eggs. Our results indicate a novel role for the integrin α6β1 as a cell-cell adhesion receptor that mediates sperm-egg binding