β1 and β3 integrins disassemble from basal focal adhesions and β3 integrin is later localised to the apical plasma membrane of rat uterine luminal epithelial cells at the time of implantation

The present study investigated the expression of integrin subunits that are known to be associated with focal adhesions, namely β1 and β3 integrins in rat uterine luminal epithelial cells during early pregnancy. The β1 and β3 integrins were concentrated along the basal cell surface and were colocalised and structurally interacted with talin, a principal focal adhesion protein, on Day 1 of pregnancy. At the time of implantation, β1 and β3 integrins disassembled from the site of focal adhesions, facilitating the removal of uterine luminal epithelial cells for embryo invasion. Also at this time, β3 integrin markedly increased along the apical membrane, suggesting a role in embryo attachment. This distributional change in β1 and β3 integrins seen at the time of implantation was predominantly under the influence of progesterone. Taken together, β1 and β3 integrin disassembly from focal adhesions and the increase in β3 integrin apically are key components of hormonally regulated endometrial receptivity.