ICAM-2 and lipid rafts disappear from the basal plasma membrane of uterine epithelial cells during early pregnancy in rats

Abstract

Adhesion molecules are redistributed in rat uterine epithelial cells (UECs) during early pregnancy for endometrial receptivity and implantation. Intercellular adhesion molecule-2 (ICAM-2) is located as an oligomer on the basal plasma membrane of non-receptive UECs on day 1 of pregnancy and colocalizes with the lipid raft marker flotillin-2. At the time of implantation in rats and in ovariectomized rats primed with progesterone, ICAM-2 disappears from the basal plasma membrane and lipid rafts redistribute to the apical membrane. The loss of ICAM-2 might render UECs less adherent to the underlying basal lamina and more prone to apoptosis. Flotillin-2 in the apical plasma membrane at the time of implantation might provide an anchoring point for several adhesion molecules that are known to localize to this region at this time. We suggest that flotillin-2 is involved with adhesion between UECs and the implanting blastocyst, whereas ICAM-2 is associated with the ability for UECs to be removed at the time of implantation.