EXPRESSION OF A P-SELECTIN LIGAND IN ZONA-PELLUCIDA OF PORCINE OOCYTES AND P-SELECTIN ON ACROSOMAL MEMBRANE OF PORCINE SPERM CELLS - POTENTIAL IMPLICATIONS FOR THEIR INVOLVEMENT IN SPERM-EGG INTERACTIONS

The selectin family of cell adhesion molecules mediates initial leukoc yte adhesion to vascular endothelial cells at sites of inflammation. O -glycan structural similarities between oligosaccharides from human le ukocyte P-selectin glycoprotein ligand-l (PSGL-1) and from zona pelluc ida glycoproteins of porcine oocytes indicate the possible existence o f a P-selectin ligand in the zona pellucida. Here, using biochemical a s well as morphological approaches, we demonstrate that a P-selectin l igand is expressed in the porcine zona pellucida. In addition, a searc h for a specific receptor for this ligand leads to the identification of P-selectin on the acrosomal membrane of porcine sperm cells. In vit ro binding of porcine acrosome-reacted sperm cells to oocytes was foun d to be Ca2+ dependent and inhibitable with either P-selectin, P-selec tin receptor-globulin, or leukocyte adhesion blocking antibodies again st P-selectin and PSGL-1. Moreover, porcine sperm cells were found to be capable of binding to human promyeloid cell line HL-60. Taken toget her, our findings implicate a potential role for the oocyte P-selectin ligand and the sperm P-selectin in porcine sperm-egg interactions.