Potential role of αv and β1 integrins as oocyte adhesion molecules during fertilization in pigs

Integrin molecules are cell adhesion molecules that are thought to be involved in sperm-oocyte interaction in rodents and humans. The objective of this study was to evaluate whether integrin molecules were present on the surface of pig oocytes, consistent with involvement in sperm-oocyte interaction in this species. Immunocytochemistry and confocal microscopy were used to evaluate the presence of beta 1, and alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, alpha 6 and av integrin subunits on the plasma membrane of pig oocytes. The beta 1 and alpha v integrin subunits were present consistently at the surface of pig oocytes; however, the remaining alpha integrin subunits evaluated were not routinely detected. The antibodies to the beta 1 and alpha v integrin subunits recognized appropriately sized protein bands on western blots of partially purified oocyte plasma membrane. These two antibodies also recognized oocyte plasma membrane protein isolated from a sperm plasma membrane affinity column. Sperm plasma membrane proteins of 137 and 93 kDa appeared to be the ligands for the beta 1 integrin subunit as revealed by a western sandwich blot. Antibody to an extracellular domain of the beta 1 integrin subunit reduced pig sperm-oocyte binding (P < 0.05), also indicating an assisting role for a beta 1 oocyte integrin subunit in sperm-oocyte interaction in pigs. These results are consistent with an alpha v beta 1 pig oocyte integrin interacting with a ligand on the sperm plasma membrane during fertilization.