Role of integrins during fertilization in mammals.
Fertilization includes sperm-oocyte recognition, adhesion, binding, fusion and egg activation. Integrin receptors, which are adhesion molecules, are expressed on sea urchin, mouse, hamster and human unfertilized oocytes. Potential sperm ligands have been identified. A role for integrins during fertilization is supported by inhibition of sperm-egg adhesion and/or fusion by means of anti-integrin monoclonal antibodies, Arg-Gly-Asp (RGD) or disintegrin-like peptides. In several cell-cell interactions, such as lymphocyte activation, viral fusion, bacterial infection or macrophage phagocytosis, integrins act as co-receptors after activation and, by clustering in a multimolecular complex, are able to transduce signals through cytoskeletal proteins and adaptor kinases. Experimental data suggest that they may act in a similar way during fertilization and may participate to initiation and/or propagation of the calcium signal via stimulation of phospholipase C gamma and inositol trisphosphate production.