Analysis of fertilin alpha (ADAM1)-mediated sperm-egg cell adhesion during fertilization and identification of an adhesion-mediating sequence in the disintegrin-like domain.

Fertilin alpha (also known as ADAM1) is a member of the ADAM (A disintegrin and A metalloprotease domain) family of proteins. In this study, we examine the mechanism of mouse fertilin alpha's in adhesion of sperm to the egg plasma membrane during fertilization. We find that recombinant forms of fertilin alpha corresponding to either the disintegrin-like domain or the cysteine-rich domain and the EGF-like repeat can perturb sperm-egg binding, suggesting that both of these domains can participate in fertilin alpha-mediated adhesion events. In further examination of the fertilin alpha disintegrin-like domain, we find that a subdomain of disintegrin-like domain with the sequence DLEECDCG outside the putative disintegrin loop but with homology to the fertilin beta disintegrin loop can inhibit the binding of both sperm and recombinant fertilin alpha to eggs, suggesting that this is an adhesion-mediating motif of the fertilin alpha disintegrin-like domain. This sequence also inhibits the binding of recombinant fertilin beta to eggs and thus is the first peptide sequence found to block two different sperm ligands. Finally, a monoclonal antibody to the tetraspanin protein CD9, KMC.8, inhibited the binding of recombinant fertilin alpha to eggs in one type of binding assay, suggesting that, under certain conditions, fertilin alpha may interact with a KMC.8-sensitive binding site on the egg plasma membrane.

Silicone gel and octamethylcyclotetrasiloxane potentiate antibody production to bovine serum albumin in mice.

Earlier studies, in the rat, have shown that silicone gel acts as a potent adjuvant for antibody production against bovine serum albumin (BSA). The purpose of the present study is to determine whether components of the silicone breast implant (silicone oil, silicone gel, and octamethylcyclotetrasiloxane [D4]) potentiate the antibody response to BSA in mice. Groups of ten A/J mice received a single subcutaneous injection of 0.1 ml of BSA emulsified with the following: a) silicone preparations, b) incomplete Freund's adjuvant, or c) saline alone. Antibodies to BSA were measured using an enzyme-linked immunosorbant assay. The results indicate that both D4 and the silicone gel potentiate antibody production to BSA in mice. Known adjuvants have been shown to induce autoimmune syndromes in animal models. Whether silicones can act in a similar mechanism is still unclear.