MAB19292 Sigma-AldrichAnti-ADAM2 Antibody, clone 9D2.2

In order to understand the mechanisms of mammalian fertilization, studies using genetically manipulated animals have provided us with plenty of interesting and valuable information on the genetic factors affecting male fertility. In the present work, we demonstrate for the first time that Prss37, a previously uncharacterized putative trypsin-like serine protease, is required for male fertility. Prss37 is highly and exclusively expressed in the testis of adult mice, especially in the elongating spermatids during spermiogenesis, and almost vanishes in the mature sperm of mice. Mice deficient for Prss37 show male infertility, but their mating activity, spermatogenesis, sperm morphology, and motility remain unaffected. In vivo fertilization assays revealed that Prss37(-/-) mice exhibited a markedly decreased fertilization rate (2.3% vs. 70% of that in control mice) accompanied by the defect in sperm migration from uterus into oviduct. In vitro study further showed sperm were incapable of sperm-egg recognition/binding when zona-intact eggs were exposed to Prss37(-/-) sperm, in which mature Adam3 was completely undetectable. Interestingly, however, Prss37(-/-) sperm were able to fertilize cumulus-intact oocytes in vitro. These data clearly indicate that Prss37 deficiency causes the absence of mature Adam3 in sperm and a defect in sperm migration from uterus into oviduct, which mainly accounts for male infertility of Prss37-null mice, while the defect in sperm-zona binding seems irrelevant to the fertilizing ability of Prss37(-/-) sperm.

In mammals, sperm acquire their motility and ability to fertilize eggs in the epididymis. This maturation process involves the acquisition of particular proteins from the epididymis. One such secretory protein specifically expressed in the epididymis is Adam7 (a disintegrin and metalloprotease 7). Previous studies have shown that Adam7 that resides in an intracellular compartment of epididymal cells is transferred to sperm membranes, where its levels are dependent on the expression of Adam2 and Adam3, which have critical roles in fertilization. Here, using a proteomics approach based on mass spectrometry, we identified proteins that interact with Adam7 in sperm membranes. This analysis revealed that Adam7 forms complexes with calnexin (Canx), heat shock protein 5 (Hspa5), and integral membrane protein 2B (Itm2b). Canx and Hspa5 are molecular chaperones, and Itm2b is a type II integral membrane protein implicated in neurodegeneration. The interaction of Adam7 with these proteins was confirmed by immunoprecipitation-Western blot analysis. We found that Adam7 and Itm2b are located in detergent-resistant regions known to be highly correlated with membrane lipid rafts. We further found that the association of Adam7 with Itm2b is remarkably promoted during sperm capacitation owing to a conformational change of Adam7 that occurs in concert with the capacitation process. Thus, our results suggest that Adam7 functions in fertilization through the formation of a chaperone complex and enhanced association with Itm2b during capacitation in sperm.