Metalloprotease-disintegrins (ADAMs) are a family of membrane anchored glycoproteins that have key roles in fertilization, neurogenesis, and in activation of EGF receptor ligands during development. The main goal of this proposal is to uncover the mechanism underlying the perinatal lethal phenotype of mice lacking the widely expressed ADAM 19, with an emphasis on evaluating the predicted role of ADAM19 in protein ectodomain shedding. Protein ectodomain shedding leads to the release of a variety of structurally and functionally diverse proteins from the plasma membrane, and has recently emerged as a critical post-translational mechanism of regulating the function of the released proteins. Ectodomain shedding is essential for proper signaling via EGF receptor-ligands, Notch-mediated lateral inhibition, limiting TNF receptor mediated inflammatory reactions, and regulating several aspects of axonal guidance. Because the first identified sheddase, the TNFalpha convertase, is an ADAM, and because lIMP inhibition studies rule out currently known matrix metalloproteases (MMPs) as sheddases for most proteins, ADAMs have emerged as the best candidate ectodomain sheddases. Our working hypothesis is that the phenotype of mice lacking ADAM19 is due, at least in part, to a defect in ectodomain shedding of one or more proteins.
The specific aims of this project are: 1) Perform a careful histopathological analysis of mice lacking ADAM19 in order to uncover the cause of the observed perinatal lethality. This will include an identification of the cell types in the lung, heart, and in bone marrow derived cells where ADAM19 is highly expressed, and in vivo studies to evaluate the function of ADAM19 in these cells and tissues. 2) Address the possibility of functional redundancy and compensation between ADAM 19 and other ADAMs during development by generating mice lacking other related ADAMs in addition to ADAM19. 3) Uncover potential aelects in ectodomain shedding in cells lacking ADAM 19 or other ADAMs compared to wildtype cells using a biased and unbiased approach The biased approach will focus on proteins that are known to be shed and could contribute to the phenotype of mice lacking ADAM 19, such as EGFR-ligands, TNF- and TNF-receptor family members. The unbiased approach will compare proteins secreted into the supernatant of wildtype and ADAM 19 knockout cells. This study will provide exciting insights into the function of ADAM19 during development and in adult mice, and will uncover the mechanism by which a defect in ADAM 19 leads to perinatal lethality. Our results are likely to have implications for the function of ADAM19 in human disease, and may uncover novel targets for therapeutic interventions in diseases that are caused by a misregulated or defective ADAMI9 or by other related ADAMs.
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