The Involvement of Neprilysin and Insulysin in Amyloid Beta Peptide Catabolism

This proposal Is based on trle premise that tIlerels Ii balance between A beta peptide synthesis and c~tabolism. An imbalance in either of these processes can be a risk factor in AD. Two peptidases, neprllysio (N=P) and insulindegri1ding enzyme (IDE), !lave each been suggested to be the major enzyme involved in A beta peptide catabolism. We will initially focus on determining the contribution of NEP and IDE to A beta peptide catabolism In model cell lines. 7PA2-CHO cells and H4 neuroblastoma Cf3l1s which express and secrete A beta peptides will be transfected with membrane and secreted forrns of NEP and lor membrane, secreted, and Intraceltularforms of IDE. The ability of each of the NEP and IDE forms to metabolize secreted and intracellular A beta peptldes will be compared. The second objective of this study will be to develop specl1lc inhibitors of IDc. A variety of peptide derivatives will be examined using a high--throughput fIuorogenic assay, and the most promising modified to produce a specifIc IDE; inhibitor. In the third objective a specific NEP Inhibitor (thiorphI:lO) aod the newly developed IDE inhibitors will be tested as inhibitors of A beta peptide catabol~sm in )1)rimary neuronal cultures. This analysis will be extended to a study of the effect of these Inhibitors on A beta peptide levels In an APP transgenic mouse model. Together these studies should provide new insights into the mechanism of A beta peptide catabolism and may lead to new approaches for treating AD.