In vivo targeting of Abeta and tau amyloidogeneses, neuroinflammation, calcium-mediated neurotoxicity and their interplays

Abstract

membrane-bound proteases termed beta-secretase (BACE1) and g-secretase. The level of Abeta in the brain is critically associated with both pathological and behavioral/clinical phenotypes of AD. Thus, CNS penetrable small molecules that can reduce Abeta in an effective and safe manner remains one of the most promising approaches for the treatment of AD. While a number of direct small molecule inhibitors of betaor g-secretase have been developed, many of them have suffered side effects owing to their target-associated toxicity. Methods: In the present study, we conducted reverse chemical genetic screening to identify small molecule inhibitors of BACE1-mediated cleavage of APP with a goal to ultimately identify a putative protein target of the identified small molecule inhibitor. In order to identify inhibitor compounds that act via a novel mechanism, we developed a cell-based assay in intact neuronal cells, based on antibody-mediated specific capture of the BACE1-derived secreted APP ectodomain (sAPPbeta) fused to a secreted alkaline phosphatase (SEAP) reporter. Results: By screening small molecule libraries using this cell system, we identified small molecules that can inhibit BACE1-mediated cleavage of APP without directly interfering with BACE1 activity. One such compound was subjected to medicinal chemistry to improve the bioactivity and the resulting compound (termed C2) reduces Abeta levels in cultured primary neurons as well as a mouse model of AD. We are currently investigating a putative cellular target for this compound. Conclusions: Identification of a small molecule modifier of the Abeta generation pathway and uncovering its cellular target may serve as the foundation for development of new therapeutic agents that could selectively probe pathological, but not normal, function of the Abeta-producing enzymes, such as BACE1.