Authors: Luiz Miguel Camargo, Patrick Loearch, Mike Caceres, Xiaohua Douglas Zhang2, Richard Raubertas, Paolo Uva, David Stone, John Majercak, William J. Ray, Marc Ferrer, Shane D. Marine, Emanuele de Rinaldis, Carol A Rohl, Jason M., Johnson, Tom L. Blundell, Mark, S, Shearman, and Kenji Mizuguchi
Abstract: A prevailing model of Alzheimer's Disease etiology is the progressive aggregation of toxic Ab peptides in the brain. Ab is produced as a result of proteolytic processing of the amyloid precursor protein (APP). Cleavage of APP by b- and g -secretases result in the production of Ab and hence several drug discovery efforts are aimed at finding either b- or g- secretase inhibitors. However, development of small molecules to either of these enzymes has proven to be challenging. In order to overcome limitations of developing b or g-secretase inhibitors, we performed large scale siRNA screens in order to identify novel regulators of APP processing that could represent more tractable drug targets. The screen measures the production of four APP proteolytic products: the non-amyloidgenic peptide (sAPPa) or the amyloidgenic pathway peptides (Ab40, Ab42, and sAPPb). We introduce a novel analysis method that scores the overall effect of individual pathways on the processing of the APP protein. This method takes into account all genes in the pathway, thus allowing for small effects to be considered, and introduces the concept of scoring 'pathways' as opposed to individual genes as a way of mitigating against false positive hits. Using this method, we identified novel and distinct pathways that regulate processing of APP into either amyloidgenic peptides or non-amyloidgeneic peptides respectively. We will also highlight how to leverage biological network data in combination with siRNA screens to to better delineate and/or identify novel pathways.
Research fully funded by Merck & Co.