Research Summary We are focused on understanding the role of the endosomal-lysosomal system in neurodegeneration, specifically the dysfunction of the neuronal endosomal-lysosomal system seen in Alzheimer''s disease (AD), and possible synergism between these AD changes and aging-related lysosomal changes and the development of neuropathology. My background is in cell biology and membrane protein trafficking, so my interests inevitably gravitate towards understanding how alterations in vesicular trafficking and/or the trafficking of specific membrane proteins and their ligands through the endosomal-lysosomal system impacts the disease''s progression. Currently, we are using in vitro cell models as well as amyloid depositing transgenic mice to examine the following aspects of the neuronal endosomal-lysosomal system: The neuronal endosomal system appears to be upregulated very early in sporadic AD. We are modeling this by overexpressing important trafficking and regulatory proteins of the endosomal system, such as the mannose 6-phosphate receptors and various rab GTPases. In these models, we can examine changes in APP metabolism, ask whether Abeta generation or clearance is affected, and determine the impact of endosomal upregulation on other proteins that may play a prominent role in neuronal degeneration. The endosome plays a critical role in the metabolism of APP. We are examining the interplay between APP trafficking and its delivery to and dwell-time in various cellular compartments with specific cleavage events, such as those mediated by the beta- or alpha-secretases. Furthering our understanding of cellular events that regulate the trafficking of APP, either along pathways that promote Abeta generation or along non-amyloidogenic pathways, is likely to be critical to our understanding of the function(s) of APP and its metabolites as well as developing anti-Abeta treatments. We are also investigating the relationship between endosomal proteolysis of APP and presenilin function, including specific cleavage at residues 40 or 42 of Abeta. In vivo, we are manipulating the lysosomal system in transgenic mice brains by infusing drugs that regulate specific proteolytic systems. Our goal here is to mimic in a mouse the aging-related lysosomal changes seen in human neurons, thereby more completely reproducing the multiple stresses (Abeta, lysosomal, cytoskeletal) faced by a human neuron during the progression of Alzheimer''s disease. Finally, in support of these projects, we have made a substantial effort to develop tools, primarily monoclonal antibodies and related assays such as ELISAs, that allow us to detect with high specificity and great sensitivity many of the key metabolites of APP.