Aberrant accumulation of protein aggregates is a common feature of age-related neurodegenerative diseases, including Alzheimer's disease. Cells clear aggregated material via autophagy. Lysosomes, the acidic organelles where proteins and unused cellular components are degraded and recycled, are the terminal compartment of autophagy. Long-lived, post-mitotic cells such as neurons are dependent upon continuous lysosomal turnover of cellular materials delivered by autophagy. With aging, lysosomes become less acidic, and their proteolytic activity decreases. In a cellular model of Alzheimer's disease, re-acidification of lysosomal pH increases autophagic flux and rescues cell function. We discovered a signaling cascade which regulates lysosomal acidification. Soluble adenylyl cyclase (sAC) is a source of the ubiquitous second messenger cAMP which is molecularly, structurally, biochemically, and functionally distinct from the family of plasma membrane-bound, hormone-regulated transmembrane forms of adenylyl cyclase. We showed sAC-generated cAMP promotes lysosomal acidification, and in the absence of sAC activity, autophagic flux is slowed. There are no pharmacological activators of sAC. We previously used high throughput screening to identify the most widely used pharmacological inhibitors specific sAC. We now propose to use high throughput screening and our battery of in vitro and cellular sAC assays to identify and characterize ?first-of-their kind? small molecule activators selective for sAC usable in cellular systems. We hypothesize that sAC activators will facilitate lysosomal acidification and increase degradation of accumulated protein aggregates in cellular models of neurodegenerative disorders. These studies have the potential to supply proof- of-principle for a therapeutic strategy to treat neurodegenerative disorders.
Age-related neurodegenerative diseases, including Alzheimer's Disease, are a global epidemic which result from accumulation of misfolded protein aggregates. The lysosomal system, as the final phase of autophagy, is responsible for clearing the cell of unused protein aggregates and old or obsolete cellular machinery. Facilitating lysosomal acidification will increase the efficiency of autophagic clearance which we hypothesize will `clean up' aggregates in aged and diseased neurons, and we propose to develop the research tools necessary to test this hypothesis.
