The worldwide population of individuals over the age of 65 is continuing to grow and is expected to double over the next 30 years. Due to this increase, an associated rise in age-related neurodegenerative diseases (NDs), such as Alzheimer?s (AD) and Parkinson?s disease, has been observed. Despite decades of research, there are currently no FDA-approved therapies that can stop or reverse disease progression. The accumulation of misfolded protein aggregates is a common feature of age-related NDs and is thought to be heavily involved in the pathophysiology of the diseases. Proteins aggregates can be cleared from the cell through autophagy, one of the major biological degradation pathways. Protein aggregates are degraded in the final step of autophagy, where they are delivered to cellular organelles known as lysosomes. Lysosomes maintain an acidic pH between 4-5 to maintain an optimal environment for acid hydrolases. In aging cells and in a cellular model of AD, lysosomes become less acidic, their hydrolases become less active and, as a result, there is a decrease in degradation through autophagy (i.e., autophagic flux) and an accumulation of undigested materials. In models of AD pathology, re-acidification of lysosomal pH, via addition of exogenous cAMP, reversed this phenotype. In line with these findings, we have shown that cAMP generated from a cytosolic adenylyl cyclase isoform, known as Soluble Adenylyl Cyclase (sAC), promotes lysosomal acidification. In addition, cells that do not express sAC show decreased autophagic flux. This, and other, physiological roles of sAC have been determined via the use of inhibitors and various genetic tools that were developed to study sAC biology. However, the ?toolbox? that is currently used to study sAC is lacking a key component: a pharmacological activator of sAC. To identify a sAC activator, we conducted a high-throughput screen of 400,000 chemically diverse compounds. From this library we discovered 13 presumptive sAC activators. In this proposal, I describe the in vitro and cell-based assays that I will use to confirm, characterize, and further develop these 13 compounds as ?first-of-their kind? small molecule activators selective for sAC. Using the newly discovered sAC activators, I will test the hypothesis that stimulating sAC can enhance lysosomal acidification and stimulate autophagy, and as a result, decrease accumulation of protein aggregates. If successful, these studies will validate small molecule sAC activators as a potential novel therapeutic strategy to treat neurodegenerative disorders.
The rate of population aging is steadily rising across the world; this is a major public health concern due to the concurrent increase in age-related neurodegenerative diseases, such as Alzheimer?s Disease. Lysosomes, via autophagy, are the cellular organelles that are responsible for degrading and clearing misfolded protein aggregates, which have been shown to accumulate in Alzheimer?s Disease and are thought to significantly contribute to disease pathogenesis. We hypothesize that facilitating lysosomal acidification will increase autophagic flux and enhance the clearance and degradation of protein aggregates; thus, in this proposal I outline an experiment strategy to develop and characterize a novel pharmacological tool to test this hypothesis.
