The goal of this research is to understand how mitochondrial transport, distribution and metabolism are regulated in neurons. Most neurodegenerative diseases involve mitochondrial dysfunction, and many result directly from specific failures of mitochondrial traffic, distribution or metabolism. This is probably because the size and asymmetry of neurons result in a non- uniform distribution of demand for mitochondrial functions such as ATP synthesis. As a result, neurons must extensively redistribute their mitochondria in response to local physiological conditions, both in vivo and in vitro. Mitochondria are transported and redistributed within the axon by several motor proteins that translocate along microtubule and actin tracks, as well as by docking interactions. But how movement, docking and mitochondrial metabolism are regulated and coordinated to deliver the right amount of function to the right location at the right time remains unclear. Our efforts to understand these events are focused on both the specific proteins involved in transport and docking, and on larger-scale processes in the healthy and diseased nervous system. In the first two aims, we will test the hypotheses that mitochondrial distribution is regulated by myosin-based disruptions of protracted movements and by inhibition of MT-based motor activities, and is controlled by signaling kinases. We will use double- stranded RNA inhibition to knock down expression of myosins V, VI and II and kinesin- regulating kinases in isolated Drosophila neurons and quantify the resulting transport phenotypes. We will also use observation of mitochondrial traffic in segmental nerve axons of intact larvae to assess the transport phenotype of myosin mutations. In the third aim, we will use Drosophila models of human mitochondrial diseases to critically assess the hypothesis that the proximal cause of neuropathology in mitochondrial neurodegenerative disease is oxidative damage rather than defects in mitochondrial transport or metabolism. Using quantitative fluorescence microscopy methods, we will determine the relationships among mitochondrial traffic, metabolism and reactive oxygen species production throughout the nervous system and across development in models for Friedriech ataxia, Barth syndrome and other disorders.
Nearly all neurodegenerative diseases are now thought to involve some kind of mitochondrial dysfunction, and many to result directly from specific failures of mitochondrial traffic, distribution, or metabolism. The proposed research seeks to understand the regulation of mitochondrial movements in neurons, and the relationship between those movements and other aspects of mitochondrial function, particularly in animal models of human mitochondrial disease. Our hope is that this knowledge will aid in designing new treatments for these disorders.
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