Control of Neural Organelle Transport

Purdue University, West Lafayette IN

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Abstract

ABSTRACT The goalofthis research is to understand how mitochondrialtransport,distribution,and metabolism areregulatedinneurons. Mostneurodegenerativediseasesinvolvemitochondrialdysfunction,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 theirmitochondria in responseto localphysiologicalconditions,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, along with anchorage of motor proteins to the organelle by specific linker proteins. We will use double-stranded RNA inhibition to knock down expression of myosins V, VI and II, and three putative motor-organelle linker proteins 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 and linker protein mutations. In the third aim, we will use Drosophila models of human mitochondrial diseases to test 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 Friedreich ataxia, Barth syndrome and other disorders.