Amyotrophic lateral sclerosis (ALS) is a fatal and incurable disease characterized by the degeneration and death of motor neurons. Both sporadic and inherited forms of ALS follow a common pathogenic pathway, which is still not understood. One hypothesis that may explain the motor neuron-specific cell death observed in ALS and other similar neurodegenerative diseases is that motor neurons are uniquely sensitive to defects in axonal transport. Active transport along the axon is driven by microtubule motor proteins;while multiple kinesins drive anterograde transport, cytoplasmic dynein and its activator dynactin are the only motor driving retrograde transport. Dominant mutations in either dynein or dynactin are sufficient to cause motor neuron disease, demonstrating the importance of axonal transport in maintaining healthy motor neurons. We now have data directly demonstrating significant defects in retrograde transport in multiple models of motor neuron disease, including a well- characterized mouse model of familial ALS;defects in dynein localization and function occur as an early event in disease pathogenesis in these models. We will examine the mechanisms linking defects in axonal transport to neurodegeneration, focusing on alterations in both the efficiency of retrograde transport and the nature of the cargos being transported. We hypothesize that these changes act together to lead to alterations in the balance of survival and death signals in the neuron, resulting in neuronal degeneration and cell death. To test this hypothesis, we will pursue three specific aims.
In Specific Aim 1, we will look at how dynein-mediated transport is altered during disease onset and progression. We will investigate the specific mechanisms involved by analyzing the motility of proteins and organelles isolated from mouse models of neurodegenerative disease.
In Specific Aim 2, we will compare the cargos that are actively transported by dynein in wild type and degenerating neurons, using proteomic screens for dynein cargos. We hypothesize that changes in dynein cargos, especially signaling molecules, will result in alterations in the balance between survival and death signals. Finally, in Specific Aim 3, we will use cellular models of neurodegenerative disease to investigate how defects in axonal transport lead to neurodegeneration. We will examine the relative contributions of defects in the transport machinery and alterations in the cargo being transported, as well as defects in organelle trafficking and protein degradation. The studies proposed here will lead to a clearer understanding of the role of axonal transport in motor neuron degenerative disease. As disruption of intracellular trafficking has been observed in a growing number of degenerative and aging diseases, including Huntington's and Alzheimer's Disease, it is likely that the mechanistic studies proposed here will provide insights that are more broadly applicable to our understanding of neuronal degeneration. The active movement of proteins, vesicles, and organelles along the extended axons of neurons is called axonal transport. This transport is essential for the health and function of the neuron, and defects in the process cause motor neuron degeneration leading to muscle atrophy in diseases such as Amyotrophic Lateral Sclerosis (ALS or Lou Gehrig's Disease). Here, we propose to investigate the mechanisms by which defects in axonal transport, caused either directly by mutations in the motor proteins that drive this transport, or indirectly by the expression of other mutant proteins, lead to degenerative disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS060698-05
Application #
8270484
Study Section
Synapses, Cytoskeleton and Trafficking Study Section (SYN)
Program Officer
Gubitz, Amelie
Project Start
2008-07-01
Project End
2014-06-30
Budget Start
2012-07-01
Budget End
2014-06-30
Support Year
5
Fiscal Year
2012
Total Cost
$337,641
Indirect Cost
$123,266
Name
University of Pennsylvania
Department
Physiology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Wong, Yvette C; Holzbaur, Erika L F (2014) The regulation of autophagosome dynamics by huntingtin and HAP1 is disrupted by expression of mutant huntingtin, leading to defective cargo degradation. J Neurosci 34:1293-305
Wong, Yvette C; Holzbaur, Erika L F (2014) Optineurin is an autophagy receptor for damaged mitochondria in parkin-mediated mitophagy that is disrupted by an ALS-linked mutation. Proc Natl Acad Sci U S A 111:E4439-48
Maday, Sandra; Holzbaur, Erika L F (2014) Autophagosome biogenesis in primary neurons follows an ordered and spatially regulated pathway. Dev Cell 30:71-85
Castle, Michael J; Perlson, Eran; Holzbaur, Erika Lf et al. (2014) Long-distance axonal transport of AAV9 is driven by dynein and kinesin-2 and is trafficked in a highly motile Rab7-positive compartment. Mol Ther 22:554-66
Zhang, Jun; Twelvetrees, Alison E; Lazarus, Jacob E et al. (2013) Establishing a novel knock-in mouse line for studying neuronal cytoplasmic dynein under normal and pathologic conditions. Cytoskeleton (Hoboken) 70:215-27
Perlson, Eran; Hendricks, Adam G; Lazarus, Jacob E et al. (2013) Dynein interacts with the neural cell adhesion molecule (NCAM180) to tether dynamic microtubules and maintain synaptic density in cortical neurons. J Biol Chem 288:27812-24
Maday, Sandra; Wallace, Karen E; Holzbaur, Erika L F (2012) Autophagosomes initiate distally and mature during transport toward the cell soma in primary neurons. J Cell Biol 196:407-17
Heisler, Frank F; Loebrich, Sven; Pechmann, Yvonne et al. (2011) Muskelin regulates actin filament- and microtubule-based GABA(A) receptor transport in neurons. Neuron 70:66-81
Schapitz, Inga U; Behrend, Bardo; Pechmann, Yvonne et al. (2010) Neuroligin 1 is dynamically exchanged at postsynaptic sites. J Neurosci 30:12733-44
Perlson, Eran; Maday, Sandra; Fu, Meng-Meng et al. (2010) Retrograde axonal transport: pathways to cell death? Trends Neurosci 33:335-44

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