The sphingolipid storage diseases are a group of ~40 genetically distinct disorders that result from inherited deficiencies of lysosomal hydrolytic activities or lipid transport. Among this group is Niemann-Pick C disease, an autosomal recessive disorder for which there is no effective treatment. Niemann-Pick C patients exhibit a clinically heterogeneous phenotype characterized by severe, progressive neurological impairment that is usually fatal in childhood. Most cases are caused by loss-of-function mutations in the NPC1 gene, resulting in impaired intracellular trafficking of cholesterol and glycosphingolipids. Despite increased knowledge of how NPC1 facilitates intracellular lipid transport, it remains poorly understood how mutations in this gene lead to the severe neuropathology by which this disorder is characterized. This lack of knowledge hinders the identification of specific targets for developing disease-modifying therapies. The objective of this application is to identify mechanisms leading to neurodegeneration and to define cellular pathways where interventions could result in effective treatments. Our central hypothesis is that neurological disease is governed by Npc1 deficiency in neurons by triggering neuron loss and impairing protein quality control. This hypothesis springs from our analysis of mice we generated with a conditional null allele of the Npc1 gene, thereby creating a novel tool for studying disease pathogenesis. Our preliminary studies show that Npc1 deletion in Purkinje cells is sufficient to trigger neuron loss in anterior, but not posterior cerebellar lobules. Our findings demonstrate that these subpopulations of neurons exhibit strikingly different vulnerability to the toxicity of Npc1 deficiency, and we hypothesize that this reflects underlying differences in gene expression. Further, we demonstrate that Npc1 deficiency impairs lysosomal protein quality control and hypothesize that defects in proteostasis underlie neuron loss. Behavioral, histological, biochemical and genetic approaches will be used to establish the extent to which Npc1 deficiency in neurons is sufficient to cause neurological disease (Aim 1), identify genes that protect neurons from the toxicity of Npc1 deficiency (Aim 2), and characterize the contribution of impaired proteostasis in Niemann-Pick C neurodegeneration (Aim 3). These studies are expected to have an important positive impact by defining pathways through which Npc1 deficiency leads to progressive neurodegeneration and by identifying potential therapeutic targets. Further, we expect that shared mechanisms mediate toxicity in several sphingolipid storage diseases, suggesting that advances here will impact our understanding and treatment approaches to genetically distinct lysosomal storage disorders.

Public Health Relevance

of the proposed studies to public health is that they will help unravel the mechanisms of neurodegeneration in Niemann-Pick C disease. Understanding these pathways is the first step toward the identification of disease-modifying therapies for patients with this disorder and related lipid storage diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS063967-05
Application #
8501700
Study Section
Developmental Brain Disorders Study Section (DBD)
Program Officer
Morris, Jill A
Project Start
2008-12-01
Project End
2016-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
5
Fiscal Year
2013
Total Cost
$322,579
Indirect Cost
$111,485
Name
University of Michigan Ann Arbor
Department
Pathology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Liu, Elaine A; Lieberman, Andrew P (2018) The intersection of lysosomal and endoplasmic reticulum calcium with autophagy defects in lysosomal diseases. Neurosci Lett :
Gurda, Brittney L; Bagel, Jessica H; Fisher, Samantha J et al. (2018) LC3 Immunostaining in the Inferior Olivary Nuclei of Cats With Niemann-Pick Disease Type C1 Is Associated With Patterned Purkinje Cell Loss. J Neuropathol Exp Neurol 77:229-245
Chung, Chan; Elrick, Matthew J; Dell'Orco, James M et al. (2016) Heat Shock Protein Beta-1 Modifies Anterior to Posterior Purkinje Cell Vulnerability in a Mouse Model of Niemann-Pick Type C Disease. PLoS Genet 12:e1006042
Chung, Chan; Puthanveetil, Prasanth; Ory, Daniel S et al. (2016) Genetic and pharmacological evidence implicates cathepsins in Niemann-Pick C cerebellar degeneration. Hum Mol Genet 25:1434-46
Schultz, Mark L; Krus, Kelsey L; Lieberman, Andrew P (2016) Lysosome and endoplasmic reticulum quality control pathways in Niemann-Pick type C disease. Brain Res 1649:181-188
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Elrick, Matthew J; Lieberman, Andrew P (2013) Autophagic dysfunction in a lysosomal storage disorder due to impaired proteolysis. Autophagy 9:234-5
Shen, Dongbiao; Wang, Xiang; Li, Xinran et al. (2012) Lipid storage disorders block lysosomal trafficking by inhibiting a TRP channel and lysosomal calcium release. Nat Commun 3:731

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