Oxidative stress, ubiquitination defects, and mitochondrial dysfunction are well recognized markers of various neurodegenerative diseases. This proposal is designed to elucidate the mechanism whereby the signaling scaffold, p62, regulates trafficking and removal of ubiquitinated proteins and damaged mitochondria.
The specific aims of this proposal are based upon the CENTRAL HYPOTHESIS that p62 is involved in the transport of proteins to the proteasome or autophagosome, employing a common tag, K63-polyubiquitin. Sequestosome 1/p62 is predominantly expressed in the hippocampus, the center of learning and memory, where it serves as a scaffold to regulate the trafficking of K63-polyubiquitinated proteins and phosphorylation of atypical protein kinase C iota/lambda substrates. Gene-targeted deletion of p62 in mice causes oxidative stress leading to Alzheimer-like characteristics such as tau-phosphorylation, loss of short term memory and synaptic plasticity, reduced serum BDNF, depression, anxiety, along with accumulation of highly insoluble polyubiquitinated proteins in the adult mice. Humans with AD likewise exhibit reduced p62 levels in hippocampus that correlate with accumulation of insoluble polyubiquitinated tau. These findings suggest that a reduced amount of p62 may act in conjunction with other environmental or genetic factors to influence susceptibility to development of AD. Our long term goal is to understand the mechanism whereby removal of p62 in the brain results in oxidative stress that contributes to development of mouse AD. Our preliminary findings reveal that p62 converges upon HDAC6 to regulate it activity and thereby influences tubulin acetylation, leading to impaired clearance of aggregated proteins. Along with p62's role in autophagy the elimination of damaged mitochondria is impaired, which together with appearance of ubiquitin aggregates results in oxidative stress. The following specific aims are proposed to further elucidate the p62 regulatory pathway.
Specific Aim 1 will examine the mechanism whereby p62 cooperates with HDAC6 to regulate clearance of aggregated polyubiquitinated proteins.
Specific Aim 2 will examine the mechanism whereby p62 regulates the trafficking, clearance and energetics of mitochondria.
Specific Aim 3 will define p62's role in mediating oxidative stress resistance. An innovative approach employing various complementary methods will be undertaken within the scope of the project. These findings are likely to provide insight into mechanism whereby p62 function impinges upon energetics and form of mitochondria, trafficking of interacting proteins, as well as, accumulation of polyubiquitin aggregates. Altogether, further knowledge of p62 may contribute to new treatments for AD, as well as, other neurodegenerative diseases.

Public Health Relevance

This project will tease apart the function of the scaffolding protein p62. The innovative aspect of this project is that the role of p62 in trafficking of tau and other interacting proteins is largely undefined. P62 is a multifunctional protein involved in both of the two major protein degradation mechanisms, ubiquitin proteasome system and autophagy-lysosome pathway.
The specific aims of this proposal are based upon the CENTRAL HYPOTHESIS that p62 is a novel shuttling factor that participates in the transport of proteins to the proteasome, autophagosome and removal of damaged mitochondria. Three synergistic but non-overlapping specific aims are proposed to further unravel the mechanistic details regarding the role of p62 in vivo.
Aim 1 will illuminate the means by which p62 regulates clearance of aggregated proteins.
Aim 2 will elucidate the mechanism whereby p62 regulates the trafficking and clearance of mitochondria.
Aim 3 will define p62's role in mediating oxidative stress resistance. The results from this study will provide invaluable insights into the role of p62 in clearance of misfolded protein aggregates and neurodegeneration. These findings may provide an avenue to develop new therapeutics for the treatment of Alzheimer's disease as well as other neurodegenerative diseases, which possess disturbances in p62 expression as a component of their underlying pathophysiology.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Neural Oxidative Metabolism and Death Study Section (NOMD)
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Corriveau, Roderick A
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Auburn University at Auburn
Schools of Arts and Sciences
Auburn University
United States
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Seibenhener, Michael L; Wooten, Michael C (2015) Use of the Open Field Maze to measure locomotor and anxiety-like behavior in mice. J Vis Exp :e52434
Du, Yifeng; Seibenhener, Michael L; Yan, Jin et al. (2015) aPKC phosphorylation of HDAC6 results in increased deacetylation activity. PLoS One 10:e0123191
Calderilla-Barbosa, Luis; Seibenhener, M Lamar; Du, Yifeng et al. (2014) Interaction of SQSTM1 with the motor protein dynein--SQSTM1 is required for normal dynein function and trafficking. J Cell Sci 127:4052-63
Seibenhener, M Lamar; Du, Yifeng; Diaz-Meco, Maria-Theresa et al. (2013) A role for sequestosome 1/p62 in mitochondrial dynamics, import and genome integrity. Biochim Biophys Acta 1833:452-9
Seibenhener, M Lamar; Zhao, Ting; Du, Yifeng et al. (2013) Behavioral effects of SQSTM1/p62 overexpression in mice: support for a mitochondrial role in depression and anxiety. Behav Brain Res 248:94-103
Yan, Jin; Seibenhener, Michael Lamar; Calderilla-Barbosa, Luis et al. (2013) SQSTM1/p62 interacts with HDAC6 and regulates deacetylase activity. PLoS One 8:e76016
Seibenhener, Michael L; Wooten, Marie W (2012) Isolation and culture of hippocampal neurons from prenatal mice. J Vis Exp :
Du, Yifeng; Wooten, Michael C; Gearing, Marla et al. (2009) Age-associated oxidative damage to the p62 promoter: implications for Alzheimer disease. Free Radic Biol Med 46:492-501
Jadhav, Trafina; Wooten, Marie W (2009) Defining an Embedded Code for Protein Ubiquitination. J Proteomics Bioinform 2:316
Jiang, Jianxiong; Parameshwaran, Kodeeswaran; Seibenhener, M Lamar et al. (2009) AMPA receptor trafficking and synaptic plasticity require SQSTM1/p62. Hippocampus 19:392-406

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