Genomes and Genes
Mechanisms of Ubiquitin Trafficking in Neurons
Principal Investigator: Michael C Wooten
Abstract: DESCRIPTION (provided by applicant): 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.
Funding Period: 1995-08-01 - 2014-12-31
more information: NIH RePORT
- Sequestosome 1/p62--more than just a scaffoldM Lamar Seibenhener
Department of Biological Sciences, Program in Cellular and Molecular Biosciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849, United States
FEBS Lett 581:175-9. 2007..Sequestosome 1/p62 is a protein that is gaining attention as it is intimately involved in cell signaling, receptor internalization, and protein turnover. Herein we review recent advances in the field...
- Behavioral effects of SQSTM1/p62 overexpression in mice: support for a mitochondrial role in depression and anxietyM Lamar Seibenhener
Dept Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36832, USA
Behav Brain Res 248:94-103. 2013..These results suggest that SQSTM1/p62 provides an attractive target for therapeutic agents potentially suitable for the treatment of anxiety and affective spectrum disorders...
- A role for sequestosome 1/p62 in mitochondrial dynamics, import and genome integrityM Lamar Seibenhener
Department of Biological Sciences, Cellular and Molecular Biosciences Program, Auburn University, AL 36849, USA
Biochim Biophys Acta 1833:452-9. 2013..We present evidence that these responses to the presence of p62 extend beyond the protein's immediate influence on membrane potential...
- Oxidative damage to the promoter region of SQSTM1/p62 is common to neurodegenerative diseaseYifeng Du
Department of Biological Sciences, Cellular and Molecular Biosciences Program, 331 Funchess Hall, Auburn University, AL 38849, USA
Neurobiol Dis 35:302-10. 2009..Altogether these results suggest that pharmacological means to increase p62 expression may be beneficial in delaying the onset of neurodegeneration...
- Age-associated oxidative damage to the p62 promoter: implications for Alzheimer diseaseYifeng Du
Cellular and Molecular Biosciences Program, Department of Biological Sciences, Auburn University, AL 38849, USA
Free Radic Biol Med 46:492-501. 2009..Altogether, our results reveal that oxidative damage to the p62 promoter correlates with decreased expression of p62 and may contribute to age-associated neurodegenerative disease such as AD and others...
- AMPA receptor trafficking and synaptic plasticity require SQSTM1/p62Jianxiong Jiang
Department of Biological Sciences and Program in Cellular and Molecular Biosciences, Auburn University, Auburn, Alabama 36849, USA
Hippocampus 19:392-406. 2009..These findings support a model where p62 interaction and aPKC phosphorylation act together to mediate AMPA receptor trafficking and long-term synaptic plasticity in the hippocampus...
- p62 serves as a shuttling factor for TrkA interaction with the proteasomeThangiah Geetha
Department of Biological Sciences, Program in Cellular and Molecular Biosciences, Auburn University, Auburn, AL 36849, USA
Biochem Biophys Res Commun 374:33-7. 2008..These findings reveal that p62 serves as a shuttling factor for interaction of ubiquitinated substrates with the proteasome and could promote localized protein turnover in neurons...
- Identification of a consensus site for TRAF6/p62 polyubiquitinationTrafina Jadhav
Program in Cellular and Molecular Biosciences, Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA
Biochem Biophys Res Commun 371:521-4. 2008..These findings reveal a possible selection process for targeting a specific lysine residue by a single E3 ligase and underscore the role of the scaffold, p62, in this process...
- Genetic inactivation of p62 leads to accumulation of hyperphosphorylated tau and neurodegenerationJ Ramesh Babu
Department of Biological Sciences, Program in Cellular and Molecular Biosciences, Auburn University, Auburn, Alabama 36849, USA
J Neurochem 106:107-20. 2008..Thus, these findings provide new insight into manifestation of sporadic Alzheimer disease and the impact of obesity...
- Essential role of sequestosome 1/p62 in regulating accumulation of Lys63-ubiquitinated proteinsMarie W Wooten
Department of Biological Sciences, Program in Cell and Molecular Biosciences, Auburn University, Auburn, Alabama 36849, USA
J Biol Chem 283:6783-9. 2008..Thus, p62 has a bifunctional role in regulation of an E3 ubiquitin-protein ligase, TRAF6, and a DUB, CYLD, to balance the turnover of Lys63-polyubiquitinated proteins such as TrkA...
- Posttranslational modifications and receptor-associated proteins in AMPA receptor trafficking and synaptic plasticityJianxiong Jiang
Department of Biological Sciences and Program in Cellular and Molecular Biosciences, Auburn University, AL 36849, USA
Neurosignals 15:266-82. 2006..Here, we summarize recent studies on posttranslational modifications and associated proteins of AMPAR subunits, and their roles in receptor trafficking and synaptic plasticity...
- Unc-51-like kinase 1/2-mediated endocytic processes regulate filopodia extension and branching of sensory axonsXiang Zhou
Department of Cell Biology, Duke University Medical School, Durham, NC 27710, USA
Proc Natl Acad Sci U S A 104:5842-7. 2007..These results and additional studies suggest that Ulk1/2 proteins regulate filopodia extension and neurite branching during sensory axon outgrowth, probably through regulating TrkA receptor trafficking and signaling...
- SQSTM1/p62 interacts with HDAC6 and regulates deacetylase activityJin Yan
Department of Biological Sciences, Cellular and Molecular Biosciences Program, Auburn University, Auburn, Alabama, United States of America
PLoS ONE 8:e76016. 2013..Thus, our findings indicate that p62 plays a key role in regulating the recruitment of F-actin network assemblies to the MTOC, a critical cellular function that is required for successful autophagic clearance of protein aggregates. ..