Mitochondrial dynamics, manifest as ability of mitochondria to change morphology and motility, play a vital role in neuronal response to fluctuating energy demands. Impairment of mitochondrial dynamics contributes to different disorders such as Alzheimer?s, Parkinson?s, and Huntington?s diseases (HD). In HD, interaction of mutant huntingtin (mHtt) with dynamin related protein 1 (Drp1) results in an increased Drp1 activity, leading to augmented mitochondrial fission, accompanied by reduced mitochondrial traffic. Despite significant effort, the molecular mechanisms, leading to mHtt-induced changes in mitochondrial morphology and motility are not completely understood. In preliminary experiments, we found that CRMP2, a protein implicated in axon guidance and regulation of neurite outgrowth, regulates mitochondrial dynamics. A mechanistic link between CRMP2 and regulation of mitochondrial dynamics has never been investigated. CRMP2 binds to neuronal mitochondria and in its dephosphorylated form to mHtt. CRMP2 physically interacts with Drp1, Mitofusin 2, and Miro 2, proteins involved in regulation of mitochondrial fission, fusion, and motility, respectively. Downregulation of CRMP2 with siRNA leads to increased fission and reduced mitochondrial traffic, implicating CRMP2 in regulation of mitochondrial dynamics. CRMP2 hyperphosphorylation after inhibition of protein phosphatases 1 and 2A correlates with augmented fission and reduced mitochondrial traffic. Conversely, decreasing CRMP2 phosphorylation can prevent these alterations. Finally, we found CRMP2 downregulation and hyperphosphorylation in striatal tissues from YAC128 HD mouse model and in postmortem striatal tissues of HD patients. Overall, the literature and our preliminary data strongly suggest that CRMP2 is involved in regulation of mitochondrial morphology and motility and CRMP2 hyperphosphorylation contributes to HD pathogenesis leading to excessive fission, reduced mitochondrial traffic, and neuronal loss. Dephosphorylated CRMP2 binds to mHtt and to proteins involved in mitochondrial dynamics and reduces their activities, whereas CRMP2 downregulation and hyperphosphorylation disrupts these protein-protein interactions, liberates binding partners of CRMP2, and increases their activities.
In Aim 1, we will determine CRMP2 localization in mitochondria, establish protein interaction partners, and assess the extent to which CRMP2 regulates mitochondrial dynamics in neurons.
In Aim 2, the mechanisms of CRMP2-medited regulation of mitochondrial dynamics will be determined.
In Aim 3, we will establish CRMP2-mediated mechanisms contributing to defects of mitochondrial dynamics and cell death in human neurons expressing mHtt. Finally, in Aim 4, we will assess to what extent CRMP2 dephosphorylation alters protein-protein interactions, protects neurons, and corrects behavioral deficits in animal models of HD. The proposed study will considerably improve our understanding of HD pathophysiology, lay a solid foundation for identifying new mechanisms of HD pathogenesis, and open novel avenues in HD research.

Public Health Relevance

Huntington?s disease (HD) is a neurodegenerative disorder characterized by mutations in huntingtin protein (Htt) and a loss of neurons in certain areas of the brain. The link between mutation in Htt and development of HD pathology is not clear and, consequently, there is no treatment against HD. The proposed study will improve our understanding of HD pathology, lay a foundation for discovering new mechanisms of HD and lead to development of new therapies for HD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS098772-01A1
Application #
9316237
Study Section
Special Emphasis Panel (ZRG1-MDCN-Q (03)M)
Program Officer
Miller, Daniel L
Project Start
2017-04-01
Project End
2022-02-28
Budget Start
2017-04-01
Budget End
2018-02-28
Support Year
1
Fiscal Year
2017
Total Cost
$574,526
Indirect Cost
$136,364
Name
Indiana University-Purdue University at Indianapolis
Department
Pharmacology
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
Moutal, Aubin; Villa, Lex Salas; Yeon, Seul Ki et al. (2017) CRMP2 Phosphorylation Drives Glioblastoma Cell Proliferation. Mol Neurobiol :