The broad, long-term objective of the project is to understand the causes of neurodegeneration in Huntington's disease (HD). In HD polyglutamine-expanded Huntingtin (Httexp) causes early synaptic dysfunction and eventual neurodegeneration through poorly understood mechanisms. We previously discovered that Httexp binds to and sensitizes inositol 1,4,5-triphosphate receptor 1 (InsP3R1) to InsP3. We also demonstrated that a novel inhibitor of neuronal store-operated calcium entry (nSOC) improved motor symptoms in transgenic HD flies and inhibited and neurodegeneration in YAC128 HD mouse medium spiny neurons (MSNs), the primary cell type affected in HD. Based on these results, we propose that excessive activation of InsP3R1 causes a persistent reduction in endoplasmic reticulum (ER) calcium levels, elevated nSOC and neuronal and dendritic spine loss in HD-afflicted MSNs. To test this hypothesis, we will focus on the following aims: 1. To evaluate the causes and importance of supranormal nSOC in synaptic loss in HD MSNs To test the role of InsP3R1, we will use antisense oligonucleotides (ASOs) to knockdown InsP3R1 expression in YAC128 MSNs. We will also reduce levels of InsP3 by overexpressing a 5PP-RA phosphatase that metabolizes InsP3. To test the role of nSOC more directly we will use genetic strategies to knockout or knockdown STIM2, a regulator of synaptic nSOC. The effects of suppression of InsP3R1- and STIM2- mediated signaling will be evaluated in vitro and in vivo in experiments with the YAC128 HD mouse model. 2. To investigate the role of sigma 1 receptor (S1R) in HD and to evaluate S1R as a potential therapeutic target. Sigma 1 receptor (S1R) is an ER-resident protein that is activated in response to ER stress and ER calcium depletion. Activated S1R is thought to promote neuroprotection and stabilize InsP3R function, which may protect MSNs and their synaptic connections. Our preliminary data indicates upregulation of S1R in the striatum of both aged YAC128 mice and human HD patients. We will study changes in S1R- mediated signaling in the HD-afflicted striatum and investigate the potential relationship between S1R and ER Ca2+ signaling in HD MSN spines. We will also use a variety of pharmacological and molecular tools to validate S1R as a novel therapeutic target for HD. In these studies we will evaluate potential roles of dysregulated ER Ca2+ signaling, nSOC and S1R in synaptic loss in HD MSNs. We will also appraise InsP3R1, STIM2 and S1R as potential therapeutic targets for HD.

Public Health Relevance

The proposed project will have direct and immediate relevance for public health. Huntington's disease (HD) is a major cause of dementia in the elderly and an enormous health problem. The experiments described in the grant are aimed at testing specific hypothesis regarding pathogenesis of HD and will provide information critical for eventual development of the cure.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS056224-08
Application #
9431245
Study Section
Cellular and Molecular Biology of Neurodegeneration Study Section (CMND)
Program Officer
Miller, Daniel L
Project Start
2007-12-15
Project End
2021-01-31
Budget Start
2018-02-01
Budget End
2019-01-31
Support Year
8
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Physiology
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
Wu, Jun; Ryskamp, Daniel; Birnbaumer, Lutz et al. (2018) Inhibition of TRPC1-Dependent Store-Operated Calcium Entry Improves Synaptic Stability and Motor Performance in a Mouse Model of Huntington's Disease. J Huntingtons Dis 7:35-50
Egorova, Polina A; Gavrilova, Alexandra V; Bezprozvanny, Ilya B (2018) In Vivo Analysis of the Climbing Fiber-Purkinje Cell Circuit in SCA2-58Q Transgenic Mouse Model. Cerebellum :
Pchitskaya, Ekaterina; Popugaeva, Elena; Bezprozvanny, Ilya (2018) Calcium signaling and molecular mechanisms underlying neurodegenerative diseases. Cell Calcium 70:87-94
Ryskamp, Daniel; Wu, Jun; Geva, Michal et al. (2017) The sigma-1 receptor mediates the beneficial effects of pridopidine in a mouse model of Huntington disease. Neurobiol Dis 97:46-59
Zhemkov, Vladimir A; Kulminskaya, Anna A; Bezprozvanny, Ilya B et al. (2016) The 2.2-Angstrom resolution crystal structure of the carboxy-terminal region of ataxin-3. FEBS Open Bio 6:168-78
Wu, Jun; Ryskamp, Daniel A; Liang, Xia et al. (2016) Enhanced Store-Operated Calcium Entry Leads to Striatal Synaptic Loss in a Huntington's Disease Mouse Model. J Neurosci 36:125-41
Egorova, Polina A; Zakharova, Olga A; Vlasova, Olga L et al. (2016) In vivo analysis of cerebellar Purkinje cell activity in SCA2 transgenic mouse model. J Neurophysiol 115:2840-51
Zhang, Zilai; Cao, Mou; Chang, Chia-Wei et al. (2016) Autism-Associated Chromatin Regulator Brg1/SmarcA4 Is Required for Synapse Development and Myocyte Enhancer Factor 2-Mediated Synapse Remodeling. Mol Cell Biol 36:70-83
Egorova, Polina; Popugaeva, Elena; Bezprozvanny, Ilya (2015) Disturbed calcium signaling in spinocerebellar ataxias and Alzheimer's disease. Semin Cell Dev Biol 40:127-33
Fedorenko, Olena A; Popugaeva, Elena; Enomoto, Masahiro et al. (2014) Intracellular calcium channels: inositol-1,4,5-trisphosphate receptors. Eur J Pharmacol 739:39-48

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