Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a pathological expansion of a polyglutamine domain within the protein huntingtin. The precise mechanisms involved in the etiology are still unknown, however there is evidence that impaired mitochondrial function is likely an important factor in HD. A possible clue to the pathogenesis of HD came with the discovery of neuronal intranuclear and cytoplasmic inclusions composed of mutant huntingtin. It has been suggested that Tissue Transglutaminase (tTG) may be a contributing factor to the formation of these aggregates. Tissue TG is a calcium-dependent transamidating enzyme that catalyzed the formation of isopeptide bonds between specific proteins to produce insoluble polymeric structures. Recently we have demonstrated that TG activity and tTG levels are significantly increased in specific brain regions affected by the disease as compared to control cases. Further, studies from the laboratory demonstrated that tTG associates with a truncated huntingtin protein and activation of tTG resulted in the modification of specific proteins associated only with the mutant truncated huntingtin protein. These results suggest that tTG may have a role in the etiology of HD. Our working hypothesis is that impaired mitochondrial function results in an increase in tTG activity and this subsequently results in an increased association of tTG with truncated huntingtin and modification of specific mutant huntingtin associated protein. In this proposal the majority of the experiments will be carried out in human neuroblastoma cells that express in a stable or inducible manner, physiological or pathological huntingtin protein constructs. In this proposal we will: (1) test the hypothesis that mitochondria impairment results in an increase in TG activity, and that the presence of mutant huntingtin potentiates this response, (2) test the hypothesis that tTG interacts selectively with the N-terminal truncated huntingtin protein, and that mitochondria impairment results in an increase in this interaction, (3) test the hypothesis that tTG contributes to the formation and/or stabilization of the aggregates, and that mitochondrial impairment may potentiate this effect, and (4) identify the mutant huntingtin-associated proteins that are tTG substrates and test the hypothesis that modification of these proteins may contribute to the selective neuronal death in HD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS041552-04
Application #
6721314
Study Section
Special Emphasis Panel (ZRG1-BDCN-4 (01))
Program Officer
Oliver, Eugene J
Project Start
2001-04-01
Project End
2006-03-31
Budget Start
2004-04-01
Budget End
2006-03-31
Support Year
4
Fiscal Year
2004
Total Cost
$215,250
Indirect Cost
Name
University of Alabama Birmingham
Department
Psychiatry
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
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Mao, Zhengkuan; Choo, Yeun Su; Lesort, Mathieu (2006) Cystamine and cysteamine prevent 3-NP-induced mitochondrial depolarization of Huntington's disease knock-in striatal cells. Eur J Neurosci 23:1701-10
Choo, Yeun Su; Mao, Zhengkuan; Johnson, Gail V W et al. (2005) Increased glutathione levels in cortical and striatal mitochondria of the R6/2 Huntington's disease mouse model. Neurosci Lett 386:63-8
Seong, Ihn Sik; Ivanova, Elena; Lee, Jong-Min et al. (2005) HD CAG repeat implicates a dominant property of huntingtin in mitochondrial energy metabolism. Hum Mol Genet 14:2871-80
Hunter, Jesse M; Crouse, Andrew B; Lesort, Mathieu et al. (2005) Verification of somatic CAG repeat expansion by pre-PCR fractionation. J Neurosci Methods 144:11-7
Choo, Yeun Su; Johnson, Gail V W; MacDonald, Marcy et al. (2004) Mutant huntingtin directly increases susceptibility of mitochondria to the calcium-induced permeability transition and cytochrome c release. Hum Mol Genet 13:1407-20
Lesort, Mathieu; Lee, Matthew; Tucholski, Janusz et al. (2003) Cystamine inhibits caspase activity. Implications for the treatment of polyglutamine disorders. J Biol Chem 278:3825-30
Chun, Wanjoo; Lesort, Mathieu; Lee, Matthew et al. (2002) Transient osmotic stress facilitates mutant huntingtin aggregation. Neuroreport 13:2543-6