Human Molecular Genetics Advance Access originally published online on February 11, 2008
Human Molecular Genetics 2008 17(10):1446-1456; doi:10.1093/hmg/ddn033
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Dopamine determines the vulnerability of striatal neurons to the N-terminal fragment of mutant huntingtin through the regulation of mitochondrial complex II
1 Unité de Recherche Associée, Commissariat à l'Energie Atomique (CEA)—Centre Nationale de la Recherche Scientifique (CNRS) 2210, Service Hospitalier Frédéric Joliot, Service MIRCen, Institut d'Imagerie Biomédicale (I2BM), Direction des Sciences du Vivant, CEA, 4 place du Général Leclerc, 91401 Orsay Cedex, France 2 Commissariat à l'Energie Atomique (CEA), Institut de Biologie et Technologies de Saclay (iBiTecS), Service de Biologie Intégrative et Génétique Moléculaire (SBIGeM), Commissariat à l'Energie Atomique (CEA) Saclay, 91191 Gif- sur-Yvette Cedex, France 3 The Burnham Institute for Medical Research, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA
* To whom correspondence should be addressed at: Neuronal Death Group, URA CEA-CNRS 2210, Service Hospitalier Frédéric Joliot, Service MIRCen, I2BM, DSV, CEA, 4 place du Général Leclerc, 91401 Orsay Cedex, France. Tel: +33 169867815; Fax: +33 169867745; Email: emmanuel.brouillet{at}cea.fr
Received October 11, 2007; Accepted January 31, 2008
In neurodegenerative disorders associated with primary or secondary mitochondrial defects such as Huntington's disease (HD), cells of the striatum are particularly vulnerable to cell death, although the mechanisms by which this cell death is induced are unclear. Dopamine, found in high concentrations in the striatum, may play a role in striatal cell death. We show that in primary striatal cultures, dopamine increases the toxicity of an N-terminal fragment of mutated huntingtin (Htt-171-82Q). Mitochondrial complex II protein (mCII) levels are reduced in HD striatum, indicating that this protein may be important for dopamine-mediated striatal cell death. We found that dopamine enhances the toxicity of the selective mCII inhibitor, 3-nitropropionic acid. We also demonstrated that dopamine doses that are insufficient to produce cell loss regulate mCII expression at the mRNA, protein and catalytic activity level. We also show that dopamine-induced down-regulation of mCII levels can be blocked by several dopamine D2 receptor antagonists. Sustained overexpression of mCII subunits using lentiviral vectors abrogated the effects of dopamine, both by high dopamine concentrations alone and neuronal death induced by low dopamine concentrations together with Htt-171-82Q. This novel pathway links dopamine signaling and regulation of mCII activity and could play a key role in oxidative energy metabolism and explain the vulnerability of the striatum in neurodegenerative diseases.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.