title: Histone deacetylase inhibition modulates kynurenine pathway activation in yeast, microglia, and mice expressing a mutant huntingtin fragment.
abstract: The kynurenine pathway of tryptophan degradation is hypothesized to play an important role in Huntington disease, a neurodegenerative disorder caused by a polyglutamine expansion in the protein huntingtin. Neurotoxic metabolites of the kynurenine pathway, generated in microglia and macrophages, are present at increased levels in the brains of patients and mouse models during early stages of disease, but the mechanism by which kynurenine pathway up-regulation occurs in Huntington disease is unknown. Here we report that expression of a mutant huntingtin fragment was sufficient to induce transcription of the kynurenine pathway in yeast and that this induction was abrogated by impairing the activity of the histone deacetylase Rpd3. Moreover, numerous genetic suppressors of mutant huntingtin toxicity that are functionally unrelated converged unexpectedly on the kynurenine pathway, supporting a critical role for the kynurenine pathway in mediating mutant huntingtin toxicity in yeast. Histone deacetylase-dependent regulation of the kynurenine pathway was also observed in a mouse model of Huntington disease, in which treatment with a neuroprotective histone deacetylase inhibitor blocked activation of the kynurenine pathway in microglia expressing a mutant huntingtin fragment in vitro and in vivo. These findings suggest that a mutant huntingtin fragment can perturb transcriptional programs in microglia, and thus implicate these cells as potential modulators of neurodegeneration in Huntington disease that are worthy of further investigation.
authors: Department of Pharmacology, University of Washington, Seattle, Washington 98195, USA.
authors: Flaviano
authors: F
authors: Giorgini
authors: Thomas
authors: T
authors: Möller
authors: Wanda
authors: W
authors: Kwan
authors: Daniel
authors: D
authors: Zwilling
authors: Jennifer L
authors: JL
authors: Wacker
authors: Soyon
authors: S
authors: Hong
authors: Li-Chun L
authors: LC
authors: Tsai
authors: Christine S
authors: CS
authors: Cheah
authors: Robert
authors: R
authors: Schwarcz
authors: Paolo
authors: P
authors: Guidetti
authors: Paul J
authors: PJ
authors: Muchowski
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D015870:Gene Expression; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007737:Kynurenine / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D017628:Microglia / Q000378:metabolism* / Q000473:pathology; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: C086055:HTT protein, human; C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D007737:Kynurenine; C071665:RPD3 protein, S cerevisiae; D006655:Histone Deacetylases