Kynurenine 3-Monooxygenase Interacts with Huntingtin at the Outer Mitochondrial Membrane
Aisha M. Swaih,
Carlo Breda,
Korrapati V. Sathyasaikumar,
Natalie Allcock,
Mary E. W. Collier,
Robert P. Mason,
Adam Feasby,
Federico Herrera,
Tiago F. Outeiro,
Robert Schwarcz,
Mariaelena Repici,
Flaviano Giorgini
Affiliations
Aisha M. Swaih
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
Carlo Breda
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
Korrapati V. Sathyasaikumar
Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD 21201, USA
Natalie Allcock
Core Biotechnology Services, Adrian Building, University of Leicester, University Road, Leicester LE1 7RH, UK
Mary E. W. Collier
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
Robert P. Mason
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
Adam Feasby
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
Federico Herrera
Cell Structure and Dynamics Laboratory, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
Tiago F. Outeiro
Department of Experimental Neurodegeneration, Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, 37073 Göttingen, Germany
Robert Schwarcz
Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD 21201, USA
Mariaelena Repici
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
Flaviano Giorgini
Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK
The flavoprotein kynurenine 3-monooxygenase (KMO) is localised to the outer mitochondrial membrane and catalyses the synthesis of 3-hydroxykynurenine from L-kynurenine, a key step in the kynurenine pathway (KP) of tryptophan degradation. Perturbation of KP metabolism due to inflammation has long been associated with the pathogenesis of several neurodegenerative disorders, including Huntington’s disease (HD)—which is caused by the expansion of a polyglutamine stretch in the huntingtin (HTT) protein. While HTT is primarily localised to the cytoplasm, it also associates with mitochondria, where it may physically interact with KMO. In order to test this hypothesis, we employed bimolecular fluorescence complementation (BiFC) and found that KMO physically interacts with soluble HTT exon 1 protein fragment in living cells. Notably, expansion of the disease-causing polyglutamine tract in HTT leads to the formation of proteinaceous intracellular inclusions that disrupt this interaction with KMO, markedly decreasing BiFC efficiency. Using confocal microscopy and ultrastructural analysis, we determined KMO and HTT localisation within the cell and found that the KMO-HTT interaction is localized to the outer mitochondrial membrane. These data suggest that KMO may interact with a pool of HTT at the mitochondrial membrane, highlighting a possible physiological role for mitochondrial HTT. The KMO-HTT interaction is abrogated upon polyglutamine expansion, which may indicate a heretofore unrecognized relevance in the pathogenesis of this disorder.
