title: Defects in optineurin- and myosin VI-mediated cellular trafficking in amyotrophic lateral sclerosis.
abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder primarily affecting motor neurons. Mutations in optineurin cause a small proportion of familial ALS cases, and wild-type (WT) optineurin is misfolded and forms inclusions in sporadic ALS patient motor neurons. However, it is unknown how optineurin mutation or misfolding leads to ALS. Optineurin acts an adaptor protein connecting the molecular motor myosin VI to secretory vesicles and autophagosomes. Here, we demonstrate that ALS-linked mutations p.Q398X and p.E478G disrupt the association of optineurin with myosin VI, leading to an abnormal diffuse cytoplasmic distribution, inhibition of secretory protein trafficking, endoplasmic reticulum (ER) stress and Golgi fragmentation in motor neuron-like NSC-34 cells. We also provide further insight into the role of optineurin as an autophagy receptor. WT optineurin associated with lysosomes and promoted autophagosome fusion to lysosomes in neuronal cells, implying that it mediates trafficking of lysosomes during autophagy in association with myosin VI. However, either expression of ALS mutant optineurin or small interfering RNA-mediated knockdown of endogenous optineurin blocked lysosome fusion to autophagosomes, resulting in autophagosome accumulation. Together these results indicate that ALS-linked mutations in optineurin disrupt myosin VI-mediated intracellular trafficking processes. In addition, in control human patient tissues, optineurin displayed its normal vesicular localization, but in sporadic ALS patient tissues, vesicles were present in a significantly decreased proportion of motor neurons. Optineurin binding to myosin VI was also decreased in tissue lysates from sporadic ALS spinal cords. This study therefore links several previously described pathological mechanisms in ALS, including defects in autophagy, fragmentation of the Golgi and induction of ER stress, to disruption of optineurin function. These findings also indicate that optineurin-myosin VI dysfunction is a common feature of both sporadic and familial ALS.
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia.
authors: Vinod
authors: V
authors: Sundaramoorthy
authors: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia.
authors: Adam K
authors: AK
authors: Walker
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and.
authors: Vanessa
authors: V
authors: Tan
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and.
authors: Jennifer A
authors: JA
authors: Fifita
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and.
authors: Emily P
authors: EP
authors: Mccann
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and.
authors: Kelly L
authors: KL
authors: Williams
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and.
authors: Ian P
authors: IP
authors: Blair
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and.
authors: Gilles J
authors: GJ
authors: Guillemin
authors: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia.
authors: Manal A
authors: MA
authors: Farg
authors: Department of Biomedical Sciences, Faculty of Medicine & Health Sciences, Macquarie University, NSW 2109, Australia and Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia julie.atkin@mq.edu.au.
authors: Julie D
authors: JD
authors: Atkin
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D026901:Membrane Transport Proteins; D051379:Mice; D009046:Motor Neurons / Q000378:metabolism; D020125:Mutation, Missense; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism; D035582:Transcription Factor TFIIIA / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D005136:Eye Proteins; D026901:Membrane Transport Proteins; C409460:OPTN protein, human; C501288:Optn protein, mouse; D035582:Transcription Factor TFIIIA; C089785:myosin VI; D018995:Myosin Heavy Chains