Anne-Katrin Güttsches1, Stefen Brady2, Kathryn Krause1,3, Alexandra Maerkens1,3, Julian Uszkoreit3, Martin Eisenacher3, Anja Schreiner1, Sara Galozzi3, Janine Mertens-Rill1, Martin Tegenthoff1, Janice L Holton4,5, Matthew B Harms6, Thomas E Lloyd7, Matthias Vorgerd1, Conrad C Weihl8, Katrin Marcus3, Rudolf A Kley1. 1. Department of Neurology, Heimer Institute for Muscle Research, University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany. 2. Department of Neurology, Southmead Hospital, Bristol, United Kingdom. 3. Medizinisches Proteom-Center, Ruhr-University Bochum, Bochum, Germany. 4. MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, United Kingdom. 5. Department of Molecular Neuroscience, Queen Square Brain Bank, UCL Institute of Neurology, London, United Kingdom. 6. Department of Neurology, Columbia University, New York, NY. 7. Johns Hopkins University School of Medicine, Baltimore, MD. 8. Department of Neurology and Hope Center for Neurological Disorders, Washington University School of Medicine, Saint Louis, MO.
Abstract
OBJECTIVE: Sporadic inclusion body myositis (sIBM) pathogenesis is unknown; however, rimmed vacuoles (RVs) are a constant feature. We propose to identify proteins that accumulate within RVs. METHODS: RVs and intact myofibers were laser microdissected from skeletal muscle of 18 sIBM patients and analyzed by a sensitive mass spectrometry approach using label-free spectral count-based relative protein quantification. Whole exome sequencing was performed on 62 sIBM patients. Immunofluorescence was performed on patient and mouse skeletal muscle. RESULTS: A total of 213 proteins were enriched by >1.5 -fold in RVs compared to controls and included proteins previously reported to accumulate in sIBM tissue or when mutated cause myopathies with RVs. Proteins associated with protein folding and autophagy were the largest group represented. One autophagic adaptor protein not previously identified in sIBM was FYCO1. Rare missense coding FYCO1 variants were present in 11.3% of sIBM patients compared with 2.6% of controls (p = 0.003). FYCO1 colocalized at RVs with autophagic proteins such as MAP1LC3 and SQSTM1 in sIBM and other RV myopathies. One FYCO1 variant protein had reduced colocalization with MAP1LC3 when expressed in mouse muscle. INTERPRETATION: This study used an unbiased proteomic approach to identify RV proteins in sIBM that included a novel protein involved in sIBM pathogenesis. FYCO1 accumulates at RVs, and rare missense variants in FYCO1 are overrepresented in sIBM patients. These FYCO1 variants may impair autophagic function, leading to RV formation in sIBM patient muscle. FYCO1 functionally connects autophagic and endocytic pathways, supporting the hypothesis that impaired endolysosomal degradation underlies the pathogenesis of sIBM. Ann Neurol 2017;81:227-239.
OBJECTIVE: Sporadic inclusion body myositis (sIBM) pathogenesis is unknown; however, rimmed vacuoles (RVs) are a constant feature. We propose to identify proteins that accumulate within RVs. METHODS: RVs and intact myofibers were laser microdissected from skeletal muscle of 18 sIBM patients and analyzed by a sensitive mass spectrometry approach using label-free spectral count-based relative protein quantification. Whole exome sequencing was performed on 62 sIBM patients. Immunofluorescence was performed on patient and mouse skeletal muscle. RESULTS: A total of 213 proteins were enriched by >1.5 -fold in RVs compared to controls and included proteins previously reported to accumulate in sIBM tissue or when mutated cause myopathies with RVs. Proteins associated with protein folding and autophagy were the largest group represented. One autophagic adaptor protein not previously identified in sIBM was FYCO1. Rare missense coding FYCO1 variants were present in 11.3% of sIBM patients compared with 2.6% of controls (p = 0.003). FYCO1 colocalized at RVs with autophagic proteins such as MAP1LC3 and SQSTM1 in sIBM and other RVmyopathies. One FYCO1 variant protein had reduced colocalization with MAP1LC3 when expressed in mouse muscle. INTERPRETATION: This study used an unbiased proteomic approach to identify RV proteins in sIBM that included a novel protein involved in sIBM pathogenesis. FYCO1 accumulates at RVs, and rare missense variants in FYCO1 are overrepresented in sIBM patients. These FYCO1 variants may impair autophagic function, leading to RV formation in sIBM patient muscle. FYCO1 functionally connects autophagic and endocytic pathways, supporting the hypothesis that impaired endolysosomal degradation underlies the pathogenesis of sIBM. Ann Neurol 2017;81:227-239.
Authors: Daniel W Neef; Alex M Jaeger; Rocio Gomez-Pastor; Felix Willmund; Judith Frydman; Dennis J Thiele Journal: Cell Rep Date: 2014-10-30 Impact factor: 9.423
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