Proteomic characterisation of polyglucosan bodies in skeletal muscle in RBCK1 deficiency. (12th September 2021)

• Record Type: Journal Article
• Authors: Thomsen, Christer; Malfatti, Edoardo; Jovanovic, Ana; Roberts, Mark; Kalev, Ognian; Lindberg, Christopher; Oldfors, Anders
• Is Part Of: Neuropathology & applied neurobiology. Volume 48:Number 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-12
• Subjects: glycogen metabolism -- glycogen storage disease -- polyglucosan -- protein aggregation; Nervous system -- Diseases -- Pathology -- Periodicals; Nervous system -- Diseases -- Periodicals; 616.8
• DOI: 10.1111/nan.12761
• Languages: English
• ISSNs: 0305-1846

Abstract

Abstract: Aims: Several neurodegenerative and neuromuscular disorders are characterised by storage of polyglucosan, consisting of proteins and amylopectin‐like polysaccharides, which are less branched than in normal glycogen. Such diseases include Lafora disease, branching enzyme deficiency, glycogenin‐1 deficiency, polyglucosan body myopathy type 1 (PGBM1) due to RBCK1 deficiency and others. The protein composition of polyglucosan bodies is largely unknown. Methods: We combined quantitative mass spectrometry, immunohistochemical and western blot analyses to identify the principal protein components of polyglucosan bodies in PGBM1. Histologically stained tissue sections of skeletal muscle from four patients were used to isolate polyglucosan deposits and control regions by laser microdissection. Prior to mass spectrometry, samples were labelled with tandem mass tags that enable quantitative comparison and multiplexed analysis of dissected samples. To study the distribution and expression of the accumulated proteins, immunohistochemical and western blot analyses were performed. Results: Accumulated proteins were mainly components of glycogen metabolism and protein quality control pathways. The majority of fibres showed depletion of glycogen and redistribution of key enzymes of glycogen metabolism to the polyglucosan bodies. The polyglucosan bodies also showed accumulation of proteins involved in the ubiquitin‐proteasome and autophagocytosis systems and protein chaperones. Conclusions: The sequestration of key enzymes of glycogen metabolism to the polyglucosan bodies may explain the glycogen depletion in the fibres and muscle function impairment. The accumulation of components of the protein quality control systems and other proteins frequently found in protein aggregate disorders indicates that protein aggregation may be an essential part of the pathobiology of polyglucosan storage. Abstract : Polyglucosan bodies contain amylopectin‐like polysaccharides together with an undefined protein component. By combining laser microdissection, quantitative mass spectrometry and immunohistochemistry, we show that the principal accumulated proteins in polyglucosan body myopathy 1 are associated with glycogen metabolism and the ubiquitin‐proteasome, autophagy and chaperone systems. Sequestration of glycogen‐related enzymes to polyglucosan may explain the observed glycogen depletion and impaired muscle function, although recruitment of protein quality control systems indicates that protein aggregation is essential for the pathobiology of polyglucosan storage.