The Proteomic Profile of Hereditary Inclusion Body Myopathy

Abstract

Hereditary inclusion body myopathy (HIBM) is an adult onset, slowly progressive distal and proximal myopathy. Although the causing gene, GNE, encodes for a key enzyme in the biosynthesis of sialic acid, its primary function in HIBM remains unknown. The goal of this study was to unravel new clues on the biological pathways leading to HIBM by proteomic comparison. Muscle cultures and biopsies were analyzed by two dimensional gel electrophoresis (2-DE) and the same biopsy extracts by isobaric tag for relative and absolute quantitation (iTRAQ). Proteins that were differentially expressed in all HIBM specimens versus all controls in each analysis were identified by mass spectrometry. The muscle cultures 2-DE analysis yielded 41 such proteins, while the biopsies 2-DE analysis showed 26 differentially expressed proteins. Out of the 400 proteins identified in biopsies by iTRAQ, 41 showed altered expression. In spite of the different nature of specimens (muscle primary cultures versus muscle biopsies) and of the different methods applied (2D gels versus iTRAQ) the differentially expressed proteins identified in each of the three analyses where related mainly to the same pathways, ubiquitination, stress response and mitochondrial processes, but the most robust cluster (30%) was assigned to cytoskeleton and sarcomere organization. Taken together, these findings indicate a possible novel function of GNE in the muscle filamentous apparatus that could be involved in the pathogenesis of HIBM.

Activation of the Ubiquitin Proteasome Pathway in a Mouse Model of Inflammatory Myopathy: A Potential Therapeutic Target

“…To understand the pathogenetic mechanisms involved in myositis, we performed an unbiased quantitative exploratory proteomic analysis of quadriceps muscle in a mouse model of myositis, using in vivo SILAC and MS. To date, the majority of studies exploring perturbed molecular mechanisms in myositic muscle have been conducted at the messenger RNA (mRNA) transcript level (). There have been a few proteomic studies of sporadic inclusion body myositis (IBM) and hereditary IBM in which the investigators used label‐free proteomic approaches (); however, precise quantification of protein modulations is technically challenging when label‐free proteomic approaches are used. Application of the SILAC strategy enabled precise quantification of alterations in protein such as H‐2Kb in diseased versus healthy muscle, and our initial proteomic profiling experiments demonstrated the effectiveness of this SILAC mouse strategy.…”

“…For example, investigators in one study conducted a proteomic analysis of IBM muscle using 2‐dimensional electrophoresis and reported 22 differentially modulated proteins (). In another study, analyses of hereditary IBM samples were conducted using 2‐dimensional electrophoresis in combination with iTRAQ, and 41 differentially modulated proteins were found (). These results suggest the superiority of in vivo labeling over other proteomic strategies without labeling.…”

“…In any case, it is important to understand the mechanism of action and mode of regulation of this protein in the pathology of myositis. Modulation of ubiquitination pathway proteins has been mentioned in relation to hereditary IBM (), but their pathogenic relevance has not been studied. Another study also demonstrated an increase in the transcripts of ubiquitin‐modifying enzymes (Ube1L, Ube2L6) in DM muscle (), suggesting a potential role of the UPP in the pathology of myositis.…”

UDP-GlcNAc 2-Epimerase/ManNAc Kinase (GNE): A Master Regulator of Sialic Acid Synthesis

“…GNE now became the focus of researchers who were no glycobiologists before. They contributed with novel findings and approaches, including the discovery of GNE splice variants [30] and, as a consequence, additional protein isoforms [31]; GNE-dependent genome [32] and proteome analysis [33]; the discovery of other GNE-opathies [34]; the establishment of a set of mouse models, and, importantly, the development of metabolic and genetic therapies for GNE-related diseases (see section 8).…”

Sustained expression and safety of human GNE in normal mice after gene transfer based on AAV8 systemic delivery

“…Dietary supply of sialic acid or its metabolic intermediate ManNAc could partially prevent the development of this pathology, indicating that sialic acid deficiency is part of the disease pathomechanism [10]. Recently, additional functions have been ascribed to GNE in muscle cells, such as its binding properties to alpha actinin, its localization in the Z disk [11] and its role in cytoskeleton organization [12], suggesting that other pathways may be affected in the pathophysiology of GNE myopathy. If indeed other mechanisms contribute to the development of GNE myopathy, metabolic supplementation may not correct them all.…”