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Updated: May 29, 2025
Author Spotlight: Investigating Cellular and Molecular Dynamics During Muscle Regeneration Using Cutting-Edge Single-Cell Technologies
Published on: December 1, 2023
A window into intracellular events in myositis through subcellular proteomics
Jennifer M Peterson1, Valérie Leclair2, Olumide E Oyebode3
1Department of Exercise and Rehabilitative Sciences, The University of Toledo, 2801 W. Bancroft St., MS 119, Toledo, OH, 43606, USA. jennifer.peterson@utoledo.edu.
Objective And Design:
Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of inflammatory muscle disorders of unknown etiology. It is postulated that mitochondrial dysfunction and protein aggregation in skeletal muscle contribute to myofiber degeneration. However, molecular pathways that lead to protein aggregation in skeletal muscle are not well defined.
Subjects:
Here we have isolated membrane-bound organelles (e.g., nuclei, mitochondria, sarcoplasmic/endoplasmic reticulum, Golgi apparatus, and plasma membrane) from muscle biopsies of normal (n = 3) and muscle disease patients (n = 11). Of the myopathy group, 10 patients displayed mitochondrial abnormalities (IIM (n = 9); mitochondrial myopathy (n = 1)), and one IIM patient did not show mitochondrial abnormalities (polymyositis).
Methods:
Global proteomic analysis was performed using an Orbitrap Fusion mass spectrometer. Upon unsupervised clustering, normal and mitochondrial myopathy muscle samples clustered separately from IIM samples.
Results:
We have confirmed previously known protein alterations in IIM and identified several new ones. For example, we found differential expression of (i) nuclear proteins that control cell division, transcription, RNA regulation, and stability, (ii) ER and Golgi proteins involved in protein folding, degradation, and protein trafficking in the cytosol, and (iii) mitochondrial proteins involved in energy production/metabolism and alterations in cytoskeletal and contractile machinery of the muscle.
Conclusions:
Our data demonstrates that molecular alterations are not limited to protein aggregations in the cytosol (inclusions) and occur in nuclear, mitochondrial, and membrane compartments of IIM skeletal muscle.
Insights
Idiopathic inflammatory myopathies involve widespread molecular changes beyond protein aggregates, affecting nuclear, mitochondrial, and membrane proteins in skeletal muscle. This study reveals new protein alterations contributing to muscle degeneration in these conditions.
Area of Science:
- Muscle Biology
- Proteomics
- Molecular Medicine
Background:
- Idiopathic inflammatory myopathies (IIM) are complex muscle disorders with unknown causes.
- Mitochondrial dysfunction and protein aggregation are implicated in skeletal muscle degeneration in IIM.
- The precise molecular pathways driving protein aggregation in skeletal muscle remain unclear.
Purpose of the Study:
- To investigate molecular alterations in skeletal muscle of patients with idiopathic inflammatory myopathies (IIM).
- To identify novel protein changes in various cellular compartments of affected muscle tissue.
- To explore the role of mitochondrial dysfunction and protein aggregation in IIM pathogenesis.
Main Methods:
- Isolation of membrane-bound organelles (nuclei, mitochondria, ER, Golgi, plasma membrane) from muscle biopsies.
- Global proteomic analysis using Orbitrap Fusion mass spectrometry.
- Unsupervised clustering of proteomic data to differentiate between normal, mitochondrial myopathy, and IIM muscle samples.
Main Results:
- Confirmed known protein alterations and identified numerous new ones in IIM skeletal muscle.
- Found differential expression of nuclear proteins involved in cell division, transcription, and RNA regulation.
- Observed altered expression of ER/Golgi proteins related to protein folding and trafficking, and mitochondrial proteins in energy metabolism.
- Identified changes in the cytoskeletal and contractile machinery of muscle.
Conclusions:
- Molecular alterations in IIM skeletal muscle extend beyond cytosolic protein aggregates.
- Significant changes occur in nuclear, mitochondrial, and membrane-bound compartments.
- These findings provide a broader understanding of the molecular pathology in IIM.
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