Chemical chaperone ameliorates pathological protein aggregation in plectin-deficient muscle
Lilli Winter, … , Rolf Schröder, Gerhard Wiche
Lilli Winter, … , Rolf Schröder, Gerhard Wiche
Published February 3, 2014
Citation Information: J Clin Invest. 2014;124(3):1144-1157. https://doi.org/10.1172/JCI71919.
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Research Article Muscle biology

Chemical chaperone ameliorates pathological protein aggregation in plectin-deficient muscle

Abstract

The ubiquitously expressed multifunctional cytolinker protein plectin is essential for muscle fiber integrity and myofiber cytoarchitecture. Patients suffering from plectinopathy-associated epidermolysis bullosa simplex with muscular dystrophy (EBS-MD) and mice lacking plectin in skeletal muscle display pathological desmin-positive protein aggregation and misalignment of Z-disks, which are hallmarks of myofibrillar myopathies (MFMs). Here, we developed immortalized murine myoblast cell lines to examine the pathogenesis of plectinopathies at the molecular and single cell level. Plectin-deficient myotubes, derived from myoblasts, were fully functional and mirrored the pathological features of EBS-MD myofibers, including the presence of desmin-positive protein aggregates and a concurrent disarrangement of the myofibrillar apparatus. Using this cell model, we demonstrated that plectin deficiency leads to increased intermediate filament network and sarcomere dynamics, marked upregulation of HSPs, and reduced myotube resilience following mechanical stretch. Currently, no specific therapy or treatment is available to improve plectin-related or other forms of MFMs; therefore, we assessed the therapeutic potential of chemical chaperones to relieve plectinopathies. Treatment with 4-phenylbutyrate resulted in remarkable amelioration of the pathological phenotypes in plectin-deficient myotubes as well as in plectin-deficient mice. Together, these data demonstrate the biological relevance of the MFM cell model and suggest that this model has potential use for the development of therapeutic approaches for EBS-MD.

Authors

Lilli Winter, Ilona Staszewska, Eva Mihailovska, Irmgard Fischer, Wolfgang H. Goldmann, Rolf Schröder, Gerhard Wiche

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Figure 7

Treatment of differentiated Plec+/+ and Plec–/– myotubes with the chemical chaperone 4-PBA.

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Treatment of differentiated Plec+/+ and Plec–/– myotubes with the chemic...
(A) 4-PBA–treated (1 mM) Plec+/+ and Plec–/– myotubes (differentiated for 10 days) were scored for cells with aggregated IFs. Mean ± SEM, 3 experiments (Plec+/+, n = 358; Plec–/–, n = 376). Note drastic reduction of affected myotubes in Plec–/– cells compared with untreated cells (dashed lines). (B) Dose response block diagram displaying the statistical evaluation of desmin protein aggregate formation in Plec–/– myotubes differentiated for 10 days in the presence of increasing concentrations of 4-PBA. (C) Z-disk formation in Plec+/+ and Plec–/– myotubes differentiated as in A. Mean ± SEM, 3 experiments (Plec+/+, n = 357; Plec–/–, n = 438). Note marked stabilization of sarcomeres in Plec–/– myotubes compared to untreated cells (dashed lines). (D) Dose response block diagram showing the statistical evaluation of Plec–/– cells with intact Z-disk formation after differentiation for 10 days in the presence of increasing concentrations of 4-PBA. Data in B and D represent mean ± SEM, 3 experiments. (E) Immunoblotting of cell lysates from 4-PBA–treated Plec+/+ and Plec–/– myotubes using antibodies to proteins indicated.