Myotubularin controls desmin intermediate filament architecture and mitochondrial dynamics in human and mouse skeletal muscle
Karim Hnia, … , Jean Louis Mandel, Jocelyn Laporte
Karim Hnia, … , Jean Louis Mandel, Jocelyn Laporte
Published December 6, 2010
Citation Information: J Clin Invest. 2011;121(1):70-85. https://doi.org/10.1172/JCI44021.
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Research Article Muscle biology

Myotubularin controls desmin intermediate filament architecture and mitochondrial dynamics in human and mouse skeletal muscle

Abstract

Muscle contraction relies on a highly organized intracellular network of membrane organelles and cytoskeleton proteins. Among the latter are the intermediate filaments (IFs), a large family of proteins mutated in more than 30 human diseases. For example, mutations in the DES gene, which encodes the IF desmin, lead to desmin-related myopathy and cardiomyopathy. Here, we demonstrate that myotubularin (MTM1), which is mutated in individuals with X-linked centronuclear myopathy (XLCNM; also known as myotubular myopathy), is a desmin-binding protein and provide evidence for direct regulation of desmin by MTM1 in vitro and in vivo. XLCNM-causing mutations in MTM1 disrupted the MTM1-desmin complex, resulting in abnormal IF assembly and architecture in muscle cells and both mouse and human skeletal muscles. Adeno-associated virus–mediated ectopic expression of WT MTM1 in Mtm1-KO muscle reestablished normal desmin expression and localization. In addition, decreased MTM1 expression and XLCNM-causing mutations induced abnormal mitochondrial positioning, shape, dynamics, and function. We therefore conclude that MTM1 is a major regulator of both the desmin cytoskeleton and mitochondria homeostasis, specifically in skeletal muscle. Defects in IF stabilization and mitochondrial dynamics appear as common physiopathological features of centronuclear myopathies and desmin-related myopathies.

Authors

Karim Hnia, Helene Tronchère, Kinga K. Tomczak, Leonela Amoasii, Patrick Schultz, Alan H. Beggs, Bernard Payrastre, Jean Louis Mandel, Jocelyn Laporte

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Figure 1

MTM1 interacts with desmin in vitro and in muscle.

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MTM1 interacts with desmin in vitro and in muscle. (A) GST–MTM1–full-len...
(A) GST–MTM1–full-length (MTM1-FL), GST-MTM1-GRAM PH domain (GRAM), or GST recombinant proteins were incubated with mouse myotube or muscle homogenates. Endogenous desmin interacted with MTM1-FL, but not GST or GRAM. CB, Coomassie blue staining of purified recombinant GST fusions. (B) Far-Western blot using recombinant desmin protein overlaid with GST-MTM1-FL and revealed with anti-GST (left) or anti-desmin (right) antibodies. (C) Top: co-IP assays with lysates from COS-1 cells (cotransfected with MTM1 and desmin constructs), myotubes, and skeletal muscle using anti-MTM1–specific antibody or a frataxin antibody as a control (CTR). Antibodies used for IB are indicated. Bottom: co-IP of MTM1 with desmin in skeletal (Sk) muscle using the anti-desmin antibody. (D) Localization of MTM1 and desmin in WT and Mtm1-KO mouse skeletal muscles. Longitudinal and transversal sections showed colocalization of MTM1 and desmin at the z-disc structure and at the sarcolemma. Desmin localization was abnormal in Mtm1-KO muscle. Scale bar: 20 μm. (E) Desmin did not precipitate with MTM1 in extracts from cardiac muscle. Longitudinal sections of cardiac muscle were stained for MTM1 and desmin. Scale bars: 10 μm.