Dynamic distribution of muscle-specific calpain in mice has a key role in physical-stress adaptation and is impaired in muscular dystrophy
Koichi Ojima, … , Atsu Aiba, Hiroyuki Sorimachi
Koichi Ojima, … , Atsu Aiba, Hiroyuki Sorimachi
Published July 1, 2010
Citation Information: J Clin Invest. 2010;120(8):2672-2683. https://doi.org/10.1172/JCI40658.
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Research Article Muscle biology

Dynamic distribution of muscle-specific calpain in mice has a key role in physical-stress adaptation and is impaired in muscular dystrophy

Abstract

Limb-girdle muscular dystrophy type 2A (LGMD2A) is a genetic disease that is caused by mutations in the calpain 3 gene (CAPN3), which encodes the skeletal muscle–specific calpain, calpain 3 (also known as p94). However, the precise mechanism by which p94 functions in the pathogenesis of this disease remains unclear. Here, using p94 knockin mice (termed herein p94KI mice) in which endogenous p94 was replaced with a proteolytically inactive but structurally intact p94:C129S mutant protein, we have demonstrated that stretch-dependent p94 distribution in sarcomeres plays a crucial role in the pathogenesis of LGMD2A. The p94KI mice developed a progressive muscular dystrophy, which was exacerbated by exercise. The exercise-induced muscle degeneration in p94KI mice was associated with an inefficient redistribution of p94:C129S in stretched sarcomeres. Furthermore, the p94KI mice showed impaired adaptation to physical stress, which was accompanied by compromised upregulation of muscle ankyrin-repeat protein-2 and hsp upon exercise. These findings indicate that the stretch-induced dynamic redistribution of p94 is dependent on its protease activity and essential to protect muscle from degeneration, particularly under conditions of physical stress. Furthermore, our data provide direct evidence that loss of p94 protease activity can result in LGMD2A and molecular insight into how this could occur.

Authors

Koichi Ojima, Yukiko Kawabata, Harumi Nakao, Kazuki Nakao, Naoko Doi, Fujiko Kitamura, Yasuko Ono, Shoji Hata, Hidenori Suzuki, Hiroyuki Kawahara, Julius Bogomolovas, Christian Witt, Coen Ottenheijm, Siegfried Labeit, Henk Granzier, Noriko Toyama-Sorimachi, Michiko Sorimachi, Koichi Suzuki, Tatsuya Maeda, Keiko Abe, Atsu Aiba, Hiroyuki Sorimachi

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Figure 4

Changes in MARP2 in WT and p94KI mice before and after exercise.

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Changes in MARP2 in WT and p94KI mice before and after exercise. (A and ...
(A and B) MARP2 protein detected in WT, WT-ex, p94KI, and p94KI-ex mice. The total extract of TA muscles was subjected to Western blot analysis using an anti-MARP2 Ab (representative blots are shown; see Supplemental Figure 7 for all the blots). In WT-ex and p94KI-ex mice, the muscles were isolated immediately after exercise. Hairlines indicate lanes that were run on the same gel but were noncontiguous. The full-length MARP2 bands (40 kDa, black arrowheads) were quantified (B) by normalizing them to the CBB-stained band for myosin heavy chain (Mhc) (CBB in A). *P < 0.05 versus WT; **P < 0.05 versus p94KI. (C–N) Induction of MARP2 in WT mice after exercise. Muscle cross-sections from WT (C–E and I–K), and p94KI (F–H and L–N) mice were stained with anti–laminin α2 (C, F, I, and L) and anti-MARP2 (D, G, J, and M) Abs. The WT-ex and p94KI-ex muscle samples were isolated immediately after exercise (I–N). Nuclei were visualized with DAPI (light blue in C, E, F, H, I, K, L, and N). Note that MARP2-positive myonuclei were detected in the exercised WT (arrowheads) sample. For observations of longitudinal sections and the specificity of the anti-MARP2 Ab, see Supplemental Figure 8. Scale bars: 50 μm.