Thrombospondin expression in myofibers stabilizes muscle membranes

Abstract

Skeletal muscle is highly sensitive to mutations in genes that participate in membrane stability and cellular attachment, which often leads to muscular dystrophy. Here we show that Thrombospondin-4 (Thbs4) regulates skeletal muscle integrity and its susceptibility to muscular dystrophy through organization of membrane attachment complexes. Loss of the Thbs4 gene causes spontaneous dystrophic changes with aging and accelerates disease in 2 mouse models of muscular dystrophy, while overexpression of mouse Thbs4 is protective and mitigates dystrophic disease. In the myofiber, Thbs4 selectively enhances vesicular trafficking of dystrophin-glycoprotein and integrin attachment complexes to stabilize the sarcolemma. In agreement, muscle-specific overexpression of Drosophila Tsp or mouse Thbs4 rescues a Drosophila model of muscular dystrophy with augmented membrane residence of βPS integrin. This functional conservation emphasizes the fundamental importance of Thbs’ as regulators of cellular attachment and membrane stability and identifies Thbs4 as a potential therapeutic target for muscular dystrophy.DOI: http://dx.doi.org/10.7554/eLife.17589.001

Myocyte-derived Myomaker expression is required for regenerative fusion but exacerbates membrane instability in dystrophic myofibers

“…Forced downhill treadmill exercise and EBD uptake. To assess the sarcolemmal stability of mice in response to exercise-induced damage, we performed a downhill treadmill exercise protocol with EBD injection as previously described (32,33). Briefly, mice were run on a 6-lane treadmill set to a 15-degree downhill angle on 4 consecutive days to induce hind limb muscle damage.…”

“…Additionally, a significant reduction in fibrosis was also observed in mdx Mymk fiberKO mice ( Figure 5C), further indicating less overall muscle damage. We next performed a validated damage-inducing downhill treadmill protocol on mdx and mdx Mymk fiberKO mice (32,33), with injection of Evans blue dye (EBD), a vital dye that is used as a marker of sarcolemmal instability by its ability to penetrate compromised myofiber membranes. This experiment served as an independent assay for membrane integrity and assessed the protective effect of mdx Mymk fiberKO mice under an acute damage stimulus.…”

The mitochondrial calcium uniporter underlies metabolic fuel preference in skeletal muscle

“…Then, 5-μm tissue sections were prepared and stained with H&E. The myofiber cross-sectional area was measured using NIH Image J software. For transmission electron microscopy, quadriceps muscle was harvested, fixed in 3.5% glutaraldehyde and 0.15% sucrose in 0.1 M sodium cacodylate, pH 7.4, postfixed in 1% OsO 4, dehydrated, and embedded in epoxy resin, as previously described (23). Imaging was performed using a Hitachi 7600 electron microscope.…”

Effects of thrombospondin-4 on pro-inflammatory phenotype differentiation and apoptosis in macrophages

“…High levels of TSP-4 have been detected in remodeling and failing hearts [3][4][5][6][7] , several cancers [8][9][10][11][12][13] , and atherosclerotic lesions 14 . Recently, new functions have been ascribed to TSP-4 in the cardiovascular system [5][6][7][14][15][16][17][18][19][20][21][22][23][24][25] , cancer [8][9][10][11][12][24][25][26][27][28][29] , skeletal muscle 30,31 , and nervous system [32][33][34][35][36] , but effects of TSP-4 on cellular responses and the regulation of TSP-4 expression remain poorly understood. For example, with an exception of TGFbeta 25 , stimuli inducing TSP-4 expression in tissues remain unknown.…”