Muscle biology
Abstract
Glucocorticoid steroids are commonly prescribed for many inflammatory conditions, but chronic daily use produces adverse effects including muscle wasting and weakness. In contrast, shorter glucocorticoid pulses may improve athletic performance, although the mechanisms remain unclear. Muscle is sexually dimorphic and comparatively little is known about how male and female muscles respond to glucocorticoid steroids. We investigated the impact of once-weekly glucocorticoid exposure on skeletal muscle performance comparing male and female mice. One month of once-weekly glucocorticoid dosing improved muscle specific force in both males and females. Transcriptomic profiling of isolated myofibers identified a striking sexually dimorphic response to weekly glucocorticoids. Male myofibers had increased expression of genes in the IGF1/PI3K pathway and calcium handling, while female myofibers had profound upregulation of lipid metabolism genes. Muscles from weekly prednisone-treated males had improved calcium handling, while comparably treated female muscles had reduced intramuscular triglycerides. Consistent with altered lipid metabolism, weekly prednisone-treated female mice had greater endurance relative to controls. Using chromatin immunoprecipitation, we defined a sexually dimorphic chromatin landscape after weekly prednisone. These results demonstrate that weekly glucocorticoid exposure elicits distinct pathways in males versus females resulting in enhanced performance.
Authors
Isabella M. Salamone, Mattia Quattrocelli, David Y. Barefield, Patrick G. Page, Ibrahim Tahtah, Michele Hadhazy, Garima Tomar, Elizabeth M. McNally
Abstract
A sarcomere is the contractile unit of the myofibril in striated muscles such as cardiac and skeletal muscles. The assembly of sarcomeres depends on multiple molecules that serve as raw materials and participate in the assembly process. However, the mechanism of this critical assembly process remains largely unknown. Here, we found that the cell fate determinant Numb and its homolog Numblike regulated sarcomere assembly and maintenance in striated muscles. We discovered that Numb and Numblike are sarcomeric molecules that were gradually confined to the Z-disc during striated muscle development. Conditional knockout of Numb and Numblike severely compromised sarcomere assembly and its integrity and thus caused organelle dysfunction. Notably, we identified that Numb and Numblike served as sarcomeric α-Actin–binding proteins (ABPs) and shared a conserved domain that can bind to the barbed end of sarcomeric α-Actin. In vitro fluorometric α-Actin polymerization assay showed that Numb and Numblike also played a role in the sarcomeric α-Actin polymerization process. Last, we demonstrate that Numb and Numblike regulate sarcomeric α-Actinin–dependent (ACTN-dependent) Z-disc consolidation in the sarcomere assembly and maintenance. In summary, our studies show that Numb and its homolog Numblike regulate sarcomere assembly and maintenance in striated muscles, and demonstrate a molecular mechanism by which Numb/Numblike, sarcomeric α-Actin, and ACTN cooperate to control thin filament formation and Z-disc consolidation.
Authors
Baolei Wang, Min Yang, Shujuan Li
Abstract
Piezo1 forms mechanically-activated non-selective cation channels that contribute to endothelial response to fluid flow. Here we reveal an important role in the control of capillary density. Conditional endothelial-specific deletion of Piezo1 in adult mice depressed physical performance. Muscle microvascular endothelial cell apoptosis and capillary rarefaction were evident and sufficient to account for the effect on performance. There was selective upregulation of thrombospondin-2 (TSP2), an inducer of endothelial apoptosis, with no effect on thrombospondin-1 (TSP1), a related important player in muscle physiology. TSP2 was poorly expressed in muscle endothelial cells but robustly expressed in muscle pericytes, in which nitric oxide (NO) repressed the Tsp2 gene without effect on Tsp1. In the endothelial cells, Piezo1 was required for normal expression of endothelial nitric oxide synthase (eNOS). The data suggest an endothelial-pericyte partnership of muscle in which endothelial Piezo1 senses blood flow to sustain capillary density and thereby maintain physical capability.
Authors
Fiona Bartoli, Marjolaine Debant, Eulashini Chuntharpursat-Bon, Elizabeth L. Evans, Katie E. Musialowski, Gregory Parsonage, Lara C. Morley, T. Simon Futers, Piruthivi Sukumar, T. Scott Bowen, Mark T. Kearney, Laeticia Lichtenstein, Lee D. Roberts, David J. Beech
Abstract
Efficient sarcolemmal repair is required for muscle cell survival, with deficits in this process leading to muscle degeneration. Lack of the sarcolemmal protein dysferlin impairs sarcolemmal repair by reducing secretion of the enzyme acid sphingomyelinase (ASM), and causes limb girdle muscular dystrophy 2B (LGMD2B). The large size of the dysferlin gene poses a challenge for LGMD2B gene therapy efforts aimed at restoring dysferlin expression in skeletal muscle fibers. Here, we present an alternative gene therapy approach targeting reduced ASM secretion, the consequence of dysferlin deficit. We showed that the bulk endocytic ability is compromised in LGMD2B patient cells, which was addressed by extracellularly treating cells with ASM. Expression of secreted human ASM (hASM) using a liver-specific adeno-associated virus (AAV) vector restored membrane repair capacity of patient cells to healthy levels. A single in vivo dose of hASM-AAV in the LGMD2B mouse model restored myofiber repair capacity, enabling efficient recovery of myofibers from focal or lengthening contraction–induced injury. hASM-AAV treatment was safe, attenuated fibro-fatty muscle degeneration, increased myofiber size, and restored muscle strength, similar to dysferlin gene therapy. These findings elucidate the role of ASM in dysferlin-mediated plasma membrane repair and to our knowledge offer the first non–muscle-targeted gene therapy for LGMD2B.
Authors
Daniel C. Bittel, Sen Chandra Sreetama, Goutam Chandra, Robin Ziegler, Kanneboyina Nagaraju, Jack H. Van der Meulen, Jyoti K. Jaiswal
Abstract
Skeletal muscle can undergo a regenerative process from injury or disease to preserve muscle mass and function, which is critically influenced by cellular stress responses. Inositol-requiring enzyme 1 (IRE1) is an ancient endoplasmic reticulum (ER) stress sensor and mediates a key branch of the unfolded protein response (UPR). In mammals, IRE1α is implicated in the homeostatic control of stress responses during tissue injury and regeneration. Here, we show that IRE1α serves as a myogenic regulator in skeletal muscle regeneration in response to injury and muscular dystrophy. We found in mice that IRE1α was activated during injury-induced muscle regeneration, and muscle-specific IRE1α ablation resulted in impaired regeneration upon cardiotoxin-induced injury. Gain- and loss-of-function studies in myocytes demonstrated that IRE1αacts to sustain both differentiation in myoblasts and hypertrophy in myotubes through regulated IRE1-dependent decay (RIDD) of mRNA encoding Myostatin, a key negative regulator of muscle repair and growth. Furthermore, in the mouse model of Duchenne muscular dystrophy (DMD), loss of muscle IRE1α resulted in augmented Myostatin signaling and exacerbated the dystrophic phenotypes. Thus, these results reveal a pivotal role for the RIDD output of IRE1α in muscle regeneration, offering new insight into potential therapeutic strategies for muscle loss diseases.
Authors
Shengqi He, Tingting Fu, Yue Yu, Qinhao Liang, Luyao Li, Jing Liu, Xuan Zhang, Qian Zhou, Qiqi Guo, Dengqiu Xu, Yong Chen, Xiaolong Wang, Yulin Chen, Jianmiao Liu, Zhenji Gan, Yong Liu
Abstract
Skeletal muscle wasting is commonly associated with chronic kidney disease (CKD), resulting in increased morbidity and mortality. However, the link between kidney and muscle function remains poorly understood. Here, we took a complementary interorgan approach to investigate skeletal muscle wasting in CKD. We identified increased production and elevated blood levels of soluble pro-cachectic factors, including activin A, directly linking experimental and human CKD to skeletal muscle wasting programs. Single-cell sequencing data identified the expression of activin A in specific kidney cell populations of fibroblasts and cells of the juxtaglomerular apparatus. We propose that persistent and increased kidney production of pro-cachectic factors, combined with a lack of kidney clearance, facilitates a vicious kidney/muscle signaling cycle, leading to exacerbated blood accumulation and, thereby, skeletal muscle wasting. Systemic pharmacological blockade of activin A using soluble activin receptor type IIB ligand trap as well as muscle-specific adeno-associated virus–mediated downregulation of its receptor ACVR2A/B prevented muscle wasting in different mouse models of experimental CKD, suggesting that activin A is a key factor in CKD-induced cachexia. In summary, we uncovered a crosstalk between kidney and muscle and propose modulation of activin signaling as a potential therapeutic strategy for skeletal muscle wasting in CKD.
Authors
Francesca Solagna, Caterina Tezze, Maja T. Lindenmeyer, Shun Lu, Guochao Wu, Shuya Liu, Yu Zhao, Robert Mitchell, Charlotte Meyer, Saleh Omairi, Temel Kilic, Andrea Paolini, Olli Ritvos, Arja Pasternack, Antonios Matsakas, Dominik Kylies, Julian Schulze zur Wiesch, Jan-Eric Turner, Nicola Wanner, Viji Nair, Felix Eichinger, Rajasree Menon, Ina V. Martin, Barbara M. Klinkhammer, Elion Hoxha, Clemens D. Cohen, Pierre-Louis Tharaux, Peter Boor, Tammo Ostendorf, Matthias Kretzler, Marco Sandri, Oliver Kretz, Victor G. Puelles, Ketan Patel, Tobias B. Huber
Abstract
Severe asthma remains challenging to manage with limited treatment options. We have previously shown that targeting smooth muscle integrin α5β1 interaction with fibronectin can mitigate the effects of airway hyperresponsiveness by impairing force transmission. In this paper we show that another member of the integrin superfamily, integrin α2β1, is present in airway smooth muscle and capable of regulating force transmission via cellular tethering to the matrix protein collagen I, and to a lesser degree, laminin-111. The addition of an inhibitor of integrin α2β1 impaired IL-13-enhanced contraction in mouse tracheal rings and human bronchial rings, and abrogated the exaggerated bronchoconstriction induced by allergen sensitization and challenge. We confirmed that this effect was not due to alterations in classic intracellular myosin light chain phosphorylation regulating muscle shortening. Although IL-13 did not affect surface expression of α2β1, it did increase α2β1-mediated adhesion and the level of expression of an activation-specific epitope on the β1 subunit. We developed a method to simultaneously quantify airway narrowing and muscle shortening using two-photon microscopy and demonstrated that inhibition of α2β1 mitigated IL-13-enhanced airway narrowing without altering muscle shortening by impairing the tethering of muscle to the surrounding matrix. Our data identify cell-matrix tethering as an attractive therapeutic target to mitigate the severity of airway contraction in asthma.
Authors
Sean Liu, Uyen Ngo, Xin-Zi Tang, Xin Ren, Wenli Qiu, Xiaozhu Huang, William DeGrado, Christopher D.C. Allen, Hyunil Jo, Dean Sheppard, Aparna B. Sundaram
Abstract
Dysregulated protein degradative pathways are increasingly recognized as mediators of human disease. This mechanism may have particular relevance to desmosomal proteins that play critical structural roles in both tissue architecture and cell-cell communication as destabilization/breakdown of the desmosomal proteome is a hallmark of genetic-based desmosomal-targeted diseases, such as the cardiac disease, arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). However, no information exists on whether there are resident proteins that regulate desmosomal proteome homeostasis. Here we uncovered a cardiac COP9 desmosomal resident protein complex, composed of subunit 6 of the COP9 signalosome (CSN6), that enzymatically restricted neddylation and targeted desmosomal proteome degradation. CSN6 binding, localization, levels and function were impacted in hearts of classic mouse and human models of ARVD/C impacted by desmosomal loss and mutations, respectively. Loss of desmosomal proteome degradation control due to CSN6 loss and human desmosomal mutations destabilizing CSN6 were also sufficient to trigger ARVD/C in mice. We identified a desmosomal resident regulatory complex that restricted desmosomal proteome degradation and disease.
Authors
Yan Liang, Robert C. Lyon, Jason Pellman, William H. Bradford, Stephan Lange, Julius Bogomolovas, Nancy D. Dalton, Yusu Gu, Marcus Bobar, Mong-Hong Lee, Tomoo Iwakuma, Vishal Nigam, Angeliki Asimaki, Melvin Scheinman, Kirk L. Peterson, Farah Sheikh
Abstract
GDP-mannose-pyrophosphorylase-B (GMPPB) facilitates the generation of GDP-mannose, a sugar donor required for glycosylation. GMPPB defects cause muscle disease due to hypoglycosylation of α-dystroglycan (α-DG). Alpha-DG is part of a protein complex, which links the extracellular matrix with the cytoskeleton thus stabilizing myofibers. Mutations of the catalytically inactive homolog GMPPA cause AAMR syndrome, which is characterized by achalasia, alacrima, mental retardation, and muscle weakness. Here we show that Gmppa KO mice recapitulate cognitive and motor deficits. As structural correlates we found cortical layering defects, progressive neuron loss, and myopathic alterations. Increased GDP-mannose levels in skeletal muscle and in vitro assays identify GMPPA as an allosteric feedback inhibitor of GMPPB. Thus, its disruption enhances mannose incorporation into glycoproteins including α-Dg in mice and men. This increases α-Dg turnover and thereby lowers α-Dg abundance. In mice dietary mannose restriction beginning after weaning corrects α-DG hyperglycosylation and abundance, normalizes skeletal muscle morphology, and prevents neuron degeneration and the development of motor deficits. Cortical layering and cognitive performance, however, are not improved. We thus identify GMPPA defects as the first congenital disorder of glycosylation characterized by α-DG hyperglycosylation, unravel underlying disease mechanisms and point to potential dietary treatment options.
Authors
Patricia Franzka, Henriette Henze, M. Juliane Jung, Svenja C. Schüler, Sonnhild Mittag, Karina Biskup, Lutz Liebmann, Takfarinas Kentache, José Morales, Braulio Martínez, Istvan Katona, Tanja Herrmann, Antje-Kathrin Huebner, J. Christopher Hennings, Susann Groth, Lennart J. Gresing, Rüdiger Horstkorte, Thorsten Marquardt, Joachim Weis, Christoph Kaether, Osvaldo M. Mutchinick, Alessandro Ori, Otmar Huber, Véronique Blanchard, Julia von Maltzahn, Christian A. Hübner
Abstract
Troponin C (TnC) is a critical regulator of skeletal muscle contraction: it binds Ca2+ to activate muscle contraction. Surprisingly, the gene encoding fast skeletal TnC (TNNC2) has not yet been implicated in muscle disease. Here, we report two families with pathogenic variants in TNNC2. Patients present with a distinct, dominantly inherited congenital muscle disease. Molecular dynamics simulations suggest that the pathomechanisms by which the variants cause muscle disease include disruption of the binding sites for Ca2+ and for troponin I. In line with these findings, physiological studies in myofibers isolated from patients’ biopsies revealed a markedly reduced force response of the sarcomeres to [Ca2+]. This pathomechanism was further confirmed in experiments in which contractile dysfunction was evoked by replacing TnC in myofibers from healthy control subjects with recombinant, mutant TnC. Conversely, the contractile dysfunction of myofibers from patients was repaired by replacing endogenous, mutant TnC with recombinant, healthy TnC. Finally, we tested the therapeutic potential of the fast skeletal muscle troponin activator tirasemtiv in patients’ myofibers and showed that the contractile dysfunction was repaired. Thus, our data reveal that pathogenic variants in TNNC2 cause congenital muscle disease, and they provide therapeutic angles to repair muscle contractility.
Authors
Martijn van de Locht, Sandra Donkervoort, Josine M. de Winter, Stefan Conijn, Leon Begthel, Benno Kusters, Payam Mohassel, Ying Hu, Livija Medne, Colin Quinn, Steven A. Moore, A. Reghan Foley, Gwimoon Seo, Darren T. Hwee, Fady I. Malik, Thomas Irving, Weikang Ma, Henk Granzier, Erik-Jan Kamsteeg, Kalyan Immadisetty, Peter Kekenes-Huskey, Jose Renato Pinto, Nicol Voermans, Carsten G. Bönnemann, Coen A.C. Ottenheijm
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)