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Hong S, Lee HG, Huh WK. ARV1 deficiency induces lipid bilayer stress and enhances rDNA stability by activating the unfolded protein response in Saccharomyces cerevisiae. J Biol Chem 2024; 300:107273. [PMID: 38588806 PMCID: PMC11089378 DOI: 10.1016/j.jbc.2024.107273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 03/18/2024] [Accepted: 04/01/2024] [Indexed: 04/10/2024] Open
Abstract
The stability of ribosomal DNA (rDNA) is maintained through transcriptional silencing by the NAD+-dependent histone deacetylase Sir2 in Saccharomyces cerevisiae. Alongside proteostasis, rDNA stability is a crucial factor regulating the replicative lifespan of S. cerevisiae. The unfolded protein response (UPR) is induced by misfolding of proteins or an imbalance of membrane lipid composition and is responsible for degrading misfolded proteins and restoring endoplasmic reticulum (ER) membrane homeostasis. Recent investigations have suggested that the UPR can extend the replicative lifespan of yeast by enhancing protein quality control mechanisms, but the relationship between the UPR and rDNA stability remains unknown. In this study, we found that the deletion of ARV1, which encodes an ER protein of unknown molecular function, activates the UPR by inducing lipid bilayer stress. In arv1Δ cells, the UPR and the cell wall integrity pathway are activated independently of each other, and the high osmolarity glycerol (HOG) pathway is activated in a manner dependent on Ire1, which mediates the UPR. Activated Hog1 translocates the stress response transcription factor Msn2 to the nucleus, where it promotes the expression of nicotinamidase Pnc1, a well-known Sir2 activator. Following Sir2 activation, rDNA silencing and rDNA stability are promoted. Furthermore, the loss of other ER proteins, such as Pmt1 or Bst1, and ER stress induced by tunicamycin or inositol depletion also enhance rDNA stability in a Hog1-dependent manner. Collectively, these findings suggest that the induction of the UPR enhances rDNA stability in S. cerevisiae by promoting the Msn2-Pnc1-Sir2 pathway in a Hog1-dependent manner.
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Affiliation(s)
- Sujin Hong
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Hyeon-Geun Lee
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea
| | - Won-Ki Huh
- School of Biological Sciences, Seoul National University, Seoul, Republic of Korea; Institute of Microbiology, Seoul National University, Seoul, Republic of Korea.
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2
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Zhang QB, Liu AY, Fang QZ, Wang F, Wang H, Zhou Y. Effect of Electrical Stimulation on Disuse Muscular Atrophy Induced by Immobilization: Correlation With Upregulation of PERK Signal and Parkin-Mediated Mitophagy. Am J Phys Med Rehabil 2023; 102:692-700. [PMID: 36630294 DOI: 10.1097/phm.0000000000002182] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVES The aims of the study are to investigate the effect of electrical stimulation on disuse muscular atrophy induced by immobilization (IM) and to explore the role of PERK signal and Parkin-dependent mitophagy in this process. DESIGN In the first subexperiment, 24 rabbits were divided into four groups, which underwent different periods of IM. In the second subexperiment, 24 rabbits were divided into four groups on average in accordance with different kinds of interventions. To test the time-dependent changes of rectus femoris after IM, and to evaluate the effect of electrical stimulation, the wet weights, cross-sectional area and fat deposition of rectus femoris were assessed in this study, along with the protein levels of atrogin-1, p-PERK, Parkin, and COXIV. RESULTS The wet weights and cross-sectional area decreased, and the fat deposition increased in rectus femoris after IM, along with the elevated protein levels of atrogin-1, p-PERK, Parkin, and decreased protein levels of COXIV. The above histomorphological and molecular changes can be partially ameliorated by electrical stimulation. CONCLUSIONS Immobilization of unilateral lower limb could induce rectus femoris atrophy, which can be partially rectified by electrical stimulation. PERK signal and Parkin-mediated mitophagy may be the mechanisms by which electrical stimulation can play a significant role.
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Affiliation(s)
- Quan-Bing Zhang
- From the Department of Rehabilitation Medicine, The Second Affiliated Hospital of Anhui Medical University, Hefei, China (Q-BZ, FW, YZ); The Center for Scientific Research of the First Affiliated Hospital of Anhui Medical University, Hefei, China (A-YL); The Second Clinical Medicine College of Anhui Medical University, Hefei, China (Q-ZF); Key Laboratory of Environmental Toxicology of Anhui Higher Education Institutes, Hefei, China (HW); and Department of Toxicology, School of Public Health, Anhui Medical University, Hefei, China (HW)
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3
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Pagliara V, Amodio G, Vestuto V, Franceschelli S, Russo NA, Cirillo V, Mottola G, Remondelli P, Moltedo O. Myogenesis in C2C12 Cells Requires Phosphorylation of ATF6α by p38 MAPK. Biomedicines 2023; 11:biomedicines11051457. [PMID: 37239128 DOI: 10.3390/biomedicines11051457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 04/28/2023] [Accepted: 05/12/2023] [Indexed: 05/28/2023] Open
Abstract
Activating transcription factor 6α (ATF6α) is an endoplasmic reticulum protein known to participate in unfolded protein response (UPR) during ER stress in mammals. Herein, we show that in mouse C2C12 myoblasts induced to differentiate, ATF6α is the only pathway of the UPR activated. ATF6α stimulation is p38 MAPK-dependent, as revealed by the use of the inhibitor SB203580, which halts myotube formation and, at the same time, impairs trafficking of ATF6α, which accumulates at the cis-Golgi without being processed in the p50 transcriptional active form. To further evaluate the role of ATF6α, we knocked out the ATF6α gene, thus inhibiting the C2C12 myoblast from undergoing myogenesis, and this occurred independently from p38 MAPK activity. The expression of exogenous ATF6α in knocked-out ATF6α cells recover myogenesis, whereas the expression of an ATF6α mutant in the p38 MAPK phosphorylation site (T166) was not able to regain myogenesis. Genetic ablation of ATF6α also prevents the exit from the cell cycle, which is essential for muscle differentiation. Furthermore, when we inhibited differentiation by the use of dexamethasone in C2C12 cells, we found inactivation of p38 MAPK and, consequently, loss of ATF6α activity. All these findings suggest that the p-p38 MAPK/ATF6α axis, in pathophysiological conditions, regulates myogenesis by promoting the exit from the cell cycle, an essential step to start myoblasts differentiation.
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Affiliation(s)
- Valentina Pagliara
- Department of Medicine, Surgery and Dentistry "Scuola Medica Salernitana", University of Salerno, Via Salvador Allende, 84081 Baronissi, Italy
| | - Giuseppina Amodio
- Department of Medicine, Surgery and Dentistry "Scuola Medica Salernitana", University of Salerno, Via Salvador Allende, 84081 Baronissi, Italy
| | - Vincenzo Vestuto
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy
| | - Silvia Franceschelli
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy
| | - Nicola Antonino Russo
- Biogem, Istituto di Biologia e Genetica Molecolare, Via Camporeale, 83031 Ariano Irpino, Italy
| | - Vittorio Cirillo
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy
| | - Giovanna Mottola
- Centre de Recherche en Cardiovasculaire et Nutrition (C2VN) (AMU-INSERM 1263-INRAE 1260), Aix Marseille Université, Campus Timone, 27 Bd. Jean Moulin, 13005 Marseille, France
- Biogénopôle (BGP), Laboratoires de Biologie Médicale, Secteur Biochimie, Hôpital de La Timone, 264 Rue Saint-Pierre, 13005 Marseille, France
| | - Paolo Remondelli
- Department of Medicine, Surgery and Dentistry "Scuola Medica Salernitana", University of Salerno, Via Salvador Allende, 84081 Baronissi, Italy
| | - Ornella Moltedo
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 84084 Fisciano, Italy
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4
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Xiao J, Huang J, Jian X, Wang H, Lan H, Liao Z, Gu R, Hu J, Liao H. IRE1α arm of unfolded protein response in muscle-specific TGF-β signaling-mediated regulation of muscle cell immunological properties. Cell Mol Biol Lett 2023; 28:15. [PMID: 36849929 PMCID: PMC9972623 DOI: 10.1186/s11658-023-00429-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 02/06/2023] [Indexed: 03/01/2023] Open
Abstract
Endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are involved in various muscle pathological states. The IRE1α arm of UPR can affect immunological properties of myofiber through restraining p38 mitogen-activated protein kinases (MAPK) activation under inflammatory milieu. However, the relevant pathway molecules regulating the initiation of the IRE1α arm in myofiber remain unclear. In this work, expression of transforming growth factor-beta (TGF-β) and TGF-β receptor II (TGF-βr2), and UPR pathway activation were examined in cardiotoxin (CTX)-damaged mouse muscle, which revealed the activation of TGF-β signaling and UPR in CTX-damaged muscle and in regenerating myofibers. Using control or transgenic mice with TGF-βr2 deleted in skeletal muscle (SM TGF-βr2-/-) and the derived primary differentiating myogenic precursor cells (MPCs) treated with/without ERS activator or inhibitor, IRE1α pathway inhibitor, or TGF-β signaling activator, this study further revealed an essential role of intrinsic TGF-β signaling in regulating muscle cell to express inflammation-related molecules including H-2Kb, H2-Eα, TLR3, and special myokines. TGF-β signaling prompted UPR IRE1α arm and restrained p38 MAPK activation in myofiber under inflammatory milieu. This study uncovers a previously unrecognized function of TGF-β signaling acting as an upstream factor controlling myofiber immune capacities in the inflamed state through the UPR-IRE1α-p38 MAPK pathway.
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Affiliation(s)
- Jiangwei Xiao
- grid.284723.80000 0000 8877 7471Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515 China
| | - Jingwen Huang
- grid.284723.80000 0000 8877 7471Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515 China
| | - Xiaoting Jian
- grid.284723.80000 0000 8877 7471Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515 China
| | - Han Wang
- grid.284723.80000 0000 8877 7471Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515 China
| | - Haiqiang Lan
- grid.284723.80000 0000 8877 7471Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515 China
| | - Zhaohong Liao
- grid.284723.80000 0000 8877 7471Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515 China
| | - Ruicai Gu
- grid.266902.90000 0001 2179 3618Department of Cell Biology, University of Oklahoma Health Science Center, Oklahoma City, OK USA
| | - Jijie Hu
- Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, China.
| | - Hua Liao
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, 510515, China.
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5
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Chen L, Bi M, Zhang Z, Du X, Chen X, Jiao Q, Jiang H. The functions of IRE1α in neurodegenerative diseases: Beyond ER stress. Ageing Res Rev 2022; 82:101774. [PMID: 36332756 DOI: 10.1016/j.arr.2022.101774] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 10/19/2022] [Accepted: 10/29/2022] [Indexed: 11/05/2022]
Abstract
Inositol-requiring enzyme 1 α (IRE1α) is a type I transmembrane protein that resides in the endoplasmic reticulum (ER). IRE1α, which is the primary sensor of ER stress, has been proven to maintain intracellular protein homeostasis by activating X-box binding protein 1 (XBP1). Further studies have revealed novel physiological functions of the IRE1α, such as its roles in mRNA and protein degradation, inflammation, immunity, cell proliferation and cell death. Therefore, the function of IRE1α is not limited to its role in ER stress; IRE1α is also important for regulating other processes related to cellular physiology. Furthermore, IRE1α plays a key role in neurodegenerative diseases that are caused by the phosphorylation of Tau protein, the accumulation of α-synuclein (α-syn) and the toxic effects of mutant Huntingtin (mHtt). Therefore, targeting IRE1α is a valuable approach for treating neurodegenerative diseases and regulating cell functions. This review discusses the role of IRE1α in different cellular processes, and emphasizes the importance of IRE1α in neurodegenerative diseases.
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Affiliation(s)
- Ling Chen
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Mingxia Bi
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Zhen Zhang
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Xixun Du
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Xi Chen
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Qian Jiao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China.
| | - Hong Jiang
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China; University of Health and Rehabilitation Sciences, Qingdao, China.
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Xiao J, Li X, Zhou Z, Guan S, Zhuo L, Gao B. Development of an in vitro insulin resistance dissociated model of hepatic steatosis by co-culture system. Biosci Trends 2022; 16:257-266. [PMID: 35965099 DOI: 10.5582/bst.2022.01242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The evidence shows that there is an associated relationship between hepatosteatosis and insulin resistance. While some existing genetic induction animal and patient models challenge this relationship, indicating that hepatosteatosis is dissociated from insulin resistance. However, the molecular mechanisms of this dissociation remain poorly understood due to a lack of available, reliable, and simplistic setup models. Currently, we used primary rat hepatocytes (rHPCs), co-cultured with rat hepatic stellate cells (HSC-T6) or human foreskin fibroblast cells (HFF-1) in stimulation with high insulin and glucose, to develop a model of steatosis charactered as dissociated lipid accumulation from insulin resistance. Oil-Red staining significantly showed intracellular lipid accumulated in the developed model. Gene expression of sterol regulatory element-binding protein 1c (SREBP1c) and elongase of very-long-chain fatty acids 6 (ELOVL6), key genes responsible for lipogenesis, were detected and obviously increased in this model. Inversely, the insulin resistance related genes expression included phosphoenolpyruvate carboxykinase 1 (PCK1), pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4), and glucose-6-phosphatase (G6pase) were decreased, suggesting a dissociation relationship between steatosis and insulin resistance in the developed model. As well, the drug metabolism of this developed model was investigated and showed up-regulation of cytochrome P450 3A (CYP3A) and down-regulation of cytochrome P450 2E1 (CYP2E1) and cytochrome P450 1A2 (CYP1A2). Taken together, those results demonstrate that the in vitro model of dissociated steatosis from insulin resistance was successfully created by our co-cultured cells in high insulin and glucose medium, which will be a potential model for investigating the mechanism of insulin resistance dissociated steatosis, and discovering a novel drug for its treatment.
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Affiliation(s)
- Jiangwei Xiao
- Institute of Biological and Medical Engineering, Guangdong Academy of Sciences, Guangzhou, China.,National Engineering Research Center for Healthcare Devices, Guangzhou, China.,Guangdong Key Lab of Medical Electronic Instruments and Polymer Material Products, Guangzhou, China
| | - Xiang Li
- Department of Emergency Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Zongbao Zhou
- Institute of Biological and Medical Engineering, Guangdong Academy of Sciences, Guangzhou, China.,National Engineering Research Center for Healthcare Devices, Guangzhou, China.,Guangdong Key Lab of Medical Electronic Instruments and Polymer Material Products, Guangzhou, China
| | - Shuwen Guan
- Institute of Biological and Medical Engineering, Guangdong Academy of Sciences, Guangzhou, China.,National Engineering Research Center for Healthcare Devices, Guangzhou, China.,Guangdong Key Lab of Medical Electronic Instruments and Polymer Material Products, Guangzhou, China
| | - Lingjian Zhuo
- Department of Emergency Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Botao Gao
- Institute of Biological and Medical Engineering, Guangdong Academy of Sciences, Guangzhou, China.,National Engineering Research Center for Healthcare Devices, Guangzhou, China.,Guangdong Key Lab of Medical Electronic Instruments and Polymer Material Products, Guangzhou, China
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7
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Huang T, Huang J, Liao Z, Lan H, Jian X, Gu R, Ouyang J, Hu J, Liao H. Regenerating myofiber directs Tregs and Th17 responses in inflamed muscle through the intrinsic TGF-β signaling-mediated IL-6 production. Am J Physiol Endocrinol Metab 2022; 323:E92-E106. [PMID: 35532076 DOI: 10.1152/ajpendo.00247.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transforming growth factor-β (TGF-β) is considered to be an important immune regulatory cytokine. However, it remains unknown whether and how the muscle fiber specific-TGF-β signaling is directly involved in intramuscular inflammatory regulation by affecting T cells. Here, we addressed these in a mouse tibialis anterior muscle Cardiotoxin injection-induced injury repair model in muscle creatine kinase (MCK)-Cre control or transgenic mice with TGF-β receptor II (TGF-βr2) being specifically deleted in muscle cells (SM TGF-βr2-/-). In control mice, TGF-β2 and TGF-βr2 were found significantly upregulated in muscle after the acute injury. In mutant mice, deficiency of TGF-β signaling in muscle cells caused more serious muscle inflammation, with the increased infiltration of macrophages and CD4+ T cells at the degeneration stage (D4) and the early stage of regeneration (D7) after myoinjury. Notably, the loss of TGF-β signaling in myofibers dramatically affected CD4+ T cell function and delayed T cells withdrawal at the later stage of muscle regeneration (D10 and D15), marked by the elevated Th17, but the impaired Tregs response. Furthermore, in vivo and in vitro, the intrinsic TGF-β signaling affected immune behaviors of muscle cells and directed CD4+ T cells differentiation by impairing IL-6 production and release. It suggests that local muscle inflammation can be inhibited potentially by directly activating the TGF-β signaling pathway in muscle cells to suppress Th17, but induce Tregs responses. Thus, according to the results of this study, we found a new idea for the control of local acute inflammation in skeletal muscle.NEW & NOTEWORTHY Myofiber mediates muscle inflammatory response through activating the intrinsic TGF-β signaling. The specific TGF-β signaling activation contributes to myofiber IL-6 production and directs muscle-specific Th17 and Treg cell responses.
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Affiliation(s)
- Tao Huang
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
- Department of Anatomy, School of Basic Medical Science, Guizhou Medical University, Guizhou, China
| | - JingWen Huang
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
| | - ZhaoHong Liao
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
| | - HaiQiang Lan
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
| | - XiaoTing Jian
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
| | - RuiCai Gu
- Department of Cell Biology, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma
| | - Jun Ouyang
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
| | - Jijie Hu
- Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Hua Liao
- Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering; Department of Anatomy, School of Basic Medical Science, Southern Medical University, Guangzhou, China
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8
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Kny M, Fielitz J. Hidden Agenda - The Involvement of Endoplasmic Reticulum Stress and Unfolded Protein Response in Inflammation-Induced Muscle Wasting. Front Immunol 2022; 13:878755. [PMID: 35615361 PMCID: PMC9124858 DOI: 10.3389/fimmu.2022.878755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 04/04/2022] [Indexed: 11/13/2022] Open
Abstract
Critically ill patients at the intensive care unit (ICU) often develop a generalized weakness, called ICU-acquired weakness (ICUAW). A major contributor to ICUAW is muscle atrophy, a loss of skeletal muscle mass and function. Skeletal muscle assures almost all of the vital functions of our body. It adapts rapidly in response to physiological as well as pathological stress, such as inactivity, immobilization, and inflammation. In response to a reduced workload or inflammation muscle atrophy develops. Recent work suggests that adaptive or maladaptive processes in the endoplasmic reticulum (ER), also known as sarcoplasmic reticulum, contributes to this process. In muscle cells, the ER is a highly specialized cellular organelle that assures calcium homeostasis and therefore muscle contraction. The ER also assures correct folding of proteins that are secreted or localized to the cell membrane. Protein folding is a highly error prone process and accumulation of misfolded or unfolded proteins can cause ER stress, which is counteracted by the activation of a signaling network known as the unfolded protein response (UPR). Three ER membrane residing molecules, protein kinase R-like endoplasmic reticulum kinase (PERK), inositol requiring protein 1a (IRE1a), and activating transcription factor 6 (ATF6) initiate the UPR. The UPR aims to restore ER homeostasis by reducing overall protein synthesis and increasing gene expression of various ER chaperone proteins. If ER stress persists or cannot be resolved cell death pathways are activated. Although, ER stress-induced UPR pathways are known to be important for regulation of skeletal muscle mass and function as well as for inflammation and immune response its function in ICUAW is still elusive. Given recent advances in the development of ER stress modifying molecules for neurodegenerative diseases and cancer, it is important to know whether or not therapeutic interventions in ER stress pathways have favorable effects and these compounds can be used to prevent or treat ICUAW. In this review, we focus on the role of ER stress-induced UPR in skeletal muscle during critical illness and in response to predisposing risk factors such as immobilization, starvation and inflammation as well as ICUAW treatment to foster research for this devastating clinical problem.
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Affiliation(s)
- Melanie Kny
- Experimental and Clinical Research Center (ECRC), Charité-Universitätsmedizin Berlin, Max Delbrück Center (MDC) for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Jens Fielitz
- Department of Molecular Cardiology, DZHK (German Center for Cardiovascular Research), Partner Site, Greifswald, Germany
- Department of Internal Medicine B, Cardiology, University Medicine Greifswald, Greifswald, Germany
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