1
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Ojima K, Kigaki M, Ichimura E, Suzuki T, Kobayashi K, Muroya S, Nishimura T. Endogenous slow and fast myosin dynamics in myofibers isolated from mice expressing GFP-Myh7 and Kusabira Orange-Myh1. Am J Physiol Cell Physiol 2022; 323:C520-C535. [PMID: 35759444 DOI: 10.1152/ajpcell.00415.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Skeletal muscle consists of slow and fast myofibers in which different myosin isoforms are expressed. Approximately 300 myosins form a single thick filament in the myofibrils, where myosin is continuously exchanged. However, endogenous slow and fast myosin dynamics have not been fully understood. To elucidate those dynamics, here we generated mice expressing green fluorescence protein-tagged slow myosin heavy chain (GFP-Myh7) and Kusabira Orange fluorescence protein-tagged fast myosin heavy chain (KuO-Myh1). First, these mice enabled us to distinguish between GFP- and KuO-myofibers under fluorescence microscopy: GFP-Myh7 and KuO-Myh1 were exclusively expressed in slow myofibers and fast myofibers, respectively. Next, to monitor endogenous myosin dynamics, fluorescence recovery after photobleaching (FRAP) was conducted. The mobile fraction (Mf) of GFP-Myh7 and that of KuO-Myh1 were almost constant values independent of the regions of the myofibers and the muscle portions where the myofibers were isolated. Intriguingly, proteasome inhibitor treatment significantly decreased the Mf in GFP-Myh7 but not in KuO-Myh1 myofibers, indicating that the response to a disturbance in protein turnover depended on muscle fiber type. Taken together, the present results indicated that the mice we generated are promising tools not only for distinguishing between GFP- and KuO-myofibers but also for studying the dynamics of endogenous myosin isoforms by live-cell fluorescence imaging.
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Affiliation(s)
- Koichi Ojima
- Muscle Biology Research Unit, Division of Animal Products Research, Institute of Livestock and Grassland Science, NARO, Tsukuba, Ibaraki, Japan
| | - Masahiro Kigaki
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Emi Ichimura
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Takahiro Suzuki
- Laboratory of Muscle and Meat Science, Department of Animal and Marine Bioresource Sciences, Faculty of Agriculture, Graduate School of Agriculture, Kyushu University, Fukuoka, Japan
| | - Ken Kobayashi
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Susumu Muroya
- Muscle Biology Research Unit, Division of Animal Products Research, Institute of Livestock and Grassland Science, NARO, Tsukuba, Ibaraki, Japan
| | - Takanori Nishimura
- Research Faculty of Agriculture, Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
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2
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Luo Y, Tian L, Lian C, Xu Y. KLHL38 facilitates STS-induced apoptosis in HL-1 cells via myocardin degradation. IUBMB Life 2022; 74:446-462. [PMID: 35112472 DOI: 10.1002/iub.2602] [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: 11/02/2021] [Revised: 12/14/2021] [Accepted: 01/28/2022] [Indexed: 11/06/2022]
Abstract
Cardiac apoptosis has been identified as one of the main precipitating factors of heart failure (HF) throughout the whole course of progressive disease. Limited to the lack of diagnostic markers and effective drug targets, cardiac apoptosis is still a major clinical challenge. Here, we reveal a potential novel therapeutic target for cardiac apoptosis. In the cause of the study, we found that KLHL38 was highly expressed in cardiac tissue of heart failure patients via GEO data-mining, which was further verified in the heart tissue of TAC mice. Meanwhile, the expression of KLHL38 is negatively correlated with myocardin protein level, which is a key cardiac apoptosis regulator. The KLHL38 overexpression obviously promoted cardiomyocyte apoptosis treated with staurosporine (STS) by facilitation of myocardin's ubiquitylation and subsequent proteasomal degradation. These findings reveal a new therapeutic target which may provide a new theoretical foundation for the treatment of myocardial apoptosis in clinical practice.
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Affiliation(s)
- Ying Luo
- College of Biological Science and Technology, Hubei Minzu University, Enshi, Hubei, China.,Hubei Provincial Key Laboratory of Occurrence and Intervention of Rheumatic diseases, Hubei Minzu University, Enshi, Hubei, China
| | - Lei Tian
- College of Biological Science and Technology, Hubei Minzu University, Enshi, Hubei, China
| | - Chen Lian
- College of Life Sciences and Health, Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Yao Xu
- College of Life Sciences and Health, Wuhan University of Science and Technology, Wuhan, Hubei, China
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3
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Sorensen DW, Carreon D, Williams JM, Pearce WJ. Hypoxic modulation of fetal vascular MLCK abundance, localization, and function. Am J Physiol Regul Integr Comp Physiol 2021; 320:R1-R18. [PMID: 33112654 PMCID: PMC7847055 DOI: 10.1152/ajpregu.00212.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/01/2020] [Accepted: 10/13/2020] [Indexed: 12/26/2022]
Abstract
Changes in vascular contractility are among the most important physiological effects of acute and chronic fetal hypoxia. Given the essential role of myosin light-chain kinase (MLCK) in smooth muscle contractility and its heterogeneous distribution, this study explores the hypothesis that subcellular changes in MLCK distribution contribute to hypoxic modulation of fetal carotid artery contractility. Relative to common carotid arteries from normoxic term fetal lambs (FN), carotids from fetal lambs gestated at high altitude (3,802 m) (FH) exhibited depressed contractility without changes in MLCK mRNA or protein abundance. Patterns of confocal colocalization of MLCK with α-actin and 20-kDa regulatory myosin light chain (MLC20) enabled calculation of subcellular MLCK fractions: 1) colocalized with the contractile apparatus, 2) colocalized with α-actin distant from the contractile apparatus, and 3) not colocalized with α-actin. Chronic hypoxia did not affect MLCK abundance in the contractile fraction, despite a concurrent decrease in contractility. Organ culture for 72 h under 1% O2 decreased total MLCK abundance in FN and FH carotid arteries, but decreased the contractile MLCK abundance only in FH carotid arteries. Correspondingly, culture under 1% O2 depressed contractility more in FH than FN carotid arteries. In addition, hypoxia appeared to attenuate ubiquitin-independent proteasomal degradation of MLCK, as reported for other proteins. In aggregate, these results demonstrate that the combination of chronic hypoxia followed by hypoxic culture can induce MLCK translocation among at least three subcellular fractions with possible influences on contractility, indicating that changes in MLCK distribution are a significant component of fetal vascular responses to hypoxia.
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Affiliation(s)
- Dane W Sorensen
- Divisions of Physiology and Pharmacology, School of Medicine, Loma Linda University, Loma Linda, California
| | - Desirelys Carreon
- Divisions of Physiology and Pharmacology, School of Medicine, Loma Linda University, Loma Linda, California
| | - James M Williams
- Divisions of Physiology and Pharmacology, School of Medicine, Loma Linda University, Loma Linda, California
| | - William J Pearce
- Divisions of Physiology and Pharmacology, School of Medicine, Loma Linda University, Loma Linda, California
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4
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Baarsma HA, Han B, Poppinga WJ, Driessen S, Elzinga CRS, Halayko AJ, Meurs H, Maarsingh H, Schmidt M. Disruption of AKAP-PKA Interaction Induces Hypercontractility With Concomitant Increase in Proliferation Markers in Human Airway Smooth Muscle. Front Cell Dev Biol 2020; 8:165. [PMID: 32328490 PMCID: PMC7160303 DOI: 10.3389/fcell.2020.00165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 02/28/2020] [Indexed: 01/11/2023] Open
Abstract
With the ability to switch between proliferative and contractile phenotype, airway smooth muscle (ASM) cells can contribute to the progression of airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), in which airway obstruction is associated with ASM hypertrophy and hypercontractility. A-kinase anchoring proteins (AKAPs) have emerged as important regulatory molecules in various tissues, including ASM cells. AKAPs can anchor the regulatory subunits of protein kinase A (PKA), and guide cellular localization via various targeting domains. Here we investigated whether disruption of the AKAP-PKA interaction, by the cell permeable peptide stearated (st)-Ht31, alters human ASM proliferation and contractility. Treatment of human ASM with st-Ht31 enhanced the expression of protein markers associated with cell proliferation in both cultured cells and intact tissue, although this was not accompanied by an increase in cell viability or cell-cycle progression, suggesting that disruption of AKAP-PKA interaction on its own is not sufficient to drive ASM cell proliferation. Strikingly, st-Ht31 enhanced contractile force generation in human ASM tissue with concomitant upregulation of the contractile protein α-sm-actin. This upregulation of α-sm-actin was independent of mRNA stability, transcription or translation, but was dependent on proteasome function, as the proteasome inhibitor MG-132 prevented the st-Ht31 effect. Collectively, the AKAP-PKA interaction appears to regulate markers of the multi-functional capabilities of ASM, and this alter the physiological function, such as contractility, suggesting potential to contribute to the pathophysiology of airway diseases.
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Affiliation(s)
- Hoeke A Baarsma
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands.,Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Bing Han
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands.,Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Wilfred J Poppinga
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands.,Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Saskia Driessen
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands
| | - Carolina R S Elzinga
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands
| | - Andrew J Halayko
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB, Canada
| | - Herman Meurs
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands.,Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Harm Maarsingh
- Department of Pharmaceutical Sciences, Lloyd L. Gregory School of Pharmacy, Palm Beach Atlantic University, West Palm Beach, FL, United States
| | - Martina Schmidt
- Department of Molecular Pharmacology, University of Groningen, Groningen, Netherlands.,Groningen Research Institute for Asthma and COPD, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
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6
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Xia XD, Zhou Z, Yu XH, Zheng XL, Tang CK. Myocardin: A novel player in atherosclerosis. Atherosclerosis 2017; 257:266-278. [DOI: 10.1016/j.atherosclerosis.2016.12.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 11/29/2016] [Accepted: 12/01/2016] [Indexed: 12/21/2022]
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7
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Singh P, Li D, Gui Y, Zheng XL. Atrogin-1 Increases Smooth Muscle Contractility Through Myocardin Degradation. J Cell Physiol 2016; 232:806-817. [PMID: 27403897 DOI: 10.1002/jcp.25485] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 07/11/2016] [Indexed: 01/25/2023]
Abstract
Atrogin-1, an E3 ligase present in skeletal, cardiac and smooth muscle, down-regulates myocardin protein during skeletal muscle differentiation. Myocardin, the master regulator of smooth muscle cell (SMC) differentiation, induces expression of smooth muscle marker genes through its association with serum response factor (SRF), which binds to the CArG box in the promoter. Myocardin undergoes ubiquitylation and proteasomal degradation. Evidence suggests that proteasomal degradation of myocardin is critical for myocardin to exert its transcriptional activity, but there is no report about the E3 ligase responsible for myocardin ubiquitylation and subsequent transactivation. Here, we showed that overexpression of atrogin-1 increased contractility of cultured SMCs and mouse aortic tissues in organ culture. Overexpression of dominant-negative myocardin attenuated the increase in SMC contractility induced by atrogin-1. Atrogin-1 overexpression increased expression of the SM contractile markers while downregulated expression of myocardin protein but not mRNA. Atrogin-1 also ubiquitylated myocardin for proteasomal degradation in vascular SMCs. Deletion studies showed that atrogin-1 directly interacted with myocardin through its amino acids 284-345. Immunostaining studies showed nuclear localization of atrogin-1, myocardin, and the Rpt6 subunit of the 26S proteasome. Atrogin-1 overexpression not only resulted in degradation of myocardin but also increased recruitment of RNA Polymerase II onto the promoters of myocardin target genes. In summary, our results have revealed the roles for atrogin-1 in the regulation of smooth muscle contractility through enhancement of myocardin ubiquitylation/degradation and its transcriptional activity. J. Cell. Physiol. 232: 806-817, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Pavneet Singh
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Dong Li
- Department of Physiology and Pharmacology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Yu Gui
- Department of Physiology and Pharmacology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Xi-Long Zheng
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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8
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Zhou YX, Shi Z, Singh P, Yin H, Yu YN, Li L, Walsh MP, Gui Y, Zheng XL. Potential Role of Glycogen Synthase Kinase-3β in Regulation of Myocardin Activity in Human Vascular Smooth Muscle Cells. J Cell Physiol 2016; 231:393-402. [PMID: 26129946 DOI: 10.1002/jcp.25084] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 06/26/2015] [Indexed: 01/13/2023]
Abstract
Glycogen synthase kinase (GSK)-3β, a serine/threonine kinase with an inhibitory role in glycogen synthesis in hepatocytes and skeletal muscle, is also expressed in cardiac and smooth muscles. Inhibition of GSK-3β results in cardiac hypertrophy through reducing phosphorylation and increasing transcriptional activity of myocardin, a transcriptional co-activator for serum response factor. Myocardin plays critical roles in differentiation of smooth muscle cells (SMCs). This study, therefore, aimed to examine whether and how inhibition of GSK-3β regulates myocardin activity in human vascular SMCs. Treatment of SMCs with the GSK-3β inhibitors AR-A014418 and TWS 119 significantly reduced endogenous myocardin activity, as indicated by lower expression of myocardin target genes (and gene products), CNN1 (calponin), TAGLN1 (SM22), and ACTA2 (SM α-actin). In human SMCs overexpressing myocardin through the T-REx system, treatment with either GSK-3β inhibitor also inhibited the expression of CNN1, TAGLN1, and ACTA2. These effects of GSK-3β inhibitors were mimicked by transfection with GSK-3β siRNA. Notably, both AR-A014418 and TWS 119 decreased the serine/threonine phosphorylation of myocardin. The chromatin immunoprecipitation assay showed that AR-A014418 treatment reduced myocardin occupancy of the promoter of the myocardin target gene ACTA2. Overexpression of a dominant-negative GSK-3β mutant in myocardin-overexpressing SMCs reduced the expression of calponin, SM22, and SM α-actin. As expected, overexpression of constitutively active or wild-type GSK-3β in SMCs without myocardin overexpression increased expression of these proteins. In summary, our results indicate that inhibition of GSK-3β reduces myocardin transcriptional activity, suggesting a role for GSK-3β in myocardin transcriptional activity and smooth muscle differentiation.
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Affiliation(s)
- Yi-Xia Zhou
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Zhan Shi
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Pavneet Singh
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Hao Yin
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Yan-Ni Yu
- Guiyang Medical University, Guizhou, China
| | - Long Li
- Guiyang Medical University, Guizhou, China
| | - Michael P Walsh
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Yu Gui
- Department of Physiology and Pharmacology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Xi-Long Zheng
- Department of Biochemistry and Molecular Biology, Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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9
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Singh P, Zheng XL. Dual regulation of myocardin expression by tumor necrosis factor-α in vascular smooth muscle cells. PLoS One 2014; 9:e112120. [PMID: 25384061 PMCID: PMC4226488 DOI: 10.1371/journal.pone.0112120] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 10/12/2014] [Indexed: 12/31/2022] Open
Abstract
De-differentiation of vascular smooth muscle cells (VSMCs) plays a critical role in the development of atherosclerosis, a chronic inflammatory disease involving various cytokines such as tumor necrosis factor-α (TNFα). Myocardin is a co-factor of serum response factor (SRF) and is considered to be the master regulator of VSMC differentiation. It binds to SRF and regulates the expression of contractile proteins in VSMCs. Myocardin is also known to inhibit VSMC proliferation by inhibiting the NF-κB pathway, whereas TNFα is known to activate the NF-κB pathway in VSMCs. NF-κB activation has also been shown to inhibit myocardin expression and smooth muscle contractile marker genes. However, it is not definitively known whether TNFα regulates the expression and activity of myocardin in VSMCs. The current study aimed to investigate the role of TNFα in regulating myocardin and VSMC function. Our studies showed that TNFα down-regulated myocardin expression and activity in cultured VSMCs by activating the NF-κB pathway, resulting in decreased VSMC contractility and increased VSMC proliferation. Surprisingly, we also found that TNFα prevented myocardin mRNA degradation, and resulted in a further significant increase in myocardin expression and activity in differentiated VSMCs. Both the NF-κB and p44/42 MAPK pathways were involved in TNFα regulation of myocardin, which further increased the contractility of VSMCs. These differential effects of TNFα on myocardin seemingly depended on whether VSMCs were in a differentiated or de-differentiated state. Taken together, our results demonstrate that TNFα differentially regulates myocardin expression and activity, which may play a key role in regulating VSMC functions.
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Affiliation(s)
- Pavneet Singh
- Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Xi-Long Zheng
- Smooth Muscle Research Group, Libin Cardiovascular Institute of Alberta, Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
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10
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Abstract
Arp5 suppresses myocardin activity through both direct binding to myocardin and binding to SRF to prevent transcriptional activation of myogenic genes by the myocardin–SRF complex. Myocardin (Myocd) and Myocd-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). RPEL motifs are monomeric globular actin (G-actin) binding elements that regulate MRTF localization and activity. However, the function of the RPEL motif in Myocd is largely unknown because of its low affinity for G-actin. Here, we demonstrated that the Myocd RPEL motif bound to actin-related protein 5 (Arp5) instead of conventional actin, resulting in a significant suppression of Myocd activity. In addition, Arp5 bound to a DNA binding domain of SRF via its C-terminal sequence and prevented the association of the Myocd–SRF complex with the promoter regions of smooth muscle genes. Well-differentiated smooth muscle cells mainly expressed a specific splicing variant of arp5; therefore, the protein level of Arp5 was markedly reduced by partial messenger RNA decay and translational suppression. In dedifferentiated smooth muscle cells, Arp5 knockdown restored the differentiated phenotype via Myocd activation. Thus, Arp5 is a key regulator of Myocd activity.
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Affiliation(s)
- Tsuyoshi Morita
- Department of Neuroscience, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
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11
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Zheng XL. Myocardin and smooth muscle differentiation. Arch Biochem Biophys 2014; 543:48-56. [DOI: 10.1016/j.abb.2013.12.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/15/2013] [Accepted: 12/18/2013] [Indexed: 01/08/2023]
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12
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Jiang Y, Singh P, Yin H, Zhou YX, Gui Y, Wang DZ, Zheng XL. Opposite roles of myocardin and atrogin-1 in L6 myoblast differentiation. J Cell Physiol 2013; 228:1989-95. [PMID: 23526547 DOI: 10.1002/jcp.24365] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 03/04/2013] [Indexed: 12/15/2022]
Abstract
L6 rat myoblasts undergo differentiation and myotube formation when cultured in medium containing a low-concentration of serum, but the underlying mechanism is not well understood. The role of atrogin-1, an E3 ligase with well-characterized roles in muscle atrophy, has not been defined in muscle differentiation. Myocardin is a coactivator of serum response factor (SRF), which together promotes smooth muscle differentiation. Myocardin is transiently expressed in skeletal muscle progenitor cells with inhibitory effects on the expression of myogenin and muscle differentiation. It remains unknown whether myocardin, which undergoes ubiquitination degradation, plays a role in L6 cell differentiation. The current study aimed to investigate the potential roles of myocardin and atrogin-1 in differentiation of L6 cells. As reported by many others, shifting to medium containing 2% serum induced myotube formation of L6 cells. Differentiation was accompanied by up-regulation of atrogin-1 and down-regulation of myocardin, suggesting that both may be involved in muscle differentiation. As expected, over-expression of atrogin-1 stimulated the expression of troponin T and myogenin and differentiation of the L6 myoblasts. Co-expression of myocardin with atrogin-1 inhibited atrogin-1-induced myogenin expression. Over-expression of atrogin-1 decreased myocardin protein level, albeit without affecting its mRNA level. Small-interfering RNA-mediated knockdown of atrogin-1 increased myocardin protein. Consistently, ectopic expression of myocardin inhibited myogenic differentiation. Unexpectedly, myocardin decreased the expression of atrogin-1 without involving Foxo1. Taken together, our results have demonstrated that atrogin-1 plays a positive role in skeletal muscle differentiation through down-regulation of myocardin.
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Affiliation(s)
- Yulan Jiang
- Department of Biochemistry & Molecular Biology, The University of Calgary, Calgary, Albeta, Canada
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Salabei JK, Cummins TD, Singh M, Jones SP, Bhatnagar A, Hill BG. PDGF-mediated autophagy regulates vascular smooth muscle cell phenotype and resistance to oxidative stress. Biochem J 2013; 451:375-88. [PMID: 23421427 PMCID: PMC4040966 DOI: 10.1042/bj20121344] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Vascular injury and chronic arterial diseases result in exposure of VSMCs (vascular smooth muscle cells) to increased concentrations of growth factors. The mechanisms by which growth factors trigger VSMC phenotype transitions remain unclear. Because cellular reprogramming initiated by growth factors requires not only the induction of genes involved in cell proliferation, but also the removal of contractile proteins, we hypothesized that autophagy is an essential modulator of VSMC phenotype. Treatment of VSMCs with PDGF (platelet-derived growth factor)-BB resulted in decreased expression of the contractile phenotype markers calponin and α-smooth muscle actin and up-regulation of the synthetic phenotype markers osteopontin and vimentin. Autophagy, as assessed by LC3 (microtubule-associated protein light chain 3 α; also known as MAP1LC3A)-II abundance, LC3 puncta formation and electron microscopy, was activated by PDGF exposure. Inhibition of autophagy with 3-methyladenine, spautin-1 or bafilomycin stabilized the contractile phenotype. In particular, spautin-1 stabilized α-smooth muscle cell actin and calponin in PDGF-treated cells and prevented actin filament disorganization, diminished production of extracellular matrix, and abrogated VSMC hyperproliferation and migration. Treatment of cells with PDGF prevented protein damage and cell death caused by exposure to the lipid peroxidation product 4-hydroxynonenal. The results of the present study demonstrate a distinct form of autophagy induced by PDGF that is essential for attaining the synthetic phenotype and for survival under the conditions of high oxidative stress found to occur in vascular lesions.
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MESH Headings
- Actins/genetics
- Actins/metabolism
- Adenine/analogs & derivatives
- Adenine/pharmacology
- Aldehydes/pharmacology
- Animals
- Aorta/cytology
- Aorta/drug effects
- Aorta/metabolism
- Autophagy/drug effects
- Autophagy/genetics
- Biomarkers/metabolism
- Calcium-Binding Proteins/genetics
- Calcium-Binding Proteins/metabolism
- Gene Expression Regulation/drug effects
- Macrolides/pharmacology
- Male
- Microfilament Proteins/genetics
- Microfilament Proteins/metabolism
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Osteopontin/genetics
- Osteopontin/metabolism
- Oxidative Stress
- Phenotype
- Platelet-Derived Growth Factor/pharmacology
- Primary Cell Culture
- Rats
- Rats, Sprague-Dawley
- Signal Transduction/drug effects
- Vimentin/genetics
- Vimentin/metabolism
- Calponins
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Affiliation(s)
- Joshua K. Salabei
- Diabetes and Obesity Center and Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY 40202
| | - Timothy D. Cummins
- Diabetes and Obesity Center and Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202
| | - Mahavir Singh
- Diabetes and Obesity Center and Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202
| | - Steven P. Jones
- Diabetes and Obesity Center and Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202
- Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, KY 40202
| | - Aruni Bhatnagar
- Diabetes and Obesity Center and Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY 40202
- Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, KY 40202
| | - Bradford G. Hill
- Diabetes and Obesity Center and Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY 40202
- Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, KY 40202
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Pfisterer L, Feldner A, Hecker M, Korff T. Hypertension impairs myocardin function: a novel mechanism facilitating arterial remodelling. Cardiovasc Res 2012; 96:120-9. [PMID: 22843699 DOI: 10.1093/cvr/cvs247] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
AIMS Hypertension evokes detrimental changes in the arterial vessel wall that facilitate stiffening and thus lead to a further rise in mean blood pressure, eventually causing heart failure. The underlying pathophysiological remodelling process is elicited by an increase in wall stress (WS) and is strictly dependent on the activation of vascular smooth muscle cells (SMC). However, it remains unclear as to why these cells fail to maintain their contractile and quiescent phenotype in a hypertensive environment. METHODS AND RESULTS In this context, we reveal that the knockdown of myocardin--a pivotal transcriptional determinant of the contractile SMC phenotype--is sufficient to induce SMC proliferation. In line with this observation, immunofluorescence analysis of the media of remodelling arteries from hypertensive mice demonstrated a significant decrease in the abundance of myocardin and an increase in SMC proliferation. Subsequent analyses of isolated perfused mouse arteries and human cultured SMCs exposed to cyclic stretch (i.e. mimicking one component of WS) suggested that this biomechanical force facilitates serine phosphorylation of myocardin. Furthermore, this biomechanical stimulus promotes rapid translocation of myocardin from the nucleus to the cytoplasm, inhibits its mRNA expression, and causes proteasomal degradation of the cytoplasmic protein. CONCLUSIONS Collectively, these findings suggest that hypertension negates the activity of myocardin in SMCs on multiple levels, hence eliminating a crucial determinant of SMC quiescence. This mechanism may control the initial switch from the contractile towards the synthetic SMC phenotype during hypertension and may offer an interesting novel approach to prevent cardiovascular disease.
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Affiliation(s)
- Larissa Pfisterer
- Institute of Physiology and Pathophysiology, Division of Cardiovascular Physiology, University of Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
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Li H, Li J, Li Y, Singh P, Cao L, Xu LJ, Li D, Wang Y, Xie Z, Gui Y, Zheng XL. Sonic hedgehog promotes autophagy of vascular smooth muscle cells. Am J Physiol Heart Circ Physiol 2012; 303:H1319-31. [PMID: 23023870 DOI: 10.1152/ajpheart.00160.2012] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sonic hedgehog (Shh) is a morphogen critically involved in development that is reexpressed in atherosclerotic lesions. It also stimulates proliferation of vascular smooth muscle cells (SMCs). Autophagy in vascular SMCs is known to promote SMC survival and increase plaque stability. The aim of this study was to investigate whether Shh induces autophagy of vascular SMCs. Our study showed that both Shh protein and microtubule-associated protein 1 light chain 3 (LC3)-II were increased in SMCs within neointimal lesions of mouse common carotid arteries. In cultured mouse aortic SMCs, recombinant mouse Shh stimulated LC3-II levels. Overexpression of wild-type mouse Shh through the tetracycline-regulated expression-inducible system in human aortic SMCs time-dependently increased the levels of LC3-II and also stimulated protein kinase B (AKT) phosphorylation. Pretreatment with AKT inhibitor IV (AKTI IV) inhibited AKT phosphorylation and the increase in LC3-II. Shh-induced autophagy was further confirmed by the formation of autophagosomes as detected by immunostaining and transmission electron microscopy, which was inhibited by AKTI IV. Shh further increased SMC LC3-II in the presence of bafilomycin A1, (2S,3S)-trans-epoxysuccinyl-L-leucylamido-3-methylbutane ethyl ester, and pepstatin A or siRNA for the autophagy-related gene 7 (ATG7). In addition, Shh induced SMC proliferation, which was inhibited not only by AKTI IV but also by cyclopamine, an inhibitor of Shh receptor. Inhibition of autophagy with 3-methyladenine (3-MA), bafilomycin A1, or ATG7 siRNA resulted in inhibition of cell proliferation. Treatment with 3-MA, AKTI IV, or cyclopamine inhibited neointima formation in mouse common carotid arteries. Taken together, our results have shown that Shh induces autophagy of vascular SMCs involving AKT activation, suggesting a role of autophagy in Shh-induced cellular responses.
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Affiliation(s)
- Haijie Li
- Department of Biochemistry and Molecular Biology, Nankai University School of Medicine, Tianjin, China
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Notarnicola C, Rouleau C, Le Guen L, Virsolvy A, Richard S, Faure S, De Santa Barbara P. The RNA-binding protein RBPMS2 regulates development of gastrointestinal smooth muscle. Gastroenterology 2012; 143:687-697.e9. [PMID: 22683258 DOI: 10.1053/j.gastro.2012.05.047] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 05/24/2012] [Accepted: 05/26/2012] [Indexed: 12/22/2022]
Abstract
BACKGROUND & AIMS Gastrointestinal development requires regulated differentiation of visceral smooth muscle cells (SMCs) and their contractile activities; alterations in these processes might lead to gastrointestinal neuromuscular disorders. Gastrointestinal SMC development and remodeling involves post-transcriptional modification of messenger RNA. We investigated the function of the RNA-binding protein for multiple splicing 2 (RBPMS2) during normal development of visceral smooth muscle in chicken and expression of its transcript in human pathophysiological conditions. METHODS We used avian replication-competent retroviral misexpression approaches to analyze the function of RBPMS2 in vivo and in primary cultures of chicken SMCs. We analyzed levels of RBPMS2 transcripts in colon samples from pediatric patients with Hirschsprung's disease and patients with chronic pseudo obstruction syndrome (CIPO) with megacystis. RESULTS RBPMS2 was expressed strongly during the early stage of visceral SMC development and quickly down-regulated in differentiated and mature SMCs. Misexpression of RBPMS2 in differentiated visceral SMCs induced their dedifferentiation and reduced their contractility by up-regulating expression of Noggin, which reduced activity of bone morphogenetic protein. Visceral smooth muscles from pediatric patients with CIPO expressed high levels of RBPMS2 transcripts, compared with smooth muscle from patients without this disorder. CONCLUSIONS Expression of RBPMS2 is present in visceral SMC precursors. Sustained expression of RBPMS2 inhibits the expression of markers of SMC differentiation by inhibiting bone morphogenetic protein activity, and stimulates SMC proliferation. RBPMS2 transcripts are up-regulated in patients with CIPO; alterations in RBPMS2 function might be involved in digestive motility disorders, particularly those characterized by the presence of muscular lesions (visceral myopathies).
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Affiliation(s)
- Cécile Notarnicola
- INSERM U1046, Université Montpellier 1, Université Montpellier 2, Montpellier, France
| | - Caroline Rouleau
- INSERM U1046, Université Montpellier 1, Université Montpellier 2, Montpellier, France; CHRU Montpellier, Service d'Anatomie Pathologique, Montpellier, France
| | - Ludovic Le Guen
- INSERM U1046, Université Montpellier 1, Université Montpellier 2, Montpellier, France
| | - Anne Virsolvy
- INSERM U1046, Université Montpellier 1, Université Montpellier 2, Montpellier, France
| | - Sylvain Richard
- INSERM U1046, Université Montpellier 1, Université Montpellier 2, Montpellier, France
| | - Sandrine Faure
- INSERM U1046, Université Montpellier 1, Université Montpellier 2, Montpellier, France
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Demasi M, Laurindo FRM. Physiological and pathological role of the ubiquitin-proteasome system in the vascular smooth muscle cell. Cardiovasc Res 2012; 95:183-93. [PMID: 22451513 DOI: 10.1093/cvr/cvs128] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Vascular smooth muscle cell (VSMC) plasticity implies a capacity for rapid change and adaptability through processes requiring protein turnover. The ubiquitin-proteasome system (UPS) is at the core of protein turnover as the main pathway for the degradation of proteins related to cell-cycle regulation, signalling, apoptosis, and differentiation. This review briefly addresses some structural UPS aspects under the perspective of VSMC (patho)biology. The UPS loss-of-function promotes direct cell effects and many indirect effects related to the adaptation to apoptosis/survival signalling, oxidative stress, and endoplasmic reticulum stress. The UPS regulates redox homeostasis and is redox-regulated. Also, the UPS closely interacts with endoplasmic reticulum (ER) homeostasis as the effector of un/misfolded protein degradation, and ER stress is strongly involved in atherosclerosis. Inhibition of cell cycle-controlling ubiquitin ligases or the proteasome reduces VSMC proliferation and prevents modulation of their synthetic phenotype. Proteasome inhibition also strongly promotes VSMC apoptosis and reduces neointima. In atherosclerosis models, proteasome inhibitors display vasculoprotective effects and reduce inflammation. However, worsening of atherosclerosis or vascular dysfunction has also been reported. Proteasome inhibitors sensitize VSMC to increased ER stress-mediated cell death and suppress unfolded protein response signalling. Taken together, these observations show that the UPS has powerful effects in the control of VSMC phenotype and survival signalling. However, more profound knowledge of mechanisms is needed in order to render the UPS an operational therapeutic target.
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Affiliation(s)
- Marilene Demasi
- Laboratory of Biochemistry and Biophysics, Butantan Institute, São Paulo, Brazil
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Abstract
Regulation of gene transcription is vitally important for the maintenance of normal cellular homeostasis. Failure to correctly regulate gene expression, or to deal with problems that arise during the transcription process, can lead to cellular catastrophe and disease. One of the ways cells cope with the challenges of transcription is by making extensive use of the proteolytic and nonproteolytic activities of the ubiquitin-proteasome system (UPS). Here, we review recent evidence showing deep mechanistic connections between the transcription and ubiquitin-proteasome systems. Our goal is to leave the reader with a sense that just about every step in transcription-from transcription initiation through to export of mRNA from the nucleus-is influenced by the UPS and that all major arms of the system--from the first step in ubiquitin (Ub) conjugation through to the proteasome-are recruited into transcriptional processes to provide regulation, directionality, and deconstructive power.
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Affiliation(s)
- Fuqiang Geng
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8240, USA.
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Kiyan Y, Limbourg A, Kiyan R, Tkachuk S, Limbourg FP, Ovsianikov A, Chichkov BN, Haller H, Dumler I. Urokinase receptor associates with myocardin to control vascular smooth muscle cells phenotype in vascular disease. Arterioscler Thromb Vasc Biol 2011; 32:110-22. [PMID: 22075245 DOI: 10.1161/atvbaha.111.234369] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE The urokinase-type plasminogen activator (uPA) and its specific receptor (uPAR) are a potent multifunctional system involved in vascular remodeling. The goal of the study was to unravel the mechanisms of uPA/uPAR-directed vascular smooth muscle cell (VSMC) differentiation. METHODS AND RESULTS Using cultured human primary VSMCs, we identified a new molecular mechanism controlling phenotypic modulation in vitro and in vivo. We found that the urokinase-type plasminogen activator receptor (uPAR) acts together with the transcriptional coactivator myocardin to regulate the VSMC phenotype. uPAR, a glycosylphosphatidylinositol-anchored cell-surface receptor family member, undergoes ligand-induced internalization and nuclear transport in VSMCs. Platelet-derived growth factor receptor β and SUMOylated RanGAP1 mediate this trafficking. Nuclear uPAR associates with myocardin, which is then recruited from the promoters of serum response factor target genes and undergoes proteasomal degradation. This chain of events initiates the synthetic VSMC phenotype. Using mouse carotid artery ligation model, we show that this mechanism contributes to adverse vascular remodeling after injury in vivo. We then cultured cells on a microstructured biomaterial and found that substrate topography induced uPAR-mediated VSMC differentiation. CONCLUSIONS These findings reveal the transcriptional activity of uPAR, controlling the differentiation of VSMCs in a vascular disease model. They also suggest a new role for uPAR as a therapeutic target and as a marker for VSMC phenotyping on prosthetic biomaterials.
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Affiliation(s)
- Yulia Kiyan
- Nephrology Department, Hannover Medical School, Carl-Neuberg Str 1, 30625 Hannover, Germany.
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