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Nangia-Makker P, Shekhar MP, Hogan V, Balan V, Raz A. MYH9 binds to dNTPs via deoxyribose moiety and plays an important role in DNA synthesis. Oncotarget 2022; 13:534-550. [PMID: 35309869 PMCID: PMC8923078 DOI: 10.18632/oncotarget.28219] [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: 01/25/2022] [Accepted: 03/04/2022] [Indexed: 11/25/2022] Open
Abstract
The accepted notion of dNTP transport following cytoplasmic biosynthesis is 'facilitated diffusion'; however, whether this alone is sufficient for moving dNTPs for DNA synthesis remains an open question. The data presented here show that the MYH9 gene encoded heavy chain of non-muscle myosin IIA binds dNTPs potentially serving as a 'reservoir'. Pull-down assays showed that MYH9 present in the cytoplasmic, mitochondrial and nuclear compartments bind to DNA and this interaction is inhibited by dNTPs and 2-deoxyribose-5-phosphate (dRP) suggesting that MYH9-DNA binding is mediated via pentose sugar recognition. Direct dNTP-MYH9 binding was demonstrated by ELISA and a novel PCR-based method, which showed that all dNTPs bind to MYH9 with varying efficiencies. Cellular thermal shift assays showed that MYH9 thermal stability is enhanced by dNTPs. MYH9 siRNA transfection or treatment with myosin II selective inhibitors ML7 or blebbistatin decreased cell proliferation compared to controls. EdU labeling and cell cycle analysis by flow cytometry confirmed MYH9 siRNA and myosin II inhibitors decreased progression to S-phase with accumulation of cells in G0/G1 phase. Taken together, our data suggest a novel role for MYH9 in dNTP binding and DNA synthesis.
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Affiliation(s)
- Pratima Nangia-Makker
- Barbara Ann Karmanos Cancer Institute, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Oncology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Malathy P.V. Shekhar
- Barbara Ann Karmanos Cancer Institute, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Oncology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Pathology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Victor Hogan
- Barbara Ann Karmanos Cancer Institute, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | | | - Avraham Raz
- Barbara Ann Karmanos Cancer Institute, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Oncology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
- Department of Pathology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
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Cook AW, Gough RE, Toseland CP. Nuclear myosins - roles for molecular transporters and anchors. J Cell Sci 2020; 133:133/11/jcs242420. [PMID: 32499319 DOI: 10.1242/jcs.242420] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The myosin family of molecular motors are well-characterised cytoskeletal proteins. However, myosins are also present in the nucleus, where they have been shown to have roles in transcription, DNA repair and viral infections. Despite their involvement in these fundamental cellular processes, our understanding of these functions and their regulation remains limited. Recently, research on nuclear myosins has been gathering pace, and this Review will evaluate the current state of the field. Here, we will focus on the variation in structure of nuclear myosins, their nuclear import and their roles within transcription, DNA damage, chromatin organisation and viral infections. We will also consider both the biochemical and biophysical properties and restraints that are placed on these multifunctional motors, and how they link to their cytoplasmic counterparts. By highlighting these properties and processes, we show just how integral nuclear myosins are for cellular survival.
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Affiliation(s)
- Alexander W Cook
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Rosemarie E Gough
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
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Venit T, Mahmood SR, Endara-Coll M, Percipalle P. Nuclear actin and myosin in chromatin regulation and maintenance of genome integrity. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 355:67-108. [DOI: 10.1016/bs.ircmb.2020.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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Milewska M, Domoradzki T, Majewska A, Błaszczyk M, Gajewska M, Hulanicka M, Grzelkowska-Kowalczyk K. Interleukin-6 affects pacsin3, ephrinA4 expression and cytoskeletal proteins in differentiating primary skeletal myoblasts through transcriptional and post-transcriptional mechanisms. Cell Tissue Res 2019; 380:155-172. [PMID: 31820147 DOI: 10.1007/s00441-019-03133-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 10/29/2019] [Indexed: 12/18/2022]
Abstract
Interleukin (IL)-6 is a proinflammatory cytokine released in injured and contracting skeletal muscles. In this study, we examined cellular expression of proteins associated with cytoskeleton organization and cell migration, chosen on the basis of microRNA profiling, in rat primary skeletal muscle cells (RSkMC) treated with IL-6 (1 ng/ml) for 11 days. MiRNA microarray analysis and qRT-PCR revealed increased expression of miR-154-3p and miR-338-3p in muscle cells treated with IL-6. Pacsin3 was downregulated post-transcriptionally by IL-6, but not by IGF-I. Ephrin4A protein was increased both in IL-6- and IGF-I-treated myocytes. IL-6, but not IGF-I, stimulated migratory ability of RSkMC, examined in wound healing assay. Alpha-actinin protein was slightly augmented in RSKMC treated with IL-6, similarly to IGF-I. IL-6, but not IGF-I, upregulated desmin in differentiating RSkMC. IL-6 supplementation caused accumulation of alpha-actinin and desmin in near-nuclear area of muscle cells, which was manifested by increased ratio: mean near-nuclear fluorescence/mean peripheral cytoplasm fluorescence of these proteins. We concluded that IL-6, a known proinflammatory cytokine and a physical activity-associated myokine, acting during differentiation of primary skeletal muscle cells, alters expression of nonmuscle-specific miRNAs. This cytokine causes differential effects on pacsin-3 and ephrinA4, through post-transcriptional inhibition and stimulation, respectively. IL-6-exerted modifications of cytoskeletal proteins in muscle cells include both transcriptional (desmin and dynein heavy chain 5) and post-transcriptional activation (alpha-actinin). Moreover, IL-6 augments near-nuclear distribution of cytoskeletal proteins, alpha-actinin and desmin and promotes migration of myocytes. Such effects suggest that IL-6 plays a role during skeletal muscle regeneration, acting through mechanisms independent of regulation of myogenic program.
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Affiliation(s)
- Marta Milewska
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Tomasz Domoradzki
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Alicja Majewska
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Maciej Błaszczyk
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Małgorzata Gajewska
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Magdalena Hulanicka
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Katarzyna Grzelkowska-Kowalczyk
- Institute of Veterinary Medicine, Department of Physiological Sciences, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776, Warsaw, Poland.
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Milewska M, Domoradzki T, Majewska A, Błaszczyk M, Gajewska M, Hulanicka M, Ciecierska A, Grzelkowska-Kowalczyk K. Interleukin-8 enhances myocilin expression, Akt-FoxO3 signaling and myogenic differentiation in rat skeletal muscle cells. J Cell Physiol 2019; 234:19675-19690. [PMID: 30945300 DOI: 10.1002/jcp.28568] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 03/04/2019] [Accepted: 03/06/2019] [Indexed: 01/01/2023]
Abstract
Interleukin (IL)-8 is released both in visceral adipose tissue and in contracting skeletal muscles. In this study, we examined cellular pathways associated with muscle hypertrophy, chosen on the basis of microRNA profiling, in differentiating rat primary skeletal muscle cells (RSkMC) treated with IL-8 (1 ng/ml) for 11 days. IL-8 increased myocilin expression, Akt phosphorylation, FoxO3 dispersion throughout the cytoplasm, and reduced FoxO3 level. IL-8 decreased the expression of atrogin and MuRF1 and increased myotube length and diameter. We concluded that IL-8 present in extracellular environment of myoblasts induced to differentiation stimulates expression of myocilin, a protein important for skeletal muscle hypertrophy. This phenomenon was associated with: (a) activation of myogenic transcription, (b) increased phosphorylation and activation of PKB/Akt, leading to (c) cytoplasm distribution and degradation of a transcription factor FoxO3, (d) decreased expression of gene markers of proteolysis, atrogin and Murf1, and (e) increased myotube length and diameter. In this regard, IL-8 affects skeletal muscle cells similarly to IGF-I and can be considered as a potent anticatabolic factor for skeletal muscle.
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Affiliation(s)
- Marta Milewska
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Tomasz Domoradzki
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Alicja Majewska
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Maciej Błaszczyk
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Małgorzata Gajewska
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Magdalena Hulanicka
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Anna Ciecierska
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
| | - Katarzyna Grzelkowska-Kowalczyk
- Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Warsaw, Poland
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Li YR, Yang WX. Myosins as fundamental components during tumorigenesis: diverse and indispensable. Oncotarget 2018; 7:46785-46812. [PMID: 27121062 PMCID: PMC5216836 DOI: 10.18632/oncotarget.8800] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 04/10/2016] [Indexed: 12/11/2022] Open
Abstract
Myosin is a kind of actin-based motor protein. As the crucial functions of myosin during tumorigenesis have become increasingly apparent, the profile of myosin in the field of cancer research has also been growing. Eighteen distinct classes of myosins have been discovered in the past twenty years and constitute a diverse superfamily. Various myosins share similar structures. They all convert energy from ATP hydrolysis to exert mechanical stress upon interactions with microfilaments. Ongoing research is increasingly suggesting that at least seven kinds of myosins participate in the formation and development of cancer. Myosins play essential roles in cytokinesis failure, chromosomal and centrosomal amplification, multipolar spindle formation and DNA microsatellite instability. These are all prerequisites of tumor formation. Subsequently, myosins activate various processes of tumor invasion and metastasis development including cell migration, adhesion, protrusion formation, loss of cell polarity and suppression of apoptosis. In this review, we summarize the current understanding of the roles of myosins during tumorigenesis and discuss the factors and mechanisms which may regulate myosins in tumor progression. Furthermore, we put forward a completely new concept of “chromomyosin” to demonstrate the pivotal functions of myosins during karyokinesis and how this acts to optimize the functions of the members of the myosin superfamily.
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Affiliation(s)
- Yan-Ruide Li
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Wan-Xi Yang
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou, China
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Zhang YS, Liu B, Luo XJ, Zhang JJ, Li NS, Ma QL, Jiang JL, Li YJ, Li Q, Peng J. A novel function of nuclear nonmuscle myosin regulatory light chain in promotion of xanthine oxidase transcription after myocardial ischemia/reperfusion. Free Radic Biol Med 2015; 83:115-28. [PMID: 25701432 DOI: 10.1016/j.freeradbiomed.2015.02.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Revised: 02/03/2015] [Accepted: 02/05/2015] [Indexed: 12/12/2022]
Abstract
Nuclear myosin regulates gene transcription and this novel function might be modulated through phosphorylation of the myosin regulatory light chain (p-MLC20). Nonmuscle MLC20 (nmMLC20) is also present in the nuclei of cardiomyocytes and a potential nmMLC20 binding sequence has been identified in the promoter of the xanthine oxidase (XO) gene. Thus, we investigated its function in the regulation of XO transcription after myocardial ischemia/reperfusion (IR). In a rat model of myocardial IR and a cardiomyocyte model of hypoxia/reoxygenation (HR) injury, the cardiac or cell injury, myosin light chain kinase (MLCK) content, XO expression and activity, XO-derived products, and level of nuclear p-nmMLC20 were detected. Coimmunoprecipitation (co-IP), chromatin immunoprecipitation, DNA pull-down, and luciferase reporter gene assays were used to decipher the molecular mechanisms through which nmMLC20 promotes XO expression. IR or HR treatment dramatically elevated nuclear p-nmMLC20 level, accompanied by increased XO expression, activity, and products (H2O2 and uric acid), as well as the IR or HR injury; these effects were ameliorated by inhibition of MLCK or knockdown of nmMLC20. Our findings from these experiments demonstrated that nuclear p-nmMLC20 binds to the consensus sequence GTCGCC in the XO gene promoter, interacts with RNA polymerase II and transcription factor IIB to form a transcription preinitiation complex, and hence activates XO gene transcription. These results suggest that nuclear p-nmMLC20 plays an important role in IR/HR injury by transcriptionally upregulating XO gene expression to increase oxidative stress in myocardium. Our findings demonstrate nuclear nmMLC20 as a potential new therapeutic target to combat cardiac IR injury.
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Affiliation(s)
- Yi-Shuai Zhang
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Bin Liu
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Xiu-Ju Luo
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Jie-Jie Zhang
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Nian-Sheng Li
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Qi-Lin Ma
- Department of Cardiovascular Medicine, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Jun-Lin Jiang
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Yuan-Jian Li
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China
| | - Qingjie Li
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, TX 77555-1083, USA.
| | - Jun Peng
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China; Hunan Provincial Key Laboratory of Cardiovascular Research, School of Pharmaceutical Sciences, Central South University, Changsha 410078, China.
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Zhang YS, Liu B, Luo XJ, Li TB, Zhang JJ, Peng JJ, Zhang XJ, Ma QL, Hu CP, Li YJ, Peng J, Li Q. Nuclear cardiac myosin light chain 2 modulates NADPH oxidase 2 expression in myocardium: a novel function beyond muscle contraction. Basic Res Cardiol 2015; 110:38. [PMID: 25982880 DOI: 10.1007/s00395-015-0494-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 05/02/2015] [Accepted: 05/08/2015] [Indexed: 12/21/2022]
Abstract
Recent studies demonstrated that NADPH oxidase 2 (NOX2) expression in myocardium after ischemia-reperfusion (IR) is significantly upregulated. However, the underlying mechanisms remain unknown. This study aims to determine if nuclear cardiac myosin light chain 2 (MYL2), a well-known regulatory subunit of myosin, functions as a transcription factor to promote NOX2 expression following myocardial IR in a phosphorylation-dependent manner. We examined the phosphorylation status of nuclear MYL2 (p-MYL2) in a rat model of myocardial IR (left main coronary artery subjected to 1 h ligation and 3 h reperfusion) injury, which showed IR injury and upregulated NOX2 expression as expected, accompanied by elevated H₂O₂ and nuclear p-MYL2 levels; these effects were attenuated by inhibition of myosin light chain kinase (MLCK). Next, we explored the functional relationship of nuclear p-MYL2 with NOX2 expression in H9c2 cell model of hypoxia-reoxygenation (HR) injury. In agreement with our in vivo findings, HR treatment increased apoptosis, NOX2 expression, nuclear p-MYL2 and H₂O₂ levels, and the increases were ameliorated by inhibition of MLCK or knockdown of MYL2. Finally, molecular biology techniques including co-immunoprecipitation (Co-IP), chromatin immunoprecipitation (ChIP), DNA pull-down and luciferase reporter gene assay were utilized to decipher the molecular mechanisms. We found that nuclear p-MYL2 binds to the consensus sequence AGCTCC in NOX2 gene promoter, interacts with RNA polymerase II and transcription factor IIB to form a transcription preinitiation complex, and thus activates NOX2 gene transcription. Our results demonstrate that nuclear MYL2 plays an important role in IR injury by transcriptionally upregulating NOX2 expression to enhance oxidative stress in a phosphorylation-dependent manner.
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Affiliation(s)
- Yi-Shuai Zhang
- Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha, 410078, China
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Betapudi V. Life without double-headed non-muscle myosin II motor proteins. Front Chem 2014; 2:45. [PMID: 25072053 PMCID: PMC4083560 DOI: 10.3389/fchem.2014.00045] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 06/19/2014] [Indexed: 11/20/2022] Open
Abstract
Non-muscle myosin II motor proteins (myosin IIA, myosin IIB, and myosin IIC) belong to a class of molecular motor proteins that are known to transduce cellular free-energy into biological work more efficiently than man-made combustion engines. Nature has given a single myosin II motor protein for lower eukaryotes and multiple for mammals but none for plants in order to provide impetus for their life. These specialized nanomachines drive cellular activities necessary for embryogenesis, organogenesis, and immunity. However, these multifunctional myosin II motor proteins are believed to go awry due to unknown reasons and contribute for the onset and progression of many autosomal-dominant disorders, cataract, deafness, infertility, cancer, kidney, neuronal, and inflammatory diseases. Many pathogens like HIV, Dengue, hepatitis C, and Lymphoma viruses as well as Salmonella and Mycobacteria are now known to take hostage of these dedicated myosin II motor proteins for their efficient pathogenesis. Even after four decades since their discovery, we still have a limited knowledge of how these motor proteins drive cell migration and cytokinesis. We need to enrich our current knowledge on these fundamental cellular processes and develop novel therapeutic strategies to fix mutated myosin II motor proteins in pathological conditions. This is the time to think how to relieve the hijacked myosins from pathogens in order to provide a renewed impetus for patients' life. Understanding how to steer these molecular motors in proliferating and differentiating stem cells will improve stem cell based-therapeutics development. Given the plethora of cellular activities non-muscle myosin motor proteins are involved in, their importance is apparent for human life.
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Affiliation(s)
- Venkaiah Betapudi
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Cleveland, OH, USA ; Department of Physiology and Biophysics, Case Western Reserve University Cleveland, OH, USA
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Affiliation(s)
- Primal de Lanerolle
- Department of Physiology and Biophysics, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, IL 60612, USA.
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Ihnatovych I, Migocka-Patrzalek M, Dukh M, Hofmann WA. Identification and characterization of a novel myosin Ic isoform that localizes to the nucleus. Cytoskeleton (Hoboken) 2012; 69:555-65. [PMID: 22736583 DOI: 10.1002/cm.21040] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 05/07/2012] [Accepted: 05/09/2012] [Indexed: 11/05/2022]
Abstract
In vertebrates, two myosin Ic isoforms that localize to the cytoplasm and to the nucleus have been characterized. The isoform that predominantly localizes to the nucleus is called nuclear myosin I (NMI). NMI has been identified as a key factor involved in nuclear processes such as transcription by RNA polymerases I and II and intranuclear transport processes. We report here the identification of a previously uncharacterized third MYOIC gene product that is called isoform A. Similar to NMI, this isoform contains a unique N-terminal peptide sequence, localizes to the nucleus and colocalizes with RNA polymerase II. However, unlike NMI, upon exposure to inhibitors of RNA polymerase II transcription the newly identified isoform translocates to nuclear speckles. Furthermore, in contrast to NMI, this new isoform is absent from nucleoli and does not colocalize with RNA polymerase I. Our results suggest an unexpected diversity among nuclear myosin Ic isoforms in respect to their intranuclear localization and interaction with nuclear binding partners that could provide new insights into the regulation of myosin-dependent nuclear processes.
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Affiliation(s)
- Ivanna Ihnatovych
- Department of Physiology and Biophysics, University at Buffalo-State University of New York, Buffalo, New York 14214, USA
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de Lanerolle P, Serebryannyy L. Nuclear actin and myosins: life without filaments. Nat Cell Biol 2011; 13:1282-8. [PMID: 22048410 DOI: 10.1038/ncb2364] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Actin and myosin are major components of the cell cytoskeleton, with structural and regulatory functions that affect many essential cellular processes. Although they were traditionally thought to function only in the cytoplasm, it is now well accepted that actin and multiple myosins are found in the nucleus. Increasing evidence on their functional roles has highlighted the importance of these proteins in the nuclear compartment.
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Affiliation(s)
- Primal de Lanerolle
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Li Q, Sarna SK. Nuclear myosin II regulates the assembly of preinitiation complex for ICAM-1 gene transcription. Gastroenterology 2009; 137:1051-60, 1060.e1-3. [PMID: 19328794 PMCID: PMC2736361 DOI: 10.1053/j.gastro.2009.03.040] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 03/11/2009] [Accepted: 03/10/2009] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Actin-myosin II motor converts chemical energy into force/motion in muscle and nonmuscle cells. The phosphorylation of 20-kilodalton regulatory myosin light chain (MLC(20)) is critical to the cytoplasmic functions of these motors. We do not know whether myosin II and actins in the nucleus function as motors to generate relative motion, such as that between RNA polymerase II holoenzyme and DNA, for assembly of the preinitiation complex. METHODS The experiments were performed on primary cultures of human colonic circular smooth muscle cells and rat colonic circular muscle strips. RESULTS We show that myosin II and alpha- and beta-actins are present in the nuclei of colonic smooth muscle cells. The nuclear myosin II is tethered to recognition sequence AGCTCC (-39/-34) in the intercellular adhesion molecule 1 (ICAM-1) core promoter region. The actins are known to complex with RNA polymerase II, and they are tethered to the nucleoskeleton. The dephosphorylation of MLC(20) increases the transcription of ICAM-1, whereas its phosphorylation decreases it. Colonic inflammation suppresses nuclear myosin light chain kinase, which increases the unphosphorylated form of nuclear MLC(20), resulting in enhanced transcription of ICAM-1. CONCLUSIONS Myosin II is a core transcription factor. The phosphorylation/dephosphorylation of nuclear MLC(20) results in the sliding of myosin and actin molecules past each other, producing relative motion between DNA bound to the myosin II and RNA polymerase II holoenzyme bound to actins and nucleoskeleton.
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Affiliation(s)
- Qingjie Li
- Department of Internal Medicine, The University of Texas Medical Branch at Galveston, Galveston, TX 77555-1064, USA
| | - Sushil K. Sarna
- Department of Internal Medicine, The University of Texas Medical Branch at Galveston, Galveston, TX 77555-1064, USA, Department of Neuroscience and Cell Biology, The University of Texas Medical Branch at Galveston, Galveston, TX 77555-1064, USA
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