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Hayashi K, Labios RJ, Morita T, Ashimori A, Aoki R, Mikuni M, Kimura K. Significance of the p38MAPK-CRP2 axis in myofibroblastic phenotypic transition. Cell Struct Funct 2023; 48:199-210. [PMID: 37899269 DOI: 10.1247/csf.23060] [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] [Indexed: 10/31/2023] Open
Abstract
We have recently demonstrated that a LIM domain protein, cysteine and glycine-rich protein 2 (CSRP2 [CRP2]), plays a vital role in the functional expression of myofibroblasts and cancer-associated fibroblasts. CRP2 binds directly to myocardin-related transcription factors (MRTF [MRTF-A or MRTF-B]) and serum response factor (SRF) to stabilize the MRTF/SRF/CArG-box complex, leading to the expression of smooth muscle cell (SMC) genes such as α-smooth muscle actin (α-SMA) and collagens. These are the marker genes for myofibroblasts. Here, we show that the adhesion of cultured human skin fibroblasts (HSFs) to collagen reduces the myofibroblastic features. HSF adhesion to collagen suppresses the expression of CRP2 and CSRP2-binding protein (CSRP2BP [CRP2BP]) and reduces the expression of SMC genes. Although CRP2BP is known as an epigenetic factor, we find that CRP2BP also acts as an adaptor protein to enhance the function of CRP2 mentioned above. This CRP2BP function does not depend on its histone acetyltransferase activity. We also addressed the molecular mechanism of the reduced myofibroblastic features of HSFs on collagen. HSF adhesion to collagen inhibits the p38MAPK-mediated pathway, and reducing the p38MAPK activity decreases the expression of CRP2 and SMC genes. Thus, the activation of p38MAPK is critical for the myofibroblastic features. We also show evidence that CRP2 plays a role in the myofibroblastic transition of retinal pigment epithelial cells (RPEs). Like HSFs, such phenotypic modulation of RPEs depends on the p38MAPK pathway.Key words: CRP2, p38MAPK, MRTF, myofibroblasts, retinal pigment epithelial cells.
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Affiliation(s)
- Ken'ichiro Hayashi
- Department of RNA Biology and Neuroscience, Osaka University Graduate School of Medicine
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine
| | - Reuben Jacob Labios
- Department of RNA Biology and Neuroscience, Osaka University Graduate School of Medicine
| | - Tsuyoshi Morita
- Department of Biology, Wakayama Medical University School of Medicine
| | - Atsushige Ashimori
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine
| | - Ren Aoki
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine
| | - Masanori Mikuni
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine
| | - Kazuhiro Kimura
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine
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2
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Hayashi K, Horoiwa S, Mori K, Miyata H, Labios RJ, Morita T, Kobayashi Y, Yamashiro C, Higashijima F, Yoshimoto T, Kimura K, Nakagawa Y. Role of CRP2-MRTF interaction in functions of myofibroblasts. Cell Struct Funct 2023; 48:83-98. [PMID: 37164693 PMCID: PMC10721955 DOI: 10.1247/csf.23004] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 03/18/2023] [Indexed: 05/12/2023] Open
Abstract
Inflammatory response induces phenotypic modulation of fibroblasts into myofibroblasts. Although transforming growth factor-βs (TGF-βs) evoke such transition, the details of the mechanism are still unknown. Here, we report that a LIM domain protein, cysteine-and glycine-rich protein 2 (CSRP2 [CRP2]) plays a vital role in the functional expression profile in myofibroblasts and cancer-associated fibroblasts (CAFs). Knock-down of CRP2 severely inhibits the expression of smooth muscle cell (SMC) genes, cell motility, and CAF-mediated collective invasion of epidermoid carcinoma. We elucidate the following molecular bases: CRP2 directly binds to myocardin-related transcription factors (MRTF-A/B [MRTFs]) and serum response factor (SRF) and stabilizes the MRTF/SRF/CArG-box complex to activate SMC gene expression. Furthermore, a three-dimensional structural analysis of CRP2 identifies the amino acids required for the CRP2-MRTF-A interaction. Polar amino acids in the C-terminal half (serine-152, glutamate-154, serine-155, threonine-156, threonine-157, and threonine-159 in human CRP2) are responsible for direct binding to MRTF-A. On the other hand, hydrophobic amino acids outside the consensus sequence of the LIM domain (tryptophan-139, phenylalanine-144, leucine-153, and leucine-158 in human CRP2) play a role in stabilizing the unique structure of the LIM domain.Key words: CRP2, 3D structure, myocardin-related transcription factor, myofibroblast, cancer-associated fibroblasts.
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Affiliation(s)
- Ken’ichiro Hayashi
- Department of RNA Biology and Neuroscience, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Minami-Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
| | - Shinri Horoiwa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kotaro Mori
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Hiroshi Miyata
- Department of Surgery, Osaka International Cancer Institute, 3-1-69 Otemae, Chuo-ku, Osaka 541-8567, Japan
| | - Reuben Jacob Labios
- Department of RNA Biology and Neuroscience, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tsuyoshi Morita
- Department of Biology, Wakayama Medical University School of Medicine, 580 Mikazura, Wakayama 641-0011, Japan
| | - Yuka Kobayashi
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Minami-Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
| | - Chiemi Yamashiro
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Minami-Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
| | - Fumiaki Higashijima
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Minami-Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
| | - Takuya Yoshimoto
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Minami-Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
| | - Kazuhiro Kimura
- Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Minami-Kogushi 1-1-1, Ube, Yamaguchi 755-8505, Japan
| | - Yoshiaki Nakagawa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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3
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Miranda MZ, Lichner Z, Szászi K, Kapus A. MRTF: Basic Biology and Role in Kidney Disease. Int J Mol Sci 2021; 22:ijms22116040. [PMID: 34204945 PMCID: PMC8199744 DOI: 10.3390/ijms22116040] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/21/2021] [Accepted: 05/30/2021] [Indexed: 12/23/2022] Open
Abstract
A lesser known but crucially important downstream effect of Rho family GTPases is the regulation of gene expression. This major role is mediated via the cytoskeleton, the organization of which dictates the nucleocytoplasmic shuttling of a set of transcription factors. Central among these is myocardin-related transcription factor (MRTF), which upon actin polymerization translocates to the nucleus and binds to its cognate partner, serum response factor (SRF). The MRTF/SRF complex then drives a large cohort of genes involved in cytoskeleton remodeling, contractility, extracellular matrix organization and many other processes. Accordingly, MRTF, activated by a variety of mechanical and chemical stimuli, affects a plethora of functions with physiological and pathological relevance. These include cell motility, development, metabolism and thus metastasis formation, inflammatory responses and—predominantly-organ fibrosis. The aim of this review is twofold: to provide an up-to-date summary about the basic biology and regulation of this versatile transcriptional coactivator; and to highlight its principal involvement in the pathobiology of kidney disease. Acting through both direct transcriptional and epigenetic mechanisms, MRTF plays a key (yet not fully appreciated) role in the induction of a profibrotic epithelial phenotype (PEP) as well as in fibroblast-myofibroblast transition, prime pathomechanisms in chronic kidney disease and renal fibrosis.
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Affiliation(s)
- Maria Zena Miranda
- Keenan Research Centre for Biomedical Science of the St. Michael’s Hospital, Toronto, ON M5B 1W8, Canada; (M.Z.M.); (Z.L.); (K.S.)
| | - Zsuzsanna Lichner
- Keenan Research Centre for Biomedical Science of the St. Michael’s Hospital, Toronto, ON M5B 1W8, Canada; (M.Z.M.); (Z.L.); (K.S.)
| | - Katalin Szászi
- Keenan Research Centre for Biomedical Science of the St. Michael’s Hospital, Toronto, ON M5B 1W8, Canada; (M.Z.M.); (Z.L.); (K.S.)
- Department of Surgery, University of Toronto, Toronto, ON M5T 1P5, Canada
| | - András Kapus
- Keenan Research Centre for Biomedical Science of the St. Michael’s Hospital, Toronto, ON M5B 1W8, Canada; (M.Z.M.); (Z.L.); (K.S.)
- Department of Surgery, University of Toronto, Toronto, ON M5T 1P5, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
- Correspondence:
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Fabrication of Adhesive Substrate for Incorporating Hydrogels to Investigate the Influence of Stiffness on Cancer Cell Behavior. Methods Mol Biol 2021; 2174:277-297. [PMID: 32813257 DOI: 10.1007/978-1-0716-0759-6_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Stiffness control of cell culture platforms provides researchers in cell biology with the ability to study different experimental models in conditions of mimicking physiological or pathological microenvironments. Nevertheless, the signal transduction pathways and drug sensibility of cancer cells have been poorly characterized widely using biomimetic platforms because the limited experience of cancer cell biology groups about handling substrates with specific mechanical properties. The protein cross-linking and stiffening control are crucial checkpoints that could strongly affect cell adhesion and spreading, misrepresenting the data acquired, and also generating inaccurate cellular models. Here, we introduce a simple method to adhere to polyacrylamide (PAA) hydrogels on glass coverslips without any special treatment for mechanics studies in cancer cell biology. By using a commercial photosensitive glue, Loctite 3525, it is possible to polymerize PAA hydrogels directly on glass surfaces. Furthermore, we describe a cross-linking reaction method to attach proteins to PAA as an alternative method to Sulfo-SANPAH cross-linking, which is sometimes difficult to implement and reproduce. In this chapter, we describe a reliable procedure to fabricate ECM protein-cross-linked PAA hydrogels for mechanotransduction studies on cancer cells.
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5
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Reed F, Larsuel ST, Mayday MY, Scanlon V, Krause DS. MRTFA: A critical protein in normal and malignant hematopoiesis and beyond. J Biol Chem 2021; 296:100543. [PMID: 33722605 PMCID: PMC8079280 DOI: 10.1016/j.jbc.2021.100543] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 03/11/2021] [Accepted: 03/12/2021] [Indexed: 12/03/2022] Open
Abstract
Myocardin-related transcription factor A (MRTFA) is a coactivator of serum response factor, a transcription factor that participates in several critical cellular functions including cell growth and apoptosis. MRTFA couples transcriptional regulation to actin cytoskeleton dynamics, and the transcriptional targets of the MRTFA–serum response factor complex include genes encoding cytoskeletal proteins as well as immediate early genes. Previous work has shown that MRTFA promotes the differentiation of many cell types, including various types of muscle cells and hematopoietic cells, and MRTFA's interactions with other protein partners broaden its cellular roles. However, despite being first identified as part of the recurrent t(1;22) chromosomal translocation in acute megakaryoblastic leukemia, the mechanisms by which MRTFA functions in malignant hematopoiesis have yet to be defined. In this review, we provide an in-depth examination of the structure, regulation, and known functions of MRTFA with a focus on hematopoiesis. We conclude by identifying areas of study that merit further investigation.
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Affiliation(s)
- Fiona Reed
- Department of Laboratory Medicine, Yale School of Medicine, New Haven, Connecticut, USA; Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, USA
| | - Shannon T Larsuel
- Department of Laboratory Medicine, Yale School of Medicine, New Haven, Connecticut, USA; Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, USA
| | - Madeline Y Mayday
- Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, USA; Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA
| | - Vanessa Scanlon
- Department of Laboratory Medicine, Yale School of Medicine, New Haven, Connecticut, USA; Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, USA
| | - Diane S Krause
- Department of Laboratory Medicine, Yale School of Medicine, New Haven, Connecticut, USA; Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, USA; Department of Pathology, Yale School of Medicine, New Haven, Connecticut, USA.
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6
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Hoffman LM, Smith MA, Jensen CC, Yoshigi M, Blankman E, Ullman KS, Beckerle MC. Mechanical stress triggers nuclear remodeling and the formation of transmembrane actin nuclear lines with associated nuclear pore complexes. Mol Biol Cell 2020; 31:1774-1787. [PMID: 31967947 PMCID: PMC7521858 DOI: 10.1091/mbc.e19-01-0027] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mechanical stimulation of fibroblasts induces changes in the actin cytoskeleton including stress fiber (SF) reinforcement and realignment. Here we characterize the nuclear response to mechanical stimulation (uniaxial cyclic stretch). Using fluorescence microscopy and quantitative image analysis we find that stretch-induced nuclear elongation and alignment perpendicular to the stretch vector are dependent on formin-regulated actin polymerization. The mechanosensitive transcription factors Yes-associated protein/Transcriptional coactivator with PDZ domain (YAP/TAZ) and myocardin-related transcription factor (MRTF-A, also known as MKL1 and MAL1) accumulate in the nucleus and activate their target genes in response to uniaxial cyclic stretch. We show that transmembrane actin nuclear (TAN) lines are induced by stretch stimulation and nuclear envelope (NE) proteins including nesprins, SUN2, and lamins form Linkers of the Nucleoskeleton and Cytoskeleton (LINC) complexes aligned with actin SFs. These NE structures are altered by pharmacological treatments (Cytochalasin D and Jasplakinolide) or genetic disruption (zyxin gene deletion) that alter actin, and their persistence requires maintenance of stretch stimulation. Nuclear pore complexes (NPCs) accumulate at TAN lines providing a potential mechanism for linking mechanical cues to NPC function.
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Affiliation(s)
- Laura M Hoffman
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112.,Department of Biology, University of Utah, Salt Lake City, UT 84112
| | - Mark A Smith
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112.,Department of Biology, University of Utah, Salt Lake City, UT 84112
| | | | - Masaaki Yoshigi
- Department of Pediatrics, University of Utah, Salt Lake City, UT 84112
| | | | - Katharine S Ullman
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112.,Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112
| | - Mary C Beckerle
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112.,Department of Biology, University of Utah, Salt Lake City, UT 84112.,Department of Oncological Sciences, University of Utah, Salt Lake City, UT 84112
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7
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Sidorenko E, Vartiainen MK. Nucleoskeletal regulation of transcription: Actin on MRTF. Exp Biol Med (Maywood) 2019; 244:1372-1381. [PMID: 31142145 DOI: 10.1177/1535370219854669] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Myocardin-related transcription factor A (MRTF-A) and serum response factor (SRF) form an essential transcriptional complex that regulates the expression of many cytoskeletal genes in response to dynamic changes in the actin cytoskeleton. The nucleoskeleton, a “dynamic network of networks,” consists of numerous proteins that contribute to nuclear shape and to its various functions, including gene expression. In this review, we will discuss recent work that has identified many nucleoskeletal proteins, such as nuclear lamina and lamina-associated proteins, nuclear actin, and the linker of the cytoskeleton and nucleoskeleton complex as important regulators of MRTF-A/SRF transcriptional activity, especially in the context of mechanical control of transcription. Impact statement Regulation of gene expression is a fundamental cellular process that ensures the appropriate response of a cell to its surroundings. Alongside biochemical signals, mechanical cues, such as substrate rigidity, have been recognized as key regulators of gene expression. Nucleoskeletal components play an important role in mechanoresponsive transcription, particularly in controlling the activity of MRTF-A/SRF transcription factors. This ensures that the cell can balance the internal and external mechanical forces by fine-tuning the expression of cytoskeletal genes.
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Affiliation(s)
- Ekaterina Sidorenko
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki 00014, Finland
| | - Maria K Vartiainen
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, Helsinki 00014, Finland
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8
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Gau D, Roy P. SRF'ing and SAP'ing - the role of MRTF proteins in cell migration. J Cell Sci 2018; 131:131/19/jcs218222. [PMID: 30309957 DOI: 10.1242/jcs.218222] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Actin-based cell migration is a fundamental cellular activity that plays a crucial role in a wide range of physiological and pathological processes. An essential feature of the remodeling of actin cytoskeleton during cell motility is the de novo synthesis of factors involved in the regulation of the actin cytoskeleton and cell adhesion in response to growth-factor signaling, and this aspect of cell migration is critically regulated by serum-response factor (SRF)-mediated gene transcription. Myocardin-related transcription factors (MRTFs) are key coactivators of SRF that link actin dynamics to SRF-mediated gene transcription. In this Review, we provide a comprehensive overview of the role of MRTF in both normal and cancer cell migration by discussing its canonical SRF-dependent as well as its recently emerged SRF-independent functions, exerted through its SAP domain, in the context of cell migration. We conclude by highlighting outstanding questions for future research in this field.
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Affiliation(s)
- David Gau
- Department of Bioengineering, University of Pittsburgh, PA 15213, USA
| | - Partha Roy
- Department of Bioengineering, University of Pittsburgh, PA 15213, USA .,Department of Pathology, University of Pittsburgh, PA, 15213, USA
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9
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Morita T, Hayashi K. Tumor Progression Is Mediated by Thymosin-β4 through a TGFβ/MRTF Signaling Axis. Mol Cancer Res 2018; 16:880-893. [DOI: 10.1158/1541-7786.mcr-17-0715] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 12/21/2017] [Accepted: 12/26/2017] [Indexed: 11/16/2022]
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10
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Finch-Edmondson M, Sudol M. Framework to function: mechanosensitive regulators of gene transcription. Cell Mol Biol Lett 2016; 21:28. [PMID: 28536630 PMCID: PMC5415767 DOI: 10.1186/s11658-016-0028-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 11/16/2016] [Indexed: 01/06/2023] Open
Abstract
Mechanobiology has shifted our understanding of fundamental cellular and physiological functions. Changes to the stiffness of the extracellular matrix, cell rigidity, or shape of the cell environment were considered in the past to be a consequence of aging or pathological processes. We now understand that these factors can actually be causative biological mediators of cell growth to control organ size. Mechanical cues are known to trigger a relatively fast translocation of specific transcriptional co-factors such as MRTFs, YAP and TAZ from the cytoplasm to the cell nucleus to initiate discrete transcriptional programs. The focus of this review is the molecular mechanisms by which biophysical stimuli that induce changes in cytoplasmic actin dynamics are communicated within cells to elicit gene-specific transcription via nuclear localisation or activation of specialized transcription factors, namely MRTFs and the Hippo pathway effectors YAP and TAZ. We propose here that MRTFs, YAP and TAZ closely collaborate as mechano-effectors.
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Affiliation(s)
- Megan Finch-Edmondson
- Mechanobiology Institute, National University of Singapore, 5A Engineering Drive 1, 117411 Singapore, Singapore.,Department of Physiology, National University of Singapore, Yong Loo Lin School of Medicine, 2 Medical Drive, 117597 Singapore, Singapore
| | - Marius Sudol
- Mechanobiology Institute, National University of Singapore, 5A Engineering Drive 1, 117411 Singapore, Singapore.,Department of Physiology, National University of Singapore, Yong Loo Lin School of Medicine, 2 Medical Drive, 117597 Singapore, Singapore
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11
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MRTF-A signaling regulates the acquisition of the contractile phenotype in dedifferentiated chondrocytes. Matrix Biol 2016; 62:3-14. [PMID: 27751947 DOI: 10.1016/j.matbio.2016.10.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 10/09/2016] [Accepted: 10/10/2016] [Indexed: 11/22/2022]
Abstract
Chondrocyte culture as a monolayer for cell number expansion results in dedifferentiation whereby expanded cells acquire contractile features and increased actin polymerization status. This study determined whether the actin polymerization based signaling pathway, myocardin-related transcription factor-a (MRTF-A) is involved in regulating this contractile phenotype. Serial passaging of chondrocytes in monolayer culture to passage 2 resulted in increased gene and protein expression of the contractile molecules alpha-smooth muscle actin, transgelin and vinculin compared to non-passaged, primary cells. This resulted in a functional change as passaged 2, but not primary, chondrocytes were capable of contracting type I collagen gels in a stress-relaxed contraction assay. These changes were associated with increased actin polymerization and MRTF-A nuclear localization. The involvement of actin was demonstrated by latrunculin B depolymerization of actin which reversed these changes. Alternatively cytochalasin D which activates MRTF-A increased gene and protein expression of α-smooth muscle actin, transgelin and vinculin, whereas CCG1423 which deactivates MRTF-A decreased these molecules. The involvement of MRTF-A signaling was confirmed by gene silencing of MRTF or its co-factor serum response factor. Knockdown experiments revealed downregulation of α-smooth muscle actin and transgelin gene and protein expression, and inhibition of gel contraction. These findings demonstrate that passaged chondrocytes acquire a contractile phenotype and that this change is modulated by the actin-MRTF-A-serum response factor signaling pathway.
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12
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Panayiotou R, Miralles F, Pawlowski R, Diring J, Flynn HR, Skehel M, Treisman R. Phosphorylation acts positively and negatively to regulate MRTF-A subcellular localisation and activity. eLife 2016; 5:e15460. [PMID: 27304076 PMCID: PMC4963197 DOI: 10.7554/elife.15460] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 06/14/2016] [Indexed: 11/29/2022] Open
Abstract
The myocardin-related transcription factors (MRTF-A and MRTF-B) regulate cytoskeletal genes through their partner transcription factor SRF. The MRTFs bind G-actin, and signal-regulated changes in cellular G-actin concentration control their nuclear accumulation. The MRTFs also undergo Rho- and ERK-dependent phosphorylation, but the function of MRTF phosphorylation, and the elements and signals involved in MRTF-A nuclear export are largely unexplored. We show that Rho-dependent MRTF-A phosphorylation reflects relief from an inhibitory function of nuclear actin. We map multiple sites of serum-induced phosphorylation, most of which are S/T-P motifs and show that S/T-P phosphorylation is required for transcriptional activation. ERK-mediated S98 phosphorylation inhibits assembly of G-actin complexes on the MRTF-A regulatory RPEL domain, promoting nuclear import. In contrast, S33 phosphorylation potentiates the activity of an autonomous Crm1-dependent N-terminal NES, which cooperates with five other NES elements to exclude MRTF-A from the nucleus. Phosphorylation thus plays positive and negative roles in the regulation of MRTF-A.
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Affiliation(s)
- Richard Panayiotou
- Signaling and Transcription Group, Francis Crick Institute, London, United Kingdom
| | - Francesc Miralles
- Signaling and Transcription Group, Francis Crick Institute, London, United Kingdom
| | - Rafal Pawlowski
- Signaling and Transcription Group, Francis Crick Institute, London, United Kingdom
| | - Jessica Diring
- Signaling and Transcription Group, Francis Crick Institute, London, United Kingdom
| | - Helen R Flynn
- Mass Spectrometry Science Technology Platform, Francis Crick Institute, London, United Kingdom
| | - Mark Skehel
- Mass Spectrometry Science Technology Platform, Francis Crick Institute, London, United Kingdom
| | - Richard Treisman
- Signaling and Transcription Group, Francis Crick Institute, London, United Kingdom
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13
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Speight P, Kofler M, Szászi K, Kapus A. Context-dependent switch in chemo/mechanotransduction via multilevel crosstalk among cytoskeleton-regulated MRTF and TAZ and TGFβ-regulated Smad3. Nat Commun 2016; 7:11642. [PMID: 27189435 PMCID: PMC4873981 DOI: 10.1038/ncomms11642] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 04/15/2016] [Indexed: 01/12/2023] Open
Abstract
Myocardin-related transcription factor (MRTF) and TAZ are major mechanosensitive transcriptional co-activators that link cytoskeleton organization to gene expression. Despite many similarities in their regulation, their physical and/or functional interactions are unknown. Here we show that MRTF and TAZ associate partly through a WW domain-dependent mechanism, and exhibit multilevel crosstalk affecting each other's expression, transport and transcriptional activity. Specifically, MRTF is essential for TAZ expression; TAZ and MRTF inhibit each other's cytosolic mobility and stimulus-induced nuclear accumulation; they antagonize each other's stimulatory effect on the α-smooth muscle actin (SMA) promoter, which harbours nearby cis-elements for both, but synergize on isolated TEAD-elements. Importantly, TAZ confers Smad3 sensitivity to the SMA promoter. Thus, TAZ is a context-dependent switch during mechanical versus mechano/chemical signalling, which inhibits stretch-induced but is indispensable for stretch+TGFβ-induced SMA expression. Crosstalk between these cytoskeleton-regulated factors seems critical for fine-tuning mechanical and mechanochemical transcriptional programmes underlying myofibroblast transition, wound healing and fibrogenesis.
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Affiliation(s)
- Pam Speight
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8
| | - Michael Kofler
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8
| | - Katalin Szászi
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8.,Department Surgery, University of Toronto, Toronto, Ontario, Canada M5P 1T5
| | - András Kapus
- Keenan Research Centre for Biomedical Science of St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada M5B 1T8.,Department Surgery, University of Toronto, Toronto, Ontario, Canada M5P 1T5.,Department Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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14
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Watanabe B, Minami S, Ishida H, Yoshioka R, Nakagawa Y, Morita T, Hayashi K. Stereospecific Inhibitory Effects of CCG-1423 on the Cellular Events Mediated by Myocardin-Related Transcription Factor A. PLoS One 2015; 10:e0136242. [PMID: 26295164 PMCID: PMC4546662 DOI: 10.1371/journal.pone.0136242] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 07/30/2015] [Indexed: 12/31/2022] Open
Abstract
CCG-1423 suppresses several pathological processes including cancer cell migration, tissue fibrosis, and the development of atherosclerotic lesions. These suppressions are caused by inhibition of myocardin-related transcription factor A (MRTF-A), which is a critical factor for epithelial–mesenchymal transition (EMT). CCG-1423 can therefore be a potent inhibitor for EMT. CCG-1423 and related compounds, CCG-100602 and CCG-203971 possess similar biological activities. Although these compounds are comprised of two stereoisomers, the differences in their biological activities remain to be assessed. To address this issue, we stereoselectively synthesized optically pure isomers of these compounds and validated their biological activities. The S-isomer of CCG-1423 rather than the R-isomer exhibited modestly but significantly higher inhibitory effects on the cellular events triggered by MRTF-A activation including serum response factor-mediated gene expression and cell migration of fibroblasts and B16F10 melanoma cells. Accordingly, the S-isomer of CCG-1423 more potently blocked the serum-induced nuclear import of MRTF-A than the R-isomer. No such difference was observed in cells treated with each of two stereoisomers of CCG-100602 or CCG-203971. We previously reported that the N-terminal basic domain (NB), which functions as a nuclear localization signal of MRTF-A, is a binding site for CCG-1423. Consistent with the biological activities of two stereoisomers of CCG-1423, docking simulation demonstrated that the S-isomer of CCG-1423 was more likely to bind to NB than the R-isomer. This is a first report demonstrating the stereospecific biological activities of CCG-1423.
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Affiliation(s)
- Bunta Watanabe
- Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Saki Minami
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan
| | - Hideaki Ishida
- Toabo Corporation Co., Ltd., Crystal Tower 18F, 2-27, 1-Chome, Shiromi, Chuo-ku, Osaka, 540-6018, Japan
| | - Ryuzo Yoshioka
- NAHLS Co., Ltd., Room 2203, Kyodai Katsura Venture Plaza South Building, 1-39 Goryo-Ohara, Nishikyo-ku, Kyoto, 615-8245, Japan
| | - Yoshiaki Nakagawa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan
| | - Tsuyoshi Morita
- Department of RNA Biology and Neuroscience, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Ken'ichiro Hayashi
- Department of RNA Biology and Neuroscience, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
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15
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Turczyńska KM, Swärd K, Hien TT, Wohlfahrt J, Mattisson IY, Ekman M, Nilsson J, Sjögren J, Murugesan V, Hultgårdh-Nilsson A, Cidad P, Hellstrand P, Pérez-García MT, Albinsson S. Regulation of Smooth Muscle Dystrophin and Synaptopodin 2 Expression by Actin Polymerization and Vascular Injury. Arterioscler Thromb Vasc Biol 2015; 35:1489-97. [DOI: 10.1161/atvbaha.114.305065] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 03/27/2015] [Indexed: 01/25/2023]
Abstract
Objective—
Actin dynamics in vascular smooth muscle is known to regulate contractile differentiation and may play a role in the pathogenesis of vascular disease. However, the list of genes regulated by actin polymerization in smooth muscle remains incomprehensive. Thus, the objective of this study was to identify actin-regulated genes in smooth muscle and to demonstrate the role of these genes in the regulation of vascular smooth muscle phenotype.
Approach and Results—
Mouse aortic smooth muscle cells were treated with an actin-stabilizing agent, jasplakinolide, and analyzed by microarrays. Several transcripts were upregulated including both known and previously unknown actin-regulated genes. Dystrophin and synaptopodin 2 were selected for further analysis in models of phenotypic modulation and vascular disease. These genes were highly expressed in differentiated versus synthetic smooth muscle and their expression was promoted by the transcription factors myocardin and myocardin-related transcription factor A. Furthermore, the expression of both synaptopodin 2 and dystrophin was significantly reduced in balloon-injured human arteries. Finally, using a dystrophin mutant
mdx
mouse and synaptopodin 2 knockdown, we demonstrate that these genes are involved in the regulation of smooth muscle differentiation and function.
Conclusions—
This study demonstrates novel genes that are promoted by actin polymerization, that regulate smooth muscle function, and that are deregulated in models of vascular disease. Thus, targeting actin polymerization or the genes controlled in this manner can lead to novel therapeutic options against vascular pathologies that involve phenotypic modulation of smooth muscle cells.
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Affiliation(s)
- Karolina M. Turczyńska
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Karl Swärd
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Tran Thi Hien
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Johan Wohlfahrt
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Ingrid Yao Mattisson
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Mari Ekman
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Johan Nilsson
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Johan Sjögren
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Vignesh Murugesan
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Anna Hultgårdh-Nilsson
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Pilar Cidad
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Per Hellstrand
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - M. Teresa Pérez-García
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
| | - Sebastian Albinsson
- From the Department of Experimental Medical Science (K.M.T., K.S., T.T.H., J.W., I.Y.M., M.E., V.M., A.H.-N., P.H., S.A.) and Department of Clinical Science (J.N., J.S.), Lund University, Lund, Sweden; and Departamento de Bioquímica y Biología Molecular y Fisiología and Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain (P.C., M.T.P.-G.)
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16
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A novel inhibitory mechanism of MRTF-A/B on the ICAM-1 gene expression in vascular endothelial cells. Sci Rep 2015; 5:10627. [PMID: 26024305 PMCID: PMC4448521 DOI: 10.1038/srep10627] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 04/22/2015] [Indexed: 01/09/2023] Open
Abstract
The roles of myocardin-related transcription factor A (MRTF-A) and MRTF-B in vascular endothelial cells are not completely understood. Here, we found a novel regulatory mechanism for MRTF-A/B function. MRTF-A/B tend to accumulate in the nucleus in arterial endothelial cells in vivo and human aortic endothelial cells (HAoECs) in vitro. In HAoECs, nuclear localization of MRTF-A/B was not significantly affected by Y27632 or latrunculin B, primarily due to the reduced binding of MRTF-A/B to G-actin and in part, to the low level of MRTF-A phosphorylation by ERK. MRTF-A/B downregulation by serum depletion or transfection of siRNA against MRTF-A and/or MRTF-B induced ICAM-1 expression in HAoECs. It is known that nuclear import of nuclear factor−κB (NF−κB) plays a key role in ICAM-1 gene transcription. However, nuclear accumulation of NF−κB p65 was not observed in MRTF-A/B-depleted HAoECs. Our present findings suggest that MRTF-A/B inhibit ICAM-1 mRNA expression by forming a complex with NF−κB p65 in the nucleus. Conversely, downregulation of MRTF-A/B alleviates this negative regulation without further translocation of NF−κB p65 into the nucleus. These results reveal the novel roles of MRTF-A/B in the homeostasis of vascular endothelium.
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17
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Rajakylä EK, Viita T, Kyheröinen S, Huet G, Treisman R, Vartiainen MK. RNA export factor Ddx19 is required for nuclear import of the SRF coactivator MKL1. Nat Commun 2015; 6:5978. [PMID: 25585691 PMCID: PMC4309436 DOI: 10.1038/ncomms6978] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/27/2014] [Indexed: 12/03/2022] Open
Abstract
Controlled transport of macromolecules between the cytoplasm and nucleus is essential for homeostatic regulation of cellular functions. For instance, gene expression entails coordinated nuclear import of transcriptional regulators to activate transcription and nuclear export of the resulting messenger RNAs for cytoplasmic translation. Here we link these two processes by reporting a novel role for the mRNA export factor Ddx19/Dbp5 in nuclear import of MKL1, the signal-responsive transcriptional activator of SRF. We show that Ddx19 is not a general nuclear import factor, and that its specific effect on MKL1 nuclear import is separate from its role in mRNA export. Both helicase and nuclear pore-binding activities of Ddx19 are dispensable for MKL1 nuclear import, but RNA binding is required. Mechanistically, Ddx19 operates by modulating the conformation of MKL1, which affects its interaction with Importin-β for efficient nuclear import. Thus, Ddx19 participates in mRNA export, translation and nuclear import of a key transcriptional regulator.
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Affiliation(s)
- Eeva Kaisa Rajakylä
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
| | - Tiina Viita
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
| | - Salla Kyheröinen
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
| | - Guillaume Huet
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
| | - Richard Treisman
- Transcription group, Cancer Research UK London Research Institute, London WC2A 3LY, UK
| | - Maria K. Vartiainen
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
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18
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Qi QR, Yang ZM. Regulation and function of signal transducer and activator of transcription 3. World J Biol Chem 2014; 5:231-239. [PMID: 24921012 PMCID: PMC4050116 DOI: 10.4331/wjbc.v5.i2.231] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Revised: 01/07/2014] [Accepted: 01/20/2014] [Indexed: 02/05/2023] Open
Abstract
Signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, is a key regulator of many physiological and pathological processes. Significant progress has been made in understanding the transcriptional control, posttranslational modification, cellular localization and functional regulation of STAT3. STAT3 can translocate into the nucleus and bind to specific promoter sequences, thereby exerting transcriptional regulation. Recent studies have shown that STAT3 can also translocate into mitochondria, participating in aerobic respiration and apoptosis. In addition, STAT3 plays an important role in inflammation and tumorigenesis by regulating cell proliferation, differentiation and metabolism. Conditional knockout mouse models make it possible to study the physiological function of STAT3 in specific tissues and organs. This review summarizes the latest advances in the understanding of the expression, regulation and function of STAT3 in physiological and tumorigenic processes.
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19
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RPEL proteins are the molecular targets for CCG-1423, an inhibitor of Rho signaling. PLoS One 2014; 9:e89016. [PMID: 24558465 PMCID: PMC3928398 DOI: 10.1371/journal.pone.0089016] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Accepted: 01/13/2014] [Indexed: 01/25/2023] Open
Abstract
Epithelial–msenchymal transition (EMT) is closely associated with cancer and tissue fibrosis. The nuclear accumulation of myocardin-related transcription factor A (MRTF-A/MAL/MKL1) plays a vital role in EMT. In various cells treated with CCG-1423, a novel inhibitor of Rho signaling, the nuclear accumulation of MRTF-A is inhibited. However, the molecular target of this inhibitor has not yet been identified. In this study, we investigated the mechanism of this effect of CCG-1423. The interaction between MRTF-A and importin α/β1 was inhibited by CCG-1423, but monomeric G-actin binding to MRTF-A was not inhibited. We coupled Sepharose with CCG-1423 (CCG-1423 Sepharose) to investigate this mechanism. A pull-down assay using CCG-1423 Sepharose revealed the direct binding of CCG-1423 to MRTF-A. Furthermore, we found that the N-terminal basic domain (NB) of MRTF-A, which acts as a functional nuclear localization signal (NLS) of MRTF-A, was the binding site for CCG-1423. G-actin did not bind to CCG-1423 Sepharose, but the interaction between MRTF-A and CCG-1423 Sepharose was reduced in the presence of G-actin. We attribute this result to the high binding affinity of MRTF-A for G-actin and the proximity of NB to G-actin-binding sites (RPEL motifs). Therefore, when MRTF-A forms a complex with G-actin, the binding of CCG-1423 to NB is expected to be blocked. NF-E2 related factor 2, which contains three distinct basic amino acid-rich NLSs, did not bind to CCG-1423 Sepharose, but other RPEL-containing proteins such as MRTF-B, myocardin, and Phactr1 bound to CCG-1423 Sepharose. These results suggest that the specific binding of CCG-1423 to the NLSs of RPEL-containing proteins. Our proposal to explain the inhibitory action of CCG-1423 is as follows: When the G-actin pool is depleted, CCG-1423 binds specifically to the NLS of MRTF-A/B and prevents the interaction between MRTF-A/B and importin α/β1, resulting in inhibition of the nuclear import of MRTF-A/B.
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20
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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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21
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Hayashi K, Morita T. Importance of dimer formation of myocardin family members in the regulation of their nuclear export. Cell Struct Funct 2013; 38:123-34. [PMID: 23594864 DOI: 10.1247/csf.13001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Myocardin (Mycd) family members function as a transcriptional cofactor for serum response factor (SRF). Dimer formation is necessary to exhibit their function, and the coiled-coil domain (CC) plays a critical role in their dimerization. We have recently revealed a detailed molecular mechanism for their Crm1 (exportin1)-mediated nuclear export. Here, we found other unique significances of the dimerization of Mycd family members. Introduction of mutations in the CC of myocardin-related transcription factor A (MRTF-A) and truncated Mycd resulted in significant decreases in their cytoplasmic localization and increases in their nuclear localization. In accordance with such subcellular localization changes, their binding to Crm1 were reduced. These results indicate that the dimerization of Mycd family members is necessary for their Crm1-mediated nuclear export. We have recently found that the N-terminal region of Mycd consisting of 128 amino acids (Mycd N128) self-associates to Mycd via the central basic domain (CB), resulting in masking the Crm1-binding site. Such self-association of MRTF-A would be unlikely. In this study, we also revealed that the dimerization of Mycd was also necessary for this self-association. Wild-type Mycd activated SRF-mediated transcription more potently than Mycd lacking the Mycd N128 (Mycd ΔN128) did. These results suggest two possible functions of the Mycd N128: 1) stabilization of Mycd dimer to enhance SRF-mediated transcription and 2) positive regulation of the transactivation ability of Mycd. These findings provide a new insight into the functional regulation of Mycd family members.
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Affiliation(s)
- Ken'ichiro Hayashi
- Department of Neuroscience, Osaka University Graduate School of Medicine, Japan.
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