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Tan Z, Chen P, Dong X, Guo S, Leung VYL, Cheung JPY, Chan D, Richardson SM, Hoyland JA, To MKT, Cheah KSE. Progenitor-like cells contributing to cellular heterogeneity in the nucleus pulposus are lost in intervertebral disc degeneration. Cell Rep 2024; 43:114342. [PMID: 38865240 DOI: 10.1016/j.celrep.2024.114342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 03/14/2024] [Accepted: 05/23/2024] [Indexed: 06/14/2024] Open
Abstract
The nucleus pulposus (NP) in the intervertebral disc (IVD) arises from embryonic notochord. Loss of notochordal-like cells in humans correlates with onset of IVD degeneration, suggesting that they are critical for healthy NP homeostasis and function. Comparative transcriptomic analyses identified expression of progenitor-associated genes (GREM1, KRT18, and TAGLN) in the young mouse and non-degenerated human NP, with TAGLN expression reducing with aging. Lineage tracing using Tagln-CreERt2 mice identified peripherally located proliferative NP (PeriNP) cells in developing and postnatal NP that provide a continuous supply of cells to the entire NP. PeriNP cells were diminished in aged mice and absent in puncture-induced degenerated discs. Single-cell transcriptomes of postnatal Tagln-CreERt2 IVD cells indicate enrichment for TGF-β signaling in Tagln descendant NP sub-populations. Notochord-specific removal of TGF-β/BMP mediator Smad4 results in loss of Tagln+ cells and abnormal NP morphologies. We propose Tagln+ PeriNP cells are potential progenitors crucial for NP homeostasis.
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Affiliation(s)
- Zhijia Tan
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China; Department of Orthopaedics and Traumatology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China; Shenzhen Clinical Research Center for Rare Diseases, The University of Hong Kong - Shenzhen Hospital, Shenzhen, China; Department of Orthopaedics and Traumatology, School of Clinical Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Peikai Chen
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China; Department of Orthopaedics and Traumatology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China; Shenzhen Clinical Research Center for Rare Diseases, The University of Hong Kong - Shenzhen Hospital, Shenzhen, China; Artificial Intelligence and Big Data Lab, The University of Hong Kong - Shenzhen Hospital, Shenzhen, China
| | - Xiaonan Dong
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Shuang Guo
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Victor Y L Leung
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Jason P Y Cheung
- Department of Orthopaedics and Traumatology, School of Clinical Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Danny Chan
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Stephen M Richardson
- Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, UK
| | - Judith A Hoyland
- Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, UK
| | - Michael K T To
- Department of Orthopaedics and Traumatology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China; Shenzhen Clinical Research Center for Rare Diseases, The University of Hong Kong - Shenzhen Hospital, Shenzhen, China; Department of Orthopaedics and Traumatology, School of Clinical Medicine, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kathryn S E Cheah
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
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2
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Kim JM. Molecular Link between DNA Damage Response and Microtubule Dynamics. Int J Mol Sci 2022; 23:ijms23136986. [PMID: 35805981 PMCID: PMC9266319 DOI: 10.3390/ijms23136986] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/20/2022] [Accepted: 06/21/2022] [Indexed: 11/16/2022] Open
Abstract
Microtubules are major components of the cytoskeleton that play important roles in cellular processes such as intracellular transport and cell division. In recent years, it has become evident that microtubule networks play a role in genome maintenance during interphase. In this review, we highlight recent advances in understanding the role of microtubule dynamics in DNA damage response and repair. We first describe how DNA damage checkpoints regulate microtubule organization and stability. We then highlight how microtubule networks are involved in the nuclear remodeling following DNA damage, which leads to changes in chromosome organization. Lastly, we discuss how microtubule dynamics participate in the mobility of damaged DNA and promote consequent DNA repair. Together, the literature indicates the importance of microtubule dynamics in genome organization and stability during interphase.
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Affiliation(s)
- Jung Min Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju 58128, Korea
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3
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Antón IM, Wandosell F. WIP, YAP/TAZ and Actin Connections Orchestrate Development and Transformation in the Central Nervous System. Front Cell Dev Biol 2021; 9:673986. [PMID: 34195190 PMCID: PMC8237755 DOI: 10.3389/fcell.2021.673986] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 05/12/2021] [Indexed: 01/01/2023] Open
Abstract
YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif) are transcription co-regulators that make up the terminal components of the Hippo signaling pathway, which plays a role in organ size control and derived tissue homeostasis through regulation of the proliferation, differentiation and apoptosis of a wide variety of differentiated and stem cells. Hippo/YAP signaling contributes to normal development of the nervous system, as it participates in self-renewal of neural stem cells, proliferation of neural progenitor cells and differentiation, activation and myelination of glial cells. Not surprisingly, alterations in this pathway underlie the development of severe neurological diseases. In glioblastomas, YAP and TAZ levels directly correlate with the amount of the actin-binding molecule WIP (WASP interacting protein), which regulates stemness and invasiveness. In neurons, WIP modulates cytoskeleton dynamics through actin polymerization/depolymerization and acts as a negative regulator of neuritogenesis, dendrite branching and dendritic spine formation. Our working hypothesis is that WIP regulates the YAP/TAZ pools using a Hippo-independent pathway. Thus, in this review we will present some of the data that links WIP, YAP and TAZ, with a focus on their function in cells from the central and peripheral nervous systems. It is hoped that a better understanding of the mechanisms involved in brain and nervous development and the pathologies that arise due to their alteration will reveal novel therapeutic targets for neurologic diseases.
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Affiliation(s)
- Inés M Antón
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología (CNB-CSIC), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Francisco Wandosell
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.,Departamento de Neuropatología Molecular, Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
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4
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Kepser LJ, Khudayberdiev S, Hinojosa LS, Macchi C, Ruscica M, Marcello E, Culmsee C, Grosse R, Rust MB. Cyclase-associated protein 2 (CAP2) controls MRTF-A localization and SRF activity in mouse embryonic fibroblasts. Sci Rep 2021; 11:4789. [PMID: 33637797 PMCID: PMC7910472 DOI: 10.1038/s41598-021-84213-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 02/12/2021] [Indexed: 01/09/2023] Open
Abstract
Recent studies identified cyclase-associated proteins (CAPs) as important regulators of actin dynamics that control assembly and disassembly of actin filaments (F-actin). While these studies significantly advanced our knowledge of their molecular functions, the physiological relevance of CAPs largely remained elusive. Gene targeting in mice implicated CAP2 in heart physiology and skeletal muscle development. Heart defects in CAP2 mutant mice were associated with altered activity of serum response factor (SRF), a transcription factor involved in multiple biological processes including heart function, but also skeletal muscle development. By exploiting mouse embryonic fibroblasts (MEFs) from CAP2 mutant mice, we aimed at deciphering the CAP2-dependent mechanism relevant for SRF activity. Reporter assays and mRNA quantification by qPCR revealed reduced SRF-dependent gene expression in mutant MEFs. Reduced SRF activity in CAP2 mutant MEFs was associated with altered actin turnover, a shift in the actin equilibrium towards monomeric actin (G-actin) as well as and reduced nuclear levels of myocardin-related transcription factor A (MRTF-A), a transcriptional SRF coactivator that is shuttled out of the nucleus and, hence, inhibited upon G-actin binding. Moreover, pharmacological actin manipulation with jasplakinolide restored MRTF-A distribution in mutant MEFs. Our data are in line with a model in which CAP2 controls the MRTF-SRF pathway in an actin-dependent manner. While MRTF-A localization and SRF activity was impaired under basal conditions, serum stimulation induced nuclear MRTF-A translocation and SRF activity in mutant MEFs similar to controls. In summary, our data revealed that in MEFs CAP2 controls basal MRTF-A localization and SRF activity, while it was dispensable for serum-induced nuclear MRTF-A translocation and SRF stimulation.
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Affiliation(s)
- Lara-Jane Kepser
- Institute of Physiological Chemistry, Philipps-University of Marburg, 35032, Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-University of Marburg, 35032, Marburg, Germany
| | - Sharof Khudayberdiev
- Institute of Physiological Chemistry, Philipps-University of Marburg, 35032, Marburg, Germany
| | - Laura Soto Hinojosa
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-University of Marburg, 35032, Marburg, Germany
- Institute of Pharmacology, University of Marburg, 35032, Marburg, Germany
| | - Chiara Macchi
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133, Milan, Italy
| | - Massimiliano Ruscica
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133, Milan, Italy
| | - Elena Marcello
- Department of Pharmacological and Biomolecular Sciences, University of Milan, 20133, Milan, Italy
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35032, Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus-Liebig-University Giessen, Hans-Meerwein-Strasse 6, 35032, Marburg, Germany
| | - Robert Grosse
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-University of Marburg, 35032, Marburg, Germany
- Institute of Pharmacology, University of Marburg, 35032, Marburg, Germany
| | - Marco B Rust
- Institute of Physiological Chemistry, Philipps-University of Marburg, 35032, Marburg, Germany.
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-University of Marburg, 35032, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus-Liebig-University Giessen, Hans-Meerwein-Strasse 6, 35032, Marburg, Germany.
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5
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Hannezo E, Heisenberg CP. Mechanochemical Feedback Loops in Development and Disease. Cell 2020; 178:12-25. [PMID: 31251912 DOI: 10.1016/j.cell.2019.05.052] [Citation(s) in RCA: 179] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/17/2019] [Accepted: 05/24/2019] [Indexed: 12/31/2022]
Abstract
There is increasing evidence that both mechanical and biochemical signals play important roles in development and disease. The development of complex organisms, in particular, has been proposed to rely on the feedback between mechanical and biochemical patterning events. This feedback occurs at the molecular level via mechanosensation but can also arise as an emergent property of the system at the cellular and tissue level. In recent years, dynamic changes in tissue geometry, flow, rheology, and cell fate specification have emerged as key platforms of mechanochemical feedback loops in multiple processes. Here, we review recent experimental and theoretical advances in understanding how these feedbacks function in development and disease.
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Affiliation(s)
- Edouard Hannezo
- Institute of Science and Technology Austria, Klosterneuburg, Austria.
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6
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Hurst V, Shimada K, Gasser SM. Nuclear Actin and Actin-Binding Proteins in DNA Repair. Trends Cell Biol 2019; 29:462-476. [PMID: 30954333 DOI: 10.1016/j.tcb.2019.02.010] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/25/2019] [Accepted: 02/26/2019] [Indexed: 12/27/2022]
Abstract
Nuclear actin has been implicated in a variety of DNA-related processes including chromatin remodeling, transcription, replication, and DNA repair. However, the mechanistic understanding of actin in these processes has been limited, largely due to a lack of research tools that address the roles of nuclear actin specifically, that is, distinct from its cytoplasmic functions. Recent findings support a model for homology-directed DNA double-strand break (DSB) repair in which a complex of ARP2 and ARP3 (actin-binding proteins 2 and 3) binds at the break and works with actin to promote DSB clustering and homology-directed repair. Further, it has been reported that relocalization of heterochromatic DSBs to the nuclear periphery in Drosophila is ARP2/3 dependent and actin-myosin driven. Here we provide an overview of the role of nuclear actin and actin-binding proteins in DNA repair, critically evaluating the experimental tools used and potential indirect effects.
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Affiliation(s)
- Verena Hurst
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland; University of Basel, Faculty of Natural Sciences, CH-4056 Basel, Switzerland
| | - Kenji Shimada
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland; University of Basel, Faculty of Natural Sciences, CH-4056 Basel, Switzerland.
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7
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Jalal S, Shi S, Acharya V, Huang RYJ, Viasnoff V, Bershadsky AD, Tee YH. Actin cytoskeleton self-organization in single epithelial cells and fibroblasts under isotropic confinement. J Cell Sci 2019; 132:jcs.220780. [PMID: 30787030 PMCID: PMC6432717 DOI: 10.1242/jcs.220780] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 01/24/2019] [Indexed: 12/23/2022] Open
Abstract
Actin cytoskeleton self-organization in two cell types, fibroblasts and epitheliocytes, was studied in cells confined to isotropic adhesive islands. In fibroblasts plated onto islands of optimal size, an initially circular actin pattern evolves into a radial pattern of actin bundles that undergo asymmetric chiral swirling before finally producing parallel linear stress fibers. Epitheliocytes, however, did not exhibit succession through all the actin patterns described above. Upon confinement, the actin cytoskeleton in non-keratinocyte epitheliocytes was arrested at the circular stage, while in keratinocytes it progressed as far as the radial pattern but still could not break symmetry. Epithelial–mesenchymal transition pushed actin cytoskeleton development from circular towards radial patterns but remained insufficient to cause chirality. Knockout of cytokeratins also did not promote actin chirality development in keratinocytes. Left–right asymmetric cytoskeleton swirling could, however, be induced in keratinocytes by treatment with small doses of the G-actin sequestering drug, latrunculin A in a transcription-independent manner. Both the nucleus and the cytokeratin network followed the induced chiral swirling. Development of chirality in keratinocytes was controlled by DIAPH1 (mDia1) and VASP, proteins involved in regulation of actin polymerization. This article has an associated First Person interview with the first author of the paper. Summary: Epitheliocytes cannot develop the F-actin patterns typically observed in fibroblasts, but can do so after treatments affecting actin polymerization. Regulators of actin polymerization, DIAPH1 and VASP, control this process.
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Affiliation(s)
- Salma Jalal
- Mechanobiology Institute, National University of Singapore, Singapore 117411
| | - Shidong Shi
- Mechanobiology Institute, National University of Singapore, Singapore 117411
| | | | - Ruby Yun-Ju Huang
- Cancer Science Institute of Singapore, National University of Singapore, Singapore 117599.,Department of Obstetrics & Gynaecology, National University Hospital, Singapore 119228.,Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599
| | - Virgile Viasnoff
- Mechanobiology Institute, National University of Singapore, Singapore 117411.,Centre National Pour la Recherche Scientifique, Singapore 117411.,Department of Biological Sciences, National University of Singapore, Singapore 117558
| | - Alexander D Bershadsky
- Mechanobiology Institute, National University of Singapore, Singapore 117411 .,Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Yee Han Tee
- Mechanobiology Institute, National University of Singapore, Singapore 117411
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8
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Mtss1 promotes maturation and maintenance of cerebellar neurons via splice variant-specific effects. Brain Struct Funct 2017; 222:2787-2805. [DOI: 10.1007/s00429-017-1372-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 01/17/2017] [Indexed: 11/26/2022]
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9
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Miroshnikova YA, Nava MM, Wickström SA. Emerging roles of mechanical forces in chromatin regulation. J Cell Sci 2017. [DOI: 10.1242/jcs.202192] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
ABSTRACT
Cells are constantly subjected to a spectrum of mechanical cues, such as shear stress, compression, differential tissue rigidity and strain, to which they adapt by engaging mechanisms of mechanotransduction. While the central role of cell adhesion receptors in this process is established, it has only recently been appreciated that mechanical cues reach far beyond the plasma membrane and the cytoskeleton, and are directly transmitted to the nucleus. Furthermore, changes in the mechanical properties of the perinuclear cytoskeleton, nuclear lamina and chromatin are critical for cellular responses and adaptation to external mechanical cues. In that respect, dynamic changes in the nuclear lamina and the surrounding cytoskeleton modify mechanical properties of the nucleus, thereby protecting genetic material from damage. The importance of this mechanism is highlighted by debilitating genetic diseases, termed laminopathies, that result from impaired mechanoresistance of the nuclear lamina. What has been less evident, and represents one of the exciting emerging concepts, is that chromatin itself is an active rheological element of the nucleus, which undergoes dynamic changes upon application of force, thereby facilitating cellular adaption to differential force environments. This Review aims to highlight these emerging concepts by discussing the latest literature in this area and by proposing an integrative model of cytoskeletal and chromatin-mediated responses to mechanical stress.
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Affiliation(s)
| | - Michele M. Nava
- Paul Gerson Unna Group ‘Skin Homeostasis and Ageing’, Max Planck Institute for Biology of Ageing, Cologne 50931, Germany
| | - Sara A. Wickström
- Paul Gerson Unna Group ‘Skin Homeostasis and Ageing’, Max Planck Institute for Biology of Ageing, Cologne 50931, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne 50931, Germany
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10
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Mechanical regulation of transcription controls Polycomb-mediated gene silencing during lineage commitment. Nat Cell Biol 2016; 18:864-75. [PMID: 27398909 DOI: 10.1038/ncb3387] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Accepted: 06/09/2016] [Indexed: 02/06/2023]
Abstract
Tissue mechanics drive morphogenesis, but how forces are sensed and transmitted to control stem cell fate and self-organization remains unclear. We show that a mechanosensory complex of emerin (Emd), non-muscle myosin IIA (NMIIA) and actin controls gene silencing and chromatin compaction, thereby regulating lineage commitment. Force-driven enrichment of Emd at the outer nuclear membrane of epidermal stem cells leads to defective heterochromatin anchoring to the nuclear lamina and a switch from H3K9me2,3 to H3K27me3 occupancy at constitutive heterochromatin. Emd enrichment is accompanied by the recruitment of NMIIA to promote local actin polymerization that reduces nuclear actin levels, resulting in attenuation of transcription and subsequent accumulation of H3K27me3 at facultative heterochromatin. Perturbing this mechanosensory pathway by deleting NMIIA in mouse epidermis leads to attenuated H3K27me3-mediated silencing and precocious lineage commitment, abrogating morphogenesis. Our results reveal how mechanics integrate nuclear architecture and chromatin organization to control lineage commitment and tissue morphogenesis.
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11
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Bamburg JR, Bernstein BW. Actin dynamics and cofilin-actin rods in alzheimer disease. Cytoskeleton (Hoboken) 2016; 73:477-97. [PMID: 26873625 DOI: 10.1002/cm.21282] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 12/18/2022]
Abstract
Cytoskeletal abnormalities and synaptic loss, typical of both familial and sporadic Alzheimer disease (AD), are induced by diverse stresses such as neuroinflammation, oxidative stress, and energetic stress, each of which may be initiated or enhanced by proinflammatory cytokines or amyloid-β (Aβ) peptides. Extracellular Aβ-containing plaques and intracellular phospho-tau-containing neurofibrillary tangles are postmortem pathologies required to confirm AD and have been the focus of most studies. However, AD brain, but not normal brain, also have increased levels of cytoplasmic rod-shaped bundles of filaments composed of ADF/cofilin-actin in a 1:1 complex (rods). Cofilin, the major ADF/cofilin isoform in mammalian neurons, severs actin filaments at low cofilin/actin ratios and stabilizes filaments at high cofilin/actin ratios. It binds cooperatively to ADP-actin subunits in F-actin. Cofilin is activated by dephosphorylation and may be oxidized in stressed neurons to form disulfide-linked dimers, required for bundling cofilin-actin filaments into stable rods. Rods form within neurites causing synaptic dysfunction by sequestering cofilin, disrupting normal actin dynamics, blocking transport, and exacerbating mitochondrial membrane potential loss. Aβ and proinflammatory cytokines induce rods through a cellular prion protein-dependent activation of NADPH oxidase and production of reactive oxygen species. Here we review recent advances in our understanding of cofilin biochemistry, rod formation, and the development of cognitive deficits. We will then discuss rod formation as a molecular pathway for synapse loss that may be common between all three prominent current AD hypotheses, thus making rods an attractive therapeutic target. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- James R Bamburg
- Department of Biochemistry and Molecular Biology and the Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO.
| | - Barbara W Bernstein
- Department of Biochemistry and Molecular Biology and the Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO
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12
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Figueroa-Angulo EE, Calla-Choque JS, Mancilla-Olea MI, Arroyo R. RNA-Binding Proteins in Trichomonas vaginalis: Atypical Multifunctional Proteins. Biomolecules 2015; 5:3354-95. [PMID: 26703754 PMCID: PMC4693282 DOI: 10.3390/biom5043354] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/07/2015] [Accepted: 11/12/2015] [Indexed: 01/08/2023] Open
Abstract
Iron homeostasis is highly regulated in vertebrates through a regulatory system mediated by RNA-protein interactions between the iron regulatory proteins (IRPs) that interact with an iron responsive element (IRE) located in certain mRNAs, dubbed the IRE-IRP regulatory system. Trichomonas vaginalis, the causal agent of trichomoniasis, presents high iron dependency to regulate its growth, metabolism, and virulence properties. Although T. vaginalis lacks IRPs or proteins with aconitase activity, possesses gene expression mechanisms of iron regulation at the transcriptional and posttranscriptional levels. However, only one gene with iron regulation at the transcriptional level has been described. Recently, our research group described an iron posttranscriptional regulatory mechanism in the T. vaginalis tvcp4 and tvcp12 cysteine proteinase mRNAs. The tvcp4 and tvcp12 mRNAs have a stem-loop structure in the 5'-coding region or in the 3'-UTR, respectively that interacts with T. vaginalis multifunctional proteins HSP70, α-Actinin, and Actin under iron starvation condition, causing translation inhibition or mRNA stabilization similar to the previously characterized IRE-IRP system in eukaryotes. Herein, we summarize recent progress and shed some light on atypical RNA-binding proteins that may participate in the iron posttranscriptional regulation in T. vaginalis.
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Affiliation(s)
- Elisa E Figueroa-Angulo
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Av. IPN # 2508, Col. San Pedro Zacatenco, CP 07360 México, D.F., Mexico.
| | - Jaeson S Calla-Choque
- Laboratorio de Inmunopatología en Neurocisticercosis, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Urb. Ingeniería, S.M.P., Lima 15102, Peru.
| | - Maria Inocente Mancilla-Olea
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Av. IPN # 2508, Col. San Pedro Zacatenco, CP 07360 México, D.F., Mexico.
| | - Rossana Arroyo
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Av. IPN # 2508, Col. San Pedro Zacatenco, CP 07360 México, D.F., Mexico.
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13
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Plattner H. Signalling in ciliates: long- and short-range signals and molecular determinants for cellular dynamics. Biol Rev Camb Philos Soc 2015; 92:60-107. [PMID: 26487631 DOI: 10.1111/brv.12218] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 07/28/2015] [Accepted: 08/21/2015] [Indexed: 12/30/2022]
Abstract
In ciliates, unicellular representatives of the bikont branch of evolution, inter- and intracellular signalling pathways have been analysed mainly in Paramecium tetraurelia, Paramecium multimicronucleatum and Tetrahymena thermophila and in part also in Euplotes raikovi. Electrophysiology of ciliary activity in Paramecium spp. is a most successful example. Established signalling mechanisms include plasmalemmal ion channels, recently established intracellular Ca2+ -release channels, as well as signalling by cyclic nucleotides and Ca2+ . Ca2+ -binding proteins (calmodulin, centrin) and Ca2+ -activated enzymes (kinases, phosphatases) are involved. Many organelles are endowed with specific molecules cooperating in signalling for intracellular transport and targeted delivery. Among them are recently specified soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), monomeric GTPases, H+ -ATPase/pump, actin, etc. Little specification is available for some key signal transducers including mechanosensitive Ca2+ -channels, exocyst complexes and Ca2+ -sensor proteins for vesicle-vesicle/membrane interactions. The existence of heterotrimeric G-proteins and of G-protein-coupled receptors is still under considerable debate. Serine/threonine kinases dominate by far over tyrosine kinases (some predicted by phosphoproteomic analyses). Besides short-range signalling, long-range signalling also exists, e.g. as firmly installed microtubular transport rails within epigenetically determined patterns, thus facilitating targeted vesicle delivery. By envisaging widely different phenomena of signalling and subcellular dynamics, it will be shown (i) that important pathways of signalling and cellular dynamics are established already in ciliates, (ii) that some mechanisms diverge from higher eukaryotes and (iii) that considerable uncertainties still exist about some essential aspects of signalling.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, PO Box M625, 78457, Konstanz, Germany
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14
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de Vallière C, Vidal S, Clay I, Jurisic G, Tcymbarevich I, Lang S, Ludwig MG, Okoniewski M, Eloranta JJ, Kullak-Ublick GA, Wagner CA, Rogler G, Seuwen K. The pH-sensing receptor OGR1 improves barrier function of epithelial cells and inhibits migration in an acidic environment. Am J Physiol Gastrointest Liver Physiol 2015. [PMID: 26206859 DOI: 10.1152/ajpgi.00408.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pH-sensing receptor ovarian cancer G protein-coupled receptor 1 (OGR1; GPR68) is expressed in the gut. Inflammatory bowel disease is typically associated with a decrease in local pH, which may lead to altered epithelial barrier function and subsequent gastrointestinal repair involving epithelial cell adhesion and migration. As the mechanisms underlying the response to pH changes are not well understood, we have investigated OGR1-mediated, pH-dependent signaling pathways in intestinal epithelial cells. Caco-2 cells stably overexpressing OGR1 were created and validated as tools to study OGR1 signaling. Barrier function, migration, and proliferation were measured using electric cell-substrate impedance-sensing technology. Localization of the tight junction proteins zonula occludens protein 1 and occludin and the rearrangement of cytoskeletal actin were examined by confocal microscopy. Paracellular permeability and protein and gene expression analysis using DNA microarrays were performed on filter-grown Caco-2 monolayers. We report that an acidic pH shift from pH 7.8 to 6.6 improved barrier function and stimulated reorganization of filamentous actin with prominent basal stress fiber formation. Cell migration and proliferation during in vitro wound healing were inhibited. Gene expression analysis revealed significant upregulation of genes related to cytoskeleton remodeling, cell adhesion, and growth factor signaling. We conclude that acidic extracellular pH can have a signaling function and impact the physiology of intestinal epithelial cells. The deconstruction of OGR1-dependent signaling may aid our understanding of mucosal inflammation mechanisms.
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Affiliation(s)
- Cheryl de Vallière
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland; Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Solange Vidal
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Ieuan Clay
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Giorgia Jurisic
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Irina Tcymbarevich
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland
| | - Silvia Lang
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland
| | | | - Michal Okoniewski
- Functional Genomics Center, University of Zurich, Zurich, Switzerland
| | - Jyrki J Eloranta
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
| | - Gerd A Kullak-Ublick
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and Zurich Center for Integrative Human Physiology, Zurich, Switzerland
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, Zurich, Switzerland
| | - Klaus Seuwen
- Novartis Institutes for Biomedical Research, Basel, Switzerland;
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15
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Abstract
Contrary to cytoplasmic actin structures, the biological functions of nuclear actin filaments remain largely enigmatic. Recent progress in the field, however, has determined nuclear actin structures in somatic cells either under steady state conditions or in response to extracellular signaling cues. These actin structures differ in size and shape as well as in their temporal appearance and dynamics. Thus, a picture emerges that suggests that mammalian cells may have different pathways and mechanisms to assemble nuclear actin filaments. Apart from serum- or LPA-triggered nuclear actin polymerization, integrin activation by extracellular matrix interaction was recently implicated in nuclear actin polymerization through the linker of nucleoskeleton and cytoskeleton (LINC) complex. Some of these extracellular cues known so far appear to converge at the level of nuclear formin activity and subsequent regulation of myocardin-related transcription factors. Nevertheless, as the precise signaling events are as yet unknown, the regulation of nuclear actin polymerization may be of significant importance for different cellular functions as well as disease conditions caused by altered nuclear dynamics and architecture.
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16
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Kalo A, Kanter I, Shraga A, Sheinberger J, Tzemach H, Kinor N, Singer RH, Lionnet T, Shav-Tal Y. Cellular Levels of Signaling Factors Are Sensed by β-actin Alleles to Modulate Transcriptional Pulse Intensity. Cell Rep 2015; 11:419-32. [PMID: 25865891 DOI: 10.1016/j.celrep.2015.03.039] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 02/18/2015] [Accepted: 03/16/2015] [Indexed: 01/11/2023] Open
Abstract
The transcriptional response of β-actin to extra-cellular stimuli is a paradigm for transcription factor complex assembly and regulation. Serum induction leads to a precisely timed pulse of β-actin transcription in the cell population. Actin protein is proposed to be involved in this response, but it is not known whether cellular actin levels affect nuclear β-actin transcription. We perturbed the levels of key signaling factors and examined the effect on the induced transcriptional pulse by following endogenous β-actin alleles in single living cells. Lowering serum response factor (SRF) protein levels leads to loss of pulse integrity, whereas reducing actin protein levels reveals positive feedback regulation, resulting in elevated gene activation and a prolonged transcriptional response. Thus, transcriptional pulse fidelity requires regulated amounts of signaling proteins, and perturbations in factor levels eliminate the physiological response, resulting in either tuning down or exaggeration of the transcriptional pulse.
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Affiliation(s)
- Alon Kalo
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Itamar Kanter
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Amit Shraga
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Jonathan Sheinberger
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Hadar Tzemach
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Noa Kinor
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Robert H Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Transcription Imaging Consortium, Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA; Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Timothée Lionnet
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Transcription Imaging Consortium, Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA
| | - Yaron Shav-Tal
- The Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan 5290002, Israel.
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17
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Plessner M, Melak M, Chinchilla P, Baarlink C, Grosse R. Nuclear F-actin formation and reorganization upon cell spreading. J Biol Chem 2015; 290:11209-16. [PMID: 25759381 DOI: 10.1074/jbc.m114.627166] [Citation(s) in RCA: 184] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Indexed: 12/30/2022] Open
Abstract
We recently discovered signal-regulated nuclear actin network assembly. However, in contrast to cytoplasmic actin regulation, polymeric nuclear actin structures and functions remain only poorly understood. Here we describe a novel molecular tool to visualize real-time nuclear actin dynamics by targeting the Actin-Chromobody-TagGFP to the nucleus, thus establishing a nuclear Actin-Chromobody. Interestingly, we observe nuclear actin polymerization into dynamic filaments upon cell spreading and fibronectin stimulation, both of which appear to be triggered by integrin signaling. Furthermore, we show that nucleoskeletal proteins such as the LINC (linker of nucleoskeleton and cytoskeleton) complex and components of the nuclear lamina couple cell spreading or integrin activation by fibronectin to nuclear actin polymerization. Spreading-induced nuclear actin polymerization results in serum response factor (SRF)-mediated transcription through nuclear retention of myocardin-related transcription factor A (MRTF-A). Our results reveal a signaling pathway, which links integrin activation by extracellular matrix interaction to nuclear actin polymerization through the LINC complex, and therefore suggest a role for nuclear actin polymerization in the context of cellular adhesion and mechanosensing.
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Affiliation(s)
- Matthias Plessner
- From the Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, Karl-von-Frisch-Strasse 1, 35043 Marburg, Germany
| | - Michael Melak
- From the Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, Karl-von-Frisch-Strasse 1, 35043 Marburg, Germany
| | - Pilar Chinchilla
- From the Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, Karl-von-Frisch-Strasse 1, 35043 Marburg, Germany
| | - Christian Baarlink
- From the Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, Karl-von-Frisch-Strasse 1, 35043 Marburg, Germany
| | - Robert Grosse
- From the Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, Karl-von-Frisch-Strasse 1, 35043 Marburg, Germany
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18
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Schweinhuber SK, Meßerschmidt T, Hänsch R, Korte M, Rothkegel M. Profilin isoforms modulate astrocytic morphology and the motility of astrocytic processes. PLoS One 2015; 10:e0117244. [PMID: 25629407 PMCID: PMC4309604 DOI: 10.1371/journal.pone.0117244] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 12/22/2014] [Indexed: 01/17/2023] Open
Abstract
The morphology of astrocytic processes determines their close structural association with synapses referred to as the ‘tripartite synapse’. Concerted morphological plasticity processes at tripartite synapses are supposed to shape neuronal communication. Morphological changes in astrocytes as well as the motility of astrocytic processes require remodeling of the actin cytoskeleton. Among the regulators of fast timescale actin-based motility, the actin binding protein profilin 1 has recently been shown to control the activity-dependent outgrowth of astrocytic processes. Here, we demonstrate that cultured murine astrocytes in addition to the ubiquitous profilin 1 also express the neuronal isoform profilin 2a. To analyze the cellular function of both profilins in astrocytes, we took advantage of a shRNA mediated isoform-specific downregulation. Interestingly, consistent with earlier results in neurons, we found redundant as well as isoform-specific functions of both profilins in modulating cellular physiology. The knockdown of either profilin 1 or profilin 2a led to a significant decrease in cell spreading of astrocytes. In contrast, solely the knockdown of profilin 2a resulted in a significantly reduced morphological complexity of astrocytes in both dissociated and slice culture astrocytes. Moreover, both isoforms proved to be crucial for forskolin-induced astrocytic stellation. Furthermore, forskolin treatment resulted in isoform-specific changes in the phosphorylation level of profilin 1 and profilin 2a, leading to a PKA-dependent phosphorylation of profilin 2a. In addition, transwell assays revealed an involvement of both isoforms in the motility of astrocytic processes, while FRAP analysis displayed an isoform-specific role of profilin 1 in the regulation of actin dynamics in peripheral astrocytic processes. Taken together, we suggest profilin isoforms to be important modulators of astrocytic morphology and motility with overlapping as well as isoform-specific functions.
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Affiliation(s)
| | - Tania Meßerschmidt
- Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, Germany
| | - Robert Hänsch
- Molecular and Cell Biology of Plants, Institute of Plant Biology, TU Braunschweig, Braunschweig, Germany
| | - Martin Korte
- Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, Germany
| | - Martin Rothkegel
- Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, Germany
- * E-mail:
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19
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Abstract
Physical working capacity decreases with age and also in microgravity. Regardless of age, increased physical activity can always improve the physical adaptability of the body, although the mechanisms of this adaptability are unknown. Physical exercise produces various mechanical stimuli in the body, and these stimuli may be essential for cell survival in organisms. The cytoskeleton plays an important role in maintaining cell shape and tension development, and in various molecular and/or cellular organelles involved in cellular trafficking. Both intra and extracellular stimuli send signals through the cytoskeleton to the nucleus and modulate gene expression via an intrinsic property, namely the "dynamic instability" of cytoskeletal proteins. αB-crystallin is an important chaperone for cytoskeletal proteins in muscle cells. Decreases in the levels of αB-crystallin are specifically associated with a marked decrease in muscle mass (atrophy) in a rat hindlimb suspension model that mimics muscle and bone atrophy that occurs in space and increases with passive stretch. Moreover, immunofluorescence data show complete co-localization of αB-crystallin and the tubulin/microtubule system in myoblast cells. This association was further confirmed in biochemical experiments carried out in vitro showing that αB-crystallin acts as a chaperone for heat-denatured tubulin and prevents microtubule disassembly induced by calcium. Physical activity induces the constitutive expression of αB-crystallin, which helps to maintain the homeostasis of cytoskeleton dynamics in response to gravitational forces. This relationship between chaperone expression levels and regulation of cytoskeletal dynamics observed in slow anti-gravitational muscles as well as in mammalian striated muscles, such as those in the heart, diaphragm and tongue, may have been especially essential for human evolution in particular. Elucidation of the intrinsic properties of the tubulin/microtubule and chaperone αB-crystallin protein complex systems is expected to provide valuable information for high-pressure bioscience and gravity health science.
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Affiliation(s)
- Yoriko Atomi
- 204 Research Center for Science and Technology, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo, 184-8588, Japan,
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20
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Albores-Saavedra J, Dorantes-Heredia R, Chablé-Montero F, Chanona-Vilchis J, Pérez-Montiel D, Lino-Silva LS, González-Romo MA, Ramírez-Jaramillo JM, Henson DE. Endometrial stromal sarcomas: immunoprofile with emphasis on HMB45 reactivity. Am J Clin Pathol 2014; 141:850-5. [PMID: 24838330 DOI: 10.1309/ajcps88cmjrxzbwa] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
OBJECTIVES We describe the morphologic and immunohistochemical features of 17 endometrial stromal neoplasms, 16 sarcomas, and one stromal nodule. METHODS We reviewed 35 cases interpreted as endometrial stromal neoplasms, but 17 high-grade endometrial stromal sarcomas (ESS) and one case of mixed endometrial sarcoma and leiomyosarcoma were excluded from the study. Data from the Surveillance Epidemiology and End Results program on low- and high-grade ESS for 1973 through 2003 were obtained. RESULTS One uterine primary ESS had collections of clear cells (20%), while a metastatic ESS contained predominantly clear cells (90%). CD10 (88.2%) and smooth muscle actin (70.5%) were the most common positive immunohistochemical markers. The latter marker was located in the cytoplasm in 47% of the ESS and in the nucleus in 23.5%, a previously unreported feature. HMB45 was detected in 23.5% of the ESS, which contrasts with the 2% reported by other authors. CONCLUSIONS The presence of clear cells and HMB45 reactivity does not justify the term perivascular epithelioid cell tumors for these neoplasms. Two of 17 patients with ESS died of metastatic disease. However, among 274 cases of ESS (all stages included) collected by the Surveillance Epidemiology and End Results Program of the National Cancer Institute during a 30-year period, the 10-year survival rate was 94%.
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Affiliation(s)
- Jorge Albores-Saavedra
- Medica Sur Clinic and Foundation, México City, México
- Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México City, México
| | - Rita Dorantes-Heredia
- Medica Sur Clinic and Foundation, México City, México
- Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México City, México
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21
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Abstract
Many if not most proteins can, under certain conditions, change cellular compartments, such as, for example, shuttling from the cytoplasm to the nucleus. Thus, many proteins may exert functions in various and very different subcellular locations, depending on the signaling context. A large amount of actin regulatory proteins has been detected in the mammalian cell nucleus, although their potential roles are much debated and are just beginning to emerge. Recently, members of the formin family of actin nucleators were also reported to dynamically localize to the nuclear environment. Here we discuss our findings that specific diaphanous-related formins can promote nuclear actin assembly in a signal-dependent manner.
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Affiliation(s)
- Christian Baarlink
- Institute of Pharmacology, Biochemical-Pharmacological Center (BPC) Marburg; University of Marburg; Marburg, Germany
| | - Robert Grosse
- Institute of Pharmacology, Biochemical-Pharmacological Center (BPC) Marburg; University of Marburg; Marburg, Germany
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