51
|
Sen B, Xie Z, Uzer G, Thompson WR, Styner M, Wu X, Rubin J. Intranuclear Actin Regulates Osteogenesis. Stem Cells 2016; 33:3065-76. [PMID: 26140478 DOI: 10.1002/stem.2090] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 06/02/2015] [Accepted: 06/06/2015] [Indexed: 12/22/2022]
Abstract
Depolymerization of the actin cytoskeleton induces nuclear trafficking of regulatory proteins and global effects on gene transcription. We here show that in mesenchymal stem cells (MSCs), cytochalasin D treatment causes rapid cofilin-/importin-9-dependent transfer of G-actin into the nucleus. The continued presence of intranuclear actin, which forms rod-like structures that stain with phalloidin, is associated with induction of robust expression of the osteogenic genes osterix and osteocalcin in a Runx2-dependent manner, and leads to acquisition of osteogenic phenotype. Adipogenic differentiation also occurs, but to a lesser degree. Intranuclear actin leads to nuclear export of Yes-associated protein (YAP); maintenance of nuclear YAP inhibits Runx2 initiation of osteogenesis. Injection of cytochalasin into the tibial marrow space of live mice results in abundant bone formation within the space of 1 week. In sum, increased intranuclear actin forces MSC into osteogenic lineage through controlling Runx2 activity; this process may be useful for clinical objectives of forming bone.
Collapse
Affiliation(s)
- Buer Sen
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Zhihui Xie
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Gunes Uzer
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - William R Thompson
- Department of Physical Therapy, University of Indiana-Purdue, Indianapolis, Indiana
| | - Maya Styner
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Xin Wu
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Janet Rubin
- Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| |
Collapse
|
52
|
Verboon JM, Sugumar B, Parkhurst SM. Wiskott-Aldrich syndrome proteins in the nucleus: aWASH with possibilities. Nucleus 2016; 6:349-59. [PMID: 26305109 PMCID: PMC4915506 DOI: 10.1080/19491034.2015.1086051] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actin and proteins that regulate its dynamics or interactions have well-established roles in the cytoplasm where they function as key components of the cytoskeleton to control diverse processes, including cellular infrastructure, cellular motility, cell signaling, and vesicle transport. Recent work has also uncovered roles for actin and its regulatory proteins in the nucleus, primarily in mechanisms governing gene expression. The Wiskott Aldrich Syndrome (WAS) family of proteins, comprising the WASP/N-WASP, SCAR/WAVE, WHAMM/JMY/WHAMY, and WASH subfamilies, function in the cytoplasm where they activate the Arp2/3 complex to form branched actin filaments. WAS proteins are present in the nucleus and have been implicated as transcriptional regulators. We found that Drosophila Wash, in addition to transcriptional effects, is involved in global nuclear architecture. Here we summarize the regulation and function of nuclear WAS proteins, and highlight how our work with Wash expands the possibilities for the functions of these proteins in the nucleus.
Collapse
Affiliation(s)
- Jeffrey M Verboon
- a Division of Basic Sciences; Fred Hutchinson Cancer Research Center ; Seattle , WA USA
| | - Bina Sugumar
- a Division of Basic Sciences; Fred Hutchinson Cancer Research Center ; Seattle , WA USA
| | - Susan M Parkhurst
- a Division of Basic Sciences; Fred Hutchinson Cancer Research Center ; Seattle , WA USA
| |
Collapse
|
53
|
Fourel L, Valat A, Faurobert E, Guillot R, Bourrin-Reynard I, Ren K, Lafanechère L, Planus E, Picart C, Albiges-Rizo C. β3 integrin-mediated spreading induced by matrix-bound BMP-2 controls Smad signaling in a stiffness-independent manner. J Cell Biol 2016; 212:693-706. [PMID: 26953352 PMCID: PMC4792076 DOI: 10.1083/jcb.201508018] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 02/09/2016] [Indexed: 12/31/2022] Open
Abstract
Matrix-bound BMP-2 is sufficient to induce β3 integrin–dependent, Cdc42/Src/FAK/ILK-mediated cell spreading by overriding the stiffness response through actin and adhesion site dynamics, showing BMP receptors and integrins work together to control signaling and tensional homeostasis, thereby coupling cell adhesion and fate commitment. Understanding how cells integrate multiple signaling pathways to achieve specific cell differentiation is a challenging question in cell biology. We have explored the physiological presentation of BMP-2 by using a biomaterial that harbors tunable mechanical properties to promote localized BMP-2 signaling. We show that matrix-bound BMP-2 is sufficient to induce β3 integrin–dependent C2C12 cell spreading by overriding the soft signal of the biomaterial and impacting actin organization and adhesion site dynamics. In turn, αvβ3 integrin is required to mediate BMP-2–induced Smad signaling through a Cdc42–Src–FAK–ILK pathway. β3 integrin regulates a multistep process to control first BMP-2 receptor activity and second the inhibitory role of GSK3 on Smad signaling. Overall, our results show that BMP receptors and β3 integrin work together to control Smad signaling and tensional homeostasis, thereby coupling cell adhesion and fate commitment, two fundamental aspects of developmental biology and regenerative medicine.
Collapse
Affiliation(s)
- Laure Fourel
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Centre National de la Recherche Scientifique, Equipe de Recherche Labellisée 5284, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France Centre National de la Recherche Scientifique UMR 5628, Laboratoire des Matériaux et du Génie Physique, Institute of Technology, 38016 Grenoble, France
| | - Anne Valat
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Centre National de la Recherche Scientifique, Equipe de Recherche Labellisée 5284, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France Centre National de la Recherche Scientifique UMR 5628, Laboratoire des Matériaux et du Génie Physique, Institute of Technology, 38016 Grenoble, France
| | - Eva Faurobert
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Centre National de la Recherche Scientifique, Equipe de Recherche Labellisée 5284, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France
| | - Raphael Guillot
- Centre National de la Recherche Scientifique UMR 5628, Laboratoire des Matériaux et du Génie Physique, Institute of Technology, 38016 Grenoble, France
| | - Ingrid Bourrin-Reynard
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Centre National de la Recherche Scientifique, Equipe de Recherche Labellisée 5284, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France
| | - Kefeng Ren
- Centre National de la Recherche Scientifique UMR 5628, Laboratoire des Matériaux et du Génie Physique, Institute of Technology, 38016 Grenoble, France
| | - Laurence Lafanechère
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France
| | - Emmanuelle Planus
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Centre National de la Recherche Scientifique, Equipe de Recherche Labellisée 5284, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France
| | - Catherine Picart
- Centre National de la Recherche Scientifique UMR 5628, Laboratoire des Matériaux et du Génie Physique, Institute of Technology, 38016 Grenoble, France
| | - Corinne Albiges-Rizo
- Institut National de la Santé et de la Recherche Médicale U823, Institut Albert Bonniot, 38042 Grenoble, France Centre National de la Recherche Scientifique, Equipe de Recherche Labellisée 5284, 38042 Grenoble, France Université Grenoble Alpes, 38041 Grenoble, France
| |
Collapse
|
54
|
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.
Collapse
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
| |
Collapse
|
55
|
Belin BJ, Lee T, Mullins RD. DNA damage induces nuclear actin filament assembly by Formin -2 and Spire-½ that promotes efficient DNA repair. [corrected]. eLife 2015; 4:e07735. [PMID: 26287480 PMCID: PMC4577826 DOI: 10.7554/elife.07735] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 08/12/2015] [Indexed: 01/20/2023] Open
Abstract
Actin filaments assemble inside the nucleus in response to multiple cellular perturbations, including heat shock, protein misfolding, integrin engagement, and serum stimulation. We find that DNA damage also generates nuclear actin filaments-detectable by phalloidin and live-cell actin probes-with three characteristic morphologies: (i) long, nucleoplasmic filaments; (ii) short, nucleolus-associated filaments; and (iii) dense, nucleoplasmic clusters. This DNA damage-induced nuclear actin assembly requires two biologically and physically linked nucleation factors: Formin-2 and Spire-1/Spire-2. Formin-2 accumulates in the nucleus after DNA damage, and depletion of either Formin-2 or actin's nuclear import factor, importin-9, increases the number of DNA double-strand breaks (DSBs), linking nuclear actin filaments to efficient DSB clearance. Nuclear actin filaments are also required for nuclear oxidation induced by acute genotoxic stress. Our results reveal a previously unknown role for nuclear actin filaments in DNA repair and identify the molecular mechanisms creating these nuclear filaments.
Collapse
Affiliation(s)
- Brittany J Belin
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
- Physiology Course, Marine Biological Laboratory, Woods Hole, United States
| | - Terri Lee
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - R Dyche Mullins
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
- Physiology Course, Marine Biological Laboratory, Woods Hole, United States
| |
Collapse
|
56
|
Tackling proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress. J Proteomics 2015; 122:73-85. [DOI: 10.1016/j.jprot.2015.03.029] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/14/2015] [Accepted: 03/27/2015] [Indexed: 12/27/2022]
|
57
|
Chang CY, Leu JD, Lee YJ. The actin depolymerizing factor (ADF)/cofilin signaling pathway and DNA damage responses in cancer. Int J Mol Sci 2015; 16:4095-120. [PMID: 25689427 PMCID: PMC4346946 DOI: 10.3390/ijms16024095] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 01/26/2015] [Accepted: 02/09/2015] [Indexed: 01/06/2023] Open
Abstract
The actin depolymerizing factor (ADF)/cofilin protein family is essential for actin dynamics, cell division, chemotaxis and tumor metastasis. Cofilin-1 (CFL-1) is a primary non-muscle isoform of the ADF/cofilin protein family accelerating the actin filamental turnover in vitro and in vivo. In response to environmental stimulation, CFL-1 enters the nucleus to regulate the actin dynamics. Although the purpose of this cytoplasm-nucleus transition remains unclear, it is speculated that the interaction between CFL-1 and DNA may influence various biological responses, including DNA damage repair. In this review, we will discuss the possible involvement of CFL-1 in DNA damage responses (DDR) induced by ionizing radiation (IR), and the implications for cancer radiotherapy.
Collapse
Affiliation(s)
- Chun-Yuan Chang
- Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 112, Taiwan.
| | - Jyh-Der Leu
- Division of Radiation Oncology, Taipei City Hospital RenAi Branch, Taipei 106, Taiwan.
| | - Yi-Jang Lee
- Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 112, Taiwan.
- Biophotonics & Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan.
| |
Collapse
|
58
|
Mardilovich K, Gabrielsen M, McGarry L, Orange C, Patel R, Shanks E, Edwards J, Olson MF. Elevated LIM kinase 1 in nonmetastatic prostate cancer reflects its role in facilitating androgen receptor nuclear translocation. Mol Cancer Ther 2015; 14:246-58. [PMID: 25344584 PMCID: PMC4297197 DOI: 10.1158/1535-7163.mct-14-0447] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Prostate cancer affects a large proportion of the male population, and is primarily driven by androgen receptor (AR) activity. First-line treatment typically consists of reducing AR signaling by hormone depletion, but resistance inevitably develops over time. One way to overcome this issue is to block AR function via alternative means, preferably by inhibiting protein targets that are more active in tumors than in normal tissue. By staining prostate cancer tumor sections, elevated LIM kinase 1 (LIMK1) expression and increased phosphorylation of its substrate Cofilin were found to be associated with poor outcome and reduced survival in patients with nonmetastatic prostate cancer. A LIMK-selective small molecule inhibitor (LIMKi) was used to determine whether targeted LIMK inhibition was a potential prostate cancer therapy. LIMKi reduced prostate cancer cell motility, as well as inhibiting proliferation and increasing apoptosis in androgen-dependent prostate cancer cells more effectively than in androgen-independent prostate cancer cells. LIMK inhibition blocked ligand-induced AR nuclear translocation, reduced AR protein stability and transcriptional activity, consistent with its effects on proliferation and survival acting via inhibition of AR activity. Furthermore, inhibition of LIMK activity increased αTubulin acetylation and decreased AR interactions with αTubulin, indicating that the role of LIMK in regulating microtubule dynamics contributes to AR function. These results indicate that LIMK inhibitors could be beneficial for the treatment of prostate cancer both by reducing nuclear AR translocation, leading to reduced proliferation and survival, and by inhibiting prostate cancer cell dissemination.
Collapse
Affiliation(s)
| | - Mads Gabrielsen
- Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Lynn McGarry
- Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Clare Orange
- Pathology Department, Division of Cancer Sciences and Molecular Pathology, Western Infirmary, University of Glasgow, Glasgow, United Kingdom
| | - Rachana Patel
- Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Emma Shanks
- Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Joanne Edwards
- Institute of Cancer Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Michael F Olson
- Beatson Institute for Cancer Research, Glasgow, United Kingdom.
| |
Collapse
|
59
|
Ulianov SV, Gavrilov AA, Razin SV. Nuclear Compartments, Genome Folding, and Enhancer-Promoter Communication. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:183-244. [DOI: 10.1016/bs.ircmb.2014.11.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
60
|
Li G, Chen H, Cheng L, Zhao R, Zhao J, Xu Y. Amyloid precursor-like protein 2 C-terminal fragments upregulate S100A9 gene and protein expression in BV2 cells. Neural Regen Res 2014; 9:1923-8. [PMID: 25558244 PMCID: PMC4281433 DOI: 10.4103/1673-5374.145362] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2014] [Indexed: 11/16/2022] Open
Abstract
The murine microglial cell line BV2 has neuroprotective effects, but is toxic to neurons by secreting inflammatory cytokines, and is an important target in the treatment of nerve inflammation and neurodegenerative diseases. In the present study, we observed the effects of transfecting three amyloid precursor-like protein 2 (APLP2) C-terminal fragments (CTFs; C57, C50 and C31) in the pEGFP-N1 vector on S100A9 expression in BV2 cells. Reverse transcription-PCR, western blot assay and immunocytochemistry revealed that S100A9 protein and mRNA expression was greater in BV2 cells after CTF transfection than after mock transfection with an empty vector. Furthermore, transfection of full-length APLP2-751 resulted in low levels of S100A9 protein expression. Our results show that APLP2-CTFs upregulate S100A9 protein and mRNA expression in BV2 cells, and identify a novel pathway involved in neuronal injury and apoptosis, and repair and protection in Alzheimer's disease.
Collapse
Affiliation(s)
- Guangzhe Li
- Department of Psychology, Yanbian Brain Hospital, Yanji, Jilin Province, China
| | - Hui Chen
- Department of Preventive Medicine, Medical College, Yanbian University, Yanji, Jilin Province, China
| | - Lin Cheng
- Department of Preventive Medicine, Medical College, Yanbian University, Yanji, Jilin Province, China
| | - Rongjie Zhao
- Department of Pharmacology, Mudanjiang Medical University, Mudanjiang, Heilongjiang, China
| | - Junchang Zhao
- Department of Pharmacology, Mudanjiang Medical University, Mudanjiang, Heilongjiang, China
| | - Yanji Xu
- Department of Preventive Medicine, Medical College, Yanbian University, Yanji, Jilin Province, China
| |
Collapse
|
61
|
Borkowski K, Wrzesinski K, Rogowska-Wrzesinska A, Audouze K, Bakke J, Petersen RK, Haj FG, Madsen L, Kristiansen K. Proteomic analysis of cAMP-mediated signaling during differentiation of 3 T3-L1 preadipocytes. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:2096-107. [PMID: 25152230 DOI: 10.1016/j.bbapap.2014.07.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 07/16/2014] [Accepted: 07/21/2014] [Indexed: 01/06/2023]
Abstract
Initiation of adipocyte differentiation is promoted by the synergistic action of insulin/insulin-like growth factor, glucocorticoids, and agents activating cAMP-dependent signaling. The action of cAMP is mediated via PKA and Epac, where at least part of the PKA function relates to strong repression of Rho kinase activity, whereas Epac counteracts the reduction in insulin/insulin-like growth factor signaling associated with complete repression of Rho kinase activity. However, detailed knowledge of the Epac-dependent branch and the interplay with PKA is still limited. In the present study, we present a comprehensive evaluation of Epac-mediated processes and their interplay with PKA during the initiation of 3 T3-L1 preadipocyte differentiation using a combination of proteomics, molecular approaches, and bioinformatics. Proteomic analyses revealed 7 proteins specifically regulated in response to Epac activation, 4 in response to PKA activation, and 11 in response to the combined activation of Epac and PKA during the initial phase of differentiation. Network analyses indicated that the identified proteins are involved in pathways of importance for glucose metabolism, inositol metabolism, and calcium-dependent signaling thereby adding a novel facet to our understanding of cAMP-mediated potentiation of adipocyte differentiation.
Collapse
Affiliation(s)
- Kamil Borkowski
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen DK-2200, Denmark
| | - Krzysztow Wrzesinski
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M DK-5230, Denmark
| | - Adelina Rogowska-Wrzesinska
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M DK-5230, Denmark
| | - Karine Audouze
- Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark
| | - Jesse Bakke
- Department of Nutrition, University of California Davis, Davis, CA 95616, USA
| | - Rasmus Koefoed Petersen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen DK-2200, Denmark
| | - Fawaz G Haj
- Department of Nutrition, University of California Davis, Davis, CA 95616, USA; Department of Internal Medicine, University of California Davis, Sacramento, CA 95817, USA
| | - Lise Madsen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen DK-2200, Denmark; National Institute of Nutrition and Seafood Research (NIFES), Bergen N-5817, Norway.
| | - Karsten Kristiansen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen DK-2200, Denmark.
| |
Collapse
|
62
|
Hendzel MJ. The F-act's of nuclear actin. Curr Opin Cell Biol 2014; 28:84-9. [DOI: 10.1016/j.ceb.2014.04.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 03/24/2014] [Accepted: 04/11/2014] [Indexed: 10/25/2022]
|
63
|
Calabrese B, Saffin JM, Halpain S. Activity-dependent dendritic spine shrinkage and growth involve downregulation of cofilin via distinct mechanisms. PLoS One 2014; 9:e94787. [PMID: 24740405 PMCID: PMC3989342 DOI: 10.1371/journal.pone.0094787] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 03/19/2014] [Indexed: 01/09/2023] Open
Abstract
A current model posits that cofilin-dependent actin severing negatively impacts dendritic spine volume. Studies suggested that increased cofilin activity underlies activity-dependent spine shrinkage, and that reduced cofilin activity induces activity-dependent spine growth. We suggest instead that both types of structural plasticity correlate with decreased cofilin activity. However, the mechanism of inhibition determines the outcome for spine morphology. RNAi in rat hippocampal cultures demonstrates that cofilin is essential for normal spine maintenance. Cofilin-F-actin binding and filament barbed-end production decrease during the early phase of activity-dependent spine shrinkage; cofilin concentration also decreases. Inhibition of the cathepsin B/L family of proteases prevents both cofilin loss and spine shrinkage. Conversely, during activity-dependent spine growth, LIM kinase stimulates cofilin phosphorylation, which activates phospholipase D-1 to promote actin polymerization. These results implicate novel molecular mechanisms and prompt a revision of the current model for how cofilin functions in activity-dependent structural plasticity.
Collapse
Affiliation(s)
- Barbara Calabrese
- Division of Biological Sciences, and Sanford Consortium for Regenerative Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Jean-Michel Saffin
- Division of Biological Sciences, and Sanford Consortium for Regenerative Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Shelley Halpain
- Division of Biological Sciences, and Sanford Consortium for Regenerative Medicine, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
| |
Collapse
|
64
|
Rajakylä EK, Vartiainen MK. Rho, nuclear actin, and actin-binding proteins in the regulation of transcription and gene expression. Small GTPases 2014; 5:e27539. [PMID: 24603113 DOI: 10.4161/sgtp.27539] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Actin cytoskeleton is one of the main targets of Rho GTPases, which act as molecular switches on many signaling pathways. During the past decade, actin has emerged as an important regulator of gene expression. Nuclear actin plays a key role in transcription, chromatin remodeling, and pre-mRNA processing. In addition, the "status" of the actin cytoskeleton is used as a signaling intermediate by at least the MKL1-SRF and Hippo-pathways, which culminate in the transcriptional regulation of cytoskeletal and growth-promoting genes, respectively. Rho GTPases may therefore regulate gene expression by controlling either cytoplasmic or nuclear actin dynamics. Although the regulation of nuclear actin polymerization is still poorly understood, many actin-binding proteins, which are downstream effectors of Rho, are found in the nuclear compartment. In this review, we discuss the possible mechanisms and key proteins that may mediate the transcriptional regulation by Rho GTPases through actin.
Collapse
Affiliation(s)
- Eeva Kaisa Rajakylä
- Program in Cell and Molecular Biology; Institute of Biotechnology; University of Helsinki; Helsinki, Finland
| | - Maria K Vartiainen
- Program in Cell and Molecular Biology; Institute of Biotechnology; University of Helsinki; Helsinki, Finland
| |
Collapse
|
65
|
The transcription factor serum response factor stimulates axon regeneration through cytoplasmic localization and cofilin interaction. J Neurosci 2014; 33:18836-48. [PMID: 24285890 DOI: 10.1523/jneurosci.3029-13.2013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Axonal injury generates growth inert retraction bulbs with dynamic cytoskeletal properties that are severely compromised. Conversion of "frozen" retraction bulbs into actively progressing growth cones is a major aim in axon regeneration. Here we report that murine serum response factor (SRF), a gene regulator linked to the actin cytoskeleton, modulates growth cone actin dynamics during axon regeneration. In regeneration-competent facial motoneurons, Srf deletion inhibited axonal regeneration. In wild-type mice after nerve injury, SRF translocated from the nucleus to the cytoplasm, suggesting a cytoplasmic SRF function in axonal regeneration. Indeed, adenoviral overexpression of cytoplasmic SRF (SRF-ΔNLS-GFP) stimulated axonal sprouting and facial nerve regeneration in vivo. In primary central and peripheral neurons, SRF-ΔNLS-GFP stimulated neurite outgrowth, branch formation, and growth cone morphology. Furthermore, we uncovered a link between SRF and the actin-severing factor cofilin during axonal regeneration in vivo. Facial nerve axotomy increased the total cofilin abundance and also nuclear localization of phosphorylated cofilin in a subpopulation of lesioned motoneurons. This cytoplasmic-to-nucleus translocation of P-cofilin upon axotomy was reduced in motoneurons expressing SRF-ΔNLS-GFP. Finally, we demonstrate that cytoplasmic SRF and cofilin formed a reciprocal regulatory unit. Overexpression of cytoplasmic SRF reduced cofilin phosphorylation and vice versa: overexpression of cofilin inhibited SRF phosphorylation. Therefore, a regulatory loop consisting of SRF and cofilin might take part in reactivating actin dynamics in growth-inert retraction bulbs and facilitating axon regeneration.
Collapse
|
66
|
Munsie LN, Truant R. The role of the cofilin-actin rod stress response in neurodegenerative diseases uncovers potential new drug targets. BIOARCHITECTURE 2014; 2:204-8. [PMID: 23267414 PMCID: PMC3527314 DOI: 10.4161/bioa.22549] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The cofilin-actin rod stress response is an actin cytoskeletal dynamic arrest that occurs in cells under a variety of stress conditions. Upon stress, the rapidly activated cofilin saturates actin filaments causing them to bundle into rod structures in either the nucleus or cytoplasm, halting actin polymerization and thus freeing ATP. Importantly, these rods dissociate quickly following relief of the transient stress. The rods form inappropriately in neurons involved in the progression of Alzheimer disease (AD) and we have linked dysfunctional dynamics of the nuclear rod response to Huntington disease (HD). Cofilin levels are also perturbed in Parkinson disease (PD), and profilin, an actin binding protein with opposite action to cofilin, is mutated in Amyotrophic Lateral Sclerosis (ALS). The persistence of the rods post-stress suggests that critical molecular switches to turn this response both on and off are being affected in neurodegeneration. We have recently shown that the cofilin protein is regulated by highly conserved nuclear import and export signals and that these signals are required to be functional for an appropriate rod formation during stress. The ability of cofilin to form rods is required in a cell culture model for cells to be resistant to apoptosis under stress conditions, indicating that a normal cofilin-actin rod response is likely integral to proper cell health in higher order organisms. Here we hypothesize on the potential physiological function of nuclear cofilin-actin rods and why the dysregulation of this response could lead to the selective vulnerability of the most susceptible populations of cells in HD. We further suggest that learning more about this cytoskeletal cell stress response will open up new avenues for drug target discovery in neurodegenerative disorders.
Collapse
Affiliation(s)
- Lise N Munsie
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Canada
| | | |
Collapse
|
67
|
Mi J, Shaw AE, Pak CW, Walsh KP, Minamide LS, Bernstein BW, Kuhn TB, Bamburg JR. A genetically encoded reporter for real-time imaging of cofilin-actin rods in living neurons. PLoS One 2013; 8:e83609. [PMID: 24391794 PMCID: PMC3877059 DOI: 10.1371/journal.pone.0083609] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 11/05/2013] [Indexed: 01/18/2023] Open
Abstract
Filament bundles (rods) of cofilin and actin (1:1) form in neurites of stressed neurons where they inhibit synaptic function. Live-cell imaging of rod formation is hampered by the fact that overexpression of a chimera of wild type cofilin with a fluorescent protein causes formation of spontaneous and persistent rods, which is exacerbated by the photostress of imaging. The study of rod induction in living cells calls for a rod reporter that does not cause spontaneous rods. From a study in which single cofilin surface residues were mutated, we identified a mutant, cofilinR21Q, which when fused with monomeric Red Fluorescent Protein (mRFP) and expressed several fold above endogenous cofilin, does not induce spontaneous rods even during the photostress of imaging. CofilinR21Q-mRFP only incorporates into rods when they form from endogenous proteins in stressed cells. In neurons, cofilinR21Q-mRFP reports on rods formed from endogenous cofilin and induced by all modes tested thus far. Rods have a half-life of 30-60 min upon removal of the inducer. Vesicle transport in neurites is arrested upon treatments that form rods and recovers as rods disappear. CofilinR21Q-mRFP is a genetically encoded rod reporter that is useful in live cell imaging studies of induced rod formation, including rod dynamics, and kinetics of rod elimination.
Collapse
Affiliation(s)
- Jianjie Mi
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Alisa E. Shaw
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Chi W. Pak
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Keifer P. Walsh
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Laurie S. Minamide
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Barbara W. Bernstein
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Thomas B. Kuhn
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
- Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, Alaska, United States of America
| | - James R. Bamburg
- Department of Biochemistry and Molecular Biology, and Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| |
Collapse
|
68
|
Analysis of nuclear actin by overexpression of wild-type and actin mutant proteins. Histochem Cell Biol 2013; 141:123-35. [PMID: 24091797 DOI: 10.1007/s00418-013-1151-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2013] [Indexed: 01/14/2023]
Abstract
Compared to the cytoplasmic F-actin abundance in cells, nuclear F-actin levels are generally quite low. However, nuclear actin is present in certain cell types including oocytes and under certain cellular conditions including stress or serum stimulation. Currently, the architecture and polymerization status of nuclear actin networks has not been analyzed in great detail. In this study, we investigated the architecture and functions of such nuclear actin networks. We generated nuclear actin polymers by overexpression of actin proteins fused to a nuclear localization signal (NLS). Raising nuclear abundance of a NLS wild-type actin, we observed phalloidin- and LifeAct-positive actin bundles forming a nuclear cytoskeletal network consisting of curved F-actin. In contrast, a polymer-stabilizing actin mutant (NLS-G15S-actin) deficient in interacting with the actin-binding protein cofilin generated a nuclear actin network reminiscent of straight stress fiber-like microfilaments in the cytoplasm. We provide a first electron microscopic description of such nuclear actin polymers suggesting bundling of actin filaments. Employing different cell types from various species including neurons, we show that the morphology of and potential to generate nuclear actin are conserved. Finally, we demonstrate that nuclear actin affects cell function including morphology, serum response factor-mediated gene expression, and herpes simplex virus infection. Our data suggest that actin is able to form filamentous structures inside the nucleus, which share architectural and functional similarities with the cytoplasmic F-actin.
Collapse
|
69
|
Klejnot M, Gabrielsen M, Cameron J, Mleczak A, Talapatra SK, Kozielski F, Pannifer A, Olson MF. Analysis of the human cofilin 1 structure reveals conformational changes required for actin binding. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:1780-8. [PMID: 23999301 DOI: 10.1107/s0907444913014418] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 05/24/2013] [Indexed: 11/10/2022]
Abstract
The actin cytoskeleton is the chassis that gives a cell its shape and structure, and supplies the power for numerous dynamic processes including motility, endocytosis, intracellular transport and division. To perform these activities, the cytoskeleton undergoes constant remodelling and reorganization. One of the major actin-remodelling families are the cofilin proteins, made up of cofilin 1, cofilin 2 and actin-depolymerizing factor (ADF), which sever aged ADP-associated actin filaments to reduce filament length and provide new potential nucleation sites. Despite the significant interest in cofilin as a central node in actin-cytoskeleton dynamics, to date the only forms of cofilin for which crystal structures have been solved are from the yeast, Chromalveolata and plant kingdoms; none have previously been reported for an animal cofilin protein. Two distinct regions in animal cofilin are significantly larger than in the forms previously crystallized, suggesting that they would be uniquely organized. Therefore, it was sought to determine the structure of human cofilin 1 by X-ray crystallography to elucidate how it could interact with and regulate dynamic actin-cytoskeletal structures. Although wild-type human cofilin 1 proved to be recalcitrant, a C147A point mutant yielded crystals that diffracted to 2.8 Å resolution. These studies revealed how the actin-binding helix undergoes a conformational change that increases the number of potential hydrogen bonds available for substrate binding.
Collapse
Affiliation(s)
- Marta Klejnot
- Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Glasgow G61 1BD, Scotland
| | | | | | | | | | | | | | | |
Collapse
|
70
|
Abstract
In the cytoplasm, actin filaments form crosslinked networks that enable eukaryotic cells to transport cargo, change shape, and move. Actin is also present in the nucleus but, in this compartment, its functions are more cryptic and controversial. If we distill the substantial literature on nuclear actin down to its essentials, we find four, recurring, and more-or-less independent, claims: (1) crosslinked networks of conventional actin filaments span the nucleus and help maintain its structure and organize its contents; (2) assembly or contraction of filaments regulates specific nuclear events; (3) actin monomers moonlight as subunits of chromatin remodeling complexes, independent of their ability to form filaments; and (4) modified actin monomers or oligomers, structurally distinct from canonical, cytoskeletal filaments, mediate nuclear events by unknown mechanisms. We discuss the evidence underlying these claims and as well as their strengths and weaknesses. Next, we describe our recent work, in which we built probes specific for nuclear actin and used them to describe the form and distribution of actin in somatic cell nuclei. Finally, we discuss how different forms of nuclear actin may play different roles in different cell types and physiological contexts.
Collapse
Affiliation(s)
- Brittany J Belin
- Cellular and Molecular Pharmacology; University of California; San Francisco, CA USA
| | | |
Collapse
|
71
|
Bravo-Cordero JJ, Magalhaes MAO, Eddy RJ, Hodgson L, Condeelis J. Functions of cofilin in cell locomotion and invasion. Nat Rev Mol Cell Biol 2013; 14:405-15. [PMID: 23778968 DOI: 10.1038/nrm3609] [Citation(s) in RCA: 367] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recently, a consensus has emerged that cofilin severing activity can generate free actin filament ends that are accessible for F-actin polymerization and depolymerization without changing the rate of G-actin association and dissociation at either filament end. The structural basis of actin filament severing by cofilin is now better understood. These results have been integrated with recently discovered mechanisms for cofilin activation in migrating cells, which led to new models for cofilin function that provide insights into how cofilin regulation determines the temporal and spatial control of cell behaviour.
Collapse
Affiliation(s)
- Jose Javier Bravo-Cordero
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
| | | | | | | | | |
Collapse
|