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Ventura Santos C, Rogers SL, Carter AP. CryoET shows cofilactin filaments inside the microtubule lumen. EMBO Rep 2023; 24:e57264. [PMID: 37702953 PMCID: PMC10626427 DOI: 10.15252/embr.202357264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 08/25/2023] [Accepted: 08/30/2023] [Indexed: 09/14/2023] Open
Abstract
Cytoplasmic microtubules are tubular polymers that can harbor small proteins or filaments inside their lumen. The identities of these objects and mechanisms for their accumulation have not been conclusively established. Here, we used cryogenic electron tomography of Drosophila S2 cell protrusions and found filaments inside the microtubule lumen, which resemble those reported recently in human HAP1 cells. The frequency of these filaments increased upon inhibition of the sarco/endoplasmic reticulum Ca2+ ATPase with the small molecule drug thapsigargin. Subtomogram averaging showed that the luminal filaments adopt a helical structure reminiscent of cofilin-bound actin (cofilactin). Consistent with this, we observed cofilin dephosphorylation, an activating modification, in cells under the same conditions that increased luminal filament occurrence. Furthermore, RNA interference knock-down of cofilin reduced the frequency of luminal filaments with cofilactin morphology. These results suggest that cofilin activation stimulates its accumulation on actin filaments inside the microtubule lumen.
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Affiliation(s)
| | - Stephen L Rogers
- Department of Biology and Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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2
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Takayama K, Matsuda K, Abe H. Formation of actin-cofilin rods by depletion forces. Biochem Biophys Res Commun 2022; 626:200-204. [PMID: 35994830 DOI: 10.1016/j.bbrc.2022.08.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 07/28/2022] [Accepted: 08/08/2022] [Indexed: 11/02/2022]
Abstract
Various stress conditions induce the formation of actin-cofilin rods in either the nucleus or the cytoplasm, although the mechanism of rod formation is unclear. In this study, we constituted actin-cofilin rods using purified actin, cofilin and actin interacting protein 1 (AIP1) in the presence of a physiological buffer containing a crowding agent, 0.8% methylcellulose (MC), which led to bundled actin filaments formed by depletion forces. Most of the F-actin bundles formed with methylcellulose were linear, whereas cofilin-bound F-actin bundles often had bent, looped, and often ring-like shapes. Increasing the amount of AIP1 shortened actin-cofilin bundles into rod-like bundles with tapering at both ends. As much shorter actin-cofilin filaments were formed in the presence of AIP1 before MC was added to the mixture, the rod-like bundle might be a mass of those short filaments. Furthermore, the small rods fused with each other to become larger rods, indicating that these rods were anisotropic liquid droplets. Several minutes after the addition of MC to the F-actin-cofilin-AIP1 mixture, we observed some long bundles in which the thick and thin parts appear alternately, reminiscent of a Plateau-Rayleigh instability observed in fluid columns. Simultaneously, we found images in which thin parts were interrupted, but the thick parts were arranged in a row in the longitudinal direction. These structures were also observed in cytoplasmic actin-cofilin rods in cells overexpressing cofilin-GFP, suggesting that cytoplasmic actin-cofilin rods have the same structure formation process as the rods reconstituted in vitro.
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Affiliation(s)
- Kohki Takayama
- Department of Biology, Graduate School of Science and Engineering, Chiba University, Chiba, 263-8522, Japan
| | - Kota Matsuda
- Department of Biology, Graduate School of Science and Engineering, Chiba University, Chiba, 263-8522, Japan
| | - Hiroshi Abe
- Department of Biology, Graduate School of Science and Engineering, Chiba University, Chiba, 263-8522, Japan; Department of Biology, Graduate School of Science, Chiba University, Chiba, 263-8522, Japan.
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3
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Lapeña-Luzón T, Rodríguez LR, Beltran-Beltran V, Benetó N, Pallardó FV, Gonzalez-Cabo P. Cofilin and Neurodegeneration: New Functions for an Old but Gold Protein. Brain Sci 2021; 11:brainsci11070954. [PMID: 34356188 PMCID: PMC8303701 DOI: 10.3390/brainsci11070954] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/12/2021] [Accepted: 07/16/2021] [Indexed: 12/11/2022] Open
Abstract
Cofilin is an actin-binding protein that plays a major role in the regulation of actin dynamics, an essential cellular process. This protein has emerged as a crucial molecule for functions of the nervous system including motility and guidance of the neuronal growth cone, dendritic spine organization, axonal branching, and synaptic signalling. Recently, other important functions in cell biology such as apoptosis or the control of mitochondrial function have been attributed to cofilin. Moreover, novel mechanisms of cofilin function regulation have also been described. The activity of cofilin is controlled by complex regulatory mechanisms, with phosphorylation being the most important, since the addition of a phosphate group to cofilin renders it inactive. Due to its participation in a wide variety of key processes in the cell, cofilin has been related to a great variety of pathologies, among which neurodegenerative diseases have attracted great interest. In this review, we summarized the functions of cofilin and its regulation, emphasizing how defects in these processes have been related to different neurodegenerative diseases.
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Affiliation(s)
- Tamara Lapeña-Luzón
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, 46010 Valencia, Spain; (T.L.-L.); (L.R.R.); (V.B.-B.); (N.B.); (F.V.P.)
- Biomedical Research Institute INCLIVA, 46010 Valencia, Spain
- CIBER de Enfermedades Raras (CIBERER), 46010 Valencia, Spain
| | - Laura R. Rodríguez
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, 46010 Valencia, Spain; (T.L.-L.); (L.R.R.); (V.B.-B.); (N.B.); (F.V.P.)
- Biomedical Research Institute INCLIVA, 46010 Valencia, Spain
- CIBER de Enfermedades Raras (CIBERER), 46010 Valencia, Spain
| | - Vicent Beltran-Beltran
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, 46010 Valencia, Spain; (T.L.-L.); (L.R.R.); (V.B.-B.); (N.B.); (F.V.P.)
| | - Noelia Benetó
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, 46010 Valencia, Spain; (T.L.-L.); (L.R.R.); (V.B.-B.); (N.B.); (F.V.P.)
- Biomedical Research Institute INCLIVA, 46010 Valencia, Spain
- CIBER de Enfermedades Raras (CIBERER), 46010 Valencia, Spain
| | - Federico V. Pallardó
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, 46010 Valencia, Spain; (T.L.-L.); (L.R.R.); (V.B.-B.); (N.B.); (F.V.P.)
- Biomedical Research Institute INCLIVA, 46010 Valencia, Spain
- CIBER de Enfermedades Raras (CIBERER), 46010 Valencia, Spain
| | - Pilar Gonzalez-Cabo
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, 46010 Valencia, Spain; (T.L.-L.); (L.R.R.); (V.B.-B.); (N.B.); (F.V.P.)
- Biomedical Research Institute INCLIVA, 46010 Valencia, Spain
- CIBER de Enfermedades Raras (CIBERER), 46010 Valencia, Spain
- Correspondence:
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4
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Walter LM, Rademacher S, Pich A, Claus P. Profilin2 regulates actin rod assembly in neuronal cells. Sci Rep 2021; 11:10287. [PMID: 33986363 PMCID: PMC8119500 DOI: 10.1038/s41598-021-89397-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2021] [Indexed: 12/13/2022] Open
Abstract
Nuclear and cytoplasmic actin-cofilin rods are formed transiently under stress conditions to reduce actin filament turnover and ATP hydrolysis. The persistence of these structures has been implicated in disease pathology of several neurological disorders. Recently, the presence of actin rods has been discovered in Spinal Muscular Atrophy (SMA), a neurodegenerative disease affecting predominantly motoneurons leading to muscle weakness and atrophy. This finding underlined the importance of dysregulated actin dynamics in motoneuron loss in SMA. In this study, we characterized actin rods formed in a SMA cell culture model analyzing their composition by LC–MS-based proteomics. Besides actin and cofilin, we identified proteins involved in processes such as ubiquitination, translation or protein folding to be bound to actin rods. This suggests their sequestration to actin rods, thus impairing important cellular functions. Moreover, we showed the involvement of the cytoskeletal protein profilin2 and its upstream effectors RhoA/ROCK in actin rod assembly in SMA. These findings implicate that the formation of actin rods exerts detrimental effects on motoneuron homeostasis by affecting actin dynamics and disturbing essential cellular pathways.
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Affiliation(s)
- Lisa Marie Walter
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany
| | - Sebastian Rademacher
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,Center for Systems Neuroscience, Hannover, Germany.,Institute of Biochemistry, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Andreas Pich
- Institute of Toxicology and Core Unit Proteomics, Hannover Medical School, Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany. .,Center for Systems Neuroscience, Hannover, Germany.
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Cofilin-Mediated Actin Stress Response Is Maladaptive in Heat-Stressed Embryos. Cell Rep 2020; 26:3493-3501.e4. [PMID: 30917306 PMCID: PMC6447309 DOI: 10.1016/j.celrep.2019.02.092] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 01/22/2019] [Accepted: 02/21/2019] [Indexed: 01/04/2023] Open
Abstract
Environmental stress threatens the fidelity of embryonic morphogenesis. Heat, for example, is a teratogen. Yet how heat affects morphogenesis is poorly understood. Here, we identify a heat-inducible actin stress response (ASR) in Drosophila embryos that is mediated by the activation of the actin regulator Cofilin. Similar to ASR in adult mammalian cells, heat stress in fly embryos triggers the assembly of intra-nuclear actin rods. Rods measure up to a few microns in length, and their assembly depends on elevated free nuclear actin concentration and Cofilin. Outside the nucleus, heat stress causes Cofilin-dependent destabilization of filamentous actin (F-actin) in actomyosin networks required for morphogenesis. F-actin destabilization increases the chance of morphogenesis mistakes. Blocking the ASR by reducing Cofilin dosage improves the viability of heat-stressed embryos. However, improved viability correlates with restoring F-actin stability, not rescuing morphogenesis. Thus, ASR endangers embryos, perhaps by shifting actin from cytoplasmic filaments to an elevated nuclear pool. Figard et al. show that heat stress induces an actin stress response (ASR) in early Drosophila embryos. This ASR is mediated by a heat-induced increase in Cofilin activity. Increased Cofilin activity destabilizes F-actin structures required for morphogenesis. In addition, the Cofilin-mediated ASR reduces embryo viability.
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The Role of Actin Dynamics and Actin-Binding Proteins Expression in Epithelial-to-Mesenchymal Transition and Its Association with Cancer Progression and Evaluation of Possible Therapeutic Targets. BIOMED RESEARCH INTERNATIONAL 2018; 2018:4578373. [PMID: 29581975 PMCID: PMC5822767 DOI: 10.1155/2018/4578373] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/19/2017] [Indexed: 12/21/2022]
Abstract
Metastasis causes death of 90% of cancer patients, so it is the most significant issue associated with cancer disease. Thus, it is no surprise that many researchers are trying to develop drugs targeting or preventing them. The secondary tumour site formation is closely related to phenomena like epithelial-to-mesenchymal and its reverse, mesenchymal-to-epithelial transition. The change of the cells' phenotype to mesenchymal involves the acquisition of migratory potential. Cancer cells movement is possible due to the development of invasive structures like invadopodia, lamellipodia, and filopodia. These changes are dependent on the reorganization of the actin cytoskeleton. In turn, the polymerization and depolymerization of actin are controlled by actin-binding proteins. In many tumour cells, the actin and actin-associated proteins are accumulated in the cell nucleus, suggesting that it may also affect the progression of cancer by regulating gene expression. Once the cancer cell reaches a new habitat it again acquires epithelial features and thus proliferative activity. Targeting of epithelial-to-mesenchymal or/and mesenchymal-to-epithelial transitions through regulation of their main components expression may be a potential solution to the problem of metastasis. This work focuses on the role of these processes in tumour progression and the assessment of therapeutic potential of agents targeting them.
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7
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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.
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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.
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8
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Tweedell R, Tao D, Dinglasan RR. The cellular and proteomic response of primary and immortalized murine Kupffer cells following immune stimulation diverges from that of monocyte-derived macrophages. Proteomics 2014; 15:545-53. [PMID: 25266554 DOI: 10.1002/pmic.201400216] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 08/25/2014] [Accepted: 09/25/2014] [Indexed: 12/23/2022]
Abstract
Kupffer cells (KCs) are the first line of defense in the liver against pathogens, yet several microbes successfully target the liver, bypass immune surveillance, and effectively develop in this tissue. Our current, albeit poor, understanding of KC-pathogen interactions has been largely achieved through the study of primary cells, requiring isolation from large numbers of animals. To facilitate the study of KC biology, an immortalized rat KC line 1, RKC1, was developed. We performed a comparative global proteomic analysis of RKC1 and primary rat KCs (PRKC) to characterize their respective responses to lipopolysaccharide-mediated immune stimulation. We identified patent differences in the proteomic response profile of RKC1 and PRKC to lipopolysaccharide. We observed that PRKC upregulated more immune function pathways and exhibited marked changes in cellular morphology following stimulation. We consequently analyzed the cytoskeletal signaling pathways of these cells in light of the fact that macrophages are known to induce cytoskeletal changes in response to pathogens. Our findings suggest that KCs respond differently to inflammatory stimulus than do monocyte-derived macrophages, and such data may provide insight into how pathogens, such as the malaria parasite, may have evolved mechanisms of liver entry through KCs without detection.
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Affiliation(s)
- Rebecca Tweedell
- W. Harry Feinstone Department of Molecular Microbiology & Immunology and the Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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9
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Chen Q, Courtemanche N, Pollard TD. Aip1 promotes actin filament severing by cofilin and regulates constriction of the cytokinetic contractile ring. J Biol Chem 2014; 290:2289-300. [PMID: 25451933 DOI: 10.1074/jbc.m114.612978] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aip1 (actin interacting protein 1) is ubiquitous in eukaryotic organisms, where it cooperates with cofilin to disassemble actin filaments, but neither its mechanism of action nor its biological functions have been clear. We purified both fission yeast and human Aip1 and investigated their biochemical activities with or without cofilin. Both types of Aip1 bind actin filaments with micromolar affinities and weakly nucleate actin polymerization. Aip1 increases up to 12-fold the rate that high concentrations of yeast or human cofilin sever actin filaments, most likely by competing with cofilin for binding to the side of actin filaments, reducing the occupancy of the filaments by cofilin to a range favorable for severing. Aip1 does not cap the barbed ends of filaments severed by cofilin. Fission yeast lacking Aip1 are viable and assemble cytokinetic contractile rings normally, but rings in these Δaip1 cells accumulate 30% less myosin II. Further, these mutant cells initiate the ingression of cleavage furrows earlier than normal, shortening the stage of cytokinetic ring maturation by 50%. The Δaip1 mutation has negative genetic interactions with deletion mutations of both capping protein subunits and cofilin mutations with severing defects, but no genetic interaction with deletion of coronin.
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Affiliation(s)
- Qian Chen
- From the Departments of Molecular Cellular and Developmental Biology
| | | | - Thomas D Pollard
- From the Departments of Molecular Cellular and Developmental Biology, Molecular Biophysics and Biochemistry, and Cell Biology Yale University, New Haven, Connecticut 06520-8103
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10
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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.
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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
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11
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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.
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Affiliation(s)
- Lise N Munsie
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Canada
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12
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Goyal P, Pandey D, Brünnert D, Hammer E, Zygmunt M, Siess W. Cofilin oligomer formation occurs in vivo and is regulated by cofilin phosphorylation. PLoS One 2013; 8:e71769. [PMID: 23951242 PMCID: PMC3738525 DOI: 10.1371/journal.pone.0071769] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 07/08/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND ADF/cofilin proteins are key regulators of actin dynamics. Their function is inhibited by LIMK-mediated phosphorylation at Ser-3. Previous in vitro studies have shown that dependent on its concentration, cofilin either depolymerizes F-actin (at low cofilin concentrations) or promotes actin polymerization (at high cofilin concentrations). METHODOLOGY/PRINCIPAL FINDINGS We found that after in vivo cross-linking with different probes, a cofilin oligomer (65 kDa) could be detected in platelets and endothelial cells. The cofilin oligomer did not contain actin. Notably, ADF that only depolymerizes F-actin was present mainly in monomeric form. Furthermore, we found that formation of the cofilin oligomer is regulated by Ser-3 cofilin phosphorylation. Cofilin but not phosphorylated cofilin was present in the endogenous cofilin oligomer. In vitro, formation of cofilin oligomers was drastically reduced after phosphorylation by LIMK2. In endothelial cells, LIMK-mediated cofilin phosphorylation after thrombin-stimulation of EGFP- or DsRed2-tagged cofilin transfected cells reduced cofilin aggregate formation, whereas inhibition of cofilin phosphorylation after Rho-kinase inhibitor (Y27632) treatment of endothelial cells promoted formation of cofilin aggregates. In platelets, cofilin dephosphorylation after thrombin-stimulation and Y27632 treatment led to an increased formation of the cofilin oligomer. CONCLUSION/SIGNIFICANCE Based on our results, we propose that an equilibrium exists between the monomeric and oligomeric forms of cofilin in intact cells that is regulated by cofilin phosphorylation. Cofilin phosphorylation at Ser-3 may induce conformational changes on the protein-protein interacting surface of the cofilin oligomer, thereby preventing and/or disrupting cofilin oligomer formation. Cofilin oligomerization might explain the dual action of cofilin on actin dynamics in vivo.
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Affiliation(s)
- Pankaj Goyal
- Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Klinikum Innenstadt, Universität München, München, Germany.
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Rosário M, Schuster S, Jüttner R, Parthasarathy S, Tarabykin V, Birchmeier W. Neocortical dendritic complexity is controlled during development by NOMA-GAP-dependent inhibition of Cdc42 and activation of cofilin. Genes Dev 2012; 26:1743-57. [PMID: 22810622 DOI: 10.1101/gad.191593.112] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Neocortical neurons have highly branched dendritic trees that are essential for their function. Indeed, defects in dendritic arborization are associated with human neurodevelopmental disorders. The molecular mechanisms regulating dendritic arbor complexity, however, are still poorly understood. Here, we uncover the molecular basis for the regulation of dendritic branching during cortical development. We show that during development, dendritic branching requires post-mitotic suppression of the RhoGTPase Cdc42. By generating genetically modified mice, we demonstrate that this is catalyzed in vivo by the novel Cdc42-GAP NOMA-GAP. Loss of NOMA-GAP leads to decreased neocortical volume, associated specifically with profound oversimplification of cortical dendritic arborization and hyperactivation of Cdc42. Remarkably, dendritic complexity and cortical thickness can be partially restored by genetic reduction of post-mitotic Cdc42 levels. Furthermore, we identify the actin regulator cofilin as a key regulator of dendritic complexity in vivo. Cofilin activation during late cortical development depends on NOMA-GAP expression and subsequent inhibition of Cdc42. Strikingly, in utero expression of active cofilin is sufficient to restore postnatal dendritic complexity in NOMA-GAP-deficient animals. Our findings define a novel cell-intrinsic mechanism to regulate dendritic branching and thus neuronal complexity in the cerebral cortex.
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Affiliation(s)
- Marta Rosário
- Neurocure Excellence Cluster, Institute of Cell and Neurobiology, Charité Universitätsmedizin Berlin, Germany.
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14
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Munsie L, Caron N, Atwal RS, Marsden I, Wild EJ, Bamburg JR, Tabrizi SJ, Truant R. Mutant huntingtin causes defective actin remodeling during stress: defining a new role for transglutaminase 2 in neurodegenerative disease. Hum Mol Genet 2011; 20:1937-51. [PMID: 21355047 PMCID: PMC3080606 DOI: 10.1093/hmg/ddr075] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Huntington's disease (HD) is caused by an expanded CAG tract in the Interesting transcript 15 (IT15) gene encoding the 350 kDa huntingtin protein. Cellular stresses can trigger the release of huntingtin from the endoplasmic reticulum, allowing huntingtin nuclear entry. Here, we show that endogenous, full-length huntingtin localizes to nuclear cofilin–actin rods during stress and is required for the proper stress response involving actin remodeling. Mutant huntingtin induces a dominant, persistent nuclear rod phenotype similar to that described in Alzheimer's disease for cytoplasmic cofilin–actin rods. Using live cell temporal studies, we show that this stress response is similarly impaired when mutant huntingtin is present, or when normal huntingtin levels are reduced. In clinical lymphocyte samples from HD patients, we have quantitatively detected cross-linked complexes of actin and cofilin with complex formation varying in correlation with disease progression. By live cell fluorescence lifetime imaging measurement–Förster resonant energy transfer studies and western blot assays, we quantitatively observed that stress-activated tissue transglutaminase 2 (TG2) is responsible for the actin–cofilin covalent cross-linking observed in HD. These data support a direct role for huntingtin in nuclear actin re-organization, and describe a new pathogenic mechanism for aberrant TG2 enzymatic hyperactivity in neurodegenerative diseases.
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Affiliation(s)
- Lise Munsie
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N3Z5
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15
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Kandasamy MK, McKinney EC, Meagher RB. Differential sublocalization of actin variants within the nucleus. Cytoskeleton (Hoboken) 2011; 67:729-43. [PMID: 20862689 DOI: 10.1002/cm.20484] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Conventional actin has been implicated in various nuclear processes including chromatin remodeling, transcription, nuclear transport, and overall nuclear structure. Moreover, actin has been identified as a component of several chromatin remodeling complexes present in the nucleus. In animal cells, nuclear actin exists as a dynamic equilibrium of monomers and polymers. Actin-binding proteins (ABPs) such as ADF/cofilin and profilin play a role in actin import and export, respectively. However, very little is known about the localization and roles of nuclear actin in plants. In multicellular plants and animals, actin is comprised of an ancient and divergent family of protein variants. Here, we have investigated the presence and differential localization of two ancient subclasses of actin in isolated Arabidopsis nuclei. Although the subclass 1 variants ACT2 and ACT8 and subclass 2 variant ACT7 were found distributed throughout the nucleoplasm, ACT7 was often found more concentrated in nuclear speckles than subclass 1 variants. The nuclei from the act2-1/act8-2 double null mutant and the act7-5 null mutant lacked their corresponding actin variants. In addition, serial sectioning of several independent nuclei revealed that ACT7 was notably more abundant in the nucleolus than the subclass 1 actins. Profilin and ADF proteins were also found in significant levels in plant nuclei. The possible functions of differentially localized nuclear actin variants are discussed.
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Affiliation(s)
- Muthugapatti K Kandasamy
- Department of Genetics, Davison Life Sciences Complex, University of Georgia, Athens, Georgia 30602, USA
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Bernstein BW, Maloney MT, Bamburg JR. Actin and Diseases of the Nervous System. ADVANCES IN NEUROBIOLOGY 2011; 5:201-234. [PMID: 35547659 PMCID: PMC9088176 DOI: 10.1007/978-1-4419-7368-9_11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Abnormal regulation of the actin cytoskeleton results in several pathological conditions affecting primarily the nervous system. Those of genetic origin arise during development, but others manifest later in life. Actin regulation is also affected profoundly by environmental factors that can have sustained consequences for the nervous system. Those consequences follow from the fact that the actin cytoskeleton is essential for a multitude of cell biological functions ranging from neuronal migration in cortical development and dendritic spine formation to NMDA receptor activity in learning and alcoholism. Improper regulation of actin, causing aggregation, can contribute to the neurodegeneration of amyloidopathies, such as Down's syndrome and Alzheimer's disease. Much progress has been made in understanding the molecular basis of these diseases.
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Affiliation(s)
- Barbara W Bernstein
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - Michael T Maloney
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | - James R Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523
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17
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Dialynas G, Speese S, Budnik V, Geyer PK, Wallrath LL. The role of Drosophila Lamin C in muscle function and gene expression. Development 2010; 137:3067-77. [PMID: 20702563 DOI: 10.1242/dev.048231] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The inner side of the nuclear envelope (NE) is lined with lamins, a meshwork of intermediate filaments that provides structural support for the nucleus and plays roles in many nuclear processes. Lamins, classified as A- or B-types on the basis of biochemical properties, have a conserved globular head, central rod and C-terminal domain that includes an Ig-fold structural motif. In humans, mutations in A-type lamins give rise to diseases that exhibit tissue-specific defects, such as Emery-Dreifuss muscular dystrophy. Drosophila is being used as a model to determine tissue-specific functions of A-type lamins in development, with implications for understanding human disease mechanisms. The GAL4-UAS system was used to express wild-type and mutant forms of Lamin C (the presumed Drosophila A-type lamin), in an otherwise wild-type background. Larval muscle-specific expression of wild type Drosophila Lamin C caused no overt phenotype. By contrast, larval muscle-specific expression of a truncated form of Lamin C lacking the N-terminal head (Lamin C DeltaN) caused muscle defects and semi-lethality, with adult 'escapers' possessing malformed legs. The leg defects were due to a lack of larval muscle function and alterations in hormone-regulated gene expression. The consequences of Lamin C association at a gene were tested directly by targeting a Lamin C DNA-binding domain fusion protein upstream of a reporter gene. Association of Lamin C correlated with localization of the reporter gene at the nuclear periphery and gene repression. These data demonstrate connections among the Drosophila A-type lamin, hormone-induced gene expression and muscle function.
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Affiliation(s)
- George Dialynas
- Department of Biochemistry, University of Iowa, Iowa City, IA 52241, USA
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Castano E, Philimonenko VV, Kahle M, Fukalová J, Kalendová A, Yildirim S, Dzijak R, Dingová-Krásna H, Hozák P. Actin complexes in the cell nucleus: new stones in an old field. Histochem Cell Biol 2010; 133:607-26. [PMID: 20443021 DOI: 10.1007/s00418-010-0701-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2010] [Indexed: 01/13/2023]
Abstract
Actin is a well-known protein that has shown a myriad of activities in the cytoplasm. However, recent findings of actin involvement in nuclear processes are overwhelming. Actin complexes in the nucleus range from very dynamic chromatin-remodeling complexes to structural elements of the matrix with single partners known as actin-binding proteins (ABPs). This review summarizes the recent findings of actin-containing complexes in the nucleus. Particular attention is given to key processes like chromatin remodeling, transcription, DNA replication, nucleocytoplasmic transport and to actin roles in nuclear architecture. Understanding the mechanisms involving ABPs will definitely lead us to the principles of the regulation of gene expression performed via concerting nuclear and cytoplasmic processes.
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Affiliation(s)
- E Castano
- Department of Biology of the Cell Nucleus, Institute of Molecular Genetics of the ASCR, Prague, Czech Republic
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19
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Affiliation(s)
- C.B. SHUSTER
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - I.M. HERMAN
- Department of Physiology, Tufts University School of Medicine, Boston, MA, USA
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20
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Bogolyubova NA, Bogolyubova IO. Actin localization in nuclei of two-cell mouse embryos. ACTA ACUST UNITED AC 2009. [DOI: 10.1134/s1990519x09050034] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Ono K, Ono S. Actin-ADF/cofilin rod formation in Caenorhabditis elegans muscle requires a putative F-actin binding site of ADF/cofilin at the C-terminus. ACTA ACUST UNITED AC 2009; 66:398-408. [PMID: 19459188 DOI: 10.1002/cm.20383] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Under a number of stress or pathological conditions, actin and actin depolymerizing factor (ADF)/cofilin form rod-like structures that contain abnormal bundles of actin filaments that are heavily decorated with ADF/cofilin. However, the mechanism of actin rod formation and the physiological role of actin rods are not clearly understood. Here, we report that overexpression of green fluorescent protein-fused UNC-60B, a muscle-specific ADF/cofilin isoform, in Caenorhabditis elegans body wall muscle induces formation of rod-like structures. The rods contained GFP-UNC-60B, actin-interacting protein 1 (AIP1), and actin, but not other major actin-associated proteins, thus resembling actin-ADF/cofilin rods found in other organisms. However, depletion or overexpression of AIP1 did not affect formation of the actin-GFP-UNC-60B rods, suggesting that AIP1 does not play a significant role in the rod assembly. Truncation of the C-terminal tail, a putative F-actin binding site, of UNC-60B abolished induction of the rod formation, strongly suggesting that stable association of UNC-60B with F-actin, which is mediated by its C-terminus, is required for inducing actin-ADF/cofilin rods. This study suggests that C. elegans can be a new model to study functions of actin-ADF/cofilin rods.
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Affiliation(s)
- Kanako Ono
- Department of Pathology, Emory University, Atlanta, Georgia 30322, USA
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22
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Bamburg JR, Bloom GS. Cytoskeletal pathologies of Alzheimer disease. CELL MOTILITY AND THE CYTOSKELETON 2009; 66:635-49. [PMID: 19479823 PMCID: PMC2754410 DOI: 10.1002/cm.20388] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The histopathological hallmarks of Alzheimer disease are the extracellular amyloid plaques, composed principally of the amyloid beta peptide, and the intracellular neurofibrillary tangles, composed of paired helical filaments of the microtubule-associated protein, tau. Other histopathological structures involving actin and the actin-binding protein, cofilin, have more recently been recognized. Here we review new findings about these cytoskeletal pathologies, and, emphasize how plaques, tangles, the actin-containing inclusions and their respective building blocks may contribute to Alzheimer pathogenesis and the primary behavioral symptoms of the disease. Cell Motil. Cytoskeleton, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- James R Bamburg
- Department of Biochemistry and Molecular Biology, Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, USA.
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Gieni RS, Hendzel MJ. Actin dynamics and functions in the interphase nucleus: moving toward an understanding of nuclear polymeric actin. Biochem Cell Biol 2009; 87:283-306. [PMID: 19234542 DOI: 10.1139/o08-133] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Actin exists as a dynamic equilibrium of monomers and polymers within the nucleus of living cells. It is utilized by the cell for many aspects of gene regulation, including mRNA processing, chromatin remodelling, and global gene expression. Polymeric actin is now specifically linked to transcription by RNA polymerase I, II, and III. An active process, requiring both actin polymers and myosin, appears to drive RNA polymerase I transcription, and is also implicated in long-range chromatin movement. This type of mechanism brings activated genes from separate chromosomal territories together, and then participates in their compartmentalization near nuclear speckles. Nuclear speckle formation requires polymeric actin, and factors promoting polymerization, such as profilin and PIP2, are concentrated there. A review of the literature shows that a functional population of G-actin cycles between the cytoplasm and the nucleoplasm. Its nuclear concentration is dependent on the cytoplasmic G-actin pool, as well as on the activity of import and export mechanisms and the availability of interactions that sequester it within the nucleus. The N-WASP-Arp2/3 actin polymer-nucleating mechanism functions in the nucleus, and its mediators, including NCK, PIP2, and Rac1, can be found in the nucleoplasm, where they likely influence the kinetics of polymer formation. The actin polymer species produced are tightly regulated, and may take on conformations not easily recognized by phalloidin. Many of the factors that cleave F-actin in the cytoplasm are present at high levels in the nucleoplasm, and are also likely to affect actin dynamics there. The absolute and relative G-actin content in the nucleoplasm and the cytoplasm of a cell contains information about the homeostatic state of that cell. We propose that the cycling of G-actin between the nucleus and cytoplasm represents a signal transduction mechanism that can function through both extremes of global cellular G-actin content. MAL signalling within the serum response factor pathway, when G-actin levels are low, represents a well-studied example of actin functioning in signal transduction. The translocation of NCK into the nucleus, along with G-actin, during dissolution of the cytoskeleton in response to DNA damage represents another instance of a unique signalling mechanism operating when G-actin levels are high.
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Affiliation(s)
- Randall S Gieni
- Cross Cancer Institute and Department of Oncology, Faculty of Medicine, University of Alberta, Edmonton, ABT6G1Z2, Canada
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Burgos-Rivera B, Ruzicka DR, Deal RB, McKinney EC, King-Reid L, Meagher RB. ACTIN DEPOLYMERIZING FACTOR9 controls development and gene expression in Arabidopsis. PLANT MOLECULAR BIOLOGY 2008; 68:619-32. [PMID: 18830798 PMCID: PMC2811079 DOI: 10.1007/s11103-008-9398-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 08/31/2008] [Indexed: 05/20/2023]
Abstract
Actin depolymerizing factors (ADF/cofilin) modulate the rate of actin filament turnover, networking cellular signals into cytoskeletal-dependent developmental pathways. Plant and animal genomes encode families of diverse ancient ADF isovariants. One weakly but ubiquitously expressed member of the Arabidopsis ADF gene family, ADF9, is moderately expressed in the shoot apical meristem (SAM). Mutant alleles adf9-1 and adf9-2 showed a 95% and 50% reduction in transcript levels, respectively. Compared to wild-type, mutant seedlings and plants were significantly smaller and adult mutant plants had decreased numbers of lateral branches and a reduced ability to form callus. The mutants flowered very early during long-day light cycles, but not during short days. adf9-1showed a several-fold lower expression of FLOWERING LOCUS C (FLC), a master repressor of the transition to flowering, and increased expression of CONSTANS, an activator of flowering. Transgenic ADF9 expression complemented both developmental and gene expression phenotypes. FLC chromatin from adf9-1 plants contained reduced levels of histone H3 lysine 4 trimethylation and lysine 9 and 14 acetylation, as well as increased nucleosome occupancy consistent with a less active chromatin state. We propose that ADF9 networks both cytoplasmic and nuclear processes within the SAM to control multicellular development.
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Affiliation(s)
| | | | - Roger B. Deal
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave North, Seattle, WA 98109, USA
| | | | - Lori King-Reid
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
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25
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Maloney MT, Bamburg JR. Cofilin-mediated neurodegeneration in Alzheimer's disease and other amyloidopathies. Mol Neurobiol 2007; 35:21-44. [PMID: 17519504 DOI: 10.1007/bf02700622] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 11/30/1999] [Accepted: 09/05/2006] [Indexed: 12/16/2022]
Abstract
Transport defects may arise in various neurodegenerative diseases from failures in molecular motors, microtubule abnormalities, and the chaperone/proteasomal degradation pathway leading to aggresomal-lysosomal accumulations. These defects represent important steps in the neurodegenerative cascade, although in many cases, a clear consensus has yet to be reached regarding their causal relationship to the disease. A growing body of evidence lends support to a link between neurite transport defects in the very early stages of many neurodegenerative diseases and alterations in the organization and dynamics of the actin cytoskeleton initiated by filament dynamizing proteins in the ADF/cofilin family. This article focuses on cofilin, which in neurons under stress, including stress induced by the amyloid-beta (Abeta) 1-42 peptide, undergoes dephosphorylation (activation) and forms rod-shaped actin bundles (rods). Rods inhibit transport, are sites of amyloid precursor protein accumulation, and contribute to the pathology of Alzheimer's disease. Because rods form rapidly in response to anoxia, they could also contribute to synaptic deficits associated with ischemic brain injury (e.g., stroke). Surprisingly, cofilin undergoes phosphorylation (inactivation) in hippocampal neurons treated with Abeta1-40 at high concentrations, and these neurons undergo dystrophic morphological changes, including accumulation of pretangle phosphorylated-tau. Therefore, extremes in phosphoregulation of cofilin by different forms of Abeta may explain much of the Alzheimer's disease pathology and provide mechanisms for synaptic loss and plaque expansion.
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Affiliation(s)
- Michael T Maloney
- Department of Biochemistry and Molecular Biology, Cellular and Integrative Neurosciences Program, Colorado State University, Fort Collins, CO, USA
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Hosoda A, Sato N, Nagaoka R, Abe H, Obinata T. Activity of cofilin can be regulated by a mechanism other than phosphorylation/dephosphorylation in muscle cells in culture. J Muscle Res Cell Motil 2007; 28:183-94. [PMID: 17823847 DOI: 10.1007/s10974-007-9117-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Accepted: 08/13/2007] [Indexed: 11/29/2022]
Abstract
Cofilin plays a critical role in actin filament dynamics in a variety of eukaryotic cells. Its activity is regulated by phosphorylation/dephosphorylation of a Ser3 residue on the N-terminal side and/or its binding to a phosphoinositide, PIP(2). To clarify how cofilin activity is regulated in muscle cells, we generated analogues of the unphosphorylated form (A3-cofilin) and phosphorylated form (D3-cofilin) by converting the phosphorylation site (Ser3) of cofilin to Ala and Asp, respectively. These mutated proteins, as well as the cofilin having Ser3 residue (S3-cofilin), were produced in an E. coli expression system and conjugated with fluorescent dyes. In an in vitro functional assay, A3-cofilin retained the ability to bind to F-actin. Upon injection into cultured muscle cells, A3-cofilin and S3-cofilin promptly disrupted actin filaments in the cytoplasm, and many cytoplasmic rods containing both the exogenous cofilin and actin were generated, while D3-cofilin was simply diffused in the cytoplasm without affecting actin filaments. Several hours after the injection, however, the activity of A3-cofilin and S3-cofilin was suppressed: the actin-A3-cofilin (or S3-cofilin) rods disappeared, the cofilin diffused in the cytoplasm like D3-cofilin, and actin filaments reformed. Both GFP-fused A3-cofilin and S3-cofilin that were produced by cDNA transfection were also suppressed in the cytoplasm of muscle cells in culture. Thus, some mechanism(s) other than phosphorylation can suppress A3-cofilin activity. We observed that PIP(2) can bind to A3-cofilin just as to S3-cofilin and inhibits the interaction of A3-cofilin with actin. Our results suggest that the activity of A3-cofilin and also S3-cofilin can be regulated by PIP(2) in the cytoplasm of muscle cells.
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Affiliation(s)
- Atsuko Hosoda
- Department of Biology, Faculty of Science, Chiba University, Chiba 263-8522, Japan
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27
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Ono S. Mechanism of depolymerization and severing of actin filaments and its significance in cytoskeletal dynamics. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 258:1-82. [PMID: 17338919 DOI: 10.1016/s0074-7696(07)58001-0] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The actin cytoskeleton is one of the major structural components of the cell. It often undergoes rapid reorganization and plays crucial roles in a number of dynamic cellular processes, including cell migration, cytokinesis, membrane trafficking, and morphogenesis. Actin monomers are polymerized into filaments under physiological conditions, but spontaneous depolymerization is too slow to maintain the fast actin filament dynamics observed in vivo. Gelsolin, actin-depolymerizing factor (ADF)/cofilin, and several other actin-severing/depolymerizing proteins can enhance disassembly of actin filaments and promote reorganization of the actin cytoskeleton. This review presents advances as well as a historical overview of studies on the biochemical activities and cellular functions of actin-severing/depolymerizing proteins.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, GA 30322, USA
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28
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Mannherz HG, Gonsior SM, Wu X, Polzar B, Pope BJ, Wartosch L, Weeds AG. Dual effects of staurosporine on A431 and NRK cells: microfilament disassembly and uncoordinated lamellipodial activity followed by cell death. Eur J Cell Biol 2006; 85:785-802. [PMID: 16697076 DOI: 10.1016/j.ejcb.2006.02.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 02/09/2006] [Accepted: 02/13/2006] [Indexed: 12/11/2022] Open
Abstract
The general protein kinase inhibitor staurosporine (STS) has dual effects on human epidermoid cancer cells (A431) and normal rat kidney fibroblasts (NRK). It almost immediately stimulated increased lamellipodial activity of both cell lines and after 2 h induced typical signs of apoptosis, including cytoplasmic condensation, nuclear fragmentation, caspase-3 activation and DNA degradation. In the early phase we observed disruption of actin-containing stress fibres and accumulation of monomeric actin in the perinuclear region and cell nucleus. Increased lamellipodial-like extensions were observed particularly in A431 cells as demonstrated by co-localisation of actin and Arp2/3 complex, whereas NRK cells shrunk and exhibited numerous thin long extensions. These extensions exhibited uncoordinated centrifugal motile activity that appeared to tear the cells apart. Both cofilin and ADF were translocated from perinuclear regions to the cell cortex and, as expected in the presence of a kinase inhibitor, all the cofilin was dephosphorylated. Myosin II was absent from the extensions, and a reduction of phosphorylated myosin light chains was observed within the cytoplasm indicating myosin inactivation. Microtubules and intermediate filaments retained their characteristic filamentous organisation after STS exposure even when the cells became rounded and disorganised. Simultaneous treatment of NRK cells with STS and the caspase inhibitor zVAD did not inhibit the morphological and cytoskeletal changes. However, the cells underwent cell death as verified by positive annexin-V-staining. Thus it seems likely that cell death induced by STS may not only be a consequence of the activation of caspase, instead the disruption of the many motile processes involving the actin cytoskeleton may by itself suffice to induce caspase-independent cell death.
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Affiliation(s)
- Hans G Mannherz
- Department of Anatomy and Embryology, Ruhr-University, Bochum, Germany.
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29
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Tanaka K, Nishio R, Haneda K, Abe H. Functional involvement of Xenopus homologue of ADF/cofilin phosphatase, slingshot (XSSH), in the gastrulation movement. Zoolog Sci 2006; 22:955-69. [PMID: 16219976 DOI: 10.2108/zsj.22.955] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
ADF/cofilin is a phosphorylation-regulated protein essential for actin filament dynamics in cells. Here, we cloned two cDNAs encoding Xenopus ADF/cofilin (XAC)-specific phosphatase, slingshot (XSSH), one of which contains an extra 15 nucleotides in a coding sequence of the other, possibly generated by alternative splicing. Whole mount in situ hybridization showed XSSH transcripts in the blastopore lip and sensorial ectoderm at stage 11, and subsequently localized to developing brain, branchial arches, developing retina, otic vesicle, cement gland, and spinal chord in neurula to tailbud embryos. Immunostaining of animal-vegetal sections of gastrula embryos demonstrated that both XAC and XSSH proteins are predominant in ectodermal and involuting mesodermal cells. Microinjection of either a wild type (thus induces overexpression) or a phosphatase-defective mutant (functions as dominantly negative form) resulted in defects in gastrulation, and often generated the spina bifida phenotype with reduced head structures. Interestingly, the ratio of phosphorylated XAC to dephosphorylated XAC markedly increased from the early gastrula stage (stage 10.5), although the amount of XSSH protein markedly increased from this stage. These results suggest that gastrulation movement requires ADF/cofilin activity through dynamic regulation of its phosphorylation state.
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Gettemans J, Van Impe K, Delanote V, Hubert T, Vandekerckhove J, De Corte V. Nuclear actin-binding proteins as modulators of gene transcription. Traffic 2005; 6:847-57. [PMID: 16138899 DOI: 10.1111/j.1600-0854.2005.00326.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Dynamic transformations in the organization of the cellular microfilament system are the driving force behind fundamental biological processes such as cellular motility, cytokinesis, wound healing and secretion. Eukaryotic cells express a plethora of actin-binding proteins (ABPs) allowing cells to control the organization of the actin cytoskeleton in a flexible manner. These structural proteins were, not surprisingly, originally described as (major) constituents of the cytoplasm. However, in recent years, there has been a steady flow of reports detailing not only translocation of ABPs into and out of the nucleus but also describing their role in the nuclear compartment. This review focuses on recent developments pertaining to nucleocytoplasmic transport of ABPs, including their mode of translocation and nuclear function. In particular, evidence that structurally and functionally unrelated cytoplasmic ABPs regulate transcription activation by various nuclear (steroid hormone) receptors is steadily accruing. Furthermore, the recent finding that actin is a necessary component of the RNA polymerase II-containing preinitiation complex opens up new opportunities for nuclear ABPs in gene transcription regulation.
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Affiliation(s)
- Jan Gettemans
- Department of Medical Protein Research, Flanders Interuniversity Institute for Biotechnology, Ghent University, Albert Baertsoenkaai 3, B-9000 Ghent, Belgium.
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Chhabra D, Nosworthy NJ, dos Remedios CG. The N-terminal fragment of gelsolin inhibits the interaction of DNase I with isolated actin, but not with the cofilin-actin complex. Proteomics 2005; 5:3131-6. [PMID: 16021605 DOI: 10.1002/pmic.200401127] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Apoptosis is essential in embryonic development, clonal selection of cells of the immune system and in the prevention of cancer. Apoptotic cells display characteristic changes in morphology that precede the eventual fragmentation of nuclear DNA resulting in cell death. Current evidence implicates DNase I as responsible for hydrolysis of DNA during apoptosis. In vivo, it is likely that cytoplasmic actin binds and inhibits the enzymatic activity and nuclear translocation of DNase I and that disruption of the actin-DNase I complex results in activation of DNase I. In this report we demonstrate that the N-terminal fragment of gelsolin (N-gelsolin) disrupts the actin-DNase I interaction. This provides a molecular mechanism for the role of the N-gelsolin in regulating DNase I activity. We also show that cofilin stabilises the actin-DNase I complex by forming a ternary complex that prevents N-gelsolin from releasing DNase I from actin. We suggest that both cofilin and gelsolin are essential in modulating the release of DNase I from actin.
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Affiliation(s)
- Deepak Chhabra
- Muscle Research Unit, Institute for Biomedical Research, School of Medical Sciences, University of Sydney, NSW 2006, Australia
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Falet H, Chang G, Brohard-Bohn B, Rendu F, Hartwig JH. Integrin αIIbβ3signals lead cofilin to accelerate platelet actin dynamics. Am J Physiol Cell Physiol 2005; 289:C819-25. [PMID: 15901596 DOI: 10.1152/ajpcell.00587.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cofilin, in its Ser3 dephosphorylated form, accelerates actin filament turnover in cells. We report here the role of cofilin in platelet actin assembly. Cofilin is primarily phosphorylated in the resting platelet as evidenced by a specific antibody directed against its Ser3 phosphorylated form. After stimulation with thrombin under nonstirring conditions, cofilin is reversibly dephosphorylated and transiently incorporates into the actin cytoskeleton. Its dephosphorylation is maximal 1–2 min after platelet stimulation, shortly after the peak of actin assembly occurs. Cofilin rephosphorylation begins 2 min after activation and exceeds resting levels by 5–10 min. Cofilin is dephosphorylated with identical kinetics but fails to become rephosphorylated when platelets are stimulated under stirring conditions. Cofilin is normally rephosphorylated when platelets are stimulated in the presence of Arg-Gly-Asp-Ser (RGDS) peptide or wortmannin to block αIIbβ3cross-linking and signaling or in platelets isolated from a patient with Glanzmann thrombasthenia, which express only 2–3% of normal αIIbβ3levels. Furthermore, actin assembly and Arp2/3 complex incorporation in the platelet actin cytoskeleton are decreased when αIIbβ3is engaged. Our results suggest that cofilin is essential for actin dynamics mediated by outside-in signals in activated platelets.
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Affiliation(s)
- Hervé Falet
- Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, One Blackfan Circle, Karp 6, Boston, Massachusetts 02115, USA.
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de Lanerolle P, Johnson T, Hofmann WA. Actin and myosin I in the nucleus: what next? Nat Struct Mol Biol 2005; 12:742-6. [PMID: 16142228 DOI: 10.1038/nsmb983] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2005] [Accepted: 08/04/2005] [Indexed: 11/09/2022]
Abstract
Several recent publications have demonstrated the importance of nuclear actin and nuclear myosin I in transcription. Here we review these publications and their implications. In addition, we discuss some important issues that should be addressed to gain a more comprehensive understanding of how these traditionally 'cytoplasmic' proteins are involved in transcription. We propose highly speculative models and mechanisms solely to stimulate thought and experimentation in this area.
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Affiliation(s)
- Primal de Lanerolle
- the Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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34
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Chhabra D, dos Remedios CG. Cofilin, actin and their complex observed in vivo using fluorescence resonance energy transfer. Biophys J 2005; 89:1902-8. [PMID: 15994898 PMCID: PMC1366693 DOI: 10.1529/biophysj.105.062083] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Accepted: 06/20/2005] [Indexed: 01/10/2023] Open
Abstract
Actin is the principal component of microfilaments. Its assembly/disassembly is essential for cell motility, cytokinesis, and a range of other functions. Recent evidence suggests that actin is present in the nucleus where it may be involved in the regulation of gene expression and that cofilin binds actin and can translocate into the nucleus during times of stress. In this report, we combine fluorescence resonance energy transfer and confocal microscopy to analyze the interactions of cofilin and G-actin within the nucleus and cytoplasm. By measuring the rate of photobleaching of fluorescein-labeled actin in the presence and absence of Cy5-labeled cofilin, we determined that almost all G-actin in the nucleus is bound to cofilin, whereas approximately (1/2) is bound in the cytoplasm. Using fluorescence resonance energy transfer imaging techniques we observed that a significant proportion of fluorescein-labeled cofilin in both the nucleus and cytoplasm binds added tetramethylrhodamine-labeled G-actin. Our data suggest there is significantly more cofilin-G-actin complex and less free cofilin in the nucleus than in the cytoplasm.
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Affiliation(s)
- D Chhabra
- Muscle Research Unit, School of Medical Sciences, Institute for Biomedical Research, University of Sydney, Sydney, New South Wales, Australia.
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35
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Shin I, Rotty J, Wu FY, Arteaga CL. Phosphorylation of p27Kip1 at Thr-157 interferes with its association with importin alpha during G1 and prevents nuclear re-entry. J Biol Chem 2004; 280:6055-63. [PMID: 15579463 DOI: 10.1074/jbc.m412367200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We have studied mechanisms of Akt-mediated phosphorylation and regulation of cellular localization of p27. Akt phosphorylates Thr-157 in p27 and retains it in the cytosol. In cells arrested in G(1) and then synchronized to enter into S phase, Akt-mediated phosphorylation of Thr-157 p27 occurred in the cytosol during G(1) phase of the cell cycle. Both T157A and S10A p27 mutants localized in the nucleus in all phases of the cell cycle regardless of the expression of active Akt. Thr-157 phosphorylation was undetectable in S10A-p27, suggesting that Ser-10 phosphorylation is required for p27 localization in the cytosol and subsequent phosphorylation at Thr-157. Phosphorylation at Thr-157 interrupted the association of p27 with importin alpha. A T157A-p27 mutant protein exhibited higher association with importin alpha than wild-type-p27. Treatment of transfected and endogenous p27 with alkaline phosphatase rescued its association with importin alpha. Leptomycin B inhibited cytosolic Thr-157 P-p27 staining, implying that CRM1-dependent nuclear export is required for Akt-mediated Thr-157 phosphorylation. Heterokaryon shuttling assays with NIH3T3 (mouse) cells transfected with FLAG-p27 and HeLa (human) cells revealed that both wild type and T157A-p27 shuttled from NIH3T3 to HeLa cell nuclei with similar frequencies. However, S10A-p27 was found only in the NIH3T3 nuclei of NIH3T3-HeLa cell fusions. These results suggest that 1) Ser-10 phosphorylation is required for nuclear export of p27, 2) subsequent Akt-mediated phosphorylation at Thr-157 during G(1) phase corrals p27 in the cytosol, and 3) Thr-157 phosphorylation inhibits the association of p27 with importin alpha thus preventing its re-entry into the nucleus.
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Affiliation(s)
- Incheol Shin
- Department of Cancer Biology and Medicine, Vanderbilt-Ingram Comprehensive Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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36
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Affiliation(s)
- Blaine T Bettinger
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA
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37
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Samstag Y, Nebl G. Interaction of cofilin with the serine phosphatases PP1 and PP2A in normal and neoplastic human T lymphocytes. ADVANCES IN ENZYME REGULATION 2004; 43:197-211. [PMID: 12791392 DOI: 10.1016/s0065-2571(02)00031-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Yvonne Samstag
- Institute for Immunology, Ruprecht-Karls-University, Im Neuenheimer Feld 305, D-69120, Heidelberg, Germany.
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38
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Krauer K, Buck M, Flanagan J, Belzer D, Sculley T. Identification of the nuclear localization signals within the Epstein–Barr virus EBNA-6 protein. J Gen Virol 2004; 85:165-172. [PMID: 14718631 DOI: 10.1099/vir.0.19549-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Epstein-Barr virus nuclear antigen (EBNA)-6 is essential for EBV-induced immortalization of primary human B-lymphocytes in vitro. Previous studies have shown that EBNA-6 acts as a transcriptional regulator of viral and cellular genes; however at present, few functional domains of the 140 kDa EBNA-6 protein have been completely characterized. There are five computer-predicted nuclear localization signals (NLS), four monopartite and one bipartite, present in the EBNA-6 amino acid sequence. To identify which of these NLS are functional, fusion proteins between green fluorescent protein and deletion constructs of EBNA-6 were expressed in HeLa cells. Each of the constructs containing at least one of the NLS was targeted to the nucleus of cells whereas a construct lacking all of the NLS was cytoplasmic. Site-directed mutation of these NLS demonstrated that only three of the NLS were functional, one at the N-terminal end (aa 72-80), one in the middle (aa 412-418) and one at the C-terminal end (aa 939-945) of the EBNA-6 protein.
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Affiliation(s)
- Kenia Krauer
- Queensland Institute of Medical Research and ACITHN University of Queensland, 300 Herston Road, Brisbane 4029, Queensland, Australia
| | - Marion Buck
- Queensland Institute of Medical Research and ACITHN University of Queensland, 300 Herston Road, Brisbane 4029, Queensland, Australia
| | - James Flanagan
- Queensland Institute of Medical Research and ACITHN University of Queensland, 300 Herston Road, Brisbane 4029, Queensland, Australia
| | - Deanna Belzer
- Queensland Institute of Medical Research and ACITHN University of Queensland, 300 Herston Road, Brisbane 4029, Queensland, Australia
| | - Tom Sculley
- Queensland Institute of Medical Research and ACITHN University of Queensland, 300 Herston Road, Brisbane 4029, Queensland, Australia
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39
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Van Impe K, De Corte V, Eichinger L, Bruyneel E, Mareel M, Vandekerckhove J, Gettemans J. The Nucleo-cytoplasmic actin-binding protein CapG lacks a nuclear export sequence present in structurally related proteins. J Biol Chem 2003; 278:17945-52. [PMID: 12637565 DOI: 10.1074/jbc.m209946200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite thorough structure-function analyses, it remains unclear how CapG, a ubiquitous F-actin barbed end capping protein that controls actin microfilament turnover in cells, is able to reside in the nucleus and cytoplasm, whereas structurally related actin-binding proteins are predominantly cytoplasmic. Here we report the molecular basis for the different subcellular localization of CapG, severin, and fragminP. Green fluorescent protein-tagged fragminP and severin accumulate in the nucleus upon treatment of transfected cells with the CRM1 inhibitor leptomycin B. We identified a nuclear export sequence in severin and fragminP, which is absent in CapG. Deletion of amino acids Met(1)-Leu(27) resulted in nuclear accumulation of severin and fragminP. Tagging this sequence to CapG triggered nuclear export, whereas mutation of single leucine residues (Leu(17), Leu(21), and Leu(27)) in the export sequence inhibited nuclear export. Based on these findings, a nuclear export signal was identified in myopodin, a muscle-specific actin-binding protein, and the Bloom syndrome protein, a RecQ-like helicase. Deletion of the myopodin nuclear export sequence blocked invasion into collagen type I of C2C12 cells transiently overexpressing myopodin. Our findings explain regulated subcellular targeting of distinct classes of actin-binding proteins.
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Affiliation(s)
- Katrien Van Impe
- Department of Biochemistry, Flanders Interuniversity Institute for Biotechnology, Faculty of Medicine and Health Sciences, Ghent University, Rommelaere Institute, Albert Baertsoenkaai 3, B-9000 Ghent, Belgium
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40
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Panasenko OO, Kim MV, Marston SB, Gusev NB. Interaction of the small heat shock protein with molecular mass 25 kDa (hsp25) with actin. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:892-901. [PMID: 12603322 DOI: 10.1046/j.1432-1033.2003.03449.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The interaction of heat shock protein with molecular mass 25 kDa (HSP25) and its point mutants S77D + S81D (2D mutant) and S15D + S77D + S81D (3D mutant) with intact and thermally denatured actin was analyzed by means of fluorescence spectroscopy and ultracentrifugation. Wild type HSP25 did not affect the polymerization of intact actin. The HSP25 3D mutant decreased the initial rate without affecting the maximal extent of intact actin polymerization. G-actin heated at 40-45 degrees C was partially denatured, but retained its ability to polymerize. The wild type HSP25 did not affect polymerization of this partially denatured actin. The 3D mutant of HSP25 increased the initial rate of polymerization of partially denatured actin. Heating at more than 55 degrees C induced complete denaturation of G-actin. Completely denatured G-actin cannot polymerize, but it aggregates at increased ionic strength. HSP25 and especially its 2D and 3D mutants effectively prevent salt-induced aggregation of completely denatured actin. It is concluded that the interaction of HSP25 with actin depends on the state of both actin and HSP25. HSP25 predominantly acts as a chaperone and preferentially interacts with thermally unfolded actin, preventing the formation of insoluble aggregates.
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Affiliation(s)
- Olesya O Panasenko
- Department of Biochemistry, School of Biology, Moscow State University, Moscow 119992, Russia
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41
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Jung J, Yoon T, Choi EC, Lee K. Interaction of cofilin with triose-phosphate isomerase contributes glycolytic fuel for Na,K-ATPase via Rho-mediated signaling pathway. J Biol Chem 2002; 277:48931-7. [PMID: 12359716 DOI: 10.1074/jbc.m208806200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We reported previously that cofilin, an actin-binding protein, interacts with Na,K-ATPase and enhances its activity (Lee, K., Jung, J., Kim, M., and Guidotti, G. (2001) Biochem. J. 353, 377-385). To understand the nature of this interaction and the role of cofilin in the regulation of Na,K-ATPase activity, we searched for cofilin-binding proteins in the rat skeletal muscle cDNA library using the yeast two-hybrid system. Several cDNA clones were isolated, some of which coded for triose-phosphate isomerase, a glycolytic enzyme. The interaction of cofilin with triose-phosphate isomerase as well as Na,K-ATPase was confirmed by immunoprecipitation and confocal microscopy in HeLa cells. Cofilin was translocated to the plasma membrane along with triose-phosphate isomerase by the Rho activator lysophosphatidic acid but not by the p160 Rho-associated kinase inhibitor Y-27632, suggesting that the phosphorylated form of cofilin bound to TPI interacts with Na,K-ATPase. Ouabain-sensitive (86)Rb(+) uptake showed that Na,K-ATPase activity was increased by the overexpression of cofilin and lysophosphatidic acid treatment, but not by the overexpression of mutant cofilin S3A and Y-27632 treatment. Pretreatment with the glycolytic inhibitor iodoacetic acid caused a remarkable reduction of Na,K-ATPase activity, whereas pretreatment with the oxidative inhibitor carbonyl cyanide m-chlorophenylhydrazone caused no detectable changes, suggesting that the phosphorylated cofilin is involved in feeding glycolytic fuel for Na,K-ATPase activity. These findings provide a novel molecular mechanism for the regulation of Na,K-ATPase activity and for the nature of the functional coupling of cellular energy transduction.
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Affiliation(s)
- Jaehoon Jung
- College of Pharmacy, Center for Cell Signaling Research and Division of Molecular Life Sciences, Ewha Woman's University, Seoul 120-750, Korea
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42
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Takahashi H, Koshimizu U, Miyazaki JI, Nakamura T. Impaired spermatogenic ability of testicular germ cells in mice deficient in the LIM-kinase 2 gene. Dev Biol 2002; 241:259-72. [PMID: 11784110 DOI: 10.1006/dbio.2001.0512] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
LIM-Kinase (LIMK), including LIMK1 and LIMK2, is the only known catalytic protein among LIM-family molecules. It is well known that LIMK phosphorylates and inactivates cofilin, an actin-depolymerizing factor regulating actin reorganization, while in vivo functions have remained to be elucidated. In the present study, we generated Limk2 gene-deficient mice in which three LIMK2 isoforms were disrupted in a Cre-mediated fashion. Impaired cofilin phosphorylation was clearly observed in Limk2-/- fibroblasts stimulated with bradykinin or lysophosphatidic acid, thereby suggesting that Cdc42 or Rho-dependent LIMK activation did not occur. However, Limk2-/- mice did not exhibit embryonic lethality or any phenotypic abnormalities in postnatal growth and development, except for spermatogenesis in the testis. The testes of Limk2-/- mice were smaller in size and partial degeneration of spermatogenic cells in the seminiferous tubules was apparent in association with increased apoptosis. In addition, the viability of Limk2-/- spermatogenic cells, when cultured under stressed conditions, was diminished. Furthermore, the potential for germ cells to differentiate in a regenerative state was severely impaired in Limk2-/- testis. Experimental hyperthermia induced impairment of ADF/cofilin phosphorylation and the formation of intranuclear cofilin inclusions in mutant germ cells. Based on these findings, we propose that LIMK2, especially the testis-specific isoform tLIMK2, plays an important role in proper progression of spermatogenesis by regulation of cofilin activity and/or localization in germ cells.
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Affiliation(s)
- Hisaaki Takahashi
- Division of Molecular Regenerative Medicine, Course of Advanced Medicine B7, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871, Japan
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43
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Hübner S, Jans DA, Drenckhahn D. Roles of cytoskeletal and junctional plaque proteins in nuclear signaling. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 208:207-65. [PMID: 11510569 DOI: 10.1016/s0074-7696(01)08005-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cytoplasmic junctional plaque proteins play an important role at intercellular junctions. They link transmembrane cell adhesion molecules to components of the cytoskeleton, thereby playing an important role in the control of many cellular processes. Recent studies on the subcellular distribution of some plaque proteins have revealed that a number of these proteins are able to localize in the nucleus. This dual location indicates that in addition to promoting adhesive interactions, plaque proteins may also play a direct role in nuclear processes, and in particular in the transfer of signals from the membrane to the nucleus. Therefore, translocation of plaque proteins into the nucleus in response to extracellular signals could represent a novel and direct mechanism by which signals can be transmitted from the plasma membrane to the nucleus. This could allow cells to respond to changing environmental conditions in a rapid and efficient way. In addition, conditional sequestration of karyophilic proteins at the sites of cell-cell and cell-substratum adhesion may represent a general mechanism for the regulation of nucleocytoplasmic transport.
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Affiliation(s)
- S Hübner
- Institut für Anatomie, Universität Würzburg, Germany
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44
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Pfannstiel J, Cyrklaff M, Habermann A, Stoeva S, Griffiths G, Shoeman R, Faulstich H. Human cofilin forms oligomers exhibiting actin bundling activity. J Biol Chem 2001; 276:49476-84. [PMID: 11679578 DOI: 10.1074/jbc.m104760200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human cofilin possesses the tendency for self-association, as indicated by the rapid formation of dimers and oligomers when reacted with water-soluble carbodiimide, Ellman's reagent, or glutathione disulfide. Intermolecular disulfide bonds involve Cys(39) and probably Cys(147) of two adjacent cofilin units. The disulfide-linked dimers and oligomers exhibit a biological activity distinct from the monomer. While monomeric cofilin decreased viscosity and light-scattering of F-actin solutions, dimers and oligomers caused an increase in viscosity and light scattering. Electron microscopy revealed that cofilin oligomers induce the formation of highly ordered actin bundles with occasionally blunt ends similar to actin-cofilin rods observed in cells under oxidative stress. Bundling activity of the disulfide-linked oligomers could be completely reversed into severing activity by dithiothreitol. Formation of cofilin oligomers occurred also in the presence of actin at pH 8, but not at pH 6.6, and was significantly enhanced in the presence of phosphatidylinositol 4,5-bisphosphate. Our data are consistent with the idea that cofilin exists in two forms in vivo also: as monomers exhibiting the known severing activity and as oligomers exhibiting actin bundling activity. However, stabilization of cofilin oligomers in cytoplasm is probably achieved not by disulfide bonds but by a local increase in cofilin concentration and/or binding of regulatory proteins.
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Affiliation(s)
- J Pfannstiel
- Max-Planck-Institute for Medical Research, Heidelberg 69120, Germany.
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45
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Blondin L, Sapountzi V, Maciver SK, Renoult C, Benyamin Y, Roustan C. The second ADF/cofilin actin-binding site exists in F-actin, the cofilin-G-actin complex, but not in G-actin. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:6426-34. [PMID: 11737197 DOI: 10.1046/j.0014-2956.2001.02592.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ADF/cofilins are actin binding proteins that bind actin close to both the N- and C-termini (site 1), and we have found a second cofilin binding site (site 2) centered around helix 112-125 [Renoult, C., Ternent, D., Maciver, S.K., Fattoum, A., Astier, C., Benyamin, Y. & Roustan, C. (1999) J. Biol. Chem. 274, 28893-28899]. We proposed a model in which ADF/cofilin intercalated between subdomains 1 and 2 of two longitudinally associated actin monomers within the actin:cofilin cofilament, explaining the change in twist that ADF/cofilins induce in the filament [McGough, A. Pope, B., Chiu, W. & Weeds, A. (1998) J. Cell Biol. 138, 771-781]. Here, we have determined the fuller extent of the cofilin footprint on site 1 of actin. Site 1 is primarily the G-actin binding site. Experiments with both peptide mimetics and fluorescently labeled cofilin suggest that site 2 only becomes available for cofilin binding within the filament, possibly due to motion between subdomains 1 and 2 within an actin monomer. We have detected motion between subdomains 1 and 2 of G-actin by FRET induced by cofilin, to reveal the second cofilin-binding site. This motion may also explain how cofilins inhibit the nucleotide exchange of actin, and why the actin:cofilin complex is polymerizable without dissociation.
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Affiliation(s)
- L Blondin
- UMR 5539 (CNRS) Laboratoire de motilité cellulaire (Ecole Pratiques des Hautes Etudes), Université de Montpellier 2, France
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46
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Bernstein BW, Painter WB, Chen H, Minamide LS, Abe H, Bamburg JR. Intracellular pH modulation of ADF/cofilin proteins. CELL MOTILITY AND THE CYTOSKELETON 2000; 47:319-36. [PMID: 11093252 DOI: 10.1002/1097-0169(200012)47:4<319::aid-cm6>3.0.co;2-i] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The ADF/cofilin (AC) proteins are necessary for the high rates of actin filament turnover seen in vivo. Their regulation is complex enough to underlie the precision in filament dynamics needed by stimulated cells. Disassembly of actin by AC proteins is inhibited in vitro by phosphorylation of ser3 and pH<7.1. This study of Swiss 3T3 cells demonstrates that pH also affects AC behavior in vivo: (1) Wounded cells show pH-dependent AC translocation to alkaline-induced ruffling membrane; (2) The Triton extractable (soluble) ADF from Swiss 3T3 cells decreases from 42+/-4% to 23+/-4% when the intracellular pH (pH(i)) is reduced from 7.4 to 6.6; (3) Covariance and colocalization analyses of immunostained endogenous proteins show that ADF partitions more with monomeric actin and less with polymeric actin when pH(i) increases. However, the distribution of cofilin, a less pH-sensitive AC in vitro, does not change with pH; (4) Only the unphosphorylatable AC mutant (A3), when overexpressed as a GFP chimera, uniquely produces aberrant cellular phenotypes and only if the pH is shifted from 7.1 to 6.6 or 7.4. A mechanism is proposed that explains why AC(A3)-GFP and AC(wt)-GFP chimeras generate different phenotypes in response to pH changes. Phospho-AC levels increase with cell density, and in motile cells, phospho-AC increases with alkalization, suggesting a homeostatic mechanism that compensates for increased AC activity and filament turnover. These results show that the behavior of AC proteins with pH-sensitivity in vitro is affected by pH in vivo.
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Affiliation(s)
- B W Bernstein
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA.
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47
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Ambach A, Saunus J, Konstandin M, Wesselborg S, Meuer SC, Samstag Y. The serine phosphatases PP1 and PP2A associate with and activate the actin-binding protein cofilin in human T lymphocytes. Eur J Immunol 2000; 30:3422-31. [PMID: 11093160 DOI: 10.1002/1521-4141(2000012)30:12<3422::aid-immu3422>3.0.co;2-j] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cofilin, an actin-depolymerizing protein, is essential for the functional dynamics of the actin cytoskeleton and for cell viability. In unstimulated human peripheral blood T lymphocytes cofilin is phosphorylated and localized in the cytoplasm. Following co-stimulation through accessory receptors (e.g. CD2 or CD28) - however, not following TCR/CD3 stimulation alone - cofilin undergoes dephosphorylation. The subcellular localization as well as the actin-binding activity of cofilin are regulated by the phosphorylation state of serine-3. Thus, only the dephosphorylated form of cofilin associates with the actin cytoskeleton and possesses the capability to translocate into the nucleus. Recently, LIM-kinase 1 was shown to inactivate cofilin through phosphorylation. Here, we have identified the functional counterparts of LIM-kinase 1: the serine/threonine phosphatases of type 1 and type 2A not only associate with cofilin but also dephosphorylate this 19-kDa protein and thereby mediate cofilin activation. In malignant T lymphoma cells, activation of these phosphatases occurs spontaneously, independent of external stimuli. In untransformed human peripheral blood T lymphocytes, these phosphatases function through a cyclosporin A/FK506-resistant co-stimulatory signaling pathway which is common for the accessory receptors CD2 and CD28. This co-stimulatory signaling pathway is also not affected by a series of other clinically established immunosuppressive drugs (i.e. rapamycin, dexamethasone, leflunomide or mycophenolic acid).
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Affiliation(s)
- A Ambach
- Institute for Immunology, Ruprecht-Karls-University, Heidelberg, Germany
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48
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Adachi R, Matsui S, Kinoshita M, Nagaishi K, Sasaki H, Kasahara T, Suzuki K. Nitric oxide induces chemotaxis of neutrophil-like HL-60 cells and translocation of cofilin to plasma membranes. INTERNATIONAL JOURNAL OF IMMUNOPHARMACOLOGY 2000; 22:855-64. [PMID: 11090694 DOI: 10.1016/s0192-0561(00)00045-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Nitric oxide (NO) plays various important roles in the physiological system. With regard to chemotaxis of neutrophils, there are reports that endogenous NO is a mediator of chemotaxis, and others that exogenous NO inhibits chemotaxis. It is also reported that NO itself expressed chemotactic activity. On the other hand, we have recently proposed the importance of cofilin, an actin-binding phosphoprotein, in phagocyte functions through dephosphorylation and translocation to the plasma membrane regions. Because chemotaxis is a phenomenon of dynamic cell movement, cofilin, a regulator of the cytoskeletal system, may be involved in its mechanisms. To clarify further the effect of NO on functions of leukocytes and to examine the effect of NO on cofilin, we investigated the chemotaxis of neutrophil-like HL-60 cells induced by NO, as well as the influence of NO on the phosphorylation and intracellular distribution of cofilin. Two NO donors, 3-[2-hydroxy-1-(1-methylethyl)-2-nitrosohydrazino]-1-propanamin e (NOC5) and S-nitroso-N-acetylpenicillamine (SNAP), were shown to cause chemotaxis, and, 2-(4-carboxyphenyl)-4,4,5, 5-tetramethylimidazole-1-oxyl 3-oxide (carboxy-PTIO), a NO-specific scavenger, inhibited the chemotaxis induced by NO-donors, suggesting that NO itself released from the NO donors has chemotactic activity. LY-83583 and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), inhibitors of soluble guanylate cyclase, inhibited the chemotaxis to NO donors, which implies that soluble guanylate cyclase is involved in the signaling pathway of this NO action. We also found that NO caused translocation of cofilin to the cell periphery, though dephosphorylation of cofilin was not detected. These results demonstrate that NO has chemotactic activity for neutrophils and caused the translocation of cofilin to the plasma membrane regions without its dephosphorylation.
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Affiliation(s)
- R Adachi
- Division of Xenobiotic Metabolism and Disposition, National Institute of Health Sciences, 1-18-1, Kamiyoga, Setagayaku, 158-8501, Tokyo, Japan
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49
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Schwarz S, Greffrath W, Büsselberg D, Treede RD. Inactivation and tachyphylaxis of heat-evoked inward currents in nociceptive primary sensory neurones of rats. J Physiol 2000; 528:539-49. [PMID: 11060130 PMCID: PMC2270164 DOI: 10.1111/j.1469-7793.2000.00539.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2000] [Accepted: 07/20/2000] [Indexed: 01/25/2023] Open
Abstract
Membrane currents evoked by repeated noxious heat stimuli (43-47 degrees C) of 3 s duration were investigated in acutely dissociated dorsal root ganglion (DRG) neurones of adult rats. The heat stimuli generated by a fast solution exchanger had a rise time of 114 +/- 6 ms and a fall time of 146 +/- 13 ms. When heat stimuli were applied to heat-sensitive small (< or = 32.5 microm) DRG neurones, an inward membrane current (I(heat)) with a mean peak of 2430 +/- 550 pA was observed (n = 19). This current started to activate and deactivate with no significant latency with respect to the heat stimulus. The peak of I(heat) was reached with a rise time of 625 +/- 115 ms. When the heat stimulus was switched off I(heat) deactivated with a fall time of 263 +/- 17 ms. During constant heat stimulation I(heat) decreased with time constants of 4-5 s (inactivation). At the end of a 3 s heat stimulus the peak current was reduced by 44 +/- 5 % (n = 19). Current-voltage curves revealed outward rectifying properties of I(heat) and a reversal potential of -6.3 +/- 2.2 mV (n = 6). Inactivation was observed at all membrane potentials investigated (-80 to 60 mV); however, inactivation was more pronounced for inward currents (37 +/- 5 %) than for outward currents (23 +/- 6 %, P < 0.05). When neurones were investigated with repeated heat stimuli (3 to 5 times) of the same temperature, the peak current relative to the first I(heat) declined by 48 +/- 6 % at the 3rd stimulus (n = 19) and by 54 +/- 18 % at the 5th stimulus (n = 4; tachyphylaxis). In the absence of extracellular Ca2+ (buffered with 10 mM EGTA) inactivation (by 53 +/- 6 %) and tachyphylaxis (by 42 +/- 7 % across three stimuli) were still observed (n = 8). The same was true when intracellular Ca2+ was buffered by 10 mM BAPTA (inactivation by 49 +/- 4 %, tachyphylaxis by 52 +/- 7 % across three stimuli; n = 13). Thus, inactivation and tachyphylaxis were mainly independent of intra- and extracellular Ca2+. These results indicate that inactivation and tachyphylaxis of heat-evoked inward currents can be observed in vitro, similar to adaptation and suppression of action potential discharges elicited by comparably fast heat stimuli in vivo. Whereas the voltage dependence of I(heat) resembles that of capsaicin-induced membrane currents (I(Caps)), the independence of inactivation and tachyphylaxis of I(heat) from calcium is in clear contrast to I(Caps). A similar difference in calcium dependence of inactivation has been reported between heat-evoked and capsaicin-induced currents through the cloned capsaicin receptor channel VR1. Thus, the properties of I(heat) and of VR1 largely account for the adaptation and suppression of heat-evoked nociceptor discharges.
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Affiliation(s)
- S Schwarz
- Institute of Physiology and Pathophysiology, Johannes Gutenberg University, D-55099 Mainz, Germany
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Vartiainen M, Ojala PJ, Auvinen P, Peränen J, Lappalainen P. Mouse A6/twinfilin is an actin monomer-binding protein that localizes to the regions of rapid actin dynamics. Mol Cell Biol 2000; 20:1772-83. [PMID: 10669753 PMCID: PMC85359 DOI: 10.1128/mcb.20.5.1772-1783.2000] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In our database searches, we have identified mammalian homologues of yeast actin-binding protein, twinfilin. Previous studies suggested that these mammalian proteins were tyrosine kinases, and therefore they were named A6 protein tyrosine kinase. In contrast to these earlier studies, we did not find any tyrosine kinase activity in our recombinant protein. However, biochemical analysis showed that mouse A6/twinfilin forms a complex with actin monomer and prevents actin filament assembly in vitro. A6/twinfilin mRNA is expressed in most adult tissues but not in skeletal muscle and spleen. In mouse cells, A6/twinfilin protein is concentrated to the areas at the cell cortex which overlap with G-actin-rich actin structures. A6/twinfilin also colocalizes with the activated forms of small GTPases Rac1 and Cdc42 to membrane ruffles and to cell-cell contacts, respectively. Furthermore, expression of the activated Rac1(V12) in NIH 3T3 cells leads to an increased A6/twinfilin localization to nucleus and cell cortex, whereas a dominant negative form of Rac1(V12,N17) induces A6/twinfilin localization to cytoplasm. Taken together, these studies show that mouse A6/twinfilin is an actin monomer-binding protein whose localization to cortical G-actin-rich structures may be regulated by the small GTPase Rac1.
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Affiliation(s)
- M Vartiainen
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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