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Bamburg JR, Minamide LS, Wiggan O, Tahtamouni LH, Kuhn TB. Cofilin and Actin Dynamics: Multiple Modes of Regulation and Their Impacts in Neuronal Development and Degeneration. Cells 2021; 10:cells10102726. [PMID: 34685706 PMCID: PMC8534876 DOI: 10.3390/cells10102726] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/06/2021] [Accepted: 10/07/2021] [Indexed: 02/06/2023] Open
Abstract
Proteins of the actin depolymerizing factor (ADF)/cofilin family are ubiquitous among eukaryotes and are essential regulators of actin dynamics and function. Mammalian neurons express cofilin-1 as the major isoform, but ADF and cofilin-2 are also expressed. All isoforms bind preferentially and cooperatively along ADP-subunits in F-actin, affecting the filament helical rotation, and when either alone or when enhanced by other proteins, promotes filament severing and subunit turnover. Although self-regulating cofilin-mediated actin dynamics can drive motility without post-translational regulation, cells utilize many mechanisms to locally control cofilin, including cooperation/competition with other proteins. Newly identified post-translational modifications function with or are independent from the well-established phosphorylation of serine 3 and provide unexplored avenues for isoform specific regulation. Cofilin modulates actin transport and function in the nucleus as well as actin organization associated with mitochondrial fission and mitophagy. Under neuronal stress conditions, cofilin-saturated F-actin fragments can undergo oxidative cross-linking and bundle together to form cofilin-actin rods. Rods form in abundance within neurons around brain ischemic lesions and can be rapidly induced in neurites of most hippocampal and cortical neurons through energy depletion or glutamate-induced excitotoxicity. In ~20% of rodent hippocampal neurons, rods form more slowly in a receptor-mediated process triggered by factors intimately connected to disease-related dementias, e.g., amyloid-β in Alzheimer’s disease. This rod-inducing pathway requires a cellular prion protein, NADPH oxidase, and G-protein coupled receptors, e.g., CXCR4 and CCR5. Here, we will review many aspects of cofilin regulation and its contribution to synaptic loss and pathology of neurodegenerative diseases.
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Affiliation(s)
- James R. Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
- Correspondence: ; Tel.: +1-970-988-9120; Fax: +1-970-491-0494
| | - Laurie S. Minamide
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
| | - O’Neil Wiggan
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
| | - Lubna H. Tahtamouni
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
- Department of Biology and Biotechnology, The Hashemite University, Zarqa 13115, Jordan
| | - Thomas B. Kuhn
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA; (L.S.M.); (O.W.); (L.H.T.); (T.B.K.)
- Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 99775, USA
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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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Biel N, Figard L, Sokac AM. Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos. J Vis Exp 2020. [PMID: 32478727 DOI: 10.3791/61297] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The purpose of this protocol is to visualize intranuclear actin rods that assemble in live Drosophila melanogaster embryos following heat stress. Actin rods are a hallmark of a conserved, inducible Actin Stress Response (ASR) that accompanies human pathologies, including neurodegenerative disease. Previously, we showed that the ASR contributes to morphogenesis failures and reduced viability of developing embryos. This protocol allows the continued study of mechanisms underlying actin rod assembly and the ASR in a model system that is highly amenable to imaging, genetics and biochemistry. Embryos are collected and mounted on a coverslip to prepare them for injection. Rhodamine-conjugated globular actin (G-actinRed) is diluted and loaded into a microneedle. A single injection is made into the center of each embryo. After injection, embryos are incubated at elevated temperature and intranuclear actin rods are then visualized by confocal microscopy. Fluorescence recovery after photobleaching (FRAP) experiments may be performed on the actin rods; and other actin-rich structures in the cytoplasm can also be imaged. We find that G-actinRed polymerizes like endogenous G-actin and does not, on its own, interfere with normal embryo development. One limitation of this protocol is that care must be taken during injection to avoid serious injury to the embryo. However, with practice, injecting G-actinRed into Drosophila embryos is a fast and reliable way to visualize actin rods and can easily be used with flies of any genotype or with the introduction of other cellular stresses, including hypoxia and oxidative stress.
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Affiliation(s)
- Natalie Biel
- Integrative Molecular and Biomedical Sciences, Baylor College of Medicine; Department of Cell and Molecular Biology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign
| | - Lauren Figard
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine
| | - Anna Marie Sokac
- Integrative Molecular and Biomedical Sciences, Baylor College of Medicine; Department of Cell and Molecular Biology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine;
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Purde V, Busch F, Kudryashova E, Wysocki VH, Kudryashov DS. Oligomerization Affects the Ability of Human Cyclase-Associated Proteins 1 and 2 to Promote Actin Severing by Cofilins. Int J Mol Sci 2019; 20:E5647. [PMID: 31718088 PMCID: PMC6888645 DOI: 10.3390/ijms20225647] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/07/2019] [Accepted: 11/08/2019] [Indexed: 02/03/2023] Open
Abstract
Actin-depolymerizing factor (ADF)/cofilins accelerate actin turnover by severing aged actin filaments and promoting the dissociation of actin subunits. In the cell, ADF/cofilins are assisted by other proteins, among which cyclase-associated proteins 1 and 2 (CAP1,2) are particularly important. The N-terminal half of CAP has been shown to promote actin filament dynamics by enhancing ADF-/cofilin-mediated actin severing, while the central and C-terminal domains are involved in recharging the depolymerized ADP-G-actin/cofilin complexes with ATP and profilin. We analyzed the ability of the N-terminal fragments of human CAP1 and CAP2 to assist human isoforms of "muscle" (CFL2) and "non-muscle" (CFL1) cofilins in accelerating actin dynamics. By conducting bulk actin depolymerization assays and monitoring single-filament severing by total internal reflection fluorescence (TIRF) microscopy, we found that the N-terminal domains of both isoforms enhanced cofilin-mediated severing and depolymerization at similar rates. According to our analytical sedimentation and native mass spectrometry data, the N-terminal recombinant fragments of both human CAP isoforms form tetramers. Replacement of the original oligomerization domain of CAPs with artificial coiled-coil sequences of known oligomerization patterns showed that the activity of the proteins is directly proportional to the stoichiometry of their oligomerization; i.e., tetramers and trimers are more potent than dimers, which are more effective than monomers. Along with higher binding affinities of the higher-order oligomers to actin, this observation suggests that the mechanism of actin severing and depolymerization involves simultaneous or consequent and coordinated binding of more than one N-CAP domain to F-actin/cofilin complexes.
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Affiliation(s)
- Vedud Purde
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; (V.P.); (F.B.); (E.K.); (V.H.W.)
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| | - Florian Busch
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; (V.P.); (F.B.); (E.K.); (V.H.W.)
- Resource for Native MS-Guided Structural Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; (V.P.); (F.B.); (E.K.); (V.H.W.)
| | - Vicki H. Wysocki
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; (V.P.); (F.B.); (E.K.); (V.H.W.)
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
- Resource for Native MS-Guided Structural Biology, The Ohio State University, Columbus, OH 43210, USA
- Campus Chemical Instrument Center, Mass Spectrometry and Proteomics, The Ohio State University, Columbus, OH 43210, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; (V.P.); (F.B.); (E.K.); (V.H.W.)
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
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Lu Z, Ma Y, Zhang Q, Zhao X, Zhang Y, Zhang L. Proteomic analyses of ram (Ovis aries) testis during different developmental stages. Anim Reprod Sci 2017; 189:93-102. [PMID: 29279200 DOI: 10.1016/j.anireprosci.2017.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 12/06/2017] [Accepted: 12/19/2017] [Indexed: 11/24/2022]
Abstract
Male reproductive capacity is essential for animal breeding and reproduction. In males, the testes produce sperm and secrete androgen, processes which require precise regulation by multiple proteins. The composition of proteins in the ram testes has not yet been studied systematically, thus, the application of proteomics to explore differential protein regulation during ram testes development is of great significance. In the present study, ram testes were studied at five different developmental phases to assess postnatal differences in protein regulation. Two dimensional electrophoresis (2-DE) was used to separate ram testes proteins at each developmental phase, yielding 45 different proteins, 37 of which were identified by Matrix Assisted Laser Desorption Ionization-Time of Flight-Time of Flight-Mass Spectrometry (MALDI-TOF/TOF-MS). Gene Ontology (GO) was used to specifically annotate the biological process, cellular composition, and molecular function of each identified protein. Most of the identified proteins were involved in structural formation, development, reproduction, and apoptosis of the testicular spermatogenic tissue and spermatozoa. Quantitative real time PCR (qRT-PCR), western blot and immunohistochemical methods were used to verify the proteins, and the results were consistent with that of 2-DE. The proteins that were different in abundance that were identified in this study can be used as biomarkers in future studies of ram reproduction.
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Affiliation(s)
- Zengkui Lu
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070, China; Engineering Laboratory of Sheep Breeding and Reproduction Biotechnology in Gansu Province, Minqin 733300, China
| | - Youji Ma
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070, China; Engineering Laboratory of Sheep Breeding and Reproduction Biotechnology in Gansu Province, Minqin 733300, China.
| | - Quanwei Zhang
- College of Life Science and Technology, Gansu Agricultural University, Lanzhou 730070, China
| | - Xingxu Zhao
- College of Veterinary Medicine, Gansu Agricultural University, Lanzhou 730070, China
| | - Yong Zhang
- College of Veterinary Medicine, Gansu Agricultural University, Lanzhou 730070, China
| | - Liping Zhang
- College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070, China
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Cofilin-1 and Other ADF/Cofilin Superfamily Members in Human Malignant Cells. Int J Mol Sci 2016; 18:ijms18010010. [PMID: 28025492 PMCID: PMC5297645 DOI: 10.3390/ijms18010010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 11/18/2016] [Accepted: 12/01/2016] [Indexed: 12/12/2022] Open
Abstract
Identification of actin-depolymerizing factor homology (ADF-H) domains in the structures of several related proteins led first to the formation of the ADF/cofilin family, which then expanded to the ADF/cofilin superfamily. This superfamily includes the well-studied cofilin-1 (Cfl-1) and about a dozen different human proteins that interact directly or indirectly with the actin cytoskeleton, provide its remodeling, and alter cell motility. According to some data, Cfl-1 is contained in various human malignant cells (HMCs) and is involved in the formation of malignant properties, including invasiveness, metastatic potential, and resistance to chemotherapeutic drugs. The presence of other ADF/cofilin superfamily proteins in HMCs and their involvement in the regulation of cell motility were discovered with the use of various OMICS technologies. In our review, we discuss the results of the study of Cfl-1 and other ADF/cofilin superfamily proteins, which may be of interest for solving different problems of molecular oncology, as well as for the prospects of further investigations of these proteins in HMCs.
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Girouard MP, Pool M, Alchini R, Rambaldi I, Fournier AE. RhoA Proteolysis Regulates the Actin Cytoskeleton in Response to Oxidative Stress. PLoS One 2016; 11:e0168641. [PMID: 27992599 PMCID: PMC5167403 DOI: 10.1371/journal.pone.0168641] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 12/05/2016] [Indexed: 11/24/2022] Open
Abstract
The small GTPase RhoA regulates the actin cytoskeleton to affect multiple cellular processes including endocytosis, migration and adhesion. RhoA activity is tightly regulated through several mechanisms including GDP/GTP cycling, phosphorylation, glycosylation and prenylation. Previous reports have also reported that cleavage of the carboxy-terminus inactivates RhoA. Here, we describe a novel mechanism of RhoA proteolysis that generates a stable amino-terminal RhoA fragment (RhoA-NTF). RhoA-NTF is detectable in healthy cells and tissues and is upregulated following cell stress. Overexpression of either RhoA-NTF or the carboxy-terminal RhoA cleavage fragment (RhoA-CTF) induces the formation of disorganized actin stress fibres. RhoA-CTF also promotes the formation of disorganized actin stress fibres and nuclear actin rods. Both fragments disrupt the organization of actin stress fibres formed by endogenous RhoA. Together, our findings describe a novel RhoA regulatory mechanism.
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Affiliation(s)
- Marie-Pier Girouard
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Rue University, Montréal, Québec, Canada
| | - Madeline Pool
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Rue University, Montréal, Québec, Canada
| | - Ricardo Alchini
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Rue University, Montréal, Québec, Canada
| | - Isabel Rambaldi
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Rue University, Montréal, Québec, Canada
| | - Alyson E. Fournier
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Rue University, Montréal, Québec, Canada
- * E-mail:
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Furgerson M, Clark JK, Crystal JD, Wagner JJ, Fechheimer M, Furukawa R. Hirano body expression impairs spatial working memory in a novel mouse model. Acta Neuropathol Commun 2014; 2:131. [PMID: 25178488 PMCID: PMC4160558 DOI: 10.1186/s40478-014-0131-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 08/15/2014] [Indexed: 11/29/2022] Open
Abstract
Introduction Hirano bodies are actin-rich intracellular inclusions found in the brains of patients with neurodegenerative conditions such as Alzheimer's disease or frontotemporal lobar degeneration-tau. While Hirano body ultrastructure and protein composition have been well studied, little is known about the physiological function of Hirano bodies in an animal model system. Results Utilizing a Cre/Lox system, we have generated a new mouse model which develops an age-dependent increase in the number of model Hirano bodies present in both the CA1 region of the hippocampus and frontal cortex. These mice develop normally and experience no overt neuron loss. Mice presenting model Hirano bodies have no abnormal anxiety or locomotor activity as measured by the open field test. However, mice with model Hirano bodies develop age-dependent impairments in spatial working memory performance assessed using a delayed win-shift task in an 8-arm radial maze. Synaptic transmission, short-term plasticity, and long-term plasticity was measured in the CA1 region from slices obtained from both the ventral and dorsal hippocampus in the same mice whose spatial working memory was assessed. Baseline synaptic responses, paired pulse stimulation and long-term potentiation measurements in the ventral hippocampus were indistinguishable from control mice. In contrast, in the dorsal hippocampus, synaptic transmission at higher stimulus intensities were suppressed in 3 month old mice with Hirano bodies as compared with control mice. In addition, long-term potentiation was enhanced in the dorsal hippocampus of 8 month old mice with Hirano bodies, concurrent with observed impairment of spatial working memory. Finally, an inflammatory response was observed at 8 months of age in mice with Hirano bodies as assessed by the presence of reactive astrocytes. Conclusion This study shows that the presence of model Hirano bodies initiates an inflammatory response, alters hippocampal synaptic responses, and impairs spatial working memory in an age-dependent manner. This suggests that Hirano bodies may promote disease progression. This new model mouse provides a tool to investigate how Hirano bodies interact with other pathologies associated with Alzheimer's disease. Hirano bodies likely play a complex and region specific role in the brain during neurodegenerative disease progression. Electronic supplementary material The online version of this article (doi:10.1186/s40478-014-0131-9) contains supplementary material, which is available to authorized users.
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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: 66] [Impact Index Per Article: 6.6] [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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Munsie LN, Desmond CR, Truant R. Cofilin nuclear-cytoplasmic shuttling affects cofilin-actin rod formation during stress. J Cell Sci 2012; 125:3977-88. [PMID: 22623727 DOI: 10.1242/jcs.097667] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Cofilin protein is involved in regulating the actin cytoskeleton during typical steady state conditions, as well as during cell stress conditions where cofilin saturates F-actin, forming cofilin-actin rods. Cofilin can enter the nucleus through an active nuclear localization signal (NLS), accumulating in nuclear actin rods during stress. Here, we characterize the active nuclear export of cofilin through a leptomycin-B-sensitive, CRM1-dependent, nuclear export signal (NES). We also redefine the NLS of cofilin as a bipartite NLS, with an additional basic epitope required for nuclear localization. Using fluorescence lifetime imaging microscopy (FLIM) and Förster resonant energy transfer (FRET) between cofilin moieties and actin, as well as automated image analysis in live cells, we have defined subtle mutations in the cofilin NLS that allow cofilin to bind actin in vivo and affect cofilin dynamics during stress. We further define the requirement of cofilin-actin rod formation in a system of cell stress by temporal live-cell imaging. We propose that cofilin nuclear shuttling is critical for the cofilin-actin rod stress response with cofilin dynamically communicating between the nucleus and cytoplasm during cell stress.
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Affiliation(s)
- Lise Nicole Munsie
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada, L8N 3Z5
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11
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Ravenscroft G, Jackaman C, Sewry CA, McNamara E, Squire SE, Potter AC, Papadimitriou J, Griffiths LM, Bakker AJ, Davies KE, Laing NG, Nowak KJ. Actin nemaline myopathy mouse reproduces disease, suggests other actin disease phenotypes and provides cautionary note on muscle transgene expression. PLoS One 2011; 6:e28699. [PMID: 22174871 PMCID: PMC3235150 DOI: 10.1371/journal.pone.0028699] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 11/14/2011] [Indexed: 01/13/2023] Open
Abstract
Mutations in the skeletal muscle α-actin gene (ACTA1) cause congenital myopathies including nemaline myopathy, actin aggregate myopathy and rod-core disease. The majority of patients with ACTA1 mutations have severe hypotonia and do not survive beyond the age of one. A transgenic mouse model was generated expressing an autosomal dominant mutant (D286G) of ACTA1 (identified in a severe nemaline myopathy patient) fused with EGFP. Nemaline bodies were observed in multiple skeletal muscles, with serial sections showing these correlated to aggregates of the mutant skeletal muscle α-actin-EGFP. Isolated extensor digitorum longus and soleus muscles were significantly weaker than wild-type (WT) muscle at 4 weeks of age, coinciding with the peak in structural lesions. These 4 week-old mice were ~30% less active on voluntary running wheels than WT mice. The α-actin-EGFP protein clearly demonstrated that the transgene was expressed equally in all myosin heavy chain (MHC) fibre types during the early postnatal period, but subsequently became largely confined to MHCIIB fibres. Ringbinden fibres, internal nuclei and myofibrillar myopathy pathologies, not typical features in nemaline myopathy or patients with ACTA1 mutations, were frequently observed. Ringbinden were found in fast fibre predominant muscles of adult mice and were exclusively MHCIIB-positive fibres. Thus, this mouse model presents a reliable model for the investigation of the pathobiology of nemaline body formation and muscle weakness and for evaluation of potential therapeutic interventions. The occurrence of core-like regions, internal nuclei and ringbinden will allow analysis of the mechanisms underlying these lesions. The occurrence of ringbinden and features of myofibrillar myopathy in this mouse model of ACTA1 disease suggests that patients with these pathologies and no genetic explanation should be screened for ACTA1 mutations.
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MESH Headings
- Actins/metabolism
- Animals
- Behavior, Animal
- Disease Models, Animal
- Gene Expression
- Green Fluorescent Proteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Muscle Contraction/physiology
- Muscle Fibers, Skeletal/pathology
- Muscle Fibers, Skeletal/ultrastructure
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscle, Skeletal/ultrastructure
- Myopathies, Nemaline/pathology
- Myopathies, Nemaline/physiopathology
- Myosin Heavy Chains/metabolism
- Phenotype
- Recombinant Fusion Proteins/metabolism
- Transgenes/genetics
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Affiliation(s)
- Gianina Ravenscroft
- Centre for Medical Research, The University of Western Australia, Western Australian Institute for Medical Research, Nedlands, Australia
- Physiology, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Perth, Australia
| | - Connie Jackaman
- Centre for Medical Research, The University of Western Australia, Western Australian Institute for Medical Research, Nedlands, Australia
| | - Caroline A. Sewry
- Wolfson Centre for Inherited Neuromuscular Diseases, Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry, United Kingdom
| | - Elyshia McNamara
- Centre for Medical Research, The University of Western Australia, Western Australian Institute for Medical Research, Nedlands, Australia
| | - Sarah E. Squire
- MRC Functional Genetics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Allyson C. Potter
- MRC Functional Genetics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - John Papadimitriou
- School of Pathology and Laboratory Medicine, The University of Western Australia, Perth, Australia
| | - Lisa M. Griffiths
- Neuropathology, Royal Perth Hospital and PathWest Anatomical Pathology, Perth, Australia
| | - Anthony J. Bakker
- Physiology, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Perth, Australia
| | - Kay E. Davies
- MRC Functional Genetics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Nigel G. Laing
- Centre for Medical Research, The University of Western Australia, Western Australian Institute for Medical Research, Nedlands, Australia
| | - Kristen J. Nowak
- Centre for Medical Research, The University of Western Australia, Western Australian Institute for Medical Research, Nedlands, Australia
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Tholl S, Moreau F, Hoffmann C, Arumugam K, Dieterle M, Moes D, Neumann K, Steinmetz A, Thomas C. Arabidopsis actin-depolymerizing factors (ADFs) 1 and 9 display antagonist activities. FEBS Lett 2011; 585:1821-7. [PMID: 21570971 DOI: 10.1016/j.febslet.2011.05.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 05/02/2011] [Accepted: 05/03/2011] [Indexed: 01/05/2023]
Abstract
We provide evidence that one of the 11 Arabidopsis actin-depolymerizing factors (ADFs), namely ADF9, does not display typical F-actin depolymerizing activity. Instead, ADF9 effectively stabilizes actin filaments in vitro and concomitantly bundles actin filaments with the highest efficiency under acidic conditions. Competition experiments show that ADF9 antagonizes ADF1 activity by reducing its ability to potentiate F-actin depolymerization. Accordingly, ectopic expression of ADF1 and ADF9 in tobacco cells has opposite effects. ADF1 severs actin filaments/bundles and promotes actin cytoskeleton disassembly, whereas ADF9 induces the formation of long bundles. Together these data reveal an additional degree of complexity in the comprehension of the biological functions of the ADF family and illustrate that antagonist activities can be displayed by seemingly equivalent actin-binding proteins.
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Affiliation(s)
- Stéphane Tholl
- Centre de Recherche Public-Santé, Luxembourg, Luxembourg
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13
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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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14
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Ravenscroft G, Wilmshurst JM, Pillay K, Sivadorai P, Wallefeld W, Nowak KJ, Laing NG. A novel ACTA1 mutation resulting in a severe congenital myopathy with nemaline bodies, intranuclear rods and type I fibre predominance. Neuromuscul Disord 2011; 21:31-6. [DOI: 10.1016/j.nmd.2010.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 07/30/2010] [Accepted: 08/23/2010] [Indexed: 01/27/2023]
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15
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Ono S. Dynamic regulation of sarcomeric actin filaments in striated muscle. Cytoskeleton (Hoboken) 2010; 67:677-92. [PMID: 20737540 PMCID: PMC2963174 DOI: 10.1002/cm.20476] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 07/21/2010] [Accepted: 07/29/2010] [Indexed: 01/08/2023]
Abstract
In striated muscle, the actin cytoskeleton is differentiated into myofibrils. Actin and myosin filaments are organized in sarcomeres and specialized for producing contractile forces. Regular arrangement of actin filaments with uniform length and polarity is critical for the contractile function. However, the mechanisms of assembly and maintenance of sarcomeric actin filaments in striated muscle are not completely understood. Live imaging of actin in striated muscle has revealed that actin subunits within sarcomeric actin filaments are dynamically exchanged without altering overall sarcomeric structures. A number of regulators for actin dynamics have been identified, and malfunction of these regulators often result in disorganization of myofibril structures or muscle diseases. Therefore, proper regulation of actin dynamics in striated muscle is critical for assembly and maintenance of functional myofibrils. Recent studies have suggested that both enhancers of actin dynamics and stabilizers of actin filaments are important for sarcomeric actin organization. Further investigation of the regulatory mechanism of actin dynamics in striated muscle should be a key to understanding how myofibrils develop and operate.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia 30322, USA.
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16
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Haigh SE, Salvi SS, Sevdali M, Stark M, Goulding D, Clayton JD, Bullard B, Sparrow JC, Nongthomba U. Drosophila indirect flight muscle specific Act88F actin mutants as a model system for studying congenital myopathies of the human ACTA1 skeletal muscle actin gene. Neuromuscul Disord 2010; 20:363-74. [DOI: 10.1016/j.nmd.2010.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 02/01/2010] [Accepted: 03/05/2010] [Indexed: 10/19/2022]
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17
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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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18
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Hofmann WA. Cell and molecular biology of nuclear actin. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 273:219-63. [PMID: 19215906 DOI: 10.1016/s1937-6448(08)01806-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Actin is a highly conserved protein and one of the major components of the cytoplasm and the nucleus in eukaryotic cells. In the nucleus, actin is involved in a variety of nuclear processes that include transcription and transcription regulation, RNA processing and export, intranuclear movement, and structure maintenance. Recent advances in the field of nuclear actin have established that functions of actin in the nucleus are versatile, complex, and interconnected. It also has become increasingly evident that the cytoplasmic and nuclear pools of actin are functionally linked. However, while the biological significance of nuclear actin has become clear, we are only beginning to understand the mechanisms that lie behind the regulation of nuclear actin. This review provides an overview of our current understanding of the functions of actin in the nucleus.
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Affiliation(s)
- Wilma A Hofmann
- Department of Physiology and Biophysics, State University of New York, Buffalo, NY, USA
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19
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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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Homma K, Niino Y, Hotta K, Oka K. Ca(2+) influx through P2X receptors induces actin cytoskeleton reorganization by the formation of cofilin rods in neurites. Mol Cell Neurosci 2007; 37:261-70. [PMID: 17993279 DOI: 10.1016/j.mcn.2007.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2006] [Revised: 09/12/2007] [Accepted: 10/01/2007] [Indexed: 01/15/2023] Open
Abstract
In physiological and pathological events, extracellular ATP plays an important role by controlling several types of purinergic receptors and changing cytoskeleton dynamics. To know the process of ATP-dependent cytoskeleton remodeling, we focused on cofilin, a key regulator of actin cytoskeleton, and investigated the dynamics of cofilin in PC12 cells through fluorescent protein-labeled cofilin and actin, Ca(2+) imaging, and fluorescence resonance energy transfer (FRET) techniques. As a result, ATP induced intracellular Ca(2+) increase, following cofilin rods' formation. ATP-induced cofilin rods' formation was not observed in cells expressing unphosphorylatable variant of cofilin. A P2X receptor agonist, but not P2Y, induced the formation of cofilin rods, whereas calmodulin and calcineurin inhibitors suppressed it. These results indicate that Ca(2+) influx through P2X receptors induces the formation of cofilin rods via calcineurin-dependent dephosphorylation of cofilin. This pathway might be one candidate to explain the effects of ATP on neuronal development and injury.
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Affiliation(s)
- Kohei Homma
- Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan.
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21
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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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22
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Phenotypes of myopathy-related actin mutants in differentiated C2C12 myotubes. BMC Cell Biol 2007; 8:2. [PMID: 17227580 PMCID: PMC1779783 DOI: 10.1186/1471-2121-8-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Accepted: 01/16/2007] [Indexed: 11/19/2022] Open
Abstract
Background About 20 % of nemaline myopathies are thus far related to skeletal muscle alpha-actin. Seven actin mutants located in different parts of the actin molecule and linked to different forms of the disease were selected and expressed as EGFP-tagged constructs in differentiated C2C12 mytoubes. Results were compared with phenotypes in patient skeletal muscle fibres and with previous expression studies in fibroblasts and C2C12 myoblasts/myotubes. Results Whereas EGFP wt-actin nicely incorporated into endogenous stress fibres and sarcomeric structures, the mutants showed a range of phenotypes, which generally changed upon differentiation. Many mutants appeared delocalized in myoblasts but integrated into endogenous actin structures after 4–6 days of differentiation, demonstrating a poor correlation between the appearance in myotubes and the severity of the disease. However, for some mutants, integration into stress fibres induced aberrant structures in differentiated cells, like thickening or fragmentation of stress fibres. Other mutants almost failed to integrate but formed huge aggregates in the cytoplasm of myotubes. Those did not co-stain with alpha-actinin, a main component of nemaline bodies found in patient muscle. Interestingly, nuclear aggregates as formed by two of the mutants in myoblasts were found less frequently or not at all in differentiated cells. Conclusion Myotubes are a suitable system to study the capacity of a mutant to incorporate into actin structures or to form or induce pathological changes. Some of the phenotypes observed in undifferentiated myoblasts may only be in vitro effects. Other phenotypes, like aberrant stress fibres or rod formation may be more directly correlated with disease phenotypes. Some mutants did not induce any changes in the cellular actin system, indicating the importance of additional studies like functional assays to fully characterize the pathological impact of a mutant.
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23
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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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24
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Muto M, Sargeant A, Tangkawattana P, Takeyasu K, Nishijima Y, Bonagura J, Hoshijima M, Nakade T, Hosaka Y, Faulkner G, Tomono K, Yamaguchi M. Intranuclear paracrystals observed in striated muscle specific LIM protein-deficient mouse cardiomyocytes. Microsc Res Tech 2006; 70:50-4. [PMID: 17094078 DOI: 10.1002/jemt.20386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A paracrystalline structure was observed within left ventricular cardiomyocyte nuclei of MLP(-/-) mice. The paracrystal possessed cross lines, approximately 8.0 micro m long and 0.3 micro m wide, with a slender spindle shape and a periodicity of 13 nm. Paracrystals were best observed along the longitudinal orientation of myofibrils and were detected in less than 10% of the nuclei observed. One dimension of the protein unit forming the paracrystal was 8.5 nm long. The electron density of the paracrystal appeared to be slightly higher than that of heterochromatin, suggesting that RNA-associated proteins are constituents of the paracrystal. This is the first report of intranuclear paracrystals in cardiomyocytes, which appear to be unique to MLP(-/-) mice.
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Affiliation(s)
- M Muto
- Department of Veterinary Surgery, Azabu University, Kanagawa, Japan
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25
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Song X, Chen X, Yamaguchi H, Mouneimne G, Condeelis JS, Eddy RJ. Initiation of cofilin activity in response to EGF is uncoupled from cofilin phosphorylation and dephosphorylation in carcinoma cells. J Cell Sci 2006; 119:2871-81. [PMID: 16803871 DOI: 10.1242/jcs.03017] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It has been demonstrated that the actin-severing activity of cofilin can be downregulated by LIM kinase (LIMK)-dependent phosphorylation at residue Ser3. Chemotactic stimulation in various cell types induces cofilin dephosphorylation, suggesting that cofilin activation in these cells occurs by a dephosphorylation mechanism. However, resting metastatic carcinoma cells have the majority of their cofilin in a dephosphorylated but largely inactive state. Stimulation with epidermal growth factor (EGF) induces an increase in cofilin activity after 60 seconds together with an increase in phosphorylated cofilin (p-cofilin), indicating that cofilin dephosphorylation is not coupled to cofilin activation in these cells. Suppression of LIMK function by inhibiting Rho-associated protein kinase (ROCK) or LIMK siRNA inhibited the EGF-induced cofilin phosphorylation but had no effect on cofilin activity or cofilin-dependent lamellipod protrusion induced by EGF. Correlation analysis revealed that cofilin, p-cofilin and LIMK are not colocalized, and changes in the location of these proteins upon stimulation with EGF indicate that they are not functionally coupled. Phospholipase C, which has been implicated in cofilin activation following stimulation with EGF, does not regulate p-cofilin levels following stimulation with EGF. Therefore, our results do not support a model for the initial activation of cofilin by dephosphorylation in response to chemoattractant stimulation in metastatic carcinoma cells.
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Affiliation(s)
- Xiaoyan Song
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, F628, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
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26
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Kudryashov DS, Galkin VE, Orlova A, Phan M, Egelman EH, Reisler E. Cofilin cross-bridges adjacent actin protomers and replaces part of the longitudinal F-actin interface. J Mol Biol 2006; 358:785-97. [PMID: 16530787 DOI: 10.1016/j.jmb.2006.02.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2005] [Revised: 01/22/2006] [Accepted: 02/13/2006] [Indexed: 11/25/2022]
Abstract
ADF/cofilins are abundant actin binding proteins critical to the survival of eukaryotic cells. Most ADF/cofilins bind both G and F-actin, sever the filaments and accelerate their treadmilling. These effects are linked to rearrangements of interprotomer contacts, changes in the mean twist, and filament destabilization by ADF/cofilin. Paradoxically, it was reported that under certain in vitro and in vivo conditions cofilin may stabilize actin filaments and nucleate their formation. Here, we show that yeast cofilin and human muscle cofilin (cofilin-2) accelerate the nucleation and elongation of ADP-F-actin and stabilize such filaments. Moreover, cofilin rescues the polymerization of the assembly incompetent tethramethyl rhodamine (TMR)-actin and T203C/C374S yeast mutant actin. Filaments of cofilin-decorated TMR-actin and unlabeled actin are indistinguishable, as revealed by electron microscopy and three-dimensional reconstruction. Our data suggest that ADF/cofilins play an active role in establishing new interprotomer interfaces in F-actin that substitute for disrupted (as in TMR-actin and mutant actin) or weakened (as in ADP-actin) longitudinal contacts in filaments.
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Affiliation(s)
- D S Kudryashov
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA.
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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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28
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Ghosh M, Song X, Mouneimne G, Sidani M, Lawrence DS, Condeelis JS. Cofilin promotes actin polymerization and defines the direction of cell motility. Science 2004; 304:743-6. [PMID: 15118165 DOI: 10.1126/science.1094561] [Citation(s) in RCA: 519] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A general caging method for proteins that are regulated by phosphorylation was used to study the in vivo biochemical action of cofilin and the subsequent cellular response. By acute and local activation of a chemically engineered, light-sensitive phosphocofilin mimic, we demonstrate that cofilin polymerizes actin, generates protrusions, and determines the direction of cell migration. We propose a role for cofilin that is distinct from its role as an actin-depolymerizing factor.
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Affiliation(s)
- Mousumi Ghosh
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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29
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Johnson N, Krebs M, Boudreau R, Giorgi G, LeGros M, Larabell C. Actin-filled nuclear invaginations indicate degree of cell de-differentiation. Differentiation 2003; 71:414-24. [PMID: 12969334 DOI: 10.1046/j.1432-0436.2003.7107003.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
For years the existence of nuclear actin has been heavily debated, but recent data have clearly demonstrated that actin, as well as actin-binding proteins (ABPs), are located in the nucleus. We examined live EGFP-actin-expressing cells using confocal microscopy and saw the presence of structures strongly resembling actin filaments in the nuclei of MDA-MB-231 human mammary epithelial tumor cells. Many nuclei had more than one of these filamentous structures, some of which appeared to cross the entire nucleus. Extensive analysis, including fluorescence recovery after photobleaching (FRAP), showed that all EGFP-actin in the nucleus is monomeric (G-actin) rather than filamentous (F-actin) and that the apparent filaments seen in the nucleus are invaginations of cytoplasmic monomeric actin. Immunolocalization of nuclear pore complex proteins shows that similar invaginations are seen in cells that are not overexpressing EGFP-actin. To determine whether there is a correlation between increased levels of invagination in the cell nuclei and the state of de-differentiation of the cell, we examined a variety of cell types, including live Xenopus embryonic cells. Cells that were highly de-differentiated, or cancerous, had an increased incidence of invagination, while cells that were differentiated had few nuclear invaginations. The nuclei of embryonic cells that were not yet differentiated underwent multiple shape changes throughout interphase, and demonstrated numerous transient invaginations of varying sizes and shapes. Although the function of these actin-filled invaginations remains speculative, their presence correlates with cells that have increased levels of nuclear activity.
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Affiliation(s)
- Nicole Johnson
- Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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30
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Maselli A, Furukawa R, Thomson SAM, Davis RC, Fechheimer M. Formation of Hirano bodies induced by expression of an actin cross-linking protein with a gain-of-function mutation. EUKARYOTIC CELL 2003; 2:778-87. [PMID: 12912897 PMCID: PMC178389 DOI: 10.1128/ec.2.4.778-787.2003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2002] [Accepted: 04/22/2003] [Indexed: 11/20/2022]
Abstract
Hirano bodies are paracrystalline actin filament-containing structures reported to be associated with a variety of neurodegenerative diseases. However, the biological function of Hirano bodies remains poorly understood, since nearly all prior studies of these structures were done with postmortem samples of tissue. In the present study, we generated a full-length form of a Dictyostelium 34-kDa actin cross-linking protein with point mutations in the first putative EF hand, termed 34-kDa DeltaEF1. The 34-kDa DeltaEF1 protein binds calcium normally but has activated actin binding that is unregulated by calcium. The expression of the 34-kDa DeltaEF1 protein in Dictyostelium induces the formation of Hirano bodies, as assessed by both fluorescence microscopy and transmission electron microscopy. Dictyostelium cells bearing Hirano bodies grow normally, indicating that Hirano bodies are not associated with cell death and are not deleterious to cell growth. Moreover, the expression of the 34-kDa DeltaEF1 protein rescues the phenotypes of cells lacking the 34-kDa protein and cells lacking both the 34-kDa protein and alpha-actinin. Finally, the expression of the 34-kDa DeltaEF1 protein also initiates the formation of Hirano bodies in cultured mouse fibroblasts. These results show that the failure to regulate the activity and/or affinity of an actin cross-linking protein can provide a signal for the formation of Hirano bodies. More generally, the formation of Hirano bodies is a cellular response to or a consequence of aberrant function of the actin cytoskeleton.
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Affiliation(s)
- Andrew Maselli
- Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, USA
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Ono K, Parast M, Alberico C, Benian GM, Ono S. Specific requirement for two ADF/cofilin isoforms in distinct actin-dependent processes in Caenorhabditis elegans. J Cell Sci 2003; 116:2073-85. [PMID: 12679387 DOI: 10.1242/jcs.00421] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Actin depolymerizing factor (ADF)/cofilin is an essential enhancer of actin turnover. Multicellular organisms express multiple ADF/cofilin isoforms in different patterns of tissue distribution. However, the functional significance of different ADF/cofilin isoforms is not understood. The Caenorhabditis elegans unc-60 gene generates two ADF/cofilins, UNC-60A and UNC-60B, by alternative splicing. These two ADF/cofilin proteins have different effects on actin dynamics in vitro, but their functional difference in vivo remains unclear. Here, we demonstrate that the two isoforms are expressed in different tissues and are required for distinct morphogenetic processes. UNC-60A was ubiquitously expressed in most embryonic cells and enriched in adult gonads, intestine and oocytes. In contrast, UNC-60B was specifically expressed in the body wall muscle, vulva and spermatheca. RNA interference of UNC-60A caused embryonic lethality with variable defects in cytokinesis and developmental patterning. In severely affected embryos, a cleavage furrow was formed and progressed but reversed before completion of the cleavage. Also, in some affected embryos, positioning of the blastomeres became abnormal, which resulted in embryonic arrest. In contrast, an unc-60B-null mutant was homozygous viable, underwent normal early embryogenesis and caused disorganization of actin filaments specifically in body wall muscle. These results suggest that the ADF/cofilin isoforms play distinct roles in specific aspects of actin reorganization in vivo.
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Affiliation(s)
- Kanako Ono
- Department of Pathology, Emory University, Whitehead IO5N, Atlanta, Georgia 30322, USA
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Maselli AG, Davis R, Furukawa R, Fechheimer M. Formation of Hirano bodies in Dictyostelium and mammalian cells induced by expression of a modified form of an actin-crosslinking protein. J Cell Sci 2002; 115:1939-49. [PMID: 11956325 DOI: 10.1242/jcs.115.9.1939] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the serendipitous development of the first cultured cell models of Hirano bodies. Myc-epitope-tagged forms of the 34 kDa actin bundling protein (amino acids 1-295) and the CT fragment (amino acids 124-295) of the 34 kDa protein that exhibits activated actin binding and calcium-insensitive actin filament crosslinking activity were expressed in Dictyosteliumand mammalian cells to assess the behavior of these modified forms in vivo. Dictyostelium cells expressing the CT-myc fragment: (1) form ellipsoidal regions that contain ordered assemblies of F-actin, CT-myc, myosin II, cofilin and α-actinin; (2) grow and develop more slowly than wildtype, but produce normal morphogenetic structures; (3) perform pinocytosis and phagocytosis normally; and (4) produce a level of total actin equivalent to wildtype, but a higher level of F-actin. The paracrystalline inclusions bear a striking resemblance to Hirano bodies, which are associated with a number of pathological conditions. Furthermore, expression of the CT fragment in murine L cells results in F-actin rearrangements characterized by loss of stress fibers, accumulation of numerous punctate foci, and large perinuclear aggregates, the Hirano bodies. Thus, failure to regulate the activity and/or affinity of an actin crosslinking protein can provide a signal for formation of Hirano bodies. More generally, formation of Hirano bodies is a cellular response to or a consequence of aberrant function of the actin cytoskeleton. The results reveal that formation of Hirano bodies is not necessarily related to cell death. These cultured cell models should facilitate studies of the biochemistry, genetics and physiological effects of Hirano bodies.
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Affiliation(s)
- Andrew G Maselli
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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33
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Weins A, Schwarz K, Faul C, Barisoni L, Linke WA, Mundel P. Differentiation- and stress-dependent nuclear cytoplasmic redistribution of myopodin, a novel actin-bundling protein. J Cell Biol 2001; 155:393-404. [PMID: 11673475 PMCID: PMC2150840 DOI: 10.1083/jcb.200012039] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
We report the cloning and functional characterization of myopodin, the second member of the synaptopodin gene family. Myopodin shows no significant homology to any known protein except synaptopodin. Northern blot analysis resulted in a 3.6-kb transcript for mouse skeletal and heart muscle. Western blots showed an 80-kD signal for skeletal and a 95-kD signal for heart muscle. Myopodin contains one PPXY motif and multiple PXXP motifs. Myopodin colocalizes with alpha-actinin and is found at the Z-disc as shown by immunogold electron microscopy. In myoblasts, myopodin shows preferential nuclear localization. During myotube differentiation, myopodin binds to stress fibers in a punctuated pattern before incorporation into the Z-disc. Myopodin can directly bind to actin and contains a novel actin binding site in the center of the protein. Myopodin has actin-bundling activity as shown by formation of latrunculin-A-sensitive cytosolic actin bundles and nuclear actin loops in transfected cells expressing green fluorescent protein-myopodin. Under stress conditions, myopodin accumulates in the nucleus and is depleted from the cytoplasm. Nuclear export of myopodin is sensitive to leptomycin B, despite the absence of a classical nuclear export sequence. We propose a dual role for myopodin as a structural protein also participating in signaling pathways between the Z-disc and the nucleus.
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Affiliation(s)
- A Weins
- Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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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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Abstract
Ubiquitous among eukaryotes, the ADF/cofilins are essential proteins responsible for the high turnover rates of actin filaments in vivo. In vertebrates, ADF and cofilin are products of different genes. Both bind to F-actin cooperatively and induce a twist in the actin filament that results in the loss of the phalloidin-binding site. This conformational change may be responsible for the enhancement of the off rate of subunits at the minus end of ADF/cofilin-decorated filaments and for the weak filament-severing activity. Binding of ADF/cofilin is competitive with tropomyosin. Other regulatory mechanisms in animal cells include binding of phosphoinositides, phosphorylation by LIM kinases on a single serine, and changes in pH. Although vertebrate ADF/cofilins contain a nuclear localization sequence, they are usually concentrated in regions containing dynamic actin pools, such as the leading edge of migrating cells and neuronal growth cones. ADF/cofilins are essential for cytokinesis, phagocytosis, fluid phase endocytosis, and other cellular processes dependent upon actin dynamics.
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Affiliation(s)
- J R Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA.
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Meijerman I, Blom WM, de Bont HJ, Mulder GJ, Nagelkerke JF. Changes of G-actin localisation in the mitotic spindle region or nucleus during mitosis and after heat shock: a histochemical study of G-actin in various cell lines with fluorescent labelled vitamin D-binding protein. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1452:12-24. [PMID: 10525156 DOI: 10.1016/s0167-4889(99)00119-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The presence and localisation of G-actin in various cell lines was studied using the highly G-actin specific, fluorescence-labelled vitamin D-binding protein. In various cell-types, pig kidney-derived cells (LLC-PK1), Chinese hamster ovary (CHO) cells, SV-40 transformed African green monkey kidney (COS) cells and human hepatoma (HepG2) cells, G-actin was only visible in the cytoplasm of interphase cells. However, in mitotic cells, depending on the mitotic phase, intense G-actin staining was found associated with the mitotic spindle (early mitosis) or overlapping the DNA-staining pattern (late mitosis). Also after heat shock (60-180 min at 43 degrees C), an intense nuclear staining of G-actin was observed. In LLC-PK1 cells, the increase of nuclear G-actin staining disappeared again after 24 h at 37 degrees C, but in COS, CHO and HepG2 cells, it was still present in the nucleus after 24 h at 37 degrees C, indicating that the process was not rapidly reversible in these cells; the increased nuclear G-actin was not associated with cell division. Comparison of the amount of G-actin present in the nucleus and in the cytosol before and after heat shock using Western blotting demonstrated that the total amount of G-actin in both nucleus and cytosol was unchanged after heat shock. This indicates that the increased G-actin staining is not a result of import of G-actin into the nucleus. These observations suggest a rearrangement of G-actin in the nucleus during both mitosis and heat shock, which may be due to changes in interaction of G-actin with chromosomes.
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Affiliation(s)
- I Meijerman
- Division of Toxicology, Sylvius Laboratories, PO Box 9503, Leiden-Amsterdam Centre for Drug Research, Leiden University, 2300 RA, Leiden, Netherlands
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Abstract
The actin-depolymerizing factor (ADF)/cofilins are a family of essential actin regulatory proteins, ubiquitous among eukaryotes, that enhance the turnover of actin by regulating the rate constants of polymerization and depolymerization at filament ends, changing the twist of the filament and severing actin filaments. Genetic and cell-biological studies have shown that an ADF/cofilin is required to drive the high turnover of the actin cytoskeleton observed in vivo. The activity of ADF/cofilin is regulated by a variety of mechanisms, including specific phosphorylation and dephosphorylation. This review addresses aspects of ADF/cofilin structure, dynamics, regulation and function.
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Affiliation(s)
- J R Bamburg
- Dept of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
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38
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Ono S, Baillie DL, Benian GM. UNC-60B, an ADF/cofilin family protein, is required for proper assembly of actin into myofibrils in Caenorhabditis elegans body wall muscle. J Cell Biol 1999; 145:491-502. [PMID: 10225951 PMCID: PMC2185080 DOI: 10.1083/jcb.145.3.491] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Caenorhabditis elegans unc-60 gene encodes two functionally distinct isoforms of ADF/cofilin that are implicated in myofibril assembly. Here, we show that one of the gene products, UNC-60B, is specifically required for proper assembly of actin into myofibrils. We found that all homozygous viable unc-60 mutations resided in the unc-60B coding region, indicating that UNC-60B is responsible for the Unc-60 phenotype. Wild-type UNC-60B had F-actin binding, partial actin depolymerizing, and weak F-actin severing activities in vitro. However, mutations in UNC-60B caused various alterations in these activities. Three missense mutations resulted in weaker F-actin binding and actin depolymerizing activities and complete loss of severing activity. The r398 mutation truncated three residues from the COOH terminus and resulted in the loss of severing activity and greater actin depolymerizing activity. The s1307 mutation in a putative actin-binding helix caused greater activity in actin-depolymerizing and severing. Using a specific antibody for UNC-60B, we found varying protein levels of UNC-60B in mutant animals, and that UNC-60B was expressed in embryonic muscles. Regardless of these various molecular phenotypes, actin was not properly assembled into embryonic myofibrils in all unc-60 mutants to similar extents. We conclude that precise control of actin filament dynamics by UNC-60B is required for proper integration of actin into myofibrils.
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Affiliation(s)
- S Ono
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia 30322, USA.
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39
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Coumans JV, dos Remedios CG. Actin-binding proteins in mouse C2 myoblasts and myotubes: a combination of affinity chromatography and two-dimensional gel electrophoresis. Electrophoresis 1998; 19:826-33. [PMID: 9629922 DOI: 10.1002/elps.1150190537] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This paper analyzes proteins expressed in a mouse muscle precursor cell line (C2 myoblasts) and compares them with those observed in differentiated myotubes from the same cell line. We observed hundreds of proteins in myoblasts using IPG two-dimensional gel electrophoresis but this number is greatly reduced using Mini-Leak (divinylsulfone-activated agarose) affinity chromatography. Two kinds of affinity columns were prepared. One contained a chemically modified monomeric actin bound to the affinity matrix. The second matrix contained a high-affinity actin-binding protein (DNase I) which was bound to the actin Mini-Leak column to block specific sites on actin. Actin-binding proteins in homogenates of myoblasts or myotubes were passed through the affinity columns and eluted under high salt conditions. The Mini-Leak affinity medium itself appeared to have little ability to bind proteins. Our two-dimensional (2-D) gels identified a small number of proteins and we are currently focusing our attention on a particular protein spot which could correspond to cofilin. Comparison of myoblast and myotube proteins using affinity chromatography shows no qualitative, clearly identifiable differences but the analysis is still in progress. These findings are discussed in relation to reports in which the myoblast-myotube transformation was associated with the up-regulation or de novo synthesis of more than ten proteins.
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Affiliation(s)
- J V Coumans
- Institute for Biomedical Research, Department of Anatomy and Histology, The University of Sydney, Australia.
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40
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Minamide LS, Painter WB, Schevzov G, Gunning P, Bamburg JR. Differential regulation of actin depolymerizing factor and cofilin in response to alterations in the actin monomer pool. J Biol Chem 1997; 272:8303-9. [PMID: 9079652 DOI: 10.1074/jbc.272.13.8303] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Myoblasts, transfected with a human gene encoding a beta-actin point mutation, down-regulate expression of actin depolymerizing factor (ADF) and its mRNA. Regulation is posttranscriptional. Expression of cofilin, a structurally similar protein, and profilin, CapG, and tropomodulin is not altered with increasing mutant beta-actin expression. Myoblasts expressing either human gamma-actin or the mutant beta-actin down-regulate the endogenous mouse actin genes to keep a constant level of actin mRNA, whereas the gamma-actin transfectants do not down-regulate ADF. Thus, ADF expression is regulated differently from actin expression. The mutant beta-actin binds to ADF with about the same affinity as normal actin; however, it does not assemble into normal actin filaments. The decrease in ADF expression correlates with an increase in the unassembled actin pool. When the actin monomer pool in untransfected myoblasts is increased 70% by treatment with latrunculin A, synthesis of ADF and actin are down-regulated compared with cofilin and 19 other proteins selected at random. Increasing the actin monomer pool also results in nearly complete phosphorylation of both ADF and cofilin. Thus, ADF and cofilin are coordinately regulated by posttranslational modification, but their expression is differentially regulated. Furthermore, expression of ADF is responsive to the utilization of actin by the cell.
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Affiliation(s)
- L S Minamide
- Department of Biochemistry and Molecular Biology and the Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado 80523, USA
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41
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Rosenblatt J, Agnew BJ, Abe H, Bamburg JR, Mitchison TJ. Xenopus actin depolymerizing factor/cofilin (XAC) is responsible for the turnover of actin filaments in Listeria monocytogenes tails. J Cell Biol 1997; 136:1323-32. [PMID: 9087446 PMCID: PMC2132508 DOI: 10.1083/jcb.136.6.1323] [Citation(s) in RCA: 193] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/1996] [Revised: 12/12/1996] [Indexed: 02/04/2023] Open
Abstract
In contrast to the slow rate of depolymerization of pure actin in vitro, populations of actin filaments in vivo turn over rapidly. Therefore, the rate of actin depolymerization must be accelerated by one or more factors in the cell. Since the actin dynamics in Listeria monocytogenes tails bear many similarities to those in the lamellipodia of moving cells, we have used Listeria as a model system to isolate factors required for regulating the rapid actin filament turnover involved in cell migration. Using a cell-free Xenopus egg extract system to reproduce the Listeria movement seen in a cell, we depleted candidate depolymerizing proteins and analyzed the effect that their removal had on the morphology of Listeria tails. Immunodepletion of Xenopus actin depolymerizing factor (ADF)/cofilin (XAC) from Xenopus egg extracts resulted in Listeria tails that were approximately five times longer than the tails from undepleted extracts. Depletion of XAC did not affect the tail assembly rate, suggesting that the increased tail length was caused by an inhibition of actin filament depolymerization. Immunodepletion of Xenopus gelsolin had no effect on either tail length or assembly rate. Addition of recombinant wild-type XAC or chick ADF protein to XAC-depleted extracts restored the tail length to that of control extracts, while addition of mutant ADF S3E that mimics the phosphorylated, inactive form of ADF did not reduce the tail length. Addition of excess wild-type XAC to Xenopus egg extracts reduced the length of Listeria tails to a limited extent. These observations show that XAC but not gelsolin is essential for depolymerizing actin filaments that rapidly turn over in Xenopus extracts. We also show that while the depolymerizing activities of XAC and Xenopus extract are effective at depolymerizing normal filaments containing ADP, they are unable to completely depolymerize actin filaments containing AMPPNP, a slowly hydrolyzible ATP analog. This observation suggests that the substrate for XAC is the ADP-bound subunit of actin and that the lifetime of a filament is controlled by its nucleotide content.
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Affiliation(s)
- J Rosenblatt
- Department of Biochemistry, University of California, San Francisco 94143, USA
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42
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Agnew BJ, Minamide LS, Bamburg JR. Reactivation of phosphorylated actin depolymerizing factor and identification of the regulatory site. J Biol Chem 1995; 270:17582-7. [PMID: 7615564 DOI: 10.1074/jbc.270.29.17582] [Citation(s) in RCA: 290] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Actin depolymerizing factor (ADF) occurs naturally in two forms, one of which contains a phosphorylated Ser and does not bind G-actin or depolymerize F-actin. Removal of this phosphate in vitro by alkaline phosphatase restores full F-actin depolymerizing activity. To identify the phosphorylation site, [32P]pADF was purified and digested with endoproteinase Lys-C. The digest contained only one 32P-labeled peptide. Further digestion with endoproteinase Asp-N and mass spectrometric analysis showed that this peptide came from the N terminus of ADF. Alkaline phosphatase treatment of one Asp-N peptide (mass 753) converted it to a peptide of mass 673, demonstrating that this peptide contains the phosphate group. Tandem mass spectrometric sequence analysis of this peptide identified the phosphorylated Ser as the encoded Ser3 (Ser2 in the processed protein). HeLa cells, transfected with either chick wild-type ADF cDNA or a cDNA mutated to code for Ala in place of Ser24 or Thr25, express and phosphorylate the exogenous ADF. Cells also expressed high levels of mutant ADF when Ser3 was deleted or converted to either Ala or Glu. However, none of these mutants was phosphorylated, confirming that Ser3 in the encoded ADF is the single in vivo regulatory site.
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Affiliation(s)
- B J Agnew
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA
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Nagaoka R, Kusano K, Abe H, Obinata T. Effects of cofilin on actin filamentous structures in cultured muscle cells. Intracellular regulation of cofilin action. J Cell Sci 1995; 108 ( Pt 2):581-93. [PMID: 7769003 DOI: 10.1242/jcs.108.2.581] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The previous investigation (Abe et al. (1989) J. Biochem. 106, 696–702) suggested that cofilin is deeply involved in the regulation of actin assembly in developing skeletal muscle. In this study, to examine further the function of cofilin in living myogenic cells in culture, recombinant cofilin having extra Cys residues at the N terminus was produced in Escherichia coli and was labeled with tetramethylrhodamine-iodoacetamide (IATMR). When the cofilin labeled with IATMR (IATMR-cofilin) was introduced into myogenic cells, actin filaments in the cytoplasm or nascent myofibrils were promptly disrupted, and many cytoplasmic rods which contained both IATMR-cofilin and actin were generated. Sarcomeric myofibrillar structures were not disrupted but tropomyosin was dissociated from the structures by the exogenous cofilin, and the IATMR-cofilin became localized in I-band regions. 24 hours after the injection, however, the actin-cofilin rods disappeared completely and the IATMR-cofilin became diffused in the cytoplasm as endogenous cofilin. Concomitantly, actin filaments were recovered and tropomyosin was re-associated with sarcomeric I-bands. At this point, the IATMR-cofilin in the cells still retained the functional activity to form intranuclear actin-cofilin rods in response to stimulation by DMSO just as endogenous cofilin. FITC-labeled actin introduced into myogenic cells at first failed to assemble into filamentous structures in the presence of the exogenous cofilin, but was gradually incorporated into myofibrils with time. The drastic effects of the exogenous cofilin on actin assembly were suppressed by phosphatidylinositol 4,5-bisphosphate (PIP2). These results indicate that the exogenous cofilin is active and alters actin dynamics remarkably in muscle cells, but its activity in the cytoplasm gradually becomes regulated by the action of some factors including PIP2-binding.
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Affiliation(s)
- R Nagaoka
- Department of Biology, Faculty of Science, Chiba University, Japan
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44
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Davidson MM, Haslam RJ. Dephosphorylation of cofilin in stimulated platelets: roles for a GTP-binding protein and Ca2+. Biochem J 1994; 301 ( Pt 1):41-7. [PMID: 8037689 PMCID: PMC1137140 DOI: 10.1042/bj3010041] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In human platelets, thrombin not only stimulates the phosphorylation of pleckstrin (P47) and of myosin P-light chains, but also induces the dephosphorylation of an 18-19 kDa phosphoprotein (P18) [Imaoka, Lynham and Haslam (1983) J. Biol. Chem. 258, 11404-11414]. We have now studied this protein in detail. The thrombin-induced dephosphorylation reaction did not begin until the phosphorylation of myosin P-light chains and the secretion of dense-granule 5-hydroxytryptamine were nearly complete, but did parallel the later stages of platelet aggregation. Experiments with ionophore A23187 and phorbol 12-myristate 13-acetate indicated that dephosphorylation of P18 was stimulated by Ca2+, but not by protein kinase C. Two-dimensional analysis of platelet proteins, using non-equilibrium pH gradient electrophoresis followed by SDS/PAGE, showed that thrombin decreased the amount of phosphorylated P18 in platelets by up to 70% and slightly increased the amount of a more basic unlabelled protein that was present in 3-fold excess of P18 in unstimulated platelets. These two proteins were identified as the phosphorylated and non-phosphorylated forms of the pH-sensitive actin-depolymerizing protein, cofilin, by sequencing of peptide fragments and immunoblotting with a monoclonal antibody specific for cofilin. The molar concentration of cofilin in platelets was approx. 10% that of actin. Platelet cofilin was phosphorylated exclusively on serine. Experiments with electropermeabilized platelets showed that dephosphorylation of cofilin could be stimulated by guanosine 5'-[gamma-thio]triphosphate (GTP[S]) in the absence of Ca2+ or by a free Ca2+ concentration of 10 microM. This GTP[S]-induced dephosphorylation reaction was inhibited by 1-naphthyl phosphate, but not by okadaic acid. Our results add cofilin to the actin-binding proteins that may regulate the platelet cytoskeleton, and suggest that platelet cofilin can be activated by dephosphorylation reactions initiated either by a GTP-binding protein or Ca2+.
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Affiliation(s)
- M M Davidson
- Department of Pathology, McMaster University, Hamilton, Ontario, Canada
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45
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Characterization of a novel cofilin isoform that is predominantly expressed in mammalian skeletal muscle. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36603-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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46
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Hayden SM, Miller PS, Brauweiler A, Bamburg JR. Analysis of the interactions of actin depolymerizing factor with G- and F-actin. Biochemistry 1993; 32:9994-10004. [PMID: 8399168 DOI: 10.1021/bi00089a015] [Citation(s) in RCA: 177] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Chick actin depolymerizing factor (ADF) is an actin binding protein previously shown to rapidly depolymerize actin filaments in vitro, yielding a 1:1 complex of ADF and actin monomer. Here we show that ADF protects actin monomer from denaturation by EDTA by inhibiting the exchange of actin-bound nucleotide. Under low ionic strength conditions, the approximate dissociation constant (KD) for the ADF-actin complex determined from exchange of nucleotide (1,N6-etheno-ATP) is about 150 and is calcium-independent. Addition of ADF to monomeric actin inhibits actin assembly as well as the ATP hydrolysis that normally accompanies assembly. Complex formation is demonstrated between ADF and actin containing either ATP, ADP, or AMPPNP as the bound nucleotide. A KD of 0.1-0.2 microM was calculated for both the ADF-ATP-actin and ADF-AMPPNP-actin complexes, whereas the KD for the ADF-ADP-actin complex is about 1.3 microM. ADF can either depolymerize or cosediment with F-actin in a stoichiometric fashion, but these reciprocal activities are pH-dependent. At pHs between 6.5 and 7.1, ADF cosediments with F-actin and demonstrates only weak depolymerizing activity. ADF binding is cooperative and saturates at a 1:1 ADF:actin molar ratio. At pHs between 7.1 and 7.7, ADF shows increasing depolymerizing activity and less F-actin binding. At pH 8.0, ADF depolymerizes F-actin in a stoichiometric manner. Both the F-actin binding and the depolymerizing activities of ADF are inhibited by phalloidin.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S M Hayden
- Department of Biochemistry, Colorado State University, Fort Collins 80523
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Morgan TE, Lockerbie RO, Minamide LS, Browning MD, Bamburg JR. Isolation and characterization of a regulated form of actin depolymerizing factor. J Cell Biol 1993; 122:623-33. [PMID: 7687605 PMCID: PMC2119666 DOI: 10.1083/jcb.122.3.623] [Citation(s) in RCA: 147] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Actin depolymerizing factor (ADF) is an 18.5-kD protein with pH-dependent reciprocal F-actin binding and severing/depolymerizing activities. We previously showed developing muscle down-regulates ADF (J. R. Bamburg and D. Bray. 1987. J. Cell Biol. 105: 2817-2825). To further study this process, we examined ADF expression in chick myocytes cultured in vitro. Surprisingly, ADF immunoreactivity increases during the first 7-10 d in culture. This increase is due to the presence of a new ADF species with higher relative molecular weight which reacts identically to brain ADF with antisera raised against either brain ADF or recombinant ADF. We have purified both ADF isoforms from myocytes and have shown by peptide mapping and partial sequence analysis that the new isoform is structurally related to ADF. Immunoprecipitation of both isoforms from extracts of cells prelabeled with [32P]orthophosphate showed that the new isoform is radiolabeled, predominantly on a serine residue, and hence is called pADF. pADF can be converted into a form which comigrates with ADF on 1-D and 2-D gels by treatment with alkaline phosphatase. pADF has been quantified in a number of cells and tissues where it is present from approximately 18% to 150% of the amount of unphosphorylated ADF. pADF, unlike ADF, does not bind to G-actin, or affect the rate or extent of actin assembly. Four ubiquitous protein kinases failed to phosphorylate ADF in vitro suggesting that ADF phosphorylation in vivo is catalyzed by a more specific kinase. We conclude that the ability to regulate ADF activity is important to muscle development since myocytes have both pre- and posttranslational mechanisms for regulating ADF activity. The latter mechanism is apparently a general one for cell regulation of ADF activity.
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Affiliation(s)
- T E Morgan
- Department of Biochemistry, Colorado State University, Fort Collins 80523
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