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Lefèvre C, Cook GM, Dinan AM, Torii S, Stewart H, Gibbons G, Nicholson AS, Echavarría-Consuegra L, Meredith LW, Lulla V, McGovern N, Kenyon JC, Goodfellow I, Deane JE, Graham SC, Lakatos A, Lambrechts L, Brierley I, Irigoyen N. Zika viruses encode 5' upstream open reading frames affecting infection of human brain cells. Nat Commun 2024; 15:8822. [PMID: 39394194 PMCID: PMC11470053 DOI: 10.1038/s41467-024-53085-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/30/2024] [Indexed: 10/13/2024] Open
Abstract
Zika virus (ZIKV), an emerging mosquito-borne flavivirus, is associated with congenital neurological complications. Here, we investigate potential pathological correlates of virus gene expression in representative ZIKV strains through RNA sequencing and ribosome profiling. In addition to the single long polyprotein found in all flaviviruses, we identify the translation of unrecognised upstream open reading frames (uORFs) in the genomic 5' region. In Asian/American strains, ribosomes translate uORF1 and uORF2, whereas in African strains, the two uORFs are fused into one (African uORF). We use reverse genetics to examine the impact on ZIKV fitness of different uORFs mutant viruses. We find that expression of the African uORF and the Asian/American uORF1 modulates virus growth and tropism in human cortical neurons and cerebral organoids, suggesting a potential role in neurotropism. Although the uORFs are expressed in mosquito cells, we do not see a measurable effect on transmission by the mosquito vector in vivo. The discovery of ZIKV uORFs sheds new light on the infection of the human brain cells by this virus and raises the question of their existence in other neurotropic flaviviruses.
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Affiliation(s)
- Charlotte Lefèvre
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Georgia M Cook
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Adam M Dinan
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
- Department of Medicine, MRC Laboratory of Molecular Biology, University of Cambridge, Cambridge, UK
| | - Shiho Torii
- Institut Pasteur, Université Paris Cité, CNRS UMR2000, Insect-Virus Interactions Unit, Paris, France
| | - Hazel Stewart
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - George Gibbons
- John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, UK
| | - Alex S Nicholson
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | | | - Luke W Meredith
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Valeria Lulla
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Naomi McGovern
- Division of Immunology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Julia C Kenyon
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Ian Goodfellow
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Janet E Deane
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Stephen C Graham
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - András Lakatos
- John van Geest Centre for Brain Repair, University of Cambridge, Cambridge, UK
- Cambridge Stem Cell Institute, Cambridge, UK
| | - Louis Lambrechts
- Institut Pasteur, Université Paris Cité, CNRS UMR2000, Insect-Virus Interactions Unit, Paris, France
| | - Ian Brierley
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Nerea Irigoyen
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK.
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Mónico A, Duarte S, Pajares MA, Pérez-Sala D. Vimentin disruption by lipoxidation and electrophiles: Role of the cysteine residue and filament dynamics. Redox Biol 2019; 23:101098. [PMID: 30658903 PMCID: PMC6859561 DOI: 10.1016/j.redox.2019.101098] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 12/28/2018] [Accepted: 01/05/2019] [Indexed: 12/17/2022] Open
Abstract
The intermediate filament protein vimentin constitutes a critical sensor for electrophilic and oxidative stress, which induce extensive reorganization of the vimentin cytoskeletal network. Here, we have investigated the mechanisms underlying these effects. In vitro, electrophilic lipids, including 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and 4-hydroxynonenal (HNE), directly bind to vimentin, whereas the oxidant diamide induces disulfide bond formation. Mutation of the single vimentin cysteine residue (Cys328) blunts disulfide formation and reduces lipoxidation by 15d-PGJ2, but not HNE. Preincubation with these agents differentially hinders NaCl-induced filament formation by wild-type vimentin, with effects ranging from delayed elongation and increased filament diameter to severe impairment of assembly or aggregation. Conversely, the morphology of vimentin Cys328Ser filaments is mildly or not affected. Interestingly, preformed vimentin filaments are more resistant to electrophile-induced disruption, although chemical modification is not diminished, showing that vimentin (lip)oxidation prior to assembly is more deleterious. In cells, electrophiles, particularly diamide, induce a fast and drastic disruption of existing filaments, which requires the presence of Cys328. As the cellular vimentin network is under continuous remodeling, we hypothesized that vimentin exchange on filaments would be necessary for diamide-induced disruption. We confirmed that strategies reducing vimentin dynamics, as monitored by FRAP, including cysteine crosslinking and ATP synthesis inhibition, prevent diamide effect. In turn, phosphorylation may promote vimentin disassembly. Indeed, treatment with the phosphatase inhibitor calyculin A to prevent dephosphorylation intensifies electrophile-induced wild-type vimentin filament disruption. However, whereas a phosphorylation-deficient vimentin mutant is only partially protected from disorganization, Cys328Ser vimentin is virtually resistant, even in the presence of calyculin A. Together, these results indicate that modification of Cys328 and vimentin exchange are critical for electrophile-induced network disruption.
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Affiliation(s)
- Andreia Mónico
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Sofia Duarte
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - María A Pajares
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain; Molecular Hepatology Group, Instituto de Investigación Sanitaria del Hospital Universitario La Paz (IdiPAZ), Paseo de la Castellana 261, 28046 Madrid, Spain
| | - Dolores Pérez-Sala
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain.
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Mitutsova V, Yeo WWY, Davaze R, Franckhauser C, Hani EH, Abdullah S, Mollard P, Schaeffer M, Fernandez A, Lamb NJC. Adult muscle-derived stem cells engraft and differentiate into insulin-expressing cells in pancreatic islets of diabetic mice. Stem Cell Res Ther 2017; 8:86. [PMID: 28420418 PMCID: PMC5395782 DOI: 10.1186/s13287-017-0539-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 03/16/2017] [Indexed: 12/12/2022] Open
Abstract
Background Pancreatic beta cells are unique effectors in the control of glucose homeostasis and their deficiency results in impaired insulin production leading to severe diabetic diseases. Here, we investigated the potential of a population of nonadherent muscle-derived stem cells (MDSC) from adult mouse muscle to differentiate in vitro into beta cells when transplanted as undifferentiated stem cells in vivo to compensate for beta-cell deficiency. Results In vitro, cultured MDSC spontaneously differentiated into insulin-expressing islet-like cell clusters as revealed using MDSC from transgenic mice expressing GFP or mCherry under the control of an insulin promoter. Differentiated clusters of beta-like cells co-expressed insulin with the transcription factors Pdx1, Nkx2.2, Nkx6.1, and MafA, and secreted significant levels of insulin in response to glucose challenges. In vivo, undifferentiated MDSC injected into streptozotocin (STZ)-treated mice engrafted within 48 h specifically to damaged pancreatic islets and were shown to differentiate and express insulin 10–12 days after injection. In addition, injection of MDSC into hyperglycemic diabetic mice reduced their blood glucose levels for 2–4 weeks. Conclusion These data show that MDSC are capable of differentiating into mature pancreatic beta islet-like cells, not only upon culture in vitro, but also in vivo after systemic injection in STZ-induced diabetic mouse models. Being nonteratogenic, MDSC can be used directly by systemic injection, and this potential reveals a promising alternative avenue in stem cell-based treatment of beta-cell deficiencies. Electronic supplementary material The online version of this article (doi:10.1186/s13287-017-0539-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Violeta Mitutsova
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France
| | - Wendy Wai Yeng Yeo
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France.,Genetics & Regenerative Medicine Research Centre, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
| | - Romain Davaze
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France
| | - Celine Franckhauser
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France
| | - El-Habib Hani
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France
| | - Syahril Abdullah
- Genetics & Regenerative Medicine Research Centre, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
| | - Patrice Mollard
- Networks and Rhythms in Endocrine Glands, IGF, CNRS UMR-5203, Montpellier, France
| | - Marie Schaeffer
- Networks and Rhythms in Endocrine Glands, IGF, CNRS UMR-5203, Montpellier, France
| | - Anne Fernandez
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France.
| | - Ned J C Lamb
- Mammalian Cell Biology group, IGH CNRS, UM, UMR 9002, 141 rue de la Cardonille, 34396, Montpellier cedex 05, France.
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Flynn MP, Fiedler SE, Karlsson AB, Carr DW, Maizels ET, Hunzicker-Dunn M. Dephosphorylation of MAP2D enhances its binding to vimentin in preovulatory ovarian granulosa cells. J Cell Sci 2016; 129:2983-96. [PMID: 27335427 DOI: 10.1242/jcs.190397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/10/2016] [Indexed: 12/28/2022] Open
Abstract
Preovulatory granulosa cells express the low-molecular-mass MAP2D variant of microtubule-associated protein 2 (MAP2). Activation of the luteinizing hormone choriogonadotropin receptor by human choriogonadotropin (hCG) promotes dephosphorylation of MAP2D on Thr256 and Thr259. We sought to evaluate the association of MAP2D with the cytoskeleton, and the effect of hCG on this association. MAP2D partially colocalized, as assessed by confocal immunofluorescence microscopy, with the vimentin intermediate filament and microtubule cytoskeletons in naive cells. In vitro binding studies showed that MAP2D bound directly to vimentin and β-tubulin. Phosphorylation of recombinant MAP2D on Thr256 and Thr259, which mimics the phosphorylation status of MAP2D in naive cells, reduces binding of MAP2D to vimentin and tubulin by two- and three-fold, respectively. PKA-dependent phosphorylation of vimentin (Ser32 and Ser38) promoted binding of vimentin to MAP2D and increased contraction of granulosa cells with reorganization of vimentin filaments and MAP2D from the periphery into a thickened layer surrounding the nucleus and into prominent cellular extensions. Chemical disruption of vimentin filament organization increased progesterone production. Taken together, these results suggest that hCG-stimulated dephosphorylation of MAP2D at Thr256 and Thr259, phosphorylation of vimentin at Ser38 and Ser72, and the resulting enhanced binding of MAP2D to vimentin might contribute to the progesterone synthetic response required for ovulation.
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Affiliation(s)
- Maxfield P Flynn
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Sarah E Fiedler
- Department of Medicine, Oregon Health and Sciences University and VA Portland Health Care System, Portland, OR 97239, USA
| | - Amelia B Karlsson
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Daniel W Carr
- Department of Medicine, Oregon Health and Sciences University and VA Portland Health Care System, Portland, OR 97239, USA
| | - Evelyn T Maizels
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Mary Hunzicker-Dunn
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
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Lowery J, Jain N, Kuczmarski ER, Mahammad S, Goldman A, Gelfand VI, Opal P, Goldman RD. Abnormal intermediate filament organization alters mitochondrial motility in giant axonal neuropathy fibroblasts. Mol Biol Cell 2015; 27:608-16. [PMID: 26700320 PMCID: PMC4750921 DOI: 10.1091/mbc.e15-09-0627] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 12/18/2015] [Indexed: 11/17/2022] Open
Abstract
GAN patient cells have abnormal aggregates of vimentin intermediate filaments, to which mitochondria appear to be tethered. Motility of mitochondria, but not lysosomes, is inhibited in these cells. Transfection with wild-type gigaxonin (the protein mutated in this disease) disperses these aggregates and bundles, and mitochondrial motility returns to normal. Giant axonal neuropathy (GAN) is a rare disease caused by mutations in the GAN gene, which encodes gigaxonin, an E3 ligase adapter that targets intermediate filament (IF) proteins for degradation in numerous cell types, including neurons and fibroblasts. The cellular hallmark of GAN pathology is the formation of large aggregates and bundles of IFs. In this study, we show that both the distribution and motility of mitochondria are altered in GAN fibroblasts and this is attributable to their association with vimentin IF aggregates and bundles. Transient expression of wild-type gigaxonin in GAN fibroblasts reduces the number of IF aggregates and bundles, restoring mitochondrial motility. Conversely, silencing the expression of gigaxonin in control fibroblasts leads to changes in IF organization similar to that of GAN patient fibroblasts and a coincident loss of mitochondrial motility. The inhibition of mitochondrial motility in GAN fibroblasts is not due to a global inhibition of organelle translocation, as lysosome motility is normal. Our findings demonstrate that it is the pathological changes in IF organization that cause the loss of mitochondrial motility.
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Affiliation(s)
- Jason Lowery
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611
| | - Nikhil Jain
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611 Laboratory of Applied Mechanobiology, Department of Health Sciences and Technology, ETH Zurich, Zurich 8093, Switzerland
| | - Edward R Kuczmarski
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611
| | - Saleemulla Mahammad
- Stem Cell and Cancer Research Institute, Michael DeGroote Centre for Learning and Discovery, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Anne Goldman
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611
| | - Puneet Opal
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Robert D Goldman
- Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611
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Zhang X, Liu W, Yang H, Tan L, Ao L, Liu J, Cao J, Cui Z. Inhibition of PPARα attenuates vimentin phosphorylation on Ser-83 and collapse of vimentin filaments during exposure of rat Sertoli cells in vitro to DBP. Reprod Toxicol 2014; 50:11-8. [PMID: 25291543 DOI: 10.1016/j.reprotox.2014.09.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 09/24/2014] [Accepted: 09/25/2014] [Indexed: 12/18/2022]
Abstract
Dibutyl phthalate (DBP) is a peroxisome proliferator which can lead to germ cell loss from Sertoli cells. Collapse of vimentin filaments occurs in Sertoli cells after DBP exposure. Peroxisome proliferator activated receptor α (PPARα) is a key receptor which could be activated by DBP. The role of PPARα in this process was investigated. Results showed that, PPARα was activated in DBP-exposed Sertoli cells, GW6471 inhibited the activity of PPARα, phosphorylation level of vimentin and concentration of soluble vimentin was higher in DBP-treated Sertoli cells than GW6471+DBP-treated cells. These results suggest that PPARα directly or indirectly mediated phosphorylation of vimentin on Ser 83, and PPARα may play an important role in regulating the reorganization of vimentin filaments during exposure of Sertoli cells to DBP.
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Affiliation(s)
- Xi Zhang
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Wenbin Liu
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Huan Yang
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Lu Tan
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Lin Ao
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Jinyi Liu
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Jia Cao
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
| | - Zhihong Cui
- Toxicology Institute, College of Preventive Medicine, Third Military Medical University, No. 30, Gaotanyan Road, Shapingba District, Chongqing 400038, China.
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Johnson-Kerner BL, Roth L, Greene JP, Wichterle H, Sproule DM. Giant axonal neuropathy: An updated perspective on its pathology and pathogenesis. Muscle Nerve 2014; 50:467-76. [DOI: 10.1002/mus.24321] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/16/2014] [Indexed: 12/15/2022]
Affiliation(s)
- Bethany L. Johnson-Kerner
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research; Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia University College of Physicians and Surgeons; New York New York USA
| | - Lisa Roth
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research; Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia University College of Physicians and Surgeons; New York New York USA
| | - J. Palmer Greene
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research; Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia University College of Physicians and Surgeons; New York New York USA
| | - Hynek Wichterle
- Project A.L.S./Jenifer Estess Laboratory for Stem Cell Research; Center for Motor Neuron Biology and Disease, Columbia Stem Cell Initiative, Columbia University College of Physicians and Surgeons; New York New York USA
| | - Douglas M. Sproule
- Division of Pediatric Neurosciences, Department of Neurology; SMA Clinical Research Center, Columbia University Medical Center; Harkness Pavilion, HP-519, 180 Fort Washington Avenue New York New York 10032-3791 USA
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Oncogenes induce a vimentin filament collapse mediated by HDAC6 that is linked to cell stiffness. Proc Natl Acad Sci U S A 2014; 111:1515-20. [PMID: 24474778 DOI: 10.1073/pnas.1300238111] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oncogenes deregulate fundamental cellular functions, which can lead to development of tumors, tumor-cell invasion, and metastasis. As the mechanical properties of cells govern cell motility, we hypothesized that oncogenes promote cell invasion by inducing cytoskeletal changes that increase cellular stiffness. We show that the oncogenes simian virus 40 large T antigen, c-Myc, and cyclin E induce spatial reorganization of the vimentin intermediate filament network in cells. At the cellular level, this reorganization manifests as increased width of vimentin fibers and the collapse of the vimentin network. At nanoscale resolution, the organization of vimentin fibers in these oncogene-expressing cells was more entangled, with increased width of the fibers compared with control cells. Expression of these oncogenes also resulted in up-regulation of the tubulin deacetylase histone deacetylase 6 (HDAC6) and altered spatial distribution of acetylated microtubules. This oncogene expression also induced increases in cellular stiffness and promoted the invasive capacity of the cells. Importantly, HDAC6 was required and sufficient for the structural collapse of the vimentin filament network, and was required for increased cellular stiffness of the oncogene-expressing cells. Taken together, these data are consistent with the possibility that oncogenes can induce cellular stiffness via an HDAC6-induced reorganization of the vimentin intermediate filament network.
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Mussche S, De Paepe B, Smet J, Devreese K, Lissens W, Rasic VM, Murnane M, Devreese B, Van Coster R. Proteomic analysis in giant axonal neuropathy: new insights into disease mechanisms. Muscle Nerve 2012; 46:246-56. [PMID: 22806374 DOI: 10.1002/mus.23306] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
INTRODUCTION Giant axonal neuropathy (GAN) is a progressive hereditary disease that affects the peripheral and central nervous systems. It is characterized morphologically by aggregates of intermediate filaments in different tissues. Mutations have been reported in the gene that codes for gigaxonin. Nevertheless, the underlying molecular mechanism remains obscure. METHODS Cell lines from 4 GAN patients and 4 controls were analyzed by iTRAQ. RESULTS Among the dysregulated proteins were ribosomal protein L29, ribosomal protein L37, galectin-1, glia-derived nexin, and aminopeptidase N. Also, nuclear proteins linked to formin-binding proteins were found to be dysregulated. Although the major role of gigaxonin is reported to be degradation of cytoskeleton-associated proteins, the amount of 76 structural cytoskeletal proteins was unaltered. CONCLUSIONS Several of the dysregulated proteins play a role in cytoskeletal reorganization. Based on these findings, we speculate that disturbed cytoskeletal regulation is responsible for formation of aggregates of intermediate filaments.
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Affiliation(s)
- Silke Mussche
- Department of Pediatrics, Division of Pediatric Neurology and Metabolism, Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium
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Grin B, Mahammad S, Wedig T, Cleland MM, Tsai L, Herrmann H, Goldman RD. Withaferin a alters intermediate filament organization, cell shape and behavior. PLoS One 2012; 7:e39065. [PMID: 22720028 PMCID: PMC3376126 DOI: 10.1371/journal.pone.0039065] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/18/2012] [Indexed: 01/09/2023] Open
Abstract
Withaferin A (WFA) is a steroidal lactone present in Withania somnifera which has been shown in vitro to bind to the intermediate filament protein, vimentin. Based upon its affinity for vimentin, it has been proposed that WFA can be used as an anti-tumor agent to target metastatic cells which up-regulate vimentin expression. We show that WFA treatment of human fibroblasts rapidly reorganizes vimentin intermediate filaments (VIF) into a perinuclear aggregate. This reorganization is dose dependent and is accompanied by a change in cell shape, decreased motility and an increase in vimentin phosphorylation at serine-38. Furthermore, vimentin lacking cysteine-328, the proposed WFA binding site, remains sensitive to WFA demonstrating that this site is not required for its cellular effects. Using analytical ultracentrifugation, viscometry, electron microscopy and sedimentation assays we show that WFA has no effect on VIF assembly in vitro. Furthermore, WFA is not specific for vimentin as it disrupts the cellular organization and induces perinuclear aggregates of several other IF networks comprised of peripherin, neurofilament-triplet protein, and keratin. In cells co-expressing keratin IF and VIF, the former are significantly less sensitive to WFA with respect to inducing perinuclear aggregates. The organization of microtubules and actin/microfilaments is also affected by WFA. Microtubules become wavier and sparser and the number of stress fibers appears to increase. Following 24 hrs of exposure to doses of WFA that alter VIF organization and motility, cells undergo apoptosis. Lower doses of the drug do not kill cells but cause them to senesce. In light of our findings that WFA affects multiple IF systems, which are expressed in many tissues of the body, caution is warranted in its use as an anti-cancer agent, since it may have debilitating organism-wide effects.
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Affiliation(s)
- Boris Grin
- Department of Cell and Molecular Biology, Feinberg School of Medicine at Northwestern University, Chicago, Illinois, United States of America.
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Helfand BT, Mendez MG, Murthy SNP, Shumaker DK, Grin B, Mahammad S, Aebi U, Wedig T, Wu YI, Hahn KM, Inagaki M, Herrmann H, Goldman RD. Vimentin organization modulates the formation of lamellipodia. Mol Biol Cell 2011; 22:1274-89. [PMID: 21346197 PMCID: PMC3078081 DOI: 10.1091/mbc.e10-08-0699] [Citation(s) in RCA: 214] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The disassembly and withdrawal of vimentin intermediate filaments (VIF) from the plasma membrane induces membrane ruffling and the formation of a lamellipodium. Conversely, lamellipodium formation is inhibited when VIF are present. Vimentin intermediate filaments (VIF) extend throughout the rear and perinuclear regions of migrating fibroblasts, but only nonfilamentous vimentin particles are present in lamellipodial regions. In contrast, VIF networks extend to the entire cell periphery in serum-starved or nonmotile fibroblasts. Upon serum addition or activation of Rac1, VIF are rapidly phosphorylated at Ser-38, a p21-activated kinase phosphorylation site. This phosphorylation of vimentin is coincident with VIF disassembly at and retraction from the cell surface where lamellipodia form. Furthermore, local induction of photoactivatable Rac1 or the microinjection of a vimentin mimetic peptide (2B2) disassemble VIF at sites where lamellipodia subsequently form. When vimentin organization is disrupted by a dominant-negative mutant or by silencing, there is a loss of polarity, as evidenced by the formation of lamellipodia encircling the entire cell, as well as reduced cell motility. These findings demonstrate an antagonistic relationship between VIF and the formation of lamellipodia.
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Affiliation(s)
- Brian T Helfand
- Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Kostenko S, Moens U. Heat shock protein 27 phosphorylation: kinases, phosphatases, functions and pathology. Cell Mol Life Sci 2009; 66:3289-307. [PMID: 19593530 PMCID: PMC11115724 DOI: 10.1007/s00018-009-0086-3] [Citation(s) in RCA: 278] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/22/2009] [Accepted: 06/23/2009] [Indexed: 10/20/2022]
Abstract
The small heat shock protein Hsp27 or its murine homologue Hsp25 acts as an ATP-independent chaperone in protein folding, but is also implicated in architecture of the cytoskeleton, cell migration, metabolism, cell survival, growth/differentiation, mRNA stabilization, and tumor progression. A variety of stimuli induce phosphorylation of serine residues 15, 78, and 82 in Hsp27 and serines 15 and 86 in Hsp25. This post-translational modification affects some of the cellular functions of Hsp25/27. As a consequence of the functional importance of Hsp25/27 phosphorylation, aberrant Hsp27 phosphorylation has been linked to several clinical conditions. This review focuses on the different Hsp25/27 kinases and phosphatases that regulate the phosphorylation pattern of Hsp25/27, and discusses the recent findings of the biological implications of these phosphorylation events in physiological and pathological processes. Novel therapeutic strategies aimed at restoring anomalous Hsp27 phosphorylation in human diseases will be presented.
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Affiliation(s)
- Sergiy Kostenko
- Department of Microbiology and Virology, Faculty of Medicine, University of Tromsø, 9037 Tromsø, Norway
| | - Ugo Moens
- Department of Microbiology and Virology, Faculty of Medicine, University of Tromsø, 9037 Tromsø, Norway
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13
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Chang L, Barlan K, Chou YH, Grin B, Lakonishok M, Serpinskaya AS, Shumaker DK, Herrmann H, Gelfand VI, Goldman RD. The dynamic properties of intermediate filaments during organelle transport. J Cell Sci 2009; 122:2914-23. [PMID: 19638410 DOI: 10.1242/jcs.046789] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Intermediate filament (IF) dynamics during organelle transport and their role in organelle movement were studied using Xenopus laevis melanophores. In these cells, pigment granules (melanosomes) move along microtubules and microfilaments, toward and away from the cell periphery in response to alpha-melanocyte stimulating hormone (alpha-MSH) and melatonin, respectively. In this study we show that melanophores possess a complex network of vimentin IFs which interact with melanosomes. IFs form an intricate, honeycomb-like network that form cages surrounding individual and small clusters of melanosomes, both when they are aggregated and dispersed. Purified melanosome preparations contain a substantial amount of vimentin, suggesting that melanosomes bind to IFs. Analyses of individual melanosome movements in cells with disrupted IF networks show increased movement of granules in both anterograde and retrograde directions, further supporting the notion of a melanosome-IF interaction. Live imaging reveals that IFs, in turn, become highly flexible as melanosomes disperse in response to alpha-MSH. During the height of dispersion there is a marked increase in the rate of fluorescence recovery after photobleaching of GFP-vimentin IFs and an increase in vimentin solubility. These results reveal a dynamic interaction between membrane bound pigment granules and IFs and suggest a role for IFs as modulators of granule movement.
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Affiliation(s)
- Lynne Chang
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Harvard University, Boston, MA, USA
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14
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Minin AA, Moldaver MV. Intermediate vimentin filaments and their role in intracellular organelle distribution. BIOCHEMISTRY (MOSCOW) 2009; 73:1453-66. [PMID: 19216711 DOI: 10.1134/s0006297908130063] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Intermediate filaments (IF) represent one of three main cytoskeletal structures in most animal cells. The human IF protein family includes about 70 members divided into five main groups. The characteristic feature of IF is that in various cells and tissues they are formed by proteins of different groups. Structures of all IF proteins follow a unique scheme: a central alpha-helical part is flanked at the N and C ends by positively charged polypeptide chains devoid of a clear secondary structure. The central part is highly conserved for all proteins in all animals, whereas the N and C termini strongly differ both in size and amino acid composition. This review covers the broad spectrum of recent investigations of IF structure and diverse functions. Special attention is paid to the regulatory mechanisms of IF functions, mainly to phosphorylation by different protein kinases whose role is well studied. The review gives examples of hereditary diseases associated with mutations of some IF proteins, which point to an important physiological role of these cytoskeletal structures.
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Affiliation(s)
- A A Minin
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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15
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Flitney EW, Kuczmarski ER, Adam SA, Goldman RD. Insights into the mechanical properties of epithelial cells: the effects of shear stress on the assembly and remodeling of keratin intermediate filaments. FASEB J 2009; 23:2110-9. [PMID: 19246484 DOI: 10.1096/fj.08-124453] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The effects of shear stress on the keratin intermediate filament (KIF) cytoskeleton of cultured human alveolar epithelial (A549) cells have been investigated. Under normal culture conditions, immunofluorescence revealed a delicate network of fine tonofibrils containing KIFs, together with many nonfilamentous, keratin-containing "particles," mostly containing either keratin 8 (K8) or 18 (K18), but not both. Triton X-100 extracted approximately 10% of the cellular keratin, and this was accompanied by a loss of the particles but not the KIFs. Shear stress dramatically reduced the soluble keratin component and transformed the fine bundles of KIFs into thicker, "wavy" tonofibrils. Both effects were accompanied by the disappearance of most keratin particles and by increased phosphorylation of K8 and K18 on serine residues 73 and 33, respectively. The particles that remained after shearing were phosphorylated and were closely associated with KIFs. We suggest that keratin particles constitute a reservoir of protein that can be recruited into KIFs under flow, creating a more robust cytoskeleton able to withstand shear forces more effectively.
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Affiliation(s)
- Eric W Flitney
- Department of Cell and Molecular Biology, Feinberg School of Medicine of Northwestern University, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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16
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Liu YR, Ye WL, Zeng XM, Ren WH, Zhang YQ, Mei YA. K+ channels and the cAMP-PKA pathway modulate TGF-beta1-induced migration of rat vascular myofibroblasts. J Cell Physiol 2008; 216:835-43. [PMID: 18551429 DOI: 10.1002/jcp.21464] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Our previous studies have indicated that TGF-beta1 exerts its effect on the expression of A-type potassium channels (I(A)) in rat vascular myofibroblasts by activation of protein kinase C during the phenotypic transformation of vascular fibroblasts to myofibroblasts. In the present study, patch-clamp whole-cell recording and transwell-migration assays were used to examine the effects of TGF-beta1- and phorbol 12-myristate 13-acetate (PMA)-induced expression of I(A) channels on myofibroblast migration and its modulation by the protein kinase A (PKA) pathway. Our results reveal that incubation of fibroblasts with TGF-beta1 or PMA up-regulates the expression of I(A) channels and increases myofibroblast migration. Blocking I(A) channel expression by 4-aminopyridine (4-AP) significantly inhibits TGF-beta1- and PMA-induced myofibroblast migration. Incubation of fibroblasts with forskolin does not result in increased expression of I(A) channels but does cause a slight increase in fibroblast migration at higher concentrations. In addition, forskolin increases the TGF-beta1- and PMA-induced myofibroblast migration but inhibits TGF-beta1- and PMA-induced the expression of I(A) channels. Whole-cell current recordings showed that forskolin augments the delayed rectifier outward K(+) (I(K)) current amplitude of fibroblasts, but not the I(A) of myofibroblasts. Our results also indicate that TGF-beta1- and PMA-induced expression of I(A) channels might be related to increase TGF-beta1- or PMA-induced myofibroblast migration. Promoting fibroblast and myofibroblast migration via the PKA pathway does not seem to involve the expression of I(A) channels, but the modulation of I(K) and I(A) channels might be implicated.
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Affiliation(s)
- Ya-Rong Liu
- Institute of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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17
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Nadella KS, Jones GN, Trimboli A, Stratakis CA, Leone G, Kirschner LS. Targeted deletion of Prkar1a reveals a role for protein kinase A in mesenchymal-to-epithelial transition. Cancer Res 2008; 68:2671-7. [PMID: 18413734 DOI: 10.1158/0008-5472.can-07-6002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Dysregulation of protein kinase A (PKA) activity, caused by loss of function mutations in PRKAR1A, is known to induce tumor formation in the inherited tumor syndrome Carney complex (CNC) and is also associated with sporadic tumors of the thyroid and adrenal. We have previously shown that Prkar1a(+/-) mice develop schwannomas reminiscent of those seen in CNC and that similar tumors are observed in tissue-specific knockouts (KO) of Prkar1a targeted to the neural crest. Within these tumors, we have previously described the presence of epithelial islands, although the nature of these structures was unclear. In this article, we report that these epithelial structures are derived from KO cells originating in the neural crest. Analysis of the mesenchymal marker vimentin revealed that this protein was markedly down-regulated not only from the epithelial islands, but also from the tumor as a whole, consistent with mesenchymal-to-epithelial transition (MET). In vitro, Prkar1a null primary mouse embryonic fibroblasts, which display constitutive PKA signaling, also showed evidence for MET, with a loss of vimentin and up-regulation of the epithelial marker E-cadherin. Reduction of vimentin protein occurred at the posttranslational level and was rescued by proteasomal inhibition. Finally, this down-regulation of vimentin was recapitulated in the adrenal nodules of CNC patients, confirming an unexpected and previously unrecognized role for PKA in MET.
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Affiliation(s)
- Kiran S Nadella
- Human Cancer Genetics Program, Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, Ohio, USA
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18
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Zamoner A, Barreto KP, Filho DW, Sell F, Woehl VM, Guma FCR, Silva FRMB, Pessoa-Pureur R. Hyperthyroidism in the developing rat testis is associated with oxidative stress and hyperphosphorylated vimentin accumulation. Mol Cell Endocrinol 2007; 267:116-26. [PMID: 17306450 DOI: 10.1016/j.mce.2007.01.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Revised: 01/06/2007] [Accepted: 01/09/2007] [Indexed: 12/20/2022]
Abstract
Hyperthyroidism was induced in rats and somatic indices and metabolic parameters were analyzed in testis. In addition, the morphological analysis evidenced testes maturation and intense protein synthesis and processing, supporting the enhancement in vimentin synthesis in hyperthyroid testis. Furthermore, vimentin phosphorylation was increased, indicating an accumulation of phosphorylated vimentin associated to the cytoskeleton, which could be a consequence of the extracellular-regulated kinase (ERK) activation regulating the cytoskeleton. Biomarkers of oxidative stress demonstrated an increased basal metabolic rate measured by tissue oxygen consumption, as well as, increased TBARS levels. In addition, the enzymatic and non-enzymatic antioxidant defences appeared to respond according to the augmented oxygen consumption. We observed decreased total glutathione levels, with enhancement of reduced glutathione, whereas most of the antioxidant enzyme activities were induced. Otherwise, superoxide dismutase activity was inhibited. These results support the idea that an increase in mitochondrial ROS generation, underlying cellular oxidative damage, is a side effect of hyperthyroid-induced biochemical changes by which rat testis increase their metabolic capacity.
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Affiliation(s)
- Ariane Zamoner
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, UFRGS, Porto Alegre, RS, Brazil
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19
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Russell MA, Lund LM, Haber R, McKeegan K, Cianciola N, Bond M. The intermediate filament protein, synemin, is an AKAP in the heart. Arch Biochem Biophys 2006; 456:204-15. [PMID: 16934740 DOI: 10.1016/j.abb.2006.06.010] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Revised: 06/01/2006] [Accepted: 06/06/2006] [Indexed: 11/28/2022]
Abstract
Targeting of protein kinase A (PKA) by A-kinase anchoring proteins (AKAPs) contributes to high specificity of PKA signaling pathways. PKA phosphorylation of myofilament and cytoskeletal proteins may regulate myofibrillogenesis and myocyte remodeling during heart disease; however, known cardiac AKAPs do not localize to these regions. To identify novel AKAPs which target PKA to the cytoskeleton or myofilaments, a human heart cDNA library was screened and the intermediate filament (IF) protein, synemin, was identified as a putative RII (PKA regulatory subunit type II) binding protein. A predicted RII binding region was mutated and resulted in loss of RII binding. Furthermore, synemin co-localized with RII in SW13/cl.1-vim+ cells and co-immunoprecipitated with RII from adult rat cardiomyocytes. Synemin was localized at the level of Z-lines with RII and desmin in adult hearts, however, neonatal cardiomyocytes showed differential synemin and desmin localization. Quantitative Western blots also showed significantly more synemin was present in failing human hearts. We propose that synemin provides temporal and spatial targeting of PKA in adult and neonatal cardiac myocytes.
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Affiliation(s)
- Mary A Russell
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
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20
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Funchal C, Dos Santos AQ, Jacques-Silva MC, Zamoner A, Gottfried C, Wajner M, Pessoa-Pureur R. Branched-chain alpha-keto acids accumulating in maple syrup urine disease induce reorganization of phosphorylated GFAP in C6-glioma cells. Metab Brain Dis 2005; 20:205-17. [PMID: 16167198 DOI: 10.1007/s11011-005-7208-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Accepted: 06/07/2005] [Indexed: 11/30/2022]
Abstract
In this study we investigate the effects of the branched-chain keto acids (BCKA) alpha-ketoisocaproic (KIC), alpha-ketoisovaleric (KIV), and alpha-keto-beta-methylvaleric (KMV) acids, metabolites accumulating in maple syrup urine disease (MSUD), on the in vitro phosphorylation of glial fibrillary acidic protein (GFAP) and cytoskeletal reorganization in C6-glioma cells. We observed that after 3 h treatment with KIC, KIV, or KMV cells showed retracted cytoplasm with bipolar processes containing packed GFAP filaments as revealed by immunocytochemistry. Western Blot analysis by anti-GFAP monoclonal antibody demonstrated that BCKA were not able to alter GFAP immunocontent in total cell homogenate, but the immunocontent as well as the in vitro (32)P incorporation into GFAP recovered into the high salt Triton-insoluble cytoskeletal fraction were significantly increased. Western Blot using monoclonal antiphosphoserine antibody showed that BCKA induced increased immunocontent of phosphoserine-containing amino acids in several proteins in total cell homogenate. In addition, the immunocontent of phosphoserine-containing amino acids was also greatly increased in GFAP recovered in the high-salt Triton insoluble cytoskeletal fraction, corresponding to the polymerized intermedite filament (IF) proteins present in the cell. In conclusion, our results indicate that KIC, KIV, or KMV increased the serine/threonine in vitro phosphorylation of GFAP leading to increased Triton-insoluble GFAP immunocontent and cytoskeletal reorganization. Considering IF networks can be regulated by phosphorylation of polypeptide subunits leading to reorganization of the IF filamentous structure, we could suppose that GFAP hyperphosphorylation and disorganization of cellular structure could be involved in the brain damage characteristic of MSUD patients.
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Affiliation(s)
- Cláudia Funchal
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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21
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Moretto MB, Funchal C, Zeni G, Rocha JBT, Pessoa-Pureur R. Organoselenium compounds prevent hyperphosphorylation of cytoskeletal proteins induced by the neurotoxic agent diphenyl ditelluride in cerebral cortex of young rats. Toxicology 2005; 210:213-22. [PMID: 15840435 DOI: 10.1016/j.tox.2005.02.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2004] [Revised: 01/24/2005] [Accepted: 02/08/2005] [Indexed: 10/25/2022]
Abstract
In this work we investigated the protective ability of the selenium compounds ebselen and diphenyl diselenide against the effect of diphenyl ditelluride on the in vitro incorporation of 32P into intermediate filament (IF) proteins from slices of cerebral cortex of 17-day-old rats. We observed that ditelluride in the concentrations of 1, 15 and 50 microM induced hyperphosphorylation of the high-salt Triton insoluble neurofilament subunits (NF-M and NF-L), glial fibrillary acidic protein (GFAP) and vimentin, without altering the immunocontent of these proteins. Concerning the selenium compounds, diselenide (1,15 and 50 microM) did not induce alteration of the in vitro phosphorylation of the IF proteins. Otherwise, ebselen induced an altered in vitro phosphorylation of the cytoskeletal proteins in a dose-dependent manner. At intermediate concentrations (15 and 30 microM) it increased the in vitro phosphorylation even though, at low (5 microM) or high (50 and 100 microM) concentrations this compound was ineffective in altering the activity of the cytoskeletal-associated phosphorylating system. In addition, 15 microM diselenide and 5 microM ebselen, presented a protective effect against the action of ditelluride, on the phosphorylation of the proteins studied. Considering that hyperphosphorylation of cytoskeletal proteins is associated with neuronal dysfunction and neurodegeneration, it is probable that the effects of ditelluride could be related to the remarkable neurotoxicity of this organic form of tellurium. Furthermore the neuroprotective action of selenium compounds against tellurium effects could be a promising route to be exploited for a possible treatment of organic tellurium poisoning.
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Affiliation(s)
- M B Moretto
- Departamento de Análises Clínicas e Toxicológicas, Centro de Ciências da Saúde, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
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22
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Eriksson JE, He T, Trejo-Skalli AV, Härmälä-Braskén AS, Hellman J, Chou YH, Goldman RD. Specific in vivo phosphorylation sites determine the assembly dynamics of vimentin intermediate filaments. J Cell Sci 2004. [DOI: 10.1242/jcs.00906 jcs.00906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intermediate filaments (IFs) continuously exchange between a small, depolymerized fraction of IF protein and fully polymerized IFs. To elucidate the possible role of phosphorylation in regulating this equilibrium, we disrupted the exchange of phosphate groups by specific inhibition of dephosphorylation and by specific phosphorylation and site-directed mutagenesis of two of the major in vivo phosphorylation sites determined in this study. Inhibition of type-1 (PP1) and type-2A (PP2A) protein phosphatases in BHK-21 fibroblasts with calyculin-A, induced rapid vimentin phosphorylation in concert with disassembly of the IF polymers into soluble tetrameric vimentin oligomers. This oligomeric composition corresponded to the oligopeptides released by cAMP-dependent kinase (PKA) following in vitro phosphorylation. Characterization of the 32P-labeled vimentin phosphopeptides, demonstrated Ser-4, Ser-6, Ser-7, Ser-8, Ser-9, Ser-38, Ser-41, Ser-71, Ser-72, Ser-418, Ser-429, Thr-456, and Ser-457 as significant in vivo phosphorylation sites. A number of the interphase-specific high turnover sites were shown to be in vitro phosphorylation sites for PKA and protein kinase C (PKC). The effect of presence or absence of phosphate groups on individual subunits was followed in vivo by microinjecting PKA-phosphorylated (primarily S38 and S72) and mutant vimentin (S38:A, S72:A), respectively. The PKA-phosphorylated vimentin showed a clearly decelerated filament formation in vivo, whereas obstruction of phosphorylation at these sites by site-directed mutagenesis had no significant effect on the incorporation rates of subunits into assembled polymers. Taken together, our results suggest that elevated phosphorylation regulates IF assembly in vivo by changing the equilibrium constant of subunit exchange towards a higher off-rate.
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Affiliation(s)
- John E. Eriksson
- Department of Biology, Laboratory of Animal Physiology, University of Turku, Science Building 1, FIN-20014 Turku, Finland
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, POB 123, FIN-20521 Turku, Finland
| | - Tao He
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, POB 123, FIN-20521 Turku, Finland
- Department of Biochemistry, Åbo Akademi University, FIN-20521 Turku, Finland
- Turku Graduate School of Biomedical Sciences, Kiinanmyllynkatu 13, FIN-20520, Turku, Finland
| | - Amy V. Trejo-Skalli
- Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, 303 E. Chicago Avenue, Chicago, IL-60611-3008, USA
| | - Ann-Sofi Härmälä-Braskén
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, POB 123, FIN-20521 Turku, Finland
- Department of Biochemistry, Åbo Akademi University, FIN-20521 Turku, Finland
| | - Jukka Hellman
- Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, POB 123, FIN-20521 Turku, Finland
| | - Ying-Hao Chou
- Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, 303 E. Chicago Avenue, Chicago, IL-60611-3008, USA
| | - Robert D. Goldman
- Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, 303 E. Chicago Avenue, Chicago, IL-60611-3008, USA
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23
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Eriksson JE, He T, Trejo-Skalli AV, Härmälä-Braskén AS, Hellman J, Chou YH, Goldman RD. Specific in vivo phosphorylation sites determine the assembly dynamics of vimentin intermediate filaments. J Cell Sci 2004; 117:919-32. [PMID: 14762106 DOI: 10.1242/jcs.00906] [Citation(s) in RCA: 250] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Intermediate filaments (IFs) continuously exchange between a small, depolymerized fraction of IF protein and fully polymerized IFs. To elucidate the possible role of phosphorylation in regulating this equilibrium, we disrupted the exchange of phosphate groups by specific inhibition of dephosphorylation and by specific phosphorylation and site-directed mutagenesis of two of the major in vivo phosphorylation sites determined in this study. Inhibition of type-1 (PP1) and type-2A (PP2A) protein phosphatases in BHK-21 fibroblasts with calyculin-A, induced rapid vimentin phosphorylation in concert with disassembly of the IF polymers into soluble tetrameric vimentin oligomers. This oligomeric composition corresponded to the oligopeptides released by cAMP-dependent kinase (PKA) following in vitro phosphorylation. Characterization of the (32)P-labeled vimentin phosphopeptides, demonstrated Ser-4, Ser-6, Ser-7, Ser-8, Ser-9, Ser-38, Ser-41, Ser-71, Ser-72, Ser-418, Ser-429, Thr-456, and Ser-457 as significant in vivo phosphorylation sites. A number of the interphase-specific high turnover sites were shown to be in vitro phosphorylation sites for PKA and protein kinase C (PKC). The effect of presence or absence of phosphate groups on individual subunits was followed in vivo by microinjecting PKA-phosphorylated (primarily S38 and S72) and mutant vimentin (S38:A, S72:A), respectively. The PKA-phosphorylated vimentin showed a clearly decelerated filament formation in vivo, whereas obstruction of phosphorylation at these sites by site-directed mutagenesis had no significant effect on the incorporation rates of subunits into assembled polymers. Taken together, our results suggest that elevated phosphorylation regulates IF assembly in vivo by changing the equilibrium constant of subunit exchange towards a higher off-rate.
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Affiliation(s)
- John E Eriksson
- Department of Biology, Laboratory of Animal Physiology, University of Turku, Science Building 1, FIN-20014 Turku, Finland.
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24
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Cheng TJ, Tseng YF, Chang WM, Chang MDT, Lai YK. Retaining of the assembly capability of vimentin phosphorylated by mitogen-activated protein kinase-activated protein kinase-2. J Cell Biochem 2003; 89:589-602. [PMID: 12761892 DOI: 10.1002/jcb.10511] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Intermediate filament (IF) networks can be regulated by phosphorylation of unit proteins, such as vimentin, by specific kinases leading to reorganization of the IF filamentous structure. Recently, we identified mitogen-activated protein kinase-activated protein kinase-2 (MAPKAP kinase-2) as a vimentin kinase (Cheng and Lai [1998] J. Cell. Biochem. 71:169-181). Herein we describe the results of further in vitro studies investigating the effects of MAPKAP kinase-2 phosphorylation on vimentin and the effects of the phosphorylation on the filamentous structure. We show that MAPKAP kinase-2 mainly phosphorylates vimentin at Ser-38, Ser-50, Ser-55, and Ser-82, residues all located in the head domain of the protein. Surprisingly, and in stark contrast to phosphorylation by most other kinases, phosphorylation of vimentin by MAPKAP kinase-2 has no discernable effect on its assembly. It suggested that structure disassembly is not the only obligated consequence of phosphorylated vimentin as regulated by other kinases. Finally, a mutational analysis of each of the phosphorylated serine residues in vimentin suggested that no single serine site was primarily responsible for structure maintenance, implying that the retention of filamentous structure may be the result of the coordinated action of several phosphorylated serine sites. This also shed new lights on the functional task(s) of vimentin that is intermediate filament proteins might provide a phosphate reservoir to accommodate the phosphate surge without any structural changes.
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Affiliation(s)
- Ting-Jen Cheng
- Department of Life Science, National Tsing Hua University, Hsinshu, Taiwan 30013, Republic of China
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25
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Helfand BT, Mikami A, Vallee RB, Goldman RD. A requirement for cytoplasmic dynein and dynactin in intermediate filament network assembly and organization. J Cell Biol 2002; 157:795-806. [PMID: 12034772 PMCID: PMC2173407 DOI: 10.1083/jcb.200202027] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2002] [Revised: 04/05/2002] [Accepted: 04/24/2002] [Indexed: 12/15/2022] Open
Abstract
We present evidence that vimentin intermediate filament (IF) motility in vivo is associated with cytoplasmic dynein. Immunofluorescence reveals that subunits of dynein and dynactin are associated with all structural forms of vimentin in baby hamster kidney-21 cells. This relationship is also supported by the presence of numerous components of dynein and dynactin in IF-enriched cytoskeletal preparations. Overexpression of dynamitin biases IF motility toward the cell surface, leading to a perinuclear clearance of IFs and their redistribution to the cell surface. IF-enriched cytoskeletal preparations from dynamitin-overexpressing cells contain decreased amounts of dynein, actin-related protein-1, and p150Glued relative to controls. In contrast, the amount of dynamitin is unaltered in these preparations, indicating that it is involved in linking vimentin cargo to dynactin. The results demonstrate that dynein and dynactin are required for the normal organization of vimentin IF networks in vivo. These results together with those of previous studies also suggest that a balance among the microtubule (MT) minus and plus end-directed motors, cytoplasmic dynein, and kinesin are required for the assembly and maintenance of type III IF networks in interphase cells. Furthermore, these motors are to a large extent responsible for the long recognized relationships between vimentin IFs and MTs.
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Affiliation(s)
- Brian T Helfand
- Northwestern University School of Medicine, Department of Cell and Molecular Biology, Chicago, IL 60611, USA
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26
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Sahlgren CM, Mikhailov A, Hellman J, Chou YH, Lendahl U, Goldman RD, Eriksson JE. Mitotic reorganization of the intermediate filament protein nestin involves phosphorylation by cdc2 kinase. J Biol Chem 2001; 276:16456-63. [PMID: 11278541 DOI: 10.1074/jbc.m009669200] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The intermediate filament protein nestin is expressed during early stages of development in the central nervous system and in muscle tissues. Nestin expression is associated with morphologically dynamic cells, such as dividing and migrating cells. However, little is known about regulation of nestin during these cellular processes. We have characterized the phosphorylation-based regulation of nestin during different stages of the cell cycle in a neuronal progenitor cell line, ST15A. Confocal microscopy of nestin organization and (32)P in vivo labeling studies show that the mitotic reorganization of nestin is accompanied by elevated phosphorylation of nestin. The phosphorylation-induced alterations in nestin organization during mitosis in ST15A cells are associated with partial disassembly of nestin filaments. Comparative in vitro and in vivo phosphorylation studies identified cdc2 as the primary mitotic kinase and Thr(316) as a cdc2-specific phosphorylation site on nestin. We generated a phosphospecific nestin antibody recognizing the phosphorylated form of this site. By using this antibody we observed that nestin shows constitutive phosphorylation at Thr(316), which is increased during mitosis. This study shows that nestin is reorganized during mitosis and that cdc2-mediated phosphorylation is an important regulator of nestin organization and dynamics during mitosis.
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Affiliation(s)
- C M Sahlgren
- Turku Centre for Biotechnology, University of Turku and Abo Akademi University, FIN-20521 Turku, Finland
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27
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Meriane M, Mary S, Comunale F, Vignal E, Fort P, Gauthier-Rouviére C. Cdc42Hs and Rac1 GTPases induce the collapse of the vimentin intermediate filament network. J Biol Chem 2000; 275:33046-52. [PMID: 10900195 DOI: 10.1074/jbc.m001566200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In this study we show that expression of active Cdc42Hs and Rac1 GTPases, two Rho family members, leads to the reorganization of the vimentin intermediate filament (IF) network, showing a perinuclear collapse. Cdc42Hs displays a stronger effect than Rac1 as 90% versus 75% of GTPase-expressing cells show vimentin collapse. Similar vimentin IF modifications were observed when endogenous Cdc42Hs was activated by bradykinin treatment, endogenous Rac1 by platelet-derived growth factor/epidermal growth factor, or both endogenous proteins upon expression of active RhoG. This reorganization of the vimentin IF network is not associated with any significant increase in soluble vimentin. Using effector loop mutants of Cdc42Hs and Rac1, we show that the vimentin collapse is mostly independent of CRIB (Cdc42Hs or Rac-interacting binding)-mediated pathways such as JNK or PAK activation but is associated with actin reorganization. This does not result from F-actin depolymerization, because cytochalasin D treatment or Scar-WA expression have merely no effect on vimentin organization. Finally, we show that genistein treatment of Cdc42 and Rac1-expressing cells strongly reduces vimentin collapse, whereas staurosporin, wortmannin, LY-294002, R(p)-cAMP, or RII, the regulatory subunit of protein kinase A, remain ineffective. Moreover, we detected an increase in cellular tyrosine phosphorylation content after Cdc42Hs and Rac1 expression without modification of the vimentin phosphorylation status. These data indicate that Cdc42Hs and Rac1 GTPases control vimentin IF organization involving tyrosine phosphorylation events.
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Affiliation(s)
- M Meriane
- Centre de Recherche de Biochimie Macromoléculaire, CNRS, UPR 1086, 1919 Route de Mende, Montpellier 34293, Cedex, France
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28
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Janosch P, Kieser A, Eulitz M, Lovric J, Sauer G, Reichert M, Gounari F, Büscher D, Baccarini M, Mischak H, Kolch W. The Raf-1 kinase associates with vimentin kinases and regulates the structure of vimentin filaments. FASEB J 2000; 14:2008-21. [PMID: 11023985 DOI: 10.1096/fj.99-0883com] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Using immobilized GST-Raf-1 as bait, we have isolated the intermediate filament protein vimentin as a Raf-1-associated protein. Vimentin coimmunoprecipitated and colocalized with Raf-1 in fibroblasts. Vimentin was not a Raf-1 substrate, but was phosphorylated by Raf-1-associated vimentin kinases. We provide evidence for at least two Raf-1-associated vimentin kinases and identified one as casein kinase 2. They are regulated by Raf-1, since the activation status of Raf-1 correlated with the phosphorylation of vimentin. Vimentin phosphorylation by Raf-1 preparations interfered with its polymerization in vitro. A subset of tryptic vimentin phosphopeptides induced by Raf-1 in vitro matched the vimentin phosphopeptides isolated from v-raf-transfected cells labeled with orthophosphoric acid, indicating that Raf-1 also induces vimentin phosphorylation in intact cells. In NIH 3T3 fibroblasts, the selective activation of an estrogen-regulated Raf-1 mutant induced a rearrangement and depolymerization of the reticular vimentin scaffold similar to the changes elicited by serum treatment. The rearrangement of the vimentin network occurred independently of the MEK/ERK pathway. These data identify a new branch point in Raf-1 signaling, which links Raf-1 to changes in the cytoskeletal architecture.
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Affiliation(s)
- P Janosch
- The Beatson Institute for Cancer Research, Garscube Estate, Glasgow G61 1BD, U.K.
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Pepperkok R, Hotz-Wagenblatt A, König N, Girod A, Bossemeyer D, Kinzel V. Intracellular distribution of mammalian protein kinase A catalytic subunit altered by conserved Asn2 deamidation. J Cell Biol 2000; 148:715-26. [PMID: 10684253 PMCID: PMC2169370 DOI: 10.1083/jcb.148.4.715] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [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 catalytic (C) subunit of protein kinase A functions both in the cytoplasm and the nucleus. A major charge variant representing about one third of the enzyme in striated muscle results from deamidation in vivo of the Asn2 residue at the conserved NH(2)-terminal sequence myrGly-Asn-Ala (Jedrzejewski, P.T., A. Girod, A. Tholey, N. König, S. Thullner, V. Kinzel, and D. Bossemeyer. 1998. Protein Sci. 7:457-469). Because of the increase of electronegativity by generation of Asp2, it is reminiscent of a myristoyl-electrostatic switch. To compare the intracellular distribution of the enzymes, both forms of porcine or bovine heart enzyme were microinjected into the cytoplasm of mouse NIH 3T3 cells after conjugation with fluorescein, rhodamine, or in unlabeled form. The nuclear/cytoplasmic fluorescence ratio (N/C) was analyzed in the presence of cAMP (in the case of unlabeled enzyme by antibodies). Under all circumstances, the N/C ratio obtained with the encoded Asn2 form was significantly higher than that with the deamidated, Asp2 form; i.e., the Asn2 form reached a larger nuclear concentration than the Asp2 form. Comparable data were obtained with a human cell line. The differential intracellular distribution of both enzyme forms is also reflected by functional data. It correlates with the degree of phosphorylation of the key serine in CREB family transcription factors in the nucleus. Microinjection of myristoylated recombinant bovine Calpha and the Asn2 deletion mutant of it yielded N/C ratios in the same range as encoded native enzymes. Thus, Asn2 seems to serve as a potential site for modulating electronegativity. The data indicate that the NH(2)-terminal domain of the PKA C-subunit contributes to the intracellular distribution of free enzyme, which can be altered by site-specific in vivo deamidation. The model character for other signaling proteins starting with myrGly-Asn is discussed.
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Affiliation(s)
- Rainer Pepperkok
- European Molecular Biology Laboratory, D-69012 Heidelberg, Germany
| | - Agnes Hotz-Wagenblatt
- Department of Pathochemistry, German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Norbert König
- Department of Pathochemistry, German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Andreas Girod
- European Molecular Biology Laboratory, D-69012 Heidelberg, Germany
- Department of Pathochemistry, German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Dirk Bossemeyer
- Department of Pathochemistry, German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Volker Kinzel
- Department of Pathochemistry, German Cancer Research Center, D-69120 Heidelberg, Germany
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30
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Gabel S, Benefield J, Meisinger J, Petruzzelli GJ, Young MR. Protein phosphatases 1 and 2A maintain endothelial cells in a resting state, limiting the motility that is needed for the morphogenic process of angiogenesis. Otolaryngol Head Neck Surg 1999; 121:463-8. [PMID: 10504605 DOI: 10.1016/s0194-5998(99)70238-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Angiogenesis that is induced by cancers, including those of the head and neck, requires endothelial cells to shift from a nonmotile resting state to an increased level of motility. Using a human microvascular endothelial cell line, this study shows the importance of the serine/threonine protein phosphatases 1 (PP1) and 2A (PP2A) in restricting endothelial cell motility. Treatment of endothelial cells with increasing concentrations of the PP1 and PP2A inhibitor okadaic acid resulted in cell rounding and increased motility, which was accompanied by cytoskeletal disorganization involving a loss of filamentous beta-tubulin and F-actin. These effects occurred at okadaic acid levels that selectively inhibit PP2A and became more prominent with higher levels that inhibit both PP2A and PP1. This study shows the importance of PP1 and PP2A in maintaining cytoskeletal organization, thereby limiting endothelial cell motility, and suggests that pharmacologic approaches to enhance PP1 and PP2A activities may be useful in preventing key events of the angiogenic process.
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Affiliation(s)
- S Gabel
- Department of Otolaryngology-Head and Neck Surgery, Loyola University Medical Center, Maywood, USA
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31
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Haier J, Nasralla M, Nicolson GL. Different adhesion properties of highly and poorly metastatic HT-29 colon carcinoma cells with extracellular matrix components: role of integrin expression and cytoskeletal components. Br J Cancer 1999; 80:1867-74. [PMID: 10471033 PMCID: PMC2374274 DOI: 10.1038/sj.bjc.6690614] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Integrin-mediated tumour cell adhesion to extracellular matrix (ECM) components is an important step in the development of metastatic lesions. Thus, integrin expression and integrin-mediated adhesion of colon carcinoma cells to various ECM components was examined. Poorly (HT-29P) and highly (HT-29LMM) liver-metastatic colon carcinoma cells were used to study the rates of adhesion to collagen I (C I), collagen IV (C IV), laminin (LN), fibronectin (FN), or vitronectin (VN) in a static adhesion assay (10-120 min). Cells were untreated or treated with oligopeptides (RGD, GRGDS, YIGSR, RGES), anti-integrin antibodies, or colchicine, nocodazole, cycloheximide, acrylamide or cytochalasin D (to disrupt cytoskeletal structures). Both cell lines expressed similar patterns of integrin expression (alpha2, alpha3, ,alpha6, alphav, beta1, beta4, and beta5) by immunocytochemistry and immunoprecipitation. HT-29LMM cells showed significantly higher rates of adhesion to LN (P < 0.001) and FN (P < 0.001), but significantly poorer rates of adhesion to C I (P < 0.05) and C IV (P < 0.001) than HT-29P cells, respectively, adhesion to VN was insignificant. RGD and GRGDS inhibited HT-29LMM cell adhesion to FN only. Pretreatment with anti-beta, or anti-alpha2 integrin subunits suppressed adhesion to C I and C IV, and adhesion to LN was inhibited with anti-beta1 or anti-alpha6 integrin. Anti-beta1 or anti-alphav blocked adhesion to FN. Pretreatment of cells with cytochalasin D, cycloheximide or acrylamide inhibited adhesive interactions of both cell lines to the ECM components. In contrast, colchicine and nocodazole had no effect. The results demonstrate that adhesion of HT-29 cells to ECM is mediated, in part, by different integrins, depending on the substrate. Poorly and highly metastatic HT-29 cells possessed different patterns of adhesion to the various ECM substrates, but these differences were not due to different expression of integrin subunits. The results also suggested that the initial adhesion of poorly or highly metastatic HT-29 cells to ECM components requires, in part, the presence of native action and intermediate filaments, but not of microtubules. Thus the adhesion of tumour cells to ECM components may be dependent on signal transduction and assembly of microfilaments.
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Affiliation(s)
- J Haier
- The Institute for Molecular Medicine, Huntington Beach, CA 92649, USA
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32
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Saltarelli D. Heterotrimetric Gi/o proteins control cyclic AMP oscillations and cytoskeletal structure assembly in primary human granulosa-lutein cells. Cell Signal 1999; 11:415-33. [PMID: 10400315 DOI: 10.1016/s0898-6568(99)00012-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In granulosa cells, the luteinising hormone (LH) and the follicle-stimulating hormone (FSH) receptors are coupled to the adenylyl cyclase-cAMP pathway. We identified at least eight different G proteins belonging to three families--Gs, Gq, and Gi/o--in primary human granulosa-lutein cells. By exploring the function of Gi/o by time-lapse and digital-imaging microscopy of live cells, we found that the reversible actin stress fibre-dependent cytoplasmic retraction of pre-luteinised cells in primary culture is a highly sensitive and quite rapid system allowing detection of an intracellular cAMP surge. This morphology was characterised by maintenance of connexin43-dependent cell-cell contacts and that of microtubule-directed cell processes attached to the substrate and to neighbouring cells. Inhibitors of cyclic nucleotide phosphodiesterase subfamily type 4 (PDE-4), hLH and hFSH provoked this reversible cAMP-dependent phenotype in a temporal-, spatial- and dose-dependent manner. Gi/o inhibited adenylyl cyclase in membranes, and cell treatment with islet-activating protein (IAP) caused the cAMP-dependent retracted phenotype. It is concluded that the basal intracellular cAMP level is kept within a narrow range of concentrations, below the threshold for disassembly of stress fibres, through Gs, Gi/o, adenylyl cyclases and phosphodiesterase-4. This work supports the paradigm that switching of the agonist-occupied receptors to Gs and Gi/o would control both the intracellular bursts of cAMP (through the gonadotropin-catalysed activation of Gs) and the basal cAMP (through a Gi/o-mediated braking effect).
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Affiliation(s)
- D Saltarelli
- Laboratoire de Biochimie Hormonale, Groupe Hospitalier Cochin, Paris, France.
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Turowski P, Myles T, Hemmings BA, Fernandez A, Lamb NJ. Vimentin dephosphorylation by protein phosphatase 2A is modulated by the targeting subunit B55. Mol Biol Cell 1999; 10:1997-2015. [PMID: 10359611 PMCID: PMC25403 DOI: 10.1091/mbc.10.6.1997] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The intermediate filament protein vimentin is a major phosphoprotein in mammalian fibroblasts, and reversible phosphorylation plays a key role in its dynamic rearrangement. Selective inhibition of type 2A but not type 1 protein phosphatases led to hyperphosphorylation and concomitant disassembly of vimentin, characterized by a collapse into bundles around the nucleus. We have analyzed the potential role of one of the major protein phosphatase 2A (PP2A) regulatory subunits, B55, in vimentin dephosphorylation. In mammalian fibroblasts, B55 protein was distributed ubiquitously throughout the cytoplasm with a fraction associated to vimentin. Specific depletion of B55 in living cells by antisense B55 RNA was accompanied by disassembly and increased phosphorylation of vimentin, as when type 2A phosphatases were inhibited using okadaic acid. The presence of B55 was a prerequisite for PP2A to efficiently dephosphorylate vimentin in vitro or to induce filament reassembly in situ. Both biochemical fractionation and immunofluorescence analysis of detergent-extracted cells revealed that fractions of PP2Ac, PR65, and B55 were tightly associated with vimentin. Furthermore, vimentin-associated PP2A catalytic subunit was displaced in B55-depleted cells. Taken together these data show that, in mammalian fibroblasts, the intermediate filament protein vimentin is dephosphorylated by PP2A, an event targeted by B55.
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Affiliation(s)
- P Turowski
- Cell Biology Unit, Institut de Genetique Humaine, Centre National de la Recherche Scientifique UPR 1142, F-34396 Montpellier Cedex 5, France
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Martys JL, Ho CL, Liem RK, Gundersen GG. Intermediate filaments in motion: observations of intermediate filaments in cells using green fluorescent protein-vimentin. Mol Biol Cell 1999; 10:1289-95. [PMID: 10233144 PMCID: PMC25258 DOI: 10.1091/mbc.10.5.1289] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- J L Martys
- Departments of Anatomy and Cell Biology and Pathology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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Zhou X, Liao J, Hu L, Feng L, Omary MB. Characterization of the major physiologic phosphorylation site of human keratin 19 and its role in filament organization. J Biol Chem 1999; 274:12861-6. [PMID: 10212274 DOI: 10.1074/jbc.274.18.12861] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Keratin polypeptide 19 (K19) is a type I intermediate filament protein that is expressed in stratified and simple-type epithelia. Little is known regarding K19 regulation or function, and the only other type I keratin that has been studied in terms of regulation is keratin 18 (K18). We characterized K19 phosphorylation as a handle to study its function. In vivo, serine is the major phosphorylated residue, and phosphopeptide mapping of 32PO4-labeled K19 generates one major phosphopeptide. Edman degradation suggested that the radiolabeled phosphopeptide represents K19 Ser-10 and/or Ser-35 phosphorylation. Mutation of Ser-10 or Ser-35 followed by transfection confirmed that Ser-35 is the major K19 phosphorylation site. Transfection of Ser-35 --> Ala K19 showed a filament assembly defect as compared with normal or with Ser-10 --> Ala K19. Comparison of K18 and K19 phosphorylation features in interphase cells showed that both are phosphorylated primarily at a single site, preferentially in the soluble versus the insoluble keratin fractions. K19 has higher basal phosphorylation, whereas K18 phosphorylation is far more sensitive to phosphatase type I and IIA inhibition. Our results demonstrate that Ser-35 is the major K19 interphase phosphorylation site and that it plays a role in keratin filament assembly. K19 and K18 phosphorylations share some features but also have distinct properties that suggest different regulation of type I keratins within the same cells.
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Affiliation(s)
- X Zhou
- Veterans Affairs Palo Alto Health Care System and Stanford University Digestive Disease Center, Palo Alto, California 94304, USA
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36
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Abstract
Keratins undergo highly dynamic events in the epithelial cells that express them. These dynamic changes have been associated with important cell processes. We have studied the possible role of keratin phosphorylation-dephosphorylation processes in the control of these dynamic events. Drugs that affect the protein phosphorylation metabolism (activators or inhibitors of protein kinases or protein phosphatases) have been used in two different dynamic experimental systems. First, the behaviour of keratins after the formation of cell heterokaryons, and second, the assembly of a newly synthesised keratin after transfection into the pre-existing keratin cytoskeleton. The main difference between these two systems stems on the alteration of the amount of keratin polypeptides present in the cells, since in heterokaryons this amount was unaltered whilst in transfection experiments there is an increase due to the presence of the transfected protein. We observed in both systems that the inhibition of protein kinases led to a delayed dynamic behaviour of the keratin polypeptides. On the contrary, the inhibition of protein phosphatases by okadaic acid or the activation of protein kinases by phorbol esters promoted a substantial increase in the kinetics of these processes. Biochemical studies demonstrate that this behavioural changes can be correlated with changes in the phosphorylation state of the keratin polypeptides. As a whole, present results indicate that the highly dynamic properties of the keratin polypeptides can be modulated by phosphorylation.
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Affiliation(s)
- J M Paramio
- Cell and Molecular Biology Program, CIEMAT (IMA), Madrid, Spain.
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37
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Hartig R, Shoeman RL, Janetzko A, Tolstonog G, Traub P. DNA-mediated transport of the intermediate filament protein vimentin into the nucleus of cultured cells. J Cell Sci 1998; 111 ( Pt 24):3573-84. [PMID: 9819349 DOI: 10.1242/jcs.111.24.3573] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A number of characteristic properties of intermediate filament (IF) proteins, such as nucleic acid-binding activity, affinity for histones and structural relatedness to transcription factors and nuclear matrix proteins, in conjunction with the tight association of IFs with the nucleus, suggest that these proteins might also fulfill nuclear functions in addition to their structure-organizing and -stabilizing activities in the cytoplasm. Yet, cytoplasmic IF proteins do not possess nuclear localization signals. In a search for carriers capable of transporting the IF protein vimentin into the nucleus, complexes of FITC-vimentin with various DNAs were microinjected into the cytoplasm of cultured cells and the intracellular distribution of the protein was followed by confocal laser scanning microscopy. The single-stranded oligodeoxyribonucleotides oligo(dG)25, oligo[d(GT)12G] and oligo[d(G3T2A)4G] proved to be excellent nuclear carriers for vimentin. However, in fibroblasts, fluorescence-labeled vimentin taken up by the nuclei remained undetectable with affinity-purified, polyclonal anti-vimentin antibody, whereas it was readily identifiable in the nuclei of microinjected epithelial cells in this way. Moreover, when FITC-vimentin was preinjected into fibroblasts and allowed to assemble into the endogenous vimentin filament system, it was still transferred into the nucleus by post-injected oligo(dG)25, although to a lesser extent. Superhelical circular DNAs, like pBR322, SV40 and mitochondrial DNA, were also characterized by considerable capacities for nuclear vimentin transport; these transport potentials were totally destroyed by relaxation or linearization of the DNA molecules. Nevertheless, certain linear double-stranded DNA molecules with a high affinity for vimentin IFs, such as repetitive telomere and centromere or mobile long interspersed repeat (LINE) DNA, could carry FITC-vimentin into the nucleus. This was also true for a 375 bp extrachromosomal linear DNA fragment which occurs in the cytoplasm of mouse tumor cells and which is capable of immortalizing human lymphocytes. On the basis of these results, it appears very likely that cellular and viral products of reverse transcription as well as other extrachromosomal DNAs, which are circular, superhelical and apparently shuttling between the cytoplasm and the nucleus (eccDNA), are constantly loaded with vimentin in vimentin-positive cells. Since such DNAs are considered as markers of genomic instability, it is conceivable that vimentin directly participates as an architectural, chromatin-modifying protein in recombinatorial processes set off by these DNAs in the nucleus.
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Affiliation(s)
- R Hartig
- Max-Planck-Institut für Zellbiologie, D-68526 Ladenburg/Heidelberg, Germany
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38
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Cheng TJ, Lai YK. Identification of mitogen-activated protein kinase-activated protein kinase-2 as a vimentin kinase activated by okadaic acid in 9L rat brain tumor cells. J Cell Biochem 1998. [DOI: 10.1002/(sici)1097-4644(19981101)71:2<169::aid-jcb3>3.0.co;2-t] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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39
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Sin WC, Chen XQ, Leung T, Lim L. RhoA-binding kinase alpha translocation is facilitated by the collapse of the vimentin intermediate filament network. Mol Cell Biol 1998; 18:6325-39. [PMID: 9774649 PMCID: PMC109219 DOI: 10.1128/mcb.18.11.6325] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The regulation of morphological changes in eukaryotic cells is a complex process involving major components of the cytoskeleton including actin microfilaments, microtubules, and intermediate filaments (IFs). The putative effector of RhoA, RhoA-binding kinase alpha (ROKalpha), is a serine/threonine kinase that has been implicated in the reorganization of actin filaments and in myosin contractility. Here, we show that ROKalpha also directly affects the structural integrity of IFs. Overexpression of active ROKalpha, like that of RhoA, caused the collapse of filamentous vimentin, a type III IF. A RhoA-binding-deficient, kinase-inactive ROKalpha inhibited the collapse of vimentin IFs induced by RhoA in HeLa cells. In vitro, ROKalpha bound and phosphorylated vimentin at its head-rod domain, thereby inhibiting the assembly of vimentin. ROKalpha colocalized predominantly with the filamentous vimentin network, which remained intact in serum-starved cells. Treatment of cells with vinblastine, a microtubule-disrupting agent, also resulted in filamentous vimentin collapse and concomitant ROKalpha translocation to the cell periphery. ROKalpha translocation did not occur when the vimentin network remained intact in vinblastine-treated cells at 4 degreesC or in the presence of the dominant-negative RhoAN19 mutant. Transient translocation of ROKalpha was also observed in cells subjected to heat shock, which caused the disassembly of the vimentin network. Thus, the translocation of ROKalpha to the cell periphery upon overexpression of RhoAV14 or growth factor treatment is associated with disassembly of vimentin IFs. These results indicate that Rho effectors known to act on microfilaments may be involved in regulating the assembly of IFs. Vimentin when phosphorylated also exhibits reduced affinity for the inactive ROKalpha. The translocation of ROKalpha from IFs to the cell periphery upon action by activated RhoA and ROKalpha suggests that ROKalpha may initiate its own cascade of activation.
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Affiliation(s)
- W C Sin
- Glaxo-IMCB Group, Institute of Molecular and Cell Biology, Singapore 117609, Singapore
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40
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Pryzwansky KB, Merricks EP. Chemotactic peptide-induced changes of intermediate filament organization in neutrophils during granule secretion: role of cyclic guanosine monophosphate. Mol Biol Cell 1998; 9:2933-47. [PMID: 9763453 PMCID: PMC25570 DOI: 10.1091/mbc.9.10.2933] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In neutrophils activated to secrete with formyl-methionyl-leucyl-phenylalanine, intermediate filaments are phosphorylated transiently by cyclic guanosine monophosphate (cGMP)-dependent protein kinase (G-kinase). cGMP regulation of vimentin organization was investigated. During granule secretion, cGMP levels were elevated and intermediate filaments were transiently assembled at the pericortex to areas devoid of granules and microfilaments. Microtubule and microfilament inhibitors affected intermediate filament organization, granule secretion, and cGMP levels. Cytochalasin D and nocodazole caused intermediate filaments to assemble at the nucleus, rather than at the pericortex. cGMP levels were elevated in neutrophils by both inhibitors; however, with cytochalasin D, cGMP was elevated earlier and granule secretion was excessive. Nocodazole did not affect normal cGMP elevations, but specific granule secretion was delayed. LY83583, a guanylyl cyclase antagonist, inhibited granule secretion and intermediate filament organization, but not microtubule or microfilament organization. Intermediate filament assembly at the pericortex and secretion were partially restored by 8-bromo-cGMP in LY83583-treated neutrophils, suggesting that cGMP regulates these functions. G-kinase directly induced intermediate filament assembly in situ, and protein phosphatase 1 disassembled filaments. However, in intact cells stimulated with formyl-methionyl-leucyl-phenylalanine, intermediate filament assembly is focal and transient, suggesting that vimentin phosphorylation is compartmentalized. We propose that, in addition to changes in microfilament and microtubule organization, granule secretion is also accompanied by changes in intermediate filament organization, and that cGMP regulates vimentin filament organization via activation of G-kinase.
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Affiliation(s)
- K B Pryzwansky
- Department of Pathology, University of North Carolina, Chapel Hill, North Carolina 27599-7525, USA
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Gao X, Hagmann W, Zacharek A, Wu N, Lee M, Porter AT, Honn KV. Eicosanoids, cancer metastasis, and gene regulation: an overview. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 400A:545-55. [PMID: 9547603 DOI: 10.1007/978-1-4615-5325-0_74] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- X Gao
- Department of Radiation Oncology, Wayne State University School of Medicine, Detroit 48202, USA
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Young MR, Lozano Y, Djordjevic A, Maier GD, Young ME. Tumor responsiveness to the metastasis-stimulatory effects of prostaglandin E2 is restricted by protein phosphatases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 400A:323-8. [PMID: 9547574 DOI: 10.1007/978-1-4615-5325-0_45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- M R Young
- Research Services, Hines V.A. Hospital, Hines, IL 60141, USA
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Chu JJ, Chen KD, Lin YL, Fei CY, Chiang AS, Chiang CD, Lai YK. Taxol induces concomitant hyperphosphorylation and reorganization of vimentin intermediate filaments in 9l rat brain tumor cells. J Cell Biochem 1998. [DOI: 10.1002/(sici)1097-4644(19980315)68:4<472::aid-jcb7>3.0.co;2-n] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Vinadé L, Gonçalves CA, Wofchuk S, Gottfried C, Rodnight R. Evidence for a role for calcium ions in the dephosphorylation of glial fibrillary acidic protein (GFAP) in immature hippocampal slices and in astrocyte cultures from the rat. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1997; 104:11-7. [PMID: 9466703 DOI: 10.1016/s0165-3806(97)00114-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Evidence was sought for a role for Ca2+ in the dephosphorylation of the astrocyte marker glial fibrillary acidic protein (GFAP) in immature hippocampal slices. Although previous work showed that the main phosphatase dephosphorylating GFAP in this preparation is a Ca2+-independent type 1 enzyme, a role for Ca2+ was suggested by the observation that the incorporation of [32P]phosphate into GFAP in immature slices is inhibited by external Ca2+. This inhibition is strikingly different to the situation in mature slices where GFAP phosphorylation is completely dependent on Ca2+. Pure astrocyte cultures were probed by immunoblotting for the presence of the Ca2+-dependent phosphatase calcineurin. An enzyme content, amounting to about 2% of that found in fresh hippocampal tissue, was detected for both the catalytic (alpha) and regulatory (beta) subunits. The direct or indirect association of calcineurin with GFAP was suggested by observations showing that FK506, a specific inhibitor of calcineurin, increased the phosphorylation state of GFAP in immature slices and of GFAP and vimentin in astrocyte cultures.
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Affiliation(s)
- L Vinadé
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, UFRGS (Centro), Porto Alegre RS, Brazil
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Dremier S, Pohl V, Poteet-Smith C, Roger PP, Corbin J, Doskeland SO, Dumont JE, Maenhaut C. Activation of cyclic AMP-dependent kinase is required but may not be sufficient to mimic cyclic AMP-dependent DNA synthesis and thyroglobulin expression in dog thyroid cells. Mol Cell Biol 1997; 17:6717-26. [PMID: 9343436 PMCID: PMC232526 DOI: 10.1128/mcb.17.11.6717] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Thyrotropin (TSH), via a cyclic AMP (cAMP)-dependent pathway, induces cytoplasmic retractions, proliferation, and differentiation expression in dog thyroid cells. The role of cAMP-dependent protein kinase (PKA) in the induction of these events was assessed by microinjection into living cells. Microinjection of the heat-stable inhibitor of PKA (PKI) inhibited the effects of TSH, demonstrating that activation of PKA was required in this process. Overexpression of the catalytic (C) subunit of PKA brought about by microinjection of the expression plasmid pC alpha ev or of purified C subunit itself was sufficient to mimic the cAMP-dependent cytoplasmic changes and thyroperoxidase mRNA expression but not to induce DNA synthesis and thyroglobulin (Tg) expression. The cAMP-dependent morphological effect was not observed when C subunit was coinjected with the regulatory subunit (RI or RII subunit) of PKA. To mimic the cAMP-induced PKA dissociation into free C and R subunits, the C subunit was coinjected with the regulation-deficient truncated RI subunit (RIdelta1-95) or with wild-type RI or native RII subunits, followed by incubation with TSH at a concentration too low to stimulate the cAMP-dependent events by itself. Although the cAMP-dependent morphology changes were still observed, neither DNA synthesis nor Tg expression was stimulated in these cells. Taken together, these data suggest that in addition to PKA activation, another cAMP-dependent mechanism could exist and play an important role in the transduction of the cAMP signal in thyroid cells.
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Affiliation(s)
- S Dremier
- Institute of Interdisciplinary Research (I.R.I.B.H.N.), Université Libre de Bruxelles, Brussels, Belgium.
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Young MR. Protein phosphatases-1 and -2A regulate tumor cell migration, invasion and cytoskeletal organization. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 407:311-8. [PMID: 9321969 DOI: 10.1007/978-1-4899-1813-0_46] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The role of protein kinase A (PKA) and protein phosphatases (PP) -1 and -2A in regulating the metastatic phenotype of Lewis lung carcinoma (LLC) cells was evaluated. The metastatic LLC-LN7 cells were more motile and invasive than were nonmetastatic LLC-C8 cells. Compared to the nonmetastatic cells, the LLC-LN7 cells had increased PKA activity and a deficiency in PP-2A. Nonmetastatic LLC-C8 cells became migratory and invasive when PP-1 and P-2A activities were inhibited with okadaic acid. This stimulation of LLC-C8 motility was tempered by PKA inhibition. Also examined was if the okadaic acid-stimulated LLC-C8 motility was associated with a change in the cytoskeletal organization to that typical of metastatic cells. Treatment of nonmetastatic LLC-C8 cells with okadaic acid caused a redistribution of F-actin toward the periphery of the cells, and eventually to a loss of the filamentous actin network. All of these effects were reversed upon removal of okadaic acid. Our results show that PP-1/2A maintain reduced motility and increased cytoskeletal organization within nonmetastatic LLC cells.
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Affiliation(s)
- M R Young
- Research Service (151-Z2) Hines V.A. Hospital, IL 60141, USA
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Borowski P, Oehlmann K, Heiland M, Laufs R. Nonstructural protein 3 of hepatitis C virus blocks the distribution of the free catalytic subunit of cyclic AMP-dependent protein kinase. J Virol 1997; 71:2838-43. [PMID: 9060639 PMCID: PMC191408 DOI: 10.1128/jvi.71.4.2838-2843.1997] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Chronic hepatitis resulting from hepatitis C virus (HCV) infection develops into cirrhosis in at least half of infected patients and increases the risk of hepatocellular carcinoma. The pathogenic effects of a number of viruses result from the disturbance of intracellular signal cascades caused by viral antigens. Therefore, we investigated the interaction of nonstructural protein 3 (NS3) of HCV with the cyclic AMP-dependent signal pathway. We found a similarity between the HCV sequence Arg-Arg-Gly-Arg-Thr-Gly-Arg-Gly-Arg-Arg-Gly-Ile-Tyr-Arg localized in NS3 and the general consensus sequence of protein kinase A (PKA). Consequently, the catalytic (C) subunit of PKA bound to a bacterially expressed fragment of HCV polyprotein containing amino acid residues 1189 to 1525. When this fragment was introduced into cells, it inhibited the translocation of the C subunit into the nucleus after stimulation with forskolin. The result of this inhibition was significantly reduced histone phosphorylation. Therefore, the presence of NS3 in the cytoplasm of infected cells may affect a wide range of PKA functions and contribute to the pathogenesis of the diseases caused by HCV.
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Affiliation(s)
- P Borowski
- Institut für Medizinische Mikrobiologie und Immunologie, Universitätskrankenhaus Eppendorf, Hamburg, Germany
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48
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Abstract
The problem for the steroidogenic cell if it is to accelerate steroid synthesis in response to trophic stimulation, consists in moving cholesterol from the sites of synthesis and storage to mitochondria at an accelerated rate. The most intensely studied situation is that in which the sterol is stored as ester in lipid droplets. Cholesterol ester must be de-esterified and transported to mitochondria where steroid synthesis begins. Since droplets and mitochondria are now known to be attached to intermediate filaments and since these structures are not contractile, it appears to be necessary to invoke the actions of other cytoskeletal elements. Actin microfilaments are involved in cholesterol transport so that it is tempting to propose that the contractile properties of actomyosin are used in this process. It is known that an energy-dependent contractile process involving actin is capable of disrupting intermediate filaments. Since the intermediate filaments appear to act by keeping lipid droplets and mitochondria apart, disruption of the filaments accompanied by a contractile process would be expected to allow these two structures to come together. This would open the way for the transfer of cholesterol to the steroidogenic pathway. This should be regarded as a first step. The events necessary for entry of cholesterol from droplets into the mitochondria remain to be clarified. In addition, the transport process for newly synthesized cholesterol that is not stored in droplets, is still not understood. At least four protein kinase enzymes have been identified in the cytoskeletons of adrenal cells, namely, Ca2+/calmodulin-dependent kinase, protein kinase (Ca2+ and phospholipid-dependent), myosin light chain kinase, and protein kinase A (cyclic AMP-dependent). The Ca2+/calmodulin kinase promotes transport of cholesterol to mitochondria and does so under conditions in which phosphorylation of vimentin and myosin light chain occurs. Phosphorylation of vimentin results in disruption of intermediate filaments while phosphorylation of light chain promotes contraction of the actomyosin ring. It now appears that intermediate filaments are cross-linked by actin filaments so that such contraction would be expected to produce significant structural changes in the cytoskeleton and the attached organelles. Although the details of the changes taking place in the organ in vivo are not known, the potential for interaction between droplets and mitochondria as the result of these changes in intermediate filaments and actomyosin, is clear. Protein kinase C is activated by ACTH and cyclic AMP, although this activation does not appear to be directly involved in the regulation of steroid synthesis. Nevertheless, vimentin is a substrate for this enzyme, and changes in the organisation of vimentin filaments and the attached organelles under the influence of protein kinase C have been reported in other cells. Presumably these changes represent part of the response to ACTH because when protein kinase C is activated by phorbol ester, the cytoskeletal changes necessary for rounding up take place but such changes are not accompanied by increased steroid synthesis. Protein kinase A causes rounding of adrenal cells. and cytoskeletons. This kinase also causes increased cholesterol transport and, hence, stimulation of steroid synthesis. The enzyme also causes phosphorylation of vimentin but with a different cytoskeletal reorganisation from that seen with the other three kinase enzymes. Clearly phosphorylation plays a major role in these responses. Phosphorylation alters the morphology and the functions of the cytoskeleton and this, in turn, is associated with accelerated cholesterol transport. It is now necessary to define the details of the specific phosphorylation reactions that occur during the response to ACTH, that is, which amino acids are phosphorylated and to what extent by each of the kinase enzymes.
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Affiliation(s)
- P F Hall
- Department of Endocrinology, Prince of Wales Hospital, Randwick, NSW, Australia
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Young MR, Lozano Y. Inhibition of tumor invasiveness by 1alpha,25-dihydroxyvitamin D3 coupled to a decline in protein kinase A activity and an increase in cytoskeletal organization. Clin Exp Metastasis 1997; 15:102-10. [PMID: 9062386 DOI: 10.1023/a:1018492525027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The capacity of cloned metastatic Lewis lung carcinoma cells (LLC-LN7) to invade through reconstituted basement membrane-coated filters was reduced after incubation with 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. This was observed at doses as low as 10(-10) M 1,25(OH)2D3. The 1,25(OH)2D3-treated cells also had reduced levels of protein kinase A (PKA) activity and an increase in the level of polymerized actin, properties that have previously been demonstrated for less metastatic LLC variants. In addition, levels of the intermediate filament protein vimentin increased in 1,25(OH)2D3-treated LLC-LN7 tumor cells. In contrast, the levels and distribution of tubulin were not affected by 1,25(OH)2D3. The possibility that the decline in PKA activity was involved in the 1,25(OH)2D3 modulation of the cytoskeletal components was evaluated. To accomplish this, LLC-7 transfectants whose PKA levels were blocked due to expression of a mutated PKA R(1alpha) subunit (LN7-REV) were incubated with 1,25(OH)2D3 and their levels of F-actin were measured. In the absence of 1,25(OH)2D3 treatment, the PKA-defective LN7-REV cells had an increased level of polymerized actin as compared to the wild-type LLC-LN7 cells. This level of F-actin was minimally affected by 1,25(OH)2D3, suggesting that PKA activity is required for 1,25(OH)2D3 modulation of actin polymerization. These studies show that 1,25(OH)2D3 can reduce PKA activity in tumor cells, and that this reduction in PKA may be an intermediate signal through which 1,25(OH)2D3 affects the cytoskeleton and diminishes tumor invasiveness.
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Affiliation(s)
- M R Young
- Department of Research Services, Hines V.A. Hospital, IL 60141, USA.
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50
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Meisinger J, Patel S, Vellody K, Bergstrom R, Benefield J, Lozano Y, Young MR. Protein phosphatase-2A association with microtubules and its role in restricting the invasiveness of human head and neck squamous cell carcinoma cells. Cancer Lett 1997; 111:87-95. [PMID: 9022132 DOI: 10.1016/s0304-3835(96)04517-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The role of protein phosphatase-2A (PP-2A) in regulating the motility and adhesion of human head and neck squamous cell carcinomas (HNSCC) was investigated. Immunofluorescent staining of these HNSCC cells showed PP-2A can co-localize with microtubules. That the PP-2A influences motility was shown by the increase in HNSCC cell migration through laminin and vitronectin when PP-2A was selectively inhibited with low dose okadaic acid, and by the reduction in invasion through these same matrix components by elevators of PP-2A activity. Motility of HNSCC cells through collagen I or fibronectin was not modulated by PP-2A. The reduction in HNSCC migration through vitronectin or laminin that resulted from treatment with PP-2A elevators was associated with an increase in cellular adhesiveness to these same ECM components. These studies show the association of PP-2A with the cellular cytoskeleton and its role in restricting the invasiveness of tumor cells through select extracellular matrix components.
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Affiliation(s)
- J Meisinger
- Department of Research Services, Hines V.A. Hospital, IL 60141, USA
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