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David MD, Petit D, Bertoglio J. The RhoGAP ARHGAP19 controls cytokinesis and chromosome segregation in T lymphocytes. J Cell Sci 2013; 127:400-10. [PMID: 24259668 DOI: 10.1242/jcs.135079] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Small GTP-binding proteins of the Rho family orchestrate the cytoskeleton remodelling events required for cell division. Guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) promote cycling of Rho GTPases between the active GTP-bound and the inactive GDP-bound conformations. We report that ARHGAP19, a previously uncharacterised protein, is predominantly expressed in hematopoietic cells and has an essential role in the division of T lymphocytes. Overexpression of ARHGAP19 in lymphocytes delays cell elongation and cytokinesis. Conversely, silencing of ARHGAP19 or expression of a GAP-deficient mutant induces precocious mitotic cell elongation and cleavage furrow ingression, as well as excessive blebbing. In relation to these phenotypes, we show that ARHGAP19 acts as a GAP for RhoA, and controls recruitment of citron and myosin II to the plasma membrane of mitotic lymphocytes as well as Rock2-mediated phosphorylation of vimentin, which is crucial to maintain the stiffness and shape of lymphocytes. In addition to its effects on cell shape, silencing of ARHGAP19 in lymphocytes also impairs chromosome segregation.
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Affiliation(s)
- Muriel D David
- Inserm U749, Institut Gustave Roussy, 94805 Villejuif, France
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2
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Gao YS, Vrielink A, MacKenzie R, Sztul E. A novel type of regulation of the vimentin intermediate filament cytoskeleton by a Golgi protein. Eur J Cell Biol 2002; 81:391-401. [PMID: 12160147 DOI: 10.1078/0171-9335-00260] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Whether the highly dynamic structure of the vimentin intermediate filament (IF) cytoskeleton responds to cues from cellular organelles, and what proteins might participate in such events is largely unknown. We have shown previously that the Golgi protein formiminotransferase cyclodeaminase (FTCD) binds to vimentin filaments in vivo and in vitro, and that overexpression of FTCD causes dramatic rearrangements of the vimentin IF cytoskeleton (Gao and Sztul, J. Cell Biol. 152, 877-894, 2001). Using real-time imaging, we now show that FTCD causes bundling of individual thinner vimentin filaments into fibers and that the bundling always originates at the Golgi. FTCD appears to be the molecular "glue" since FTCD cross-links vimentin filaments in vitro. To initiate the analysis of structural determinants required for FTCD function in vimentin dynamics, we used structure-based design to generate individual formiminotransferase (FT) and cyclodeaminase (CD) domains, and to produce an enzymatically inactive FTCD. We show that the intact octameric structure is required for FTCD binding to vimentin filaments and for promoting filament assembly, but that eliminating enzymatic activity does not affect FTCD effects on the vimentin cytoskeleton. Our findings indicate that the Golgi protein FTCD is a potent modulator of the vimentin IF cytoskeleton, and suggest that the Golgi might act as a reservoir for proteins that regulate cytoskeletal dynamics.
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Affiliation(s)
- Ya-Sheng Gao
- Department of Cell Biology, University of Alabama at Birmingham, 35294, USA
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Henics T, Nagy E, Szekeres-Barthó J. Interaction of AU-rich sequence binding proteins with actin: possible involvement of the actin cytoskeleton in lymphokine mRNA turnover. J Cell Physiol 1997; 173:19-27. [PMID: 9326445 DOI: 10.1002/(sici)1097-4652(199710)173:1<19::aid-jcp3>3.0.co;2-m] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In the current study, we report that cytochalasin-induced disruption of microfilaments stabilizes lymphokine mRNAs in activated human peripheral blood lymphocytes. Parallel with this, a dose- and time-dependent increase in AU-rich sequence binding protein (AUPB) activities is apparent in the nonionic detergent-resistant fractions of these cells, suggesting that cytochalasin-induced modulation of lymphokine mRNA stability might be mediated through cytoplasmic AUBPs. We provide evidence that some of the AUBPs can be immunoprecipitated with anti-actin antibodies, implicating the potential of these proteins to associate with the actin-based cytoskeleton in vivo. Moreover, disruption of the microfilament network by cytochalasins produces increased immunoprecipitable actin-AUBP complexes in the detergent-resistant cytoplasmic subfractions of lymphocytes. We show that cytochalasin-induced changes in AUBP activities are parallel with their higher binding affinity to RNA containing AU-rich instability sequence element as judged by in vitro competition and in vivo ultraviolet-crosslinking analysis. Correlation of these findings with changes in mRNA stability indicates that the actin cytoskeleton may play a physiologically important role in posttranscriptional regulation of lymphokine gene expression during early lymphocyte activation.
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Affiliation(s)
- T Henics
- Department of Microbiology, University Medical School of Pécs, Hungary.
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Vikstrom KL, Lim SS, Goldman RD, Borisy GG. Steady state dynamics of intermediate filament networks. J Biophys Biochem Cytol 1992; 118:121-9. [PMID: 1618899 PMCID: PMC2289530 DOI: 10.1083/jcb.118.1.121] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have conducted experiments to examine the dynamic exchange between subunit and polymer of vimentin intermediate filaments (IF) at steady state through the use of xrhodamine-labeled vimentin in fluorescence recovery after photobleaching (FRAP) analysis. The xrhodamine-vimentin incorporated into the endogenous vimentin IF network after microinjection into fibroblasts and could be visualized with a cooled charge-coupled device (CCD) camera and digital imaging fluorescence microscopy. Bar shaped regions were bleached in the fluorescent IF network using a beam from an argon ion laser and the cells were monitored at various times after bleaching to assess recovery of fluorescence in the bleached zones. We determined that bleached vimentin fibers can recover their fluorescence over relatively short time periods. Vimentin fibers in living cells also can exhibit significant movements, but the recovery of fluorescence was not dependent upon movement of fibers. Fluorescence recovery within individual fibers did not exhibit any marked polarity and was most consistent with a steady state exchange of vimentin subunits along the lengths of IF.
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Affiliation(s)
- K L Vikstrom
- Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, Chicago, Illinois 60611
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Roy C, Brown DL, Little JE, Valentine BK, Walker PR, Sikorska M, Leblanc J, Chaly N. The topoisomerase II inhibitor teniposide (VM-26) induces apoptosis in unstimulated mature murine lymphocytes. Exp Cell Res 1992; 200:416-24. [PMID: 1315287 DOI: 10.1016/0014-4827(92)90190-j] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
This study shows that not only concanavalin A-stimulated proliferating lymphocytes but also unstimulated mouse splenic lymphocytes are sensitive to the topoisomerase II (topo II) inhibitor teniposide (VM-26). When unstimulated lymphocytes are pretreated with VM-26 for a 2-h period and are then incubated in drug-free medium, cell viability, as determined by trypan blue exclusion, decreases to 40% of the control by 6 h. The drug-treated cultures show two to three times the level of detergent soluble DNA than the control cultures and agarose gel electrophoresis of the soluble DNA shows the presence of oligonucleosomal-sized fragments, a feature considered to be a hallmark of apoptosis. Phase contrast microscopy, Hoechst staining for DNA, and immunofluorescence microscopy of various nuclear and cytoplasmic antigens (nucleolar fibrillarin, snRNP, ubiquitin, vimentin, tubulin) in the VM-26-treated cells characterize the morphological changes during apoptosis of these cells. The role of topo II as the mediator of the VM-26 effects is supported by pulsed field gel electrophoresis, which shows the typical topo II-induced cleavage of supercoiled DNA into loop-sized 300- and 50-kbp fragments. We conclude that the cancer chemotherapeutic agent VM-26 interacts with topo II and induces apoptosis in unstimulated lymphocytes.
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Affiliation(s)
- C Roy
- Department of Biology, University of Ottawa, Canada
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6
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Paulin-Levasseur M, Julien M. Expression of intermediate filament proteins in TPA-induced MPC-11 and HL-60 cells. Exp Cell Res 1992; 199:363-72. [PMID: 1544377 DOI: 10.1016/0014-4827(92)90446-f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Under normal culture conditions, the tumor cell lines MPC-11 and HL-60 exhibit high rates of proliferation and show a peculiar expression of intermediate filament proteins as they appear to synthesize only lamin B. A 48-h exposure of murine plasmacytomas MPC-11 to the phorbol ester TPA reduces their growth and induces vimentin synthesis without affecting the composition of their nuclear lamina. When applied to human leukemic promyelocytes HL-60, such treatment promotes their maturation into macrophage-like cells: their proliferative ability is suppressed, a differentiated phenotype is developed, and their content in intermediate filament proteins now includes vimentin and a full complement of lamins A, B, and C. In the present study, a kinetic analysis of vimentin and lamin A/C expression in relation to proliferation and differentiation has been performed in these two cellular systems. Proliferation rates of MPC-11 and HL-60 populations were evaluated by monitoring cell growth and measuring thymidine incorporation. Maturation of HL-60 cells was assessed by Giemsa staining and percentage of adherent cells. Expression of vimentin and lamins A/C was analyzed using immunofluorescence and immunoblotting techniques. Our data show that there is a relationship between the level of vimentin expression and the extent of growth inhibition in both systems. They also suggest that the expression of lamins A/C during the TPA-induced maturation of HL-60 promyelocytes might be part of the processes which lock these cells into the macrophage pathway.
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Knox JD, Mitchel RE, Brown DL. Effects of hyperthermia on microtubule organization and cytolytic activity of murine cytotoxic T lymphocytes. Exp Cell Res 1991; 194:275-83. [PMID: 2026179 DOI: 10.1016/0014-4827(91)90365-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
When murine cytotoxic T lymphocytes (CTL) are heated at 42 degrees C for 30 min their ability to lyse their target cells (TC) is severely impaired. When the CTL are allowed to recover at 37 degrees C, a partial recovery of cytolytic activity that peaks within 6 h is observed. A dye exclusion assay demonstrated that such a heat shock does not affect the viability of the CTL and direct microscopic observations established that their ability to bind to TC is not impaired. Therefore, the step or steps inhibited by hyperthermia are subsequent to TC recognition and binding. Kupfer et al. ((1983) Proc. Natl. Acad. Sci. USA 80, 7224-7228) demonstrated that upon binding to an appropriate TC, a rapid orientation of the Golgi apparatus and the microtubule organizing center (MTOC) occurred within the CTL so that the two organelles face the TC. This orientation is a prerequisite for efficient TC lysis. We have shown by immunofluorescence and confocal microscopy, using a monoclonal antibody to tubulin and a rabbit autoimmune serum that binds a centriole-associated protein, that the organization of the MTOC-microtubule array is disrupted by hyperthermia. EM suggests that this disorganization of the microtubules may result from an aggregation of the pericentriolar material. The recovery of cytolytic activity is coincident with the reorganization of the microtubules about the MTOC. These findings suggest that the initial inhibitory effect of hyperthermia on CTL function results from the disruption of microtubule organization.
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Affiliation(s)
- J D Knox
- Department of Biology, University of Ottawa, Ontario, Canada
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Podolin PL, Prystowsky MB. The kinetics of vimentin RNA and protein expression in interleukin 2-stimulated T lymphocytes. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67678-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Abstract
The hypothesis that proteins known to occur in glial cells in the central nervous system may be present in inner-ear supporting cells was investigated. Immunocytochemical techniques were used to look for the existence of two classes of intermediate filaments, vimentin and glial fibrillary acidic protein (GFAP), in cellular elements of the inner-ear epithelium in normal and experimentally damaged guinea-pig cochleas. Vimentin is present in two types of supporting cells in the normal organ of Corti: Deiters' cells and inner pillar cells. Differences in intensity and distribution of vimentin immunostaining are observed across the three rows of Deiters' cells. GFAP immunoreactivity was not detected in any supporting-cell type in the organ. Cochlear hair cells were not labeled for either GFAP or vimentin. Following hair-cell destruction by exposure to noise or the administration of aminoglycosides, GFAP and vimentin are not present in phalangeal scars replacing lost hair cells.
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Affiliation(s)
- E C Oesterle
- Department of Otolaryngology, University of Washington, Seattle 98195
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Birkenbach M, Liebowitz D, Wang F, Sample J, Kieff E. Epstein-Barr virus latent infection membrane protein increases vimentin expression in human B-cell lines. J Virol 1989; 63:4079-84. [PMID: 2548016 PMCID: PMC251011 DOI: 10.1128/jvi.63.9.4079-4084.1989] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Latent Epstein-Barr virus (EBV) infection activates B-lymphocyte proliferation through mechanisms which are partially known. One approach to further delineate these mechanisms is to identify cellular genes whose expression is augmented in cells latently infected with EBV. Since EBV-negative Burkitt's lymphoma cells can be grown in continuous culture and EBV can establish growth-altering latent infection in these cells, some effects of EBV on B-lymphocyte gene expression can be studied by using this in vitro system. Pursuing this latter approach, we have used cDNA cloning and subtractive hybridization to identify a gene whose expression is increased after EBV infection. This gene encodes the cytoskeletal protein vimentin. Latent infection of established EBV-negative Burkitt's lymphoma cell lines with the transforming EBV strain, B95-8, resulted in dramatic increases in vimentin mRNA and protein levels, while infection with the nontransforming P3HR1 strain failed to do so. Vimentin induction was reproduced by the expression of the single EBV gene which encodes the latent infection membrane protein (LMP). An amino-terminal LMP deletion mutant did not induce vimentin. These results are of particular interest in light of the transforming potential of LMP, as demonstrated in rodent fibroblasts, and the interaction between vimentin and LMP observed in immunofluorescent colocalization and cell fractionation studies.
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Affiliation(s)
- M Birkenbach
- Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115
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Vikstrom KL, Borisy GG, Goldman RD. Dynamic aspects of intermediate filament networks in BHK-21 cells. Proc Natl Acad Sci U S A 1989; 86:549-53. [PMID: 2643116 PMCID: PMC286509 DOI: 10.1073/pnas.86.2.549] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A procedure was developed for the conjugation of vimentin with biotin. Biotinylated vimentin was then microinjected into BHK-21 cells and the fate of the labeled protein was determined at various times postinjection by indirect immunofluorescence. Microinjected vimentin could be traced through a specific sequence of morphological changes ultimately resulting in the formation of a filamentous network. The injected protein was first detected in spots dispersed throughout the cytoplasm. Subsequently, these spots appeared to cluster near the nucleus where they merged into a diffuse "cap." This cap coincided with a concentration of endogenous intermediate filaments and eventually gave rise to a filamentous network that was coincident with the endogenous intermediate filament network as determined by double-label immunofluorescence. The results indicate that the incorporation of exogenous vimentin into a filamentous network is initiated in a perinuclear region and progresses in a polarized fashion toward the cell surface.
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Affiliation(s)
- K L Vikstrom
- Department of Cell Biology and Anatomy, Northwestern University Medical School, Chicago, IL 60611
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Brown DL, Reuhl KR, Bormann S, Little JE. Effects of methyl mercury on the microtubule system of mouse lymphocytes. Toxicol Appl Pharmacol 1988; 94:66-75. [PMID: 3376115 DOI: 10.1016/0041-008x(88)90337-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The effects of in vivo and in vitro methyl mercury (MeHg) treatments on the microtubule system of murine splenic lymphocytes were examined by immunofluorescence microscopy. In vitro exposures to 1 to 10 microM MeHg resulted in time- and concentration-dependent microtubule disassembly. Lymphocytes isolated from mice receiving a single 10 mg/kg injection displayed microtubule damage when examined 2 and 5 days post-treatment. The capacity of in vivo and in vitro treated lymphocytes to respond to the mitogen concanavalin A (Con A) was generally inhibited by MeHg. There was a good correlation between the degree of microtubule disassembly and the inhibition of mitogen responsiveness. In vivo and in vitro treatments that resulted in extensive microtubule damage suppressed the ConA response and blocked lymphocytes early in the stimulation sequence. In vitro MeHg treatment late in mitogenesis caused a rapid, concentration-dependent inhibition of [3H]thymidine incorporation. These results suggest that damage to the microtubule system can serve as an indicator of MeHg toxicity and may underlie the toxicant's effects on lymphocyte functions.
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Affiliation(s)
- D L Brown
- Department of Biology, University of Ottawa, Ontario, Canada
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