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Kühn S, Bergqvist J, Gil M, Valenzuela C, Barrio L, Lebreton S, Zurzolo C, Enninga J. Actin Assembly around the Shigella-Containing Vacuole Promotes Successful Infection. Cell Rep 2021; 31:107638. [PMID: 32402280 PMCID: PMC7225751 DOI: 10.1016/j.celrep.2020.107638] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 03/10/2020] [Accepted: 04/21/2020] [Indexed: 12/13/2022] Open
Abstract
The enteroinvasive bacterium Shigella flexneri forces its uptake into non-phagocytic host cells through the translocation of T3SS effectors that subvert the actin cytoskeleton. Here, we report de novo actin polymerization after cellular entry around the bacterium-containing vacuole (BCV) leading to the formation of a dynamic actin cocoon. This cocoon is thicker than any described cellular actin structure and functions as a gatekeeper for the cytosolic access of the pathogen. Host CDC42, TOCA-1, N-WASP, WIP, the Arp2/3 complex, cortactin, coronin, and cofilin are recruited to the actin cocoon. They are subverted by T3SS effectors, such as IpgD, IpgB1, and IcsB. IcsB immobilizes components of the actin polymerization machinery at the BCV dependent on its fatty acyltransferase activity. This represents a unique microbial subversion strategy through localized entrapment of host actin regulators causing massive actin assembly. We propose that the cocoon promotes subsequent invasion steps for successful Shigella infection. A thick actin cocoon forms de novo around the Shigella-containing vacuole upon entry The effector IcsB entraps host actin regulators at the vacuole by lipidation Cdc42, N-WASP, and the Arp2/3 complex are major actin cocoon regulators Cocoon formation promotes subsequent Shigella niche formation and dissemination
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Affiliation(s)
- Sonja Kühn
- Institut Pasteur, Department of Cell Biology and Infection, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, 75015 Paris, France; CNRS UMR3691, 25 Rue du Dr. Roux, 75015 Paris, France
| | - John Bergqvist
- Institut Pasteur, Department of Cell Biology and Infection, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, 75015 Paris, France; CNRS UMR3691, 25 Rue du Dr. Roux, 75015 Paris, France
| | - Magdalena Gil
- Institut Pasteur, Department of Cell Biology and Infection, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, 75015 Paris, France; CNRS UMR3691, 25 Rue du Dr. Roux, 75015 Paris, France
| | - Camila Valenzuela
- Institut Pasteur, Department of Cell Biology and Infection, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, 75015 Paris, France; CNRS UMR3691, 25 Rue du Dr. Roux, 75015 Paris, France
| | - Laura Barrio
- Institut Pasteur, Department of Cell Biology and Infection, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, 75015 Paris, France; CNRS UMR3691, 25 Rue du Dr. Roux, 75015 Paris, France
| | - Stéphanie Lebreton
- Institut Pasteur, Department of Cell Biology and Infection, Membrane Trafficking and Pathogenesis Unit, 28 Rue du Dr. Roux, 75015 Paris, France
| | - Chiara Zurzolo
- Institut Pasteur, Department of Cell Biology and Infection, Membrane Trafficking and Pathogenesis Unit, 28 Rue du Dr. Roux, 75015 Paris, France
| | - Jost Enninga
- Institut Pasteur, Department of Cell Biology and Infection, Dynamics of Host-Pathogen Interactions Unit, 25 Rue du Dr. Roux, 75015 Paris, France; CNRS UMR3691, 25 Rue du Dr. Roux, 75015 Paris, France.
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2
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Zhao L, Liu SY, Li YM, Xiong ZT. Villin is a biomarker for reverse polarity in colorectal micropapillary carcinoma. Oncol Lett 2020; 21:72. [PMID: 33365083 PMCID: PMC7716710 DOI: 10.3892/ol.2020.12333] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 10/19/2020] [Indexed: 12/27/2022] Open
Abstract
Colorectal cancer (CRC) is a common malignant tumor of digestive system. CRC with micropapillary pattern (MPP) is an aggressive variant of colorectal adenocarcinoma. The aim of the present study was to clarify the clinicopathological significance and the prognostic role of an immunohistochemical marker, MPP, in CRC. The association between MPP and clinicopathological characteristics and prognosis in 286 cases of CRC (286/453 cases had follow-up information) were analysed. Then, 81 tissues without MPP and 90 tissues with MPP were analysed by immunohistochemistry using antibodies against villin, E-cadherin and epithelial membrane antigen (EMA). Bioinformatics was used to evaluate the expression of these three indicators in CRC. The proportion of micropapillary carcinoma in the overall tumour was ≥5%, and was observed in 90/453 cases (19.8%). The present data showed that CRC with MPP displayed higher rates of vascular and lymphatic invasion, a higher metastatic lymph node ratio and a higher pathological tumour and metastasis stage compared with CRC without MPP. The positive expression rates of EMA, E-cadherin and villin were 50.3, 93.4 and 96.5%, respectively. In 90 CRC cases with MPP, EMA inside-out pattern (I/OP) staining was observed in 26 cases (28.9%), and it was often focal and partial, while 37 cases (41.1%) had E-cadherin focal and partial staining compatible with reverse polarity. Villin I/OP staining was observed in 77 cases (85.6%), and circumferential staining predominated over partial staining. Overall, the data suggested that the presence of MPP is significantly associated with aggressive tumour behaviour and worse overall survival rate in CRC. Visualization and distinction of reverse polarity of colorectal micropapillary carcinomas is improved villin compared with EMA or E-cadherin.
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Affiliation(s)
- Li Zhao
- Department of Pathology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China
| | - Shao-Yan Liu
- Department of Pathology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China
| | - Yu-Meng Li
- Department of Pathology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China
| | - Zhong-Tang Xiong
- Department of Pathology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong 510150, P.R. China
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3
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Rey C, Chang YY, Latour-Lambert P, Varet H, Proux C, Legendre R, Coppée JY, Enninga J. Transcytosis subversion by M cell-to-enterocyte spread promotes Shigella flexneri and Listeria monocytogenes intracellular bacterial dissemination. PLoS Pathog 2020; 16:e1008446. [PMID: 32282860 PMCID: PMC7179946 DOI: 10.1371/journal.ppat.1008446] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 04/23/2020] [Accepted: 02/29/2020] [Indexed: 11/19/2022] Open
Abstract
Microfold (M) cell host-pathogen interaction studies would benefit from the visual analysis of dynamic cellular and microbial interplays. We adapted a human in vitro M cell model to physiological bacterial infections, expression of fluorescent localization reporters and long-term three-dimensional time-lapse microscopy. This approach allows following key steps of M cell infection dynamics at subcellular resolution, from the apical onset to basolateral epithelial dissemination. We focused on the intracellular pathogen Shigella flexneri, classically reported to transcytose through M cells to initiate bacillary dysentery in humans, while eliciting poorly protective immune responses. Our workflow was critical to reveal that S. flexneri develops a bimodal lifestyle within M cells leading to rapid transcytosis or delayed vacuolar rupture, followed by direct actin motility-based propagation to neighboring enterocytes. Moreover, we show that Listeria monocytogenes, another intracellular pathogen sharing a tropism for M cells, disseminates in a similar manner and evades M cell transcytosis completely. We established that actin-based M cell-to-enterocyte spread is the major dissemination pathway for both pathogens and avoids their exposure to basolateral compartments in our system. Our results challenge the notion that intracellular pathogens are readily transcytosed by M cells to inductive immune compartments in vivo, providing a potential mechanism for their ability to evade adaptive immunity. Microfold (M) epithelial cells are important for the onset of infections and induction of immune responses in many mucosal diseases. We extended a human in vitro M cell model to apical infections, expression of fluorescent host and microbial reporters and real-time fluorescence microscopy. Focusing on the human intracellular pathogen S. flexneri, responsible for bacillary dysentery, this workflow allowed us to uncover that the bacterium can subvert the immunological sampling function of M cells by promoting a cytosolic lifestyle and spreading directly to neighboring enterocytes. This mechanism was shared with the etiologic agent of listeriosis, the intracellular pathogen L. monocytogenes and allowed both pathogens to avoid exposure to underlying immune compartments. These results may provide a mechanism for the ability of intracellular pathogens to evade adaptive immunity in vivo, emphasizing the importance of advanced studies of M cell host-pathogen interactions to understand early steps of mucosal invasion and their consequences on immunity.
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Affiliation(s)
- Camille Rey
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, Paris, France, and Centre National de le la Recherche Scientifique (CNRS) UMR3691, Paris, France
| | - Yuen-Yan Chang
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, Paris, France, and Centre National de le la Recherche Scientifique (CNRS) UMR3691, Paris, France
| | - Patricia Latour-Lambert
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, Paris, France, and Centre National de le la Recherche Scientifique (CNRS) UMR3691, Paris, France
| | - Hugo Varet
- Institut Pasteur, Transcriptome and Epigenome Platform, Paris, France
- Institut Pasteur, Hub Bioinformatique et Biostatistique, Département de Biologie Computationnelle (USR 3756 IP CNRS), Paris, France
| | - Caroline Proux
- Institut Pasteur, Transcriptome and Epigenome Platform, Paris, France
| | - Rachel Legendre
- Institut Pasteur, Transcriptome and Epigenome Platform, Paris, France
- Institut Pasteur, Hub Bioinformatique et Biostatistique, Département de Biologie Computationnelle (USR 3756 IP CNRS), Paris, France
| | - Jean-Yves Coppée
- Institut Pasteur, Transcriptome and Epigenome Platform, Paris, France
| | - Jost Enninga
- Institut Pasteur, Dynamics of Host-Pathogen Interactions Unit, Paris, France, and Centre National de le la Recherche Scientifique (CNRS) UMR3691, Paris, France
- * E-mail:
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4
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Zhao W, Qu X, Zhuang Y, Wang L, Bosch M, Franklin-Tong VE, Xue Y, Huang S. Villin controls the formation and enlargement of punctate actin foci in pollen tubes. J Cell Sci 2020; 133:jcs237404. [PMID: 32051284 DOI: 10.1242/jcs.237404] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/01/2020] [Indexed: 11/20/2022] Open
Abstract
Self-incompatibility (SI) in the poppy Papaver rhoeas triggers dramatic alterations in actin within pollen tubes. However, how these actin alterations are mechanistically achieved remains largely unexplored. Here, we used treatment with the Ca2+ ionophore A23187 to mimic the SI-induced elevation in cytosolic Ca2+ and trigger formation of the distinctive F-actin foci. Live-cell imaging revealed that this remodeling involves F-actin fragmentation and depolymerization, accompanied by the rapid formation of punctate actin foci and subsequent increase in their size. We established that actin foci are generated and enlarged from crosslinking of fragmented actin filament structures. Moreover, we show that villins associate with actin structures and are involved in this actin reorganization process. Notably, we demonstrate that Arabidopsis VILLIN5 promotes actin depolymerization and formation of actin foci by fragmenting actin filaments, and controlling the enlargement of actin foci via bundling of actin filaments. Our study thus uncovers important novel insights about the molecular players and mechanisms involved in forming the distinctive actin foci in pollen tubes.
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Affiliation(s)
- Wanying Zhao
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xiaolu Qu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuhui Zhuang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Ludi Wang
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK
| | - Maurice Bosch
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK
| | - Vernonica E Franklin-Tong
- School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Yongbiao Xue
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
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5
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Schroer CFE, Baldauf L, van Buren L, Wassenaar TA, Melo MN, Koenderink GH, Marrink SJ. Charge-dependent interactions of monomeric and filamentous actin with lipid bilayers. Proc Natl Acad Sci U S A 2020; 117:5861-5872. [PMID: 32123101 PMCID: PMC7084070 DOI: 10.1073/pnas.1914884117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The cytoskeletal protein actin polymerizes into filaments that are essential for the mechanical stability of mammalian cells. In vitro experiments showed that direct interactions between actin filaments and lipid bilayers are possible and that the net charge of the bilayer as well as the presence of divalent ions in the buffer play an important role. In vivo, colocalization of actin filaments and divalent ions are suppressed, and cells rely on linker proteins to connect the plasma membrane to the actin network. Little is known, however, about why this is the case and what microscopic interactions are important. A deeper understanding is highly beneficial, first, to obtain understanding in the biological design of cells and, second, as a possible basis for the building of artificial cortices for the stabilization of synthetic cells. Here, we report the results of coarse-grained molecular dynamics simulations of monomeric and filamentous actin in the vicinity of differently charged lipid bilayers. We observe that charges on the lipid head groups strongly determine the ability of actin to adsorb to the bilayer. The inclusion of divalent ions leads to a reversal of the binding affinity. Our in silico results are validated experimentally by reconstitution assays with actin on lipid bilayer membranes and provide a molecular-level understanding of the actin-membrane interaction.
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Affiliation(s)
- Carsten F E Schroer
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Lucia Baldauf
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
- Living Matter Department, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Lennard van Buren
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
- Living Matter Department, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Tsjerk A Wassenaar
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Manuel N Melo
- Instituto de Tecnologia Química e Biológica, New University of Lisbon, 2780-157, Oeiras, Portugal
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands;
- Living Matter Department, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands;
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
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6
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A systematic investigation of the effect of the fluid shear stress on Caco-2 cells towards the optimization of epithelial organ-on-chip models. Biomaterials 2019; 225:119521. [DOI: 10.1016/j.biomaterials.2019.119521] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 09/20/2019] [Accepted: 09/23/2019] [Indexed: 01/01/2023]
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7
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Chandra S, Kumar M, Sharma NR, Sarkar DP. Site-specific phosphorylation of villin remodels the actin cytoskeleton to regulate Sendai viral glycoprotein-mediated membrane fusion. FEBS Lett 2019; 593:1927-1943. [PMID: 31183850 DOI: 10.1002/1873-3468.13477] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 05/26/2019] [Accepted: 05/28/2019] [Indexed: 11/10/2022]
Abstract
Connivance of cellular factors during virus-host cell membrane fusion is poorly understood. We have recently shown that cellular villin plays an important role during membrane fusion of reconstituted Sendai virosomes with hepatocytes. Here, we employed villin-null Chinese Hamster Ovary (CHO) cells, where villin expression led to an increased fusion with virosomes, which was further enhanced due to tyrosine phosphorylation in the presence of c-src. However, the villin RRI mutant, lacking actin-severing function, failed to augment membrane fusion. Furthermore, quantitative mass spectrometry and detailed analysis revealed Tyr499 to be the key phosphorylation site of villin responsible for the enhancement of virosome-CHO cell fusion. Overall, our results demonstrate a critical role for villin and its cell-type dependent phosphorylation in regulating membrane fusion.
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Affiliation(s)
- Sunandini Chandra
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
| | - Manoj Kumar
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
| | - Nishi R Sharma
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
| | - Debi P Sarkar
- Department of Biochemistry, University of Delhi South Campus, New Delhi, India
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8
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Vélez-Ortega AC, Frolenkov GI. Building and repairing the stereocilia cytoskeleton in mammalian auditory hair cells. Hear Res 2019; 376:47-57. [PMID: 30638948 DOI: 10.1016/j.heares.2018.12.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/19/2018] [Accepted: 12/28/2018] [Indexed: 10/27/2022]
Abstract
Despite all recent achievements in identification of the molecules that are essential for the structure and mechanosensory function of stereocilia bundles in the auditory hair cells of mammalian species, we still have only a rudimentary understanding of the mechanisms of stereocilia formation, maintenance, and repair. Important molecular differences distinguishing mammalian auditory hair cells from hair cells of other types and species have been recently revealed. In addition, we are beginning to solve the puzzle of the apparent life-long stability of the stereocilia bundles in these cells. New data link the stability of the cytoskeleton in the mammalian auditory stereocilia with the normal activity of mechanotransduction channels. These data suggest new ideas on how a terminally-differentiated non-regenerating hair cell in the mammalian cochlea may repair and tune its stereocilia bundle throughout the life span of the organism.
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Affiliation(s)
- A Catalina Vélez-Ortega
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
| | - Gregory I Frolenkov
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
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9
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CIB2 interacts with TMC1 and TMC2 and is essential for mechanotransduction in auditory hair cells. Nat Commun 2017; 8:43. [PMID: 28663585 PMCID: PMC5491523 DOI: 10.1038/s41467-017-00061-1] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 05/02/2017] [Indexed: 11/24/2022] Open
Abstract
Inner ear hair cells detect sound through deflection of stereocilia, the microvilli-like projections that are arranged in rows of graded heights. Calcium and integrin-binding protein 2 is essential for hearing and localizes to stereocilia, but its exact function is unknown. Here, we have characterized two mutant mouse lines, one lacking calcium and integrin-binding protein 2 and one carrying a human deafness-related Cib2 mutation, and show that both are deaf and exhibit no mechanotransduction in auditory hair cells, despite the presence of tip links that gate the mechanotransducer channels. In addition, mechanotransducing shorter row stereocilia overgrow in hair cell bundles of both Cib2 mutants. Furthermore, we report that calcium and integrin-binding protein 2 binds to the components of the hair cell mechanotransduction complex, TMC1 and TMC2, and these interactions are disrupted by deafness-causing Cib2 mutations. We conclude that calcium and integrin-binding protein 2 is required for normal operation of the mechanotransducer channels and is involved in limiting the growth of transducing stereocilia. Inner ear hair cells detect sound through deflection of stereocilia that harbor mechanically-gated channels. Here the authors show that protein responsible for Usher syndrome, CIB2, interacts with these channels and is essential for their function and hearing in mice.
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10
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Vélez-Ortega AC, Freeman MJ, Indzhykulian AA, Grossheim JM, Frolenkov GI. Mechanotransduction current is essential for stability of the transducing stereocilia in mammalian auditory hair cells. eLife 2017; 6. [PMID: 28350294 PMCID: PMC5407859 DOI: 10.7554/elife.24661] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 03/27/2017] [Indexed: 01/02/2023] Open
Abstract
Mechanotransducer channels at the tips of sensory stereocilia of inner ear hair cells are gated by the tension of 'tip links' interconnecting stereocilia. To ensure maximal sensitivity, tip links are tensioned at rest, resulting in a continuous influx of Ca2+ into the cell. Here, we show that this constitutive Ca2+ influx, usually considered as potentially deleterious for hair cells, is in fact essential for stereocilia stability. In the auditory hair cells of young postnatal mice and rats, a reduction in mechanotransducer current, via pharmacological channel blockers or disruption of tip links, leads to stereocilia shape changes and shortening. These effects occur only in stereocilia that harbor mechanotransducer channels, recover upon blocker washout or tip link regeneration and can be replicated by manipulations of extracellular Ca2+ or intracellular Ca2+ buffering. Thus, our data provide the first experimental evidence for the dynamic control of stereocilia morphology by the mechanotransduction current. DOI:http://dx.doi.org/10.7554/eLife.24661.001 Our sense of hearing depends on cells known as hair cells that line the inner ear. Each hair cell has tiny projections called stereocilia, which are arranged in a bundle with rows of increasing height like a staircase and are connected to each other by tiny filaments called tip-links. When sound waves hit the stereocilia, the tension on the tip-links increases, which opens “mechanotransduction” channels on the shorter stereocilia that allow calcium ions to flow into the cells. To ensure that the ears can detect even the softest sounds, the tip-links always have a small amount of tension which allows a small, but continuous flow of calcium ions into the cell. Scientists generally consider this continuous flow of calcium ions as a potentially harmful byproduct of sensitive hearing. Vélez-Ortega et al. isolated inner ear tissues from young mice and rats and exposed them to drugs that either block the flow of calcium ions through the mechanotransduction channels or break the tip-links on stereocilia. Surprisingly, these drugs made profound changes in the shape of individual stereocilia and the staircase architecture of the stereocilia bundle. When the drugs were rinsed out of the hair cells, the stereocilia went back to their normal shape. Sequestering of free calcium ions inside the hair cells had a similar effect on the shape of stereocilia. These findings show that the flow of calcium ions into the sterocilia via mechanotransduction channels controls the exquisite staircase-like architecture of the stereocilia bundle. More research is needed to identify which structural proteins cause the stereocilia shape changes and to work out exactly how calcium ions are involved. DOI:http://dx.doi.org/10.7554/eLife.24661.002
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Affiliation(s)
- A Catalina Vélez-Ortega
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Mary J Freeman
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Artur A Indzhykulian
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Jonathan M Grossheim
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Gregory I Frolenkov
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
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11
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Patnaik S, George SP, Pham E, Roy S, Singh K, Mariadason JM, Khurana S. By moonlighting in the nucleus, villin regulates epithelial plasticity. Mol Biol Cell 2015; 27:535-48. [PMID: 26658611 PMCID: PMC4751603 DOI: 10.1091/mbc.e15-06-0453] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 11/30/2015] [Indexed: 12/02/2022] Open
Abstract
Nuclear villin regulates the expression and activity of Slug, a key transcriptional regulator of epithelial–mesenchymal transition, by directly interacting with its transcriptional corepressor, ZBRK1. Villin accumulates in the nucleus during wound repair, and altering the cellular microenvironment by hypoxia increases the nuclear villin. Villin is a tissue-specific, actin-binding protein involved in the assembly and maintenance of microvilli in polarized epithelial cells. Conversely, villin is also linked with the loss of epithelial polarity and gain of the mesenchymal phenotype in migrating, invasive cells. In this study, we describe for the first time how villin can switch between these disparate functions to change tissue architecture by moonlighting in the nucleus. Our study reveals that the moonlighting function of villin in the nucleus may play an important role in tissue homeostasis and disease. Villin accumulates in the nucleus during wound repair, and altering the cellular microenvironment by inducing hypoxia increases the nuclear accumulation of villin. Nuclear villin is also associated with mouse models of tumorigenesis, and a systematic analysis of a large cohort of colorectal cancer specimens confirmed the nuclear distribution of villin in a subset of tumors. Our study demonstrates that nuclear villin regulates epithelial–mesenchymal transition (EMT). Altering the nuclear localization of villin affects the expression and activity of Slug, a key transcriptional regulator of EMT. In addition, we find that villin directly interacts with a transcriptional corepressor and ligand of the Slug promoter, ZBRK1. The outcome of this study underscores the role of nuclear villin and its binding partner ZBRK1 in the regulation of EMT and as potential new therapeutic targets to inhibit tumorigenesis.
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Affiliation(s)
- Srinivas Patnaik
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204
| | - Sudeep P George
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204
| | - Eric Pham
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204
| | - Swati Roy
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204
| | - Kanchan Singh
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204
| | - John M Mariadason
- Olivia Newton-John Cancer Research Institute, La Trobe University School of Cancer Medicine, Melbourne, VIC 3084, Australia
| | - Seema Khurana
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204 Baylor College of Medicine, Houston, TX 77030
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12
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Orly G, Naoz M, Gov NS. Physical model for the geometry of actin-based cellular protrusions. Biophys J 2015; 107:576-587. [PMID: 25099797 DOI: 10.1016/j.bpj.2014.05.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 05/09/2014] [Accepted: 05/28/2014] [Indexed: 11/17/2022] Open
Abstract
Actin-based cellular protrusions are a ubiquitous feature of cell morphology, e.g., filopodia and microvilli, serving a huge variety of functions. Despite this, there is still no comprehensive model for the mechanisms that determine the geometry of these protrusions. We present here a detailed computational model that addresses a combination of multiple biochemical and physical processes involved in the dynamic regulation of the shape of these protrusions. We specifically explore the role of actin polymerization in determining both the height and width of the protrusions. Furthermore, we show that our generalized model can explain multiple morphological features of these systems, and account for the effects of specific proteins and mutations.
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Affiliation(s)
- G Orly
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - M Naoz
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - N S Gov
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
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13
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Lhocine N, Arena ET, Bomme P, Ubelmann F, Prévost MC, Robine S, Sansonetti PJ. Apical invasion of intestinal epithelial cells by Salmonella typhimurium requires villin to remodel the brush border actin cytoskeleton. Cell Host Microbe 2015; 17:164-77. [PMID: 25600187 PMCID: PMC4346658 DOI: 10.1016/j.chom.2014.12.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 09/16/2014] [Accepted: 12/04/2014] [Indexed: 01/16/2023]
Abstract
Salmonella invasion of intestinal epithelial cells requires extensive, though transient, actin modifications at the site of bacterial entry. The actin-modifying protein villin is present in the brush border where it participates in the constitution of microvilli and in epithelial restitution after damage through its actin-severing activity. We investigated a possible role for villin in Salmonella invasion. The absence of villin, which is normally located at the bacterial entry site, leads to a decrease in Salmonella invasion. Villin is necessary for early membrane-associated processes and for optimal ruffle assembly by balancing the steady-state level of actin. The severing activity of villin is important for Salmonella invasion in vivo. The bacterial phosphatase SptP tightly regulates villin phosphorylation, while the actin-binding effector SipA protects F-actin and counterbalances villin-severing activity. Thus, villin plays an important role in establishing the balance between actin polymerization and actin severing to facilitate the initial steps of Salmonella entry. The host actin-binding protein villin is required for Salmonella apical invasion Villin plays a role in Salmonella ruffle formation and actin dynamics Villin-severing activity promotes Salmonella invasion in cells and in vivo The bacterial effectors SipA and SptP regulate villin activities
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Affiliation(s)
- Nouara Lhocine
- Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France; INSERM U786, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France
| | - Ellen T Arena
- Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France; INSERM U786, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France
| | - Perrine Bomme
- Plateforme de Microscopie Ultrastructurale, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France
| | - Florent Ubelmann
- Unité Mixte de Recherche 144, Institut Curie, 75248 Paris Cedex 05, France; Centro de Estudos de Doenças Crónicas (CEDOC), Faculdade de Ciencias Médicas, Universidade Nova de Lisboa, 1169-056, Portugal
| | - Marie-Christine Prévost
- Plateforme de Microscopie Ultrastructurale, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France
| | - Sylvie Robine
- Unité Mixte de Recherche 144, Institut Curie, 75248 Paris Cedex 05, France
| | - Philippe J Sansonetti
- Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France; INSERM U786, Institut Pasteur, 25 rue du Docteur Roux, 75015 Paris, France; Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France.
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14
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Enterocyte loss of polarity and gut wound healing rely upon the F-actin-severing function of villin. Proc Natl Acad Sci U S A 2013; 110:E1380-9. [PMID: 23520048 DOI: 10.1073/pnas.1218446110] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Efficient wound healing is required to maintain the integrity of the intestinal epithelial barrier because of its constant exposure to a large variety of environmental stresses. This process implies a partial cell depolarization and the acquisition of a motile phenotype that involves rearrangements of the actin cytoskeleton. Here we address how polarized enterocytes harboring actin-rich apical microvilli undergo extensive cell remodeling to drive injury repair. Using live imaging technologies, we demonstrate that enterocytes in vitro and in vivo rapidly depolarize their microvilli at the wound edge. Through its F-actin-severing activity, the microvillar actin-binding protein villin drives both apical microvilli disassembly in vitro and in vivo and promotes lamellipodial extension. Photoactivation experiments indicate that microvillar actin is mobilized at the lamellipodium, allowing optimal migration. Finally, efficient repair of colonic mechanical injuries requires villin severing of F-actin, emphasizing the importance of villin function in intestinal homeostasis. Thus, villin severs F-actin to ensure microvillus depolarization and enterocyte remodeling upon injury. This work highlights the importance of specialized apical pole disassembly for the repolarization of epithelial cells initiating migration.
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15
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George SP, Chen H, Conrad JC, Khurana S. Regulation of directional cell migration by membrane-induced actin bundling. J Cell Sci 2012; 126:312-26. [PMID: 23132923 DOI: 10.1242/jcs.116244] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
During embryonic development and in metastatic cancers, cells detach from the epithelium and migrate with persistent directionality. Directional cell migration is also crucial for the regeneration and maintenance of the epithelium and impaired directional migration is linked to chronic inflammatory diseases. Despite its significance, the mechanisms controlling epithelial cell migration remain poorly understood. Villin is an epithelial-cell-specific actin modifying protein that regulates epithelial cell plasticity and motility. In motile cells villin is associated with the highly branched and the unbranched actin filaments of lamellipodia and filopodia, respectively. In this study we demonstrate for the first time that villin regulates directionally persistent epithelial cell migration. Functional characterization of wild-type and mutant villin proteins revealed that the ability of villin to self-associate and bundle actin as well as its direct interaction with phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] regulates villin-induced filopodial assembly and directional cell migration. Our findings suggest that convergence of different signaling cascades could spatially restrict villin activity to areas of high PtdIns(4,5)P(2) and F-actin concentration to assemble filopodia. Furthermore, our data reveal the ability of villin to undergo actin- and PtdIns(4,5)P(2)-induced self-association, which may be particularly suited to coalesce and reorganize actin bundles within the filopodia.
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Affiliation(s)
- Sudeep P George
- Department of Biology and Biochemistry, The University of Houston, Houston, TX 77204, USA
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16
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Haglund CM, Welch MD. Pathogens and polymers: microbe-host interactions illuminate the cytoskeleton. ACTA ACUST UNITED AC 2011; 195:7-17. [PMID: 21969466 PMCID: PMC3187711 DOI: 10.1083/jcb.201103148] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Intracellular pathogens subvert the host cell cytoskeleton to promote their own survival, replication, and dissemination. Study of these microbes has led to many discoveries about host cell biology, including the identification of cytoskeletal proteins, regulatory pathways, and mechanisms of cytoskeletal function. Actin is a common target of bacterial pathogens, but recent work also highlights the use of microtubules, cytoskeletal motors, intermediate filaments, and septins. The study of pathogen interactions with the cytoskeleton has illuminated key cellular processes such as phagocytosis, macropinocytosis, membrane trafficking, motility, autophagy, and signal transduction.
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Affiliation(s)
- Cat M Haglund
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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17
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Khurana S, George SP. The role of actin bundling proteins in the assembly of filopodia in epithelial cells. Cell Adh Migr 2011; 5:409-20. [PMID: 21975550 PMCID: PMC3218608 DOI: 10.4161/cam.5.5.17644] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 08/05/2011] [Indexed: 01/22/2023] Open
Abstract
The goal of this review is to highlight how emerging new models of filopodia assembly, which include tissue specific actin-bundling proteins, could provide more comprehensive representations of filopodia assembly that would describe more adequately and effectively the complexity and plasticity of epithelial cells. This review also describes how the true diversity of actin bundling proteins must be considered to predict the far-reaching significance and versatile functions of filopodia in epithelial cells.
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Affiliation(s)
- Seema Khurana
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA.
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18
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Zhang H, Qu X, Bao C, Khurana P, Wang Q, Xie Y, Zheng Y, Chen N, Blanchoin L, Staiger CJ, Huang S. Arabidopsis VILLIN5, an actin filament bundling and severing protein, is necessary for normal pollen tube growth. THE PLANT CELL 2010; 22:2749-67. [PMID: 20807879 PMCID: PMC2947167 DOI: 10.1105/tpc.110.076257] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A dynamic actin cytoskeleton is essential for pollen germination and tube growth. However, the molecular mechanisms underlying the organization and turnover of the actin cytoskeleton in pollen remain poorly understood. Villin plays a key role in the formation of higher-order structures from actin filaments and in the regulation of actin dynamics in eukaryotic cells. It belongs to the villin/gelsolin/fragmin superfamily of actin binding proteins and is composed of six gelsolin-homology domains at its core and a villin headpiece domain at its C terminus. Recently, several villin family members from plants have been shown to sever, cap, and bundle actin filaments in vitro. Here, we characterized a villin isovariant, Arabidopsis thaliana VILLIN5 (VLN5), that is highly and preferentially expressed in pollen. VLN5 loss-of-function retarded pollen tube growth and sensitized actin filaments in pollen grains and tubes to latrunculin B. In vitro biochemical analyses revealed that VLN5 is a typical member of the villin family and retains a full suite of activities, including barbed-end capping, filament bundling, and calcium-dependent severing. The severing activity was confirmed with time-lapse evanescent wave microscopy of individual actin filaments in vitro. We propose that VLN5 is a major regulator of actin filament stability and turnover that functions in concert with oscillatory calcium gradients in pollen and therefore plays an integral role in pollen germination and tube growth.
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Affiliation(s)
- Hua Zhang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaolu Qu
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chanchan Bao
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Parul Khurana
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Qiannan Wang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yurong Xie
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yiyan Zheng
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Naizhi Chen
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l’Energie Atomique/Centre National de la Recherche Scientifique/Université Joseph Fourier, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Address correspondence to
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19
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Calcium-actin waves and oscillations of cellular membranes. Biophys J 2009; 97:1558-68. [PMID: 19751660 DOI: 10.1016/j.bpj.2009.07.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Revised: 06/18/2009] [Accepted: 07/01/2009] [Indexed: 01/16/2023] Open
Abstract
We propose a mechanism for the formation of membrane oscillations and traveling waves, which arise due to the coupling between the actin cytoskeleton and the calcium flux through the membrane. In our model, the fluid cell membrane has a mobile but constant population of proteins with a convex spontaneous curvature, which act as nucleators of actin polymerization and adhesion. Such a continuum model couples the forces of cell-substrate adhesion, actin polymerization, membrane curvature, and the flux of calcium through the membrane. Linear stability analysis shows that sufficiently strong coupling among the calcium, membrane, and protein dynamics may induce robust traveling waves on the membrane. This result was checked for a reduced feedback scheme and is compared to the results without the effects of calcium, where permanent phase separation without waves or oscillations is obtained. The model results are compared to the published observations of calcium waves in cell membranes, and a number of testable predictions are proposed.
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Khurana S, George SP. Regulation of cell structure and function by actin-binding proteins: villin's perspective. FEBS Lett 2008; 582:2128-39. [PMID: 18307996 PMCID: PMC2680319 DOI: 10.1016/j.febslet.2008.02.040] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Accepted: 02/19/2008] [Indexed: 12/23/2022]
Abstract
Villin is a tissue-specific actin modifying protein that is associated with actin filaments in the microvilli and terminal web of epithelial cells. It belongs to a large family of actin-binding proteins which includes actin-capping, -nucleating and/or -severing proteins such as gelsolin, severin, fragmin, adseverin/scinderin and actin crosslinking proteins such as dematin and supervillin. Studies done in epithelial cell lines and villin knock-out mice have demonstrated the function of villin in regulating actin dynamics, cell morphology, epithelial-to-mesenchymal transition, cell migration and cell survival. In addition, the ligand-binding properties of villin (F-actin, G-actin, calcium, phospholipids and phospholipase C-gamma1) are mechanistically important for the crosstalk between signaling pathways and actin reorganization in epithelial cells.
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Affiliation(s)
- Seema Khurana
- Department of Physiology, University of Tennessee Health Science Center, 894 Union Avenue, Nash 402, Memphis, TN 38163, United States.
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Ki MR, Lee HR, Goo MJ, Hong IH, Do SH, Jeong DH, Yang HJ, Yuan DW, Park JK, Jeong KS. Differential regulation of ERK1/2 and p38 MAP kinases in VacA-induced apoptosis of gastric epithelial cells. Am J Physiol Gastrointest Liver Physiol 2008; 294:G635-47. [PMID: 18096609 DOI: 10.1152/ajpgi.00281.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Helicobacter pylori vacuolating cytotoxin A (VacA) has been considered as an apoptosis-inducing factor. Here, we investigated the mechanism of VacA-induced apoptosis in relation to the defense mechanism and MAP kinases pathway in gastric epithelial cells. AGS cells exposed to enriched VacA extracts affected the level of SOD-1 and villin. We further investigated the role of VacA in those inductions using a functional recombinant VacA (rVacA). Activation of p38 MAPK and Bax dimerization by rVacA were increased in a dose-dependent manner. rVacA-induced ERK1/2 MAPK activation was maximal at 30 min and 4 h and 1-4 microg/ml of rVacA. rVacA-induced SOD-1 expression was considerably diminished by inhibiting ERK1/2 MAPK and it was slightly increased by inhibiting p38 MAPK. rVacA increased or decreased villin expression depending on dose and exposure time and its expression was mainly appeared in the contractile actin ring of the dividing cells. Despite its cytoprotective effect, SB-203580, a p38 inhibitor, was unlikely to reduce VacA-induced Bax dimerization and rather inhibited villin and Bcl2 expression, indicating that p38 may also play a role in cell proliferation or differentiation for survival after VacA intoxication. Furthermore, p38 inhibitor accelerated rVacA-induced cell death after exposure of AGS cells to H(2)O(2) but ERK1/2 inhibitor protected cells from H(2)O(2) insult. These results suggest that SOD-1 and villin are expressed differentially upon VacA insult depending on dose and exposure time via ERK and p38 MAP kinases; decrease in SOD-1 and villin expression coupled with Bax dimerization leads to apoptosis of gastric epithelial cells.
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Affiliation(s)
- Mi-Ran Ki
- Department of Pathology, College of Veterinary Medicine, Kyungpook National University, Buk-ku, Daegu City, Republic of Korea
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Cooper JA, Sept D. New insights into mechanism and regulation of actin capping protein. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 267:183-206. [PMID: 18544499 DOI: 10.1016/s1937-6448(08)00604-7] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The heterodimeric actin capping protein, referred to here as "CP," is an essential element of the actin cytoskeleton, binding to the barbed ends of actin filaments and regulating their polymerization. In vitro, CP has a critical role in the dendritic nucleation process of actin assembly mediated by Arp2/3 complex, and in vivo, CP is important for actin assembly and actin-based process of morphogenesis and differentiation. Recent studies have provided new insight into the mechanism of CP binding the barbed end, which raises new possibilities for the dynamics of CP and actin in cells. In addition, a number of molecules that bind and regulate CP have been discovered, suggesting new ideas for how CP may integrate into diverse processes of cell physiology.
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Affiliation(s)
- John A Cooper
- Department of Cell Biology, Washington University, St. Louis, MO 63110, USA
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