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Yang MH, Zhao MY, Wang Z, Kang R, He YL, Yin XC, Liu LY, Yang LC, Zhan CX, Wu XS, Tang DL, Cao LZ. WAVE1 regulates P-glycoprotein expression via Ezrin in leukemia cells. Leuk Lymphoma 2011; 52:298-309. [PMID: 21281239 DOI: 10.3109/10428194.2010.538776] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
For children with acute myeloblastic leukemia (AML), multidrug resistance (MDR) reduces treatment effectiveness, and often leads to poor patient survival. While a number of factors have been described that affect MDR, the mechanisms underlying this effect remain unclear. In this study, the role of WAVE1 in MDR was investigated. Among 62 children with AML, high levels of WAVE1 were associated with poor patient outcomes. Proteomic techniques were used to identify novel WAVE1-interacting proteins from leukemia cells, one of which was the cytoskeleton regulator Ezrin. In leukemia cells, WAVE1 co-localized with both Ezrin and P-glycoprotein (P-gp), a critical regulator of the MDR phenotype. Overexpression of WAVE1 in K562 leukemia cells up-regulated P-gp and Ezrin, and reduced K562 cells' sensitivity to the chemotherapy drug adriamycin. The opposite effect was seen when WAVE1 expression was reduced via RNA interference. Critically, overexpression of WAVE1 in the absence of Ezrin did not affect P-gp levels or MDR. These data suggest that WAVE1 affects P-gp and MDR of leukemia cells through Ezrin.
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Affiliation(s)
- Ming-Hua Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, Hunan Province, People's Republic of China
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52
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Huber F, Käs J. Self-regulative organization of the cytoskeleton. Cytoskeleton (Hoboken) 2011; 68:259-65. [DOI: 10.1002/cm.20509] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 02/21/2011] [Accepted: 03/03/2011] [Indexed: 01/09/2023]
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53
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An actin cytoskeleton with evolutionarily conserved functions in the absence of canonical actin-binding proteins. Proc Natl Acad Sci U S A 2011; 108:6151-6. [PMID: 21444821 DOI: 10.1073/pnas.1018593108] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Giardia intestinalis, a human intestinal parasite and member of what is perhaps the earliest-diverging eukaryotic lineage, contains the most divergent eukaryotic actin identified to date and is the first eukaryote known to lack all canonical actin-binding proteins (ABPs). We sought to investigate the properties and functions of the actin cytoskeleton in Giardia to determine whether Giardia actin (giActin) has reduced or conserved roles in core cellular processes. In vitro polymerization of giActin produced filaments, indicating that this divergent actin is a true filament-forming actin. We generated an anti-giActin antibody to localize giActin throughout the cell cycle. GiActin localized to the cortex, nuclei, internal axonemes, and formed C-shaped filaments along the anterior of the cell and a flagella-bundling helix. These structures were regulated with the cell cycle and in encysting cells giActin was recruited to the Golgi-like cyst wall processing vesicles. Knockdown of giActin demonstrated that giActin functions in cell morphogenesis, membrane trafficking, and cytokinesis. Additionally, Giardia contains a single G protein, giRac, which affects the Giardia actin cytoskeleton independently of known target ABPs. These results imply that there exist ancestral and perhaps conserved roles for actin in core cellular processes that are independent of canonical ABPs. Of medical significance, the divergent giActin cytoskeleton is essential and commonly used actin-disrupting drugs do not depolymerize giActin structures. Therefore, the giActin cytoskeleton is a promising drug target for treating giardiasis, as we predict drugs that interfere with the Giardia actin cytoskeleton will not affect the mammalian host.
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Leong SY, Faux CH, Turbic A, Dixon KJ, Turnley AM. The Rho Kinase Pathway Regulates Mouse Adult Neural Precursor Cell Migration. Stem Cells 2011; 29:332-43. [DOI: 10.1002/stem.577] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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55
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Germane KL, Spiller BW. Structural and functional studies indicate that the EPEC effector, EspG, directly binds p21-activated kinase. Biochemistry 2011; 50:917-9. [PMID: 21235237 DOI: 10.1021/bi1020138] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bacterial pathogens secrete effectors into their hosts that subvert host defenses and redirect host processes. EspG is a type three secretion effector with a disputed function that is found in enteropathogenic Escherichia coli. Here we show that EspG is structurally similar to VirA, a Shigella virulence factor; EspG has a large, conserved pocket on its surface; EspG binds directly to the amino-terminal inhibitory domain of human p21-activated kinase (PAK); and mutations to conserved residues in the surface pocket disrupt the interaction with PAK.
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Affiliation(s)
- Katherine L Germane
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
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56
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Yun SP, Ryu JM, Jang MW, Han HJ. Interaction of profilin-1 and F-actin via a β-arrestin-1/JNK signaling pathway involved in prostaglandin E(2)-induced human mesenchymal stem cells migration and proliferation. J Cell Physiol 2011; 226:559-71. [PMID: 20717968 DOI: 10.1002/jcp.22366] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Although many previous reports have examined the function of prostaglandin E(2) (PGE(2)) in the migration and proliferation of various cell types, the role of the actin cytoskeleton in human mesenchymal stem cells (hMSCs) migration and proliferation has not been reported. The present study examined the involvement of profilin-1 (Pfn-1) and filamentous-actin (F-actin) in PGE(2)-induced hMSC migration and proliferation and its related signal pathways. PGE(2) (10(-6) M) increased both cell migration and proliferation, and also increased E-type prostaglandin receptor 2 (EP2) mRNA expression, β-arrestin-1 phosphorylation, and c-Jun N-terminal kinase (JNK) phosphorylation. Small interfering RNA (siRNA)-mediated knockdown of β-arrestin-1 and JNK (-1, -2, -3) inhibited PGE(2)-induced growth of hMSCs. PGE(2) also activated Pfn-1, which was blocked by JNK siRNA, and induced F-actin level and organization. Downregulation of Pfn-1 by siRNA decreased the level and organization of F-actin. In addition, specific siRNA for TRIO and F-actin-binding protein (TRIOBP) reduced the PGE(2)-induced increase in hMSC migration and proliferation. Together, these experimental data demonstrate that PGE(2) partially stimulates hMSCs migration and proliferation by interaction of Pfn-1 and F-actin via EP2 receptor-dependent β-arrestin-1/JNK signaling pathways.
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Affiliation(s)
- Seung Pil Yun
- Department of Veterinary Physiology, College of Veterinary Medicine, Biotherapy Human Resources Center (BK21), Chonnam National University, Gwangju, Korea
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57
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Carter GC, Bernstone L, Baskaran D, James W. HIV-1 infects macrophages by exploiting an endocytic route dependent on dynamin, Rac1 and Pak1. Virology 2011; 409:234-50. [DOI: 10.1016/j.virol.2010.10.018] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 10/04/2010] [Accepted: 10/13/2010] [Indexed: 01/12/2023]
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Allen RJ, Elston TC. From Physics to Pharmacology? REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2011; 74:016601. [PMID: 25484456 PMCID: PMC4256083 DOI: 10.1088/0034-4885/74/1/016601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Over the last fifty years there has been an explosion of biological data, leading to the realization that to fully explain biological mechanisms it is necessary to interpret them as complex dynamical systems. The first stage of this interpretation is to determine which components (proteins, genes or metabolites) of the system interact. This is usually represented by a graph, or network. The behavior of this network can then be investigated using mathematical modeling. In vivo these biological networks show several remarkable (and seemingly paradoxical) properties including robustness, plasticity and sensitivity. Erroneous behavior of these networks is often associated with disease. Hence understanding the system-level properties can have important implications for the treatment of disease. Systems biology is an organized approach to quantitatively describe and elucidate the behavior of these complex networks. This review focuses on the progress and future challenges of a systems approach to biology.
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Affiliation(s)
- Richard J Allen
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Timothy C Elston
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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59
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Wuertz CM, Lorincz A, Vettel C, Thomas MA, Wieland T, Lutz S. p63RhoGEF—a key mediator of angiotensin II‐dependent signaling and processes in vascular smooth muscle cells. FASEB J 2010. [DOI: 10.1096/fj.10.155499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Christina M. Wuertz
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Akos Lorincz
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Christiane Vettel
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Martin A. Thomas
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Thomas Wieland
- Institute of Experimental and Clinical Pharmacology and Toxicology Heidelberg Germany
| | - Susanne Lutz
- Medical Faculty MannheimUniversity of Heidelberg Heidelberg Germany
- Department of PharmacologyMedical Faculty Goettingen, University of Goettingen Goettingen Germany
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60
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Cochaud S, Chevrier L, Meunier AC, Brillet T, Chadéneau C, Muller JM. The vasoactive intestinal peptide-receptor system is involved in human glioblastoma cell migration. Neuropeptides 2010; 44:373-83. [PMID: 20638719 DOI: 10.1016/j.npep.2010.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 05/14/2010] [Accepted: 06/12/2010] [Indexed: 12/31/2022]
Abstract
Glioblastoma multiforme (GBM) is the most aggressive form of brain tumor in adults. This cancer has an infiltrative nature and the median survival of patients is about one year. Vasoactive intestinal peptide (VIP) belongs to a structurally related family of polypeptides and is a major regulatory factor in the central and peripheral nervous systems. VIP regulates proliferation of astrocytes and of numerous cancer cell lines and modulates migration in prostatic and colonic cancer cell lines. Little is known about the involvement of VIP and its receptors (VIP-receptor system) in proliferation or migration of GBM cells. The effects of VIP, PACAP and of synthetic VIP antagonists were tested in two human GBM cell lines, M059K and M059J, established from two different parts of a single tumor. In these cells, the data revealed that the VIP-receptor system did not affect proliferation but controlled cell migration. Indeed, in M059K cells which express components of the VIP receptor system, the VIP receptor antagonists and a PACAP antibody enhanced migration. The VIP receptor antagonists increased generation of typical migration-associated processes: filopodia and lamellipodia, and activation of Rac1 and Cdc42 GTPases. Reciprocally, in M059J cells which poorly express the VIP-receptor system, treatments with the agonists VIP and PACAP resulted in decreased cell migration. Furthermore, the peptides appeared to act through a subclass of binding sites displaying an uncommon very high affinity for these ligands. Taken together, these observations suggest that components of the VIP-receptor system negatively regulate cell migration, thus showing potential anti-oncogenic properties.
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Affiliation(s)
- Stéphanie Cochaud
- Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, CNRS, 40 Avenue du Recteur Pineau, Poitiers F-86022, France
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61
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WASH, WHAMM and JMY: regulation of Arp2/3 complex and beyond. Trends Cell Biol 2010; 20:650-61. [PMID: 20888769 DOI: 10.1016/j.tcb.2010.08.014] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 08/16/2010] [Accepted: 08/30/2010] [Indexed: 02/07/2023]
Abstract
Arp2/3 complex mediates the nucleation of actin filaments in multiple subcellular processes, and is activated by nucleation-promoting factors (NPFs) from the Wiskott-Aldrich Syndrome family. In exciting new developments, this family has grown by three members: WASH, WHAMM and JMY, which extend the repertoire of dynamic membrane structures that are remodeled following Arp2/3 activation in vivo. These novel NPFs share an actin- and Arp2/3-interacting WCA module, and combine Arp2/3 activation with additional biochemical functions, including capping protein inhibition, microtubule engagement or Arp2/3-independent actin nucleation, none of which had been previously associated with canonical WCA-harboring proteins. Uncovering the physiological relevance of these unique activities will require concerted efforts from multiple disciplines, and is sure to impact our understanding of how the cytoskeleton controls so many dynamic subcellular events.
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62
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Burrows C, Abd Latip N, Lam SJ, Carpenter L, Sawicka K, Tzolovsky G, Gabra H, Bushell M, Glover DM, Willis AE, Blagden SP. The RNA binding protein Larp1 regulates cell division, apoptosis and cell migration. Nucleic Acids Res 2010; 38:5542-53. [PMID: 20430826 PMCID: PMC2938220 DOI: 10.1093/nar/gkq294] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 04/01/2010] [Accepted: 04/07/2010] [Indexed: 01/11/2023] Open
Abstract
The RNA binding protein Larp1 was originally shown to be involved in spermatogenesis, embryogenesis and cell-cycle progression in Drosophila. Our data show that mammalian Larp1 is found in a complex with poly A binding protein and eukaryote initiation factor 4E and is associated with 60S and 80S ribosomal subunits. A reduction in Larp1 expression by siRNA inhibits global protein synthesis rates and results in mitotic arrest and delayed cell migration. Consistent with these data we show that Larp1 protein is present at the leading edge of migrating cells and interacts directly with cytoskeletal components. Taken together, these data suggest a role for Larp1 in facilitating the synthesis of proteins required for cellular remodelling and migration.
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Affiliation(s)
- Carla Burrows
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Normala Abd Latip
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Sarah-Jane Lam
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Lee Carpenter
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Kirsty Sawicka
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - George Tzolovsky
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Hani Gabra
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Martin Bushell
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - David M. Glover
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Anne E. Willis
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
| | - Sarah P. Blagden
- Department of Molecular Oncology, Imperial College, Hammersmith Campus, Du Cane Road, London W12 0HS, NHS Blood and Transplant, John Radcliffe Hospital, Oxford, OX3 9BQ, School of Pharmacy, Nottingham University, Nottingham UK NG7 2RD and Department of Genetics, Downing Site, Cambridge CB2 3EH, UK
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Wuertz CM, Lorincz A, Vettel C, Thomas MA, Wieland T, Lutz S. p63RhoGEF--a key mediator of angiotensin II-dependent signaling and processes in vascular smooth muscle cells. FASEB J 2010; 24:4865-76. [PMID: 20739613 DOI: 10.1096/fj.10-155499] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of our study was to investigate the role of endogenous p63RhoGEF in G(q/11)-dependent RhoA activation and signaling in rat aortic smooth muscle cells (RASMCs). Therefore, we studied the expression and subcellular localization in freshly isolated RASMCs and performed loss of function experiments to analyze its contribution to RhoGTPase activation and functional responses such as proliferation and contraction. By this, we could show that p63RhoGEF is endogenously expressed in RASMCs and acts there as the dominant mediator of the fast angiotensin II (ANG II)-dependent but not of the sphingosine-1-phosphate (S(1)P)-dependent RhoA activation. p63RhoGEF is not an activator of the concomitant Rac1 activation and functions independently of caveolae. The knockdown of endogenous p63RhoGEF significantly reduced the mitogenic response of ANG II, abolished ANG II-induced stress fiber formation and cell elongation in 2-D culture, and impaired the ANG II-driven contraction in a collagen-based 3-D model. In conclusion, our data provide for the first time evidence that p63RhoGEF is an important mediator of ANG II-dependent RhoA activation in RASMCs and therewith a leading actor in the subsequently triggered cellular processes, such as proliferation and contraction.
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Affiliation(s)
- Christina M Wuertz
- Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
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64
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Keeping in touch with contact inhibition of locomotion. Trends Cell Biol 2010; 20:319-28. [PMID: 20399659 PMCID: PMC2927909 DOI: 10.1016/j.tcb.2010.03.005] [Citation(s) in RCA: 207] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 03/24/2010] [Accepted: 03/24/2010] [Indexed: 01/01/2023]
Abstract
Contact inhibition of locomotion (CIL) is the process by which cells in vitro change their direction of migration upon contact with another cell. Here, we revisit the concept that CIL plays a central role in the migration of single cells and in collective migration, during both health and disease. Importantly, malignant cells exhibit a diminished CIL behaviour which allows them to invade healthy tissues. Accumulating evidence indicates that CIL occurs in vivo and that regulation of small Rho GTPases is important in the collapse of cell protrusions upon cell contact, the first step of CIL. Finally, we propose possible cell surface proteins that could be involved in the initial contact that regulates Rho GTPases during CIL.
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65
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König K, Diehl L, Rommerscheidt-Fuss U, Golletz C, Quast T, Kahl P, Kolanus W, Knolle P, Buettner R, Heukamp LC. Four-and-a-Half LIM Domain Protein 2 Is a Novel Regulator of Sphingosine 1-Phosphate Receptor 1 in CCL19-Induced Dendritic Cell Migration. THE JOURNAL OF IMMUNOLOGY 2010; 185:1466-75. [DOI: 10.4049/jimmunol.0903449] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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66
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Klink BU, Barden S, Heidler TV, Borchers C, Ladwein M, Stradal TEB, Rottner K, Heinz DW. Structure of Shigella IpgB2 in complex with human RhoA: implications for the mechanism of bacterial guanine nucleotide exchange factor mimicry. J Biol Chem 2010; 285:17197-208. [PMID: 20363740 PMCID: PMC2878080 DOI: 10.1074/jbc.m110.107953] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 03/11/2010] [Indexed: 11/06/2022] Open
Abstract
A common theme in bacterial pathogenesis is the manipulation of eukaryotic cells by targeting the cytoskeleton. This is in most cases achieved either by modifying actin, or indirectly via activation of key regulators controlling actin dynamics such as Rho-GTPases. A novel group of bacterial virulence factors termed the WXXXE family has emerged as guanine nucleotide exchange factors (GEFs) for these GTPases. The precise mechanism of nucleotide exchange, however, has remained unclear. Here we report the structure of the WXXXE-protein IpgB2 from Shigella flexneri and its complex with human RhoA. We unambiguously identify IpgB2 as a bacterial RhoA-GEF and dissect the molecular mechanism of GDP release, an essential prerequisite for GTP binding. Our observations uncover that IpgB2 induces conformational changes on RhoA mimicking DbI- but not DOCK family GEFs. We also show that dissociation of the GDP.Mg(2+) complex is preceded by the displacement of the metal ion to the alpha-phosphate of the nucleotide, diminishing its affinity to the GTPase. These data refine our understanding of the mode of action not only of WXXXE GEFs but also of mammalian GEFs of the DH/PH family.
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Affiliation(s)
| | | | | | - Christina Borchers
- Signaling and Motility Group, Helmholtz Zentrum für Infektionsforschung, D-38124 Braunschweig and
| | | | - Theresia E. B. Stradal
- Signaling and Motility Group, Helmholtz Zentrum für Infektionsforschung, D-38124 Braunschweig and
- the Institute of General Zoology and Genetics, University of Münster, D-48149 Münster, Germany
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67
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Mercer J, Knébel S, Schmidt FI, Crouse J, Burkard C, Helenius A. Vaccinia virus strains use distinct forms of macropinocytosis for host-cell entry. Proc Natl Acad Sci U S A 2010; 107:9346-51. [PMID: 20439710 PMCID: PMC2889119 DOI: 10.1073/pnas.1004618107] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To enter host cells, vaccinia virus, a prototype poxvirus, can induce transient macropinocytosis followed by endocytic internalization and penetration through the limiting membrane of pinosomes by membrane fusion. Although mature virions (MVs) of the Western reserve (WR) strain do this in HeLa cells by activating transient plasma membrane blebbing, MVs from the International Health Department-J strain were found to induce rapid formation (and lengthening) of filopodia. When the signaling pathways underlying these responses were compared, differences were observed at the level of Rho GTPases. Key to the filopodial formation was the virus-induced activation of Cdc42, and for the blebbing response the activation of Rac1. In addition, unlike WR, International Health Department-J MVs did not rely on genistein-sensitive tyrosine kinase and PI(3)K activities. Only WR MVs had membrane fusion activity at low pH. Inhibitor profiling showed that MVs from both strains entered cells by macropinocytosis and that this was induced by virion-exposed phosphatidylserine. Both MVs relied on the activation of epidermal growth factor receptor, on serine/threonine kinases, protein kinase C, and p21-activated kinase 1. The results showed that different strains of the same virus can elicit dramatically different responses in host cells during entry, and that different macropinocytic mechanisms are possible in the same cell line through subtle differences in the activating ligand.
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Affiliation(s)
- Jason Mercer
- Eidgenössische Technische Hochschule Zurich, Institute of Biochemistry, Eidgenössische Technische Hochschule Hoenggerberg, 8093 Zurich, Switzerland
| | - Stephan Knébel
- Eidgenössische Technische Hochschule Zurich, Institute of Biochemistry, Eidgenössische Technische Hochschule Hoenggerberg, 8093 Zurich, Switzerland
| | - Florian I. Schmidt
- Eidgenössische Technische Hochschule Zurich, Institute of Biochemistry, Eidgenössische Technische Hochschule Hoenggerberg, 8093 Zurich, Switzerland
| | - Josh Crouse
- Eidgenössische Technische Hochschule Zurich, Institute of Biochemistry, Eidgenössische Technische Hochschule Hoenggerberg, 8093 Zurich, Switzerland
| | - Christine Burkard
- Eidgenössische Technische Hochschule Zurich, Institute of Biochemistry, Eidgenössische Technische Hochschule Hoenggerberg, 8093 Zurich, Switzerland
| | - Ari Helenius
- Eidgenössische Technische Hochschule Zurich, Institute of Biochemistry, Eidgenössische Technische Hochschule Hoenggerberg, 8093 Zurich, Switzerland
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68
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Zhu J, Attias O, Aoudjit L, Jiang R, Kawachi H, Takano T. p21-Activated kinases regulate actin remodeling in glomerular podocytes. Am J Physiol Renal Physiol 2010; 298:F951-61. [DOI: 10.1152/ajprenal.00536.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The tyrosine phosphorylation of nephrin is reported to regulate podocyte morphology via the Nck adaptor proteins. The Pak family of kinases are regulators of the actin cytoskeleton and are recruited to the plasma membrane via Nck. Here, we investigated the role of Pak in podocyte morphology. Pak1/2 were expressed in cultured podocytes. In mouse podocytes, Pak2 was predominantly phosphorylated, concentrated at the tips of the cellular processes, and its expression and/or phosphorylation were further increased when differentiated. Overexpression of rat nephrin in podocytes increased Pak1/2 phosphorylation, which was abolished when the Nck binding sites were mutated. Furthermore, dominant-negative Nck constructs blocked the Pak1 phosphorylation induced by antibody-mediated cross linking of nephrin. Transient transfection of constitutively kinase-active Pak1 into differentiated mouse podocytes decreased stress fibers, increased cortical F-actin, and extended the cellular processes, whereas kinase-dead mutant, kinase inhibitory construct, and Pak2 knockdown by shRNA had the opposite effect. In a rat model of puromycin aminonucleoside nephrosis, Pak1/2 phosphorylation was decreased in glomeruli, concomitantly with a decrease of nephrin tyrosine phosphorylation. These results suggest that Pak contributes to remodeling of the actin cytoskeleton in podocytes. Disturbed nephrin-Nck-Pak interaction may contribute to abnormal morphology of podocytes and proteinuria.
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Affiliation(s)
- Jianxin Zhu
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; and
| | - Ortal Attias
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; and
| | - Lamine Aoudjit
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; and
| | - Ruihua Jiang
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; and
| | - Hiroshi Kawachi
- Department of Cell Biology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Tomoko Takano
- Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; and
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69
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Georgiou M, Baum B. Polarity proteins and Rho GTPases cooperate to spatially organise epithelial actin-based protrusions. J Cell Sci 2010; 123:1089-98. [PMID: 20197404 DOI: 10.1242/jcs.060772] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Different actin-filament-based structures co-exist in many cells. Here, we characterise dynamic actin-based protrusions that form at distinct positions within columnar epithelial cells, focusing on basal filopodia and sheet-like intermediate-level protrusions that extend between surrounding epithelial cells. Using a genetic analysis, we found that the form and distribution of these actin-filament-based structures depends on the activities of apical polarity determinants, not on basal integrin signalling. Bazooka/Par3 acts upstream of the RacGEF Sif/TIAM1 to limit filopodia to the basal domain, whereas Cdc42, aPKC and Par6 are required for normal protrusion morphology and dynamics. Downstream of these polarity regulators, Sif/TIAM1, Rac, SCAR and Arp2/3 complexes catalyse actin nucleation to generate lamellipodia and filopodia, whose form depends on the level of Rac activation. Taken together, these data reveal a role for Baz/Par3 in the establishment of an intercellular gradient of Rac inhibition, from apical to basal, and an intimate association between different apically concentrated Par proteins and Rho-family GTPases in the regulation of the distribution and structure of the polarised epithelial actin cytoskeleton.
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Affiliation(s)
- Marios Georgiou
- MRC-Laboratory of Molecular Cell Biology, UCL, London, WC1E 6BT, UK.
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70
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Gisselsson L, Toresson H, Ruscher K, Wieloch T. Rho kinase inhibition protects CA1 cells in organotypic hippocampal slices during in vitro ischemia. Brain Res 2009; 1316:92-100. [PMID: 20026316 DOI: 10.1016/j.brainres.2009.11.087] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Accepted: 11/23/2009] [Indexed: 01/24/2023]
Abstract
The actin cytoskeleton is a dynamic superstructure that regulates multiple cellular functions and that has been implicated in cell death regulation. We investigated whether modulating the neuronal actin cytoskeleton polymerization by Rho-GTPase kinase (ROCK) inhibition influences cell death in hippocampal neuronal cultures and in murine organotypic hippocampal slice cultures subjected to in vitro ischemia (IVI). During IVI, spines on vehicle treated hippocampal neurons collapsed and large dendritic actin aggregates were formed. Following ROCK inhibition by Y27632, the actin aggregates were markedly smaller while large filopodia extended from the dendritic trunk. Y27632 also provided strong neuroprotection of hippocampal pyramidal CA1 neurons, which was of similar magnitude as protection by NMDA receptor blockade. Likewise, treatment with the F-actin depolymerizing agent latrunculin during IVI diminished actin aggregation and mitigated cell death following IVI. We propose that ROCK inhibition protects neurons against ischemic damage by disrupting actin polymerization thereby mitigating NMDA receptor induced toxicity and releasing ATP bound to actin for cellular energy use. We conclude that ROCK inhibitors abrogate multiple detrimental processes and could therefore be useful in stroke therapy.
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Affiliation(s)
- Lennart Gisselsson
- Laboratory for Experimental Brain Research, Wallenberg Neuroscience Center, Lund University, BMC A13, S-22184 Lund, Sweden
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71
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The T3SS effector EspT defines a new category of invasive enteropathogenic E. coli (EPEC) which form intracellular actin pedestals. PLoS Pathog 2009; 5:e1000683. [PMID: 20011125 PMCID: PMC2782363 DOI: 10.1371/journal.ppat.1000683] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 11/05/2009] [Indexed: 02/07/2023] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) strains are defined as extracellular pathogens which nucleate actin rich pedestal-like membrane extensions on intestinal enterocytes to which they intimately adhere. EPEC infection is mediated by type III secretion system effectors, which modulate host cell signaling. Recently we have shown that the WxxxE effector EspT activates Rac1 and Cdc42 leading to formation of membrane ruffles and lamellipodia. Here we report that EspT-induced membrane ruffles facilitate EPEC invasion into non-phagocytic cells in a process involving Rac1 and Wave2. Internalized EPEC resides within a vacuole and Tir is localized to the vacuolar membrane, resulting in actin polymerization and formation of intracellular pedestals. To the best of our knowledge this is the first time a pathogen has been shown to induce formation of actin comets across a vacuole membrane. Moreover, our data breaks the dogma of EPEC as an extracellular pathogen and defines a new category of invasive EPEC. Enteropathogenic E. coli (EPEC) is an important diarrheal pathogen responsible for significant infant mortality in the developing world and is increasingly associated with sporadic outbreaks in the developed world. The virulence strategy of EPEC revolves around a conserved Type 3 secretion system (T3SS) which translocates bacterial effector proteins directly into host cells. EPEC is considered to be a non-invasive pathogen which intimately adheres to host cells and polymerizes actin rich pedestals on which extracellular bacteria rest. Recently we have identified the T3SS effector EspT which activates the mammalian Rho GTPases Rac1 and Cdc42, resulting in the formation of membrane ruffles and lamellipodia. In this study we dissect the signaling pathway utilized by EspT to nucleate membrane ruffles and demonstrate that these ruffles can promote EPEC invasion of host cells. Furthermore, we show that internalized EPEC are bound within a vacuole. We also report for the first time the ability of a bacterial pathogen to form actin comet tails across a vacuole membrane. In addition to providing novel insights into the subversion of cellular signaling by invasive pathogens, our study also breaks the long held dogma of EPEC as an extracellular pathogen and will have implications on how future EPEC infections are diagnosed and treated.
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72
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Wang YH, Yan ZQ, Shen BR, Zhang L, Zhang P, Jiang ZL. Vascular smooth muscle cells promote endothelial cell adhesion via microtubule dynamics and activation of paxillin and the extracellular signal-regulated kinase (ERK) pathway in a co-culture system. Eur J Cell Biol 2009; 88:701-9. [DOI: 10.1016/j.ejcb.2009.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 06/11/2009] [Accepted: 06/12/2009] [Indexed: 12/25/2022] Open
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73
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Kim H, Nakamura F, Lee W, Shifrin Y, Arora P, McCulloch CA. Filamin A is required for vimentin-mediated cell adhesion and spreading. Am J Physiol Cell Physiol 2009; 298:C221-36. [PMID: 19776392 DOI: 10.1152/ajpcell.00323.2009] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Cell adhesion and spreading are regulated by complex interactions involving the cytoskeleton and extracellular matrix proteins. We examined the interaction of the intermediate filament protein vimentin with the actin cross-linking protein filamin A in regulation of spreading in HEK-293 and 3T3 cells. Filamin A and vimentin-expressing cells were well spread on collagen and exhibited numerous cell extensions enriched with filamin A and vimentin. By contrast, cells treated with small interfering RNA (siRNA) to knock down filamin A or vimentin were poorly spread; both of these cell populations exhibited >50% reductions of cell adhesion, cell surface beta1 integrin expression, and beta1 integrin activation. Knockdown of filamin A reduced vimentin phosphorylation and blocked recruitment of vimentin to cell extensions, whereas knockdown of filamin and/or vimentin inhibited the formation of cell extensions. Reduced vimentin phosphorylation, cell spreading, and beta1 integrin surface expression, and activation were phenocopied in cells treated with the protein kinase C inhibitor bisindolylmaleimide; cell spreading was also reduced by siRNA knockdown of protein kinase C-epsilon. By immunoprecipitation of cell lysates and by pull-down assays using purified proteins, we found an association between filamin A and vimentin. Filamin A also associated with protein kinase C-epsilon, which was enriched in cell extensions. These data indicate that filamin A associates with vimentin and to protein kinase C-epsilon, thereby enabling vimentin phosphorylation, which is important for beta1 integrin activation and cell spreading on collagen.
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Affiliation(s)
- Hugh Kim
- Canadian Institutes of Health Group in Matrix Dynamics, University of Toronto, Toronto, Ontario, M5S 3E2, Canada.
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74
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Actin dynamics and Rho GTPases regulate the size and formation of parasitophorous vacuoles containing Coxiella burnetii. Infect Immun 2009; 77:4609-20. [PMID: 19635823 DOI: 10.1128/iai.00301-09] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Q fever is a disease caused by Coxiella burnetii. In the host cell, this pathogen generates a large parasitophorous vacuole (PV) with lysosomal characteristics. Here we show that F-actin not only is recruited to but also is involved in the formation of the typical PV. Treatment of infected cells with F-actin-depolymerizing agents alters PV development. The small PVs formed in latrunculin B-treated cells were loaded with transferrin and Lysotracker and labeled with an antibody against cathepsin D, suggesting that latrunculin B did not affect vacuole cargo and its lysosomal characteristics. Nevertheless, the vacuoles were unable to fuse with latex bead phagosomes. It is known that actin dynamics are regulated by the Rho family GTPases. To assess the role of these GTPases in PV formation, infected cells were transfected with pEGFP expressing wild-type and mutant Rac1, Cdc42, and RhoA proteins. Rac1 did not show significant PV association. In contrast, PVs were decorated by both the wild types and constitutively active mutants of Cdc42 and RhoA. This association was inhibited by treatment of infected cells with chloramphenicol, suggesting a role for bacterial protein synthesis in the recruitment of these proteins. Interestingly, a decrease in vacuole size was observed in cells expressing dominant-negative RhoA; however, these small vacuoles accumulated transferrin, Lysotracker, and DQ-BSA. In summary, these results suggest that actin, likely modulated by the GTPases RhoA and Cdc42 and by bacterial proteins, is involved in the formation of the typical PV.
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75
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French CT, Panina EM, Yeh SH, Griffith N, Arambula DG, Miller JF. The Bordetella type III secretion system effector BteA contains a conserved N-terminal motif that guides bacterial virulence factors to lipid rafts. Cell Microbiol 2009; 11:1735-49. [PMID: 19650828 PMCID: PMC2788067 DOI: 10.1111/j.1462-5822.2009.01361.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Bordetella type III secretion system (T3SS) effector protein BteA is necessary and sufficient for rapid cytotoxicity in a wide range of mammalian cells. We show that BteA is highly conserved and functionally interchangeable between Bordetella bronchiseptica, Bordetella pertussis and Bordetella parapertussis. The identification of BteA sequences required for cytotoxicity allowed the construction of non-cytotoxic mutants for localization studies. BteA derivatives were targeted to lipid rafts and showed clear colocalization with cortical actin, ezrin and the lipid raft marker GM1. We hypothesized that BteA associates with the cytoplasmic face of lipid rafts to locally modulate host cell responses to Bordetella attachment. B. bronchiseptica adhered to host cells almost exclusively to GM1-enriched lipid raft microdomains and BteA colocalized to these same sites following T3SS-mediated translocation. Disruption of lipid rafts with methyl-beta-cyclodextrin protected cells from T3SS-induced cytotoxicity. Localization to lipid rafts was mediated by a 130-amino-acid lipid raft targeting domain at the N-terminus of BteA, and homologous domains were identified in virulence factors from other bacterial species. Lipid raft targeting sequences from a T3SS effector (Plu4750) and an RTX-type toxin (Plu3217) from Photorhabdus luminescens directed fusion proteins to lipid rafts in a manner identical to the N-terminus of BteA.
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Affiliation(s)
- Christopher T French
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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76
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Nakamura N, Naruse K, Matsuki T, Hamada Y, Nakashima E, Kamiya H, Matsubara T, Enomoto A, Takahashi M, Oiso Y, Nakamura J. Adiponectin promotes migration activities of endothelial progenitor cells via Cdc42/Rac1. FEBS Lett 2009; 583:2457-63. [PMID: 19596003 DOI: 10.1016/j.febslet.2009.07.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 07/07/2009] [Accepted: 07/09/2009] [Indexed: 12/17/2022]
Abstract
Adiponectin has anti-atherosclerotic effects through its direct actions on vascular cells. The present study investigates the molecular mechanisms of adiponectin in the migration of endothelial progenitor cells (EPCs) which play an important role in neovascularization and re-endothelization. The phosphorylation of Akt and the activations of Cdc42 and Rac1 were significantly increased by adiponectin. Adiponectin increased the migration activity of EPCs, which was completely inhibited by a PI3-kinase inhibitor. siRNA of Cdc42 or Rac1 completely inhibited the adiponectin-induced migration, but siRNA of Akt had no effects, indicating that adiponectin promotes the migration activities of EPCs mainly through PI3-kinase/Cdc42/Rac1.
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Affiliation(s)
- Nobuhisa Nakamura
- Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya, Japan
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77
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Lai FPL, Szczodrak M, Oelkers JM, Ladwein M, Acconcia F, Benesch S, Auinger S, Faix J, Small JV, Polo S, Stradal TEB, Rottner K. Cortactin promotes migration and platelet-derived growth factor-induced actin reorganization by signaling to Rho-GTPases. Mol Biol Cell 2009; 20:3209-23. [PMID: 19458196 DOI: 10.1091/mbc.e08-12-1180] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Dynamic actin rearrangements are initiated and maintained by actin filament nucleators, including the Arp2/3-complex. This protein assembly is activated in vitro by distinct nucleation-promoting factors such as Wiskott-Aldrich syndrome protein/Scar family proteins or cortactin, but the relative in vivo functions of each of them remain controversial. Here, we report the conditional genetic disruption of murine cortactin, implicated previously in dynamic actin reorganizations driving lamellipodium protrusion and endocytosis. Unexpectedly, cortactin-deficient cells showed little changes in overall cell morphology and growth. Ultrastructural analyses and live-cell imaging studies revealed unimpaired lamellipodial architecture, Rac-induced protrusion, and actin network turnover, although actin assembly rates in the lamellipodium were modestly increased. In contrast, platelet-derived growth factor-induced actin reorganization and Rac activation were impaired in cortactin null cells. In addition, cortactin deficiency caused reduction of Cdc42 activity and defects in random and directed cell migration. Reduced migration of cortactin null cells could be restored, at least in part, by active Rac and Cdc42 variants. Finally, cortactin removal did not affect the efficiency of receptor-mediated endocytosis. Together, we conclude that cortactin is fully dispensable for Arp2/3-complex activation during lamellipodia protrusion or clathrin pit endocytosis. Furthermore, we propose that cortactin promotes cell migration indirectly, through contributing to activation of selected Rho-GTPases.
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Affiliation(s)
- Frank P L Lai
- Cytoskeleton Dynamics Group, Helmholtz Centre for Infection Research, D-38124 Braunschweig, Germany
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78
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Tsai WC, Hsu PWC, Lai TC, Chau GY, Lin CW, Chen CM, Lin CD, Liao YL, Wang JL, Chau YP, Hsu MT, Hsiao M, Huang HD, Tsou AP. MicroRNA-122, a tumor suppressor microRNA that regulates intrahepatic metastasis of hepatocellular carcinoma. Hepatology 2009; 49:1571-82. [PMID: 19296470 DOI: 10.1002/hep.22806] [Citation(s) in RCA: 465] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED MicroRNAs (miRNAs), which are inhibitors of gene expression, participate in diverse biological functions and in carcinogenesis. In this study, we show that liver-specific microRNA-122 (miR-122) is significantly down-regulated in liver cancers with intrahepatic metastasis and negatively regulates tumorigenesis. Restoration of miR-122 in metastatic Mahlavu and SK-HEP-1 cells significantly reduced in vitro migration, invasion, and anchorage-independent growth as well as in vivo tumorigenesis, angiogenesis, and intrahepatic metastasis in an orthotopic liver cancer model. Because an inverse expression pattern is often present between an miRNA and its target genes, we used a computational approach and identified multiple miR-122 candidate target genes from two independent expression microarray datasets. Thirty-two target genes were empirically verified, and this group of genes was enriched with genes regulating cell movement, cell morphology, cell-cell signaling, and transcription. We further showed that one of the miR-122 targets, ADAM17 (a disintegrin and metalloprotease 17) is involved in metastasis. Silencing of ADAM17 resulted in a dramatic reduction of in vitro migration, invasion, in vivo tumorigenesis, angiogenesis, and local invasion in the livers of nude mice, which is similar to that which occurs with the restoration of miR-122. CONCLUSION Our study suggests that miR-122, a tumor suppressor microRNA affecting hepatocellular carcinoma intrahepatic metastasis by angiogenesis suppression, exerts some of its action via regulation of ADAM17. Restoration of miR-122 has a far-reaching effect on the cell. Using the concomitant down-regulation of its targets, including ADAM17, a rational therapeutic strategy based on miR-122 may prove to be beneficial for patients with hepatocellular carcinoma.
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Affiliation(s)
- Wei-Chih Tsai
- Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
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79
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Lizárraga F, Poincloux R, Romao M, Montagnac G, Le Dez G, Bonne I, Rigaill G, Raposo G, Chavrier P. Diaphanous-related formins are required for invadopodia formation and invasion of breast tumor cells. Cancer Res 2009; 69:2792-800. [PMID: 19276357 DOI: 10.1158/0008-5472.can-08-3709] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Proteolytic degradation of the extracellular matrix by metastatic tumor cells is initiated by the formation of invadopodia, i.e., actin-driven filopodia-like membrane protrusions endowed with matrix-degradative activity. A signaling cascade involving neural Wiskott-Aldrich syndrome protein and the Arp2/3 actin nucleating complex is involved in actin assembly at invadopodia. Yet, the mechanism of invadopodia formation is poorly understood. Based on their role as actin nucleators in cytoskeletal rearrangements, including filopodia formation, we examined the function of Diaphanous-related formins (DRF) in invadopodia formation and invasion by breast tumor cells. Using small interfering RNA silencing of protein expression in highly invasive MDA-MB-231 breast adenocarcinoma cells, we show that three members of the DRF family (DRF1-DRF3) are required for invadopodia formation and two-dimensional matrix proteolysis. We also report that invasion of a three-dimensional Matrigel matrix involves filopodia-like protrusions enriched for invadopodial proteins, including membrane type 1 matrix metalloproteinase, which depend on DRFs for their formation. These data identify DRFs as critical components of the invasive apparatus of tumor cells in two-dimensional and three-dimensional matrices and suggest that different types of actin nucleators cooperate during the formation of invadopodia.
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80
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Faix J, Breitsprecher D, Stradal TEB, Rottner K. Filopodia: Complex models for simple rods. Int J Biochem Cell Biol 2009; 41:1656-64. [PMID: 19433307 DOI: 10.1016/j.biocel.2009.02.012] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Revised: 02/16/2009] [Accepted: 02/17/2009] [Indexed: 11/26/2022]
Abstract
Filopodia are prominent cell surface projections filled with bundles of linear actin filaments that drive their protrusion. These structures are considered important sensory organelles, for instance in neuronal growth cones or during the fusion of sheets of epithelial tissues. In addition, they can serve a precursor function in adhesion site or stress fibre formation. Actin filament assembly is essential for filopodia formation and turnover, yet the precise molecular mechanisms of filament nucleation and/or elongation are controversial. Indeed, conflicting reports on the molecular requirements of filopodia initiation have prompted researchers to propose different types and/or alternative or redundant mechanisms mediating this process. However, recent data shed new light on these questions, and they indicate that the balance of a limited set of biochemical activities can determine the structural outcome of a given filopodium. Here we focus on discussing our current view of the relevance of these activities, and attempt to propose a molecular mechanism of filopodia assembly based on a single core machinery.
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Affiliation(s)
- Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany.
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81
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Ohta T, Ikemoto Y, Saeki K, Koide T, Wakabayashi S. Histidine-rich glycoprotein and concanavalin A synergistically stimulate the phosphatidylinositol 3-kinase-independent signaling pathway in leukocytes leading to increased cell adhesion and changes in cell morphology. Cell Immunol 2009; 259:5-12. [DOI: 10.1016/j.cellimm.2009.05.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 05/01/2009] [Indexed: 11/29/2022]
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82
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Para A, Krischke M, Merlot S, Shen Z, Oberholzer M, Lee S, Briggs S, Firtel RA. Dictyostelium Dock180-related RacGEFs regulate the actin cytoskeleton during cell motility. Mol Biol Cell 2008; 20:699-707. [PMID: 19037099 DOI: 10.1091/mbc.e08-09-0899] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cell motility of amoeboid cells is mediated by localized F-actin polymerization that drives the extension of membrane protrusions to promote forward movements. We show that deletion of either of two members of the Dictyostelium Dock180 family of RacGEFs, DockA and DockD, causes decreased speed of chemotaxing cells. The phenotype is enhanced in the double mutant and expression of DockA or DockD complements the reduced speed of randomly moving DockD null cells' phenotype, suggesting that DockA and DockD are likely to act redundantly and to have similar functions in regulating cell movement. In this regard, we find that overexpressing DockD causes increased cell speed by enhancing F-actin polymerization at the sites of pseudopod extension. DockD localizes to the cell cortex upon chemoattractant stimulation and at the leading edge of migrating cells and this localization is dependent on PI3K activity, suggesting that DockD might be part of the pathway that links PtdIns(3,4,5)P(3) production to F-actin polymerization. Using a proteomic approach, we found that DdELMO1 is associated with DockD and that Rac1A and RacC are possible in vivo DockD substrates. In conclusion, our work provides a further understanding of how cell motility is controlled and provides evidence that the molecular mechanism underlying Dock180-related protein function is evolutionarily conserved.
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Affiliation(s)
- Alessia Para
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0380, USA
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83
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Bulgin RR, Arbeloa A, Chung JCS, Frankel G. EspT triggers formation of lamellipodia and membrane ruffles through activation of Rac-1 and Cdc42. Cell Microbiol 2008; 11:217-29. [PMID: 19016787 PMCID: PMC2688677 DOI: 10.1111/j.1462-5822.2008.01248.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Subversion of the eukaryotic cell cytoskeleton is a virulence strategy employed by many bacterial pathogens. Due to the pivotal role of Rho GTPases in actin dynamics they are common targets of bacterial effector proteins and toxins. IpgB1, IpgB2 (Shigella), SifA, SifB (Salmonella) and Map and EspM (attaching and effacing pathogens) constitute a family of type III secretion system effectors that subverts small GTPase signalling pathways. In this study we identified and characterized EspT from Citrobacter rodentium that triggers formation of lamellipodia on Swiss 3T3 and membrane ruffles on HeLa cells, which are reminiscent of the membrane ruffles induced by IpgB1. Ectopic expression of EspT and IpgB1, but not EspM, resulted in a mitochondrial localization. Using dominant negative constructs we found that EspT-induced actin remodelling is dependent on GTP-bound Rac-1 and Cdc42 but not ELMO or Dock180, which are hijacked by IpgB1 in order to form a Rac-1 specific guanine nucleotide exchange factor. Using pull-down assays with the Rac-1 and Cdc42 binding domains of Pak and WASP we demonstrate that EspT is capable of activating both Rac-1 and Cdc42. These results suggest that EspT modulates the host cell cytoskeleton through coactivation of Rac-1 and Cdc42 by a distinct mechanism.
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Affiliation(s)
- Richard R Bulgin
- Centre for Molecular Microbiology and Infection, Division of Cell and Molecular Biology, Imperial College, London SW7 2AZ, UK
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