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Zhao S, Xu Q, Cui Y, Yao S, Jin S, Zhang Q, Wen Z, Ruan H, Liang X, Chao Y, Gong S, Sansonetti P, Wei K, Tang H, Jiu Y. Salmonella effector SopB reorganizes cytoskeletal vimentin to maintain replication vacuoles for efficient infection. Nat Commun 2023; 14:478. [PMID: 36717589 DOI: 10.1038/s41467-023-36123-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 01/16/2023] [Indexed: 01/31/2023] Open
Abstract
A variety of intracellular bacteria modulate the host cytoskeleton to establish subcellular niches for replication. However, the role of intermediate filaments, which are crucial for mechanical strength and resilience of the cell, and in bacterial vacuole preservation remains unclear. Here, we show that Salmonella effector SopB reorganizes the vimentin network to form cage-like structures that surround Salmonella-containing vacuoles (SCVs). Genetic removal of vimentin markedly disrupts SCV organization, significantly reduces bacterial replication and cell death. Mechanistically, SopB uses its N-terminal Cdc42-binding domain to interact with and activate Cdc42 GTPase, which in turn recruits vimentin around SCVs. A high-content imaging-based screening identified that MEK1/2 inhibition led to vimentin dispersion. Our work therefore elucidates the signaling axis SopB-Cdc42-MEK1/2 as mobilizing host vimentin to maintain concrete SCVs and identifies a mechanism contributing to Salmonella replication. Importantly, Trametinib, a clinically-approved MEK1/2 inhibitor identified in the screen, displayed significant anti-infection efficacy against Salmonella both in vitro and in vivo, and may provide a therapeutic option for treating drug-tolerant salmonellosis.
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2
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Yen CH, Li ST, Cheng NC, Ji YR, Wang JH, Young TH. Label-free platform on pH-responsive chitosan: Adhesive heterogeneity for cancer stem-like cell isolation from A549 cells via integrin β4. Carbohydr Polym 2020; 239:116168. [PMID: 32414450 DOI: 10.1016/j.carbpol.2020.116168] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 03/11/2020] [Accepted: 03/12/2020] [Indexed: 12/25/2022]
Abstract
Great efforts have been paid to develop methodologies for cancer stem-like cell (CSLC) isolation in anti-cancer research. The major obstacle lies in the lack of generic biomarkers for different cancer types and the requirement of complicated immuno-labeling procedures. The purpose of this study is to establish a label-free platform for CSLC isolation using pH-responsive chitosan. Based on the adhesive heterogeneity, 15.7 ± 1.9 % of human non-small cell lung cancer (NSCLC) cell line A549 detached from the chitosan substrate following medium pH elevation from 6.99 to 7.65 within 1 h. As a result, this subpopulation of cells with low adhesiveness exhibited superior CSLC hallmarks, including self-renewal, invasive and metastatic potential, therapeutic-resistance, colony formation in vitro, as well as nude mice xenograft in vivo for tumorigenesis, in comparison with their high-adhesive counterpart. Furthermore, integrin β4 is decisive in controlling CSLC detachment of NSCLC. Conclusively, this pH-dependent isolation provides new insights into biomaterial-based CSLC isolation.
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Vohnoutka RB, Gulvady AC, Goreczny G, Alpha K, Handelman SK, Sexton JZ, Turner CE. The focal adhesion scaffold protein Hic-5 regulates vimentin organization in fibroblasts. Mol Biol Cell 2019; 30:3037-3056. [PMID: 31644368 PMCID: PMC6880880 DOI: 10.1091/mbc.e19-08-0442] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Focal adhesion (FA)-stimulated reorganization of the F-actin cytoskeleton regulates cellular size, shape, and mechanical properties. However, FA cross-talk with the intermediate filament cytoskeleton is poorly understood. Genetic ablation of the FA-associated scaffold protein Hic-5 in mouse cancer-associated fibroblasts (CAFs) promoted a dramatic collapse of the vimentin network, which was rescued following EGFP-Hic-5 expression. Vimentin collapse correlated with a loss of detergent-soluble vimentin filament precursors and decreased vimentin S72/S82 phosphorylation. Additionally, fluorescence recovery after photobleaching analysis indicated impaired vimentin dynamics. Microtubule (MT)-associated EB1 tracking and Western blotting of MT posttranslational modifications indicated no change in MT dynamics that could explain the vimentin collapse. However, pharmacological inhibition of the RhoGTPase Cdc42 in Hic-5 knockout CAFs rescued the vimentin collapse, while pan-formin inhibition with SMIFH2 promoted vimentin collapse in Hic-5 heterozygous CAFs. Our results reveal novel regulation of vimentin organization/dynamics by the FA scaffold protein Hic-5 via modulation of RhoGTPases and downstream formin activity.
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Affiliation(s)
- Rishel B Vohnoutka
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Anushree C Gulvady
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Gregory Goreczny
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Kyle Alpha
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Samuel K Handelman
- Division of Gastroenterology, Department of Internal Medicine, Michigan Medicine at the University of Michigan, Ann Arbor, MI 48109
| | - Jonathan Z Sexton
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109
| | - Christopher E Turner
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
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4
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Willems E, Dedobbeleer M, Digregorio M, Lombard A, Goffart N, Lumapat PN, Lambert J, Van den Ackerveken P, Szpakowska M, Chevigné A, Scholtes F, Rogister B. Aurora A plays a dual role in migration and survival of human glioblastoma cells according to the CXCL12 concentration. Oncogene 2018; 38:73-87. [PMID: 30082913 PMCID: PMC6755987 DOI: 10.1038/s41388-018-0437-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 07/10/2018] [Accepted: 07/11/2018] [Indexed: 12/13/2022]
Abstract
Primary glioblastoma is the most frequent human brain tumor in adults and is generally fatal due to tumor recurrence. We previously demonstrated that glioblastoma-initiating cells invade the subventricular zones and promote their radio-resistance in response to the local release of the CXCL12 chemokine. In this work, we show that the mitotic Aurora A kinase (AurA) is activated through the CXCL12–CXCR4 pathway in an ERK1/2-dependent manner. Moreover, the CXCL12–ERK1/2 signaling induces the expression of Ajuba, the main cofactor of AurA, which allows the auto-phosphorylation of AurA. We show that AurA contributes to glioblastoma cell survival, radio-resistance, self-renewal, and proliferation regardless of the exogenous stimulation with CXCL12. On the other hand, AurA triggers the CXCL12-mediated migration of glioblastoma cells in vitro as well as the invasion of the subventricular zone in xenograft experiments. Moreover, AurA regulates cytoskeletal proteins (i.e., Actin and Vimentin) and favors the pro-migratory activity of the Rho-GTPase CDC42 in response to CXCL12. Altogether, these results show that AurA, a well-known kinase of the mitotic machinery, may play alternative roles in human glioblastoma according to the CXCL12 concentration.
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Affiliation(s)
- Estelle Willems
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium
| | - Matthias Dedobbeleer
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium
| | - Marina Digregorio
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium
| | - Arnaud Lombard
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium.,Department of Neurosurgery, CHU of Liège, Liège, Belgium
| | - Nicolas Goffart
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium
| | - Paul Noel Lumapat
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium
| | - Jeremy Lambert
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium.,Department of Neurosurgery, CHU of Liège, Liège, Belgium
| | | | - Martyna Szpakowska
- Department of Infection and Immunity, Immuno-Pharmacology and Interactomics, Luxembourg Institute of Health, Esch-sur-Alzette, Luxembourg
| | - Andy Chevigné
- Department of Infection and Immunity, Immuno-Pharmacology and Interactomics, Luxembourg Institute of Health, Esch-sur-Alzette, Luxembourg
| | - Felix Scholtes
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium.,Department of Neurosurgery, CHU of Liège, Liège, Belgium
| | - Bernard Rogister
- Laboratory of Nervous System Diseases and Therapy, GIGA-Neuroscience, University of Liège, Liège, Belgium. .,Department of Neurology, CHU of Liège, Liège, Belgium.
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5
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Tarbet HJ, Dolat L, Smith TJ, Condon BM, O'Brien ET, Valdivia RH, Boyce M. Site-specific glycosylation regulates the form and function of the intermediate filament cytoskeleton. eLife 2018. [PMID: 29513221 PMCID: PMC5841932 DOI: 10.7554/elife.31807] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intermediate filaments (IF) are a major component of the metazoan cytoskeleton and are essential for normal cell morphology, motility, and signal transduction. Dysregulation of IFs causes a wide range of human diseases, including skin disorders, cardiomyopathies, lipodystrophy, and neuropathy. Despite this pathophysiological significance, how cells regulate IF structure, dynamics, and function remains poorly understood. Here, we show that site-specific modification of the prototypical IF protein vimentin with O-linked β-N-acetylglucosamine (O-GlcNAc) mediates its homotypic protein-protein interactions and is required in human cells for IF morphology and cell migration. In addition, we show that the intracellular pathogen Chlamydia trachomatis, which remodels the host IF cytoskeleton during infection, requires specific vimentin glycosylation sites and O-GlcNAc transferase activity to maintain its replicative niche. Our results provide new insight into the biochemical and cell biological functions of vimentin O-GlcNAcylation, and may have broad implications for our understanding of the regulation of IF proteins in general. Like the body's skeleton, the cytoskeleton gives shape and structure to the inside of a cell. Yet, unlike a skeleton, the cytoskeleton is ever changing. The cytoskeleton consists of many fibers each made from chains of protein molecules. One of these proteins is called vimentin and it forms intermediate filaments in the cytoskeleton. Many different types of cells contain vimentin and a lot of it is found in cancer cells that have spread beyond their original location to other sites in the body. Cells use chemical modifications to regulate cytoskeleton proteins. For example, through a process called glycosylation, cells can reversibly attach a sugar modification called O-GlcNAc to vimentin. O-GlcNAc can be attached to several different parts of vimentin and each location may have a different effect. It is not currently clear how cells control their vimentin filaments or what role O-GlcNAc plays in this process. Using genetic engineering, Tarbet et al. produced human cells in the laboratory with modified vimentin proteins. These altered proteins lacked some of the sites for O-GlcNAc attachment. The goal was to see whether the loss of O-GlcNAc at a specific location would affect fiber formation and cell behavior. The results showed one site where vimentin needs O-GlcNAc to form fibers. Without O-GlcNAc at this site, cells could not migrate towards chemical signals. In addition, in normal human cells, Chlamydia bacteria hijack vimentin and rearrange the filaments to form a cage around themselves for protection. However, the cells lacking O-GlcNAc on vimentin were resistant to infection by Chlamydia bacteria. These findings highlight the importance of O-GlcNAc on vimentin in healthy cells and during infection. Vimentin’s contribution to cell migration may also help to explain its role in the spread of cancer. The importance of O-GlcNAc suggests it could be a new target for therapies. Yet, it also highlights the need for caution due to the delicate balance between the activity of vimentin in healthy and diseased cells. In addition, human cells produce about 70 other vimentin-like proteins and further work will examine if they are also affected by O-GlcNAc.
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Affiliation(s)
- Heather J Tarbet
- Department of Biochemistry, Duke University School of Medicine, Durham, United States
| | - Lee Dolat
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, United States.,Center for Host-Microbial Interactions, Duke University School of Medicine, Durham, United States
| | - Timothy J Smith
- Department of Biochemistry, Duke University School of Medicine, Durham, United States
| | - Brett M Condon
- Department of Biochemistry, Duke University School of Medicine, Durham, United States
| | - E Timothy O'Brien
- Department of Biochemistry, Duke University School of Medicine, Durham, United States.,Department of Physics and Astronomy, University of North Carolina, Chapel Hill, United States
| | - Raphael H Valdivia
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, United States.,Center for Host-Microbial Interactions, Duke University School of Medicine, Durham, United States
| | - Michael Boyce
- Department of Biochemistry, Duke University School of Medicine, Durham, United States.,Center for Host-Microbial Interactions, Duke University School of Medicine, Durham, United States
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Leduc C, Etienne-Manneville S. Regulation of microtubule-associated motors drives intermediate filament network polarization. J Cell Biol 2017; 216:1689-1703. [PMID: 28432079 PMCID: PMC5461013 DOI: 10.1083/jcb.201607045] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 01/16/2017] [Accepted: 03/03/2017] [Indexed: 11/22/2022] Open
Abstract
Intermediate filaments (IFs) are key players in the control of cell morphology and structure as well as in active processes such as cell polarization, migration, and mechanoresponses. However, the regulatory mechanisms controlling IF dynamics and organization in motile cells are still poorly understood. In this study, we investigate the mechanisms leading to the polarized rearrangement of the IF network along the polarity axis. Using photobleaching and photoconversion experiments in glial cells expressing vimentin, glial fibrillary acidic protein, and nestin, we show that the distribution of cytoplasmic IFs results from a continuous turnover based on the cooperation of an actin-dependent retrograde flow and anterograde and retrograde microtubule-dependent transports. During wound-induced astrocyte polarization, IF transport becomes directionally biased from the cell center toward the cell front. Such asymmetry in the transport is mainly caused by a Cdc42- and atypical PKC-dependent inhibition of dynein-dependent retrograde transport. Our results show how polarity signaling can affect the dynamic turnover of the IF network to promote the polarization of the network itself.
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Affiliation(s)
- Cécile Leduc
- Institut Pasteur Paris, Cell Polarity, Migration and Cancer Unit, UMR 3691, Equipe Labellisée Ligue Contre le Cancer, Centre National de la Recherché Scientifique, 75724 Paris, France
| | - Sandrine Etienne-Manneville
- Institut Pasteur Paris, Cell Polarity, Migration and Cancer Unit, UMR 3691, Equipe Labellisée Ligue Contre le Cancer, Centre National de la Recherché Scientifique, 75724 Paris, France.
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7
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Abstract
In this study we show that binding of mitochondria to vimentin intermediate filaments (VIF) is regulated by GTPase Rac1. The activation of Rac1 leads to a redoubling of mitochondrial motility in murine fibroblasts. Using double-mutants Rac1(G12V, F37L) and Rac1(G12V, Y40H) that are capable to activate different effectors of Rac1, we show that mitochondrial movements are regulated through PAK1 kinase. The involvement of PAK1 kinase is also confirmed by the fact that expression of its auto inhibitory domain (PID) blocks the effect of activated Rac1 on mitochondrial motility. The observed effect of Rac1 and PAK1 kinase on mitochondria depends on phosphorylation of the Ser-55 of vimentin. Besides the effect on motility Rac1 activation also decreases the mitochondrial membrane potential (MMP) which is detected by ∼20% drop of the fluorescence intensity of mitochondria stained with the potential sensitive dye TMRM. One of important consequences of the discovered regulation of MMP by Rac1 and PAK1 is a spatial differentiation of mitochondria in polarized fibroblasts: at the front of the cell they are less energized (by ∼25%) than at the rear part.
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Affiliation(s)
- Elena A Matveeva
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
| | - Larisa S Venkova
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
| | - Ivan S Chernoivanenko
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
| | - Alexander A Minin
- Institute of Protein Research, Russian Academy of Sciences, Department of Cell Biology, Moscow 119988, Russia
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8
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Abstract
Transformation of a normal cell to a cancer cell is caused by mutations in genes that regulate proliferation, apoptosis, and invasion. Small GTPases such as Ras, Rho, Rac and Cdc42 orchestrate many of the signals that are required for malignant transformation. The p21-activated kinases (PAKs) are effectors of Rac and Cdc42. PAKs are a family of serine/threonine protein kinases comprised of six isoforms (PAK1–6), and they play important roles in cytoskeletal dynamics, cell survival and proliferation. They act as key signal transducers in several cancer signaling pathways, including Ras, Raf, NFκB, Akt, Bad and p53. Although PAKs are not mutated in cancers, they are overexpressed, hyperactivated or amplified in several human tumors and their role in cell transformation make them attractive therapeutic targets. This review discusses the evidence that PAK is important for cell transformation and some key signaling pathways it regulates. This review primarily discusses Group I PAKs (PAK1, PAK2 and PAK3) as Group II PAKs (PAK4, PAK5 and PAK6) are discussed elsewhere in this issue (by Minden).
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Affiliation(s)
- Diana Zi Ye
- Department of Pharmacology; Perelman School of Medicine; University of Pennsylvania; Philadelphia, PA USA
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9
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Robert A, Herrmann H, Davidson MW, Gelfand VI. Microtubule-dependent transport of vimentin filament precursors is regulated by actin and by the concerted action of Rho- and p21-activated kinases. FASEB J 2014; 28:2879-90. [PMID: 24652946 DOI: 10.1096/fj.14-250019] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Intermediate filaments (IFs) form a dense and dynamic network that is functionally associated with microtubules and actin filaments. We used the GFP-tagged vimentin mutant Y117L to study vimentin-cytoskeletal interactions and transport of vimentin filament precursors. This mutant preserves vimentin interaction with other components of the cytoskeleton, but its assembly is blocked at the unit-length filament (ULF) stage. ULFs are easy to track, and they allow a reliable and quantifiable analysis of movement. Our results show that in cultured human vimentin-negative SW13 cells, 2% of vimentin-ULFs move along microtubules bidirectionally, while the majority are stationary and tightly associated with actin filaments. Rapid motor-dependent transport of ULFs along microtubules is enhanced ≥ 5-fold by depolymerization of actin cytoskeleton with latrunculin B. The microtubule-dependent transport of vimentin ULFs is further regulated by Rho-kinase (ROCK) and p21-activated kinase (PAK): ROCK inhibits ULF transport, while PAK stimulates it. Both kinases act on microtubule transport independently of their effects on actin cytoskeleton. Our study demonstrates the importance of the actin cytoskeleton to restrict IF transport and reveals a new role for PAK and ROCK in the regulation of IF precursor transport.-Robert, A., Herrmann, H., Davidson, M. W., and Gelfand, V. I. Microtubule-dependent transport of vimentin filament precursors is regulated by actin and by the concerted action of Rho- and p21-activated kinases.
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Affiliation(s)
- Amélie Robert
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Harald Herrmann
- Division of Molecular Genetics, German Cancer Research Center, Heidelberg, Germany; and
| | - Michael W Davidson
- National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, Tallahassee, Florida, USA
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA;
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10
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Teo CSH, Chu JJH. Cellular vimentin regulates construction of dengue virus replication complexes through interaction with NS4A protein. J Virol 2014; 88:1897-913. [PMID: 24284321 PMCID: PMC3911532 DOI: 10.1128/jvi.01249-13] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 11/20/2013] [Indexed: 01/23/2023] Open
Abstract
Dengue virus (DENV) interacts with host cellular factors to construct a more favorable environment for replication, and the interplay between DENV and the host cellular cytoskeleton may represent one of the potential antiviral targeting sites. However, the involvement of cellular vimentin intermediate filaments in DENV replication has been explored less. Here, we revealed the direct interaction between host cellular vimentin and DENV nonstructural protein 4A (NS4A), a known component of the viral replication complex (RC), during DENV infection using tandem affinity purification, coimmunoprecipitation, and scanning electron microscopy. Furthermore, the dynamics of vimentin-NS4A interaction were demonstrated by using confocal three-dimensional (3D) reconstruction and proximity ligation assay. Most importantly, we report for the first time the discovery of the specific region of NS4A that interacts with vimentin lies within the first 50 amino acid residues at the cytosolic N-terminal domain of NS4A (N50 region). Besides identifying vimentin-NS4A interaction, vimentin reorganization and phosphorylation by calcium calmodulin-dependent protein kinase II occurs during DENV infection, signifying that vimentin reorganization is important in maintaining and supporting the DENV RCs. Interestingly, we found that gene silencing of vimentin by small interfering RNA induced a significant alteration in the distribution of RCs in DENV-infected cells. This finding further supports the crucial role of intact vimentin scaffold in localizing and concentrating DENV RCs at the perinuclear site, thus facilitating efficient viral RNA replication. Collectively, our findings implicate the biological and functional significance of vimentin during DENV replication, as we propose that the association of DENV RCs with vimentin is mediated by DENV NS4A.
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Affiliation(s)
- Catherine Su Hui Teo
- Laboratory of Molecular RNA Virology and Antiviral Strategies, Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore
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11
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Berardi S, Caivano A, Ria R, Nico B, Savino R, Terracciano R, De Tullio G, Ferrucci A, De Luisi A, Moschetta M, Mangialardi G, Catacchio I, Basile A, Guarini A, Zito A, Ditonno P, Musto P, Dammacco F, Ribatti D, Vacca A. Four proteins governing overangiogenic endothelial cell phenotype in patients with multiple myeloma are plausible therapeutic targets. Oncogene 2011; 31:2258-69. [PMID: 21963844 DOI: 10.1038/onc.2011.412] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Bone marrow (BM) angiogenesis has an important role in the initiation and progression of multiple myeloma (MM). We looked at novel mechanisms of vessel formation in patients with MM through a comparative proteomic analysis between BM endothelial cells (ECs) of patients with active MM (MMECs) and ECs of patients with monoclonal gammopathy of undetermined significance (MGECs) and of subjects with benign anemia (normal ECs). Four proteins were found overexpressed in MMECs: filamin A, vimentin, α-crystallin B and 14-3-3ζ/δ protein, not yet linked to overangiogenic phenotype. These proteins gave a typical distribution in the BM of MM patients and in MMECs versus MGECs, plausibly according to a different functional state. Their expression was enhanced by vascular endothelial growth factor, fibroblast growth factor 2, hepatocyte growth factor and MM plasma cell conditioned medium in step with enhancement of MMEC angiogenesis. Their silencing RNA knockdown affected critical MMEC angiogenesis-related functions, such as spreading, migration and tubular morphogenesis. A gradual stabilization of 14-3-3ζ/δ protein was observed, with transition from normal ECs to MGECs and MMECs that may be a critical step for the angiogenic switch in MMECs and maintenance of the cell overangiogenic phenotype. These proteins were substantially impacted by anti-MM drugs, such as bortezomib, lenalidomide and panobinostat. Results suggest that these four proteins could be new targets for the antiangiogenic management of MM patients.
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Affiliation(s)
- S Berardi
- Department of Biomedical Sciences and Human Oncology, University of Bari Medical School, Bari, Italy
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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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13
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Abstract
Some of the characteristics of cancer cells are high rates of cell proliferation, cell survival, and the ability to invade surrounding tissue. The cytoskeleton has an essential role in these processes. Dynamic changes in the cytoskeleton are necessary for cell motility and cancer cells are dependent on motility for invasion and metastasis. The signaling pathways behind the reshaping and migrating properties of the cytoskeleton in cancer cells involve a group of Ras-related small GTPases and their effectors, including the p21-activated kinases (Paks). Paks are a family of serine/threonine protein kinases comprised of six isoforms (Pak 1-6), all of which are direct targets of the small GTPases Rac and Cdc42. Besides their role in cytoskeletal dynamics, Paks have recently been shown to regulate various other cellular activities, including cell survival, mitosis, and transcription. Paks are overexpressed and/or hyperactivated in several human tumors and their role in cell transformation makes them attractive therapeutic targets. Pak-targeted therapeutics may efficiently inhibit certain types of tumors and efforts to identify selective Pak-inhibitors are underway.
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Affiliation(s)
- Bettina Dummler
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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14
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Abstract
Cdc42GAP (GTPase-activating protein) has been implicated in the regulation of cell motility, adhesion, proliferation, and apoptosis. In this study, Cdc42GAP was cloned from smooth muscle tissues. Cdc42GAP, but not inactive R282A Cdc42GAP (alanine substitution at arginine-282), enhanced the GTP hydrolysis of Cdc42 in an in vitro assay. Furthermore, we developed an assay to evaluate the activity of Cdc42GAP in vivo. Stimulation of smooth muscle cells with 5-hydroxytryptamine (5-HT) resulted in the decrease in Cdc42GAP activity. The agonist-induced GAP suppression was reversed by reactive oxygen species inhibitors. Treatment with hydrogen peroxide also inhibited GAP activity in smooth muscle cells. Because the vimentin cytoskeleton undergoes dynamic changes in response to contractile activation, we evaluated the role of Cdc42GAP in regulating vimentin filaments. Smooth muscle cells were infected with retroviruses encoding wild-type Cdc42GAP or its R282A mutant. Expression of wild-type Cdc42GAP, but not mutant R282A GAP, inhibited the increase in the activation of Cdc42 upon agonist stimulation. Phosphorylation of p21-activated kinase (PAK) at Thr-423 (an indication of PAK activation), vimentin phosphorylation (Ser-56), partial disassembly and spatial remodeling, and contraction were also attenuated in smooth muscle cells expressing Cdc42GAP. Our results suggest that the activity of Cdc42GAP is regulated upon contractile activation, which is mediated by intracellular ROS. Cdc42GAP regulates the vimentin network through the Cdc42-PAK pathway in smooth muscle cells during 5-HT stimulation.
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Affiliation(s)
- Qing-Fen Li
- The Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208, USA
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15
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Barberis L, Pasquali C, Bertschy-Meier D, Cuccurullo A, Costa C, Ambrogio C, Vilbois F, Chiarle R, Wymann M, Altruda F, Rommel C, Hirsch E. Leukocyte transmigration is modulated by chemokine-mediated PI3Kγ-dependent phosphorylation of vimentin. Eur J Immunol 2009; 39:1136-46. [DOI: 10.1002/eji.200838884] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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16
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Abstract
Vascular smooth muscle is a key effector in the wall of blood vessels during the pathogenesis of hypertension. Various factors directly elicit smooth muscle cell contraction, migration, growth, and hypertrophy, which lead to the progression of hypertension. Crk-associated substrate (CAS), the first discovered member of the adapter protein CAS family, has recently emerged as a critical cellular component that regulates smooth muscle functions. In this review, the molecular structure and protein interactions of the CAS family members are summarized. Evidence for the role of CAS in the regulation of vascular smooth muscle contractility, cell migration, hypertrophy, and growth is presented. Regulation of CAS by novel tyrosine kinases/phosphatases and unique downstream signaling partners of CAS are also discussed. These new findings establish the important role for CAS in regulating vascular smooth muscle functions. The CAS-associated processes may be new biological targets for the development of new treatment of cardiovascular diseases such as hypertension.
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Affiliation(s)
- Dale D Tang
- Center for Cardiovascular Sciences, Albany Medical College, Albany, New York 12208, USA.
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17
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O'Rourke M, Ward C, Worthington J, McKenna J, Valentine A, Robson T, Hirst DG, McKeown SR. Evaluation of the antiangiogenic potential of AQ4N. Clin Cancer Res 2008; 14:1502-9. [PMID: 18316575 DOI: 10.1158/1078-0432.ccr-07-1262] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE A number of cytotoxic chemotherapy agents tested at low concentrations show antiangiogenic properties with limited cytotoxicity, e.g., cyclophosphamide, tirapazamine, and mitoxantrone. AQ4N is a bioreductive alkylaminoanthraquinone that is cytotoxic when reduced to AQ4; hence, it can be used to target hypoxic tumor cells. AQ4N is structurally similar to mitoxantrone and was evaluated for antiangiogenic properties without the need for bioreduction. EXPERIMENTAL DESIGN The effect of AQ4N and fumagillin on human microvascular endothelial cells (HMEC-1) was measured using a variety of in vitro assays, i.e., 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, wound scrape, tubule formation, rat aortic ring, and invasion assays. Low-dose AQ4N (20 mg/kg) was also given in vivo to mice bearing a tumor in a dorsal skin flap. RESULTS AQ4N (10(-11) to 10(-5) mol/L) had no effect on HMEC-1 viability. AQ4N (10(-9) to 10(-5)mol/L) caused a sigmoidal dose-dependent inhibition of endothelial cell migration in the wound scrape model. Fumagillin showed a similar response over a lower dose range (10(-13) to 10(-9) mol/L); however, the maximal inhibition was less (25% versus 43% for AQ4N). AQ4N inhibited HMEC-1 cell contacts on Matrigel (10(-8) to 10(-5) mol/L), HMEC-1 cell invasion, and sprouting in rat aorta explants. Immunofluorescence staining with tubulin, vimentim, dynein, and phalloidin revealed that AQ4N caused disruption to the cell cytoskeleton. When AQ4N (20 mg/kg) was given in vivo for 5 days, microvessels disappeared in LNCaP tumors grown in a dorsal skin flap. CONCLUSIONS This combination of assays has shown that AQ4N possesses antiangiogenic effects in normoxic conditions, which could potentially contribute to antitumor activity.
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Affiliation(s)
- Martin O'Rourke
- Biomedical Sciences Research Institute, University of Ulster, Coleraine, Northern Ireland, United Kingdom
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18
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Abstract
The intermediate filament (IF) network is one of the three cytoskeletal systems in smooth muscle. The type III IF proteins vimentin and desmin are major constituents of the network in smooth muscle cells and tissues. Lack of vimentin or desmin impairs contractile ability of various smooth muscle preparations, implying their important role for smooth muscle force development. The IF framework has long been viewed as a fixed cytostructure that solely provides mechanical integrity for the cell. However, recent studies suggest that the IF cytoskeleton is dynamic in mammalian cells in response to various external stimulation. In this review, the structure and biological properties of IF proteins in smooth muscle are summarized. The role of IF proteins in the modulation of smooth muscle force development and redistribution/translocation of signaling partners (such as p130 Crk-associated substrate, CAS) is depicted. This review also summarizes our latest understanding on how the IF network may be regulated in smooth muscle.
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Affiliation(s)
- Dale D Tang
- Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12208, USA.
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Houben F, Ramaekers FCS, Snoeckx LHEH, Broers JLV. Role of nuclear lamina-cytoskeleton interactions in the maintenance of cellular strength. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2007; 1773:675-86. [PMID: 17050008 DOI: 10.1016/j.bbamcr.2006.09.018] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Revised: 07/12/2006] [Accepted: 09/08/2006] [Indexed: 01/08/2023]
Abstract
The response of individual cells to cellular stress is vital for cellular functioning. A large network of physically interconnected cellular components, starting from the structural components of the cells' nucleus, via cytoskeleton filaments to adhesion molecules and the extracellular matrix, constitutes an integrated matrix that functions as a scaffold allowing the cell to cope with mechanical stress. Next to a role in mechanical properties, this network also has a mechanotransductional function in the response to mechanical stress. This signaling route does not only regulate a rapid reorganization of structural components such as actin filaments, but also stimulates for example gene activation via NFkappaB and other transcription factors. The importance of an intact mechano-signaling network is illustrated by the physiological consequences of several genetic defects of cellular network components e.g. actin, dystrophin, desmin and lamins. These give rise to an impaired response of the affected cells to mechanical stress and often result in dystrophy of the affected tissue. Recently, the importance of the cell nucleus in cellular strength has been established. Several new interconnecting proteins, such as the nesprins that link the nuclear lamina to the cytoskeleton, have been identified. Furthermore, the function of nuclear lamins in determining cellular strength and nuclear stability was illustrated in lamin-knock-out cells. Absence of the A-type lamins or mutations in these structural components of the nuclear lamina lead to an impaired cellular response to mechanical stress and disturbances in cytoskeletal organization. In addition, laminopathies show clinical phenotypes comparable to those seen for diseases resulting from genetic defects in cytoskeletal components, further indicating that lamins play a central role in maintaining the mechanical properties of the cell.
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Affiliation(s)
- F Houben
- Department of Molecular Cell Biology, Cardiovascular Research Institute Maastricht (CARIM) and Research Institute for Growth and Development (GROW), University of Maastricht, Maastricht, The Netherlands.
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20
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Li QF, Spinelli AM, Wang R, Anfinogenova Y, Singer HA, Tang DD. Critical role of vimentin phosphorylation at Ser-56 by p21-activated kinase in vimentin cytoskeleton signaling. J Biol Chem 2006; 281:34716-24. [PMID: 16990256 PMCID: PMC1634890 DOI: 10.1074/jbc.m607715200] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphorylation and spatial reorganization of the vimentin network have been implicated in mediating smooth muscle contraction, cell migration, and mitosis. In this study, stimulation of cultured smooth muscle cells with 5-hydroxytryptamine (5-HT) induced PAK1 phosphorylation at Thr-423 (an indication of p21-activated kinase (PAK) activation). Treatment with PAK led to disassembly of wild-type (but not mutant S56A) vimentin filaments as assessed by an in vitro filament assembly assay. Furthermore, stimulation with 5-HT resulted in the dissociation of Crk-associated substrate (CAS; an adapter protein associated with smooth muscle force development) from cytoskeletal vimentin. Expression of mutant S56A vimentin in cells inhibited the increase in phosphorylation at Ser-56 and in the ratios of soluble to insoluble vimentin (an index of vimentin disassembly) and the dissociation of CAS from cytoskeletal vimentin in response to 5-HT activation compared with cells expressing wild-type vimentin. Because CAS may be involved in PAK activation, PAK phosphorylation was evaluated in cells expressing the S56A mutant. Expression of mutant S56A vimentin depressed PAK phosphorylation at Thr-423 induced by 5-HT. Expression of the S56A mutant also inhibited the spatial reorientation of vimentin filaments in cells in response to 5-HT stimulation. Our results suggest that vimentin phosphorylation at Ser-56 may inversely regulate PAK activation possibly via the increase in the amount of soluble CAS upon agonist stimulation of smooth muscle cells. Additionally, vimentin phosphorylation at this position is critical for vimentin filament spatial rearrangement elicited by agonists.
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Affiliation(s)
- Qing-Fen Li
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208
| | - Amy M. Spinelli
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208
| | - Ruping Wang
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208
| | - Yana Anfinogenova
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208
| | - Harold A. Singer
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208
| | - Dale D. Tang
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208
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21
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Abstract
Vimentin intermediate filaments undergo spatial reorganization in cultured smooth muscle cells in response to contractile activation; however, the role of vimentin in the physiological properties of smooth muscle has not been well elucidated. Tracheal smooth muscle strips were loaded with antisense oligonucleotides (ODNs) against vimentin and then cultured for 2 days to allow for protein degradation. Treatment with vimentin antisense, but not sense, ODNs suppressed vimentin protein expression; neither vimentin antisense nor sense ODNs affected protein levels of desmin and actin. Force development in response to ACh stimulation or KCl depolarization was lower in vimentin-deficient tissues than in vimentin sense ODN- or non-ODN-treated muscle strips. Passive tension was also depressed in vimentin-depleted muscle tissues. Vimentin downregulation did not attenuate increases in myosin light chain (MLC) phosphorylation in response to contractile stimulation or basal MLC phosphorylation. In vimentin sense ODN-treated or non-ODN-treated smooth muscle strips, the desmosomal protein plakoglobin was primarily localized in the cell periphery. The membrane-associated localization of plakoglobin was reduced in vimentin-depleted muscle tissues. These studies suggest that vimentin filaments play an important role in mediating active force development and passive tension, which are not regulated by MLC phosphorylation. Vimentin downregulation impairs the structural organization of desmosomes, which may be associated with the decrease in force development.
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Affiliation(s)
| | | | - Dale D. Tang
- Correspondence: Dale D. Tang, Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY 12208, Tel: (518)-262-6416; Fax: (518)-262-8101, E-mail:
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22
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Abstract
Fluid shear stress caused by blood flow is a major determinant of vascular remodeling and arterial tone and can lead to development of atherosclerosis. The endothelial monolayer in vivo acts as a signal transduction interface for hemodynamic forces; these forces determine the shape, cytoskeletal organization, and function of endothelial cells, allowing the vessels to cope with physiological or pathological conditions. The Ras superfamily of GTPases have been revealed to be master regulators of many cellular activities. In particular, the GTPases RhoA, Rac1, and Cdc42 are known to regulate cell shape changes through effects on the cytoskeleton, but their ability to influence polarity, microtubule dynamics, and transcription factor activity is just as significant. Shear stress modulates the activity of small GTPases, which are critical for both cytoskeletal reorganization and changes in gene expression in response to shear stress. The goal of this article is to review what is known about Ras and more so about Rho GTPases in mechanotransduction and the responses of cells to fluid flow. Several distinct signaling pathways can be coordinately activated by flow, and small GTPases are strongly implicated in some of them; thus possible connections will be explored and a unifying hypothesis offered.
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Affiliation(s)
- Eleni Tzima
- Department of Cell and Molecular Physiology, Carolina Cardiovascular Biology Center, University of North Carolina, Chapel Hill, NC 27599, USA.
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23
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Tang DD, Bai Y, Gunst SJ. Silencing of p21-activated kinase attenuates vimentin phosphorylation on Ser-56 and reorientation of the vimentin network during stimulation of smooth muscle cells by 5-hydroxytryptamine. Biochem J 2005; 388:773-83. [PMID: 15766329 PMCID: PMC1183456 DOI: 10.1042/bj20050065] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Vimentin intermediate filaments undergo spatial reorganization in endothelial cells and fibroblasts in response to stimulation with platelet-derived growth factor and epidermal growth factor. In the present study, the vimentin network exhibited a curved filamentous structure in unstimulated smooth muscle cells. Vimentin filaments became straight and were arranged along the long axis of cells upon stimulation with 5-hydroxytryptamine (5-HT; serotonin). Stimulation of smooth muscle cells with 5-HT also induced phosphorylation of vimentin on Ser-56. Treatment of cells with small interfering RNA selectively down-regulated the expression of PAK1 (p21-activated kinase 1) without affecting the content of smooth muscle alpha-actin. The silencing of PAK1 inhibited the site-specific phosphorylation and spatial rearrangement of the vimentin network in response to stimulation with 5-HT. Neither the disruption of stress fibres by cytochalasin D nor the inhibition of protein tyrosine phosphorylation affects the spatial reorganization of vimentin intermediate filaments in response to stimulation with 5-HT. In addition, stimulation of smooth muscle cells with 5-HT increased the ratio of soluble to insoluble vimentin. PAK1 silencing attenuated increases in the ratio of soluble to insoluble vimentin upon stimulation with 5-HT. These results suggest that the PAK-mediated site-specific phosphorylation of vimentin may play a role in regulating the reorganization of vimentin intermediate filaments during stimulation of smooth muscle cells with 5-HT.
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Affiliation(s)
- Dale D Tang
- Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, ME-424, Albany, NY 12208, USA.
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24
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Soloff RS, Katayama C, Lin MY, Feramisco JR, Hedrick SM. Targeted deletion of protein kinase C lambda reveals a distribution of functions between the two atypical protein kinase C isoforms. J Immunol 2004; 173:3250-60. [PMID: 15322187 DOI: 10.4049/jimmunol.173.5.3250] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Protein kinase C lambda (PKClambda) is an atypical member of the PKC family of serine/threonine kinases with high similarity to the other atypical family member, PKCzeta. This similarity has made it difficult to determine specific roles for the individual atypical isoforms. Both PKClambda and PKCzeta have been implicated in the signal transduction, initiated by mediators of innate immunity, that culminates in the activation of MAPKs and NF-kappaB. In addition, work from invertebrates shows that atypical PKC molecules play a role in embryo development and cell polarity. To determine the unique functions of PKClambda, mice deficient for PKClambda were generated by gene targeting. The ablation of PKClambda results in abnormalities early in gestation with lethality occurring by embryonic day 9. The role of PKClambda in cytokine-mediated cellular activation was studied by making mouse chimeras from PKClambda-deficient embryonic stem cells and C57BL/6 or Rag2-deficient blastocysts. Cell lines derived from these chimeric animals were then used to dissect the role of PKClambda in cytokine responses. Although the mutant cells exhibited alterations in actin stress fibers and focal adhesions, no other phenotypic differences were noted. Contrary to experiments using dominant interfering forms of PKClambda, mutant cells responded normally to TNF, serum, epidermal growth factor, IL-1, and LPS. In addition, no abnormalities were found in T cell development or T cell activation. These data establish that, in vertebrates, the two disparate functions of atypical PKC molecules have been segregated such that PKCzeta mediates signal transduction of the innate immune system and PKClambda is essential for early embryogenesis.
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Affiliation(s)
- Rachel S Soloff
- Division of Biological Sciences, Moores University of California at San Diego Cancer Center, La Jolla 92093, USA
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25
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Abstract
Intermediate filaments, actin-containing microfilaments and microtubules are the three main cytoskeletal systems of vertebrate and many invertebrate cells. Although these systems are composed of distinctly different proteins, they are in constant and intimate communication with one another. Understanding the molecular basis of this cytoskeletal crosstalk is essential for determining the mechanisms that underlie many cell-biological phenomena. Recent studies have revealed that intermediate filaments and their associated proteins are important components in mediating this crosstalk.
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Affiliation(s)
- Lynne Chang
- Feinberg School of Medicine, Northwestern University, Department of Cell and Molecular Biology, 303 East Chicago Avenue, Chicago, Illinois 60611, USA.
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26
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Abstract
The fibrillar collagen I gel induced the formation of numerous dendritic cell-like protrusions (cell spikes) from the cell body, whereas monomeric collagen I induced typical cell spreading with filopodia and lamellipodia in skin fibroblasts. Peripheral, not central stress fibers appeared upon adhesion to fibrillar collagen gel, whereas both types of fibers were evident upon adhesion to monomeric collagen. Microtubules and vimentin filaments were elongated inside stress fibers along the terminal tip of cell spikes. Spike formation was totally inhibited by nocodazole and severely delayed by cytochalasin D. This suggests that cell spike formation is dependent on microtubules rather than on F-actin. We then investigated the intracellular signaling responsible for cytoskeleton organization to identify the key factor that induces cell spike morphology. During cell spike formation, FAK and CAS were activated. More CAS was activated in cells on fibrillar collagen gel than on the monomeric form, whereas FAK was activated to the same level on either. At 90 min of culture, Rac1 was activated in cells on monomeric collagen I, whereas Cdc42, Rac1 and RhoA were activated in cells on fibrillar collagen gel. These results suggest that microtubule organization via CAS and small GTPases is important for the cell spike formation that is involved in collagen gel contraction and in wound retraction in skin.
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Affiliation(s)
- Kaori Sato
- Department of Molecular Biology, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
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