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Hu W, Gao W, Gong Y, Guo P, Li W, Shu X, Lü S, Zeng Z, Zhang Y, Long M. Trail Formation Alleviates Excessive Adhesion and Maintains Efficient Neutrophil Migration. ACS APPLIED MATERIALS & INTERFACES 2023; 15:17577-17591. [PMID: 36976830 DOI: 10.1021/acsami.3c00288] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Migrating neutrophils are found to leave behind subcellular trails in vivo, but the underlying mechanisms remain unclear. Here, an in vitro cell migration test plus an in vivo observation was applied to monitor neutrophil migration on intercellular cell adhesion molecule-1 (ICAM-1) presenting surfaces. Results indicated that migrating neutrophils left behind long-lasting, chemokine-containing trails. Trail formation tended to alleviate excessive cell adhesion enhanced by the trans-binding antibody and maintain efficient cell migration, which was associated with differential instantaneous edge velocity between the cell front and rear. CD11a and CD11b worked differently in inducing trail formation with polarized distributions on the cell body and uropod. Trail release at the cell rear was attributed to membrane ripping, in which β2-integrin was disrupted from the cell membrane through myosin-mediated rear contraction and integrin-cytoskeleton dissociation, potentiating a specialized strategy of integrin loss and cell deadhesion to maintain efficient migration. Moreover, neutrophil trails left on the substrate served as immune forerunners to recruit dendritic cells. These results provided an insight in elucidating the mechanisms of neutrophil trail formation and deciphering the roles of trail formation in efficient neutrophil migration.
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Affiliation(s)
- Wenhui Hu
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Basic Medical Sciences, Guizhou Medical University, Guiyang 550025, P.R. China
| | - Wenbo Gao
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yixin Gong
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pan Guo
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wang Li
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xinyu Shu
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shouqin Lü
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhu Zeng
- School of Basic Medical Sciences, Guizhou Medical University, Guiyang 550025, P.R. China
| | - Yan Zhang
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Mian Long
- Center for Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory) and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
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Chen H, Luo T, He S, Sa G. Regulatory mechanism of oral mucosal rete peg formation. J Mol Histol 2021; 52:859-868. [PMID: 34463917 DOI: 10.1007/s10735-021-10016-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 08/26/2021] [Indexed: 01/17/2023]
Abstract
Rete pegs are finger-like structures that are formed during the development and wound healing process of the skin and oral mucosa, and they provide better mechanical resistance and nutritional supply between the epithelium and dermis. An increasing number of studies have shown that rete pegs have physiological functions, such as resisting bacterial invasion, body fluid loss, and other harmful changes, which indicate that rete pegs are important structures in natural skin and oral mucosa. Although a great deal of progress has been made in scaffold materials and construction methods for tissue-engineered skin and oral mucosa in recent years, construction of the oral mucosa with functional rete pegs remains a major challenge. In this review, we summarized current research on the progress on formation of rete pegs in human oral mucosa as well as its molecular basis and regulatory mechanism, which might provide new ideas for functional construction of tissue-engineered skin and oral mucosa.
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Affiliation(s)
- Heng Chen
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan, 430079, People's Republic of China
| | - Tianhao Luo
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan, 430079, People's Republic of China
| | - Sangang He
- Department of Oral and Maxillofacial Surgery, School & Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan, 430079, Hubei, China.
| | - Guoliang Sa
- Department of Oral and Maxillofacial Surgery, School & Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan, 430079, Hubei, China.
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Cross-Talk between Hemidesmosomes and Focal Adhesions: A Primer for Wound Healing, Blistering Skin Disease, and Skin Aging. J Invest Dermatol 2019; 139:1854-1856. [DOI: 10.1016/j.jid.2019.04.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 04/23/2019] [Accepted: 04/23/2019] [Indexed: 01/17/2023]
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Hemidesmosomes and Focal Adhesions Treadmill as Separate but Linked Entities during Keratinocyte Migration. J Invest Dermatol 2019; 139:1876-1888.e4. [PMID: 30951704 DOI: 10.1016/j.jid.2019.03.1139] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 03/18/2019] [Accepted: 03/19/2019] [Indexed: 01/25/2023]
Abstract
Hemidesmosomes anchor the epidermal keratin filament cytoskeleton to the extracellular matrix. They are crucial for the mechanical integrity of skin. Their role in keratinocyte migration, however, remains unclear. Examining migrating primary human keratinocytes, we find that hemidesmosomes cluster as ordered arrays consisting of multiple chevrons that are flanked by actin-associated focal adhesions. These hemidesmosomal arrays with intercalated focal adhesions extend from the cell rear to the cell front. New hemidesmosomal chevrons form subsequent to focal adhesion assembly at the cell's leading front, whereas chevrons and associated focal adhesions disassemble at the cell rear in reverse order. The bulk of the hemidesmosome-focal adhesion composite, however, remains attached to the substratum during cell translocation. Similar hemidesmosome-focal adhesion patterns emerge on X-shaped fibronectin-coated micropatterns, during cell spreading and in leader cells during collective cell migration. We further find that hemidesmosomes and focal adhesions affect each other's distribution. We propose that both junctions are separate but linked entities, which treadmill coordinately to support efficient directed cell migration and cooperate to coordinate the dynamic interplay between the keratin and actin cytoskeleton.
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Mason DE, Collins JM, Dawahare JH, Nguyen TD, Lin Y, Voytik-Harbin SL, Zorlutuna P, Yoder MC, Boerckel JD. YAP and TAZ limit cytoskeletal and focal adhesion maturation to enable persistent cell motility. J Cell Biol 2019; 218:1369-1389. [PMID: 30737263 PMCID: PMC6446844 DOI: 10.1083/jcb.201806065] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 11/29/2018] [Accepted: 01/11/2019] [Indexed: 12/18/2022] Open
Abstract
The importance of transcription during cell motility is controversial. Mason et al. show that YAP/TAZ-mediated transcription is required to limit cytoskeletal tension generation and permit persistent cell motility. This pathway is defined as a negative feedback loop whereby Rho-ROCK-myosin activate YAP and TAZ, which limit myosin activation through NUAK2 expression. Cell migration initiates by traction generation through reciprocal actomyosin tension and focal adhesion reinforcement, but continued motility requires adaptive cytoskeletal remodeling and adhesion release. Here, we asked whether de novo gene expression contributes to this cytoskeletal feedback. We found that global inhibition of transcription or translation does not impair initial cell polarization or migration initiation, but causes eventual migratory arrest through excessive cytoskeletal tension and over-maturation of focal adhesions, tethering cells to their matrix. The transcriptional coactivators YAP and TAZ mediate this feedback response, modulating cell mechanics by limiting cytoskeletal and focal adhesion maturation to enable persistent cell motility and 3D vasculogenesis. Motile arrest after YAP/TAZ ablation was partially rescued by depletion of the YAP/TAZ-dependent myosin phosphatase regulator, NUAK2, or by inhibition of Rho-ROCK-myosin II. Together, these data establish a transcriptional feedback axis necessary to maintain a responsive cytoskeletal equilibrium and persistent migration.
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Affiliation(s)
- Devon E Mason
- McKay Orthopaedic Research Laboratory, Department of Orthopedic Surgery, University of Pennsylvania, Philadelphia, PA.,Department of Bioengineering, University of Pennsylvania, Philadelphia, PA.,Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN
| | - Joseph M Collins
- McKay Orthopaedic Research Laboratory, Department of Orthopedic Surgery, University of Pennsylvania, Philadelphia, PA.,Department of Bioengineering, University of Pennsylvania, Philadelphia, PA
| | - James H Dawahare
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN
| | - Trung Dung Nguyen
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN.,Department of Engineering and Computer Science, Seattle Pacific University, Seattle, WA
| | - Yang Lin
- Herman B. Wells Center for Pediatric Research, Indiana University, Indianapolis, IN
| | - Sherry L Voytik-Harbin
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN.,Department of Basic Medical Sciences, Purdue University, West Lafayette, IN
| | - Pinar Zorlutuna
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN
| | - Mervin C Yoder
- Herman B. Wells Center for Pediatric Research, Indiana University, Indianapolis, IN
| | - Joel D Boerckel
- McKay Orthopaedic Research Laboratory, Department of Orthopedic Surgery, University of Pennsylvania, Philadelphia, PA .,Department of Bioengineering, University of Pennsylvania, Philadelphia, PA.,Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN
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Afewerki T, Ahmed S, Warren D. Emerging regulators of vascular smooth muscle cell migration. J Muscle Res Cell Motil 2019; 40:185-196. [PMID: 31254136 PMCID: PMC6726670 DOI: 10.1007/s10974-019-09531-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 06/21/2019] [Indexed: 12/30/2022]
Abstract
Vascular smooth muscle cells (VSMCs) are the predominant cell type in the blood vessel wall and normally adopt a quiescent, contractile phenotype. VSMC migration is tightly controlled, however, disease associated changes in the soluble and insoluble environment promote VSMC migration. Classically, studies investigating VSMC migration have described the influence of soluble factors. Emerging data has highlighted the importance of insoluble factors, including extracellular matrix stiffness and porosity. In this review, we will recap on the important signalling pathways that regulate VSMC migration and reflect on the potential importance of emerging regulators of VSMC function.
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Affiliation(s)
- TecLino Afewerki
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
| | - Sultan Ahmed
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
| | - Derek Warren
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ UK
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Castro-Muñozledo F, Meza-Aguilar DG, Domínguez-Castillo R, Hernández-Zequinely V, Sánchez-Guzmán E. Vimentin as a Marker of Early Differentiating, Highly Motile Corneal Epithelial Cells. J Cell Physiol 2016; 232:818-830. [DOI: 10.1002/jcp.25487] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 07/11/2016] [Indexed: 01/03/2023]
Affiliation(s)
- Federico Castro-Muñozledo
- Department of Cell Biology; Centro de Investigación y de Estudios Avanzados del IPN; México City Mexico
| | - Diana G. Meza-Aguilar
- Department of Cell Biology; Centro de Investigación y de Estudios Avanzados del IPN; México City Mexico
| | - Rocío Domínguez-Castillo
- Department of Molecular Biomedicine; Centro de Investigación y de Estudios Avanzados del IPN; México City Mexico
| | | | - Erika Sánchez-Guzmán
- Department of Cell Biology; Centro de Investigación y de Estudios Avanzados del IPN; México City Mexico
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Nono JK, Lutz MB, Brehm K. EmTIP, a T-Cell immunomodulatory protein secreted by the tapeworm Echinococcus multilocularis is important for early metacestode development. PLoS Negl Trop Dis 2014; 8:e2632. [PMID: 24392176 PMCID: PMC3879249 DOI: 10.1371/journal.pntd.0002632] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Accepted: 11/26/2013] [Indexed: 01/05/2023] Open
Abstract
Background Alveolar echinococcosis (AE), caused by the metacestode of the tapeworm Echinococcus multilocularis, is a lethal zoonosis associated with host immunomodulation. T helper cells are instrumental to control the disease in the host. Whereas Th1 cells can restrict parasite proliferation, Th2 immune responses are associated with parasite proliferation. Although the early phase of host colonization by E. multilocularis is dominated by a potentially parasitocidal Th1 immune response, the molecular basis of this response is unknown. Principal Findings We describe EmTIP, an E. multilocularis homologue of the human T-cell immunomodulatory protein, TIP. By immunohistochemistry we show EmTIP localization to the intercellular space within parasite larvae. Immunoprecipitation and Western blot experiments revealed the presence of EmTIP in the excretory/secretory (E/S) products of parasite primary cell cultures, representing the early developing metacestode, but not in those of mature metacestode vesicles. Using an in vitro T-cell stimulation assay, we found that primary cell E/S products promoted interferon (IFN)-γ release by murine CD4+ T-cells, whereas metacestode E/S products did not. IFN-γ release by T-cells exposed to parasite products was abrogated by an anti-EmTIP antibody. When recombinantly expressed, EmTIP promoted IFN-γ release by CD4+ T-cells in vitro. After incubation with anti-EmTIP antibody, primary cells showed an impaired ability to proliferate and to form metacestode vesicles in vitro. Conclusions We provide for the first time a possible explanation for the early Th1 response observed during E. multilocularis infections. Our data indicate that parasite primary cells release a T-cell immunomodulatory protein, EmTIP, capable of promoting IFN-γ release by CD4+ T-cells, which is probably driving or supporting the onset of the early Th1 response during AE. The impairment of primary cell proliferation and the inhibition of metacestode vesicle formation by anti-EmTIP antibodies suggest that this factor fulfills an important role in early E. multilocularis development within the intermediate host. E. multilocularis is a parasitic helminth causing the chronic human disease alveolar echinococcosis. Current disease control measures are very limited resulting in a high case-fatality rate. A transiently dominating Th1 immune response is mounted at the early phase of the infection, potentially limiting parasite proliferation and disease progression. Understanding the molecular basis of this early anti-Echinococcocus Th1 response would provide valuable information to improve disease control. The authors found that EmTIP, a T-cell immunomodulatory protein homologue, is secreted by the parasite early larva and promotes a Th1 response in host cells. Interestingly, EmTIP binding by antibodies impairs the development of the early parasite larva towards the chronic stage. Altogether the authors propose that E. multilocularis utilizes EmTIP for early larval development, but in the process, the factor is released by the parasite larva and influences host T-cells by directing a parasitocidal Th1 immune response. Therefore, the authors recommend EmTIP as a promising lead for future studies on the development of anti-Echinococcus intervention strategies.
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Affiliation(s)
- Justin Komguep Nono
- University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany
| | - Manfred B. Lutz
- University of Würzburg, Institute of Virology and Immunobiology, Würzburg, Germany
| | - Klaus Brehm
- University of Würzburg, Institute for Hygiene and Microbiology, Würzburg, Germany
- * E-mail:
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Yamada M, Mugnai G, Serada S, Yagi Y, Naka T, Sekiguchi K. Substrate-attached materials are enriched with tetraspanins and are analogous to the structures associated with rear-end retraction in migrating cells. Cell Adh Migr 2013; 7:304-14. [PMID: 23676281 PMCID: PMC3711998 DOI: 10.4161/cam.25041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Substrate-attached materials (SAMs) are cellular feet that remain on substrates after the treatment of adherent cells with EGTA. SAMs are thought to contain cell adhesion machineries, but their biochemical properties have not been addressed in detail. To gain insight into the molecular mechanisms operating in cell adhesions, we comprehensively identified the protein components of SAMs by liquid chromatography coupled with tandem mass spectrometry, followed by immunoblot analysis. We found that the tetraspanins CD9, CD81, and CD151 were enriched in SAMs along with other transmembrane proteins that are known to associate with tetraspanins. Notably, integrins were detected in SAMs, but the components of focal adhesions were scarcely detected. These observations are reminiscent of the “footprints” that remain on substrates when the retraction fibers at the rear of migrating cells are released, because such footprints have been reported to contain tetraspanins and integrins but not focal adhesion proteins. In support of this hypothesis, the formation of SAMs was attenuated by inhibitors of ROCK, myosin II and dynamin, all of which are known to participate in rear-end retraction in migrating cells. Furthermore, SAMs left on collagen-coated substrates were found by electron microscopy to be fewer and thinner than those on laminin-coated substrates, reflecting the thin and fragile retraction fibers of cells migrating on collagen. Collectively, these results indicate that SAMs closely resemble the footprints and retraction fibers of migrating cells in their protein components, and that they are yielded by similar mechanisms.
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Affiliation(s)
- Masashi Yamada
- Laboratory of Extracellular Matrix Biochemistry, Institute for Protein Research, Osaka University, Suita, Japan
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Hyun YM, Sumagin R, Sarangi PP, Lomakina E, Overstreet MG, Baker CM, Fowell DJ, Waugh RE, Sarelius IH, Kim M. Uropod elongation is a common final step in leukocyte extravasation through inflamed vessels. ACTA ACUST UNITED AC 2012; 209:1349-62. [PMID: 22711877 PMCID: PMC3405502 DOI: 10.1084/jem.20111426] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Uropod elongation occurs during leukocyte extravasation. The efficient trafficking of immune cells into peripheral nonlymphoid tissues is key to enact their protective functions. Despite considerable advances in our understanding of cell migration in secondary lymphoid organs, real-time leukocyte recruitment into inflamed tissues is not well characterized. The conventional multistep paradigm of leukocyte extravasation depends on CD18 integrin–mediated events such as rapid arrest and crawling on the surface of the endothelium and transmigration through the endothelial layer. Using enhanced three-dimensional detection of fluorescent CD18 fusion proteins in a newly developed knockin mouse, we report that extravasating leukocytes (neutrophils, monocytes, and T cells) show delayed uropod detachment and become extremely elongated before complete transmigration across the endothelium. Additionally, these cells deposit CD18+ microparticles at the subendothelial layer before retracting the stretched uropod. Experiments with knockout mice and blocking antibodies reveal that the uropod elongation and microparticle formation are the result of LFA-1–mediated adhesion and VLA-3–mediated cell migration through the vascular basement membrane. These findings suggest that uropod elongation is a final step in the leukocyte extravasation cascade, which may be important for precise regulation of leukocyte recruitment into inflamed tissues.
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Affiliation(s)
- Young-Min Hyun
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, NY 14642, USA
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Han SJ, Sniadecki NJ. Simulations of the contractile cycle in cell migration using a bio-chemical–mechanical model. Comput Methods Biomech Biomed Engin 2011; 14:459-68. [DOI: 10.1080/10255842.2011.554412] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Sartori A, Gatz R, Beck F, Rigort A, Baumeister W, Plitzko JM. Correlative microscopy: Bridging the gap between fluorescence light microscopy and cryo-electron tomography. J Struct Biol 2007; 160:135-45. [PMID: 17884579 DOI: 10.1016/j.jsb.2007.07.011] [Citation(s) in RCA: 253] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Revised: 07/19/2007] [Accepted: 07/25/2007] [Indexed: 11/17/2022]
Abstract
Cryo-electron tomography of frozen-hydrated biological samples offers a means of studying large and complex cellular structures in three-dimensions and with nanometer-scale resolution. The low contrast of unstained biological material embedded in amorphous ice and the need to minimise the exposure of these radiation-sensitive samples to the electron beam result in a poor signal-to-noise ratio. This poses problems not only in the visualisation and interpretation of such tomograms, it is also a problem in surveying the sample and in finding regions which contain the features of interest and which are suitable for recording tomograms. To address this problem, we have developed a correlative fluorescence light microscopy-electron microscopy approach, which guides the search for the structures of interest and allows electron microscopy to zoom in on them. With our approach, the total dose spent on locating regions of interest is negligible. A newly designed cryo-holder allows imaging of fluorescently labelled samples after vitrification. The absolute coordinates of structures identified and located by cryo-light microscopy are transferred to the electron microscope via a Matlab-based user interface. We have successfully tested the experimental setup and the whole procedure with two types of adherent fluorescently labelled cells, a neuronal cell line and keratinocytes, both grown directly on EM grids.
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Affiliation(s)
- Anna Sartori
- Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany.
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Kirfel G, Rigort A, Borm B, Herzog V. Cell migration: mechanisms of rear detachment and the formation of migration tracks. Eur J Cell Biol 2005; 83:717-24. [PMID: 15679116 DOI: 10.1078/0171-9335-00421] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cell migration is central to many biological and pathological processes, including embryogenesis, tissue repair and regeneration as well as cancer and the inflammatory response. In general, cell migration can be usefully conceptualized as a cyclic process. The initial response of a cell to a migration-promoting agent is to polarize and extend protrusions in the direction of migration. These protrusions can be large, broad lamellipodia or spike-like filopodia, are usually driven by actin polymerization, and are stabilized by adhering to the extracellular matrix (ECM) via transmembrane receptors of the integrin family linked to the actin cytoskeleton. These adhesions serve as traction sites for migration as the cell moves forward over them, and they must be disassembled at the cell rear, allowing it to detach. The mechanisms of rear detachment and the regulatory processes involved are not well understood. The disassembly of adhesions that is required for detachment depends on a coordinated interaction of actin and actin-binding proteins, signaling molecules and effector enzymes including proteases, kinases and phosphatases. Originally, the biochemically regulated processes leading to rear detachment of migrating cells were thought not to be necessarily accompanied by any loss of cell material. However, it has been shown that during rear detachment long tubular extensions, the retracting fibers, are formed and that "membrane ripping" occurs at the cell rear. By this process, a major fraction of integrin-containing cellular material is left behind forming characteristic migration tracks that exactly mark the way a cell has taken.
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Affiliation(s)
- Gregor Kirfel
- Institute of Cell Biology, University of Bonn, Bonn, Germany.
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