1
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Davis-Lunn M, Goult BT, Andrews MR. Clutching at Guidance Cues: The Integrin-FAK Axis Steers Axon Outgrowth. BIOLOGY 2023; 12:954. [PMID: 37508384 PMCID: PMC10376711 DOI: 10.3390/biology12070954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023]
Abstract
Integrin receptors are essential contributors to neurite outgrowth and axon elongation. Activated integrins engage components of the extracellular matrix, enabling the growth cone to form point contacts, which connect the extracellular substrate to dynamic intracellular protein complexes. These adhesion complexes facilitate efficient growth cone migration and neurite extension. Major signalling pathways mediated by the adhesion complex are instigated by focal adhesion kinase (FAK), whilst axonal guidance molecules present in vivo promote growth cone turning or retraction by local modulation of FAK activity. Activation of FAK is marked by phosphorylation following integrin engagement, and this activity is tightly regulated during neurite outgrowth. FAK inhibition slows neurite outgrowth by reducing point contact turnover; however, mutant FAK constructs with enhanced activity stimulate aberrant outgrowth. Importantly, FAK is a major structural component of maturing adhesion sites, which provide the platform for actin polymerisation to drive leading edge advance. In this review, we discuss the coordinated signalling of integrin receptors and FAK, as well as their role in regulating neurite outgrowth and axon elongation. We also discuss the importance of the integrin-FAK axis in vivo, as integrin expression and activation are key determinants of successful axon regeneration following injury.
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Affiliation(s)
- Mathew Davis-Lunn
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Benjamin T Goult
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Melissa R Andrews
- Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO17 1BJ, UK
- Centre for Human Development, Stem Cells and Regeneration, School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
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2
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Hsu KS, Dunleavey JM, Szot C, Yang L, Hilton MB, Morris K, Seaman S, Feng Y, Lutz EM, Koogle R, Tomassoni-Ardori F, Saha S, Zhang XM, Zudaire E, Bajgain P, Rose J, Zhu Z, Dimitrov DS, Cuttitta F, Emenaker NJ, Tessarollo L, St. Croix B. Cancer cell survival depends on collagen uptake into tumor-associated stroma. Nat Commun 2022; 13:7078. [PMID: 36400786 PMCID: PMC9674701 DOI: 10.1038/s41467-022-34643-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 11/01/2022] [Indexed: 11/19/2022] Open
Abstract
Collagen I, the most abundant protein in humans, is ubiquitous in solid tumors where it provides a rich source of exploitable metabolic fuel for cancer cells. While tumor cells were unable to exploit collagen directly, here we show they can usurp metabolic byproducts of collagen-consuming tumor-associated stroma. Using genetically engineered mouse models, we discovered that solid tumor growth depends upon collagen binding and uptake mediated by the TEM8/ANTXR1 cell surface protein in tumor-associated stroma. Tumor-associated stromal cells processed collagen into glutamine, which was then released and internalized by cancer cells. Under chronic nutrient starvation, a condition driven by the high metabolic demand of tumors, cancer cells exploited glutamine to survive, an effect that could be reversed by blocking collagen uptake with TEM8 neutralizing antibodies. These studies reveal that cancer cells exploit collagen-consuming stromal cells for survival, exposing an important vulnerability across solid tumors with implications for developing improved anticancer therapy.
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Affiliation(s)
- Kuo-Sheng Hsu
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - James M. Dunleavey
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Christopher Szot
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Liping Yang
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Mary Beth Hilton
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA ,grid.418021.e0000 0004 0535 8394Basic Research Program, Leidos Biomedical Research Inc., Frederick National Laboratory for Cancer Research (FNLCR), Frederick, MD 21702 USA
| | - Karen Morris
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA ,grid.418021.e0000 0004 0535 8394Basic Research Program, Leidos Biomedical Research Inc., Frederick National Laboratory for Cancer Research (FNLCR), Frederick, MD 21702 USA
| | - Steven Seaman
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Yang Feng
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Emily M. Lutz
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Robert Koogle
- grid.418021.e0000 0004 0535 8394MCGP, NCI, Frederick, MD 21702 USA
| | | | - Saurabh Saha
- BioMed Valley Discoveries, Inc, Kansas City, MO 64111 USA ,Present Address: Centessa Pharmaceuticals, Cambridge, MA 02139 USA
| | - Xiaoyan M. Zhang
- BioMed Valley Discoveries, Inc, Kansas City, MO 64111 USA ,Present Address: Ikena Oncology, Cambridge, MA 02210 USA
| | - Enrique Zudaire
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA ,Present Address: Janssen Pharmaceutical Companies, J&J, R&D, Welsh Road McKean Road, Spring House, PA 19477 USA
| | - Pradip Bajgain
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Joshua Rose
- grid.48336.3a0000 0004 1936 8075Biomolecular Structure Section, Center for Structural Biology, NCI, NIH, Frederick, MD 21702 USA
| | - Zhongyu Zhu
- grid.48336.3a0000 0004 1936 8075Protein Interactions Section, Cancer and Inflammation Program, NCI, NIH, Frederick, MD 21702 USA ,grid.420872.bPresent Address: Lentigen Technology, Inc. 1201 Clopper Road, Gaithersburg, MD 20878 USA
| | - Dimiter S. Dimitrov
- grid.48336.3a0000 0004 1936 8075Protein Interactions Section, Cancer and Inflammation Program, NCI, NIH, Frederick, MD 21702 USA ,grid.21925.3d0000 0004 1936 9000Present Address: Center for Antibody Therapeutics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Frank Cuttitta
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
| | - Nancy J. Emenaker
- grid.48336.3a0000 0004 1936 8075Division of Cancer Prevention, NCI, NIH, Bethesda, MD 20892 USA
| | - Lino Tessarollo
- grid.48336.3a0000 0004 1936 8075Neural Development Section, MCGP, NCI, NIH, Frederick, MD 21702 USA
| | - Brad St. Croix
- grid.48336.3a0000 0004 1936 8075Tumor Angiogenesis Unit, Mouse Cancer Genetics Program (MCGP), National Cancer Institute (NCI), NIH, Frederick, MD 21702 USA
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3
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Pickrum AM, Riegert MO, Wells C, Brockman K, Frank DW. The In Vitro Replication Cycle of Achromobacter xylosoxidans and Identification of Virulence Genes Associated with Cytotoxicity in Macrophages. Microbiol Spectr 2022; 10:e0208322. [PMID: 35856670 PMCID: PMC9430717 DOI: 10.1128/spectrum.02083-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 07/08/2022] [Indexed: 11/28/2022] Open
Abstract
Achromobacter xylosoxidans is an opportunistic pathogen implicated in a wide variety of human infections including the ability to colonize the lungs of cystic fibrosis (CF) patients. The role of A. xylosoxidans in human pathology remains controversial due to the lack of optimized in vitro and in vivo model systems to identify and test bacterial gene products that promote a pathological response. We have previously identified macrophages as a target host cell for A. xylosoxidans-induced cytotoxicity. By optimizing our macrophage infection model, we determined that A. xylosoxidans enters macrophages and can reside within a membrane bound vacuole for extended periods of time. Intracellular replication appears limited with cellular lysis preceding an enhanced, mainly extracellular replication cycle. Using our optimized in vitro model system along with transposon mutagenesis, we identified 163 genes that contribute to macrophage cytotoxicity. From this list, we characterized a giant RTX adhesin encoded downstream of a type one secretion system (T1SS) that mediates bacterial binding and entry into host macrophages, an important first step toward cellular toxicity and inflammation. The RTX adhesin is encoded by other human isolates and is recognized by antibodies present in serum isolated from CF patients colonized by A. xylosoxidans, indicating this virulence factor is produced and deployed in vivo. This study represents the first characterization of A. xylosoxidans replication during infection and identifies a variety of genes that may be linked to virulence and human pathology. IMPORTANCE Patients affected by CF develop chronic bacterial infections characterized by inflammatory exacerbations and tissue damage. Advancements in sequencing technologies have broadened the list of opportunistic pathogens colonizing the CF lung. A. xylosoxidans is increasingly recognized as an opportunistic pathogen in CF, yet our understanding of the bacterium as a contributor to human disease is limited. Genomic studies have identified potential virulence determinants in A. xylosoxidans isolates, but few have been mechanistically studied. Using our optimized in vitro cell model, we identified and characterized a bacterial adhesin that mediates binding and uptake by host macrophages leading to cytotoxicity. A subset of serum samples from CF patients contains antibodies that recognize the RTX adhesion, suggesting, for the first time, that this virulence determinant is produced in vivo. This work furthers our understanding of A. xylosoxidans virulence factors at a mechanistic level.
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Affiliation(s)
- Adam M. Pickrum
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Molly O. Riegert
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Clive Wells
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Kenneth Brockman
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Dara W. Frank
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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4
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Abstract
Integrin activation is essential for creating functional transmembrane receptors capable of inducing downstream cellular effects such as cell migration, cell spreading, neurite outgrowth and axon regeneration. Integrins are bidirectional signalling molecules that mediate their effects by 'inside-out' and 'outside-in' signalling. This review will provide a detailed overview of integrin activation focusing on intracellular activation in neurons and discussing direct implications in the regulation of neurite outgrowth and axon regeneration.
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Affiliation(s)
- Menghon Cheah
- John van Geest Centre for Brain Repair, University of Cambridge, Cambridge CB2 0PY, UK.
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK.
| | - Melissa R Andrews
- Department of Biological Sciences, University of Southampton, Life Sciences Bldg 85, Highfield Campus, Southampton SO17 1BJ, UK.
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5
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Brown KL, Banerjee S, Feigley A, Abe H, Blackwell TS, Pozzi A, Hudson BG, Zent R. Salt-bridge modulates differential calcium-mediated ligand binding to integrin α1- and α2-I domains. Sci Rep 2018; 8:2916. [PMID: 29440721 PMCID: PMC5811549 DOI: 10.1038/s41598-018-21231-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 01/31/2018] [Indexed: 11/11/2022] Open
Abstract
Integrins are transmembrane cell-extracellular matrix adhesion receptors that impact many cellular functions. A subgroup of integrins contain an inserted (I) domain within the α–subunits (αI) that mediate ligand recognition where function is contingent on binding a divalent cation at the metal ion dependent adhesion site (MIDAS). Ca2+ is reported to promote α1I but inhibit α2I ligand binding. We co-crystallized individual I-domains with MIDAS-bound Ca2+ and report structures at 1.4 and 2.15 Å resolution, respectively. Both structures are in the “closed” ligand binding conformation where Ca2+ induces minimal global structural changes. Comparisons with Mg2+-bound structures reveal Mg2+ and Ca2+ bind α1I in a manner sufficient to promote ligand binding. In contrast, Ca2+ is displaced in the α2I domain MIDAS by 1.4 Å relative to Mg2+ and unable to directly coordinate all MIDAS residues. We identified an E152-R192 salt bridge hypothesized to limit the flexibility of the α2I MIDAS, thus, reducing Ca2+ binding. A α2I E152A construct resulted in a 10,000-fold increase in Mg2+ and Ca2+ binding affinity while increasing binding to collagen ligands 20%. These data indicate the E152-R192 salt bridge is a key distinction in the molecular mechanism of differential ion binding of these two I domains.
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Affiliation(s)
- Kyle L Brown
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA. .,Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA. .,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.
| | - Surajit Banerjee
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA.,Northeastern Collaborative Access Team, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Andrew Feigley
- Leadership Alliance, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA
| | - Hanna Abe
- Aspirnaut Summer research program, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA
| | - Timothy S Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Veterans Affairs Hospital, Nashville, TN, 37232, USA
| | - Ambra Pozzi
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Veterans Affairs Hospital, Nashville, TN, 37232, USA
| | - Billy G Hudson
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Aspirnaut Summer research program, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Department of Biochemistry, Vanderbilt University, Nashville, TN, 37232-2372, USA
| | - Roy Zent
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Veterans Affairs Hospital, Nashville, TN, 37232, USA
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6
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Binner M, Bray LJ, Friedrichs J, Freudenberg U, Tsurkan MV, Werner C. Cell-instructive starPEG-heparin-collagen composite matrices. Acta Biomater 2017; 53:70-80. [PMID: 28216298 DOI: 10.1016/j.actbio.2017.01.086] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 12/26/2016] [Accepted: 01/31/2017] [Indexed: 12/15/2022]
Abstract
Polymer hydrogels can be readily modulated with regard to their physical properties and functionalized to recapitulate molecular cues of the extracellular matrix (ECM). However, they remain structurally different from the hierarchical supramolecular assemblies of natural ECM. Accordingly, we herein report a set of hydrogel composite materials made from starPEG-peptide conjugates, maleimide-functionalized heparin and collagen type I that combine semisynthetic and ECM-derived components. Collagen fibrillogenesis was controlled by temperature and collagen concentration to form collagen microstructures which were then homogeneously distributed within the 3D composite matrix during hydrogel formation. The collagen-laden hydrogel materials showed a heterogeneous local variation of the stiffness and adhesion ligand density. Composite gels functionalized with growth factors and cell adhesive peptides (RGDSP) supported the growth of embedded human umbilical cord vein endothelial cells (HUVECs) and induced the alignment of embedded bone marrow-derived human mesenchymal stem cells (MSCs) to the collagen microstructures in vitro. The introduced composite hydrogel material is concluded to faithfully mimic cell-instructive features of the ECM. STATEMENT OF SIGNIFICANCE Cell-instructive materials play an important role in the generation of both regenerative therapies and advanced tissue and disease models. For that purpose, biofunctional polymer hydrogels recapitulating molecular cues of the extracellular matrix (ECM) were successfully applied in various different studies. However, hydrogels generally lack the hierarchical supramolecular structure of natural ECM. We have therefore developed a hydrogel composite material made from starPEG-peptide conjugates, maleimide-functionalized heparin and collagen type I fibrils. The collagen-laden scaffolds showed a heterogeneous local variation in the stiffness of the material. The composite gels were successfully tested in culture experiments with human umbilical cord vein endothelial cells and bone marrow-derived human mesenchymal stem cells. It was concluded that the composite scaffold was able to faithfully mimic important cell-instructive features of the ECM.
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Affiliation(s)
- Marcus Binner
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Budapester Strasse 27, Dresden, Saxony 01069, Germany
| | - Laura J Bray
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Budapester Strasse 27, Dresden, Saxony 01069, Germany; School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, 2 George Street, Brisbane, Queensland 4000, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove, Queensland 4059, Australia
| | - Jens Friedrichs
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Budapester Strasse 27, Dresden, Saxony 01069, Germany
| | - Uwe Freudenberg
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Budapester Strasse 27, Dresden, Saxony 01069, Germany
| | - Mikhail V Tsurkan
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Budapester Strasse 27, Dresden, Saxony 01069, Germany; Technische Universität Dresden, Center for Regenerative Therapies Dresden, Fetscherstrasse 105, Dresden, Saxony 01307, Germany
| | - Carsten Werner
- Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials, Budapester Strasse 27, Dresden, Saxony 01069, Germany; Technische Universität Dresden, Center for Regenerative Therapies Dresden, Fetscherstrasse 105, Dresden, Saxony 01307, Germany.
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Platelet adhesion involves a novel interaction between vimentin and von Willebrand factor under high shear stress. Blood 2014; 123:2715-21. [PMID: 24642750 DOI: 10.1182/blood-2013-10-530428] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The interaction between platelet receptor glycoprotein Ibα and the A1 domain of von Willebrand factor (VWF) mediates tethering/translocation of platelets to sites of vascular injury. Unexpectedly, we observed platelets translocating over A1A2A3 domains protein slower than on A1 domain at high shear stress. This observation suggests an additional interaction between A domains and an adhesive receptor. We investigated vimentin because we have data showing the interaction of vimentin with the A2 domain of VWF. Moreover, vimentin is expressed on the platelet surface. This novel interaction was analyzed by using purified VWF, recombinant proteins, anti-vimentin antibodies, parallel flow chamber adhesion assays, flow cytometry, and vimentin-deficient murine platelets. The active form of VWF bound to vimentin, and the purified A2 domain blocked that binding. The interaction of a gain-of-function A1A2A3 mutant with platelet was reduced using anti-vimentin antibody. Platelet adhesion to wild-type (WT) A1A2A3 protein, collagen, and fibrin(ogen) was inhibited (32-75%) by anti-vimentin antibody under high shear stress. Compared with WT mice, platelets from vimentin-deficient mice had a reduced flow-dependent adhesion to both collagen and purified murine VWF. Last, the vimentin knockout mice had a prolonged tail bleeding time. The results describe that platelet vimentin engages VWF during platelet adhesion under high shear stress.
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Liddington RC. Structural aspects of integrins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 819:111-26. [PMID: 25023171 DOI: 10.1007/978-94-017-9153-3_8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Structural studies on integrins have recently made great strides in recent years. Crystal structures of the complete extracellular fragments of three integrins in open and closed conformations, 6 α-I domains in complex with ligands, and at least 20 intracellular proteins in complex with cytosolic tails have been obtained; and several transmembrane and cytosolic complexes have been determined by NMR. High resolution EM studies complement these atomic resolution techniques by studying the integrin in different activation states. Although we still have only a few experimental examples among integrin family members, the high level of sequence homology between integrins means that reliable models can be built for the other members of the integrin family. These structures make sense of a lot of preceding biochemical, biophysical and mutagenesis studies, and generate many new testable hypotheses of integrin function. This chapter emphasizes new structural insights applicable to all integrins, with an emphasis on those integrins that contain an α-I domain. The structural data reinforce the notion of the integrin as a molecule in dynamic equilibrium at the cell surface, regulated by binding both to extracellular and intracellular ligands.
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Affiliation(s)
- Robert C Liddington
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA, 92037, USA,
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9
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McKleroy W, Lee TH, Atabai K. Always cleave up your mess: targeting collagen degradation to treat tissue fibrosis. Am J Physiol Lung Cell Mol Physiol 2013; 304:L709-21. [PMID: 23564511 PMCID: PMC3680761 DOI: 10.1152/ajplung.00418.2012] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 03/26/2013] [Indexed: 12/23/2022] Open
Abstract
Pulmonary fibrosis is a vexing clinical problem with no proven therapeutic options. In the normal lung there is continuous collagen synthesis and collagen degradation, and these two processes are precisely balanced to maintain normal tissue architecture. With lung injury there is an increase in the rate of both collagen production and collagen degradation. The increase in collagen degradation is critical in preventing the formation of permanent scar tissue each time the lung is exposed to injury. In pulmonary fibrosis, collagen degradation does not keep pace with collagen production, resulting in extracellular accumulation of fibrillar collagen. Collagen degradation occurs through both extracellular and intracellular pathways. The extracellular pathway involves cleavage of collagen fibrils by proteolytic enzyme including the metalloproteinases. The less-well-described intracellular pathway involves binding and uptake of collagen fragments by fibroblasts and macrophages for lysosomal degradation. The relationship between these two pathways and their relevance to the development of fibrosis is complex. Fibrosis in the lung, liver, and skin has been associated with an impaired degradative environment. Much of the current scientific effort in fibrosis is focused on understanding the pathways that regulate increased collagen production. However, recent reports suggest an important role for collagen turnover and degradation in regulating the severity of tissue fibrosis. The objective of this review is to evaluate the roles of the extracellular and intracellular collagen degradation pathways in the development of fibrosis and to examine whether pulmonary fibrosis can be viewed as a disease of impaired matrix degradation rather than a disease of increased matrix production.
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Affiliation(s)
- William McKleroy
- Cardiovascular Research Institute, Lung Biology Center, University of California San Francisco, San Francisco, CA 94158, USA
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10
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11
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Allen DL, Abrahamsson S, Murphy MF, Roberts DJ. Human platelet antigen 1a epitopes are dependent on the cation-regulated conformation of integrin α(IIb)β(3) (GPIIb/IIIa). J Immunol Methods 2011; 375:166-75. [PMID: 22036924 DOI: 10.1016/j.jim.2011.10.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Revised: 09/18/2011] [Accepted: 10/07/2011] [Indexed: 11/17/2022]
Abstract
BACKGROUND The HPA-1a (Leu(33)) polymorphism of platelet integrin αIIbβ3 is the target of alloantibodies in 70-80% cases of neonatal alloimmune thrombocytopenia (NAIT) in Caucasians and reliable detection of these antibodies is essential for appropriate clinical management. However, the ability to detect such antibodies is highly variable between laboratories and, in a number of clinical cases where there is a HPA-1 genotype mismatch between mother and neonate, HPA-1a antibodies are undetectable. Furthermore, some studies have not shown a consistent relationship between maternal anti-HPA-1a level and neonatal platelet count. Since the integrity and conformation of the αIIbβ3 complex are dependent on divalent cations, we investigated whether HPA-1a epitope integrity and/or conformation might be affected by the presence of the cation chelator EDTA in patient samples or in assay buffers, thus providing a possible explanation for the variable sensitivity of current assays. PRINCIPLE FINDINGS Exposure of the αIIbβ3 complex to EDTA resulted in reduced reactivity of three anti-HPA-1a mAbs (B2, 19-7 and 23-15). More significantly, cation chelation adversely affected detection of polyclonal anti-HPA-1a, not only in the platelet immunofluorescence assay, where alloantibody binding was reduced compared to control platelets (mean MFI reduction 44.5%, range 17.3-69.7%, n=4), but also in the commonly used monoclonal antibody specific immobilisation of platelet antigens assay (MAIPA) where both alloantibody and monoclonal capture antibody binding were reduced (mean OD reduction 82.8%, range 68.3-96.6%, n=9). CONCLUSIONS These data show that HPA-1a antibodies recognise epitopes on αIIbβ3 that are sensitive to EDTA treatment and that cation chelation grossly reduces the sensitivity of the MAIPA assay by diminishing not only HPA-1a alloantibody binding but also 'capture' monoclonal antibody binding. These findings may, in part, explain the current variability in antibody measurement and will guide the development of more sensitive tests for anti-integrin antibodies in NAIT and other conditions.
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Affiliation(s)
- David L Allen
- NHS Blood and Transplant, John Radcliffe Hospital, Oxford, UK.
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12
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Satchell KJ. Structure and Function of MARTX Toxins and Other Large Repetitive RTX Proteins. Annu Rev Microbiol 2011; 65:71-90. [DOI: 10.1146/annurev-micro-090110-102943] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Karla J.F. Satchell
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611;
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13
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Metals in proteins: cluster analysis studies. J Mol Model 2010; 17:429-42. [DOI: 10.1007/s00894-010-0733-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 04/23/2010] [Indexed: 01/19/2023]
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14
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Varga-Szabo D, Pleines I, Nieswandt B. Cell Adhesion Mechanisms in Platelets. Arterioscler Thromb Vasc Biol 2008; 28:403-12. [DOI: 10.1161/atvbaha.107.150474] [Citation(s) in RCA: 416] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- David Varga-Szabo
- From the Rudolf Virchow Center (D.V.-S., I.P., B.N.), DFG-Research Center for Experimental Biomedicine and the Institute of Clinical Biochemistry and Pathobiochemistry (B.N.), University of Würzburg, Germany
| | - Irina Pleines
- From the Rudolf Virchow Center (D.V.-S., I.P., B.N.), DFG-Research Center for Experimental Biomedicine and the Institute of Clinical Biochemistry and Pathobiochemistry (B.N.), University of Würzburg, Germany
| | - Bernhard Nieswandt
- From the Rudolf Virchow Center (D.V.-S., I.P., B.N.), DFG-Research Center for Experimental Biomedicine and the Institute of Clinical Biochemistry and Pathobiochemistry (B.N.), University of Würzburg, Germany
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15
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Abstract
Stable platelet adhesion to extracellular matrices and the formation of a hemostatic or pathological thrombus are dependent on integrin alphaIIbbeta3, also known as GPIIb-IIIa. However, maximal platelet responses to vascular injury may involve the participation of other integrins expressed in platelets (alphaVbeta3, alpha2beta1, alpha5beta1, and alpha6beta1). Platelet membrane 'immunoreceptors' contain at least one subunit with an extracellular immunoglobulin superfamily domain and/or an intracellular stimulatory immunoreceptor tyrosine-based activation motif (ITAM) or immunoreceptor tyrosine-based inhibitory motif (ITIM). Platelet ITAM receptors, such as FcgammaRIIA and the GPVI-FcRgamma complex, promote activation of integrins, while ITIM receptors, such as platelet-endothelial cell adhesion molecule-1, may promote their inhibition. This review summarizes the structure and function of platelet integrins and immunoreceptors, the emerging functional relationships between these receptor classes, and the consequences of their interaction for platelet function in hemostasis and thrombosis.
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Affiliation(s)
- Ana Kasirer-Friede
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0726, USA.
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16
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Farndale RW, Slatter DA, Siljander PRM, Jarvis GE. Platelet receptor recognition and cross-talk in collagen-induced activation of platelets. J Thromb Haemost 2007; 5 Suppl 1:220-9. [PMID: 17635730 DOI: 10.1111/j.1538-7836.2007.02521.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Comprehensive mapping of protein-binding sites within human collagen III has allowed the recognition motifs for integrin alpha(2)beta(1) and VWF A3 domain to be identified. Glycoprotein VI-binding sites are understood, although less well defined. This information, together with recent developments in understanding collagen fiber architecture, and crystal structures of the receptor collagen-binding domains, allows a coherent model for the interaction of collagen with the platelet surface to be developed. This complements our understanding of the orchestration of receptor presentation by membrane microdomains, such that the polyvalent collagen surface may stabilize signaling complexes within the heterogeneous receptor composition of the lipid raft. The ensuing interactions lead to the convergence of signals from each of the adhesive receptors, mediated by FcR gamma-chain and/or FcgammaRIIa, leading to concerted and co-operative platelet activation. Each receptor has a shear-dependent role, VWF/GpIb essential at high shear, and alpha(2)beta(1) at low and intermediate shear, whilst GpVI provides core signals that contribute to enhanced integrin affinity, tighter binding to collagen and consequent platelet activation.
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Affiliation(s)
- R W Farndale
- Department of Biochemistry, University of Cambridge, Cambridge, UK.
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17
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Li D, Graham LD. Epidermal secretions of terrestrial flatworms and slugs: Lehmannia valentiana mucus contains matrilin-like proteins. Comp Biochem Physiol B Biochem Mol Biol 2007; 148:231-44. [PMID: 17644381 DOI: 10.1016/j.cbpb.2007.06.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 06/05/2007] [Accepted: 06/05/2007] [Indexed: 11/25/2022]
Abstract
We describe the epidermal mucus of two types of terrestrial invertebrates: free-living flatworms (Tricladida: Terricola), and the slug Lehmannia valentiana (Gastropoda: Pulmonata). Both exhibited similar dry shear strengths (1.4-1.7 MPa). In denaturing gel electrophoresis, the protein fraction of flatworm mucus migrated mainly as a broad band (200-300 kDa). Slug mucus had a higher protein content than flatworm mucus but it contained more carbohydrate than protein, mainly as large heparan sulfate-like glycosaminoglycans. Proteins and glycosaminoglycans were both essential for the mechanical integrity of the slug hydrogel. The protein fraction of slug mucus contained approximately 12 larger proteins (30-300 kDa) and approximately 6 smaller ones (10-28 kDa). Complete cDNA clones were obtained for the slug mucus 40 kDa protein (Sm40; Genbank accession EF634345) and 85 kDa protein (Sm85; Genbank accession EF634346). Both proteins contain EGF-like repeats and von Willebrand A-domains, and therefore resemble vertebrate matrilins. Many of the larger slug mucus proteins appear to contain A-domains, and these may play a role in the unusual rheological properties of gastropod mucus.
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Affiliation(s)
- Dongmei Li
- CSIRO Molecular and Health Technologies, Sydney Laboratory, North Ryde, NSW, Australia
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18
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Zhao H, Waite JH. Proteins in load-bearing junctions: the histidine-rich metal-binding protein of mussel byssus. Biochemistry 2006; 45:14223-31. [PMID: 17115717 PMCID: PMC1892233 DOI: 10.1021/bi061677n] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Building complex load-bearing scaffolds depends on effective ways of joining functionally different biomacromolecules. The junction between collagen fibers and foamlike adhesive plaques in mussel byssus is robust despite the strikingly dissimilar connected structures. mcfp-4, the matrix protein from this junction, and its presecreted form from the foot tissue of Mytilus californianus were isolated and characterized. mcfp-4 has a mass of approximately 93 kDa as determined by MALDI-TOF mass spectrometry. Its composition is dominated by histidine (22 mol %), but levels of lysine, arginine, and aspartate are also significant. A small amount of 3,4-dihydroxyphenyl-l-alanine (2 mol %) can be detected by amino acid analysis and redox cycling assays. The cDNA-deduced sequence of mcfp-4 reveals multiple variants with highly repetitive internal structures, including approximately 36 tandemly repeated His-rich decapeptides (e.g., HVHTHRVLHK) in the N-terminal half and 16 somewhat more degenerate aspartate-rich undecapeptides (e.g., DDHVNDIAQTA) in the C-terminal half. Incubation of a synthetic peptide based on the His-rich decapeptide with Fe3+, Co2+, Ni2+, Zn2+, and Cu2+ indicates that only Cu is strongly bound. MALDI-TOF mass spectrometry of the peptide modified with diethyl pyrocarbonate before and after Cu binding suggests that histidine residues dominate Cu binding. In contrast, the aspartate-rich undecapeptides preferentially bind Ca2+. mcfp-4 is strategically positioned to function as a macromolecular bifunctional linker by using metal ions to couple its own His-rich domains to the His-rich termini of the preCOLs. Ca2+ may mediate coupling of the C-terminus to other calcium-binding plaque proteins.
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Affiliation(s)
- Hua Zhao
- Molecular, Cellular and Developmental Biology Department, University of California, Santa Barbara, California 93106, USA
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19
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Farndale RW. Collagen-induced platelet activation. Blood Cells Mol Dis 2006; 36:162-5. [PMID: 16464621 DOI: 10.1016/j.bcmd.2005.12.016] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Accepted: 12/06/2005] [Indexed: 11/21/2022]
Abstract
Platelet collagen receptors, such as Gp VI, are attractive targets for antithrombotic therapy. In this paper, I discuss the current knowledge regarding collagen-platelet interactions, including the role of platelet receptors, the recognition of collagen by platelets, the effect of the interaction on platelet activation and thrombosis and the effect of collagen structure on the platelet interaction, and highlight the areas in which additional information is required to pursue the goal of antithrombotic therapy, using the collagen-platelet interaction as the site of intervention. Understanding the detail of the receptor recognition motifs within collagen not only may reveal new antithrombotic targets within collagen, but will almost certainly lead to the development of defined reagents that can be used in vitro and ex vivo to explore thrombus formation further.
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20
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Käpylä J, Jäälinoja J, Tulla M, Ylöstalo J, Nissinen L, Viitasalo T, Vehviläinen P, Marjomäki V, Nykvist P, Säämänen AM, Farndale RW, Birk DE, Ala-Kokko L, Heino J. The Fibril-associated Collagen IX Provides a Novel Mechanism for Cell Adhesion to Cartilaginous Matrix. J Biol Chem 2004; 279:51677-87. [PMID: 15383545 DOI: 10.1074/jbc.m409412200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Collagen IX is the prototype fibril-associated collagen with interruptions in triple helix. In human cartilage it covers collagen fibrils, but its putative cellular receptors have been unknown. The reverse transcription-PCR analysis of human fetal tissues suggested that based on their distribution all four collagen receptor integrins, namely alpha1beta1, alpha2beta1, alpha10beta1, and alpha11beta1, are possible receptors for collagen IX. Furthermore primary chondrocytes and chondrosarcoma cells express the four integrins simultaneously. Chondrosarcoma cells, as well as Chinese hamster ovary cells transfected to express alpha1beta1, alpha2beta1, or alpha10beta1 integrin as their only collagen receptor, showed fast attachment and spreading on human recombinant collagen IX indicating that it is an effective cell adhesion protein. To further study the recognition of collagen IX we produced recombinant alphaI domains in Escherichia coli. For each of the four alphaI domains, collagen IX was among the best collagenous ligands, making collagen IX exceptional compared with all other collagen subtypes tested so far. Rotary shadowing electron microscopy images of both alpha1I- and alpha2I-collagen IX complexes unveiled only one binding site located in the COL3 domain close to the kink between it and the COL2 domain. The recognition of collagen IX by alpha2I was considered to represent a novel mechanism for two reasons. First, collagen IX has no GFOGER motif, and the identified binding region lacks any similar sequences. Second, the alpha2I domain mutations D219R and H258V, which both decreased binding to collagen I and GFOGER, had very different effects on its binding to collagen IX. D219R had no effect, and H258V prevented type IX binding. Thus, our results indicate that collagen IX has unique cell adhesion properties when compared with other collagens, and it provides a novel mechanism for cell adhesion to cartilaginous matrix.
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Affiliation(s)
- Jarmo Käpylä
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä FI-40014, Finland
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21
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Cruz MA, Chen J, Whitelock JL, Morales LD, López JA. The platelet glycoprotein Ib-von Willebrand factor interaction activates the collagen receptor alpha2beta1 to bind collagen: activation-dependent conformational change of the alpha2-I domain. Blood 2004; 105:1986-91. [PMID: 15514009 DOI: 10.1182/blood-2004-04-1365] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrin alpha2beta1 (glycoprotein [GP] Ia/IIa) is a major platelet receptor for collagen, containing its collagen-binding site within the alpha2 I domain. alpha2beta1 changes conformation upon platelet activation, increasing its affinity for collagen. We observed that 2 antibodies known to bind within the alpha2I domain, 12F1 and 6F1, bound preferentially to adenosine diphosphate (ADP)-activated platelets. Interestingly, when whole blood was perfused over a surface coated with either 12F1 or 6F1, only 6F1 supported the adhesion of unstimulated platelets. To test whether the interaction of GP Ib with von Willebrand factor (VWF) directly activates alpha2beta1, we used 12F1 as a probe of integrin activation. We perfused blood over a surface coated with a mixture of VWF-A1 domain (a GP Ib ligand) and 12F1 or VWF-A1 and mouse immunoglobulin G (IgG). Platelets rolled and did not attach stably on the A1/IgG surface, but they firmly bound and covered the A1/12F1 surface. We corroborated that 12F1 binds an active conformation of the I domain by showing that it binds with higher affinity to a gain-of-function mutant than to either wild-type I domain or a loss-of-function mutant. These results strongly suggest that the interaction of platelet GP Ib with VWF mediates the activation of alpha2beta1, increasing its affinity for collagen.
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Affiliation(s)
- Miguel A Cruz
- Thrombosis Research Section, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, N1319, Houston, TX 77030, USA.
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22
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Jokinen J, Dadu E, Nykvist P, Käpylä J, White DJ, Ivaska J, Vehviläinen P, Reunanen H, Larjava H, Häkkinen L, Heino J. Integrin-mediated cell adhesion to type I collagen fibrils. J Biol Chem 2004; 279:31956-63. [PMID: 15145957 DOI: 10.1074/jbc.m401409200] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the integrin family, the collagen receptors form a structurally and functionally distinct subgroup. Two members of this subgroup, alpha(1)beta(1) and alpha(2)beta(1) integrins, are known to bind to monomeric form of type I collagen. However, in tissues type I collagen monomers are organized into large fibrils immediately after they are released from cells. Here, we studied collagen fibril recognition by integrins. By an immunoelectron microscopy method we showed that integrin alpha(2)I domain is able to bind to classical D-banded type I collagen fibrils. However, according to the solid phase binding assay, the collagen fibril formation appeared to reduce integrin alpha(1)I and alpha(2)I domain avidity to collagen and to lower the number of putative alphaI domain binding sites on it. Respectively, cellular alpha(1)beta(1) integrin was able to mediate cell spreading significantly better on monomeric than on fibrillar type I collagen matrix, whereas alpha(2)beta(1) integrin appeared still to facilitate both cell spreading on fibrillar type I collagen matrix and also the contraction of fibrillar type I collagen gel. Additionally, alpha(2)beta(1) integrin promoted the integrin-mediated formation of long cellular projections typically induced by fibrillar collagen. Thus, these findings suggest that alpha(2)beta(1) integrin is a functional cellular receptor for type I collagen fibrils, whereas alpha(1)beta(1) integrin may only effectively bind type I collagen monomers. Furthermore, when the effect of soluble alphaI domains on type I collagen fibril formation was tested in vitro, the observations suggest that integrin type collagen receptors might guide or even promote pericellular collagen fibrillogenesis.
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Affiliation(s)
- Johanna Jokinen
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä FI-40014, Finland
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23
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Londrigan SL, Graham KL, Takada Y, Halasz P, Coulson BS. Monkey rotavirus binding to alpha2beta1 integrin requires the alpha2 I domain and is facilitated by the homologous beta1 subunit. J Virol 2003; 77:9486-501. [PMID: 12915563 PMCID: PMC187378 DOI: 10.1128/jvi.77.17.9486-9501.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Rotaviruses utilize integrins during virus-cell interactions that lead to infection. Cell binding and infection by simian rotavirus SA11 were inhibited by antibodies (Abs) to the inserted (I) domain of the alpha2 integrin subunit. To determine directly which integrins or other proteins bind rotaviruses, cell surface proteins precipitated by rotaviruses were compared with those precipitated by anti-alpha2beta1 Abs. Two proteins precipitated by SA11 and rhesus rotavirus RRV from MA104 and Caco-2 cells migrated indistinguishably from alpha2beta1 integrin, and SA11 precipitated beta1 from alpha2beta1-transfected CHO cells. These viruses specifically precipitated two MA104 cell proteins only, but an additional 160- to 165-kDa protein was precipitated by SA11 from Caco-2 cells. The role of the alpha2 I domain in rotavirus binding, infection, and growth was examined using CHO cell lines expressing wild-type or mutated human alpha2 or alpha2beta1. Infectious SA11 and RRV, but not human rotavirus Wa, specifically bound CHO cell-expressed human alpha2beta1 and, to a lesser extent, human alpha2 combined with hamster beta1. Binding was inhibited by anti-alpha2 I domain monoclonal Abs (MAbs), but not by non-I domain MAbs to alpha2, and required the presence of the alpha2 I domain. Amino acid residues 151, 221, and 254 in the metal ion-dependent adhesion site of the alpha2 I domain that are necessary for type I collagen binding to alpha2beta1 were not essential for rotavirus binding. Rotavirus-alpha2beta1 binding led to increased virus infection and RRV growth. SA11 and RRV require the alpha2 I domain for binding to alpha2beta1, and their binding to this integrin is distinguishable from that of collagen.
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Affiliation(s)
- Sarah L Londrigan
- Department of Microbiology and Immunology, The University of Melbourne, Melbourne, Victoria 3010, Australia
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24
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McCleverty CJ, Liddington RC. Engineered allosteric mutants of the integrin alphaMbeta2 I domain: structural and functional studies. Biochem J 2003; 372:121-7. [PMID: 12611591 PMCID: PMC1223386 DOI: 10.1042/bj20021273] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2002] [Revised: 02/27/2003] [Accepted: 03/03/2003] [Indexed: 11/17/2022]
Abstract
The alpha-I domain, found in the alpha-subunit of the leucocyte integrins such as alphaMbeta2 and alphaLbeta2, switches between the open and closed tertiary conformations, reflecting the high- and low-affinity ligand-binding states of the integrin that are required for regulated cell adhesion and migration. In the present study we show, by using point mutations and engineered disulphide bonds, that ligand affinity can be reduced or increased allosterically by altering the equilibrium between the closed and open states. We determined equilibrium constants for the binding of two ligands, fibrinogen and intercellular cell-adhesion molecule 1, to the alphaM-I domain by surface plasmon resonance, and determined crystal structures of a low-affinity mutant. Locking the domain in the open conformation increases affinity by a factor of no greater than 10, consistent with a closely balanced equilibrium between the two conformations in the absence of ligand. This behaviour contrasts with that of the unliganded alphaL-I domain, for which the equilibrium lies strongly in favour of the closed conformation. These results suggest significant differences in the way the parent integrins regulate I domain conformation and hence ligand affinity.
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Affiliation(s)
- Clare J McCleverty
- The Burnham Institute, 10901 North Torrey Pines Rd, La Jolla, CA 92037, U.S.A
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25
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Romijn RA, Westein E, Bouma B, Schiphorst ME, Sixma JJ, Lenting PJ, Huizinga EG. Mapping the collagen-binding site in the von Willebrand factor-A3 domain. J Biol Chem 2003; 278:15035-9. [PMID: 12582178 DOI: 10.1074/jbc.m208977200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The multimeric glycoprotein von Willebrand factor (VWF) mediates platelet adhesion to collagen at sites of vascular damage. The binding site for collagen types I and III is located in the VWF-A3 domain. Recently, we showed that His(1023), located near the edge between the "front" and "bottom" faces of A3, is critical for collagen binding (Romijn, R. A., Bouma, B., Wuyster, W., Gros, P., Kroon, J., Sixma, J. J., and Huizinga, E. G. (2001) J. Biol. Chem. 276, 9985-9991). To map the binding site in detail, we introduced 22 point mutations in the front and bottom faces of A3. The mutants were expressed as multimeric VWF, and binding to collagen type III was evaluated in a solid-state binding assay and by surface plasmon resonance. Mutation of residues Asp(979), Ser(1020), and His(1023) nearly abolished collagen binding, whereas mutation of residues Ile(975), Thr(977), Val(997), and Glu(1001) reduced binding affinity about 10-fold. Together, these residues define a flat and rather hydrophobic collagen-binding site located at the front face of the A3 domain. The collagen-binding site of VWF-A3 is distinctly different from that of the homologous integrin alpha(2) I domain, which has a hydrophilic binding site located at the top face of the domain. Based on the surface characteristics of the collagen-binding site of A3, we propose that it interacts with collagen sequences containing positively charged and hydrophobic residues. Docking of a collagen triple helix on the binding site suggests a range of possible engagements and predicts that at most eight consecutive residues in a collagen triple helix interact with A3.
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Affiliation(s)
- Roland A Romijn
- Thrombosis and Haemostasis Laboratory, Department of Haematology, University Medical Center and Institute of Biomembranes, HP G03.647, P. O. Box 85500, 3508 GA Utrecht, The Netherlands
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26
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Ball S, Bella J, Kielty C, Shuttleworth A. Structural basis of type VI collagen dimer formation. J Biol Chem 2003; 278:15326-32. [PMID: 12473679 DOI: 10.1074/jbc.m209977200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have determined the interactive sites required for dimer formation in type VI collagen. Despite the fact that type VI collagen is a heterotrimer composed of alpha1(VI), alpha2(VI), and alpha3(VI) chains, the formation of dimers is determined principally by interactions of the alpha2(VI) chain. Key components of this interaction are the metal ion-dependent adhesion site (MIDAS) motif of the alpha2C2 A-domain and the GER sequence in the helical domain of another alpha2(VI) chain. Replacement of the alpha2(VI) C2 domain with the alpha3(VI) domain abolished dimer formation, whereas alterations in the alpha2(VI) C1 domain did not disrupt dimer formation. When the helical sequences were investigated, replacement of the alpha2(VI) sequence GSPGERGDQ with the alpha3(VI) sequence GEKGERGDV abolished dimer formation. Mutating the Pro-108 to a Lys-108 in this alpha2(VI) sequence did not influence dimer formation and suggests that, unlike the integrin I-domain/triple-helix interaction, hydroxyproline is not required in collagen VI A-domain/helix interaction. These results demonstrate that the alpha2(VI) chain position in the assembled triple-helical molecule is critical for antiparallel dimer formation and identify the interacting collagenous and MIDAS sequences involved. These interactions underpin the subsequent assembly of type VI collagen.
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Affiliation(s)
- Stephen Ball
- Wellcome Trust Centre for Cell-Matrix Research, University of Manchester, 2.205 Stopford Building, Oxford Road, Manchester M13 9PT, United Kingdom
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27
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Zigrino P, Kamiguti AS, Eble J, Drescher C, Nischt R, Fox JW, Mauch C. The reprolysin jararhagin, a snake venom metalloproteinase, functions as a fibrillar collagen agonist involved in fibroblast cell adhesion and signaling. J Biol Chem 2002; 277:40528-35. [PMID: 12186858 DOI: 10.1074/jbc.m202049200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The integrins alpha(2)beta(1) and alpha(1)beta(1) have been shown to modulate cellular activities of fibroblasts on contact with fibrillar collagen. Previously it has been shown that collagen binding to alpha(2)beta(1) regulates matrix metalloproteinase MMP-1 and membrane-type MT1-MMP expression. Jararhagin is a snake venom metalloproteinase of the Reprolysin family of zinc metalloproteinases, containing a metalloproteinase domain followed by disintegrin-like and cysteine-rich domains. Jararhagin blocks type I collagen-induced platelet aggregation by binding to the alpha(2)beta(1) integrin and inhibiting collagen-mediated intracellular signaling events. Here we present evidence that, in contrast to the observations in platelets, jararhagin binding to the integrin receptor alpha(2)beta(1) in fibroblasts produces collagen-like cell signaling events such as up-regulation of MMP-1 and MT1-MMP. Inactivation of the metalloproteinase domain had no effect on these properties of jararhagin. Thus, in fibroblasts the snake venom metalloproteinase jararhagin functions as a collagen-mimetic substrate that binds to and activates integrins. Given the homology between the metalloproteinase, disintegrin-like and cysteine-rich domains of jararhagin and those of the members of the ADAMs (a disintegrin-like and metalloproteinase) family of proteins, this work demonstrates the potential of the disintegrin-like/cysteine-rich domains in the ADAMs as cellular signaling agents to elicit responses relevant to the biological function of these proteins.
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Affiliation(s)
- Paola Zigrino
- Department of Dermatology, University of Cologne, Cologne 50924, Germany
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28
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Gullberg DE, Lundgren-Akerlund E. Collagen-binding I domain integrins--what do they do? PROGRESS IN HISTOCHEMISTRY AND CYTOCHEMISTRY 2002; 37:3-54. [PMID: 11876085 DOI: 10.1016/s0079-6336(02)80008-0] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Collagens are the most abundant proteins in the mammalian body and it is well recognized that collagens fulfill an important structural role in the extracellular matrix in a number of tissues. Inactivation of the collagen alpha 1(I) gene in mice results in embryonic lethality and collagen mutations in humans cause defects leading to disease. Integrins constitute a major group of receptors for extracellular matrix components, including collagens. Currently four collagen-binding I domain-containing integrins are known, namely alpha 1 beta 1, alpha 2 beta 1, alpha 10 beta 1 and alpha 11 beta 1. Unlike the undisputed role of collagens as structural elements, the biological importance of integrin mediated cell-collagen interactions is far from clear. This is in part due to the limited information available on the most recent additions of the integrin family, alpha 10 beta 1 and alpha 11 beta 1. Future studies using gene inactivation of individual and multiple integrin genes will allow testing of the hypothesis that collagen-binding integrins have redundant functions but will also shed light on their importance in pathological conditions. In this review we will describe what is currently known about the collagen-binding integrins and discuss their biological functions.
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Affiliation(s)
- Donald E Gullberg
- Department of Medical Biochemistry and Microbiology, Biomedical Center, Box 582, Uppsala University, S-75123 Uppsala, Sweden.
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29
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Seow KT, Xiong JP, Arnaout MA, Welge J, Rippmann F, Goodman SL. Divalent cations and the relationship between alphaA and betaA domains in integrins. Biochem Pharmacol 2002; 64:805-12. [PMID: 12213573 DOI: 10.1016/s0006-2952(02)01142-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Integrins contain either one or two von Willebrand factor A-like domains, which are primary ligand and cation binding regions in the molecules. Here we examine the first structure of an A domain of a beta subunit, in alphanubeta3 and compare it to known A domain structures of alpha subunits. Ligand binding to immobilized alphanubeta3 domain is stimulated by Ca2+ rather than inhibited by it. Biochemical, cell biological and structural evidence suggests that the A domain is a major site of ligand interaction in alphanubeta3. The Arg-Gly-Asp based inhibitor cilengitide (EMD 121974) inhibites ligand interaction with transmembrane-truncated alphanubeta3 in the presence of either Ca2+ or Mn2+ ions, and does so with similar kinetics. The alphanubeta3 structure reveals that both the alphaA and betaA domains share common structural cores. But, in contrast to alphaA, the betaA domain has three cation binding sites, that are involved either directly or indirectly in ligand binding. Structural alignment of alphaA and betaA domains reveals additional loops unique only to the betaA domain and much evidence support that that these loops are important for ligand binding specificity and for the interaction between alpha and beta subunits. Since the position of these loops are evolutionary conserved but their primary sequence varies between the various betaA domains, they represents potential targets for dissecting functional diversity among integrins.
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Affiliation(s)
- Kah-Tong Seow
- Department of Bio- and Chemoinformatics, Merck KGaA, Frankfurterstr. 250, Darmstadt, Germany
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30
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Garbarino JE, Gibbons IR. Expression and genomic analysis of midasin, a novel and highly conserved AAA protein distantly related to dynein. BMC Genomics 2002; 3:18. [PMID: 12102729 PMCID: PMC117441 DOI: 10.1186/1471-2164-3-18] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2002] [Accepted: 07/08/2002] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The largest open reading frame in the Saccharomyces genome encodes midasin (MDN1p, YLR106p), an AAA ATPase of 560 kDa that is essential for cell viability. Orthologs of midasin have been identified in the genome projects for Drosophila, Arabidopsis, and Schizosaccharomyces pombe. RESULTS Midasin is present as a single-copy gene encoding a well-conserved protein of approximately 600 kDa in all eukaryotes for which data are available. In humans, the gene maps to 6q15 and encodes a predicted protein of 5596 residues (632 kDa). Sequence alignments of midasin from humans, yeast, Giardia and Encephalitozoon indicate that its domain structure comprises an N-terminal domain (35 kDa), followed by an AAA domain containing six tandem AAA protomers (approximately 30 kDa each), a linker domain (260 kDa), an acidic domain (approximately 70 kDa) containing 35-40% aspartate and glutamate, and a carboxy-terminal M-domain (30 kDa) that possesses MIDAS sequence motifs and is homologous to the I-domain of integrins. Expression of hemagglutamin-tagged midasin in yeast demonstrates a polypeptide of the anticipated size that is localized principally in the nucleus. CONCLUSIONS The highly conserved structure of midasin in eukaryotes, taken in conjunction with its nuclear localization in yeast, suggests that midasin may function as a nuclear chaperone and be involved in the assembly/disassembly of macromolecular complexes in the nucleus. The AAA domain of midasin is evolutionarily related to that of dynein, but it appears to lack a microtubule-binding site.
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Affiliation(s)
- Joan E Garbarino
- Molecular and Cell Biology Department, University of California Berkeley, Berkeley CA 94720-3200, USA
| | - I R Gibbons
- Molecular and Cell Biology Department, University of California Berkeley, Berkeley CA 94720-3200, USA
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Waite JH, Vaccaro E, Sun C, Lucas JM. Elastomeric gradients: a hedge against stress concentration in marine holdfasts? Philos Trans R Soc Lond B Biol Sci 2002; 357:143-53. [PMID: 11911771 PMCID: PMC1692926 DOI: 10.1098/rstb.2001.1025] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The byssal threads of marine mussels are elastomeric fibres with a great capacity for absorbing and dissipating energy. Up to 70% of the total absorbed energy can be dissipated in the byssus. Because byssal threads attach the mussel to hard inert surfaces in its habitat, they must combine the need to be good shock absorbers with appropriate matching of Young's modulus between living tissue and a hard sub-stratum such as stone - stiffnesses that can differ by five orders of magnitude. Recent data suggest that improved modulus matching and decreased stress concentration between different portions of the byssus is achieved by the use of protein gradients. Protein gradients in byssal threads are constructed using natural macromolecular chimeras having a central collagenous domain, variable flanking modules and histidine-rich amino and carboxy termini. Stiff silk-like flanking modules prevail distally, while at the animal end, rubbery modules resembling elastin predominate. In between the two thread ends there is a mix of both module types. The histidine-rich termini provide metal binding/cross-linking sites, while collagen domains may confer self-assembly on all parts of the structure. A graded axial distribution of flanking modules is expected to moderate stress concentration in joined materials having disparate moduli.
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Affiliation(s)
- J Herbert Waite
- Marine Science Institute & Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.
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Curat CA, Eck M, Dervillez X, Vogel WF. Mapping of epitopes in discoidin domain receptor 1 critical for collagen binding. J Biol Chem 2001; 276:45952-8. [PMID: 11598108 DOI: 10.1074/jbc.m104360200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The binding and activation of the discoidin domain receptor 1 by collagen has led to the conclusion that proteins from the extracellular matrix can directly induce receptor tyrosine kinase-mediated signaling cascades. A region in the extracellular domain of DDR1 homologous to the Dictyostelium discoideum protein discoidin-I is also present in the secreted human protein RS1. Mutations in RS1 cause retinoschisis, a genetic disorder characterized by ablation of the retina. By introducing point mutations into the discoidin domain of DDR1 at positions homologous to the retinoschisis mutations, ligand binding epitopes in the discoidin domain of DDR1 were mapped. Surprisingly, some residues only affected receptor phosphorylation, whereas others influenced both collagen-binding and receptor activation. Furthermore, two truncated DDR1 variants, lacking either the discoidin domain or the stalk region between the discoidin and transmembrane domain, were generated. We showed that (i) the discoidin domain was necessary and sufficient for collagen binding, (ii) only the region between discoidin and transmembrane domain was glycosylated, and (iii) the entire extracellular domain was essential for transmembrane signaling. Using these results, we were able to predict key sites in the collagen-binding epitope of DDR1 and to suggest a potential mechanism of signaling.
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Affiliation(s)
- C A Curat
- Laboratory of Extracellular Matrix Signaling and Tumor Invasion, Georg-Speyer-Haus-Institute for Biomedical Research, Johann Wolfgang von Goethe University Frankfurt, Paul-Ehrlich-Strasse 42-44, 60596 Frankfurt, Germany
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Reiner AP, Siscovick DS, Rosendaal FR. Platelet glycoprotein gene polymorphisms and risk of thrombosis: facts and fancies. REVIEWS IN CLINICAL AND EXPERIMENTAL HEMATOLOGY 2001; 5:262-87; discussion 311-2. [PMID: 11703818 DOI: 10.1046/j.1468-0734.2001.00045.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Over the past several years, platelet glycoprotein gene polymorphisms have received increasing attention as possible inherited determinants of prothrombotic tendency. However, their role in genetic susceptibility to thrombotic disease remains controversial. The glycoprotein IIIa Leu33Pro amino acid substitution appears to be associated with a subtle effect on platelet thrombogenicity in vitro, but is not a major risk factor for arterial thrombotic disease among the general population. Evidence suggests that the glycoprotein IIIa Pro33 allele may be associated with increased risk of thrombotic events following coronary re-vascularization and possibly among younger subjects with atherosclerosis. The nucleotide 807T variant of glycoprotein Ia is associated with increased platelet glycoprotein Ia/IIa receptor density, collagen-induced platelet adhesion and an increased risk of early onset myocardial infarction and stroke. Evaluation of the roles of the glycoprotein Ibalpha Thr145Met and variable number of tandem repeat polymorphisms has been complicated by their lack of well-defined effects on platelet adhesive function and the strong linkage disequilibrium between the two sites. Future epidemiologic studies of platelet glycoprotein gene polymorphisms will require larger sample sizes and family based approaches to further elucidate clinically important associations with thrombotic disease, including gene-environment and gene-gene interactions. Other polymorphisms of potential functional significance within genes encoding platelet membrane proteins will undoubtedly be discovered. The challenge will be to integrate advances in platelet biology with molecular and genetic epidemiology to enhance our understanding of the genetic determinants of common, but etiologically complex thrombotic diseases.
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Affiliation(s)
- A P Reiner
- Department of Medicine, University of Washington, Seattle, USA.
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Romijn RA, Bouma B, Wuyster W, Gros P, Kroon J, Sixma JJ, Huizinga EG. Identification of the collagen-binding site of the von Willebrand factor A3-domain. J Biol Chem 2001; 276:9985-91. [PMID: 11098050 DOI: 10.1074/jbc.m006548200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Von Willebrand factor (vWF) is a multimeric glycoprotein that mediates platelet adhesion and thrombus formation at sites of vascular injury. vWF functions as a molecular bridge between collagen and platelet receptor glycoprotein Ib. The major collagen-binding site of vWF is contained within the A3 domain, but its precise location is unknown. To localize the collagen-binding site, we determined the crystal structure of A3 in complex with an Fab fragment of antibody RU5 that inhibits collagen binding. The structure shows that RU5 recognizes a nonlinear epitope consisting of residues 962-966, 981-997, and 1022-1026. Alanine mutants were constructed of residues Arg(963), Glu(987), His(990), Arg(1016), and His(1023), located in or close to the epitope. Mutants were expressed as fully processed multimeric vWF. Mutation of His(1023) abolished collagen binding, whereas mutation of Arg(963) and Arg(1016) reduced collagen binding by 25-35%. These residues are part of loops alpha3beta4 and alpha1beta2 and alpha-helix 3, respectively, and lie near the bottom face of the domain. His(1023) and flanking residues display multiple conformations in available A3-crystal structures, suggesting that binding of A3 to collagen involves an induced-fit mechanism. The collagen-binding site of A3 is located distant from the top face of the domain where collagen-binding sites are found in homologous integrin I domains.
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Affiliation(s)
- R A Romijn
- Thrombosis and Haemostasis Laboratory, Department of Haematology, University Medical Center and Institute of Biomembranes, HP G03.647, P. O. Box 85500, 3508 GA Utrecht, The Netherlands
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Savoia A, Balduini CL, Savino M, Noris P, Del Vecchio M, Perrotta S, Belletti S, Iolascon A. Autosomal dominant macrothrombocytopenia in Italy is most frequently a type of heterozygous Bernard-Soulier syndrome. Blood 2001; 97:1330-5. [PMID: 11222377 DOI: 10.1182/blood.v97.5.1330] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A form of autosomal dominant macrothrombocytopenia is characterized by mild or no clinical symptoms, normal platelet function, and normal megakaryocyte count. Because this condition has so far received little attention, patients are subject to misdiagnosis and inappropriate therapy. To identify the molecular basis of this disease, 12 Italian families were studied by linkage analysis and mutation screening. Flow cytometry evaluations of platelet membrane glycoproteins (GPs) were also performed. Linkage analysis in 2 large families localized the gene to chromosome 17p, in an interval containing an excellent candidate, the GPIbalpha gene. GPIbalpha, together with other proteins, constitutes the plasma von Willebrand factor (vWF) receptor, which is altered in Bernard-Soulier syndrome (BSS). In 6 of 12 families, a heterozygous Ala156Val missense substitution was identified. Platelet membrane GP studies were performed in 10 patients. Eight were distinguished by a reduction of GPs comparable to that found in a BSS heterozygous condition, whereas the other 2, without the Ala156Val mutation, had a normal content of platelet GPs. In conclusion, the current study provides evidence that most (10 of 12) patients with an original diagnosis of autosomal dominant macrothrombocytopenia shared clinical and molecular features with the heterozygous BSS phenotype. The remaining 2 affected subjects represented patients with "true" autosomal dominant macrothrombocytopenia; the GPIb/IX/V complex was normally distributed on the surface of their platelets. Thus, the diagnosis of heterozygous BSS must always be suspected in patients with inherited thrombocytopenia and platelet macrocytosis.
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Affiliation(s)
- A Savoia
- Medical Genetics Service, IRCCS Hospital CSS, Foggia, Italy
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Chernoff EA, Clarke DO, Wallace-Evers JL, Hungate-Muegge LP, Smith RC. The effects of collagen synthesis inhibitory drugs on somitogenesis and myogenin expression in cultured chick and mouse embryos. Tissue Cell 2001; 33:97-110. [PMID: 11292177 DOI: 10.1054/tice.2000.0161] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The role of fibrillar collagen on myogenic differentiation has previously been studied in tissue culture cell lines but has not been studied in situ. We treated cultured chick and mouse embryos with collagen synthesis inhibitors to determine the role of fibrillar collagen on somitogenesis and on myogenic differentiation in vivo. Stage 12 chick embryos and 8.7 dpc mouse embryos were cultured in control medium or a range of concentrations of the collagen synthesis inhibitors ethyl-3,4-dihydroxybenzoate (EDHB) or cis-hydroxy-proline (CHP). Chick embryos were cultured for 24 h and mouse embryos were cultured for 30 h. Both collagen synthesis inhibitors produced a range of somite abnormalities including formation of fewer and irregular somites in both chick and mouse at high drug concentrations, as well as formation of double somites in EDHB-treated chick embryos. Examination of EDHB-treated mouse embryos by scanning electron microscopy demonstrated a dosage-dependent loss of fibrillar collagen and associated extracellular matrix. Expression of myogenin in EDHB-treated mouse embryos, examined by whole-mount in situ hybridization, was suppressed at higher dosage levels. This study suggests that inhibition of fibrillar collagen production and/or loss of fibrillar collagen in the developing avian and mammalian embryo results in abnormal somite formation and perturbed myogenic differentiation.
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Affiliation(s)
- E A Chernoff
- Department of Biology, Indiana University-Purdue University Indianapolis, Indiana 46202-5132, USA.
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Xu Y, Gurusiddappa S, Rich RL, Owens RT, Keene DR, Mayne R, Höök A, Höök M. Multiple binding sites in collagen type I for the integrins alpha1beta1 and alpha2beta1. J Biol Chem 2000; 275:38981-9. [PMID: 10986291 DOI: 10.1074/jbc.m007668200] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrins alpha(1)beta(1) and alpha(2)beta(1) are two major collagen receptors on the surface of eukaryotic cells. Binding to collagen is primarily due to an A-domain near the N terminus of the alpha chains. Previously, we reported that recombinant A-domain of alpha(1)beta(1) (alpha(1)A) had at least two affinity classes of binding sites in type I collagen (Rich, R. L., et al. (1999) J. Biol. Chem. 274, 24906-24913). Here, we compared the binding of the recombinant A-domain of alpha(2)beta(1) (alpha(2)A) to type I collagen with that of alpha(1)A using surface plasmon resonance and showed that alpha(2)A exhibited only one detectable class of binding sites in type I collagen, with a K(D) of approximately 10 microm at approximately 3 binding sites per collagen molecule. We further demonstrated that alpha(1)A and alpha(2)A competed with each other for binding to type I collagen in enzyme-linked immunosorbent assay (ELISA), suggesting that the binding sites in collagen for the two A-domains overlap or are adjacent to each other. By using rotary shadowing, the complexes of alpha(1)A- and alpha(2)A-procollagen were visualized. Morphometric analyses indicated three major binding regions (near the N terminus, in the central part, and near the C terminus) along the type I procollagen molecule for both A-domains. The positions of the respective binding regions for alpha(1)A and alpha(2)A were overlapping with or adjacent to each other, consistent with the ELISA results. Analysis of the sequences of type I collagen revealed that GER or GER-like motifs are present at each of the binding regions, and notably, the central region contains the GFOGER sequence, which was previously identified as a high affinity site for both alpha(1)A and alpha(2)A (Knight, C. G., et al. (2000) J. Biol. Chem. 275, 35-40). Peptides containing GLOGERGRO (peptide I, near the N terminus), GFOGERGVQ (peptide II, central), and GASGERGPO (peptide III, near the C terminus) were synthesized. Peptides I and II effectively inhibited the binding of alpha(1)A and alpha(2)A to type I collagen, while peptide III did so moderately. The N-terminal site in type I collagen has the sequence GLOGER in all three chains. Thus, it seems that peptide I represents a newly discovered native high affinity site for alpha(1)A and alpha(2)A.
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Affiliation(s)
- Y Xu
- Center for Extracellular Matrix Biology, Institute of Biosciences and Technology, Texas A & M University, Houston, Texas 77030, USA
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Cruz MA, Diacovo TG, Emsley J, Liddington R, Handin RI. Mapping the glycoprotein Ib-binding site in the von willebrand factor A1 domain. J Biol Chem 2000; 275:19098-105. [PMID: 10764791 DOI: 10.1074/jbc.m002292200] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The von Willebrand factor (vWF) mediates platelet adhesion to exposed subendothelium at sites of vascular injury. It does this by forming a bridge between subendothelial collagen and the platelet glycoprotein Ib-IX-V complex (GPIb). The GPIb-binding site within vWF has been localized to the vWF-A1 domain. Based on the crystal structure of the vWF-A1 domain (Emsley, J., Cruz, M., Handin, R., and Liddington, R. (1998) J. Biol. Chem. 273, 10396-10401), we introduced point mutations into 16 candidate residues that might form all or part of the GPIb interaction site. We also introduced two mutations previously reported to impair vWF function yielding a total of 18 mutations. The recombinant vWF-A1 mutant proteins were then expressed in Escherichia coli, and the activity of the purified proteins was assessed by their ability to support flow-dependent platelet adhesion and their ability to inhibit ristocetin-induced platelet agglutination. Six mutations located on the front and upper anterior face of the folded vWF-A1 domain, R524S, G561S, H563T, T594S/E596A, Q604R, and S607R, showed reduced activity in all the assays, and we suggest that these residues form part of the GPIb interaction site. One mutation, G561S, with impaired activity occurs in the naturally occurring variant form of von Willebrand's disease-type 2M underscoring the physiologic relevance of the mutations described here.
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Affiliation(s)
- M A Cruz
- Hematology Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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Emsley J, Knight CG, Farndale RW, Barnes MJ, Liddington RC. Structural basis of collagen recognition by integrin alpha2beta1. Cell 2000; 101:47-56. [PMID: 10778855 DOI: 10.1016/s0092-8674(00)80622-4] [Citation(s) in RCA: 744] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We have determined the crystal structure of a complex between the I domain of integrin alpha2beta1 and a triple helical collagen peptide containing a critical GFOGER motif. Three loops on the upper surface of the I domain that coordinate a metal ion also engage the collagen, with a collagen glutamate completing the coordination sphere of the metal. Comparison with the unliganded I domain reveals a change in metal coordination linked to a reorganization of the upper surface that together create a complementary surface for binding collagen. Conformational changes propagate from the upper surface to the opposite pole of the domain, suggesting both a basis for affinity regulation and a pathway for signal transduction. The structural features observed here may represent a general mechanism for integrin-ligand recognition.
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Affiliation(s)
- J Emsley
- Department of Biochemistry, University of Leicester, United Kingdom
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