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Sawyer TK, Aral E, Staros JV, Bobst CE, Garman SC. Human Saposin B Ligand Binding and Presentation to α-Galactosidase A. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.04.584535. [PMID: 38617236 PMCID: PMC11014568 DOI: 10.1101/2024.04.04.584535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Sphingolipid activator protein B (saposin B; SapB) is an essential activator of globotriaosylceramide (Gb3) catabolism by α-galactosidase A. However, the manner by which SapB stimulates α-galactosidase A activity remains unknown. To uncover the molecular mechanism of SapB presenting Gb3 to α-galactosidase A, we subjected the fluorescent substrate globotriaosylceramide-nitrobenzoxidazole (Gb3-NBD) to a series of biochemical and structural assays involving SapB. First, we showed that SapB stably binds Gb3-NBD using a fluorescence equilibrium binding assay, isolates Gb3-NBD from micelles, and facilitates α-galactosidase A cleavage of Gb3-NBD in vitro. Second, we crystallized SapB in the presence of Gb3-NBD and validated the ligand-bound assembly. Third, we captured transient interactions between SapB and α-galactosidase A by chemical cross-linking. Finally, we determined the crystal structure of SapB bound to α-galactosidase A. These findings establish general principles for molecular recognition in saposin:hydrolase complexes and highlight the utility of NBD reporter lipids in saposin biochemistry and structural biology.
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Affiliation(s)
- Thomas K Sawyer
- Department of Biochemistry & Molecular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
- Program in Molecular & Cellular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Efecan Aral
- Department of Biochemistry & Molecular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
- Program in Molecular & Cellular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - James V Staros
- Department of Biochemistry & Molecular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Cedric E Bobst
- Mass Spectrometry Core Facility, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Scott C Garman
- Department of Biochemistry & Molecular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
- Program in Molecular & Cellular Biology, Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
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2
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Vasconcelos AA, Estrada JC, Caruso IP, Kurtenbach E, Zingali RB, Almeida FCL. Toward the mechanism of jarastatin (rJast) inhibition of the integrin αVβ3. Int J Biol Macromol 2024; 255:128078. [PMID: 37972836 DOI: 10.1016/j.ijbiomac.2023.128078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 11/04/2023] [Accepted: 11/12/2023] [Indexed: 11/19/2023]
Abstract
Disintegrins are a family of cysteine-rich small proteins that were first identified in snake venom. The high divergence of disintegrins gave rise to a plethora of functions, all related to the interaction with integrins. Disintegrins evolved to interact selectively with different integrins, eliciting many physiological outcomes and being promising candidates for the therapy of many pathologies. We used NMR to determine the structure and dynamics of the recombinant disintegrin jarastatin (rJast) and its interaction with the cancer-related integrin αVβ3. rJast displayed the canonical fold of a medium-sized disintegrin and showed complex dynamic in multiple timescales. We used NMR experiments to map the interaction of rJast with αVβ3, and molecular docking followed by molecular dynamics (MD) simulation to describe the first structural model of a disintegrin/integrin complex. We showed that not only the RGD loop participates in the interaction, but also the N-terminal domain. rJast plasticity was essential for the interaction with αVβ3 and correlated with the main modes of motion depicted in the MD trajectories. In summary, our study provides novel structural insights that enhance our comprehension of the mechanisms underlying disintegrin functionality.
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Affiliation(s)
- Ariana A Vasconcelos
- Laboratório de RMN de Biomoléculas, Instituto de Bioquímica Médica Leopoldo de Meis (IBqM), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Centro Nacional de Ressonância Magnética Nuclear (CNRMN), Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jorge C Estrada
- Laboratório de Hemostase e Venenos, Instituto de Bioquímica Médica Leopoldo de Meis (IBqM), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Icaro P Caruso
- Multiuser Center for Biomolecular Innovation (CMIB), Department of Physics, São Paulo State University (UNESP), São Jose do Rio Preto, São Paulo, Brazil
| | - Eleonora Kurtenbach
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Russolina B Zingali
- Laboratório de Hemostase e Venenos, Instituto de Bioquímica Médica Leopoldo de Meis (IBqM), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
| | - Fabio C L Almeida
- Laboratório de RMN de Biomoléculas, Instituto de Bioquímica Médica Leopoldo de Meis (IBqM), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Centro Nacional de Ressonância Magnética Nuclear (CNRMN), Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
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3
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Pitchai MS, Ipe DS, Hamlet S. The Effect of Titanium Surface Topography on Adherent Macrophage Integrin and Cytokine Expression. J Funct Biomater 2023; 14:jfb14040211. [PMID: 37103301 PMCID: PMC10145888 DOI: 10.3390/jfb14040211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/28/2023] Open
Abstract
Immunomodulatory biomaterials have the potential to stimulate an immune response able to promote constructive and functional tissue remodeling, as opposed to persistent inflammation and scar tissue formation. This study examined the effects of titanium surface modification on integrin expression and concurrent cytokine secretion by adherent macrophages in vitro in an attempt to delineate the molecular events involved in biomaterial-mediated immunomodulation. Non-polarised (M0) and inflammatory polarised (M1) macrophages were cultured on a relatively smooth (machined) titanium surface and two proprietary modified rough titanium surfaces (blasted and fluoride-modified) for 24 h. The physiochemical characteristics of the titanium surfaces were assessed by microscopy and profilometry, while macrophage integrin expression and cytokine secretion were determined using PCR and ELISA, respectively. After 24 h adhesion onto titanium, integrin α1 expression was downregulated in both M0 and M1 cells on all titanium surfaces. Expression of integrins α2, αM, β1 and β2 increased in M0 cells cultured on the machined surface only, whereas in M1 cells, expression of integrins α2, αM and β1 all increased with culture on both the machined and rough titanium surfaces. These results correlated with a cytokine secretory response whereby levels of IL-1β, IL-31 and TNF-α increased significantly in M1 cells cultured on the titanium surfaces. These results show that adherent inflammatory macrophages interact with titanium in a surface-dependent manner such that increased levels of inflammatory cytokines IL-1β, TNF-α and IL-31 secreted by M1 cells were associated with higher expression of integrins α2, αM and β1.
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Affiliation(s)
- Manju Sofia Pitchai
- School of Medicine and Dentistry, Gold Coast Campus, Griffith University, Southport, QLD 4222, Australia
| | - Deepak Samuel Ipe
- School of Medicine and Dentistry, Gold Coast Campus, Griffith University, Southport, QLD 4222, Australia
| | - Stephen Hamlet
- School of Medicine and Dentistry, Gold Coast Campus, Griffith University, Southport, QLD 4222, Australia
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4
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Pang X, He X, Qiu Z, Zhang H, Xie R, Liu Z, Gu Y, Zhao N, Xiang Q, Cui Y. Targeting integrin pathways: mechanisms and advances in therapy. Signal Transduct Target Ther 2023; 8:1. [PMID: 36588107 PMCID: PMC9805914 DOI: 10.1038/s41392-022-01259-6] [Citation(s) in RCA: 86] [Impact Index Per Article: 86.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/14/2022] [Accepted: 11/21/2022] [Indexed: 01/03/2023] Open
Abstract
Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.
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Affiliation(s)
- Xiaocong Pang
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Xu He
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Zhiwei Qiu
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Hanxu Zhang
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Ran Xie
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Zhiyan Liu
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Yanlun Gu
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Nan Zhao
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Qian Xiang
- Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034, Beijing, China. .,Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191, Beijing, China.
| | - Yimin Cui
- Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034, Beijing, China. .,Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191, Beijing, China.
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5
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Integrin Regulators in Neutrophils. Cells 2022; 11:cells11132025. [PMID: 35805108 PMCID: PMC9266208 DOI: 10.3390/cells11132025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 02/01/2023] Open
Abstract
Neutrophils are the most abundant leukocytes in humans and are critical for innate immunity and inflammation. Integrins are critical for neutrophil functions, especially for their recruitment to sites of inflammation or infections. Integrin conformational changes during activation have been heavily investigated but are still not fully understood. Many regulators, such as talin, Rap1-interacting adaptor molecule (RIAM), Rap1, and kindlin, are critical for integrin activation and might be potential targets for integrin-regulating drugs in treating inflammatory diseases. In this review, we outline integrin activation regulators in neutrophils with a focus on the above critical regulators, as well as newly discovered modulators that are involved in integrin activation.
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6
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LFA1 Activation: Insights from a Single-Molecule Approach. Cells 2022; 11:cells11111751. [PMID: 35681446 PMCID: PMC9179313 DOI: 10.3390/cells11111751] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 02/04/2023] Open
Abstract
Integrin LFA1 is a cell adhesion receptor expressed exclusively in leukocytes, and plays crucial roles in lymphocyte trafficking, antigen recognition, and effector functions. Since the discovery that the adhesiveness of LFA1 can be dynamically changed upon stimulation, one challenge has been understanding how integrins are regulated by inside-out signaling coupled with macromolecular conformational changes, as well as ligand bindings that transduce signals from the extracellular domain to the cytoplasm in outside-in signaling. The small GTPase Rap1 and integrin adaptor proteins talin1 and kindlin-3 have been recognized as critical molecules for integrin activation. However, their cooperative regulation of integrin adhesiveness in lymphocytes requires further research. Recent advances in single-molecule imaging techniques have revealed dynamic molecular processes in real-time and provided insight into integrin activation in cellular environments. This review summarizes integrin regulation and discusses new findings regarding the bidirectionality of LFA1 activation and signaling processes in lymphocytes.
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7
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Cappenberg A, Kardell M, Zarbock A. Selectin-Mediated Signaling-Shedding Light on the Regulation of Integrin Activity in Neutrophils. Cells 2022; 11:cells11081310. [PMID: 35455989 PMCID: PMC9025114 DOI: 10.3390/cells11081310] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/08/2022] [Accepted: 04/12/2022] [Indexed: 02/04/2023] Open
Abstract
As a consequence of tissue injury or infection, neutrophils are recruited in a stepwise recruitment process from the bloodstream into the surrounding tissue. Selectins are a family of adhesion molecules comprised of L-, E-, and P-selectin. Differences in expression patterns, protein structure, and ligand binding characteristics mediate distinct functions of each selectin. Interactions of selectins and their counter-receptors mediate the first contact of neutrophils with the endothelium, as well as subsequent neutrophil rolling along the endothelial surface. For efficient neutrophil recruitment, activation of β2-integrins on the cell surface is essential. Integrin activation can be elicited via selectin- as well as chemokine-mediated inside-out signaling resulting in integrin conformational changes and clustering. Dysregulation of selectin-induced integrin activation on neutrophils is involved in the development of severe pathological disease conditions including leukocyte adhesion deficiency (LAD) syndromes in humans. Here, we review molecular mechanisms involved in selectin-mediated signaling pathways in neutrophils and their impact on integrin activation, neutrophil recruitment, and inflammatory diseases.
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8
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Sun H, Hu L, Fan Z. β2 integrin activation and signal transduction in leukocyte recruitment. Am J Physiol Cell Physiol 2021; 321:C308-C316. [PMID: 34133240 DOI: 10.1152/ajpcell.00560.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Leukocyte recruitment is a critical step in the pathogenesis of inflammatory and immunological responses. Cell adhesion molecules (CAMs) are involved in controlling cell movements and the recruitment process, and the integrin family of CAMs plays a key role. During cell movement, integrin function is dynamically and precisely regulated. However, this balance might be broken under pathological conditions. Thus, the functional regulation and molecular mechanisms of integrins related to diseases are often a focus of research. Integrin β2 is one of the most commonly expressed integrins in leukocytes that mediate leukocyte adhesion and migration, and it plays an important role in immune responses and inflammation. In this review, we focus on specific functions of integrin β2 in leukocyte recruitment, the conformational changes and signal transduction of integrin β2 activation, the similarities between murine and human factors, and how new insights into these processes can inform future therapies for inflammation and immune diseases.
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Affiliation(s)
- Hao Sun
- Department of Medicine, University of California San Diego, La Jolla, California
| | - Liang Hu
- Cardiovascular Institute of Zhengzhou University, Department of Cardiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China
| | - Zhichao Fan
- Department of Immunology, School of Medicine, UConn Health, Farmington, Connecticut
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9
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Bonus M, Häussinger D, Gohlke H. Liver cell hydration and integrin signaling. Biol Chem 2021; 402:1033-1045. [PMID: 33915604 DOI: 10.1515/hsz-2021-0193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 04/12/2021] [Indexed: 12/21/2022]
Abstract
Liver cell hydration (cell volume) is dynamic and can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such volume changes were identified as a novel and important modulator of cell function. It provides an early example for the interaction between a physical parameter (cell volume) on the one hand and metabolism, transport, and gene expression on the other. Such events involve mechanotransduction (osmosensing) which triggers signaling cascades towards liver function (osmosignaling). This article reviews our own work on this topic with emphasis on the role of β1 integrins as (osmo-)mechanosensors in the liver, but also on their role in bile acid signaling.
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Affiliation(s)
- Michele Bonus
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
| | - Dieter Häussinger
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Wilhelm-Johnen-Str., D-52428 Jülich, Germany
- Institute of Biological Information Processing (IBI-7: Structural Biochemistry), and Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., D-52428 Jülich, Germany
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10
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Large magnitude of force leads to NO-mediated cell shrinkage in single osteocytes implying an initial apoptotic response. J Biomech 2021; 117:110245. [PMID: 33493709 DOI: 10.1016/j.jbiomech.2021.110245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 11/06/2020] [Accepted: 01/03/2021] [Indexed: 11/22/2022]
Abstract
Damage accumulation in the bone under continuous daily loading causes local mechanical overloading known to induce osteocyte apoptosis, which promotes bone resorption to repair bone damage. However, only a few studies have investigated the mechanism of apoptosis in mechanically overloaded osteocytes. As mechanically stimulated osteocytes produce nitric oxide (NO), which triggers apoptosis in various cell types, we aimed to elucidate the mechanism underlying apoptosis in mechanically overloaded osteocytes, focusing on intracellular NO. To investigate the effects of force magnitude on apoptosis and intracellular NO production, we isolated osteocytes from DMP1-EGFP mice and subjected them to quantitative local forces via fibronectin-coated micro beads targeting integrin on the cell surface using a magnetic tweezer. Cell shrinkage was microscopically examined, and intracellular NO production was visualized using DAR-4 M. Mechanical stimulation revealed relationships between force magnitude, apoptosis, and intracellular NO production. The application of a smaller force resulted in no significant cell shrinkage or intracellular NO production; however, a larger force caused a rapid increase in intracellular NO production followed by cell shrinkage. Besides, intracellular NOS (NO synthase) inhibition and NO donation revealed the pro-apoptotic roles of NO in osteocytes. L-NAME (NOS inhibitor)-treated cells displayed no significant shrinkage under a larger force, whereas SNP (NO donor)-treated cells showed cell shrinkage and Annexin V fluorescence, indicating apoptosis. Collectively, our study demonstrates that larger force leads to NO production-mediated osteocyte shrinkage, implying an initial apoptotic response and highlighting the importance of NO production in bone damage.
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11
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Wirth F, Lubosch A, Hamelmann S, Nakchbandi IA. Fibronectin and Its Receptors in Hematopoiesis. Cells 2020; 9:cells9122717. [PMID: 33353083 PMCID: PMC7765895 DOI: 10.3390/cells9122717] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/08/2020] [Accepted: 12/15/2020] [Indexed: 02/07/2023] Open
Abstract
Fibronectin is a ubiquitous extracellular matrix protein that is produced by many cell types in the bone marrow and distributed throughout it. Cells of the stem cell niche produce the various isoforms of this protein. Fibronectin not only provides the cells a scaffold to bind to, but it also modulates their behavior by binding to receptors on the adjacent hematopoietic stem cells and stromal cells. These receptors, which include integrins such as α4β1, α9β1, α4β7, α5β1, αvβ3, Toll-like receptor-4 (TLR-4), and CD44, are found on the hematopoietic stem cell. Because the knockout of fibronectin is lethal during embryonal development and because fibronectin is produced by almost all cell types in mammals, the study of its role in hematopoiesis is difficult. Nevertheless, strong and direct evidence exists for its stimulation of myelopoiesis and thrombopoiesis using in vivo models. Other reviewed effects can be deduced from the study of fibronectin receptors, which showed their activation modifies the behavior of hematopoietic stem cells. Erythropoiesis was only stimulated under hemolytic stress, and mostly late stages of lymphocytic differentiation were modulated. Because fibronectin is ubiquitously expressed, these interactions in health and disease need to be taken into account whenever any molecule is evaluated in hematopoiesis.
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Affiliation(s)
- Franziska Wirth
- Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany; (F.W.); (A.L.); (S.H.)
| | - Alexander Lubosch
- Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany; (F.W.); (A.L.); (S.H.)
| | - Stefan Hamelmann
- Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany; (F.W.); (A.L.); (S.H.)
| | - Inaam A. Nakchbandi
- Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany; (F.W.); (A.L.); (S.H.)
- Max-Planck Institute for Medical Research, 69120 Heidelberg, Germany
- Correspondence: ; Tel.: +49-622-156-8744
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12
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Lietha D, Izard T. Roles of Membrane Domains in Integrin-Mediated Cell Adhesion. Int J Mol Sci 2020; 21:ijms21155531. [PMID: 32752284 PMCID: PMC7432473 DOI: 10.3390/ijms21155531] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 12/13/2022] Open
Abstract
The composition and organization of the plasma membrane play important functional and regulatory roles in integrin signaling, which direct many physiological and pathological processes, such as development, wound healing, immunity, thrombosis, and cancer metastasis. Membranes are comprised of regions that are thick or thin owing to spontaneous partitioning of long-chain saturated lipids from short-chain polyunsaturated lipids into domains defined as ordered and liquid-disorder domains, respectively. Liquid-ordered domains are typically 100 nm in diameter and sometimes referred to as lipid rafts. We posit that integrin β senses membrane thickness and that mechanical force on the membrane regulates integrin activation through membrane thinning. This review examines what we know about the nature and mechanism of the interaction of integrins with the plasma membrane and its effects on regulating integrins and its binding partners.
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Affiliation(s)
- Daniel Lietha
- Cell Signaling and Adhesion Group, Structural and Chemical Biology, Margarita Salas Center for Biological Research (CIB-CSIC), E-28040 Madrid, Spain;
| | - Tina Izard
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, FL 33458, USA
- Correspondence:
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13
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Abstract
Integrins are heterodimeric cell surface receptors ensuring the mechanical connection between cells and the extracellular matrix. In addition to the anchorage of cells to the extracellular matrix, these receptors have critical functions in intracellular signaling, but are also taking center stage in many physiological and pathological conditions. In this review, we provide some historical, structural, and physiological notes so that the diverse functions of these receptors can be appreciated and put into the context of the emerging field of mechanobiology. We propose that the exciting journey of the exploration of these receptors will continue for at least another new generation of researchers.
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Affiliation(s)
- Michael Bachmann
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
| | - Sampo Kukkurainen
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
| | - Vesa P Hytönen
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
| | - Bernhard Wehrle-Haller
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
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14
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Unique transmembrane domain interactions differentially modulate integrin αvβ3 and αIIbβ3 function. Proc Natl Acad Sci U S A 2019; 116:12295-12300. [PMID: 31160446 DOI: 10.1073/pnas.1904867116] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lateral transmembrane (TM) helix-helix interactions between single-span membrane proteins play an important role in the assembly and signaling of many cell-surface receptors. Often, these helices contain two highly conserved yet distinct interaction motifs, arranged such that the motifs cannot be engaged simultaneously. However, there is sparse experimental evidence that dual-engagement mechanisms play a role in biological signaling. Here, we investigate the function of the two conserved interaction motifs in the TM domain of the integrin β3-subunit. The first motif uses reciprocating "large-large-small" amino acid packing to mediate the interaction of the β3 and αIIb TM domains and maintain the inactive resting conformation of the platelet integrin αIIbβ3. The second motif, S-x3-A-x3-I, is a variant of the classical "G-x3-G" motif. Using site-directed mutagenesis, optical trap-based force spectroscopy, and molecular modeling, we show that S-x3-A-x3-I does not engage αIIb but rather mediates the interaction of the β3 TM domain with the TM domain of the αv-subunit of the integrin αvβ3. Like αIIbβ3, αvβ3 on circulating platelets is inactive, and in the absence of platelet stimulation is unable to interact with components of the subendothelial matrix. However, disrupting any residue in the β3 S-x3-A-x3-I motif by site-directed mutations is sufficient to induce αvβ3 binding to the αvβ3 ligand osteopontin and to the monoclonal antibody WOW-1. Thus, the β3-integrin TM domain is able to engage in two mutually exclusive interactions that produce alternate α-subunit pairing, creating two integrins with distinct biological functions.
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15
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Paladino A, Civera M, Curnis F, Paolillo M, Gennari C, Piarulli U, Corti A, Belvisi L, Colombo G. The Importance of Detail: How Differences in Ligand Structures Determine Distinct Functional Responses in Integrin α
v
β
3. Chemistry 2019; 25:5959-5970. [DOI: 10.1002/chem.201900169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 02/22/2019] [Indexed: 01/09/2023]
Affiliation(s)
- Antonella Paladino
- Istituto di Chimica del Riconoscimento Molecolare CNR via Mario Bianco 9 20131 Milan Italy
| | - Monica Civera
- Dipartimento di ChimicaUniversità degli Studi di Milano via Golgi 19 20133 Milan Italy
| | - Flavio Curnis
- IRCCS Ospedale San Raffaele Via Olgettina 60 20132 Milan Italy
| | - Mayra Paolillo
- Dipartimento di Scienze del FarmacoUniversità degli Studi di Pavia Viale Taramelli 6 27100 Pavia Italy
| | - Cesare Gennari
- Dipartimento di ChimicaUniversità degli Studi di Milano via Golgi 19 20133 Milan Italy
| | - Umberto Piarulli
- Dipartimento di Scienza e Alta TecnologiaUniversità degli Studi dell'Insubria Via Valleggio 11 22100 Como Italy
| | - Angelo Corti
- IRCCS Ospedale San Raffaele Via Olgettina 60 20132 Milan Italy
| | - Laura Belvisi
- Dipartimento di ChimicaUniversità degli Studi di Milano via Golgi 19 20133 Milan Italy
| | - Giorgio Colombo
- Dipartimento di ChimicaUniversità degli Studi di Pavia Viale Taramelli 12 27100 Pavia Italy
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16
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Bidone TC, Polley A, Jin J, Driscoll T, Iwamoto DV, Calderwood DA, Schwartz MA, Voth GA. Coarse-Grained Simulation of Full-Length Integrin Activation. Biophys J 2019; 116:1000-1010. [PMID: 30851876 DOI: 10.1016/j.bpj.2019.02.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 12/25/2018] [Accepted: 02/13/2019] [Indexed: 01/01/2023] Open
Abstract
Integrin conformational dynamics are critical to their receptor and signaling functions in many cellular processes, including spreading, adhesion, and migration. However, assessing integrin conformations is both experimentally and computationally challenging because of limitations in resolution and dynamic sampling. Thus, structural changes that underlie transitions between conformations are largely unknown. Here, focusing on integrin αvβ3, we developed a modified form of the coarse-grained heterogeneous elastic network model (hENM), which allows sampling conformations at the onset of activation by formally separating local fluctuations from global motions. Both local fluctuations and global motions are extracted from all-atom molecular dynamics simulations of the full-length αvβ3 bent integrin conformer, but whereas the former are incorporated in the hENM as effective harmonic interactions between groups of residues, the latter emerge by systematically identifying and treating weak interactions between long-distance domains with flexible and anharmonic connections. The new hENM model allows integrins and single-point mutant integrins to explore various conformational states, including the initiation of separation between α- and β-subunit cytoplasmic regions, headpiece extension, and legs opening.
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Affiliation(s)
- Tamara C Bidone
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois
| | - Anirban Polley
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois
| | - Jaehyeok Jin
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois
| | - Tristan Driscoll
- Yale Cardiovascular Research Center and Department of Internal Medicine (Section of Cardiovascular Medicine), Yale School of Medicine, New Haven, Connecticut
| | | | - David A Calderwood
- Department of Pharmacology, New Haven, Connecticut; Department of Cell Biology, Yale University, New Haven, Connecticut
| | - Martin A Schwartz
- Departments of Cell Biology and Biomedical Engineering, Yale University, New Haven, Connecticut; Yale Cardiovascular Research Center and Department of Internal Medicine (Section of Cardiovascular Medicine), Yale School of Medicine, New Haven, Connecticut
| | - Gregory A Voth
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois.
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17
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18
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Mezzenga R, Mitsi M. The Molecular Dance of Fibronectin: Conformational Flexibility Leads to Functional Versatility. Biomacromolecules 2018; 20:55-72. [PMID: 30403862 DOI: 10.1021/acs.biomac.8b01258] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Fibronectin, a large multimodular protein and one of the major fibrillar components of the extracellular matrix, has been the subject of study for many decades and plays critical roles in embryonic development and tissue homeostasis. Moreover, fibronectin has been implicated in the pathology of many diseases, including cancer, and abnormal depositions of fibronectin have been identified in a number of amyloid and nonamyloid lesions. The ability of fibronectin to carry all these diverse functionalities depends on interactions with a large number of molecules, including adhesive and signaling cell surface receptors, other components of the extracellular matrix, and growth factors and cytokines. The regulation and integration of such large number of interactions depends on the modular architecture of fibronectin, which allows a large number of conformations, exposing or destroying different binding sites. In this Review, we summarize the current knowledge regarding the conformational flexibility of fibronectin, with an emphasis on how it regulates the ability of fibronectin to interact with various signaling molecules and cell-surface receptors and to form supramolecular assemblies and fibrillar structures.
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Affiliation(s)
- Raffaele Mezzenga
- Laboratory of Food and Soft Materials , ETH Zurich , 8092 Zurich , Switzerland
| | - Maria Mitsi
- Laboratory of Food and Soft Materials , ETH Zurich , 8092 Zurich , Switzerland
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19
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Seetharaman S, Etienne-Manneville S. Integrin diversity brings specificity in mechanotransduction. Biol Cell 2018; 110:49-64. [DOI: 10.1111/boc.201700060] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 01/08/2018] [Indexed: 12/29/2022]
Affiliation(s)
- Shailaja Seetharaman
- Institut Pasteur Paris CNRS UMR3691; Cell Polarity; Migration and Cancer Unit; Equipe Labellisée Ligue Contre le Cancer; Paris Cedex 15 France
- Université Paris Descartes, Sorbonne Paris Cité; Paris 75006 France
| | - Sandrine Etienne-Manneville
- Institut Pasteur Paris CNRS UMR3691; Cell Polarity; Migration and Cancer Unit; Equipe Labellisée Ligue Contre le Cancer; Paris Cedex 15 France
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20
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Hanein D, Volkmann N. Conformational Equilibrium of Human Platelet Integrin Investigated by Three-Dimensional Electron Cryo-Microscopy. Subcell Biochem 2018; 87:353-363. [PMID: 29464566 DOI: 10.1007/978-981-10-7757-9_12] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Integrins are bidirectional transmembrane receptors that play central roles in hemostasis and arterial thrombosis. They have been subject to structural studies for many years, in particular using X-ray crystallography, nuclear magnetic resonance spectroscopy, and two-dimensional negative stain electron microscopy. Despite considerable progress, a full consensus on the molecular mechanism of integrin activation is still lacking. Three-dimensional reconstructions of full-length human platelet integrin αIIbβ3 in lipid-bilayer nanodiscs obtained by electron cryo-microscopy and single-particle reconstruction have shed new light on the activation process. These studies show that integrin αIIbβ3 exists in a continuous conformational equilibrium ranging from a compact nodular conformation similar to that obtained in crystal structures to a fully extended state with the leg domains separated. This equilibrium is shifted towards the extended conformation when extracellular ligands, cytosolic activators and lipid-bilayer nanodiscs are added. Addition of cytosolic activators and extracellular ligands in the absense of nanodiscs produces significantly less dramatic shifts, emphasizing the importance of the membrane bilayer in the activation process.
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Affiliation(s)
- Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford-Burnham-Prebys Medical Discovery Institute, San Diego, CA, USA
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford-Burnham-Prebys Medical Discovery Institute, San Diego, CA, USA.
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21
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Schittenhelm L, Hilkens CM, Morrison VL. β 2 Integrins As Regulators of Dendritic Cell, Monocyte, and Macrophage Function. Front Immunol 2017; 8:1866. [PMID: 29326724 PMCID: PMC5742326 DOI: 10.3389/fimmu.2017.01866] [Citation(s) in RCA: 141] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 12/08/2017] [Indexed: 12/24/2022] Open
Abstract
Emerging evidence suggests that the β2 integrin family of adhesion molecules have an important role in suppressing immune activation and inflammation. β2 integrins are important adhesion and signaling molecules that are exclusively expressed on leukocytes. The four β2 integrins (CD11a, CD11b, CD11c, and CD11d paired with the β2 chain CD18) play important roles in regulating three key aspects of immune cell function: recruitment to sites of inflammation; cell-cell contact formation; and downstream effects on cellular signaling. Through these three processes, β2 integrins both contribute to and regulate immune responses. This review explores the pro- and anti-inflammatory effects of β2 integrins in monocytes, macrophages, and dendritic cells and how they influence the outcome of immune responses. We furthermore discuss how imbalances in β2 integrin function can have far-reaching effects on mounting appropriate immune responses, potentially influencing the development and progression of autoimmune and inflammatory diseases. Therapeutic targeting of β2 integrins, therefore, holds enormous potential in exploring treatment options for a variety of inflammatory conditions.
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Affiliation(s)
- Leonie Schittenhelm
- Institute of Infection, Immunity & Inflammation, University of Glasgow, Glasgow, United Kingdom.,Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.,Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence (RACE), Glasgow, United Kingdom
| | - Catharien M Hilkens
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom.,Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence (RACE), Glasgow, United Kingdom
| | - Vicky L Morrison
- Institute of Infection, Immunity & Inflammation, University of Glasgow, Glasgow, United Kingdom.,Arthritis Research UK Rheumatoid Arthritis Pathogenesis Centre of Excellence (RACE), Glasgow, United Kingdom
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22
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Yeh YH(J, Lin CM, Chen TT. Human IGF-I Eb-peptide induces cell attachment and lamellipodia outspread of metastatic breast carcinoma cells (MDA-MB-231). Exp Cell Res 2017; 358:199-208. [DOI: 10.1016/j.yexcr.2017.06.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/18/2017] [Accepted: 06/22/2017] [Indexed: 11/29/2022]
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23
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Kastantin M, Faulón Marruecos D, Grover N, Yu McLoughlin S, Schwartz DK, Kaar JL. Connecting Protein Conformation and Dynamics with Ligand-Receptor Binding Using Three-Color Förster Resonance Energy Transfer Tracking. J Am Chem Soc 2017; 139:9937-9948. [PMID: 28658579 DOI: 10.1021/jacs.7b03978] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Specific binding between biomolecules, i.e., molecular recognition, controls virtually all biological processes including the interactions between cells and biointerfaces, both natural and synthetic. Such binding often relies on the conformation of biomacromolecules, which can be highly heterogeneous and sensitive to environmental perturbations, and therefore difficult to characterize and control. An approach is demonstrated here that directly connects the binding kinetics and stability of the protein receptor integrin αvβ3 to the conformation of the ligand fibronectin (FN), which are believed to control cellular mechanosensing. Specifically, we investigated the influence of surface-adsorbed FN structure and dynamics on αvβ3 binding using high-throughput single-molecule three-color Förster resonance energy transfer (FRET) tracking methods. By controlling FN structure and dynamics through tuning surface chemistry, we found that as the conformational and translational dynamics of FN increased, the rate of binding, particularly to folded FN, and stability of the bound FN-αvβ3 complex decreased significantly. These findings highlight the importance of the conformational plasticity and accessibility of the arginine-glycine-aspartic acid (RGD) binding site in FN, which, in turn, mediates cell signaling in physiological and synthetic environments.
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Affiliation(s)
- Mark Kastantin
- Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado 80309, United States
| | - David Faulón Marruecos
- Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado 80309, United States
| | - Navdeep Grover
- Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado 80309, United States
| | - Sean Yu McLoughlin
- Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado 80309, United States
| | - Daniel K Schwartz
- Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado 80309, United States
| | - Joel L Kaar
- Department of Chemical and Biological Engineering, University of Colorado , Boulder, Colorado 80309, United States
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24
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Tolomelli A, Galletti P, Baiula M, Giacomini D. Can Integrin Agonists Have Cards to Play against Cancer? A Literature Survey of Small Molecules Integrin Activators. Cancers (Basel) 2017; 9:cancers9070078. [PMID: 28678151 PMCID: PMC5532614 DOI: 10.3390/cancers9070078] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 06/30/2017] [Accepted: 07/03/2017] [Indexed: 12/14/2022] Open
Abstract
The ability of integrins to activate and integrate intracellular communication illustrates the potential of these receptors to serve as functional distribution hubs in a bi-directional signal transfer outside-in and inside-out of the cells. Tight regulation of the integrin signaling is paramount for normal physiological functions such as migration, proliferation, and differentiation, and misregulated integrin activity could be associated with several pathological conditions. Because of the important roles of integrins and their ligands in biological development, immune responses, leukocyte traffic, haemostasis, and cancer, their potential as therapeutic tools is now widely recognized. Nowadays extensive efforts have been made to discover and develop small molecule ligands as integrin antagonists, whereas less attention has been payed to agonists. In recent years, it has been recognized that integrin agonists could open up novel opportunities for therapeutics, which gain benefits to increase rather than decrease integrin-dependent adhesion and transductional events. For instance, a significant factor in chemo-resistance in melanoma is a loss of integrin-mediated adhesion; in this case, stimulation of integrin signaling by agonists significantly improved the response to chemotherapy. In this review, we overview results about small molecules which revealed an activating action on some integrins, especially those involved in cancer, and examine from a medicinal chemistry point of view, their structure and behavior.
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Affiliation(s)
- Alessandra Tolomelli
- Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126 Bologna, Italy.
| | - Paola Galletti
- Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126 Bologna, Italy.
| | - Monica Baiula
- Department of Pharmacy and Biotechnology, University of Bologna, Via Irnerio 48, 40126 Bologna, Italy.
| | - Daria Giacomini
- Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126 Bologna, Italy.
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25
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Wang L, Pan D, Yan Q, Song Y. Activation mechanisms of αVβ3 integrin by binding to fibronectin: A computational study. Protein Sci 2017; 26:1124-1137. [PMID: 28340512 PMCID: PMC5441423 DOI: 10.1002/pro.3163] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 03/13/2017] [Accepted: 03/19/2017] [Indexed: 01/29/2023]
Abstract
Integrin αVβ3 plays an important role in regulating cellular activities and in human diseases. Although the structure of αVβ3 has been studied by crystallography and electron microscopy, the detailed activation mechanism of integrin αVβ3 induced by fibronectin remains unclear. In this study, we investigated the conformational and dynamical motion changes of Mn2+ -bound integrin αVβ3 by binding to fibronectin with molecular dynamics simulations. Results showed that fibronectin binding to integrin αVβ3 caused the changes of the conformational flexibility of αVβ3 domains, the essential mode of motion for the domains of αV subunit and β3 subunit and the degrees of correlated motion of residues between the domains of αV subunit and β3 subunit of integrin αVβ3. The angle of Propeller domain with respect to the Calf-2 domain of αV subunit and the angle of Hybrid domain with respect to βA domain of β3 subunit significantly increased when integrin αVβ3 was bound to fibronectin. These changes could result in the conformational change tendency of αVβ3 from a bend conformation to an extended conformation and lead to the open swing of Hybrid domain relative to βA domain of β3 subunit, which have demonstrated their importance for αVβ3 activation. Fibronectin binding to integrin αVβ3 significantly decreased the relative position of α1 helix to βA domain and that to metal ion-dependent adhesion site, stabilized Mn2+ ions binding in integrin αVβ3 and changed fibronectin conformation, which are important for αVβ3 activation. Results from this study provide important molecular insight into the "outside-in" activation mechanism of integrin αVβ3 by binding to fibronectin.
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Affiliation(s)
- Lingyun Wang
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
| | - Di Pan
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
| | - Qi Yan
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
| | - Yuhua Song
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
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26
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Sens C, Huck K, Pettera S, Uebel S, Wabnitz G, Moser M, Nakchbandi IA. Fibronectins containing extradomain A or B enhance osteoblast differentiation via distinct integrins. J Biol Chem 2017; 292:7745-7760. [PMID: 28325836 DOI: 10.1074/jbc.m116.739987] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 03/10/2017] [Indexed: 12/16/2022] Open
Abstract
Fibronectin is a multidomain protein secreted by various cell types. It forms a network of fibers within the extracellular matrix and impacts intracellular processes by binding to various molecules, primarily integrin receptors on the cells. Both the presence of several isoforms and the ability of the various domains and isoforms to bind to a variety of integrins result in a wide range of effects. In vivo findings suggest that fibronectin isoforms produced by the osteoblasts enhance their differentiation. Here we report that the isoform characterized by the presence of extradomain A activates α4β1 integrin and augments osteoblast differentiation. In addition, the isoform containing extradomain B enhances the binding of fibronectin through the RGD sequence to β3-containing integrin, resulting in increased mineralization by and differentiation of osteoblasts. Our study thus reveals novel functions for two fibronectin isoforms and the mediating receptors in osteoblast differentiation.
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Affiliation(s)
- Carla Sens
- From the Max-Planck Institute of Biochemistry, 82152 Martinsried and.,the Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany
| | - Katrin Huck
- From the Max-Planck Institute of Biochemistry, 82152 Martinsried and.,the Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany
| | - Stefan Pettera
- From the Max-Planck Institute of Biochemistry, 82152 Martinsried and
| | - Stephan Uebel
- From the Max-Planck Institute of Biochemistry, 82152 Martinsried and
| | - Guido Wabnitz
- the Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany
| | - Markus Moser
- From the Max-Planck Institute of Biochemistry, 82152 Martinsried and
| | - Inaam A Nakchbandi
- From the Max-Planck Institute of Biochemistry, 82152 Martinsried and .,the Institute of Immunology, University of Heidelberg, 69120 Heidelberg, Germany
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27
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High Affinity vs. Native Fibronectin in the Modulation of αvβ3 Integrin Conformational Dynamics: Insights from Computational Analyses and Implications for Molecular Design. PLoS Comput Biol 2017; 13:e1005334. [PMID: 28114375 PMCID: PMC5293283 DOI: 10.1371/journal.pcbi.1005334] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 02/06/2017] [Accepted: 12/23/2016] [Indexed: 11/19/2022] Open
Abstract
Understanding how binding events modulate functional motions of multidomain proteins is a major issue in chemical biology. We address several aspects of this problem by analyzing the differential dynamics of αvβ3 integrin bound to wild type (wtFN10, agonist) or high affinity (hFN10, antagonist) mutants of fibronectin. We compare the dynamics of complexes from large-scale domain motions to inter-residue coordinated fluctuations to characterize the distinctive traits of conformational evolution and shed light on the determinants of differential αvβ3 activation induced by different FN sequences. We propose an allosteric model for ligand-based integrin modulation: the conserved integrin binding pocket anchors the ligand, while different residues on the two FN10's act as the drivers that reorganize relevant interaction networks, guiding the shift towards inactive (hFN10-bound) or active states (wtFN10-bound). We discuss the implications of results for the design of integrin inhibitors.
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28
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Xu XP, Kim E, Swift M, Smith JW, Volkmann N, Hanein D. Three-Dimensional Structures of Full-Length, Membrane-Embedded Human α(IIb)β(3) Integrin Complexes. Biophys J 2016; 110:798-809. [PMID: 26910421 DOI: 10.1016/j.bpj.2016.01.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 12/08/2015] [Accepted: 01/13/2016] [Indexed: 10/22/2022] Open
Abstract
Integrins are bidirectional, allosteric transmembrane receptors that play a central role in hemostasis and arterial thrombosis. Using cryo-electron microscopy, multireference single-particle reconstruction methods, and statistics-based computational fitting approaches, we determined three-dimensional structures of human integrin αIIbβ3 embedded in a lipid bilayer (nanodiscs) while bound to domains of the cytosolic regulator talin and to extracellular ligands. We also determined the conformations of integrin in solution by itself to localize the membrane and the talin-binding site. To our knowledge, our data provide unprecedented three-dimensional information about the conformational states of intact, full-length integrin within membrane bilayers under near-physiological conditions and in the presence of cytosolic activators and extracellular ligands. We show that αIIbβ3 integrins exist in a conformational equilibrium clustered around four main states. These conformations range from a compact bent nodule to two partially extended intermediate conformers and finally to a fully upright state. In the presence of nanodiscs and the two ligands, the equilibrium is significantly shifted toward the upright conformation. In this conformation, the receptor extends ∼20 nm upward from the membrane. There are no observable contacts between the two subunits other than those in the headpiece near the ligand-binding pocket, and the α- and β-subunits are well separated with their cytoplasmic tails ∼8 nm apart. Our results indicate that extension of the ectodomain is possible without separating the legs or extending the hybrid domain, and that the ligand-binding pocket is not occluded by the membrane in any conformations of the equilibrium. Further, they suggest that integrin activation may be influenced by equilibrium shifts.
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Affiliation(s)
- Xiao-Ping Xu
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Eldar Kim
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Mark Swift
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Jeffrey W Smith
- Infectious Disease Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Niels Volkmann
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
| | - Dorit Hanein
- Bioinformatics and Structural Biology Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
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29
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Fan Z, Ley K. Leukocyte arrest: Biomechanics and molecular mechanisms of β2 integrin activation. Biorheology 2016; 52:353-77. [PMID: 26684674 DOI: 10.3233/bir-15085] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Integrins are a group of heterodimeric transmembrane receptors that play essential roles in cell-cell and cell-matrix interaction. Integrins are important in many physiological processes and diseases. Integrins acquire affinity to their ligand by undergoing molecular conformational changes called activation. Here we review the molecular biomechanics during conformational changes of integrins, integrin functions in leukocyte biorheology (adhesive functions during rolling and arrest) and molecules involved in integrin activation.
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Affiliation(s)
- Zhichao Fan
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA
| | - Klaus Ley
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.,Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
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30
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Abstract
Integrins comprise a large family of αβ heterodimeric cell adhesion receptors that are expressed on all cells except red blood cells and that play essential roles in the regulation of cell growth and function. The leukocyte integrins, which include members of the β
1, β
2, β
3, and β
7 integrin family, are critical for innate and adaptive immune responses but also can contribute to many inflammatory and autoimmune diseases when dysregulated. This review focuses on the β
2 integrins, the principal integrins expressed on leukocytes. We review their discovery and role in host defense, the structural basis for their ligand recognition and activation, and their potential as therapeutic targets.
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Affiliation(s)
- M Amin Arnaout
- Leukocyte Biology & Inflammation Program, Structural Biology Program, Nephrology, Center for Regenerative Medicine, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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31
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Fan Z, McArdle S, Marki A, Mikulski Z, Gutierrez E, Engelhardt B, Deutsch U, Ginsberg M, Groisman A, Ley K. Neutrophil recruitment limited by high-affinity bent β2 integrin binding ligand in cis. Nat Commun 2016; 7:12658. [PMID: 27578049 PMCID: PMC5013657 DOI: 10.1038/ncomms12658] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Accepted: 07/20/2016] [Indexed: 12/28/2022] Open
Abstract
Neutrophils are essential for innate immunity and inflammation and many neutrophil functions are β2 integrin-dependent. Integrins can extend (E(+)) and acquire a high-affinity conformation with an 'open' headpiece (H(+)). The canonical switchblade model of integrin activation proposes that the E(+) conformation precedes H(+), and the two are believed to be structurally linked. Here we show, using high-resolution quantitative dynamic footprinting (qDF) microscopy combined with a homogenous conformation-reporter binding assay in a microfluidic device, that a substantial fraction of β2 integrins on human neutrophils acquire an unexpected E(-)H(+) conformation. E(-)H(+) β2 integrins bind intercellular adhesion molecules (ICAMs) in cis, which inhibits leukocyte adhesion in vitro and in vivo. This endogenous anti-inflammatory mechanism inhibits neutrophil aggregation, accumulation and inflammation.
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Affiliation(s)
- Zhichao Fan
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle Drive, La Jolla, California 92037, USA
| | - Sara McArdle
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle Drive, La Jolla, California 92037, USA.,Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | - Alex Marki
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle Drive, La Jolla, California 92037, USA
| | - Zbigniew Mikulski
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle Drive, La Jolla, California 92037, USA
| | - Edgar Gutierrez
- Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | - Britta Engelhardt
- Theodor Kocher Institute, University of Bern, 1 Freiestrasse, 3012 Bern, Switzerland
| | - Urban Deutsch
- Theodor Kocher Institute, University of Bern, 1 Freiestrasse, 3012 Bern, Switzerland
| | - Mark Ginsberg
- Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | - Alex Groisman
- Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | - Klaus Ley
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle Drive, La Jolla, California 92037, USA.,Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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32
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The role of integrins in glaucoma. Exp Eye Res 2016; 158:124-136. [PMID: 27185161 DOI: 10.1016/j.exer.2016.05.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 05/06/2016] [Accepted: 05/10/2016] [Indexed: 01/04/2023]
Abstract
Integrins are a family of heterodimeric transmembrane receptors that mediate adhesion to the extracellular matrix (ECM). In addition to their role as adhesion receptors, integrins can act as ''bidirectional signal transducers'' that coordinate a large number of cellular activities in response to the extracellular environment and intracellular signaling events. This bidirectional signaling helps maintain tissue homeostasis. Dysregulated bidirectional signaling, however, could trigger the propagation of feedback loops that can lead to the establishment of a disease state such as glaucoma. Here we discuss the role of integrins and bidirectional signaling as they relate to the glaucomatous phenotype with special emphasis on the αvβ3 integrin. We present evidence that this particular integrin may have a significant impact on the pathogenesis of glaucoma.
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33
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Bruce AG, Horst JA, Rose TM. Conservation of the glycoprotein B homologs of the Kaposi׳s sarcoma-associated herpesvirus (KSHV/HHV8) and old world primate rhadinoviruses of chimpanzees and macaques. Virology 2016; 494:29-46. [PMID: 27070755 DOI: 10.1016/j.virol.2016.04.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 03/29/2016] [Accepted: 04/01/2016] [Indexed: 01/09/2023]
Abstract
The envelope-associated glycoprotein B (gB) is highly conserved within the Herpesviridae and plays a critical role in viral entry. We analyzed the evolutionary conservation of sequence and structural motifs within the Kaposi׳s sarcoma-associated herpesvirus (KSHV) gB and homologs of Old World primate rhadinoviruses belonging to the distinct RV1 and RV2 rhadinovirus lineages. In addition to gB homologs of rhadinoviruses infecting the pig-tailed and rhesus macaques, we cloned and sequenced gB homologs of RV1 and RV2 rhadinoviruses infecting chimpanzees. A structural model of the KSHV gB was determined, and functional motifs and sequence variants were mapped to the model structure. Conserved domains and motifs were identified, including an "RGD" motif that plays a critical role in KSHV binding and entry through the cellular integrin αVβ3. The RGD motif was only detected in RV1 rhadinoviruses suggesting an important difference in cell tropism between the two rhadinovirus lineages.
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Affiliation(s)
- A Gregory Bruce
- Center for Global Infectious Disease Research, Seattle Children׳s Research Institute, Seattle, WA, United States
| | - Jeremy A Horst
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, United States
| | - Timothy M Rose
- Center for Global Infectious Disease Research, Seattle Children׳s Research Institute, Seattle, WA, United States; Department of Pediatrics, University of Washington, Seattle, WA, United States.
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34
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Identification and characterization of a unique role for EDB fibronectin in phagocytosis. J Mol Med (Berl) 2015; 94:567-81. [PMID: 26637426 PMCID: PMC4856727 DOI: 10.1007/s00109-015-1373-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 11/12/2015] [Accepted: 11/19/2015] [Indexed: 01/21/2023]
Abstract
Abstract Plasma fibronectin is a circulating protein that facilitates phagocytosis by connecting bacteria to immune cells. A fibronectin isoform, which includes a sequence of 90 AA called extra-domain B (EDB), is synthesized de novo at the messenger RNA (mRNA) level in immune cells, but the reason for its expression remains elusive. We detected an 80-fold increase in EDB-containing fibronectin in the cerebrospinal fluid of patients with bacterial meningitis that was most pronounced in staphylococcal infections. A role for this isoform in phagocytosis was further suggested by enhanced EDB fibronectin release after internalization of Staphylococcus aureus in vitro. Using transgenic mouse models, we established that immune cell production of fibronectin contributes to phagocytosis, more so than circulating plasma fibronectin, and that accentuated release of EDB-containing fibronectin by immune cells improved phagocytosis. In line with this, administration of EDB fibronectin enhanced in vitro phagocytosis to a larger extent than plasma fibronectin. This enhancement was mediated by αvβ3 integrin as shown using inhibitors or cells from β3 integrin knockout mice. Thus, we identified both a novel function for EDB fibronectin in augmenting phagocytosis over circulating plasma fibronectin, as well as the mediating receptor. Our data also establish for the first time, a direct role for β3 integrin in bacterial phagocytosis in mammals. Key messages • Fibronectin containing an extra domain called EDB is released in bacterial meningitis. • EDB-containing fibronectin enhances phagocytosis more than plasma fibronectin. • The enhancement is mediated by activation of αvβ3 integrin in the presence of EDB. Electronic supplementary material The online version of this article (doi:10.1007/s00109-015-1373-0) contains supplementary material, which is available to authorized users.
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35
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Dai A, Ye F, Taylor DW, Hu G, Ginsberg MH, Taylor KA. The Structure of a Full-length Membrane-embedded Integrin Bound to a Physiological Ligand. J Biol Chem 2015; 290:27168-27175. [PMID: 26391523 DOI: 10.1074/jbc.m115.682377] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Indexed: 11/06/2022] Open
Abstract
Increased ligand binding to integrin ("activation") underpins many biological processes, such as leukocyte trafficking, cell migration, host-pathogen interaction, and hemostasis. Integrins exist in several conformations, ranging from compact and bent to extended and open. However, the exact conformation of membrane-embedded, full-length integrin bound to its physiological macromolecular ligand is still unclear. Integrin αIIbβ3, the most abundant integrin in platelets, has been a prototype for integrin activation studies. Using negative stain electron microscopy and nanodisc-embedding to provide a membrane-like environment, we visualized the conformation of full-length αIIbβ3 in both a Mn(2+)-activated, ligand-free state and a Mn(2+)-activated, fibrin-bound state. Activated but ligand-free integrins exist mainly in the compact conformation, whereas fibrin-bound αIIbβ3 predominantly exists in a fully extended, headpiece open conformation. Our results show that membrane-embedded, full-length integrin adopts an extended and open conformation when bound to its physiological macromolecular ligand.
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Affiliation(s)
- Aguang Dai
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and
| | - Feng Ye
- Department of Hematology and Oncology, University of California at San Diego, La Jolla, California 92093-0726
| | - Dianne W Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and
| | - Guiqing Hu
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and
| | - Mark H Ginsberg
- Department of Hematology and Oncology, University of California at San Diego, La Jolla, California 92093-0726
| | - Kenneth A Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306-4380 and.
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36
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Lee WH, Schaffner-Reckinger E, Tsoukatos DC, Aylward K, Moussis V, Tsikaris V, Trypou P, Egot M, Baruch D, Kieffer N, Bachelot-Loza C. Inhibition of αIIbβ3 Ligand Binding by an αIIb Peptide that Clasps the Hybrid Domain to the βI Domain of β3. PLoS One 2015; 10:e0134952. [PMID: 26332040 PMCID: PMC4557944 DOI: 10.1371/journal.pone.0134952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 07/15/2015] [Indexed: 11/22/2022] Open
Abstract
Agonist-stimulated platelet activation triggers conformational changes of integrin αIIbβ3, allowing fibrinogen binding and platelet aggregation. We have previously shown that an octapeptide, p1YMESRADR8, corresponding to amino acids 313–320 of the β-ribbon extending from the β-propeller domain of αIIb, acts as a potent inhibitor of platelet aggregation. Here we have performed in silico modelling analysis of the interaction of this peptide with αIIbβ3 in its bent and closed (not swing-out) conformation and show that the peptide is able to act as a substitute for the β-ribbon by forming a clasp restraining the β3 hybrid and βI domains in a closed conformation. The involvement of species-specific residues of the β3 hybrid domain (E356 and K384) and the β1 domain (E297) as well as an intrapeptide bond (pE315-pR317) were confirmed as important for this interaction by mutagenesis studies of αIIbβ3 expressed in CHO cells and native or substituted peptide inhibitory studies on platelet functions. Furthermore, NMR data corroborate the above results. Our findings provide insight into the important functional role of the αIIb β-ribbon in preventing integrin αIIbβ3 head piece opening, and highlight a potential new therapeutic approach to prevent integrin ligand binding.
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Affiliation(s)
- Wen Hwa Lee
- SGC, University of Oxford, Oxford, United Kingdom
| | - Elisabeth Schaffner-Reckinger
- Laboratoire de Biologie et Physiologie Intégrée, (CNRS/GDRE-ITI), University of Luxembourg, Luxembourg City, Luxembourg
| | | | - Kelly Aylward
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Vassilios Moussis
- Department of Chemistry, Section of Organic Chemistry and Biochemistry, Ioannina, Greece
| | - Vassilios Tsikaris
- Department of Chemistry, Section of Organic Chemistry and Biochemistry, Ioannina, Greece
| | - Paraskevi Trypou
- Department of Chemistry, Section of Organic Chemistry and Biochemistry, Ioannina, Greece
| | - Marion Egot
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Dominique Baruch
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Nelly Kieffer
- Laboratoire de Biologie et Physiologie Intégrée, (CNRS/GDRE-ITI), University of Luxembourg, Luxembourg City, Luxembourg
- CNRS-LIA124, Sino-French Research Center for Life Sciences and Genomics, Rui Jin Hospital, Jiao Tong University School of Medicine, Shanghai, China
| | - Christilla Bachelot-Loza
- Inserm UMR_S 1140, Faculté de pharmacie, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- * E-mail:
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37
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Roll, adhere, spread and contract: structural mechanics of platelet function. Eur J Cell Biol 2015; 94:129-38. [PMID: 25655000 DOI: 10.1016/j.ejcb.2015.01.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 12/26/2014] [Accepted: 01/07/2015] [Indexed: 12/31/2022] Open
Abstract
Platelets are involved in life-sustaining processes such as hemostasis, wound healing, atherothrombosis and angiogenesis. Mechanical trauma to blood vessels causes platelet activation resulting in their adherence and clot formation at the damaged site, culminating in clot retraction and tissue repair. Two of the major players underlying this process are the cytoskeleton, i.e., actin and microtubules, and the membrane integrin receptors. Rare congenital bleeding disorders such as Glanzmann thrombasthenia and Bernard-Soulier syndrome are associated with genetic alterations of platelet surface receptors, also affecting the platelet cytoskeletal structure. In this review, we summarize the current knowledge about platelet structure and adhesion, and delve into the mechanical aspects of platelet function. Platelets lack a nucleus, and can thus provide a minimal model of a biological cell. New biophysical tools may help to scrutinize platelets anew and to extend the existing knowledge on cell biology.
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38
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Integrin-mediated adhesion and mechano-sensing in cutaneous wound healing. Cell Tissue Res 2014; 360:571-82. [DOI: 10.1007/s00441-014-2064-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Accepted: 11/11/2014] [Indexed: 12/30/2022]
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39
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Müller MA, Brunie L, Bächer AS, Kessler H, Gottschalk KE, Reuning U. Cytoplasmic salt bridge formation in integrin αvß3 stabilizes its inactive state affecting integrin-mediated cell biological effects. Cell Signal 2014; 26:2493-503. [PMID: 25041847 DOI: 10.1016/j.cellsig.2014.07.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 07/09/2014] [Indexed: 02/01/2023]
Abstract
Heterodimeric integrin receptors are mediators of cell adhesion, motility, invasion, proliferation, and survival. By this, they are crucially involved in (tumor) cell biological behavior. Integrins trigger signals bidirectionally across cell membranes: by outside-in, following binding of protein ligands of the extracellular matrix, and by inside-out, where proteins are recruited to ß-integrin cytoplasmic tails resulting in conformational changes leading to increased integrin binding affinity and integrin activation. Computational modeling and experimental/mutational approaches imply that associations of integrin transmembrane domains stabilize the low-affinity integrin state. Moreover, a cytoplasmic interchain salt bridge is discussed to contribute to a tight clasp of the α/ß-membrane-proximal regions; however, its existence and physiological relevance for integrin activation are still a controversial issue. In order to further elucidate the functional role of salt bridge formation, we designed mutants of the tumor biologically relevant integrin αvß3 by mutually exchanging the salt bridge forming amino acid residues on each chain (αvR995D and ß3D723R). Following transfection of human ovarian cancer cells with different combinations of wild type and mutated integrin chains, we showed that loss of salt bridge formation strengthened αvß3-mediated adhesion to vitronectin, provoked recruitment of cytoskeletal proteins, such as talin, and induced integrin signaling, ultimately resulting in enhanced cell migration, proliferation, and activation of integrin-related signaling molecules. These data support the notion of a functional relevance of integrin cytoplasmic salt bridge disruption during integrin activation.
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Affiliation(s)
- Martina A Müller
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany
| | - Leonora Brunie
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany
| | - Anne-Sophie Bächer
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany
| | - Horst Kessler
- Institute for Advanced Study and Centre of Integrated Protein Science, Department Chemie, Technische Universitaet München, Garching, Germany; Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | | | - Ute Reuning
- Clinical Research Unit, Dept. for Obstetrics & Gynecology, Technische Universitaet München, Munich, Germany.
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40
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Single-particle EM reveals plasticity of interactions between the adenovirus penton base and integrin αVβ3. Proc Natl Acad Sci U S A 2014; 111:8815-9. [PMID: 24889614 DOI: 10.1073/pnas.1404575111] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human adenoviruses are double-stranded DNA viruses responsible for numerous infections, some of which can be fatal. Furthermore, adenoviruses are currently used in clinical trials as vectors for gene therapy applications. Although initial binding of adenoviruses to host attachment receptors has been extensively characterized, the interactions with the entry receptor (integrins) remain poorly understood at the structural level. We characterized the interactions between the adenovirus 9 penton base subunit and αVβ3 integrin using fluorescence correlation spectroscopy and single-particle electron microscopy to understand the mechanisms underlying virus internalization and infection. Our results indicate that the penton base subunit can bind integrins with high affinity and in several different orientations. These outcomes correlate with the requirement of the pentameric penton base to simultaneously bind several integrins to enable their clustering and promote virus entry into the host cell.
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41
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Anderson LR, Owens TW, Naylor MJ. Structural and mechanical functions of integrins. Biophys Rev 2014; 6:203-213. [PMID: 28510180 PMCID: PMC5418412 DOI: 10.1007/s12551-013-0124-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 08/28/2013] [Indexed: 01/09/2023] Open
Abstract
Integrins are ubiquitously expressed cell surface receptors that play a critical role in regulating the interaction between a cell and its microenvironment to control cell fate. These molecules are regulated either via their expression on the cell surface or through a unique bidirectional signalling mechanism. However, integrins are just the tip of the adhesome iceberg, initiating the assembly of a large range of adaptor and signalling proteins that mediate the structural and signalling functions of integrin. In this review, we summarise the structure of integrins and mechanisms by which integrin activation is controlled. The different adhesion structures formed by integrins are discussed, as well as the mechanical and structural roles integrins play during cell migration. As the function of integrin signalling can be quite varied based on cell type and context, an in depth understanding of these processes will aid our understanding of aberrant adhesion and migration, which is often associated with human pathologies such as cancer.
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Affiliation(s)
- Luke R Anderson
- Discipline of Physiology & Bosch Institute, School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia
| | - Thomas W Owens
- Discipline of Physiology & Bosch Institute, School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia
| | - Matthew J Naylor
- Discipline of Physiology & Bosch Institute, School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia.
- The University of Sydney, Room E212, Anderson Stuart Building (F13), Sydney, NSW, 2006, Australia.
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42
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Van Agthoven JF, Xiong JP, Alonso JL, Rui X, Adair BD, Goodman SL, Arnaout MA. Structural basis for pure antagonism of integrin αVβ3 by a high-affinity form of fibronectin. Nat Struct Mol Biol 2014; 21:383-8. [PMID: 24658351 PMCID: PMC4012256 DOI: 10.1038/nsmb.2797] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 02/24/2014] [Indexed: 01/07/2023]
Abstract
Integrins are important therapeutic targets. However, current RGD-based anti-integrin drugs are also partial agonists, inducing conformational changes that trigger potentially fatal immune reactions and paradoxical cell adhesion. Here we describe the first crystal structure of αVβ3 bound to a physiologic ligand, the tenth type III RGD domain of wild-type fibronectin (wtFN10), or to a high-affinity mutant (hFN10) shown here to act as a pure antagonist. Comparison of these structures revealed a central π-π interaction between Trp1496 in the RGD-containing loop of hFN10 and Tyr122 of the β3 subunit that blocked conformational changes triggered by wtFN10 and trapped hFN10-bound αVβ3 in an inactive conformation. Removing the Trp1496 or Tyr122 side chains or reorienting Trp1496 away from Tyr122 converted hFN10 into a partial agonist. These findings offer new insights into the mechanism of integrin activation and a basis for the design of RGD-based pure antagonists.
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Affiliation(s)
- Johannes F. Van Agthoven
- Structural Biology Program, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129
| | - Jian-Ping Xiong
- Structural Biology Program, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129
| | - José Luis Alonso
- Leukocyte Biology & Inflammation Program, Department of Medicine, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129
| | - Xianliang Rui
- Leukocyte Biology & Inflammation Program, Department of Medicine, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129
| | - Brian D. Adair
- Structural Biology Program, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129
| | - Simon L. Goodman
- Harvard Medical School, Global Research and Early Development, Translational Innovation platform, Oncology, Merck KGaA, Darmstadt 64271, Germany
| | - M. Amin Arnaout
- Structural Biology Program, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129,Leukocyte Biology & Inflammation Program, Department of Medicine, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129
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43
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Mahalingam B, Van Agthoven JF, Xiong JP, Alonso JL, Adair BD, Rui X, Anand S, Mehrbod M, Mofrad MRK, Burger C, Goodman SL, Arnaout MA. Atomic basis for the species-specific inhibition of αV integrins by monoclonal antibody 17E6 is revealed by the crystal structure of αVβ3 ectodomain-17E6 Fab complex. J Biol Chem 2014; 289:13801-9. [PMID: 24692540 DOI: 10.1074/jbc.m113.546929] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The function-blocking, non-RGD-containing, and primate-specific mouse monoclonal antibody 17E6 binds the αV subfamily of integrins. 17E6 is currently in phase II clinical trials for treating cancer. To elucidate the structural basis of recognition and the molecular mechanism of inhibition, we crystallized αVβ3 ectodomain in complex with the Fab fragment of 17E6. Protein crystals grew in presence of the activating cation Mn(2+). The integrin in the complex and in solution assumed the genuflected conformation. 17E6 Fab bound exclusively to the Propeller domain of the αV subunit. At the core of αV-Fab interface were interactions involving Propeller residues Lys-203 and Gln-145, with the latter accounting for primate specificity. The Propeller residue Asp-150, which normally coordinates Arg of the ligand Arg-Gly-Asp motif, formed contacts with Arg-54 of the Fab that were expected to reduce soluble FN10 binding to cellular αVβ3 complexed with 17E6. This was confirmed in direct binding studies, suggesting that 17E6 is an allosteric inhibitor of αV integrins.
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Affiliation(s)
| | | | | | - José Luis Alonso
- the Leukocyte Biology and Inflammation Program, Departments of Medicine and Developmental & Regenerative Biology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | | | - Xianliang Rui
- the Leukocyte Biology and Inflammation Program, Departments of Medicine and Developmental & Regenerative Biology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Saurabh Anand
- the Leukocyte Biology and Inflammation Program, Departments of Medicine and Developmental & Regenerative Biology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Mehrdad Mehrbod
- the Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720
| | - Mohammad R K Mofrad
- the Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720
| | - Christa Burger
- Merck KGaA and Discovery Technologies, Molecular Pharmacology, and
| | - Simon L Goodman
- Merck KGaA and Therapeutic Innovation Platform, Oncology, Darmstadt 64271, Germany
| | - M Amin Arnaout
- From the Structural Biology Program and the Leukocyte Biology and Inflammation Program, Departments of Medicine and Developmental & Regenerative Biology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129,
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44
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Drayman N, Glick Y, Ben-nun-shaul O, Zer H, Zlotnick A, Gerber D, Schueler-Furman O, Oppenheim A. Pathogens use structural mimicry of native host ligands as a mechanism for host receptor engagement. Cell Host Microbe 2014; 14:63-73. [PMID: 23870314 DOI: 10.1016/j.chom.2013.05.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 04/04/2013] [Accepted: 05/03/2013] [Indexed: 11/25/2022]
Abstract
A pathogen's ability to engage host receptors is a critical determinant of its host range and interspecies transmissibility, key issues for understanding emerging diseases. However, the identification of host receptors, which are also attractive drug targets, remains a major challenge. Our structural bioinformatics studies reveal that both bacterial and viral pathogens have evolved to structurally mimic native host ligands (ligand mimicry), thus enabling engagement of their cognate host receptors. In contrast to the structural homology, amino acid sequence similarity between pathogen molecules and the mimicked host ligands was low. We illustrate the utility of this concept to identify pathogen receptors by delineating receptor tyrosine kinase Axl as a candidate receptor for the polyomavirus SV40. The SV40-Axl interaction was validated, and its participation in the infection process was verified. Our results suggest that ligand mimicry is widespread, and we present a quick tool to screen for pathogen-host receptor interactions.
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Affiliation(s)
- Nir Drayman
- Department of Haematology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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45
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Opposing effects of collagen I and vitronectin on fibronectin fibril structure and function. Matrix Biol 2014; 34:33-45. [PMID: 24509439 DOI: 10.1016/j.matbio.2014.01.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 01/27/2014] [Accepted: 01/28/2014] [Indexed: 11/21/2022]
Abstract
Extracellular matrix fibronectin fibrils serve as passive structural supports for the organization of cells into tissues, yet can also actively stimulate a variety of cell and tissue functions, including cell proliferation. Factors that control and coordinate the functional activities of fibronectin fibrils are not known. Here, we compared effects of cell adhesion to vitronectin versus type I collagen on the assembly of and response to, extracellular matrix fibronectin fibrils. The amount of insoluble fibronectin matrix fibrils assembled by fibronectin-null mouse embryonic fibroblasts adherent to collagen- or vitronectin-coated substrates was not significantly different 20 h after fibronectin addition. However, the fibronectin matrix produced by vitronectin-adherent cells was ~10-fold less effective at enhancing cell proliferation than that of collagen-adherent cells. Increasing insoluble fibronectin levels with the fibronectin fragment, anastellin did not increase cell proliferation. Rather, native fibronectin fibrils polymerized by collagen- and vitronectin-adherent cells exhibited conformational differences in the growth-promoting, III-1 region of fibronectin, with collagen-adherent cells producing fibronectin fibrils in a more extended conformation. Fibronectin matrix assembly on either substrate was mediated by α5β1 integrins. However, on vitronectin-adherent cells, α5β1 integrins functioned in a lower activation state, characterized by reduced 9EG7 binding and decreased talin association. The inhibitory effect of vitronectin on fibronectin-mediated cell proliferation was localized to the cell-binding domain, but was not a general property of αvβ3 integrin-binding substrates. These data suggest that adhesion to vitronectin allows for the uncoupling of fibronectin fibril formation from downstream signaling events by reducing α5β1 integrin activation and fibronectin fibril extension.
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Measurement of cationic and intracellular modulation of integrin binding affinity by AFM-based nanorobot. Biophys J 2014; 105:40-7. [PMID: 23823222 DOI: 10.1016/j.bpj.2013.05.052] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 05/12/2013] [Accepted: 05/30/2013] [Indexed: 11/23/2022] Open
Abstract
Integrins are dynamic transmembrane cation-dependent heterodimers that both anchor cells in position and transduce signals into and out of cells. We used an atomic force microscope (AFM)-based nanorobotic system to measure integrin-binding forces in intact human intestinal epithelial Caco-2 cells. The AFM-based nanorobot enables human-directed, high-accuracy probe positioning and site-specific investigations. Functionalizing the AFM probe with an arginine-glycine-aspartate (RGD)-containing sequence (consensus binding sequence for integrins) allowed us to detect a series of peptide-cell membrane interactions with a median binding force of 115.1 ± 4.9 pN that were not detected in control interactions. Chelating divalent cations from the culture medium abolished these interactions, as did inhibiting intracellular focal adhesion kinase (FAK) using Y15. Adding 1 mM Mg(2+) to the medium caused a rightward shift in the force-binding curve. Adding 1 mM Ca(2+) virtually abolished the RGD-membrane specific interactions and blocked the Mg(2+) effects. Cell adhesion assays demonstrated parallel effects of divalent cations and the FAK inhibitor on cell adhesion. These results demonstrate direct modulation of integrin-binding affinity by both divalent cations and intracellular signal inhibition. Additionally, three binding states (nonspecific, specific inactivated, and specific activated) were delineated from affinity measurements. Although other research has assumed that this process of integrin conformational change causes altered ligand binding, in this work we directly measured these three states in individual integrins in a physiologically based study.
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Ye F, Snider AK, Ginsberg MH. Talin and kindlin: the one-two punch in integrin activation. Front Med 2014; 8:6-16. [DOI: 10.1007/s11684-014-0317-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 11/29/2013] [Indexed: 11/25/2022]
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Jahed Z, Shams H, Mehrbod M, Mofrad MRK. Mechanotransduction pathways linking the extracellular matrix to the nucleus. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 310:171-220. [PMID: 24725427 DOI: 10.1016/b978-0-12-800180-6.00005-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cells contain several mechanosensing components that transduce mechanical signals into biochemical cascades. During cell-ECM adhesion, a complex network of molecules mechanically couples the extracellular matrix (ECM), cytoskeleton, and nucleoskeleton. The network comprises transmembrane receptor proteins and focal adhesions, which link the ECM and cytoskeleton. Additionally, recently identified protein complexes extend this linkage to the nucleus by linking the cytoskeleton and the nucleoskeleton. Despite numerous studies in this field, due to the complexity of this network, our knowledge of the mechanisms of cell-ECM adhesion at the molecular level remains remarkably incomplete. Herein, we present a review of the structures of key molecules involved in cell-ECM adhesion, along with an evaluation of their predicted roles in mechanical sensing. Additionally, specific binding events prompted by force-induced conformational changes of each molecule are discussed. Finally, we propose a model for the biomechanical events prominent in cell-ECM adhesion.
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Affiliation(s)
- Zeinab Jahed
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California at Berkeley, Berkeley, California, USA
| | - Hengameh Shams
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California at Berkeley, Berkeley, California, USA
| | - Mehrdad Mehrbod
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California at Berkeley, Berkeley, California, USA
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California at Berkeley, Berkeley, California, USA.
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Ballut L, Sapay N, Chautard E, Imberty A, Ricard-Blum S. Mapping of heparin/heparan sulfate binding sites on αvβ3 integrin by molecular docking. J Mol Recognit 2013; 26:76-85. [PMID: 23334915 DOI: 10.1002/jmr.2250] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 10/15/2012] [Accepted: 10/15/2012] [Indexed: 01/24/2023]
Abstract
Heparin/heparan sulfate interact with growth factors, chemokines, extracellular proteins, and receptors. Integrins are αβ heterodimers that serve as receptors for extracellular proteins, regulate cell behavior, and participate in extracellular matrix assembly. Heparin binds to RGD-dependent integrins (αIIbβ3, α5β1, αvβ3, and αvβ5) and to RGD-independent integrins (α4β1, αXβ2, and αMβ2), but their binding sites have not been located on integrins. We report the mapping of heparin binding sites on the ectodomain of αvβ3 integrin by molecular modeling. The surface of the ectodomain was scanned with small rigid probes mimicking the sulfated domains of heparan sulfate. Docking results were clustered into binding spots. The best results were selected for further docking simulations with heparin hexasaccharide. Six potential binding spots containing lysine and/or arginine residues were identified on the ectodomain of αvβ3 integrin. Heparin would mostly bind to the top of the genu domain, the Calf-I domain of the α subunit, and the top of the β subunit of RGD-dependent integrins. Three spots were close enough from each other on the integrin surface to form an extended binding site that could interact with heparin/heparan sulfate chains. Because heparin does not bind to the same integrin site as protein ligands, no steric hindrance prevents the formation of ternary complexes comprising the integrin, its protein ligand, and heparin/heparan sulfate. The basic amino acid residues predicted to interact with heparin are conserved in the sequences of RGD-dependent but not of RGD-independent integrins suggesting that heparin/heparan sulfate could bind to different sites on these two integrin subfamilies.
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Affiliation(s)
- Lionel Ballut
- UMR 5086 CNRS-Université Lyon 1, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, 69367 Lyon Cedex 07, France
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Three-dimensional reconstruction of intact human integrin αIIbβ3: new implications for activation-dependent ligand binding. Blood 2013; 122:4165-71. [PMID: 24136164 DOI: 10.1182/blood-2013-04-499194] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Integrin αIIbβ3 plays a central role in hemostasis and thrombosis. We provide the first 3-dimensional reconstruction of intact purified αIIbβ3 in a nanodisc lipid bilayer. Unlike previous models, it shows that the ligand-binding head domain is on top, pointing away from the membrane. Moreover, unlike the crystal structure of the recombinant ectodomain, the lower legs are not parallel, straight, and adjacent. Rather, the αIIb lower leg is bent between the calf-1 and calf-2 domains and the β3 Integrin-Epidermal Growth Factor (I-EGF) 2 to 4 domains are freely coiled rather than in a cleft between the β3 headpiece and the αIIb lower leg. Our data indicate an important role for the region that links the distal calf-2 and β-tail domains to their respective transmembrane (TM) domains in transmitting the conformational changes in the TM domains associated with inside-out activation.
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