1
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Niu T, Li Z, Huang Y, Ye Y, Liu Y, Ye Z, Jiang L, He X, Wang L, Li J. LFA-1 knockout inhibited the tumor growth and is correlated with treg cells. Cell Commun Signal 2023; 21:233. [PMID: 37723552 PMCID: PMC10506322 DOI: 10.1186/s12964-023-01238-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 07/19/2023] [Indexed: 09/20/2023] Open
Abstract
Cancer immunotherapy has been proven to be clinically effective in multiple types of cancers. Lymphocyte function-associated antigen 1 (LFA-1), a member of the integrin family of adhesion molecules, is expressed mainly on αβ T cells. LFA-1 is associated with tumor immune responses, but its exact mechanism remains unknown. Here, two kinds of mice tumor model of LFA-1 knockout (LFA-1-/-) mice bearing subcutaneous tumor and Apc Min/+;LFA-1-/- mice were used to confirm that LFA-1 knockout resulted in inhibition of tumor growth. Furthermore, it also demonstrated that the numbers of regulatory T cells (Treg cells) in the spleen, blood, mesenteric lymph nodes were decreased in LFA-1-/- mice, and the numbers of Treg cells in mesenteric lymph nodes were also decreased in Apc Min/+;LFA-1-/- mice compared with Apc Min/+ mice. LFA-1 inhibitor (BIRT377) was administered to subcutaneous tumor-bearing LFA-1+/+ mice, and the results showed that the tumor growth was inhibited and the number of Treg cells was reduced. The analysis of TIMER tumor database indicated that LFA-1 expression is positively associated with Treg cells and TNM stage. Conclusively, this suggests that LFA-1 knockout would inhibit tumor growth and is correlated with Treg cells. LFA-1 may be one potential target for cancer immunotherapy. Video Abstract.
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Affiliation(s)
- Ting Niu
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Zhengyang Li
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Yiting Huang
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Yuxiang Ye
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Yilong Liu
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Zhijin Ye
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Lingbi Jiang
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Xiaodong He
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China
| | - Lijing Wang
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China.
| | - Jiangchao Li
- Institute of Basic Medical Sciences, School of Life Sciences and Biopharmaceuticals, Guangdong Pharmaceutical University, No. 280 Waihuan Rd. E, Higher Education Mega Center, 510006, Guangzhou, China.
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2
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Moore TI, Aaron J, Chew TL, Springer TA. Measuring Integrin Conformational Change on the Cell Surface with Super-Resolution Microscopy. Cell Rep 2019; 22:1903-1912. [PMID: 29444440 PMCID: PMC5851489 DOI: 10.1016/j.celrep.2018.01.062] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/19/2017] [Accepted: 01/19/2018] [Indexed: 02/08/2023] Open
Abstract
We use super-resolution interferometric photoactivation and localization microscopy (iPALM) and a constrained photoactivatable fluorescent protein integrin fusion to measure the displacement of the head of integrin lymphocyte function-associated 1 (LFA-1) resulting from integrin conformational change on the cell surface. We demonstrate that the distance of the LFA-1 head increases substantially between basal and ligand-engaged conformations, which can only be explained at the molecular level by integrin extension. We further demonstrate that one class of integrin antagonist maintains the bent conformation, while another antagonist class induces extension. Our molecular scale measurements on cell-surface LFA-1 are in excellent agreement with distances derived from crystallographic and electron microscopy structures of bent and extended integrins. Our distance measurements are also in excellent agreement with a previous model of LFA-1 bound to ICAM-1 derived from the orientation of LFA-1 on the cell surface measured using fluorescence polarization microscopy.
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Affiliation(s)
- Travis I Moore
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA
| | - Jesse Aaron
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Teng-Leong Chew
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Timothy A Springer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
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3
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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: 37] [Impact Index Per Article: 4.6] [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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4
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Lahtinen S, Wang Q, Soukka T. Long-Lifetime Luminescent Europium(III) Complex as an Acceptor in an Upconversion Resonance Energy Transfer Based Homogeneous Assay. Anal Chem 2015; 88:653-8. [DOI: 10.1021/acs.analchem.5b02228] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Satu Lahtinen
- Department of Biochemistry/Biotechnology, University of Turku, Tykistökatu 6 A, 20520 Turku, Finland
| | - Qi Wang
- Department of Biochemistry/Biotechnology, University of Turku, Tykistökatu 6 A, 20520 Turku, Finland
| | - Tero Soukka
- Department of Biochemistry/Biotechnology, University of Turku, Tykistökatu 6 A, 20520 Turku, Finland
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5
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Johnson A, Saunders MJ, Back TG. Stereodivergent synthesis of the LFA-1 antagonist BIRT-377 by porcine liver esterase desymmetrization and Curtius rearrangement. Org Biomol Chem 2015; 13:1463-9. [DOI: 10.1039/c4ob02303j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BIRT-377 was synthesized by enzymatic desymmetrization in conjunction with Curtius rearrangement, affording a key α-quaternary amine intermediate in high ee.
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Affiliation(s)
- Aaron Johnson
- Department of Chemistry
- University of Calgary
- 2500 University Drive NW
- Calgary AB
- Canada
| | - Matthew J. Saunders
- Department of Chemistry
- University of Calgary
- 2500 University Drive NW
- Calgary AB
- Canada
| | - Thomas G. Back
- Department of Chemistry
- University of Calgary
- 2500 University Drive NW
- Calgary AB
- Canada
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6
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Chigaev A, Smagley Y, Haynes MK, Ursu O, Bologa CG, Halip L, Oprea T, Waller A, Carter MB, Zhang Y, Wang W, Buranda T, Sklar LA. FRET detection of lymphocyte function-associated antigen-1 conformational extension. Mol Biol Cell 2014; 26:43-54. [PMID: 25378583 PMCID: PMC4279228 DOI: 10.1091/mbc.e14-06-1050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Lymphocyte function–associated antigen 1 (LFA-1) and its ligands are essential for immune cell interactions. LFA-1 is regulated through conformational changes. The relationship between molecular conformation and function is unclear. Förster resonance energy transfer is used to assess LFA-1 conformation under real-time signaling conditions. Lymphocyte function–associated antigen 1 (LFA-1, CD11a/CD18, αLβ2-integrin) and its ligands are essential for adhesion between T-cells and antigen-presenting cells, formation of the immunological synapse, and other immune cell interactions. LFA-1 function is regulated through conformational changes that include the modulation of ligand binding affinity and molecular extension. However, the relationship between molecular conformation and function is unclear. Here fluorescence resonance energy transfer (FRET) with new LFA-1–specific fluorescent probes showed that triggering of the pathway used for T-cell activation induced rapid unquenching of the FRET signal consistent with extension of the molecule. Analysis of the FRET quenching at rest revealed an unexpected result that can be interpreted as a previously unknown LFA-1 conformation.
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Affiliation(s)
| | | | - Mark K Haynes
- University of New Mexico Center for Molecular Discovery, and
| | - Oleg Ursu
- University of New Mexico Center for Molecular Discovery, and Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM 87131
| | - Cristian G Bologa
- University of New Mexico Center for Molecular Discovery, and Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM 87131
| | - Liliana Halip
- Department of Computational Chemistry, Institute of Chemistry, Romanian Academy, Timisoara 300223, Romania
| | - Tudor Oprea
- University of New Mexico Center for Molecular Discovery, and Department of Internal Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM 87131
| | - Anna Waller
- University of New Mexico Center for Molecular Discovery, and
| | - Mark B Carter
- University of New Mexico Center for Molecular Discovery, and
| | - Yinan Zhang
- Department of Pharmaceutical Science, College of Pharmacy, University of Kentucky, Lexington, KY 40506
| | - Wei Wang
- Department of Chemistry, University of New Mexico, Albuquerque, NM 87131
| | | | - Larry A Sklar
- Department of Pathology and Cancer Center, University of New Mexico Center for Molecular Discovery, and
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7
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Li W, Wang G, Liang W, Kang K, Guo K, Zhang Y. Integrin β3 is required in infection and proliferation of classical swine fever virus. PLoS One 2014; 9:e110911. [PMID: 25340775 PMCID: PMC4207786 DOI: 10.1371/journal.pone.0110911] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/24/2014] [Indexed: 12/25/2022] Open
Abstract
Classical Swine Fever (CSF) is a highly infectious fatal pig disease, resulting in huge economic loss to the swine industry. Integrins are membrane-bound signal mediators, expressed on a variety of cell surfaces and are known as receptors or co-receptors for many viruses. However, the role of integrin β3 in CSFV infection is unknown. Here, through quantitive PCR, immunofluorescence (IFC) and immunocytohistochemistry (ICC), we revealed that ST (swine testicles epithelial) cells have a prominent advantage in CSFV proliferation as compared to EC (swine umbilical vein endothelial cell), IEC (swine intestinal epithelial cell) and PK (porcine kidney epithelial) cells. Meanwhile, ST cells had remarkably more integrin β3 expression as compared to EC, IEC and PK cells, which was positively correlated with CSFV infection and proliferation. Integrin β3 was up-regulated post CSFV infection in all the four cell lines, while the CSFV proliferation rate was decreased in integrin β3 function-blocked cells. ShRNA1755 dramatically decreased integrin β3, with a deficiency of 96% at the mRNA level and 80% at the protein level. CSFV proliferation was dramatically reduced in integrin β3 constantly-defected cells (ICDC), with the deficiencies of 92.6%, 99% and 81.7% at 24 h, 48 h and 72 h post CSFV infection, respectively. These results demonstrate that integrin β3 is required in CSFV infection and proliferation, which provide a new insight into the mechanism of CSFV infection.
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Affiliation(s)
- Weiwei Li
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Gang Wang
- Jiangsu Key Laboratory of Biological Cancer Therapy, Xuzhou Medical College, Xuzhou, Jiangsu, China
| | - Wulong Liang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Kai Kang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Kangkang Guo
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Yanming Zhang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- * E-mail:
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8
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Chigaev A, Sklar LA. Aspects of VLA-4 and LFA-1 regulation that may contribute to rolling and firm adhesion. Front Immunol 2012; 3:242. [PMID: 22876249 PMCID: PMC3410440 DOI: 10.3389/fimmu.2012.00242] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 07/18/2012] [Indexed: 01/21/2023] Open
Abstract
Very Late Antigen-4 (CD49d/CD29, alpha4 beta1) and Lymphocyte Function-associated Antigen-1 (CD11a/CD18, alphaL beta2) integrins are representatives of a large family of adhesion receptors widely expressed on immune cells. They participate in cell recruitment to sites of inflammation, as well as multiple immune cell interactions. A unique feature of integrins is that integrin-dependent cell adhesion can be rapidly and reversibly modulated in response to cell signaling, because of a series of conformational changes within the molecule, which include changes in the affinity of the ligand binding pocket, molecular extension (unbending) and others. Here, we provide a concise comparative analysis of the conformational regulation of the two integrins with specific attention to the physiological differences between these molecules. We focus on recent data obtained using a novel technology, based on small fluorescent ligand-mimicking probes for the detection of integrin conformation in real-time on live cells at natural receptor abundance.
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Affiliation(s)
- Alexandre Chigaev
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque NM, USA
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9
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Abstract
Lymphocyte function-associated antigen-1 (LFA-1) is a heterodimeric integrin consisting of αL (gene name, Itgal) and β2 (gene name, Itgb2) subunits expressed in all leukocytes. LFA-1 is essential for neutrophil recruitment to inflamed tissue. Activation of LFA-1 by chemokines allows neutrophils and other leukocytes to undergo arrest, resulting in firm adhesion on endothelia expressing intercellular adhesion molecules (ICAMs). In mice, CXCR2 is the primary chemokine receptor involved in triggering neutrophil arrest, and it does so through “inside-out” activation of LFA-1. CXCR2 signaling induces changes in LFA-1 conformation that are coupled to affinity upregulation of the ligand-binding headpiece (extended with open I domain). Unlike naïve lymphocytes, engagement of P-selectin glycoprotein ligand-1 (PSGL-1) on neutrophils stimulates a slow rolling behavior that is mediated by LFA-1 in a distinct activation state (extended with closed I domain). How inside-out signaling cascades regulate the structure and function of LFA-1 is being studied using flow chambers, intravital microscopy, and flow cytometry for ligand and reporter antibody binding. Here, we review how LFA-1 activation is regulated by cellular signaling and ligand binding. Two FERM domain-containing proteins, talin-1 and Kindlin-3, are critical integrin co-activators and have distinct roles in the induction of LFA-1 conformational rearrangements. This review integrates these new results into existing models of LFA-1 activation.
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Affiliation(s)
- Craig T Lefort
- Division of Inflammation Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA
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10
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Abstract
Integrins play critical adhesion and signaling roles during development, wound healing, immunity, and cancer. Central to their function is a unique ability to dynamically modulate their adhesiveness and signaling properties through changes in conformation, both homo- and heterotypic protein-protein interactions and cellular distribution. Genetic, biochemical and structural studies have been instrumental in uncovering overall functions, describing ligand and regulatory protein interactions and elucidating the molecular architecture of integrins. However, such approaches alone are inadequate to describe how dynamic integrin behaviors are orchestrated in intact cells. To fill this void, a wide array of distinct light microscopy (largely fluorescence-based) imaging approaches have been developed and employed. Various microscopy technologies, including wide-field, optical sectioning (laser-scanning confocal, spinning-disk confocal, and multiphoton), TIRF and range of novel "Super-Resolution" techniques have been used in combination with diverse imaging modalities (such as IRM, FRET, FRAP, CALI, and fluorescence speckle imaging) to address distinct aspects of integrin function and regulation. This chapter provides an overview of these imaging approaches and how they have advanced our understanding of integrins.
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Affiliation(s)
- Christopher V Carman
- Center for Vascular Biology Research, Division of Molecular and Vascular Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
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11
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Chigaev A, Smagley Y, Zhang Y, Waller A, Haynes MK, Amit O, Wang W, Larson RS, Sklar LA. Real-time analysis of the inside-out regulation of lymphocyte function-associated antigen-1 revealed similarities to and differences from very late antigen-4. J Biol Chem 2011; 286:20375-86. [PMID: 21515675 PMCID: PMC3121518 DOI: 10.1074/jbc.m110.206185] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Ten years ago, we introduced a fluorescent probe that shed light on the inside-out regulation of one of the major leukocyte integrins, very late antigen-4 (VLA-4, CD49d/CD29). Here we describe the regulation of another leukocyte integrin, lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18) using a novel small fluorescent probe in real time on live cells. We found that multiple signaling mechanisms regulate LFA-1 conformation in a manner analogous to VLA-4. LFA-1 can be rapidly activated by Gαi-coupled G protein-coupled receptors (GPCRs) and deactivated by Gαs-coupled GPCRs. The effects of Gαs-coupled GPCR agonists can be reversed in real time by receptor-specific antagonists. The specificity of the fluorescent probe binding has been assessed in a competition assay using the natural LFA-1 ligand ICAM-1 and the LFA-1-specific α I allosteric antagonist BIRT0377. Similar to VLA-4 integrin, modulation of the ligand dissociation rate can be observed for different LFA-1 affinity states. However, we also found a striking difference in the binding of the small fluorescent ligand. In the absence of inside-out activation ligand, binding to LFA-1 is extremely slow, at least 10 times slower than expected for diffusion-limited binding. This implies that an additional structural mechanism prevents ligand binding to inactive LFA-1. We propose that such a mechanism explains the inability of LFA-1 to support cell rolling, where the absence of its rapid engagement by a counterstructure in the inactive state leads to a requirement for a selectin-mediated rolling step.
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Affiliation(s)
- Alexandre Chigaev
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131, USA.
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12
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Abstract
Interaction of the integrin receptors with ligands determines the molecular basis of integrin-dependent cell adhesion. Integrin ligands are typically large proteins with relatively low binding affinities. This makes direct ligand-binding kinetic measurements somewhat difficult. Here we examine several real-time methods, aimed to overcome these experimental limitations and to distinguish the regulation of integrin conformation and affinity. This chapter includes: the use of a small ligand-mimetic probe for studies of inside-out regulation of integrin affinity and unbending, real-time cell aggregation and disaggregation kinetics to probe integrin conformational states and the number of integrin-ligand bonds, as well as the real-time monitoring of ligand-induced epitopes under signaling through G-protein-coupled receptors, and others. Experimental data obtained using these novel methods are summarized in terms of the current model of integrin activation.
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Affiliation(s)
- Alexandre Chigaev
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
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13
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Buranda T, Wu Y, Perez D, Chigaev A, Sklar LA. Real-time partitioning of octadecyl rhodamine B into bead-supported lipid bilayer membranes revealing quantitative differences in saturable binding sites in DOPC and 1:1:1 DOPC/SM/cholesterol membranes. J Phys Chem B 2010; 114:1336-49. [PMID: 20043651 DOI: 10.1021/jp906648q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quantitative analysis of the staining of cell membranes with the cationic amphiphile, octadecyl rhodamine B (R18), is confounded by probe aggregation and changes to the probes' absorption cross section and emission quantum yield. In this paper, flow cytometry, quantum-dot-based fluorescence calibration beads, and FRET were used to examine real-time transfer of R18 from water to two limiting models of the cellular plasma membrane, namely, a single-component disordered membrane, dioleoyl-L-alpha-phosphatidylcholine (DOPC), and a ternary mixture of DOPC, cholesterol, and sphingomyelin (DSC) membranes, reconstituted on spherical and monodisperse glass beads (lipobeads). The quenching of R18 was analyzed as the probe concentration was raised from 0 to 10 mol % in membranes. The data show a > 2-fold enhancement in the quenching level of the probes that were reconstituted in DSC relative to DOPC membranes at the highest concentration of R18. We have parametrized the propagation of concentration-dependent quenching as a function of real-time binding of R18 to lipobeads. In this way, phenomenological kinetics of serum-albumin-mediated transfer of R18 from the aqueous phase to DOPC and DSC membranes could be evaluated under optimal conditions where the critical aggregation concentration (CAC) of the probe is defined as 14 nM. The mass action kinetics of association of R18 with DOPC and DSC lipobeads are shown to be similar. However, the saturable capacity for accepting exogenous probes is found to be 37% higher in DOPC relative to that for DSC membranes. The difference is comparable to the disparity in the average molecular areas of DOPC and DSC membranes. Finally, this analysis shows little difference in the spectral overlap integrals of the emission spectrum of a fluorescein derivative donor and the absorption spectrum of either monomeric or simulated spectrum of dimeric R18. This approach represents a first step toward a nanoscale probing of membrane heterogeneity in living cells by analyzing differential local FRET among sites of unique receptor expression in living cells.
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Affiliation(s)
- Tione Buranda
- Department of Pathology and Cancer Center, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA.
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14
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Lefort CT, Hyun YM, Schultz JB, Law FY, Waugh RE, Knauf PA, Kim M. Outside-in signal transmission by conformational changes in integrin Mac-1. THE JOURNAL OF IMMUNOLOGY 2009; 183:6460-8. [PMID: 19864611 DOI: 10.4049/jimmunol.0900983] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Intracellular signals associated with or triggered by integrin ligation can control cell survival, differentiation, proliferation, and migration. Despite accumulating evidence that conformational changes regulate integrin affinity to its ligands, how integrin structure regulates signal transmission from the outside to the inside of the cell remains elusive. Using fluorescence resonance energy transfer, we addressed whether conformational changes in integrin Mac-1 are sufficient to transmit outside-in signals in human neutrophils. Mac-1 conformational activation induced by ligand occupancy or activating Ab binding, but not integrin clustering, triggered similar patterns of intracellular protein tyrosine phosphorylation, including Akt phosphorylation, and inhibited spontaneous neutrophil apoptosis, indicating that global conformational changes are critical for Mac-1-dependent outside-in signal transduction. In neutrophils and myeloid K562 cells, ligand ICAM-1 or activating Ab binding promoted switchblade-like extension of the Mac-1 extracellular domain and separation of the alpha(M) and beta(2) subunit cytoplasmic tails, two structural hallmarks of integrin activation. These data suggest the primacy of global conformational changes in the generation of Mac-1 outside-in signals.
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Affiliation(s)
- Craig T Lefort
- Department of Microbiology and Immunology, David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, NY 14642, USA
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15
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Njus BH, Chigaev A, Waller A, Wlodek D, Ostopovici-Halip L, Ursu O, Wang W, Oprea TI, Bologa CG, Sklar LA. Conformational mAb as a tool for integrin ligand discovery. Assay Drug Dev Technol 2009; 7:507-15. [PMID: 19754304 PMCID: PMC3096548 DOI: 10.1089/adt.2009.0203] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
alpha(4)beta(1)-Integrin (very late antigen-4 (VLA-4)) mediates cell adhesion to cell surface ligands (VCAM-1). Binding of VLA-4 to VCAM-1 initiates rolling and firm adhesion of leukocytes to vascular endothelium followed by the extravasation into the tissue. VLA-4-dependent adhesion plays a key role in controlling leukocyte adhesive events. Small molecules that bind to the integrin ligand-binding site and block its interaction with natural ligands represent promising candidates for treatment of several diseases. Following a flow cytometric screen for small molecule discovery, we took advantage of a conformationally sensitive anti-beta(1)-integrin antibody (HUTS-21) and a small LDV-containing ligand (LDV-FITC) with known affinity to study binding affinities of several known and recently discovered integrin ligands. We found that binding of the LDV-containing small molecule induced exposure of HUTS-21 epitope and that the EC(50) for antibody binding was equal to previously reported K(d) for fluorescent LDV (LDV-FITC). Thus, binding of HUTS-21 can be used to report ligand-binding site occupancy. We studied binding of two known integrin ligands (YLDV and TR14035), as well as of two novel compounds. EC(50) values for HUTS-21 binding showed good correlation with K(i)s determined in the competition assay with LDV-FITC for all ligands. A docking model suggests a common mode of binding for the small molecule VLA-4 ligands. This novel approach described here can be used to determine ligand-binding affinities for unlabeled integrin ligands, and can be adapted to a high-throughput screening format for identification of unknown integrin ligands.
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Affiliation(s)
- Ben H. Njus
- Department of Chemistry, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Alexandre Chigaev
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Anna Waller
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Danuta Wlodek
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Liliana Ostopovici-Halip
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
- Romanian Academy—Institute of Chemistry, Timisoara, Romania.
| | - Oleg Ursu
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Wei Wang
- Department of Chemistry, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Tudor I. Oprea
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Cristian G. Bologa
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
| | - Larry A. Sklar
- Department of Pathology and Cancer Center, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
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16
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Lefort CT, Kim M. Chapter 12 Fluorescence Resonance Energy Transfer in the Studies of Integrin Activation. CURRENT TOPICS IN MEMBRANES 2009. [DOI: 10.1016/s1063-5823(09)64012-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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17
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Roda A, Guardigli M, Michelini E, Mirasoli M. Nanobioanalytical luminescence: Förster-type energy transfer methods. Anal Bioanal Chem 2008; 393:109-23. [DOI: 10.1007/s00216-008-2435-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 09/22/2008] [Accepted: 09/23/2008] [Indexed: 12/21/2022]
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18
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Tang ML, Vararattanavech A, Tan SM. Urokinase-type plasminogen activator receptor induces conformational changes in the integrin alphaMbeta2 headpiece and reorientation of its transmembrane domains. J Biol Chem 2008; 283:25392-25403. [PMID: 18644795 DOI: 10.1074/jbc.m802311200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The glycosylphosphatidylinositol-linked urokinase-type plasminogen activator receptor (uPAR) interacts with the heterodimer cell adhesion molecules integrins to modulate cell adhesion and migration. Devoid of a cytoplasmic domain, uPAR triggers intracellular signaling via its associated molecules that contain cytoplasmic domains. Interestingly, uPAR changes the ectodomain conformation of one of its partner molecules, integrin alpha(5)beta(1), and elicits cytoplasmic signaling. The separation or reorientation of integrin transmembrane domains and cytoplasmic tails are required for integrin outside-in signaling. However, there is a lack of direct evidence showing these conformational changes of an integrin that interacts with uPAR. In this investigation we used reporter monoclonal antibodies and fluorescence resonance energy transfer analyses to show conformational changes in the alpha(M)beta(2) headpiece and reorientation of its transmembrane domains when alpha(M)beta(2) interacts with uPAR.
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Affiliation(s)
- Man-Li Tang
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, 637551, Singapore
| | - Ardcharaporn Vararattanavech
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, 637551, Singapore
| | - Suet-Mien Tan
- Division of Molecular and Cell Biology, School of Biological Sciences, Nanyang Technological University, 637551, Singapore.
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Iskandarsyah, Tejo BA, Tambunan USF, Verkhivker G, Siahaan TJ. Structural modifications of ICAM-1 cyclic peptides to improve the activity to inhibit heterotypic adhesion of T cells. Chem Biol Drug Des 2008; 72:27-33. [PMID: 18554252 DOI: 10.1111/j.1747-0285.2008.00676.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1) interaction plays an important role in the formation of the immunological synapse between T cells and antigen-presenting cells. Blocking of LFA-1/ICAM-1 interactions has been shown to suppress the progression of autoimmune diseases. cIBR peptide (cyclo(1,12)PenPRGGSVLVTGC) inhibits ICAM-1/LFA-1 interaction by binding to the I-domain of LFA-1. To increase the bioactivity of cIBR peptide, we systemically modified the structure of the peptide by (i) replacing the Pen residue at the N-terminus with Cys, (ii) cyclization using amide bond formation between Lys-Glu side chains, and (iii) reducing the peptide size by eliminating the C-terminal residue. We found that the activity of cIBR peptide was not affected by replacing Phe with Cys. Peptide cyclization by forming the Lys-Glu amide bond also increased the activity of cIBR peptide, presumably due to the resistance of the amide bond to the reducing nature of glutathione in plasma. We also found that a reduced derivative of cIBR with eight residues (cyclo(1,8)CPRGGSVC) has a bioactivity similar to that of the larger cIBR peptides. Our findings suggest that, by systemically modifying the structure of cIBR peptide, the biological activity of these derivatives can be optimized for future use to inhibit T-cell adhesion in in vivo models of autoimmune diseases.
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Affiliation(s)
- Iskandarsyah
- Department of Pharmaceutical Chemistry, The University of Kansas, 2095 Constant Avenue, Lawrence, KS 66047, USA
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20
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Chigaev A, Waller A, Amit O, Sklar LA. Galphas-coupled receptor signaling actively down-regulates alpha4beta1-integrin affinity: a possible mechanism for cell de-adhesion. BMC Immunol 2008; 9:26. [PMID: 18534032 PMCID: PMC2442041 DOI: 10.1186/1471-2172-9-26] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 06/05/2008] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Activation of integrins in response to inside-out signaling serves as a basis for leukocyte arrest on endothelium, and migration of immune cells. Integrin-dependent adhesion is controlled by the conformational state of the molecule (i.e. change in the affinity for the ligand and molecular unbending (extension)), which is regulated by seven-transmembrane Guanine nucleotide binding Protein-Coupled Receptors (GPCRs). alpha4beta1-integrin (CD49d/CD29, Very Late Antigen-4, VLA-4) is expressed on leukocytes, hematopoietic stem cells, hematopoietic cancer cells, and others. Affinity and extension of VLA-4 are both rapidly up-regulated by inside-out signaling through several Galphai-coupled GPCRs. The goal of the current report was to study the effect of Galphas-coupled GPCRs upon integrin activation. RESULTS Using real-time fluorescent ligand binding to assess affinity and a FRET based assay to probe alpha4beta1-integrin unbending, we show that two Galphas-coupled GPCRs (H2-histamine receptor and beta2-adrenergic receptor) as well as several cAMP agonists can rapidly down modulate the affinity of VLA-4 activated through two Galphai-coupled receptors (CXCR4 and FPR) in U937 cells and primary human peripheral blood monocytes. This down-modulation can be blocked by receptor-specific antagonists. The Galphas-induced responses were not associated with changes in the expression level of the Galphai-coupled receptors. In contrast, the molecular unbending of VLA-4 was not significantly affected by Galphas-coupled GPCR signaling. In a VLA-4/VCAM-1-specific myeloid cell adhesion system, inhibition of the VLA-4 affinity change by Galphas-coupled GPCR had a statistically significant effect upon cell aggregation. CONCLUSION We conclude that Galphas-coupled GPCRs can rapidly down modulate the affinity state of VLA-4 binding pocket through a cAMP dependent pathway. This plays an essential role in the regulation of cell adhesion. We discuss several possible implications of this described phenomenon.
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Affiliation(s)
- Alexandre Chigaev
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.
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21
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Tang XY, Li YF, Tan SM. Intercellular adhesion molecule-3 binding of integrin alphaL beta2 requires both extension and opening of the integrin headpiece. THE JOURNAL OF IMMUNOLOGY 2008; 180:4793-804. [PMID: 18354203 DOI: 10.4049/jimmunol.180.7.4793] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The leukocyte-restricted integrin alpha(L)beta(2) is required in immune processes such as leukocyte adhesion, migration, and immune synapse formation. Activation of alpha(L)beta(2) by conformational changes promotes alpha(L)beta(2) binding to its ligands, ICAMs. It was reported that different affinity states of alpha(L)beta(2) are required for binding ICAM-1 and ICAM-3. Recently, the bent, extended with a closed headpiece, and extended with open headpiece conformations of alpha(L)beta(2), was reported. To address the overall conformational requirements of alpha(L)beta(2) that allow selective binding of these ICAMs, we examined the adhesion properties of these alpha(L)beta(2) conformers. alpha(L)beta(2) with different conformations were generated by mutations, and verified by using a panel of reporter mAbs that detect alpha(L)beta(2) extension, hybrid domain movement, or I-like domain activation. We report a marked difference between extended alpha(L)beta(2) with closed and open headpieces in their adhesive properties to ICAM-1 and ICAM-3. Our data show that the extension of alpha(L)beta(2) alone is sufficient to mediate ICAM-1 adhesion. By contrast, an extended alpha(L)beta(2) with an open headpiece is required for ICAM-3 adhesion.
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Affiliation(s)
- Xiao-Yan Tang
- School of Biological Sciences, Nanyang Technological University, Singapore
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22
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Poria RB, Norenberg JP, Anderson TL, Erion J, Wagner CR, Arterburn JB, Larson RS. Characterization of a radiolabeled small molecule targeting leukocyte function-associated antigen-1 expression in lymphoma and leukemia. Cancer Biother Radiopharm 2007; 21:418-26. [PMID: 17105416 DOI: 10.1089/cbr.2006.21.418] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE Leukocyte function-associated antigen-1 (LFA-1) is constitutively expressed on leukocytes, including overexpression on lymphomas and leukemias. We have developed a derivative of BIRT 377, an allosteric inhibitor of LFA-1, which may be chemically tagged without affecting binding. In this study, we modified this derivative, (R)-1-(4-aminobutyl)-5-(4-bromobenzyl)-3-(3,5-dichlorophenyl)-5-methylimidazolidine- 2,4-dione (butylamino-NorBIRT), and demonstrated its potential as a noninvasive imaging agent. METHODS Specific binding of fluorescein-labeled butylamino-NorBIRT to both human and murine cells was demonstrated using equilibrium binding and dissociation techniques. A radiometal, lutetium-177 (Lu-177), was incorporated into the butylamino-NorBIRT through 1,4,7,10-tetraazacyclododecane-N,N',N",N'''- tetraacetic acid (DOTA) as a chelator. RESULTS Equilibrium-binding experiments demonstrated that fluorescein- labeled butylamino-NorBIRT specifically binds human and murine LFA-1 with affinity constants of 135 and 186 nM, respectively. Dissociation kinetic experiments demonstrated an off-rate of 0.168/second(1) on murine cells, consistent with the observed affinity constant. Lutetium-177 was used for labeling, with > or =99.99% radiochemical purity and incorporation yield. This radiolabeled derivative exhibited high stability in fetal bovine serum (FBS) at 37 degrees C over 72 hours. (177)Lu-DOTA-butylamino-NorBIRT showed a binding affinity of 235 nM to human LFA-1 for equilibrium binding and competitive binding experiments. CONCLUSIONS The radiolabeled DOTA-butylamino-NorBIRT may have potential as a noninvasive imaging or therapeutic agent in both human and mouse models.
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Affiliation(s)
- Rahul B Poria
- Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
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23
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Kinashi T. Integrin Regulation of Lymphocyte Trafficking: Lessons from Structural and Signaling Studies. Adv Immunol 2007; 93:185-227. [PMID: 17383542 DOI: 10.1016/s0065-2776(06)93005-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
High trafficking capability of lymphocytes is crucial in immune surveillance and antigen responses. Central to this regulatory process is a dynamic control of lymphocyte adhesion behavior regulated by chemokines and adhesion receptors such as integrins. Modulation of lymphocyte adhesive responses occurs in a wide range of time window from less than a second to hours, enabling rolling lymphocyte to attach to and migrate through endothelium and interact with antigen-presenting cells. While there has been a rapid progress in the understanding of integrin structure, elucidation of signaling events to relay extracellular signaling to integrins in physiological contexts has recently emerged from studies using gene-targeting and gene-silencing technique. Regulatory molecules critical for integrin activity control distribution of integrins, polarized cell morphology and motility, suggesting a signaling network that coordinates integrin function with lymphocyte migration. Here, I review recent studies of integrin structural changes and intracellular signal molecules that trigger integrin activation (inside-out signals), and discuss molecular mechanisms that control lymphocyte integrins and how inside-out signals coordinately modulate adhesive reactions and cell shape and migration.
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Affiliation(s)
- Tatsuo Kinashi
- Department of Molecular Genetics, Institute of Biomedical Science, Kansai Medical University, Kyoto 606, Japan
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24
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Abstract
Fluorescence resonance energy transfer (FRET) has been proven to be a powerful tool to visualize and quantify the signaling cascades in live cells with high spatiotemporal resolutions. Here we describe the development of the genetically encoded and FRET-based biosensors for imaging of integrin-related signaling cascades. The construction of a FRET biosensor for Src kinase, an important tyrosine kinase involved in integrin-related signaling pathways, is used as an example to illustrate the construction procedure and the pitfalls involved. The design strategies and considerations on improvements of sensitivity and specificity are also discussed. The FRET-based biosensors provide a complementary approach to traditional biochemical assays for the analysis of the functions of integrins and their associated signaling molecules. The dynamic and subcellular visualization enabled by FRET can shed new light on the molecular mechanisms regulating integrin signaling and advance our knowledge in the understanding of integrin-related pathophysiological processes.
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Affiliation(s)
- Yingxiao Wang
- Department of Bioengineering and Molecular & Integrative Physiology, Neuroscience Program, Center for Biophysics and Computational Biology, Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, USA
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25
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Sapsford KE, Berti L, Medintz IL. Materialien für den resonanten Fluoreszenzenergietransfer (FRET): jenseits klassischer Donor-Acceptor-Kombinationen. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200503873] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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26
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Sapsford KE, Berti L, Medintz IL. Materials for Fluorescence Resonance Energy Transfer Analysis: Beyond Traditional Donor–Acceptor Combinations. Angew Chem Int Ed Engl 2006; 45:4562-89. [PMID: 16819760 DOI: 10.1002/anie.200503873] [Citation(s) in RCA: 1028] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The use of Förster or fluorescence resonance energy transfer (FRET) as a spectroscopic technique has been in practice for over 50 years. A search of ISI Web of Science with just the acronym "FRET" returns more than 2300 citations from various areas such as structural elucidation of biological molecules and their interactions, in vitro assays, in vivo monitoring in cellular research, nucleic acid analysis, signal transduction, light harvesting and metallic nanomaterials. The advent of new classes of fluorophores including nanocrystals, nanoparticles, polymers, and genetically encoded proteins, in conjunction with ever more sophisticated equipment, has been vital in this development. This review gives a critical overview of the major classes of fluorophore materials that may act as donor, acceptor, or both in a FRET configuration. We focus in particular on the benefits and limitations of these materials and their combinations, as well as the available methods of bioconjugation.
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Affiliation(s)
- Kim E Sapsford
- Center for Bio/Molecular Science and Engineering, U.S. Naval Research Laboratory, Code 6910, 4555 Overlook Avenue SW, Washington, DC 20375, USA
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Anderson ME, Tejo BA, Yakovleva T, Siahaan TJ. Characterization of Binding Properties of ICAM-1 Peptides to LFA-1: Inhibitors of T-cell Adhesion. Chem Biol Drug Des 2006; 68:20-8. [PMID: 16923022 DOI: 10.1111/j.1747-0285.2006.00407.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the present study, we characterized the binding site of two intercellular adhesion molecule-1-derived cyclic peptides, cIBC and cIBR, to the LFA-1 on the surface of T cells. These peptides had been able to inhibit LFA-1/intercellular adhesion molecule-1 signal by blocking the signal-2 of immune synapse. Both peptides prefer to bind to the closed form of LFA-1 I-domain, indicating that two peptides act as allosteric inhibitors against intercellular adhesion molecule-1. Binding site mapping using monoclonal antibodies proposes that cIBC binds to around residues 266-272 of LFA-1 I-domain where this site is adjacent to the metal ion-dependent adhesion site. On the other hand, cIBR binds to the pocket called L-site where is distant from metal ion-dependent adhesion site. Cross-inhibition mapping between two peptides show that cIBR could inhibit the binding of cIBC but not vice versa, suggesting that cIBR has some properties that allow this peptide bind to more than one site. Structural comparison between cIBC and cIBR reveals that cIBR is more flexible than cIBC, allowing this peptide bind to exposed region, such as cIBC-binding site as well as cramped pocket like L-site. Our findings are important for understanding the selectivity of cIBC and cIBR peptides; thus, they can be conjugated with drugs and transported specifically to the target.
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Affiliation(s)
- Meagan E Anderson
- Department of Pharmaceutical Chemistry, The University of Kansas, 2095 Constant Ave, Lawrence, KS 66047, USA
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Staunton DE, Lupher ML, Liddington R, Gallatin WM. Targeting integrin structure and function in disease. Adv Immunol 2006; 91:111-57. [PMID: 16938539 DOI: 10.1016/s0065-2776(06)91003-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Initially linked to the pathogenesis of inflammatory and hematologic diseases, integrins have become validated drug targets with the approval of five drugs. Moreover, there are several promising drug candidates in preclinical and clinical stages of development for multiple clinical indications. Integrins are attractive drug targets as their antagonism can block several steps in disease progression or maintenance. Integrin inhibitors can block the proliferation, migration, or tissue localization of inflammatory, angiogenic, and tumor cells, as well as signaling and gene expression contributing to disease. There has been a rapid increase in the elucidation of integrin structure, their allosteric mechanisms of bidirectional signaling, and the structure of complexes with drugs. This information brings greater focus to how integrins support various cellular functions and how they have been and may be targeted to develop novel drugs. Here we review conformational switches, including an internal ligand, which allosterically regulate the transition from low- to high-affinity ligand binding. We address some of the successes, disappointments, and challenges in targeting competitive or allosteric sites to develop therapeutics. We also discuss new opportunities, including a structure-based approach to discover novel drugs to treat inflammatory and other diseases. This approach targets structural relatives of the von Willebrand factor A-domain present in integrins and many functionally diverse proteins.
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