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Benk LT, Benk AS, Lira RB, Cavalcanti-Adam EA, Dimova R, Lipowsky R, Geiger B, Spatz JP. Integrin α
IIb
β
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Activation and Clustering in Minimal Synthetic Cells. ADVANCED NANOBIOMED RESEARCH 2022. [DOI: 10.1002/anbr.202100094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Lucia T. Benk
- Department of Cellular Biophysics Max Planck Institute for Medical Research Jahnstr. 29 69120 Heidelberg Germany
| | - Amelie S. Benk
- Department of Cellular Biophysics Max Planck Institute for Medical Research Jahnstr. 29 69120 Heidelberg Germany
| | - Rafael B. Lira
- Theory & Bio-Systems Max Planck Institute of Colloids and Interfaces 14424 Potsdam Germany
- Faculty of Science and Engineering Molecular Biophysics Zernike Institute for Advanced Materials 9747 AG Groningen The Netherlands
| | - Elisabetta Ada Cavalcanti-Adam
- Department of Cellular Biophysics Max Planck Institute for Medical Research Jahnstr. 29 69120 Heidelberg Germany
- Max Planck School Matter to Life Jahnstr. 29 69120 Heidelberg Germany
| | - Rumiana Dimova
- Theory & Bio-Systems Max Planck Institute of Colloids and Interfaces 14424 Potsdam Germany
| | - Reinhard Lipowsky
- Theory & Bio-Systems Max Planck Institute of Colloids and Interfaces 14424 Potsdam Germany
- Max Planck School Matter to Life Jahnstr. 29 69120 Heidelberg Germany
| | - Benjamin Geiger
- Department of Molecular Cell Biology Weizmann Institute of Science Rehovot 76100 Israel
| | - Joachim P. Spatz
- Department of Cellular Biophysics Max Planck Institute for Medical Research Jahnstr. 29 69120 Heidelberg Germany
- Max Planck School Matter to Life Jahnstr. 29 69120 Heidelberg Germany
- Institute for Molecular Systems Engineering (IMSE) Heidelberg University 69120 Heidelberg Germany
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Tobi D, Krashin E, Davis PJ, Cody V, Ellis M, Ashur-Fabian O. Three-Dimensional Modeling of Thyroid Hormone Metabolites Binding to the Cancer-Relevant αvβ3 Integrin: In-Silico Based Study. Front Endocrinol (Lausanne) 2022; 13:895240. [PMID: 35692387 PMCID: PMC9186291 DOI: 10.3389/fendo.2022.895240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 04/26/2022] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Thyroid hormones (TH), T4 and T3, mediate pro-mitogenic effects in cancer cells through binding the membrane receptor αvβ3 integrin. The deaminated analogue tetrac effectively blocks TH binding to this receptor and prevents their action. While computational data on TH binding to the αvβ3 integrin was published, a comprehensive analysis of additional TH metabolites is lacking. METHODS In-silico docking of 26 TH metabolites, including the biologically active thyroid hormones (T3 and T4) and an array of sulfated, deiodinated, deaminated or decarboxylated metabolites, to the αvβ3 receptor binding pocket was performed using DOCK6, based on the three-dimensional representation of the crystallographic structure of the integrin. As the TH binding site upon the integrin is at close proximity to the well-defined RGD binding site, linear and cyclic RGD were included as a reference. Binding energy was calculated for each receptor-ligand complex using Grid score and Amber score with distance movable region protocol. RESULTS All TH molecules demonstrated negative free energy, suggesting affinity to the αvβ3 integrin. Notably, based on both Grid and Amber scores sulfated forms of 3,3' T2 (3,3' T2S) and T4 (T4S) demonstrated the highest binding affinity to the integrin, compared to both cyclic RGD and an array of examined TH metabolites. The major thyroid hormones, T3 and T4, showed high affinity to the integrin, which was superior to that of linear RGD. For all hormone metabolites, decarboxylation led to decreased affinity. This corresponds with the observation that the carboxylic group mediates binding to the integrin pocket via divalent cations at the metal-ion-dependent adhesion (MIDAS) motif site. A similar reduced affinity was documented for deaminated forms of T3 (triac) and T4 (tetrac). Lastly, the reverse forms of T3, T3S, and T3AM showed higher Amber scores relative to their native form, indicating that iodination at position 5 is associated with increased binding affinity compared to position 5'. SUMMARY Three-dimensional docking of various TH metabolites uncovered a structural basis for a differential computational free energy to the αvβ3 integrin. These findings may suggest that naturally occurring endogenous TH metabolites may impact integrin-mediate intracellular pathways in physiology and cancer.
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Affiliation(s)
- Dror Tobi
- Department of Molecular Biology, Ariel University, Ariel, Israel
- Department of Computer Sciences, Ariel University, Ariel, Israel
- *Correspondence: Osnat Ashur-Fabian, ; Dror Tobi,
| | - Eilon Krashin
- Translational Oncology Laboratory, Meir Medical Center, Kfar-Saba, Israel
- Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Paul J. Davis
- Department of Medicine, Albany Medical College, Albany, NY, United States
- Pharmaceutical Research Institute, Albany College of Pharmacy and Health Sciences, Albany, NY, United States
| | - Vivian Cody
- Hauptman-Woodward Medical Research Institute & Department of Structural Biology, SUNY, University at Buffalo, Buffalo, NY, United States
| | - Martin Ellis
- Translational Oncology Laboratory, Meir Medical Center, Kfar-Saba, Israel
- Hematology Institute and Blood Bank, Meir Medical Center, Kfar-Saba, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Osnat Ashur-Fabian
- Translational Oncology Laboratory, Meir Medical Center, Kfar-Saba, Israel
- Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- Hematology Institute and Blood Bank, Meir Medical Center, Kfar-Saba, Israel
- *Correspondence: Osnat Ashur-Fabian, ; Dror Tobi,
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Slow Freezing Versus Vitrification of Mouse Ovaries: from Ex Vivo Analyses to Successful Pregnancies after Auto-Transplantation. Sci Rep 2019; 9:19668. [PMID: 31873164 PMCID: PMC6928220 DOI: 10.1038/s41598-019-56182-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 11/14/2019] [Indexed: 12/23/2022] Open
Abstract
Slow freezing (SF) is the reference method for ovarian tissue cryopreservation. Vitrification (VT) constitutes an alternative but controversial method. This study compares SF and VT (open [VTo] and closed [VTc] systems) in terms of freezing damage and fertility restoration ability. In vitro analyses of C57Bl/6 SF or VTo-ovaries, immediately after thawing/warming or after culture (cult), revealed that event though follicular density was similar between all groups, nuclear density was decreased in VTo-ovaries compared to CT-ovaries (CT = 0.50 ± 0.012, SF = 0.41 ± 0.03 and VTo = 0.29 ± 0.044, p < 0.01). Apoptosis was higher in VTo-cult ovaries compared to SF-cult ovaries (p < 0.001) whereas follicular Bmp15 and Amh gene expression levels were decreased in the ovaries after culture, mostly after VTo (p < 0.001). Natural mating after auto-transplantation of SF, VTo and VTc-ovaries revealed that most mice recovered their oestrous cycle. Fertility was only restored with SF and VTo ovaries (SF: 68%; VTo: 63%; VTc: 0%; p < 0.001). Mice auto-transplanted with SF and VTo-ovaries achieved the highest number of pregnancies. In conclusion, in vitro, no differences between SF and VTo were evident immediately after thawing/warming but VTo ovaries displayed alterations in apoptosis and follicular specific proteins after culture. In vivo, SF and VTo ovary auto-transplantation fully restored fertility whereas with VTc-ovary auto-transplantation no pregnancies were achieved.
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Raborn J, Fu T, Wu X, Xiu Z, Li G, Luo BH. Variation in one residue associated with the metal ion-dependent adhesion site regulates αIIbβ3 integrin ligand binding affinity. PLoS One 2013; 8:e76793. [PMID: 24116162 PMCID: PMC3792891 DOI: 10.1371/journal.pone.0076793] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 08/29/2013] [Indexed: 01/06/2023] Open
Abstract
The Asp of the RGD motif of the ligand coordinates with the β I domain metal ion dependent adhesion site (MIDAS) divalent cation, emphasizing the importance of the MIDAS in ligand binding. There appears to be two distinct groups of integrins that differ in their ligand binding affinity and adhesion ability. These differences may be due to a specific residue associated with the MIDAS, particularly the β3 residue Ala252 and corresponding Ala in the β1 integrin compared to the analogous Asp residue in the β2 and β7 integrins. Interestingly, mutations in the adjacent to MIDAS (ADMIDAS) of integrins α4β7 and αLβ2 increased the binding and adhesion abilities compared to the wild-type, while the same mutations in the α2β1, α5β1, αVβ3, and αIIbβ3 integrins demonstrated decreased ligand binding and adhesion. We introduced a mutation in the αIIbβ3 to convert this MIDAS associated Ala252 to Asp. By combination of this mutant with mutations of one or two ADMIDAS residues, we studied the effects of this residue on ligand binding and adhesion. Then, we performed molecular dynamics simulations on the wild-type and mutant αIIbβ3 integrin β I domains, and investigated the dynamics of metal ion binding sites in different integrin-RGD complexes. We found that the tendency of calculated binding free energies was in excellent agreement with the experimental results, suggesting that the variation in this MIDAS associated residue accounts for the differences in ligand binding and adhesion among different integrins, and it accounts for the conflicting results of ADMIDAS mutations within different integrins. This study sheds more light on the role of the MIDAS associated residue pertaining to ligand binding and adhesion and suggests that this residue may play a pivotal role in integrin-mediated cell rolling and firm adhesion.
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Affiliation(s)
- Joel Raborn
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
- University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States of America
| | - Ting Fu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, PR China
- Graduate University of the Chinese Academy of Sciences, Beijing, P. R. China
| | - Xue Wu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, PR China
| | - Zhilong Xiu
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, PR China
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China
- * E-mail: (GL); (BL)
| | - Bing-Hao Luo
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
- * E-mail: (GL); (BL)
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Abstract
Integrins are a family of α/β heterodimeric adhesion metalloprotein receptors and their functions are highly dependent on and regulated by different divalent cations. Recently advanced studies have revolutionized our perception of integrin metal ion-binding sites and their specific functions. Ligand binding to integrins is bridged by a divalent cation bound at the MIDAS motif on top of either α I domain in I domain-containing integrins or β I domain in α I domain-less integrins. The MIDAS motif in β I domain is flanked by ADMIDAS and SyMBS, the other two crucial metal ion binding sites playing pivotal roles in the regulation of integrin affinity and bidirectional signaling across the plasma membrane. The β-propeller domain of α subunit contains three or four β-hairpin loop-like Ca(2+)-binding motifs that have essential roles in integrin biogenesis. The function of another Ca(2+)-binding motif located at the genu of α subunit remains elusive. Here, we provide an overview of the integrin metal ion-binding sites and discuss their roles in the regulation of integrin functions.
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Affiliation(s)
- Kun Zhang
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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Narbutt J, Boncela J, Smolarczyk K, Kowalewski C, Wozniak K, Torzecka JD, Sysa-Jedrzejowska A, Cierniewski CS, Lesiak A. Pathogenic activity of circulating anti-desmoglein-3 autoantibodies isolated from pemphigus vulgaris patients. Arch Med Sci 2012; 8:347-56. [PMID: 22662010 PMCID: PMC3361049 DOI: 10.5114/aoms.2012.28564] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 08/05/2010] [Accepted: 08/18/2010] [Indexed: 01/19/2023] Open
Abstract
INTRODUCTION There are scarce data on immunochemical properties of pemphigus antibodies detected in clinical remission in pemphigus vulgaris (PV) patients. The aim of the study was to compare biological activity of anti-Dsg3 autoantibodies purified from the sera of PV patients in active stage and in clinical remission. MATERIAL AND METHODS The effect of purified antibodies on expression of procaspase-3, Bax, Bcl-2, uPAR, IL-1β, IL-6, and TNF-α mRNAs in the HaCaT keratinocytes was evaluated by Western blot and RT-PCR method. RESULTS Incubation of HaCaT cells with anti-Dsg-3 autoantibodies caused their binding to cell membranes surfaces. Anti-Dsg3 autoantibodies isolated from the patients in active stage and clinical remission showed proapoptotic effect, caused enhanced expression of analyzed proinflammatory cytokines' mRNAs and uPAR mRNA. CONCLUSIONS Our data revealed similar pathogenic activity of anti Dsg-3 autoantibodies isolated from active and clinical remission PV patients.
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Affiliation(s)
- Joanna Narbutt
- Department of Dermatology, Medical University of Lodz, Poland
| | - Joanna Boncela
- Centre of Medical Biology, Polish Academy of Sciences, Lodz, Poland
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Pines M, Fairchild MJ, Tanentzapf G. Distinct regulatory mechanisms control integrin adhesive processes during tissue morphogenesis. Dev Dyn 2011; 240:36-51. [PMID: 21089076 DOI: 10.1002/dvdy.22488] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cell adhesion must be precisely regulated to enable both dynamic morphogenetic processes and the subsequent transition to stable tissue maintenance. Integrins link the intracellular cytoskeleton and extracellular matrix, relaying bidirectional signals across the plasma membrane. In vitro studies have demonstrated that multiple mechanisms control integrin-mediated adhesion; however, their roles during development are poorly understood. We used mutations that activate or deactivate specific functions of vertebrate β-integrins in vitro to investigate how perturbing Drosophila βPS-integrin regulation in developing embryos regulation affects tissue morphogenesis and maintenance. We found that morphogenetic processes use various β-integrin regulatory mechanisms to differing degrees and that conformational changes associated with outside-in activation are essential for developmental integrin functions. Long-term adhesion is also sensitive to integrin dysregulation, suggesting integrins must be continuously regulated to support stable tissue maintenance. Altogether, in vivo phenotypic analyses allowed us to identify the importance of various β-integrin regulatory mechanisms during different morphogenetic processes.
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Affiliation(s)
- Mary Pines
- Department of Cellular and Physiological Sciences, University of British Columbia, Life Sciences Institute, Vancouver, BC, Canada
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Murcia M, Jirouskova M, Li J, Coller BS, Filizola M. Functional and computational studies of the ligand-associated metal binding site of beta3 integrins. Proteins 2008; 71:1779-91. [PMID: 18175315 DOI: 10.1002/prot.21859] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A combination of experimental and computational approaches was used to provide a structural context for the role of the beta3 integrin subunit ligand-associated metal binding site (LIMBS) in the binding of physiological ligands to beta3 integrins. Specifically, we have carried out (1) adhesion assays on cells expressing normal alphaIIbeta3, normal alphaVbeta3, or the corresponding beta3 D217A LIMBS mutants; and (2) equilibrium and nonequilibrium (steered) molecular dynamics (MD) simulations of eptifibatide in complex with either a fully hydrated normal alphaIIbeta3 integrin fragment (alphaIIb beta-propeller and the beta3 betaA (I-like), hybrid, and PSI domains) or the equivalent beta3 D217A mutant. Normal alphaIIbeta3 expressing cells adhered to immobilized fibrinogen and echistatin, whereas cells expressing the alphaIIbeta3 D217A LIMBS mutant failed to adhere to either ligand. Similarly, the equivalent alphaVbeta3 mutant was unable to support adhesion to vitronectin or fibrinogen. The alphaIIbeta3 D217A mutation increased the binding of mAb AP5, which recognizes a ligand-induced binding site (LIBS) in the beta3 PSI domain, indicating that this mutation induced allosteric changes in the protein. Steered MD simulating the unbinding of eptifibatide from either normal alphaIIbeta3 or the equivalent beta3 D217A mutant suggested that the reduction in ligand binding caused by the LIMBS mutant required the loss of both the LIMBS and the metal ion-dependent adhesion site (MIDAS) metal ions. Our computational results indicate that the LIMBS plays a crucial role in ligand binding to alphaIIbeta3 by virtue of its effects on the coordination of the MIDAS.
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Affiliation(s)
- Marta Murcia
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, New York 10029-6574, USA
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Swiatkowska M, Szymański J, Padula G, Cierniewski CS. Interaction and functional association of protein disulfide isomerase with alphaVbeta3 integrin on endothelial cells. FEBS J 2008; 275:1813-23. [PMID: 18331351 DOI: 10.1111/j.1742-4658.2008.06339.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Adhesive properties of endothelial cells are influenced by the thioldisulfide balance. However, the molecular mechanism of this effect is unclear, although recent observations indicate that integrin receptors may be direct targets for redox modulation. The purpose of this study was to examine whether protein disulfide isomerase (PDI) is directly involved in this process. As manganese ions are known to affect the thioldisulfide balance and activate integrins to maximal affinity, we searched for PDI interactions with integrins, particularly with alpha(V)beta(3), in Mn(2+)-treated endothelial cells. By employing confocal microscopy, flow cytometry and coimmunoprecipitation experiments, we showed that exposure of endothelial cells to Mn(2+) resulted in: (a) the appearance of surface protein thiol groups, which can be found in PDI and alpha(V)beta(3), and both proteins colocalizing on the cellular surface; and (b) the formation of the PDI-alpha(V)beta(3) complex, which dissociates upon reduction. In addition, PDI in a complex with alpha(V)beta(3) induces conversion of the integrin to the ligand-competent high-affinity state, as evidenced by increased binding of vitronectin. The membrane-impermeable sulfhydryl blockers 3-N-maleimidylpropionyl biocytin 3-N-maleimidylpropionyl biocytin and p-chloromercuriphenyl sulfonate, as well as the PDI inhibitors bacitracin, MA3 018, and MA3 019, abolished the binding of vitronectin and LM609 to endothelial cells that is activated by Mn(2+). Consistently, LM609 almost completely blocked binding of vitronectin to such cells. The formation of the PDI-alpha(V)beta(3) stoichiometric complex was further demonstrated by surface plasmon resonance analysis, which showed that the initial reversible binding of PDI becomes irreversible in the presence of Mn(2+), probably mediated by disulfide bonds. Thus, we show that Mn(2+) simultaneously modulates the thiol isomerase activity of PDI that is bound to alpha(V)beta(3) and induces its transition to the ligand-competent state, suggesting an alternative mechanism of integrin regulation.
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Affiliation(s)
- Maria Swiatkowska
- Department of Molecular and Medical Biophysics, Medical University in Lodz, 6/8 Mazowiecka Street, Lodz, Poland.
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Pesho MM, Bledzka K, Michalec L, Cierniewski CS, Plow EF. The Specificity and Function of the Metal-binding Sites in the Integrin β3 A-domain. J Biol Chem 2006; 281:23034-41. [PMID: 16723352 DOI: 10.1074/jbc.m602856200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The A-domains within integrin beta subunits contain three metal sites termed the metal ion-dependent adhesion site (MIDAS), site adjacent to the metal ion-dependent adhesion site (ADMIDAS), and ligand-induced metal-binding site (LIMBS), and these sites are involved in ligand engagement. The selectivity of these metal sites and their role in ligand binding have been investigated by expressing a fragment corresponding to the beta3 A-domain, beta3-(109-352), and single point mutants in which each of the cation-binding sites has been disabled. Equilibrium dialysis experiments identified three Mn2+- and two Ca2+-binding sites with the LIMBS being the site that did not bind Ca2+. Although the ADMIDAS could bind Ca2+, it did not bind Mg2+. These results indicate that the Ca2+-specific site that inhibits ligand binding is the ADMIDAS. Two different assay systems, surface plasmon resonance and a microtiter plate assay, demonstrated that the beta3 A-domain fragment bound fibrinogen in the presence of 0.1 mm Ca2+ but not in 3 mm Ca2+. This behavior recapitulated the effects of Ca2+ on fibrinogen binding to alphavbeta3 but not alphaIIbbeta3. Disabling any of the three cation-binding sites abrogated fibrinogen binding. These results indicate that the specificities of the three metal-binding sites for divalent cations are distinct and that each site can regulate the ligand binding potential of the beta3 A-domain.
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Affiliation(s)
- Michelle M Pesho
- Joseph J. Jacobs Center for Thrombosis and Vascular Biology and Department of Molecular Cardiology, Cleveland Clinic, Cleveland, Ohio 44195, USA
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Stenina OI, Ustinov V, Krukovets I, Marinic T, Topol EJ, Plow EF. Polymorphisms A387P in thrombospondin-4 and N700S in thrombospondin-1 perturb calcium binding sites. FASEB J 2005; 19:1893-5. [PMID: 16148025 DOI: 10.1096/fj.05-3712fje] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent genetic studies have associated members of the thrombospondin (TSP) gene family with premature cardiovascular disease. The disease-associated polymorphisms lead to single amino acid changes in TSP-4 (A387P) and TSP-1 (N700S). These substitutions reside in adjacent domains of these highly homologous proteins. Secondary structural predictive programs and the homology of the domains harboring these amino acid substitutions to those in other proteins pointed to potential alterations of putative Ca2+ binding sites that reside in close proximity to the polymorphic amino acids. Since Ca2+ binding is critical for the structure and function of TSP family members, direct evidence for differences in Ca2+ binding by the polymorphic forms was sought. Using synthetic peptides and purified recombinant variant fragments bearing the amino acid substitutions, we measured differences in Tb3+ luminescence as an index of Ca2+ binding. The Tb3+ binding constants placed the TSP-1 region affected by N700S polymorphism among other high-affinity Ca2+ binding sites. The affinity of Ca2+ binding was lower for peptides (3.5-fold) and recombinant fragments (10-fold) containing the S700 vs. the N700 form. In TSP-4, the P387 form acquired an additional Ca2+ binding site absent in the A387 form. The results of our study suggest that both substitutions (A387P in TSP-4 and N700S in TSP-1) alter Ca2+ binding properties. Since these substitutions exert the opposite effects on Ca2+ binding, a decrease in TSP-1 and an increase in TSP-4, the two TSP variants are likely to influence cardiovascular functions in distinct but yet pathogenic ways.
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Affiliation(s)
- Olga I Stenina
- Department of Molecular Cardiology, Joseph J. Jacobs Center for Thrombosis, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
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Ludbrook SB, Barry ST, Delves CJ, Horgan CMT. The integrin alphavbeta3 is a receptor for the latency-associated peptides of transforming growth factors beta1 and beta3. Biochem J 2003; 369:311-8. [PMID: 12358597 PMCID: PMC1223078 DOI: 10.1042/bj20020809] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2002] [Revised: 09/13/2002] [Accepted: 10/02/2002] [Indexed: 12/31/2022]
Abstract
The integrins alpha(v)beta(1), alpha(v)beta(5), alpha(v)beta(6) and alpha(v)beta(8) have all recently been shown to interact with the RGD motif of the latency-associated peptide (LAPbeta(1)) of transforming growth factor beta(1) (TGFbeta(1)), with binding to alpha(v)beta(6) and alpha(v)beta(8) leading to TGFbeta(1) activation. Previously it has been suggested that the remaining alpha(v) integrin, alpha(v)beta(3,) does not interact with LAPbeta(1). However, here we show clearly that alpha(v)beta(3) does indeed interact with the LAPbeta(1) RGD motif. This interaction is similar to other alpha(v)beta(3) ligands in terms of the cations required for adhesion, the concentrations of LAPbeta(1) required for binding and the ability of a small-molecule inhibitor of alpha(v)beta(3), SB223245, to block the interaction. Using glutathione S-transferase fusion proteins we have mapped a minimal integrin-binding loop in LAPbeta(1) and then used this approach to probe the integrin-binding properties of the equivalent loops in LAPbeta(2) and LAPbeta(3). We show that the RGD motif of LAPbeta(3) also interacts with alpha(v)beta(3), in addition to alpha(v)beta(6), alpha(v)beta(1) and alpha(v)beta(5), whereas the corresponding loop in LAPbeta(2) does not interact with these integrins. These observations therefore correct a previously reported inaccuracy in the literature. Furthermore, they are important as they link alpha(v)beta(3) and TGFbeta, which may have implications in cancer and a number of inflammatory and fibrotic diseases where expression of both proteins has been documented.
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Affiliation(s)
- Steven B Ludbrook
- Department of Systems Research, GlaxoSmithKline Research and Development, Gunnels Wood Road, Stevenage SG1 2NY, U.K.
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13
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Humphries MJ. Insights into integrin-ligand binding and activation from the first crystal structure. ARTHRITIS RESEARCH 2002; 4 Suppl 3:S69-78. [PMID: 12110125 PMCID: PMC3240139 DOI: 10.1186/ar563] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2002] [Revised: 02/28/2002] [Accepted: 03/03/2002] [Indexed: 12/31/2022]
Abstract
Integrin receptors transduce bidirectional signals between extracellular adhesion molecules and intracellular cytoskeletal and signalling molecules. The structural basis of integrin signalling is unknown, but the recent publication of the first crystal structure of the extracellular domain of integrin alphaVbeta3 has provided a number of insights. In this review, previous structure-function analyses of integrins that have employed biochemical and molecular biological approaches are placed in the context of the crystal structure, and novel routes to the development of integrin antagonists are discussed.
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Affiliation(s)
- Martin J Humphries
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, UK.
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