Abstract
The LM609 antibody specifically recognizes αVβ3 integrin and inhibits angiogenesis, bone resorption, and viral infections in an arginine-glycine-aspartate-independent manner. LM609 entered phase II clinical trials for the treatment of several cancers and was also used for αVβ3-targeted radioimmunotherapy. To elucidate the mechanisms of recognition and inhibition of αVβ3 integrin, we solved the structure of the LM609 antigen-binding fragment by X-ray crystallography and determined its binding affinity for αVβ3. Using single-particle electron microscopy, we show that LM609 binds at the interface between the β-propeller domain of the αV chain and the βI domain of the β3 chain, near the RGD-binding site, of all observed integrin conformational states. Integrating these data with fluorescence size-exclusion chromatography, we demonstrate that LM609 sterically hinders access of large ligands to the RGD-binding pocket, without obstructing it. This work provides a structural framework to expedite future efforts utilizing LM609 as a diagnostic or therapeutic tool.
Keywords:
LM609 antibody; abegrin; alpha V beta 3 integrin; etaracizumab; integrins; single-particle electron microscopy; vitaxin.
Copyright © 2017 Elsevier Ltd. All rights reserved.
MeSH terms
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Amino Acid Motifs
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Angiogenesis Inhibitors / chemistry
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Angiogenesis Inhibitors / immunology
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Angiogenesis Inhibitors / metabolism
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Antibodies, Monoclonal / chemistry*
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Antibodies, Monoclonal / genetics
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Antibodies, Monoclonal / immunology
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Antigens / chemistry*
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Antigens / genetics
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Antigens / immunology
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Antiviral Agents / chemistry
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Antiviral Agents / immunology
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Antiviral Agents / metabolism
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Binding Sites
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Bone Density Conservation Agents / chemistry
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Bone Density Conservation Agents / immunology
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Bone Density Conservation Agents / metabolism
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Cloning, Molecular
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Crystallography, X-Ray
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Escherichia coli / genetics
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Escherichia coli / metabolism
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Gene Expression
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Genetic Vectors / chemistry
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Genetic Vectors / metabolism
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Humans
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Immunoglobulin Fab Fragments / chemistry*
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Immunoglobulin Fab Fragments / genetics
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Immunoglobulin Fab Fragments / immunology
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Integrin alphaVbeta3 / chemistry*
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Integrin alphaVbeta3 / genetics
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Integrin alphaVbeta3 / immunology
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Ligands
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Models, Molecular
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Oligopeptides / chemistry*
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Oligopeptides / genetics
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Oligopeptides / immunology
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Protein Binding
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / immunology
Substances
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Angiogenesis Inhibitors
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Antibodies, Monoclonal
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Antigens
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Antiviral Agents
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Bone Density Conservation Agents
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Immunoglobulin Fab Fragments
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Integrin alphaVbeta3
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Ligands
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Oligopeptides
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Recombinant Proteins
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arginyl-glycyl-aspartic acid