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      Integrins

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          Abstract

          Integrins are cell adhesion receptors that are evolutionary old and that play important roles during developmental and pathological processes. The integrin family is composed of 24 αβ heterodimeric members that mediate the attachment of cells to the extracellular matrix (ECM) but that also take part in specialized cell-cell interactions. Only a subset of integrins (8 out of 24) recognizes the RGD sequence in the native ligands. In some ECM molecules, such as collagen and certain laminin isoforms, the RGD sequences are exposed upon denaturation or proteolytic cleavage, allowing cells to bind these ligands by using RGD-binding receptors. Proteolytic cleavage of ECM proteins might also generate fragments with novel biological activity such as endostatin, tumstatin, and endorepellin. Nine integrin chains contain an αI domain, including the collagen-binding integrins α1β1, α2β1, α10β1, and α11β1. The collagen-binding integrins recognize the triple-helical GFOGER sequence in the major collagens, but their ability to recognize these sequences in vivo is dependent on the fibrillar status and accessibility of the interactive domains in the fibrillar collagens. The current review summarizes some basic facts about the integrin family including a historical perspective, their structure, and their ligand-binding properties.

          Electronic supplementary material

          The online version of this article (doi:10.1007/s00441-009-0834-6) contains supplementary material, which is available to authorized users.

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          Most cited references 94

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          Integrin ligands at a glance.

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            Crystal structure of the extracellular segment of integrin alpha Vbeta3 in complex with an Arg-Gly-Asp ligand.

            The structural basis for the divalent cation-dependent binding of heterodimeric alphabeta integrins to their ligands, which contain the prototypical Arg-Gly-Asp sequence, is unknown. Interaction with ligands triggers tertiary and quaternary structural rearrangements in integrins that are needed for cell signaling. Here we report the crystal structure of the extracellular segment of integrin alphaVbeta3 in complex with a cyclic peptide presenting the Arg-Gly-Asp sequence. The ligand binds at the major interface between the alphaV and beta3 subunits and makes extensive contacts with both. Both tertiary and quaternary changes are observed in the presence of ligand. The tertiary rearrangements take place in betaA, the ligand-binding domain of beta3; in the complex, betaA acquires two cations, one of which contacts the ligand Asp directly and the other stabilizes the ligand-binding surface. Ligand binding induces small changes in the orientation of alphaV relative to beta3.
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              Genetic and cell biological analysis of integrin outside-in signaling.

              Integrins are cell surface transmembrane receptors that recognize and bind to extracellular matrix proteins and counter receptors. Binding of activated integrins to their ligands induces a vast number of structural and signaling changes within the cell. Large, multimolecular complexes assemble onto the cytoplasmic tails of activated integrins to engage and organize the cytoskeleton, and activate signaling pathways that ultimately lead to changes in gene expression. Additionally, integrin-mediated signaling intersects with growth factor-mediated signaling through various levels of cross-talk. This review discusses recent work that has tremendously broadened our understanding of the complexity of integrin-mediated signaling.
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                Author and article information

                Contributors
                +47-555-86332 , +47-555-86410 , donald.gullberg@biomed.uib.no
                Journal
                Cell Tissue Res
                Cell and Tissue Research
                Springer-Verlag (Berlin/Heidelberg )
                0302-766X
                1432-0878
                20 August 2009
                January 2010
                : 339
                : 1
                : 269-280
                Affiliations
                Department of Biomedicine, University of Bergen, Jonas Lies Vei 91, 5009 Bergen, Norway
                Article
                834
                10.1007/s00441-009-0834-6
                2784866
                19693543
                © The Author(s) 2009
                Categories
                at-a-Glance Article
                Custom metadata
                © Springer-Verlag 2010

                Molecular medicine

                integrins, history, ligands, α and β subunits, rgd, gfoger, collagen

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