Lymphocyte-fibroblast adhesion A useful model for analysis of the interaction of the leucocyte integrin LFA-1 with ICAM-1 (original) (raw)
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On the species specificity of the interaction of LFA-1 with intercellular adhesion molecules
Journal of immunology (Baltimore, Md. : 1950), 1990
Species restrictions in immune cell interactions have been demonstrated both in Ag-specific responses of T lymphocytes and the phenomenon of natural attachment. To determine the possible contribution of adhesion receptors to these restrictions, we have studied binding between the murine and human homologues of LFA-1 (CD11a/CD18) and ICAM employing purified human LFA-1 and ICAM-1 (CD54) bound to solid substrates. Murine cell lines bind to purified human LFA-1 through ICAM-1 and at least one other counter-receptor. This provides evidence for multiple counter-receptors for LFA-1 in the mouse as well as in the human. In contrast to binding of murine ICAM-1 to human LFA-1, murine LFA-1 does not bind to human ICAM-1. The species specificity maps to the LFA-1 alpha subunit, because mouse x human hybrid cells expressing the human alpha subunit associated with a mouse beta subunit bind to human ICAM-1, whereas those with a human beta subunit associated with a murine alpha subunit do not. Inc...
Cellular Immunology, 1990
The integrin surface molecule termed lymphocyte functional antigen-1 (LFA-1), and its physiological ligand intercellular adhesion molecule-1 (ICAM-1), have been proven to play a relevant role in several immune reactions where cell-to-cell contact is required: these reactions include allogeneic mixed lymphocyte reaction (MLR) and direct cytotoxicity. In the present study, we show that monoclonal antibodies (mAbs) directed to LFA-1 as well as to ICAM-1 molecules are able to inhibit T cell proliferation in autologous MLR (AMLR). Such an in vitro reaction is generally considered a functional model of Ia-mediated immunocompetent cell cooperation, and is impaired in several pathological conditions. It is noteworthy that the LFA-1 molecule is largely represented on the T cell surface, whereas ICAM-1 is poorly expressed on resting T cells: autologous stimulation slightly increases ICAM-1 expression. Pretreatment studies indicate that the inhibitory effect of anti-ICAM-1 mAb on T cell proliferation in AMLR is exerted on responder T cells.
Proceedings of The National Academy of Sciences, 1993
The signaling that causes the leukocyte integrin lymphocyte function-associated molecule (LFA-1) to bind firmly to its ligand intercellular adhesion molecule 1 (ICAM-1) is transduced indirectly through other T-cell receptors and is termed inside-out signaling. We show here that the highaffinity state of LFA-1 is characterized by expression of the LFA-1 epitope detected by monoclonal antibody 24. This epitope is expressed not in response to the initial agonistmediated signal but when LFA-1 binds to ICAM-1, indicating that ligand binding induces an alteration in LFA-1. As would be predicted, the monoclonal antibody 24 epitope is confined to the LFA-1, which is located at the site ofcontact between T cells and ICAM-1-expressing transfectants. When a fixation protocol for "freezing" receptors is used, only T cells that are fixed after prior exposure to ICAM-1 bind frmly to ICAM-1 a
Journal of Biological Chemistry, 1998
On T cells the leukocyte integrin leukocyte functionassociated antigen-1 (LFA-1) (CD11a/CD18) can be induced to bind its ligand intercellular adhesion molecule 1 (ICAM-1) (CD54) either by increasing the affinity of the receptor with Mg 2؉ and EGTA or by receptor clustering following activation with phorbol ester. The existence of these two adhesion-inducing pathways implies that alternative mechanisms might exist by which LFA-1 engages ICAM-1. The LFA-1 ␣ subunit I domain contains a major binding site for ICAM-1. In this study we show that soluble LFA-1 I domain blocks ICAM-1 binding of the high affinity Mg 2؉-induced form of LFA-1 but not the phorbol ester-induced form. Under conditions of Mg 2؉activation, the soluble I domain also prevents expression of an activation dependent epitope on LFA-1, implying that it inhibits a conformational change necessary for conversion to the high affinity form of this integrin. In addition, the binding of Mg 2؉-activated LFA-1 to ICAM-1 is blocked by peptides covering the ␣4-3 loop, the 3-␣5 loop, and the ␣5 helix of the I domain, whereas none of the peptides tested blocks phorbol ester-mediated adhesion. The blocking peptides localize to the same face of the crystal structure of the LFA-1 I domain and define an area that, during activation, may be involved in association of the I domain with another region of LFA-1, potentially the -propeller domain. This is the first evidence linking a structural domain of an integrin, in this case the I domain, with a particular activation mechanism.
Chemical Biology & Drug Design, 2007
We have used nuclear magnetic resonance to characterize the binding site of two intercellular adhesion molecule-1 derived cyclic peptides, cIBC and cIBR, to the I-domain of leukocyte function-associated antigen-1. These peptides inhibit the leukocyte function-associated antigen-1/intercellular adhesion molecule-1 interaction known to play a key role in autoimmune diseases and cancer metastasis. Perturbation of the chemical shifts and intensities of the nuclear magnetic resonance signals corresponding to a number of residues of the I-domain of leukocyte function-associated antigen-1 show that both peptides bind to the I-domain allosteric site, the binding site of I-domain allosteric inhibitors such as lovastatin, and therefore the peptides probably also act as allosteric inhibitors of leukocyte function-associated antigen-1. Molecular models of the interaction of these two cyclic peptides with leukocyte function-associated antigen-1 I-domain show that the binding mode of the three molecules are analogous: the hydrophobic residues of the peptides remain buried and occupy the same positions as the apolar groups of lovastatin, while the peptides regions containing the most polar residues are flexible and primarily exposed to the solvent. These results suggest an allosteric mechanism for the inhibitory effect on T-cell adhesion displayed by both peptides, which exhibit potential as therapeutic agents.
Journal of Biological Chemistry, 1998
By extensive mutagenic analysis of the inserted domain (I-domain) of the ␣-chain (CD11a) of the leukocyte function-associated antigen-1 (LFA-1), we have defined a putative binding surface for intercellular adhesion molecules 1 and 2 (ICAM-1 and-2). This analysis showed that individually mutating Leu-205 or Glu-241 to alanine completely abolished LFA-1 binding to ICAM-1 or-2 without affecting I-domain structure, as assayed by antibody binding. Mutating Thr-243 to alanine also had a profound effect on LFA-1 binding to ICAM-1 and-2, as seen by complete loss of binding to ICAM-1 and a significant reduction (70% decrease) in binding to ICAM-2. Mutating Glu-146 to alanine reduced LFA-1 binding to ICAM-1 or-2 by 70%, and mutating His-264 or Glu-293 to alanine reduced binding to ICAM-1 or-2 by about 30-40%. Mutating Thr-175 to alanine reduced binding to ICAM-1 by about 30% and binding to ICAM-2 by about 70%. Interestingly, mutating Lys-263 to alanine preferentially abolished LFA-1 binding to ICAM-2. Using these data, we have generated a model of the interface between the LFA-1 I-domain and residues in the first domain of ICAM-1 that have been shown to be critical for this interaction. In addition, this model, together with the ICAM-2 crystal structure, has been used to map residues that are likely to mediate LFA-1 I-domain binding to ICAM-2. Leukocyte function-associated antigen-1 (LFA-1) 1 is a member of the leukocyte integrin family. Like other members of this family, it is expressed exclusively on leukocytes and shares a common -chain ( 2 , CD18). The four members of this family that differ in their ␣-chains are LFA-1 (CD11a, ␣L), Mac-1 (CD11b, ␣M), p150,95 (CD11c, ␣X), and ␣d 2 (CD11d, ␣d). LFA-1 is constitutively expressed on the cell surface and is thought to undergo a conformational change that renders it capable of high affinity ligand binding. The primary ligands for LFA-1 are intercellular adhesion molecules-1,-2, and-3 (ICAM-1,-2, and-3). The interaction of ICAM-3 with LFA-1 is of considerably lower affinity than ICAM-1 or-2 binding to
Journal of Leukocyte Biology
The aggregation of human neutrophils in suspension has features that are analogous to their attachment to activated endothelium in that both involve selectin and  2 -integrin adhesion receptors. For the collisional interaction that forms neutrophil aggregates in suspension, there is a tethering step in which L-selectin on neutrophils binds PSGL-1. At relatively low shear rates (100-200 s -1 ) firm adhesion is mediated in equal measure by LFA-1 binding to ICAM-3, and Mac-1 binding to an as yet undefined ligand. In this report we used a mouse melanoma cell line expressing an estimated 700,000 ICAM-1 (CD54) to examine the relative roles of LFA-1 and Mac-1 over the kinetics of heterotypic cell adhesion in shear mixed suspensions. Neither heterotypic nor homotypic neutrophil aggregates formed with application of shear alone. However, the rate of aggregation peaked within seconds of chemotactic stimulation. In contrast to homotypic aggregation, neither L-selectin nor its O-glycoprotein ligands on neutrophils contributed to heterotypic adhesion. Adhesion was inhibited in a dose-dependent manner as ICAM-1 was titrated with blocking mAb. A direct interaction between LFA-1 and ICAM-1 was preferred over the first minute of stimulation, whereas at later times adhesion was supported equally by Mac-1. Activation with MnCl 2 also favored participation of the constitutively expressed LFA-1. Application of defined shear in a cone and plate viscometer showed that adhesion to the ICAM-1 cells decreased from a maximum level to baseline as shear rate increased up to 400 s -1 in a manner typical of integrin adhesion alone. In contrast, homotypic aggregation supported by the transition from selectin to integrin binding exhibited an increase in efficiency up to 800 s -1 . The pathophysiological significance of receptor site density and duration of contact in collisional interactions relevant to leukocyte recruitment compared to leukocyte-endothelial cell interactions on surfaces is discussed. J. Leukoc. Biol. 64: 622-630; 1998.