Differential Engagement of Modules 1 and 4 of Vascular Cell Adhesion Molecule-1 (CD106) by Integrins α4β1 (CD49d/29) and αMβ2 (CD11b/18) of Eosinophils

Abstract

We have studied adhesion of eosinophils to various forms of vascular cell adhesion molecule 1 (VCAM-1, CD106), an integrin counter-receptor implicated in eosinophil recruitment to the airway in asthma. Full-length 7d-VCAM-1, with seven immunoglobulin-like modules, contains integrin-binding sites in modules 1 and 4. The alternatively spliced six-module protein, 6d-VCAM-1, lacks module 4. In static assays, unactivated purified human blood eosinophils adhered similarly to recombinant soluble human 6d-VCAM-1 and 7d-VCAM-1 coated onto polystyrene microtiter wells. Further experiments, however, revealed differences in recognition of modules 1 and 4. Antibody blocking indicated that eosinophil adhesion to 6d-VCAM-1 or a VCAM-1 construct containing only modules 1-3, 1-3VCAM-1, is mediated by ␣4␤1 (CD49d/29) ,whereas adhesion to a construct containing modules 4 -7, 4 -7VCAM-1, is mediated by both ␣4␤1 and ␣M␤2 (CD11b/18). Inhibitors of phosphoinositide 3-kinase, which block adhesion of eosinophils mediated by ␣M␤2, blocked adhesion to 4 -7VCAM-1 but had no effect on adhesion to 6d-VCAM-1. Consistent with the antibody and pharmacological blocking experiments, eosinophilic leukemic cell lines lacking ␣M␤2 did not adhere to 4 -7VCAM-1 but did adhere to 6d-VCAM-1 or 1-3VCAM-1. Activation of eosinophils by interleukin (IL)-5 enhanced static adhesion to 6d-VCAM-1, 7d-VCAM-1, or 4 -7VCAM-1; IL-5-enhanced adhesion to all 3 constructs was blocked by anti-␣M␤2. Adhesion of unstimulated eosinophils to 7d-VCAM-1 under flow conditions was inhibited by anti-␣4 or anti-␣M. IL-5 treatment decreased eosinophil adhesion to 7d-VCAM-1 under flow, and anti-␣M had the paradoxical effect of increasing adhesion. These results demonstrate that ␣M␤2 modulates ␣4␤1-mediated eosinophil adhesion to VCAM-1 under both static and flow conditions. Vascular cell adhesion molecule 1 (VCAM-1)2 is a multimodular cell-surface glycoprotein up-regulated on human endothelium in response to pro-inflammatory cytokines in the asthmatic lung (1) and has been implicated in recruitment of eosinophils (EOS) from blood to the airway in asthma (2). Heterodimeric integrin receptors interacting with VCAM-1 are important in the rolling, firm adhesion, and movement of EOS (3, 4). These events are regulated by cytokines, which may alter integrin adhesive activity (5, 6). EOS express at least three potential integrin receptors that may be involved in adhesion to VCAM-1: ␣4␤1 (7-9), ␣D␤2 (7), and ␣4␤7 (8 -11).Considerable information is available about features of human VCAM-1 that are important for adhesion. The loop between ␤ strands C and D in the first immunoglobulin (Ig)-like module is accessible on the protein surface and contains the core integrin-recognition sequence Ile 39 -Asp-Ser-Pro-Leu 43 (IDSPL) (11-15). A second IDSPL site is present in the CD loop in module 4 (12, 14). Based on topology of exons within the mammalian genome and the similarity in amino acid sequence, a three-module unit was likely duplicated to generate VCAM-1 modules 1-3 and 4 -6 (16, 17). Modul...

Development of urinary incontinence in a 7-year old boy after therapy with proton pump inhibitors and complete resolution of his clinicopathologic features of eosinophilic esophagitis after H2-receptor antagonist treatment: A case report

“…Several mechanisms which may predispose GERD patients for the development of EoE have been described, such as acid peptic damage to the tight junctions between epithelial cells affecting permeability of the esophageal epithelium for allergens (27,28), as well as enhancement of expression of adhesion molecules and production of inflammatory mediators and cytokines that attract and recruit inflammatory cells including eosinophils in the esophagus (29,30).…”

Up-Regulation and Activation of Eosinophil Integrins in Blood and Airway after Segmental Lung Antigen Challenge

“…␣ M ␤ 2 is believed to be important for eosinophil migration (22,51,53,(93)(94)(95). Thus, the scenario has migrating eosinophils using activated ␣ M ␤ 2 and possibly other integrins to interact with multiple substrates (22,36,92), including VCAM-1, ICAM-1, and extracellular matrix proteins, on endothelial cells, in connective tissue, and on epithelium of the bronchial wall. …”

“…Circulating eosinophils with activated ␤ 1 and up-regulated ␣ D are presumed to have a higher probability of arresting on VCAM-1 on the activated endothelium of the bronchial circulation (Fig. 11), because adhesion of purified blood eosinophils to VCAM-1 is mediated by ␣ 4 ␤ 1 (22,92), with a possible contribution by ␣ D ␤ 2 (22,31). ␣ M and␤ 2 are shown as being up-regulated and ␤ 2 integrins as being activated by IL-5, also elaborated in response to allergen.…”

Surface markers distinguishing mesenchymal stem cells from fibroblasts

“…Halfon S and colleagues (10) showed that only 16.7% of fibroblasts expressed ITGA11 on their surface compared with MSCs of early (51.4%) and late (28.6%) passages. CD106 (also known as vascular cell adhesion molecule-1 VCAM-1) is a member of the Ig superfamily which mediates leukocyte-endothelial cell adhesion and signal transduction during inflammation (13,14). It was shown that CD106 protein was expressed only on MSCs but not on fibroblasts (10).…”