Involvement of the LFA-1 ligand JAM-A in inflammatory recruitment of mononuclear cells : identification of the JAM-A binding domain in LFA-1

Junctional adhesion molecule-A (JAM-A) is a ligand of the integrin lymphocyte function-associated antigen-1 (LFA-1). In this study the JAM-A binding site in LFA-1 was identified and the involvement of JAM-A in inflammatory recruitment of mononuclear cells was analyzed. Furthermore, a functional contribution of JAM-A to atherogenesis was investigated. By deletion of the I domain in the aL subunit of LFA-1 and expression of this aL mutant in aL-deficient Jurkat J-ß2.7 T cells, it was here demonstrated that the I domain of LFA-1 is crucial for adhesion to immobilized JAM-A. This was substantiated by blocking the stimulated adhesion of T cells or monocytes to JAM-A using the I domain-directed mAb TS1/22 or the small molecule antagonist BIRT377, which stabilizes the low-affinity conformation of the I domain. The immobilized LFA-1 I domain locked in the open high-affinity conformation was sufficient to support adhesion of transfected Chinese hamster ovary cells expressing human JAM-A. A solid-phase binding assay confirmed a direct interaction of recombinant JAM-A with immobilized LFA 1 I domain locked in the open high-affinity conformation. These data have demonstrated that the I domain of LFA-1 is sufficient and required for the functional interactions of LFA-1 with JAM-A. Using soluble JAM-A.Fc chimeric protein as a competitive inhibitor, the involvement of JAM-A in distinct steps of mononuclear cells recruitment was analyzed. Adhesion assays revealed that LFA-1-mediated binding of T cells or monocytes to immobilized ICAM-1 or cytokine-costimulated endothelium was dose-dependently inhibited by soluble JAM-A.Fc. Similarly, soluble JAM-A.Fc reduced the LFA-1-mediated SDF-1-triggered arrest under flow conditions and transendothelial chemotaxis of T cells. These data have shown that soluble JAM-A can be effectively applied to inhibit distinct steps of inflammatory recruitment of mononuclear cells. Immunofluorescence and real-time RT-PCR analysis showed an upregulation of JAM-A expression on early atherosclerotic endothelium of carotid arteries from apolipoprotein E-deficient (apoE-/-) mice fed a high fat Western-type diet. In ex vivo perfusion assays, soluble JAM-A.Fc inhibited the VLA-4-independent accumulation of mononuclear cells on atherosclerotic endothelium. Together with the upregulation of JAM-A on atherosclerotic endothelium, this suggests a functional contribution of JAM-A to atherogenesis. The role of endothelial JAM-A in atherogenic recruitment was further substantiated by an attenuation of monocyte arrest and transmigration on activated JAM-A-/-apoE-/- versus JAM-A+/+apoE-/- mouse aortal endothelial cells in vitro. The findings from this work may be helpful in designing new stategies for the development of anti-inflammatory therapies.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2007

Author dc:creator

• Fraemohs, Line Rebo

Contributors dc:contributor

• Fischer, Rainer

• info:eu-repo/classification/ddc/570
• Zell-Adhäsionsmolekül
• Tight junction
• Chemotaxis
• Atherogenese
• Biowissenschaften, Biologie
• cell adhesion molecule
• atherogenesis

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-124009%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62440