The functional interaction of the beta 2 integrin lymphocyte function-associated antigen-1 with junctional adhesion molecule-A is mediated by the I domain

• Published in: The Journal of immunology (1950) 2004-11, Vol.173 (10), p.6259-6264
• Main Authors: Fraemohs, Line, Koenen, Rory R, Ostermann, Georg, Heinemann, Bo, Weber, Christian
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Blocking - pharmacology; Antibodies, Monoclonal - pharmacology; Binding, Competitive - genetics; Binding, Competitive - immunology; CD18 Antigens - biosynthesis; CD18 Antigens - genetics; CD18 Antigens - immunology; CD18 Antigens - metabolism; Cell Adhesion Molecules - metabolism; Cell Adhesion Molecules - physiology; CHO Cells; Cricetinae; Humans; Imidazolidines - pharmacology; Junctional Adhesion Molecules; Jurkat Cells; Lymphocyte Function-Associated Antigen-1 - biosynthesis; Lymphocyte Function-Associated Antigen-1 - genetics; Lymphocyte Function-Associated Antigen-1 - immunology; Lymphocyte Function-Associated Antigen-1 - metabolism; Protein Binding - genetics; Protein Structure, Tertiary - genetics; Protein Structure, Tertiary - physiology; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Sequence Deletion
• ISSN: 0022-1767

Binding of the beta(2) integrin LFA-1 (alpha(L)beta(2)) to junctional adhesion molecule-A (JAM-A) has been shown to enhance leukocyte adhesion and transendothelial migration. This is mediated by the membrane-proximal Ig-like domain 2 of JAM-A; however, the location of the JAM-A binding site in LFA-1 has not been identified. We have deleted the I domain in the alpha(L) subunit of LFA-1 and expressed this alpha(L) mutant in alpha(l)-deficient Jurkat J-beta(2).7 cells to demonstrate that the I domain of LFA-1 is crucial for their adhesion to immobilized JAM-A. This was substantiated by blocking the stimulated adhesion of wild-type Jurkat T cells or monocytic Mono Mac 6 cells to JAM-A using the I domain-directed mAb TS1/22 or the small molecule antagonist BIRT 377, 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 binding of transfected Chinese hamster ovary cells expressing JAM-A. Solid-phase binding assays confirmed a direct interaction of recombinant JAM-A with the immobilized locked-open I domain. These data provide the first evidence that the I domain of LFA-1 contains a functional binding site for JAM-A.