The leukocyte integrin alpha D beta 2 binds VCAM-1: evidence for a binding interface between I domain and VCAM-1.
The trafficking of leukocytes through tissues is supported by an interaction between the beta 2 (CD18) integrins CD11a/CD18 (LFA-1) and CD11b/CD18 (Mac-1) and their ligand ICAM-1. The most recently identified and fourth member of the beta 2 integrins, alpha D beta 2, selectively binds ICAM-3 and does not appear to bind ICAM-1. We have reported recently that alpha D beta 2 can support eosinophil adhesion to VCAM-1. Here we demonstrate that expression of alpha D beta 2 in a lymphoid cell that does not express alpha 4 integrins confers efficient binding to VCAM-1. In addition, a soluble form of alpha D beta 2 binds VCAM-1 with greater efficiency relative to ICAM-3. The I domain of alpha D contains a binding site for VCAM-1 since recombinant alpha D I domain binds specifically to VCAM-1. In addition, alpha D mAb that block cellular binding to VCAM-1 bind the alpha D I domain. Using VCAM-1 mutants we have determined that the binding site on VCAM-1 for alpha D beta 2 overlaps with that of alpha 4++ integrins. Substitution of VCAM-1 aspartate at position 40, D40, within the conserved integrin binding site, diminishes binding to alpha D beta 2 and abrogates binding to the alpha D I domain. The corresponding integrin binding site residue in ICAM-3 is also essential to alpha D beta 2 binding. Finally, we demonstrate that alpha D beta 2 can support lymphoid cell adhesion to VCAM-1 under flow conditions at levels equivalent to those mediated by alpha 4 beta 1. These results indicate that VCAM-1 can bind to an I domain and that the binding of alpha D beta 2 to VCAM-1 may contribute to the trafficking of a subpopulation of leukocytes that express alpha D beta 2.
Van der Vieren
M
M
ICOS Corp., Bothell, WA 98021, USA.
Crowe
D T
DT
Hoekstra
D
D
Vazeux
R
R
Hoffman
P A
PA
Grayson
M H
MH
Bochner
B S
BS
Gallatin
W M
WM
Staunton
D E
DE
D000818:Animals; D019138:Antibodies, Blocking / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D001666:Binding Sites, Antibody; D018845:CD11 Antigens; D002448:Cell Adhesion / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D006801:Humans; D039001:Integrin alpha Chains; D039441:Integrin alpha4; D016023:Integrins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D019169:Jurkat Cells; D007962:Leukocytes / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D016024:Receptors, Cytoadhesin; D011994:Recombinant Proteins / Q000378:metabolism; D012212:Rheology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
D019138:Antibodies, Blocking; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018845:CD11 Antigens; C406812:ITGAD protein, human; D039001:Integrin alpha Chains; D016023:Integrins; D010446:Peptide Fragments; D016024:Receptors, Cytoadhesin; D011994:Recombinant Proteins; D019010:Vascular Cell Adhesion Molecule-1; D039441:Integrin alpha4