The second domain of intercellular adhesion molecule-1 (ICAM-1) maintains the structural integrity of the leucocyte function-associated antigen-1 (LFA-1) ligand-binding site in the first domain.
The first domain of intercellular adhesion molecule-1 (ICAM-1) binds to the leucocyte function-associated antigen-1 (LFA-1) I domain, which contains the principal ligand-binding site of this leucocyte integrin. Whether the function of the second domain is also to directly bind LFA-1 has been unclear. Our data show that mutation in the hydrophilic EF loop of ICAM-1 domain 2 resulted in impaired binding of the isolated I domain when compared with wild-type ICAM-1. LFA-1 on T-cells also binds with reduced affinity to this ICAM-1 mutant. A hybrid construct containing the first domain of vascular cell-adhesion molecule-1 joined to domains 2-5 of ICAM-1 was unable to bind to the I domain, showing that there is no direct interaction between the second domain of ICAM-1 and the I domain. This construct was also not bound by LFA-1 expressed in T-cells. Function-blocking monoclonal antibodies that map to domain 2 of ICAM-1, implicating this domain in ligand binding, were found to act indirectly. In summary our data suggest that the second domain of ICAM-1 has a role in maintaining the structure of the LFA-1 ligand-binding site in the first domain of ICAM-1 but does not appear to have a direct role in ligand binding.
Stanley
P
P
Leukocyte Adhesion Laboratory, Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
McDowall
A
A
Bates
P A
PA
Brashaw
J
J
Hogg
N
N
D000911:Antibodies, Monoclonal / Q000276:immunology; D001665:Binding Sites; D002448:Cell Adhesion; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D019169:Jurkat Cells; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000737:chemistry / Q000378:metabolism
D000911:Antibodies, Monoclonal; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1; D011993:Recombinant Fusion Proteins; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1