Characterization of the major histocompatibility complex class II binding site on LAG-3 protein.
The lymphocyte activation gene-3 (LAG-3), selectively transcribed in human activated T and NK cells, encodes a ligand for major histocompatibility complex (MHC) class II molecules. Like CD4, LAG-3 ectodomain is composed of four Ig-like domains (D1-D4). Nothing is known about the LAG-3 regions or residues required to form a stable MHC class II binding site. In contrast to CD4, soluble LAG-3 molecules stably interact with MHC class II molecules expressed on the cell surface. In addition, the first two N-terminal domains of soluble LAG-3 (D1 and D2) molecules, alone, are capable of binding MHC class II. From a LAG-3 model structure, we designed mutants and tested their ability to bind MHC class II molecules in an intercellular adhesion assay. We found residues on the membrane-distal, CDR1-2-containing top face of D1 that are essential for either binding or repulsing MHC class II proteins. Most of these residues are clustered at the base of a large extra-loop structure that is a hallmark of the LAG-3 D1 Ig-like domain. In addition, as for CD4, oligomerization of LAG-3 on the cell surface may be required to form a stable MHC binding site because mutation of three residues in the ABED beta-strands containing side of D1 results in a dominant negative effect (i.e., binding inhibition of coexpressed wild-type LAG-3).
Huard
B
B
Laboratoire d'Immunologie Cellulaire, Institut National de la Santé et de la Recherche Médicale, U333, Institut Gustave-Roussy, 39, rue Camille Desmoulins, 94805 Villejuif Cedex, France.
Mastrangeli
R
R
Prigent
P
P
Bruniquel
D
D
Donini
S
S
El-Tayar
N
N
Maigret
B
B
Dréano
M
M
Triebel
F
F
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000737:chemistry; D001665:Binding Sites; D015704:CD4 Antigens / Q000737:chemistry*; D019556:COS Cells; D006681:HLA-D Antigens / Q000737:chemistry / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology; D007700:Kinetics; D008024:Ligands; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured; D000093322:Lymphocyte Activation Gene 3 Protein
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015704:CD4 Antigens; D006681:HLA-D Antigens; D000949:Histocompatibility Antigens Class II; D008024:Ligands; D008565:Membrane Proteins; D011994:Recombinant Proteins; D000093322:Lymphocyte Activation Gene 3 Protein; C000720328:soluble LAG-3 protein, human; C000720326:Lag3 protein, human