Molecular basis for E-cadherin recognition by killer cell lectin-like receptor G1 (KLRG1).
The killer cell lectin-like receptor G1, KLRG1, is a cell surface receptor expressed on subsets of natural killer (NK) cells and T cells. KLRG1 was recently found to recognize E-cadherin and thus inhibit immune responses by regulating the effector function and the developmental processes of NK and T cells. E-cadherin is expressed on epithelial cells and exhibits Ca(2+)-dependent homophilic interactions that contribute to cell-cell junctions. However, the mechanism underlying the molecular recognition of KLRG1 by E-cadherin remains unclear. Here, we report structural, binding, and functional analyses of this interaction using multiple methods. Surface plasmon resonance demonstrated that KLRG1 binds the E-cadherin N-terminal domains 1 and 2 with low affinity (K(d) approximately 7-12 microm), typical of cell-cell recognition receptors. NMR binding studies showed that only a limited N-terminal region of E-cadherin, comprising the homodimer interface, exhibited spectrum perturbation upon KLRG1 complex formation. It was confirmed by binding studies using a series of E-cadherin mutants. Furthermore, killing assays using KLRG1(+)NK cells and reporter cell assays demonstrated the functional significance of the N-terminal region of E-cadherin. These results suggest that KLRG1 recognizes the N-terminal homodimeric interface of domain 1 of E-cadherin and binds only the monomeric form of E-cadherin to inhibit the immune response. This raises the possibility that KLRG1 detects monomeric E-cadherin at exposed cell surfaces to control the activation threshold of NK and T cells.
Nakamura
Seiko
S
Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Kuroki
Kimiko
K
Ohki
Izuru
I
Sasaki
Kaori
K
Kajikawa
Mizuho
M
Maruyama
Takuma
T
Ito
Masayuki
M
Kameda
Yosuke
Y
Ikura
Mitsuhiko
M
Yamamoto
Kazuo
K
Matsumoto
Naoki
N
Maenaka
Katsumi
K
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015820:Cadherins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism; D037181:Lectins, C-Type; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011971:Receptors, Immunologic / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013194:Staining and Labeling; D020349:Surface Plasmon Resonance
D015820:Cadherins; C451496:Klrg1 protein, mouse; D037181:Lectins, C-Type; D011971:Receptors, Immunologic; D011994:Recombinant Proteins