Inhibitory mechanisms of LAG-3–dependent T cell suppression
前田, 武雄 徳島大学大学院医科学教育部（医学専攻）
T cell activation is tightly regulated by both stimulatory and inhibitory co-receptors and has been a focus in the development of interventions for managing cancer or autoimmune diseases. Targeting the inhibitory co-receptors programmed cell death 1 (PD-1) and cytotoxic T lymphocyte–associated protein 4 (CTLA-4) has successfully eradicated tumors but induced immune-related adverse events in humans and mice. The beneficial and adverse effects of targeting these co-receptors highlight their importance in cancer immunity and also autoimmunity. Although the therapeutic potencies of other inhibitory co-receptors are under extensive investigation, their inhibitory mechanisms and their functional differences are not well understood. Here we analyzed the inhibitory mechanisms of lymphocyte activation gene-3 (LAG-3), another inhibitory co-receptor, by using an in vitro T cell activation system and a high-affinity anti-LAG-3 antibody that strongly interferes with the binding of LAG-3 to its ligand. We found that the expression level of LAG-3 strongly correlates with the inhibitory function of LAG-3, suggesting that LAG-3 functions as a rheostat rather than as a breaker of T cell activation. By evaluating the inhibitory capacities of various LAG-3 variants relative to their expression levels, we found that LAG-3 transduces two independent inhibitory signals through an FXXL motif in the membrane-proximal region and the C-terminal EX repeat. These motifs have not been reported previously for inhibitory co-receptors, suggesting that LAG-3 inhibits T cell activation through a nonredundant inhibitory mechanisms along with the other inhibitory co-receptors. Our findings provide a rationale for combinatorial targeting of LAG-3 and the other inhibitory co-receptors to improve cancer immunotherapy.
Journal of Biological Chemistry
American Society for Biochemistry and Molecular Biology
本論文は，著者Takeo K. Maedaの学位論文として提出され，学位審査・授与の対象となっている。
This research was originally published in the Journal of Biological Chemistry. Takeo K. Maeda, Daisuke Sugiura, Il-mi Okazaki, Takumi Maruhashi, Taku Okazaki. Atypical motifs in the cytoplasmic region of the inhibitory immune co-receptor LAG-3 inhibit T cell activation. J. Biol. Chem. 2019 Vol.294(15), pp.6017-6026.
© 2019 Maeda et al. Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.
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