Palmitoylation of TIM-3 promotes immune exhaustion and restrains antitumor immunity
Zhaoying Zhang, Caiyue Ren, Rong Xiao, Shuaiya Ma, Huimin Liu, Yutong Dou, Yu‐Chen Fan, Shuo Wang, Peng Zhan, Chengjiang Gao, Xuetian Yue, Chunyang Li, Lifen Gao, Xiaohong Liang, Zhuanchang Wu, Chunhong Ma
Abstract
T cell immunoglobulin and mucin domain–containing protein 3 (TIM-3) is an immune checkpoint that has critical roles in immune exhaustion. However, little is known about the mechanisms that regulate TIM-3 surface expression and turnover. Here, we report that human TIM-3 is palmitoylated by the palmitoyltransferase DHHC9 at residue cysteine 296 (Cys 296 ). Palmitoylation stabilized TIM-3 by preventing binding to E3 ubiquitin ligase HRD1, thereby suppressing its polyubiquitination and degradation. DHHC9 knockdown attenuated chimeric antigen receptor T (CAR-T) cell exhaustion, and a peptidic inhibitor of TIM-3 palmitoylation accelerated TIM-3 degradation and enhanced antitumor immunity mediated by CAR-T cells and natural killer (NK) cells. In hepatocellular carcinoma, DHHC9 expression correlated with TIM-3 expression in CD8 + T cells and NK cells, and high DHHC9 expression was associated with shorter survival in patients with high TIM-3. These findings demonstrate that palmitoylation of TIM-3 catalyzed by DHHC9 promotes its stability, resulting in immune exhaustion and impaired antitumor immunity.