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.

中文翻译：

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TIM-3 的棕榈酰化促进免疫衰竭并抑制抗肿瘤免疫


T 细胞免疫球蛋白和含粘蛋白结构域的蛋白 3 （TIM-3） 是一种免疫检查点，在免疫衰竭中起关键作用。然而，关于调节 TIM-3 表面表达和周转的机制知之甚少。在这里，我们报道了人 TIM-3 在残基半胱氨酸 296 （Cys 296） 处被棕榈酰转移酶 DHHC9 棕榈酰化。棕榈酰化通过阻止与 E3 泛素连接酶 HRD1 结合来稳定 TIM-3，从而抑制其多泛素化和降解。DHHC9 敲除减弱了嵌合抗原受体 T （CAR-T） 细胞耗竭，TIM-3 棕榈酰化的肽抑制剂加速了 TIM-3 降解并增强了 CAR-T 细胞和自然杀伤 （NK） 细胞介导的抗肿瘤免疫。在肝细胞癌中，DHHC9 表达与 CD8 + T 细胞和 NK 细胞中 TIM-3 的表达相关，高 DHHC9 表达与高 TIM-3 患者的生存期缩短相关。这些发现表明，DHHC9 催化的 TIM-3 棕榈酰化促进了其稳定性，导致免疫衰竭和抗肿瘤免疫受损。