Granzyme A from killer lymphocytes cleaves gasdermin B (GSDMB) and triggers pyroptosis in targeted human tumor cells, eliciting antitumor immunity. However, GSDMB has a controversial role in pyroptosis and has been linked to both anti- and protumor functions. Here, we found that GSDMB splicing variants are functionally distinct. Cleaved N-terminal (NT) fragments of GSDMB isoforms 3 and 4 caused pyroptosis, but isoforms 1, 2, and 5 did not. The nonfunctional isoforms have a deleted or modified exon 6 and therefore lack a stable belt motif. The belt likely contributes to the insertion of oligomeric GSDMB-NTs into the membrane. Consistently, noncytotoxic GSDMB-NTs blocked pyroptosis caused by cytotoxic GSDMB-NTs in a dominant-negative manner. Upon natural killer (NK) cell attack, GSDMB3-expressing cells died by pyroptosis, whereas GSDMB4-expressing cells died by mixed pyroptosis and apoptosis, and GSDMB1/2-expressing cells died only by apoptosis. GSDMB4 partially resisted NK cell-triggered cleavage, suggesting that only GSDMB3 is fully functional. GSDMB1-3 were the most abundant isoforms in the tested tumor cell lines and were similarly induced by interferon-γ and the chemotherapy drug methotrexate. Expression of cytotoxic GSDMB3/4 isoforms, but not GSDMB1/2 isoforms that are frequently up-regulated in tumors, was associated with better outcomes in bladder and cervical cancers, suggesting that GSDMB3/4-mediated pyroptosis was protective in those tumors. Our study indicates that tumors may block and evade killer cell-triggered pyroptosis by generating noncytotoxic GSDMB isoforms. Therefore, therapeutics that favor the production of cytotoxic GSDMB isoforms by alternative splicing may improve antitumor immunity.

中文翻译：

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GSDMB 的选择性剪接调节杀伤淋巴细胞触发的细胞焦亡

来自杀伤淋巴细胞的颗粒酶 A 裂解 Gasdermin B (GSDMB) 并触发目标人类肿瘤细胞焦亡，从而引发抗肿瘤免疫。然而，GSDMB 在细胞焦亡中的作用存在争议，并且与抗肿瘤和促肿瘤功能有关。在这里，我们发现GSDMB剪接变体在功能上是不同的。GSDMB 同工型 3 和 4 的 N 端 (NT) 片段切割会导致细胞焦亡，但同工型 1、2 和 5 则不会。非功能性亚型具有删除或修饰的外显子 6，因此缺乏稳定的带基序。该带可能有助于将寡聚 GSDMB-NT 插入膜中。一致地，非细胞毒性 GSDMB-NT 以显性失活方式阻断细胞毒性 GSDMB-NT 引起的细胞焦亡。在自然杀伤（NK）细胞攻击后，表达GSDMB3的细胞因焦亡而死亡，而表达GSDMB4的细胞因混合焦亡和凋亡而死亡，而表达GSDMB1/2的细胞仅因凋亡而死亡。GSDMB4 部分抵抗 NK 细胞触发的裂解，表明只有 GSDMB3 具有完全功能。GSDMB1-3是测试的肿瘤细胞系中最丰富的亚型，并且类似地由干扰素-γ和化疗药物甲氨蝶呤诱导。细胞毒性的表达GSDMB3/4同种型，但不是GSDMB1/2在肿瘤中经常上调的亚型与膀胱癌和宫颈癌的更好结果相关，这表明 GSDMB3/4 介导的细胞焦亡对这些肿瘤具有保护作用。我们的研究表明，肿瘤可以通过产生非细胞毒性的 GSDMB 亚型来阻止和逃避杀伤细胞触发的细胞焦亡。因此，有利于通过选择性剪接产生细胞毒性 GSDMB 亚型的治疗方法可能会提高抗肿瘤免疫力。