Moresco Philip, Kastan Jonathan P, Yang Jung-In, Prabakar Rishvanth, Minicozzi Francesca, Adams Dexter W, Cifani Paolo, Tuveson David A, Fearon Douglas T
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Graduate Program in Genetics, Stony Brook University, Stony Brook, NY 11794, USA.
bioRxiv. 2025 Jan 20:2025.01.18.633717. doi: 10.1101/2025.01.18.633717.
The exclusion of T cells causes immune escape of pancreatic ductal adenocarcinoma (PDA). T cell exclusion is mediated by the interaction between CXCR4 on T cells and its ligand, CXCL12, which is complexed to keratin-19 (KRT19) on the surface of PDA cells. KRT19 secretion by PDA cells is essential to this process but is unusual because KRT19 lacks an endoplasmic reticulum (ER)-directing signal peptide (SP). By using biotinylation by an ER-restricted TurboID system and a split-GFP assay in PDA cells, we demonstrate that KRT19 enters the ER via its "head" domain. Additionally, KRT19 is shown to interact with the signal recognition particle and its secretion is sensitive to canonical protein secretion inhibitors. In vivo, mouse tumors formed with ER-TurboID-expressing PDA cells contain biotinylated KRT19. In contrast, keratin-8 (KRT8), which colocalizes with KRT19 on the surface of PDA cells, does not enter the ER. Rather, KRT8 is externalized via secretory autophagy possibly in a complex with KRT19. Thus, despite lacking a classical SP, PDA cells secrete KRT19 to capture CXCL12 and protect against immune attack.
T细胞的排除导致胰腺导管腺癌（PDA）的免疫逃逸。T细胞排除是由T细胞上的CXCR4与其配体CXCL12之间的相互作用介导的，CXCL12与PDA细胞表面的角蛋白-19（KRT19）结合。PDA细胞分泌KRT19对这一过程至关重要，但不同寻常的是KRT19缺乏内质网（ER）导向信号肽（SP）。通过使用内质网限制的TurboID系统进行生物素化以及在PDA细胞中进行分裂GFP分析，我们证明KRT19通过其“头部”结构域进入内质网。此外，KRT19被证明与信号识别颗粒相互作用，并且其分泌对经典蛋白质分泌抑制剂敏感。在体内，用表达内质网-TurboID的PDA细胞形成的小鼠肿瘤含有生物素化的KRT19。相比之下，与KRT19在PDA细胞表面共定位的角蛋白-8（KRT8）不进入内质网。相反，KRT8可能通过分泌自噬与KRT19形成复合物而被外化。因此，尽管缺乏经典的信号肽，PDA细胞仍分泌KRT19以捕获CXCL12并抵御免疫攻击。
