Pathogenic mycobacteria, such as Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium marinum, can trigger NLRP3 inflammasome activation leading to maturation and secretion of interleukin 1β (IL‐1β). However, the mycobacterial factors involved in the activation of NLRP3 inflammasome are not fully understood. Here, we identified that the PPE family protein PPE13 was responsible for the induction of IL‐1β secretion in a NLRP3 inflammasome‐dependent manner. We found that the recombinant Mycobacterium smegmatis expressing PPE13 activates NLRP3 inflammasome, thereby inducing caspase‐1 cleavage and IL‐1β secretion in J774A.1, BMDMs, and THP‐1 macrophages. To examine whether this inflammasome activation was triggered by PPE13 rather than components of M. smegmatis, PPE13 was introduced into the aforementioned macrophages by lentivirus as a delivery vector. Similarly, this led to the activation of NLRP3 inflammasome, indicating that PPE13 is a direct activator of NLRP3 cascade. We further demonstrated that the NLRP3 complex activated the inflammasome cascade, and the assembly of this complex was facilitated by PPE13 through interacting with the LRR and NATCH domains of NLRP3. Finally, we found that all PPE13 proteins isolated from M. tuberculosis, M. bovis, and M. marinum can activate NLRP3 inflammasome through binding to NLRP3, which requires C‐terminal repetitive MPTR domain of PPE13. Thus, we, for the first time, revealed that PPE13 triggers the inflammasome‐response by interacting with the MPTR domain of PPE13 and the LRR and NATCH domains of NLRP3. These findings provide a novel perspective on the function of PPE proteins in the immune system during mycobacteria invasion.

中文翻译：

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分枝杆菌 PPE13 通过与 NLRP3 的 NATCH 和 LRR 结构域相互作用激活炎症小体

致病性分枝杆菌，如结核分枝杆菌、牛分枝杆菌和海分枝杆菌，可触发 NLRP3 炎性体激活，导致白细胞介素 1β (IL-1β) 的成熟和分泌。然而，参与 NLRP3 炎症小体激活的分枝杆菌因子尚不完全清楚。在这里，我们发现 PPE 家族蛋白 PPE13 负责以 NLRP3 炎症小体依赖性方式诱导 IL-1β 分泌。我们发现表达 PPE13 的重组耻垢分枝杆菌激活 NLRP3 炎性体，从而诱导 J774A.1、BMDM 和 THP-1 巨噬细胞中的 caspase-1 裂解和 IL-1β 分泌。为了检查这种炎症小体激活是否由 PPE13 而不是耻垢分枝杆菌的成分触发，PPE13通过慢病毒作为递送载体被引入上述巨噬细胞。同样，这导致 NLRP3 炎症小体的激活，表明 PPE13 是 NLRP3 级联的直接激活剂。我们进一步证明 NLRP3 复合物激活了炎性体级联反应，并且 PPE13 通过与 NLRP3 的 LRR 和 NATCH 结构域相互作用促进了该复合物的组装。最后，我们发现从结核分枝杆菌、牛分枝杆菌和海洋分枝杆菌中分离的所有 PPE13 蛋白都可以通过与 NLRP3 结合激活 NLRP3 炎性体，这需要 PPE13 的 C 端重复 MPTR 结构域。因此，我们首次发现 PPE13 通过与 PPE13 的 MPTR 结构域以及 NLRP3 的 LRR 和 NATCH 结构域相互作用来触发炎症小体反应。