2024 article
TAK1 inhibition translocates pore-forming proteins, MLKL and gasdermins into mitochondria to generate reactive oxygen species
Gonzalez-Calderon, R., Lopez-Perez, W., Sai, K., & Ninomiya-Tsuji, J. (2024, March). JOURNAL OF BIOLOGICAL CHEMISTRY, Vol. 300, pp. S555–S555.
open access via www.jbc.org (publisher PDF)Mitogen-activated protein kinase kinase kinase 7 (MAP3K7), known as TAK1, is a central mediator of intracellular host defense signaling promoting inflammatory gene expression. Hence, TAK1 is a prime target of intracellular bacterial effectors in blocking inflammatory gene expression. However, when TAK1 is inhibited, host cells alternatively induce mitochondrial reactive oxygen species (ROS) to kill intracellular bacteria, which ultimately induces host cell death to prevent bacteria spreading. In the current study, we delineate the mechanism of how host cells elevate ROS and induce cell death in response to TAK1 inhibition in bone marrow derived macrophage (BMDMs). TAK1 inhibition activates multiple cell death pathways, namely caspase 8-dependent apoptosis and pyroptosis, and receptor interacting protein kinase 3 (RIPK3)-dependent necroptosis. While these pathways lead to host cell death, we found that mixed lineage kinase-like (MLKL) downstream RIPK3 and gasdermins (GSDMD and GSDME) downstream caspase 8 were translocated to mitochondria upon TAK1 inhibition. Deletion of both MLKL and gasdermins partially blocked TAK1 inhibition-induced mitochondrial ROS and exacerbated intracellular bacteria growth colonization. These results suggest that these cell-killing pore forming proteins play an alternative host defense role to prevent intracellular pathogen colonization by modulating mitochondria. Additionally, we found that ablation of both caspase 8 (apoptosis and pyroptosis) and RIPK3 (necroptosis) did not abolish TAK1 inhibition-induced cell death in BMDMs. Furthermore, we found that mice having TAK1, caspase 8 and RIPK3 triple deletion died within 8 days. These results suggest that an unidentified caspase 8 and RIPK3-independent cell killing pathway(s) is activated by TAK1 inhibition, which is another host defense mechanism. Our results demonstrate that apoptosis, pyroptosis, necroptosis together with unidentified pathways cooperatively act as the host defense in response to bacterial TAK1 inhibition. NIH R35GM139601.