RÉSUMÉ
Human NLRP1 (NACHT, LRR, and PYD domain-containing protein 1) is an innate immune sensor predominantly expressed in the skin and airway epithelium. Here, we report that human NLRP1 senses the ultraviolet B (UVB)- and toxin-induced ribotoxic stress response (RSR). Biochemically, RSR leads to the direct hyperphosphorylation of a human-specific disordered linker region of NLRP1 (NLRP1DR) by MAP3K20/ZAKα kinase and its downstream effector, p38. Mutating a single ZAKα phosphorylation site in NLRP1DR abrogates UVB- and ribotoxin-driven pyroptosis in human keratinocytes. Moreover, fusing NLRP1DR to CARD8, which is insensitive to RSR by itself, creates a minimal inflammasome sensor for UVB and ribotoxins. These results provide insight into UVB sensing by human skin keratinocytes, identify several ribotoxins as NLRP1 agonists, and establish inflammasome-driven pyroptosis as an integral component of the RSR.
Sujet(s)
Inflammasomes , MAP Kinase Kinase Kinases , Protéines NLR , Pyroptose , Ribosomes , Stress physiologique , Anisomycine/toxicité , Protéines adaptatrices de signalisation CARD/métabolisme , Humains , Inflammasomes/effets des médicaments et des substances chimiques , Inflammasomes/métabolisme , Inflammasomes/effets des radiations , Kératinocytes/effets des médicaments et des substances chimiques , Kératinocytes/métabolisme , Kératinocytes/effets des radiations , MAP Kinase Kinase Kinases/métabolisme , Mutation , Protéines NLR/génétique , Protéines NLR/métabolisme , Protéines tumorales/métabolisme , Phosphorylation/effets des médicaments et des substances chimiques , Phosphorylation/effets des radiations , Pyroptose/effets des médicaments et des substances chimiques , Pyroptose/effets des radiations , Ribosomes/effets des médicaments et des substances chimiques , Ribosomes/effets des radiations , Rayons ultravioletsRÉSUMÉ
Cilia and flagella are conserved eukaryotic organelles important for motility and sensory. The RanGTPase, best known for nucleocytoplasmic transport functions, may also play a role in protein trafficking into the specialized flagellar/ciliary compartments, although the regulatory mechanisms controlling Ran activity at the flagellum remain unclear. The unicellular parasite Trypanosoma brucei contains a single flagellum necessary for cell movement, division and morphogenesis. Correct flagellum functions require flagellar attachment to the cell body, which is mediated by a specialized flagellum attachment zone (FAZ) complex that is assembled together with the flagellum during the cell cycle. We have previously identified the leucine-rich-repeat protein 1 LRRP1 on a bi-lobe structure at the proximal base of flagellum and FAZ. LRRP1 is essential for bi-lobe and FAZ biogenesis, consequently affecting flagellum-driven cell motility and division. Here, we show that LRRP1 forms a complex with Ran and a Ran-binding protein, and regulates Ran-GTP hydrolysis in T. brucei. In addition to mitotic inhibition, depletion of Ran inhibits FAZ assembly in T. brucei, supporting the presence of a conserved mechanism that involves Ran in the regulation of flagellum functions in an early divergent eukaryote.