Bruton tyrosine kinase deficiency augments NLRP3 inflammasome activation and causes IL-1β–mediated colitis
Liming Mao, Atsushi Kitani, Eitaro Hiejima, Kim Montgomery-Recht, Wenchang Zhou, Ivan Fuss, Adrian Wiestner, Warren Strober
Liming Mao, Atsushi Kitani, Eitaro Hiejima, Kim Montgomery-Recht, Wenchang Zhou, Ivan Fuss, Adrian Wiestner, Warren Strober
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Research Article Gastroenterology

Bruton tyrosine kinase deficiency augments NLRP3 inflammasome activation and causes IL-1β–mediated colitis

Abstract

Bruton tyrosine kinase (BTK) is present in a wide variety of cells and may thus have important non–B cell functions. Here, we explored the function of this kinase in macrophages with studies of its regulation of the NLR family, pyrin domain–containing 3 (NLRP3) inflammasome. We found that bone marrow–derived macrophages (BMDMs) from BTK-deficient mice or monocytes from patients with X-linked agammaglobulinemia (XLA) exhibited increased NLRP3 inflammasome activity; this was also the case for BMDMs exposed to low doses of BTK inhibitors such as ibrutinib and for monocytes from patients with chronic lymphocytic leukemia being treated with ibrutinib. In mechanistic studies, we found that BTK bound to NLRP3 during the priming phase of inflammasome activation and, in doing so, inhibited LPS- and nigericin-induced assembly of the NLRP3 inflammasome during the activation phase of inflammasome activation. This inhibitory effect was caused by BTK inhibition of protein phosphatase 2A–mediated (PP2A-mediated) dephosphorylation of Ser5 in the pyrin domain of NLRP3. Finally, we show that BTK-deficient mice were subject to severe experimental colitis and that such colitis was normalized by administration of anti–IL-β or anakinra, an inhibitor of IL-1β signaling. Together, these studies strongly suggest that BTK functions as a physiologic inhibitor of NLRP3 inflammasome activation and explain why patients with XLA are prone to develop Crohn’s disease.

Authors

Liming Mao, Atsushi Kitani, Eitaro Hiejima, Kim Montgomery-Recht, Wenchang Zhou, Ivan Fuss, Adrian Wiestner, Warren Strober

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Figure 5

BTK interacts with PP2A and upregulates PP2A Tyr307 phosphorylation, and BTK-KO cells produce decreased amounts of IL-1β in cells with PP2A knockdown.

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BTK interacts with PP2A and upregulates PP2A Tyr307 phosphorylation, and...
(A) HEK293T cells were transfected with plasmids as indicated, and 24 hours later, the cells were lysed and lysates subjected to IP with anti-Flag antibody and then WB. Data are representative of 2 independent experiments. (B) BMDMs from WT and BTK-KO mice were stimulated with LPS (200 ng/mL) for 3 hours, after which the cells were lysed and lysates subjected to IP and WB. (C–E) BMDMs were transfected with siRNA specific for PP2A (Ppp2aca) as indicated, and 48 hours later, the cells were primed with LPS (200 ng/mL) for 3 hours and then stimulated with nigericin for 30 minutes. Cells were then lysed and lysates subjected to WB for BTK, PP2A, and NLRP3 (C); the above culture supernatants were collected for IL-1β (D) and IL-6 (E) ELISAs. *P < 0.05 and **P < 0.01, by 1-way ANOVA with multiple comparisons test. Data are presented as the mean ± SD and are representative of 2 independent experiments.