Beclin 2 negatively regulates innate immune signaling and tumor development
Motao Zhu, … , Guangjun Nie, Rong-Fu Wang
Motao Zhu, … , Guangjun Nie, Rong-Fu Wang
Published August 31, 2020
Citation Information: J Clin Invest. 2020;130(10):5349-5369. https://doi.org/10.1172/JCI133283.
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Research Article Cell biology Inflammation

Beclin 2 negatively regulates innate immune signaling and tumor development

Abstract

Beclin 2 plays a critical role in metabolic regulation and obesity, but its functions in innate immune signaling and cancer development remain largely unknown. Here, we identified Beclin 2 as a critical negative regulator of inflammation and lymphoma development. Mice with homozygous ablation of BCL2-interacting protein 2 (Becn2) developed splenomegaly and lymphadenopathy and markedly increased ERK1/2 and NF-κB signaling for proinflammatory cytokine production. Beclin 2 targeted the key signaling kinases MEKK3 and TAK1 for degradation through an ATG9A-dependent, but ATG16L/Beclin 1/LC3–independent, autophagic pathway. Mechanistically, Beclin 2 recruited MEKK3 or TAK1 through ATG9A to form a complex (Beclin 2-ATG9A-MEKK3) on ATG9A+ vesicles upon ULK1 activation. Beclin 2 further interacted with STX5 and STX6 to promote the fusion of MEKK3- or TAK1-associated ATG9A+ vesicles to phagophores for subsequent degradation. Importantly, Becn2-deficient mice had a markedly increased incidence of lymphoma development, with persistent STAT3 activation. Myeloid-specific ablation of MEKK3 (Map3k3) completely rescued the phenotypes (splenomegaly, higher amounts of proinflammatory cytokines, and cancer incidence) of Becn2-deficient mice. Hence, our findings have identified an important role of Beclin 2 in the negative regulation of innate immune signaling and tumor development through an ATG9A-dependent, but ATG16L/Beclin 1/LC3–independent, autophagic pathway, thus providing a potential target for the treatment of inflammatory diseases and cancer.

Authors

Motao Zhu, Guangtong Deng, Peng Tan, Changsheng Xing, Cuiping Guan, Chongming Jiang, Yinlong Zhang, Bo Ning, Chaoran Li, Bingnan Yin, Kaifu Chen, Yuliang Zhao, Helen Y. Wang, Beth Levine, Guangjun Nie, Rong-Fu Wang

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Figure 5

Beclin 2 mediates degradation of TAK1 and MEKK3 through ATG16L/LC3/Beclin 1–independent pathway.

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Beclin 2 mediates degradation of TAK1 and MEKK3 through ATG16L/LC3/Becli...
(A–C) WT 293T cells and sgRNA-guided ATG16L-KO (A), MAP1LC3B-KO (B), or BECN1-KO (C) 293T cell clones were transfected with HA-TAK1 or HA-MEKK3 alone or together with Flag–Beclin 2 plasmid, followed by immunoblotting with the indicated antibodies. Samples shown in B were run on parallel gels contemporaneously. Right panels: quantitative analysis of HA-TAK1 and HA-MEKK3 expression and degradation percentages in WT and KO cells after normalization based on band intensity of 3 independent experiments. Data are plotted as mean ± SEM. (D) Cell lysates of 293T cells were immunoprecipitated using specific antibodies against each protein, then immunoblotted using indicated antibodies. Statistical differences between EmpVec-transfected and Flag–Beclin 2–transfected cells were calculated using Student’s unpaired t test (A–C). Statistical differences of degradation percentages between WT and KO groups were calculated using 1-way ANOVA with Dunnett’s multiple comparisons test (A–C). *P < 0.05; **P < 0.01; ***P < 0.001.