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 8

Ablation of Map3k3 rescues the phenotypes observed in Becn2-KO mice.

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Ablation of Map3k3 rescues the phenotypes observed in Becn2-KO mice. (A)...
(A) Spleens and lymph nodes of 6- to 8-week-old WT, Becn2-KO, Map3k3ΔM/ΔM:Becn2-KO, and Map3k7ΔM/ΔM:Becn2-KO mice. (B) H&E staining of spleens from WT, Becn2-KO, Map3k3ΔM/ΔM:Becn2-KO, and Map3k7ΔM/ΔM:Becn2-KO mice. Scale bars: 1 mm. Representative images (A and B) are shown for each group (n = 5 mice per group). (C) Total numbers of splenocytes and flow cytometry–based quantification of B220+ and CD3+ cell populations in spleens counted from 6- to 8-week-old Becn2-KO and WT mice (n = 5 mice per group). (D) Basal IL-6 levels in 8- to 12-week-old mouse sera (n = 8 mice per group). (E) Cytokine levels in serum samples from 6- to 8- week-old WT, Becn2-KO, and Becn2-KO:Map3k3 ΔM/ΔM mice after high-dose LPS (i.p. 30 mg/kg) treatment (n = 5 mice per group). (F) IL-6 production by WT, Becn2-KO, Map3k3 ΔM/ΔM:Becn2-KO, and Map3k7ΔM/ΔM:Becn2-KO macrophages treated with LPS (100 ng/mL) for 0, 2, 4, or 6 hours (mean ± SEM). (G) Immunoblot analysis of macrophages from WT, Becn2-KO, Map3k3ΔM/ΔM:Becn2-KO, and Map3k7ΔM/ΔM:Becn2-KO mice treated with LPS (100 ng/mL) for the indicated periods. Data (F and G) are representative of 3 independent experiments. Statistical differences between groups were calculated using 1-way ANOVA with Dunnett’s multiple comparisons test (C–F). *P < 0.05; **P < 0.01; ***P < 0.001.