B Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Sci Signal. 2010 May 25;3(123):ra42. doi: 10.1126/scisignal.2000751.
Autophagy delivers cytoplasmic constituents to autophagolysosomes and is linked to both innate and adaptive immunity. Toll-like receptor 4 (TLR4) signaling induces autophagy and recruits Beclin-1, the mammalian homolog of yeast Atg6, to the receptor complex. We found that tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6)-mediated, Lys(63) (K63)-linked ubiquitination of Beclin-1 is critical for TLR4-triggered autophagy in macrophages. Two TRAF6-binding motifs in Beclin-1 facilitated the binding of TRAF6 and the ubiquitination of Beclin-1. Lys(117), which is strategically located in the Bcl-2 homology 3 (BH3) domain of Beclin-1, was a major site for K63-linked ubiquitination. The deubiquitinating enzyme A20 reduced the extent of K63-linked ubiquitination of Beclin-1 and limited the induction of autophagy in response to TLR signaling. Treatment of macrophages with either interferon-gamma or interleukin-1 also triggered the K63-linked ubiquitination of Beclin-1 and the formation of autophagosomes. These results indicate that the status of K63-linked ubiquitination of Beclin-1 plays a key role in regulating autophagy during inflammatory responses.
自噬将细胞质成分输送到自噬溶酶体，并与先天免疫和适应性免疫有关。Toll 样受体 4（TLR4）信号诱导自噬，并将哺乳动物同源物 Beclin-1（酵母 Atg6 的同源物）募集到受体复合物。我们发现肿瘤坏死因子受体（TNFR）相关因子 6（TRAF6）介导的 Beclin-1 赖氨酸（63）（K63）连接的泛素化对于巨噬细胞中 TLR4 触发的自噬至关重要。Beclin-1 中的两个 TRAF6 结合基序促进了 TRAF6 的结合和 Beclin-1 的泛素化。Beclin-1 的 Bcl-2 同源结构域 3（BH3）结构域中具有战略意义的赖氨酸（117）是 K63 连接泛素化的主要位点。去泛素化酶 A20 降低了 Beclin-1 的 K63 连接泛素化程度，并限制了 TLR 信号诱导的自噬。用干扰素-γ或白细胞介素-1 处理巨噬细胞也会触发 Beclin-1 的 K63 连接泛素化和自噬体的形成。这些结果表明，Beclin-1 的 K63 连接泛素化状态在炎症反应期间调节自噬中起着关键作用。
