School of Pharmacy, Fudan University, Shanghai 201203, China.
Proc Natl Acad Sci U S A. 2013 Apr 23;110(17):6841-6. doi: 10.1073/pnas.1217692110. Epub 2013 Apr 8.
Autophagy is a stress-induced catabolic process in which cytoplasmic components, sequestered in double-membrane autophagic vesicles (AVs) or autophagosomes, are delivered to lysosomes for degradation and recycling [Kroemer G, Mariño G, Levine B (2010) Mol Cell 40(2):280-293]. Activity of the class III phosphatidylinositol-3-OH-kinase (PI3K) vacuolar protein-sorting (Vps) 34, bound to coiled-coil moesin-like B-cell lymphoma 2 (Bcl-2)-interacting protein Beclin-1, is required for phosphoinositide generation, essential for AV formation in autophagy [Cuervo AM (2010) Nat Cell Biol 12(8):735-737]. However, how autophagy-inducing stress regulates Vps34 activity has not been fully elucidated. Our findings demonstrate that autophagy-inducing stress increases intracellular levels of acetylated inducible heat shock protein (hsp) 70, which binds to the Beclin-1-Vps34 complex. Acetylated hsp70 also recruits E3 ligase for SUMOylation, KRAB-ZFP-associated protein 1 (KAP1), inducing Lys840 SUMOylation and increasing Vps34 activity bound to Beclin 1. Knockdown of hsp70 abolished the Beclin-1-Vps34 complex formation, as well as inhibited KAP1 binding to Vps34 and AV formation. Notably, autophagy-inducing stress due to histone deacetylase inhibitor treatment induced AV formation in the wild-type but not hsp70.1/3 knockout mouse embryonic fibroblasts MEFs. These findings highlight a regulatory mechanism of Vps34 activity, which involves acetylated hsp70 and KAP1-dependent SUMOylation of Vps34 bound to Beclin 1.
自噬是一种应激诱导的分解代谢过程，其中细胞质成分被隔离在双层自噬小泡（AVs）或自噬体中，然后递送至溶酶体进行降解和再循环[Kroemer G、Mariño G、Levine B（2010）Mol Cell 40（2）：280-293]。与卷曲螺旋样 B 细胞淋巴瘤 2（Bcl-2）相互作用蛋白 Beclin-1 结合的 III 类磷脂酰肌醇-3-OH-激酶（PI3K）液泡分选（Vps）34 的活性是磷酸肌醇生成所必需的，对自噬中 AV 的形成至关重要[Cuervo AM（2010）Nat Cell Biol 12（8）：735-737]。然而，自噬诱导应激如何调节 Vps34 活性尚未完全阐明。我们的研究结果表明，自噬诱导应激会增加乙酰化诱导热休克蛋白（hsp）70 的细胞内水平，后者与 Beclin-1-Vps34 复合物结合。乙酰化 hsp70 还募集 E3 连接酶进行 SUMO 化，即 KRAB-ZFP 相关蛋白 1（KAP1），诱导 Vps34 上 Lys840 的 SUMO 化，从而增加与 Beclin 1 结合的 Vps34 活性。hsp70 的敲低消除了 Beclin-1-Vps34 复合物的形成，以及抑制 KAP1 与 Vps34 的结合和 AV 的形成。值得注意的是，由于组蛋白去乙酰化酶抑制剂处理引起的自噬诱导应激在野生型但不是 hsp70.1/3 敲除小鼠胚胎成纤维细胞（MEFs）中诱导了 AV 的形成。这些发现强调了 Vps34 活性的调节机制，该机制涉及与 Beclin 1 结合的 Vps34 的乙酰化 hsp70 和 KAP1 依赖性 SUMO 化。
