Selective VPS34 inhibitor blocks autophagy and uncovers a role for NCOA4 in ferritin degradation and iron homeostasis in vivo
Selective VPS34 inhibitor blocks autophagy and uncovers a role for NCOA4 in ferritin degradation and iron homeostasis in vivo
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DOI：
10.1038/ncb3053
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发表时间：
2014-11-01
影响因子：
21.3
通讯作者：
Murphy, Leon O.
中科院分区：
文献类型：
--
作者：
Dowdle, William E.;Nyfeler, Beat;Murphy, Leon O.
细胞依靠自噬来清除错误折叠的蛋白质和受损的细胞器以维持细胞稳态。在本研究中，我们使用新型自噬抑制剂 PIK-III 来筛选自噬底物。 PIK-III 是 VPS34 的选择性抑制剂，可结合相关激酶（如 PI(3) K α）中不存在的独特疏水口袋。 PIK-III 强烈抑制自噬和 LC3 的从头脂质化，并导致自噬底物的稳定。通过对 PIK-III 处理的细胞进行泛素亲和蛋白质组学，我们鉴定了包括 NCOA4 在内的底物，NCOA4 在 ATG7 缺陷的细胞中积累并与自溶酶体共定位。 NCOA4 直接结合铁蛋白重链 1 (FTH1)，在饥饿或缺铁后将相对分子质量为 450,000 的铁结合铁蛋白复合物靶向自溶酶体。有趣的是，Ncoa4(-/-)小鼠在脾脏巨噬细胞中表现出铁的大量积累，这对于重新利用被吞噬的红细胞中的铁至关重要。总而言之，这项研究的结果提供了铁蛋白选择性自噬的新机制，并揭示了自噬和 NCOA4 在体内铁稳态控制中先前未被认识到的作用。
Cells rely on autophagy to clear misfolded proteins and damaged organelles to maintain cellular homeostasis. In this study we use the new autophagy inhibitor PIK-III to screen for autophagy substrates. PIK-III is a selective inhibitor of VPS34 that binds a unique hydrophobic pocket not present in related kinases such as PI(3) K alpha. PIK-III acutely inhibits autophagy and de novo lipidation of LC3, and leads to the stabilization of autophagy substrates. By performing ubiquitin-affinity proteomics on PIK-III-treated cells we identified substrates including NCOA4, which accumulates in ATG7-deficient cells and co-localizes with autolysosomes. NCOA4 directly binds ferritin heavy chain-1 (FTH1) to target the iron-binding ferritin complex with a relative molecular mass of 450,000 to autolysosomes following starvation or iron depletion. Interestingly, Ncoa4(-/-) mice exhibit a profound accumulation of iron in splenic macrophages, which are critical for the reutilization of iron from engulfed red blood cells. Taken together, the results of this study provide a new mechanism for selective autophagy of ferritin and reveal a previously unappreciated role for autophagy and NCOA4 in the control of iron homeostasis in vivo.