Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Cell Res. 2012 Feb;22(2):346-59. doi: 10.1038/cr.2011.80. Epub 2011 May 10.
The AAA (ATPase-associated with various cellular activities) ATPase p97 acts on diverse substrate proteins to partake in various cellular processes such as membrane fusion and endoplasmic reticulum-associated degradation (ERAD). In membrane fusion, p97 is thought to function in analogy to the related ATPase NSF (N-ethylmaleimide-sensitive fusion protein), which promotes membrane fusion by disassembling a SNARE complex. In ERAD, p97 dislocates misfolded proteins from the ER membrane to facilitate their turnover by the proteasome. Here, we identify a novel function of p97 in endocytic trafficking by establishing the early endosomal autoantigen 1 (EEA1) as a new p97 substrate. We demonstrate that a fraction of p97 is localized to the early endosome membrane, where it binds EEA1 via the N-terminal C2H2 zinc finger domain. Inhibition of p97 either by siRNA or a pharmacological inhibitor results in clustering and enlargement of early endosomes, which is associated with an altered trafficking pattern for an endocytic cargo. Mechanistically, we show that p97 inhibition causes increased EEA1 self-association at the endosome membrane. We propose that p97 may regulate the size of early endosomes by governing the oligomeric state of EEA1.
AAA（与各种细胞活动相关的 ATP 酶）ATP 酶 p97 作用于多种底物蛋白，参与多种细胞过程，如膜融合和内质网相关降解（ERAD）。在膜融合中，p97 的功能被认为类似于相关的 ATP 酶 NSF（N-乙基马来酰亚胺敏感融合蛋白），它通过解组装 SNARE 复合物来促进膜融合。在 ERAD 中，p97 将错误折叠的蛋白质从内质网膜上移位，以促进它们被蛋白酶体降解。在这里，我们通过确定早期内体自身抗原 1（EEA1）为新的 p97 底物，鉴定了 p97 在胞吞作用中的新功能。我们证明，一部分 p97 定位于早期内体膜上，通过 N 端 C2H2 锌指结构域与 EEA1 结合。通过 siRNA 或药理学抑制剂抑制 p97 会导致早期内体的聚集和增大，这与胞吞货物的运输模式改变有关。在机制上，我们表明 p97 抑制会导致内体膜上 EEA1 自缔合增加。我们提出，p97 可能通过调节 EEA1 的寡聚状态来调节早期内体的大小。
