Role of the p97 ATPase in endocytosis

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 -乙基马酰亚胺敏感融合蛋白），它通过分解SNARE复合体来促进膜融合。在ERAD中，p97将错误折叠的蛋白质从内质网膜上错位，以促进蛋白酶体对它们的周转。在这里，我们通过建立早期内体自身抗原1 （EEA1）作为新的p97底物，确定了p97在内吞运输中的新功能。我们证明p97的一部分定位于早期内体膜，在那里它通过n端C2H2锌指结构域与EEA1结合。siRNA或药物抑制剂抑制p97可导致早期内体聚集和扩大，这与内吞货物的运输模式改变有关。在机制上，我们发现p97抑制导致EEA1在核内体膜上的自结合增加。我们认为p97可能通过调控EEA1的寡聚状态来调节早期内体的大小。我们最近进一步证明EEA1在细胞中经历单泛素化，这种修饰可以调节早期内体的大小。

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. We recently further demonstrate that EEA1 undergoes mono-ubiquitination in the cell and this modification can regulate the size of early endosomes.