Regulatory mechanism of Rab14 and its effector proteins in post-Golgi membrane trafficking

在这里，我们报道Rab14以gtp依赖的方式与RUFY1/Rabip4结合，RUFY1/Rabip4最初被确定为Rab4效应物。Rab14在外周核内体上与Rab4共定位良好。Rab14的缺失，而不是Rab4的缺失，导致RUFY1从内体膜分离。RUFY1与Rab14或Rab4共表达可诱导核内体聚集和扩大，而缺乏Rab4结合区的RUFY1突变体即使与Rab14或Rab4共表达也不会诱导核内体结构的显著形态变化。这些结果表明Rab14和Rab4与RUFY1一起顺序起作用；Rab14是RUFY1募集到内体膜上所必需的，随后RUFY1与Rab4的相互作用可能允许内体系结和融合。Rab14或RUFY1以及Rab4的缺失会抑制内吞噬转铁蛋白的有效再循环，这表明Rab14和Rab4通过与其双重效应物RUFY1的合作相互作用来调节内体功能。

Here, we report that Rab14 binds in a GTP-dependent manner to RUFY1/Rabip4, which had been originally identified as a Rab4 effector. Rab14 colocalizes well with Rab4 on peripheral endosomes. Depletion of Rab14, but not Rab4, causes dissociation of RUFY1 from endosomal membranes. Coexpression of RUFY1 with either Rab14 or Rab4 induces clustering and enlargement of endosomes, while a RUFY1 mutant lacking the Rab4-binding region does not induce a significant morphological change in the endosomal structures even when coexpressed with Rab14 or Rab4. These findings suggest that Rab14 and Rab4 act sequentially, together with RUFY1 ; Rab14 is required for recruitment of RUFY1 onto endosomal membranes, and subsequent RUFY1 interaction with Rab4 may allow endosomal tethering and fusion. Depletion of Rab14 or RUFY1, as well as Rab4, inhibits efficient recycling of endocytosed transferrin, suggesting that Rab14 and Rab4 regulate endosomal functions through cooperative interactions with their dual effector, RUFY1.