Cancer Research UK London Research Institute, WC2A 3PF London, England, UK.
J Cell Biol. 2012 May 28;197(5):659-75. doi: 10.1083/jcb.201111079. Epub 2012 May 21.
Autophagy is a bulk degradation process characterized by the formation of double membrane vesicles called autophagosomes. The exact molecular mechanism of autophagosome formation and the origin of the autophagosomal membrane remain unclear. We screened 38 human Tre-2/Bub2/Cdc16 domain-containing Rab guanosine triphosphatase-activating proteins (GAPs) and identified 11 negative regulators of starvation-induced autophagy. One of these putative RabGAPs, TBC1D14, colocalizes and interacts with the autophagy kinase ULK1. Overexpressed TBC1D14 tubulates ULK1-positive recycling endosomes (REs), impairing their function and inhibiting autophagosome formation. TBC1D14 binds activated Rab11 but is not a GAP for Rab11, and loss of Rab11 prevents TBC1D14-induced tubulation of REs. Furthermore, Rab11 is required for autophagosome formation. ULK1 and Atg9 are found on Rab11- and transferrin (Tfn) receptor (TfnR)-positive recycling endosomes. Amino acid starvation causes TBC1D14 to relocalize from REs to the Golgi complex, whereas TfnR and Tfn localize to forming autophagosomes, which are ULK1 and LC3 positive. Thus, TBC1D14- and Rab11-dependent vesicular transport from REs contributes to and regulates starvation-induced autophagy.
自噬是一种批量降解过程，其特征是形成双层膜囊泡，称为自噬体。自噬体形成的确切分子机制和自噬体膜的起源仍不清楚。我们筛选了 38 个人类 Tre-2/Bub2/Cdc16 结构域包含 Rab 鸟嘌呤核苷酸三磷酸酶激活蛋白 (GAPs)，并鉴定出 11 种饥饿诱导自噬的负调控因子。这些假定的 RabGAP 之一，TBC1D14，与自噬激酶 ULK1 共定位并相互作用。过表达的 TBC1D14 使 ULK1 阳性再循环内体 (REs) 管化，损害其功能并抑制自噬体形成。TBC1D14 结合激活的 Rab11，但不是 Rab11 的 GAP，并且 Rab11 的缺失可防止 TBC1D14 诱导的 REs 管化。此外，Rab11 是自噬体形成所必需的。ULK1 和 Atg9 存在于 Rab11 和转铁蛋白 (Tfn) 受体 (TfnR) 阳性再循环内体上。氨基酸饥饿导致 TBC1D14 从 RE 重新定位到高尔基复合体，而 TfnR 和 Tfn 定位到正在形成的自噬体，这些自噬体是 ULK1 和 LC3 阳性的。因此，TBC1D14 和 Rab11 依赖性从 RE 到高尔基体的囊泡运输有助于并调节饥饿诱导的自噬。
