Biochemistry Section, National Institute for Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
Mol Cell Biol. 2013 Sep;33(18):3675-88. doi: 10.1128/MCB.00079-13. Epub 2013 Jul 22.
During autophagy, a double membrane envelops cellular material for trafficking to the lysosome. Human beclin-1 and its yeast homologue, Atg6/Vps30, are scaffold proteins bound in a lipid kinase complex with multiple cellular functions, including autophagy. Several different Atg6 complexes exist, with an autophagy-specific form containing Atg14. However, the roles of Atg14 and beclin-1 in the activation of this complex remain unclear. We here addressed the mechanism of beclin-1 complex activation and reveal two critical steps in this pathway. First, we identified a unique domain in beclin-1, conserved in the yeast homologue Atg6, which is involved in membrane association and, unexpectedly, controls autophagosome size and number in yeast. Second, we demonstrated that human Atg14 is critical in controlling an autophagy-dependent phosphorylation of beclin-1. We map these novel phosphorylation sites to serines 90 and 93 and demonstrate that phosphorylation at these sites is necessary for maximal autophagy. These results help clarify the mechanism of beclin-1 and Atg14 during autophagy.
在自噬过程中，双层膜将细胞物质包裹起来，运送到溶酶体。人类 beclin-1 和其酵母同源物 Atg6/Vps30 是与多种细胞功能（包括自噬）相关的脂质激酶复合物中的支架蛋白。存在几种不同的 Atg6 复合物，其中一种自噬特异性形式包含 Atg14。然而，Atg14 和 beclin-1 在该复合物激活中的作用仍不清楚。我们在这里研究了 beclin-1 复合物的激活机制，并揭示了该途径中的两个关键步骤。首先，我们鉴定了 beclin-1 中的一个独特结构域，该结构域在酵母同源物 Atg6 中保守，参与膜结合，并且出人意料的是，控制酵母中自噬体的大小和数量。其次，我们证明人类 Atg14 对控制 beclin-1 的自噬依赖性磷酸化至关重要。我们将这些新的磷酸化位点定位到丝氨酸 90 和 93，并证明这些位点的磷酸化对于最大程度的自噬是必需的。这些结果有助于阐明自噬过程中 beclin-1 和 Atg14 的作用机制。
