Autophagosome targeting and membrane curvature sensing by Barkor/Atg14(L)
Autophagosome targeting and membrane curvature sensing by Barkor/Atg14(L)
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DOI：
10.1073/pnas.1016472108
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发表时间：
2011-05-10
影响因子：
11.1
通讯作者：
Zhong, Qing
中科院分区：
文献类型：
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作者：
Fan, Weiliang;Nassiri, Ashley;Zhong, Qing
III类磷脂酰肌醇3-激酶（PI 3 KC 3）对于自噬体的生物发生至关重要。长期以来，人们一直推测自噬体膜成核，但这种成核活性的生化机制仍然没有解决。我们最近发现Barkor/Atg 14（L）是PI 3 KC 3在自噬体膜上的靶向因子。在这里，我们表明，我们已经表征了Barkor/Atg 14（L）的区域所需的自噬体靶向和确定的BATS [Barkor/Atg 14（L）自噬体靶向序列]结构域在Barkor的羧基末端。生物信息学和突变分析显示，BATS结构域通过内在的两亲性α螺旋的疏水表面结合到自噬体膜。BATS puncta与Atg 16和LC 3重叠，部分与DFCP 1重叠，以应激诱导的方式。异位表达的BATS聚集在高度弯曲的小管上，这可能代表中间的自噬结构。Barkor/Atg 14（L）的PI 3 KC 3募集和自噬刺激需要BATS结构域。此外，我们的生化分析表明，BATS结构域直接结合到膜上，并且它有利于由磷脂酰肌醇3-磷酸[PtdIns（3）P]和磷脂酰肌醇4，5-二磷酸[PtdIns（4，5）P2]组成的膜。通过优先结合到掺入PtdIns（3）P而不是PtdIns（4，5）P2的弯曲膜，BATS结构域能够感测膜曲率。因此，我们提出了一种新的PI 3 KC 3自噬体膜成核模型，其中其自噬体特异性适配器Barkor通过其BATS结构域在高度弯曲的PtdIns（3）P富集的自噬膜上积累以感知和维持膜曲率。
The class III phosphatidylinositol 3-kinase (PI3KC3) is crucial for autophagosome biogenesis. It has been long speculated to nucleate the autophagosome membrane, but the biochemical mechanism of such nucleation activity remains unsolved. We recently identified Barkor/Atg14(L) as the targeting factor for PI3KC3 to autophagosome membrane. Here, we show that we have characterized the region of Barkor/Atg14(L) required for autophagosome targeting and identified the BATS [Barkor/Atg14(L) autophagosome targeting sequence] domain at the carboxyl terminus of Barkor. Bioinformatics and mutagenesis analyses revealed that the BATS domain binds to autophagosome membrane via the hydrophobic surface of an intrinsic amphipathic alpha helix. BATS puncta overlap with Atg16 and LC3, and partially with DFCP1, in a stress-inducible manner. Ectopically expressed BATS accumulates on highly curved tubules that likely represent intermediate autophagic structures. PI3KC3 recruitment and autophagy stimulation by Barkor/Atg14(L) require the BATS domain. Furthermore, our biochemical analyses indicate that the BATS domain directly binds to the membrane, and it favors membrane composed of phosphatidylinositol 3-phosphate [PtdIns(3) P] and phosphatidylinositol 4,5-biphosphate [PtdIns(4,5)P2]. By binding preferentially to curved membranes incorporated with PtdIns(3) P but not PtdIns(4,5) P2, the BATS domain is capable of sensing membrane curvature. Thus, we propose a novel model of PI3KC3 autophagosome membrane nucleation in which its autophagosome-specific adaptor, Barkor, accumulates on highly curved PtdIns(3) P enriched autophagic membrane via its BATS domain to sense and maintain membrane curvature.