VAMP7 Regulates Autophagosome Formation by Supporting Atg9a Functions in Pancreatic β-Cells From Male Mice
VAMP7 Regulates Autophagosome Formation by Supporting Atg9a Functions in Pancreatic β-Cells From Male Mice
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DOI：
10.1210/en.2018-00447
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发表时间：
2018-11-01
期刊：
影响因子：
4.8
通讯作者：
Ohara-Imaizumi, Mica
中科院分区：
文献类型：
--
作者：
Aoyagi, Kyota;Itakura, Makoto;Ohara-Imaizumi, Mica
在糖尿病患者的β细胞中观察到功能障碍的线粒体，其最终通过自噬被去除。囊泡相关膜蛋白（VAMP）7是一种囊泡陷阱蛋白，调节自噬体形成以维持线粒体稳态并控制胰腺β细胞中的胰岛素分泌。然而，其分子机制在很大程度上是未知的。在这项研究中，我们使用VAMP 7缺陷的β细胞和β细胞衍生的Min 6细胞研究了VAMP 7依赖性自噬体形成的分子机制。VAMP 7定位于再循环内体（RE）的自噬相关（Atg）9a驻留囊泡中，其有助于自噬体形成，并且其与Hrb、Syntaxin 16和SNAP-47相互作用。Hrb从质膜募集VAMP 7和Atg 9a至REs.Syntaxin16和SNAP-47介导的自噬体形成晚于VAMP 7至Atg 9a驻留囊泡的适当定位。Hrb、Syntaxin 16和SNAP-47的敲低导致有缺陷的自噬体形成、功能障碍的线粒体的积累和葡萄糖刺激的胰岛素分泌的损害。我们的数据表明，VAM P7和Atg 9a最初被招募到RE，以Hrb依赖的方式组织VAMP 7和Atg 9a驻留囊泡。此外，VAMP 7与Syntaxin 16和SNAP-47形成SNARE复合物，这可能导致Atg 9a驻留囊泡在自噬体形成期间融合。因此，VAMP 7通过支持有助于维持线粒体质量的Atg 9a功能参与自噬体形成。
Dysfunctional mitochondria are observed in beta-cells of diabetic patients, which are eventually removed by autophagy. Vesicle-associated membrane protein (VAMP)7, a vesicular SNARE protein, regulates autophagosome formation to maintain mitochondrial homeostasis and control insulin secretion in pancreatic beta-cells. However, its molecular mechanism is largely unknown. In this study, we investigated the molecular mechanism of VAMP7-dependent autophagosome formation using VAMP7-deficient beta-cells and beta-cell derived Min6 cells. VAMP7 localized in autophagy-related (Atg) 9a resident vesicles of recycling endosomes (REs), which contributed to autophagosome formation, and it interacted with Hrb, Syntaxinl6, and SNAP-47. Hrb recruited VAMP7 and Atg9a from the plasma membrane to REs. Syntaxin16 and SNAP-47 mediated autophagosome formation at a step later than the proper localization of VAMP7 to Atg9a-resident vesicles. Knockdown of Hrb, Syntaxin16, and SNAP-47 resulted in defective autophagosome formation, accumulation of dysfunctional mitochondria, and impairment of glucose-stimulated insulin secretion. Our data indicate that VAM P7 and Atg9a are initially recruited to REs to organize VAMP7 and Atg9a-resident vesicles in an Hrb-dependent manner. Additionally, VAMP7 forms a SNARE complex with Syntaxin16 and SNAP-47, which may cause fusions of Atg9a-resident vesicles during autophagosome formation. Thus, VAMP7 participates in autophagosome formation by supporting Atg9a functions that contribute to maintenance of mitochondrial quality.