The STX6-VTI1B-VAMP3 complex facilitates xenophagy by regulating the fusion between recycling endosomes and autophagosomes
The STX6-VTI1B-VAMP3 complex facilitates xenophagy by regulating the fusion between recycling endosomes and autophagosomes
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DOI：
10.1080/15548627.2016.1241924
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发表时间：
2017-01-01
期刊：
影响因子：
13.3
通讯作者：
Nakagawa, Ichiro
中科院分区：
文献类型：
--
作者：
Nozawa, Takashi;Minowa-Nozawa, Atsuko;Nakagawa, Ichiro
巨自噬/自噬通过直接降解入侵的病原体（如A组链球菌（GAS））在免疫中起着关键作用，该过程被称为异源吞噬（xenophagy）。我们以前证明，针对GAS的自噬空泡，称为含GAS的自噬体样空泡（GcAVs），使用再循环内体（RE）作为膜源。然而，促进GcAVs和RE之间融合的精确分子机制仍不清楚。在这里，我们证明了STX 6（syntaxin 6）被募集到GcAVs，并与VTI 1B和VAMP 3形成复合物，以调节嗜异性所需的GcAV-RE融合。STX 6通过其基于酪氨酸的分选基序和跨膜结构域靶向GcAV膜，并通过其H2 SNARE结构域定位于GcAV上的TFRC（转铁蛋白受体）阳性点状结构。敲除和敲除实验表明，STX 6是GcAVs和RE之间融合所必需的，以促进细胞内GAS通过自噬的清除。此外，VAMP 3和VTI 1B与STX 6相互作用并定位于GcAV上的TFRC阳性斑点上，并且还参与RE-GcAV融合。此外，RABGEF 1的敲除损害RE-GcAV融合和STX 6-VAMP 3相互作用。这些发现表明，RABGEF 1通过STX 6-VAMP 3-VTI 1B复合物介导RE与GcAV融合，并揭示了响应细菌感染的自噬体形成中涉及的SNARE动力学。
Macroautophagy/autophagy plays a critical role in immunity by directly degrading invading pathogens such as Group A Streptococcus (GAS), through a process that has been named xenophagy. We previously demonstrated that autophagic vacuoles directed against GAS, termed GAS-containing autophagosome-like vacuoles (GcAVs), use recycling endosomes (REs) as a membrane source. However, the precise molecular mechanism that facilitates the fusion between GcAVs and REs remains unclear. Here, we demonstrate that STX6 (syntaxin 6) is recruited to GcAVs and forms a complex with VTI1B and VAMP3 to regulate the GcAV-RE fusion that is required for xenophagy. STX6 targets the GcAV membrane through its tyrosine-based sorting motif and transmembrane domain, and localizes to TFRC (transferrin receptor)-positive punctate structures on GcAVs through its H2 SNARE domain. Knockdown and knockout experiments revealed that STX6 is required for the fusion between GcAVs and REs to promote clearance of intracellular GAS by autophagy. Moreover, VAMP3 and VTI1B interact with STX6 and localize on the TFRC-positive puncta on GcAVs, and are also involved in the RE-GcAV fusion. Furthermore, knockout of RABGEF1 impairs the RE-GcAV fusion and STX6-VAMP3 interaction. These findings demonstrate that RABGEF1 mediates RE fusion with GcAVs through the STX6-VAMP3-VTI1B complex, and reveal the SNARE dynamics involved in autophagosome formation in response to bacterial infection.