The SNARE protein vti1a functions in dense‐core vesicle biogenesis
The SNARE protein vti1a functions in dense‐core vesicle biogenesis
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DOI：
10.15252/embj.201387549
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发表时间：
2014-08
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通讯作者：
Alexander M. Walter;J. Kurps;H. Wit;Susanne Schöning;T. Toft-Bertelsen;J. Lauks;Iwona Ziomkiewicz;A. N. Weiss;A. Schulz;G. Fischer von Mollard;M. Verhage;J. B. Sørensen
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作者：
Alexander M. Walter;J. Kurps;H. Wit;Susanne Schöning;T. Toft-Bertelsen;J. Lauks;Iwona Ziomkiewicz;A. N. Weiss;A. Schulz;G. Fischer von Mollard;M. Verhage;J. B. Sørensen
SNARE蛋白vti 1a被认为驱动细胞内细胞器的融合，但最近的数据也表明vti 1a参与胞吐作用。在这里，我们发现vti 1a在肾上腺嗜铬细胞的成熟分泌囊泡中不存在，但定位于trans-Golgi网络附近的一个区室，与syntaxin-6部分重叠。在vti 1a null细胞中，胞吐作用受损，部分原因是质膜上的Ca 2+通道较少，部分原因是尺寸减小的囊泡较少和小突触泡蛋白-2含量减少。相反，释放动力学和Ca 2+敏感性保持不变，表明导致递质释放的最终融合反应未受干扰。额外删除最密切相关的SNARE，vti 1b，不加剧vti 1a表型，和vti 1b空细胞显示没有分泌缺陷，表明vti 1b不参与胞吐。vti 1a的长期再表达（天）是恢复分泌能力所必需的，而强的短期表达（小时）是无效的，这与vti 1a参与与囊泡生成相关的上游步骤而不是融合一致。我们的结论是vti 1a功能的囊泡生成和Ca 2+通道的运输，但不适合递质释放。
The SNARE protein vti1a is proposed to drive fusion of intracellular organelles, but recent data also implicated vti1a in exocytosis. Here we show that vti1a is absent from mature secretory vesicles in adrenal chromaffin cells, but localizes to a compartment near the trans‐Golgi network, partially overlapping with syntaxin‐6. Exocytosis is impaired in vti1a null cells, partly due to fewer Ca2+‐channels at the plasma membrane, partly due to fewer vesicles of reduced size and synaptobrevin‐2 content. In contrast, release kinetics and Ca2+‐sensitivity remain unchanged, indicating that the final fusion reaction leading to transmitter release is unperturbed. Additional deletion of the closest related SNARE, vti1b, does not exacerbate the vti1a phenotype, and vti1b null cells show no secretion defects, indicating that vti1b does not participate in exocytosis. Long‐term re‐expression of vti1a (days) was necessary for restoration of secretory capacity, whereas strong short‐term expression (hours) was ineffective, consistent with vti1a involvement in an upstream step related to vesicle generation, rather than in fusion. We conclude that vti1a functions in vesicle generation and Ca2+‐channel trafficking, but is dispensable for transmitter release.