Exocytosis is a fundamental process in physiology, that ensures communication between cells, organs and even organisms. Hormones, neuropeptides and antibodies, among other cargoes are packed in exocytic vesicles that need to reach and fuse with the plasma membrane to release their content to the extracellular milieu. Hundreds of proteins participate in this process and several others in its regulation. We report here a novel component of the exocytic machinery, the Drosophila transmembrane immunophilin Zonda (Zda), previously found to participate in autophagy. Zda is highly expressed in secretory tissues, and regulates exocytosis in at least three of them: the ring gland, insulin‐producing cells and the salivary gland. Using the salivary gland as a model system, we found that Zda is required at final steps of the exocytic process for fusion of secretory granules to the plasma membrane. In a genetic screen we identified the small GTPase RalA as a crucial regulator of secretory granule exocytosis that is required, similarly to Zda, for fusion between the secretory granule and the plasma membrane.

中文翻译：

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亲免蛋白Zonda控制内分泌和外分泌组织中调节的胞吐作用

胞吐作用是生理学的基本过程，可确保细胞，器官甚至生物体之间的通讯。激素，神经肽和抗体以及其他货物包装在胞外小泡中，胞外小泡需要到达并与质膜融合以将其内容物释放到细胞外环境中。数百种蛋白质参与该过程，其他几种蛋白质参与其调控。我们在这里报告了胞外机制的一个新组成部分，果蝇跨膜免疫亲和蛋白Zonda（Zda），先前发现其参与自噬。Zda在分泌组织中高度表达，并在至少三个组织中调节胞吐作用：环形腺，产生胰岛素的细胞和唾液腺。使用唾液腺作为模型系统，我们发现在分泌过程的最后阶段需要Zda才能使分泌颗粒融合到质膜上。在遗传筛选中，我们确定了小的GTPase RalA是分泌颗粒胞吐作用的关键调节剂，与Zda类似，分泌颗粒与胞膜之间的融合也需要分泌颗粒胞吐作用。