Tyrosine phosphorylation of secretion machinery proteins is a crucial regulatory mechanism for exocytosis. However, the participation of protein tyrosine phosphatases (PTPs) in different exocytosis stages has not been defined. Here we demonstrated that PTP-MEG2 controls multiple steps of catecholamine secretion. Biochemical and crystallographic analyses revealed key residues that the interactions between govern the PTP-MEG2 and NSF-pY⁸³ site, specify PTP-MEG2 substrate selectivity and modulate the fusion of catecholamine-containing vesicles. Unexpectedly, delineation of PTP-MEG2 mutants along with the NSF binding interface revealed that PTP-MEG2 controls the fusion pore opening through non-NSF dependent mechanisms. Utilizing bioinformatics search and biochemical and electrochemical screening approaches, we discovered that PTP-MEG2 regulates the opening and extension of the fusion pore by dephosphorylating the DYNAMIN2-pY¹²⁵ and MUNC18-1-pY¹⁴⁵ site. Further structural and biochemical analysis confirmed the interaction of PTP-MEG2 with MUNC18-1-pY¹⁴⁵ or DYNAMIN2-pY¹²⁵ through a distinct structural basis compared with that of the NSF-pY⁸³ site. Our studies extended mechanistic insights in complex exocytosis processes.

中文翻译：

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PTP-MEG2通过两个不同的结构基础和底物调节定量大小和融合孔的开放

分泌机器蛋白的酪氨酸磷酸化是胞吐作用的关键调节机制。但是，尚未定义蛋白质酪氨酸磷酸酶（PTP）在不同胞吐阶段的参与。在这里，我们证明了PTP-MEG2控制儿茶酚胺分泌的多个步骤。生化和晶体学分析揭示了关键残基，它们之间的相互作用决定了PTP-MEG2和NSF-pY ⁸³位点，指定PTP-MEG2底物选择性，并调节含儿茶酚胺的囊泡的融合。出乎意料的是，对PTP-MEG2突变体与NSF结合界面的描述揭示了PTP-MEG2通过非NSF依赖性机制控制融合孔的开放。利用生物信息学搜索以及生物化学和电化学筛选方法，我们发现PTP-MEG2通过使DYNAMIN2-pY ¹²⁵和MUNC18-1-pY ¹⁴⁵位去磷酸化来调节融合孔的开放和延伸。进一步的结构和生化分析证实，与NSF-pY ⁸³相比，PTP-MEG2与MUNC18-1-pY ¹⁴⁵或DYNAMIN2-pY ¹²⁵的相互作用具有独特的结构基础现场。我们的研究在复杂的胞吐过程中扩展了机制的见解。