Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan.
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan.
Nat Commun. 2023 May 9;14(1):2683. doi: 10.1038/s41467-023-38397-6.
Many secretory enzymes acquire essential zinc ions (Zn) in the Golgi complex. ERp44, a chaperone operating in the early secretory pathway, also binds Zn to regulate its client binding and release for the control of protein traffic and homeostasis. Notably, three membrane transporter complexes, ZnT4, ZnT5/ZnT6 and ZnT7, import Zn into the Golgi lumen in exchange with protons. To identify their specific roles, we here perform quantitative Zn imaging using super-resolution microscopy and Zn-probes targeted in specific Golgi subregions. Systematic ZnT-knockdowns reveal that ZnT4, ZnT5/ZnT6 and ZnT7 regulate labile Zn concentration at the distal, medial, and proximal Golgi, respectively, consistent with their localization. Time-course imaging of cells undergoing synchronized secretory protein traffic and functional assays demonstrates that ZnT-mediated Zn fluxes tune the localization, trafficking, and client-retrieval activity of ERp44. Altogether, this study provides deep mechanistic insights into how ZnTs control Zn homeostasis and ERp44-mediated proteostasis along the early secretory pathway.
许多分泌酶在高尔基体复合物中获得必需的锌离子（Zn）。ERp44 是一种在早期分泌途径中起作用的伴侣蛋白，也结合 Zn 来调节其客户的结合和释放，以控制蛋白质运输和动态平衡。值得注意的是，三种膜转运体复合物 ZnT4、ZnT5/ZnT6 和 ZnT7 将 Zn 导入高尔基体腔中，以质子交换的方式进行。为了确定它们的特定作用，我们在这里使用超分辨率显微镜和靶向特定高尔基体亚区的 Zn 探针进行定量 Zn 成像。系统的 ZnT 敲低揭示了 ZnT4、ZnT5/ZnT6 和 ZnT7 分别调节远端、中部和近端高尔基体的不稳定 Zn 浓度，与它们的定位一致。对经历同步分泌蛋白运输的细胞进行时程成像和功能测定表明，ZnT 介导的 Zn 通量调节 ERp44 的定位、运输和客户检索活性。总的来说，这项研究提供了深入的机制见解，说明了 ZnT 如何控制早期分泌途径中的 Zn 动态平衡和 ERp44 介导的蛋白质稳态。
