The zinc ion (Zn2+) is emerging as an important signaling molecule. Here, we engineered an improved Zn2+ probe GZnP2 based on a previously developed fluorescent sensor GZnP1 to provide a higher fluorescent readout (2-fold higher) that is proportional to cellular labile Zn2+ concentrations. We further developed a set of GZnP2 derived imaging tools to determine the labile Zn2+ concentrations in the mitochondrial matrix, mitochondrial intermembrane space (IMS), and cytosol in four different cell lines (HeLa, Cos-7, HEK293, and INS-1). The labile Zn2+ concentration in the matrix was less than 1 pM, while the labile Zn2+ concentration in the IMS was comparable to the cytosol (∼100 pM). With these sensors, we showed that upon exposure to high Zn2+, only the cytosol and the IMS were overloaded with Zn2+, while the mitochondrial matrix was unable to sequester excess labile Zn2+ in depolarized INS-1 cells. This work highlighted the importance of distinguishing the labile Zn2+ concentrations and dynamics between the mitochondrial matrix and IMS.

中文翻译：

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用GZnP2传感器光学记录线粒体基质和膜间空间中Zn2 +的动力学。

锌离子（Zn2 +）正在作为一种重要的信号分子出现。在这里，我们基于先前开发的荧光传感器GZnP1设计了一种改进的Zn2 +探针GZnP2，以提供与细胞不稳定的Zn2 +浓度成比例的更高的荧光读数（高2倍）。我们进一步开发了一组GZnP2衍生的成像工具，以确定四种不同细胞系（HeLa，Cos-7，HEK293和INS-1）中线粒体基质，线粒体膜间空间（IMS）和胞质溶胶中不稳定的Zn2 +浓度。基质中不稳定的Zn2 +浓度小于1 pM，而IMS中不稳定的Zn2 +浓度可与胞质溶胶（〜100 pM）相提并论。使用这些传感器，我们发现在暴露于高Zn2 +的情况下，只有胞质溶胶和IMS才会超载Zn2 +，而线粒体基质无法隔离去极化的INS-1细胞中过量的不稳定Zn2 +。这项工作强调了区分线粒体基质和IMS之间不稳定的Zn2 +浓度和动力学的重要性。