The labile metal pool involved in intracellular trafficking and homeostasis is the portion susceptible to environmental stress. Herein, we visualized the different intracellular distributions of labile Cu(I) and Cu(II) pools in the alga Chlamydomonas reinhardtii. We first demonstrated that labile Cu(I) predominantly accumulated in the granules within the cytoplasmic matrix, whereas the labile Cu(II) pool primarily localized in the pyrenoid and chloroplast. The cell cycle played an integral role in balancing the labile Cu(I)/Cu(II) pools. Specifically, the labile Cu(II) pool primarily accumulated during the SM phase following cell division, while the labile Cu(I) pool dynamically changed during the G phase as cell size increased. Notably, the labile Cu(II) pool in algae at the SM stage exhibited heightened sensitivity to environmental Cu stress. Exogenous Cu stress disrupted the intracellular labile Cu(I)/Cu(II) cycle and balance, causing a shift toward the labile Cu(II) pool. Our proteomic analysis further identified a putative cupric reductase, potentially capable of reducing Cu(II) to Cu(I), and four putative multicopper oxidases, potentially capable of oxidizing Cu(I) to Cu(II), which may be involved in the conversion between the labile Cu(I) pool and labile Cu(II) pool. Our study elucidated a dynamic cycle of the intracellular labile Cu(I)/Cu(II) pools, which were accessible and responsive to environmental changes.

中文翻译：

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微藻莱茵衣藻细胞内不稳定 Cu(I)/Cu(II) 循环的动态调节：铜胁迫破坏平衡

参与细胞内运输和体内平衡的不稳定金属池是容易受到环境压力影响的部分。在此，我们可视化了藻类莱茵衣藻中不稳定 Cu(I) 和 Cu(II) 池的不同细胞内分布。我们首先证明不稳定的 Cu(I) 主要积聚在细胞质基质内的颗粒中，而不稳定的 Cu(II) 库主要集中在核糖核和叶绿体中。细胞周期在平衡不稳定的 Cu(I)/Cu(II) 库中发挥着不可或缺的作用。具体来说，不稳定的 Cu(II) 池主要在细胞分裂后的 SM 期积累，而不稳定的 Cu(I) 池在 G 期随着细胞大小的增加而动态变化。值得注意的是，SM 阶段藻类中不稳定的 Cu(II) 库表现出对环境铜胁迫的高度敏感性。外源铜应激破坏了细胞内不稳定的铜（I）/铜（II）循环和平衡，导致向不稳定的铜（II）库的转变。我们的蛋白质组分析进一步鉴定了一种假定的铜还原酶，可能能够将 Cu(II) 还原为 Cu(I)，以及四种假定的多铜氧化酶，可能能够将 Cu(I) 氧化为 Cu(II)，它们可能参与不稳定 Cu(I) 池和不稳定 Cu(II) 池之间的转换。我们的研究阐明了细胞内不稳定 Cu(I)/Cu(II) 库的动态循环，这些库易于访问并对环境变化做出响应。