Details of morpholino used.

Mitochondria regulate several physiological functions through mitochondrial Ca2+ dynamics. However, role of mitochondrial Ca2+ signaling in melanosome biology remains unknown. Here, we show that pigmentation requires mitochondrial Ca2+ uptake. In vitro gain and loss of function studies demonstrate that mitochondrial Ca2+ uniporter (MCU) is crucial for melanogenesis while MCU rheostat, MCUb negatively control melanogenesis. Zebrafish, MCU+/- and MCUb-/- mice models show that MCU complex drives pigmentation in vivo. Mechanistically, MCU silencing activates transcription factor NFAT2 to induce expression of keratin (5, 7, and 8) filaments. Interestingly, keratin5 in turn augments mitochondrial Ca2+ uptake and potentiates melanogenesis by regulating melanosome biogenesis and maturation. Hence this signaling module acts as a negative feedback loop that fine-tunes both mitochondrial Ca2+ signaling and pigmentation. Notably, mitoxantrone, an FDA approved drug that inhibits MCU, reduces pigmentation thereby highlighting therapeutic potential of targeting mitochondrial Ca2+ uptake for clinical management of pigmentary disorders. Taken together, we reveal an MCU-NFAT2-Keratin5 driven signaling axis that acts as a critical determinant of mitochondrial Ca2+ uptake and pigmentation. Given the vital role of mitochondrial Ca2+ signaling and keratin filaments in cellular physiology, this feedback loop could be operational in a variety of other patho-physiological processes.

线粒体通过线粒体钙动态调控多种生理功能。然而，线粒体钙信号在黑素体生物学中的作用仍未明确。本研究证实，色素沉着过程依赖于线粒体钙摄取。体外功能获得与功能缺失实验表明，线粒体钙单向转运体（mitochondrial Ca2+ uniporter, MCU）在黑素生成中发挥关键作用，而其调控亚基MCUb则负向调控黑素生成。通过斑马鱼、MCU+/-及MCUb-/-小鼠模型，我们证实MCU复合物在体内可驱动色素沉着。机制层面，MCU沉默可激活转录因子活化T细胞核因子2（nuclear factor of activated T cells 2, NFAT2），进而诱导角蛋白（5、7、8型）丝的表达。有趣的是，角蛋白5反过来可通过调控黑素体的生物发生与成熟，增强线粒体钙摄取并促进黑素生成。因此，该信号模块构成负反馈环路，可精准调控线粒体钙信号与色素沉着过程。值得注意的是，美国食品药品监督管理局（Food and Drug Administration, FDA）批准的MCU抑制剂米托蒽醌可降低色素沉着水平，这一发现凸显了靶向线粒体钙摄取用于临床治疗色素性疾病的潜力。综上，本研究揭示了一条由MCU-NFAT2-角蛋白5构成的信号轴，其作为线粒体钙摄取与色素沉着的关键调控因子。鉴于线粒体钙信号与角蛋白丝在细胞生理中的重要作用，该负反馈环路可能在多种其他病理生理过程中发挥功能。