Super-resolution tracking of mitochondrial dynamics with a third-row transition metal complex dye

Combining luminescent transition metal complex (LTMC) dye with super-resolution microscopy is an excellent strategy for the long-term visualization of the dynamics of subcellular structures in living cells. However, it remains unclear whether the third-row LTMC dye is applicable for a particular type of super-resolution technique, structured illumination microscopy (SIM), to image subcellular structures. As described herein, we developed a synthetic 970-Da third-row LTMC, Iridium(III) complex dye, to track mitochondrial dynamics in living cells under SIM. The dye demonstrated excellent specificity and photostability and satisfactory cell permeability. While using SIM to image mitochondria, we achieved an approximately 80-nm resolution that allowed the clear observation of the structure of mitochondrial cristae. We used the dye to monitor mitochondrial dynamics relative to lysosomes, including fusion involved in mitophagy, and newly discovered mitochondria-lysosome contact (MLC) under different conditions. MLC remained intact and fusion vanished when five receptors, p62, NDP52, OPTN, NBR1, and TAX1BP1, were knocked out, suggesting that these two processes are independence.