4-Dimensional observation ER-mitochondria interaction in living cells under nanoscopy by a stable pyridium salt as biosensor

Abstract

Intracellular membrane-bounded organelles are physically associated and play critical roles in many physiological processes. However, real-time monitoring of their interaction at the nanoscale in three-dimension (xyz-t or 4D imaging) remains considerable difficulties due to limitations of the current super-resolution probe toolbox. Here, we developed a novel cell-permeable pyridium salt derivative (TpsPym) with red-emission and large Stock-shift. Interestingly, TpsPym demonstrated a high specificity to mitochondria and endoplasmic reticulum (ER) with different fluorescent intensity. This offered the possibility to utilize this probe to label dual-organelles (ER-mitochondria) under stimulated emission depletion nanoscopy (STED). We successfully monitored the dynamic interactions in real-time between mitochondria and ER in three dimension during starvation-induced autophagy. It suggested ER-mitochondria contacting area might play an essential factor during autophagic cell death (ACD). Our study not only expanding the nanoscopic probe kit but also provide new understanding for ER-mitochondrial interaction at the nanoscale during correlated physiological conditions.