Ratiometric probe with optimized permeability for visualizing lysosomal acidification during autophagy

Lysosomal pH plays indispensable roles in regulating the activity of lysosomal hydrolases, and is involved in crucial biological procedures including autophagy. Fluorescent probes for lysosomal pH were significant molecular tools to investigate lysosomal pH regulation. In this work, we have designed a new fluorophore to respond to pH in a ratiometric manner based on intramolecular charge transfer (ICT) mechanism. By modifying different alkyl chains on the dye, we have obtained a novel ratiometric probe for lysosomal pH with optimized membrane permeability. The probe could stain lysosomes, and was capable of monitoring lysosomal pH in a ratiometric manner. Chloroquine (CQ) induced pH rise in lysosomes was successfully visualized with the probe. The downregulation and subsequence up-regulation of lysosomal pH during starvation were also revealed in ratiometric manner. We firmly believe that the probe is a desirable tool to investigate lysosomal pH and promote the studies in autophagy and relative biological areas.

Automated summary

A new fluorescent probe has been developed for ratiometric monitoring of lysosomal pH, showing optimized membrane permeability and the ability to stain lysosomes. The probe successfully visualized the pH increase induced by chloroquine in lysosomes, as well as the downregulation and subsequent up-regulation of lysosomal pH during starvation in a ratiometric manner. It is believed to be a desirable tool for investigating lysosomal pH and promoting studies in autophagy and related biological areas.