An Aggregation-Induced Emission Optical Highlighter for the Studies of Endoplasmic Reticulum-Lipid Droplet Content Dynamics

The lipid droplet (LD) is a dynamic organelle responsible for lipid storage and metabolism that plays important roles in maintaining lipid homeostasis. However, limited strategies are available for tracking the LD content exchange. In this contribution, we report a novel fluorescent probe, TPE-AmAl, for real-time LD content dynamics tracking. TPE-AmAl is LD-specific, but emits faintly due to its intramolecular motion. Upon photoactivation, it undergoes a photocyclodehydrogenation reaction and shows a large fluorescence increment. Thus, it can be used for highlighting selected LDs with high spatial resolution. By measuring the fluorescence changes in the distal region, the lipid content exchange efficiency can be estimated. In our experiment, LD content exchange rate differences between nascent and mature LDs as well as cells with normal and deficient LD budding machinery are observed. This probe expands the fluorescence-based toolbox for LD content dynamics studies.