Semi-Synthetic LC3-Interacting Degrader for Visualizing Macroautophagic Activity and Targeted Degradation.

Macroautophagy is central to cellular homeostasis and emerges as a promising avenue for targeted degradation. However, there is still a lack of efficient approaches allowing for visualizing macroautophagic flux and degradation. Here we develop a semi-synthetic LC3-interacting degrader (SLID) that enables fluorogenic imaging of macroautophagic activities and visualization of targeted degradation. SLID is engineered by fusing LC3-interacting regions (LIRs) to a self-labeling tag and an oligomeric motif, with the LIRs for binding to autophagosomes, the oligomeric motif for enhancing the binding, and the self-labeling tag for visualizing autophagosome formation using a pH indicator. SLID is further coupled to an antibody domain through a dimerization-induced proximity system, allowing chemically inducible degradation of target proteins. We show that this SLID platform permits efficient degradation of diverse target proteins such as disease-associated aggregation-prone proteins and phase-separated condensates. SLID also reveals elevated macroautophagic activities in senescent cells, and is repurposed for inducing senescent cell apoptosis via degradation of pro-survival and anti-apoptotic proteins. Our study highlights the great promise of SLID as a versatile tool for studying macroautophagy and targeted protein degradation.