Study On A Lysosomal Marker Targeting To Cysteine Cathepsins

Lysosomes are membrane-enclosed vesicles which involved in a variety of lifeactivities including intracelluar digestion, cell membrane recycling, and apoptosis.Lysosomal disfunctions could lead to diverse diseases, such as inflammmation, tumor, andsilicosis Visualization of the moleculars getting into or out of lysosomes is not onlyimportant for understanding the molecular mechansiams of life activities that lysosomesinvolved, but also of great significance to the treatment of diseases.In this study, we developed cell-permeable activity-based probes (CpFABPs) to labellysosomes in living cells. Through colocalization studies with lysosomal makers, wedemonstrated that the CpFABPs could be used as a lysosomal maker in different cells. Viadirect labeling and indirect competition experiments with E-64in vitro or with inhibitorJPM-OEt in vivo, it was proved that CpFABPs could track lysosomes due to theirspecificity to cathepsins, which accumulated in lysosomes. The results also revealed thatCpFABPs could label lysosomes even in fixed cells, permeabilized cells, NH4Cl-treatedcells. Moreover, CpFABPs could directly detect the location changes of cathepsins,including the releasing of cathepsins from lysosomes in apoptotic cells.Therefore, the ABPs based on the activity of cathepsins could be a valuable tool tolabel lysosomes and track cathepsins in lysosome-related studies.