Labeling Lysosomes and
Tracking Lysosome-Dependent
Apoptosis with a Cell-Permeable Activity-Based Probe
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Abstract
In this study, we describe a new strategy for labeling
and tracking
lysosomes with a cell-permeable fluorescent activity-based probe (CpFABP)
that is covalently bound to select lysosomal proteins. Colocalization
studies that utilized LysoTracker probes as standard lysosomal markers
demonstrated that our novel probe is effective in specifically labeling
lysosomes in various kinds of live cells. Furthermore, our studies
revealed that this probe has the ability to label fixed cells, permeabilized
cells, and NH<sub>4</sub>Cl-treated cells, unlike LysoTracker probes,
which show ineffective labeling under the same conditions. Remarkably,
when applied to monitor the process of lysosome-dependent apoptosis,
our probe not only displayed the expected release of lysosomal cathepsins
from lysosomes into the cytosol but also revealed additional information
about the location of the cathepsins during apoptosis, which is undetectable
by other chemical lysosome markers. These results suggest a wide array
of promising applications for our probe and provide useful guidelines
for its use as a lysosome marker in lysosome-related studies