Caspase-Activated Cell-Penetrating Peptides Reveal
Temporal Coupling Between Endosomal Release and Apoptosis in an RGC‑5
Cell Model
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Abstract
Caspase-activatable cell-penetrating peptide (CPP) probes, designed
for efficient cell uptake and specificity via cleavable intramolecular
quenched-fluorophore strategies, show promise for identifying and
imaging retinal ganglion cell apoptosis <i>in vivo.</i> However,
initial cell uptake and trafficking events cannot be visualized because
the probes are designed to be optically quenched in the intact state.
To visualize subcellular activation events in real-time during apoptosis,
a new series of matched quenched and nonquenched CPP probes were synthesized.
In both native and staurosporine-differentiated RGC-5 cells, probe
uptake was time- and concentration-dependent through clathrine-, caveolin-,
and pinocytosis-mediated endocytic mechanisms. During apoptosis, KcapTR488,
a novel dual fluorophore CPP probe, revealed by multispectral imaging
a temporal coupling of endosomal release and effector caspase activation
in RGC-5 cells. The novel CPPs described herein provide new tools
to study spatial and temporal regulation of endosomal permeability
during apoptosis