Labeling Lysosomes in Live Cells with LysoTracker

INTRODUCTION The LysoTracker probes (Invitrogen/Molecular Probes) are used to label lysosomes in live cells, as described in this protocol. They are more selective for acidic organelles than the classically used neutral red or acridine orange dyes. They are freely membrane permeant at neutral pH and effectively label lysosomes at nanomolar concentrations, with ~50 nM being optimal for selectivity. It has been reported that in larger acidic compartments, the staining pattern is preserved even after fixation with aldehydes. LysoTracker dyes can be visualized at different wavelengths, so they are useful when multiple fluorescent dyes are used to label cells simultaneously.