300 nM LysoTracker red or green (Life Technologies) in Dulbecco’s
modified phosphate buffered saline (DPBS) for 15-minutes at room temperature,
washed tree times with DPBS, and imaged using a Zeiss Axio Observer inverted
microscope with Colibri LED light source and Zeiss Mrm CCD camera with
Axiovision 4.8 software. Lysosomal area per cell was measured from LysoTracker
fluorescence images in
using the analyse particles function. LysoTracker fluorescence was measured in
cells grown in Corning CellBIND 96-well plates (0.8x10^5 cells/well) using a
SpectraMax® Gemini microplate reader (Molecular Devices).
Ca2+ measurements were done as described12 (link) but with minor modifications for neurons, which
were loaded with 1 µM Fura-2, AM (Stratech) without Pluronic F-127. Cells
were imaged in Hank’s balanced salt solution (HBSS; 1 mM HEPES pH7.4, 10
µM CaCl2 and 1 mM MgCl2) using a Zeiss Axiovert 35
microscope with Cairn Optospin filter exchanger, Orca Flash 4.0 sCMOS camera and
MetaFluor 7.10 software. For all experiments, ionomycin (Merck, 2 μM) was
added to clamp intracellular Ca2+ stores followed by 500 µM
Gly-Phe-β-naphthylamide (GPN, Abcam) to release lysosomal Ca2+12 (link).