FIGURE 8.

KCl depolarization induces alkalinization of SgII-GFP-containing granules in PC12 and A35C cells. Kinetics of fluorescence changes following KCl depolarization in PC12 cells (A) or A35C cells (B) expressing SgII-GFP alone or together with botulinum neurotoxin C1 light chain (+L-BoNT/C1). Cells were preincubated for 10 min in either a calcium-containing buffer (+CaB), a calcium-depleted buffer (−CaB), or a calcium-depleted buffer containing 50 mm of BAPTA/AM (−CaB + BAPTA/AM). Whole cell fluorescence was continuously monitored (500-ms acquisition frames) over a 20-min period. Superfusion of 50 mm KCl (+KCl) or H₂O (vehicle) was performed at the indicated time (black arrow). Changes in fluorescence are expressed as a percentage of the fluorescence present in the cell before superfusion. Measurements were done in triplicate for each cell type, in at least three independent experiments. Shown are the kinetics of one typical transfected cell.