Peroxisomal Ca ²⁺ dynamics. Peroxisomal Ca²⁺ dynamics explored using a targeted Cameleon. (A) Colocalization of transiently expressed D3cpv-SKL and the peroxisome marker catalase in HeLa cells. Bar, 10 µm. (B and C) Increases in [Ca²⁺]_c are followed by a slow rise in intraperoxisomal [Ca²⁺]. Fluorescence changes of GH3 cells transiently expressing D3cpv-KVK-SKL selectively within peroxisomes (two cells, dashed and dotted traces), mistargeted to the cytosol (continuous trace; B), or loaded with fura-2 (C). Where indicated, 30 mM KCl and 2 mM EGTA were added. (D) Cells permeabilized with digitonin. The experiment shows that no driving force supplied by ATP is needed for Ca²⁺ to enter peroxisomes (from Drago et al. [2008] with permission from The American Society for Biochemistry and Molecular Biology).