Overexpression of the Ca2+-binding protein CB-28K decreases MAO-A activity. HT-22 cells were transfected with the pREP plasmid (Vector) or the pREP-CB-28K expression vector (CB-28K). (A) The effect of CB-28K overexpression (24 h) on free intracellular Ca2+, [Ca2+]i, and on ROS production was examined. (note, the relative fluorescence intensity used for this set of ROS experiments was increased intentionally so as to avoid a "floor" effect, i.e. so that a decrease in ROS production could be demonstrated in CB-28K-overexpressing cells). (B) MAO-A and MAO-B activities were assessed radioenzymatically in corresponding cell lysates (*P < 0.05 versus control levels). (C) SDS-PAGE-resolved total cellular proteins were probed for CB-28K overexpression and for the expression of MAO-A and β-actin (used as a loading control). (D) Densitometry graph representing mao-A gene expression (relative to β-actin expression) determined by semi-quantitative RT-PCR, represented in (E). Data are presented as mean ± SD.