Figure 6.

Effect of palmitoylation on NCX1 inactivation by masking anionic phospholipid head groups. Stably transfected FT-293 cells expressing WT and C739A NCX1 were voltage clamped in the whole-cell mode using ATP-free, highly Ca-buffered cytoplasmic solutions (10 mM EGTA with 1 mM Ca). A) Using a cytoplasmic solution containing 20 µM heptalysine (K7) to bind head groups of anionic phospholipids, outward exchange currents were activated by stepping extracellular Ca from 0 to 4 mM in cells expressing WT (left) and C739A exchangers (right). Current magnitudes are given for peak currents and current remaining after 10 s. Residual currents are highly significantly increased in cells expressing C739A compared with WT exchangers. B) Using a cytoplasmic solution containing 0.15 mM Al³⁺ (in the presence of 10 mM EGTA) to bind PIP₂ head groups, outward exchange currents were strongly suppressed in cells expressing WT exchangers (left) but remained robust in cells expressing C739A exchangers (right). **P < 0.01.