Phosphatidylinositol-4,5-Biphosphate (PI(4,5)P(2)) Is Required for Rapid Endocytosis in Chromaffin Cells

OBJECTIVE: Phosphoinositides play a regulatory role in clathrin-mediated endocytosis. However, their involvement in clathrin-independent endocytosis termed rapid endocytosis (RE), which is the mode of vesicle recycling during neurotransmitter release by transient fusion (known as kiss-and-run), has not been investigated. Here, we used patch-clamp recording of whole-cell membrane capacitance in adrenal chromaffin cells (ACC) to monitor changes of RE kinetics in response to pharmacological alteration of phosphatidylinositol-4,5-biphosphate (PI(4,5)P(2)) level by phenylarsine oxide (PAO) or antibody against phosphatidylinositol 4-kinase (Ab(PI4K)). RESULTS: We found that PAO and Ab(PI4K) significantly abrogated RE kinetics. Infusion of PI(4,5)P(2) through the patch pipette potentiated RE kinetics and reversed PAO- and Ab(PI4K)-induced blockade of RE. Similarly, the application of the bifunctional thiol dithiothreitol (DTT) to PAO-treated cells completely prevented the inhibitory effect of PAO on RE. These findings indicate that PI(4,5)P(2) is implicated in the signaling (mechanistic) process of RE in ACC.