Figure 2.

PI(4)P and PI(4,5)P₂ are required for refilling of RRP. (A) Individual β cells were stimulated by using a train of fourteen 500-ms depolarizations (V_m, Upper). The associated increases in cell capacitance (C_m, Lower) were measured under control conditions and after inclusion of 1 μM PI(4)P in the pipette solution dialyzing the cell interior. (B) Histogram summarizing the magnitude of the exocytotic responses elicited by trains of depolarizations (C_m, train) under control conditions and in the presence of 1 μM PI(4)P and 1 μM PI(4,5)P₂. (C) Exocytosis (C_m) elicited by two trains of depolarizations 2 min (Left) and 5 min (Right) after establishment of standard whole-cell configuration under control conditions (control) and in a different cell after infusion of an antibody directed against PI(4)P [25 μg/ml, anti-PI(4)P]. (D) Histogram summarizing exocytosis elicited by 1st (2 min, open bars) and 2nd train of depolarizations (5 min after reaching whole-cell configuration, filled bars) under control conditions, in the presence of 25 μg/ml anti-PI(4)P, 25 μg/ml of an antibody directed against PI(4,5)P₂ [anti-PI(4,5)P₂] or 25 μg/ml of an antibody against phosphatidylserine (anti-PS). In B and D, data are quoted as mean values ± SEM of five experiments in each group. *, P < 0.01.