Fig. 2.

Phosphorylation of PI by class I PI3 kinase is important, and PI(3)P and PI(4,5)P₂ work together to stimulate actin polymerization. (A) Pyrene actin assay on addition of PC/PI/PI(4,5)P₂ into extracts preincubated with 10 μM wortmannin, BEZ-235, or YM201636. (B) Pyrene actin assay on addition of 48% PC, 47% PI, 1% PI(3)P, and 4% PI(4,5)P₂ liposomes in extracts that were preincubated with the drugs similarly to A showing that the 3-position stimulates actin polymerization. (C) Pyrene actin assay on addition of 48% PC, 47% PS, 1% PI(3)P or 1% PI(3,5)P₂, and 4% PI(4,5)P₂ in extract preincubated with a 1/100 dilution of a phosphatase inhibitor mixture. (D) Addition of liposomes where PI(3)P and PI(4,5)P₂ are present in the same or distinct liposomes. Data is representative of two or three independent experiments.