Fig. 3.

PIP4K IIβ decreases PI-3,4,5-P₃, but not PI-3,4-P₂ levels. (A) CHO-IR cells were transfected with p110caax and with PIP4K IIβ, Ship2, or empty vector (V) as indicated. Cells were serum-starved and labeled with [³H]inositol for 24 h. The deacylated lipids were analyzed by HPLC, quantified, and normalized as described. The graphs represent the relative levels of PI-3,4,5-P₃ (black) or PI-3,4-P₂ (gray) when compared with the PI-3,4,5-P₃ levels in cells transfected with empty vector. (B and C) The ratio of PI-3,4,5-P₃ and PI-3,4-P₂ in cells expressing p110caax (B) or cells stimulated with insulin (C). The gray bars represent the percentage of PI-3,4-P₂, and the black bars represent the percentage of PI-3,4,5-P₃ over the sum of PI-3,4-P₂ and PI-3,4,5-P₃. The error bars represent the range from two experiments.