LAUSR

Phosphatidylinositol(4,5)-bisphosphate (PtdInsP2) is an important modulator of many cellular processes and its abundance in the plasma membrane is closely regulated. We examined the hypothesis that the scaffolding protein Dishevelled can bind the lipid kinases PI4K and PIP5K, facilitating synthesis of PtdInsP2 directly from PtdIns. This report used several assays for PtdInsP2 to examine the cooperative function of phosphoinositide kinases and Dishevelled in the context of two receptor signaling cascades. Simultaneous overexpression of PI4KIIIα and PIP5KIγ had a synergistic effect on PtdInsP2 synthesis that was recapitulated by overexpression of Dishevelled. Increasing the activity of Dishevelled by overexpression increased resting plasma membrane PtdInsP2. Knockdown of Dishevelled reduced resting plasma membrane PtdInsP2 and slowed PtdInsP2 resynthesis following receptor activation. We confirm that Dishevelled promotes coupling of PI4KIIIα and PIP5KIγ and show that this interaction is essential for efficient resynthesis of PtdInsP2 following receptor activation.