Figure 4.

In vitro regulation of Golgi/endosomal PI4K activity by cholesterol. (A) CHO cells were treated with or without 5 mM MβCD in DMEM for 30 min, washed twice in DMEM, and incubated in DMEM with 5% LPDS with or without MβCD-cholesterol (100 μM) complex (LPDS+Chol). After 2 h, cells were harvested, and fraction II was isolated and assayed for PI4K activity. PI4K activity is expressed relative to cells that were not treated with MβCD. Results are the mean and SEM of three experiments. (B and C) Golgi-enriched fraction II from CHO cells was treated with the indicated concentrations of MβCD (B) or MβCD-cholesterol complex (C) for 30 min at 37°C before assaying for PI4K activity. Results are expressed relative to buffer-treated controls and are the mean and SEM of three experiments.