A possible regulatory role of squalene epoxidase in chinese hamster ovary cells

Growth of Chinese Hamster Ovary (CHO) cells in the presence of 20% lipid depleted serum (LDS) for only 2 hr results in an increase in the synthesis of [ 14 C] sterols from [ 14 C] mevalonate and from [ 14 C] squalene compared with cells grown under normal growth conditions in the presence of 10% fetal calf serum (FCS). This enhanced sterol synthesis increases with time of exposure of the cells to LDS. However, exposing these cells for time periods up to 42.5 hr to a growth medium containing 20% LDS did not result in enhanced [ 14 C] sterol synthesis from [ 14 C] 2,3‐oxidosqualene. Incubation of these cells with [ 14 C] mevalonate resulted in the accumulation of [ 14 C] squalene regardless of the presence of either LDS or FCS. These results suggest that squalene epoxidase is a regulatory enzyme in the cholesterol biosynthetic pathway in CHO.