Transport of cholesterol from the endoplasmic reticulum to the plasma membrane.

TLDR

The study investigates the transport of newly synthesized cholesterol from the ER to the plasma membrane in CHO cells using a cell fractionation assay. The authors employed a cell fractionation assay and inhibitor screening (cytochalasin B, colchicine, monensin, cycloheximide, NH₄Cl) to probe cholesterol transport mechanisms. Cholesterol transport from the ER to the plasma membrane is energy‑dependent, temperature‑sensitive, and appears to occur via a vesicular system, as it stops at 15 °C, accumulates in the ER and vesicles when synthesis continues, and is unaffected by cytoskeletal or metabolic inhibitors.

Abstract

We have studied the transport of newly synthesized cholesterol from the endoplasmic reticulum to the plasma membrane in Chinese hamster ovary cells using a cell fractionation assay. We found that transport is dependent on metabolic energy, but that the maintenance of the high differential concentration of cholesterol in the plasma membrane is not an energy-requiring process. We have tested a variety of inhibitors for their effect on cholesterol transport and found that cytochalasin B, colchicine, monensin, cycloheximide, and NH4Cl did not have any effect. The cholesterol transport process shows a sharp temperature dependence; it ceases at 15 degrees C, whereas cholesterol synthesis continues. When synthesis occurs at 15 degrees C, the newly synthesized cholesterol accumulates in the endoplasmic reticulum and in a low density, lipid-rich vesicle fraction. These results suggest that cholesterol is transported via a vesicular system.