Cell-substratum and cell-monolayer adhesion are dependent upon cellular cholesterol biosynthesis

Abstract

Incubation of Chinese hamster lung (Dede) cells in medium containing 25-hydroxycholesterol resulted in the suppression of cellular cholesterol biosynthesis and a decrease in the cellular concentration of cholesterol so that the cholesterol/phospholipid molar ratio was reduced to approx. 50% of the control value. When these ‘sterol-depleted’ cells were allowed to attach to a serum-coated glass substratum, an inhibition of the rate and extent of attachment relative to the controls was observed. After 1 h incubation, only 10–25% of the 25-hydroxycholesterol-treated cells were attached, compared with virtually 100% of the control cells. Similar results were obtained with Chinese hamster ovary cells and with mouse L cells. Inhibition of adhesion was dependent upon the dose of—and time of exposure to—the oxygenated sterol. This inhibition was prevented when either cholesterol or mevalonic acid (the product of the enzymatic reaction inhibited by 25-hydroxycholesterol) was added with the 25-hydroxycholesterol, indicating that the effect of the sterol was primarily due to suppression of cholesterol synthesis. In addition, the inhibitor had no effect on the growth of a 25-hydroxycholesterol-resistant mutant or on the rate or extent of its adhesion to the substratum. Other oxygenated sterols (e.g. 22-ketocholesterol, 7β-hydroxycholesterol, 20α-hydryxycholesterol and 5α-cholest-8(14)-en-3β-ol-15-one) effected qualitatively similar inhibitions of the rates of sterol synthesis and cell-substratum attachment. The decreased adhesion observed when cultures were treated with inhibitors of cholesterol synthesis was not alleviated at low temperatures, suggesting that the effects of the inhibitor could not be overcome by a temperature-dependent increase in membrane viscosity. The rate and extent of adhesion of either Chinese hamster lung cells or L cell to several cell monolayers was also reduced in response to sterol depletion. These results suggest that membrane lipids, particularly cholesterol, play a significant role in cell-substratum and cell-cell adhesion.