FIG. 1.

Effect of calphostin C on the endogenous LDL receptor gene induction in response to sterol depletion. HepG2 cells were either untreated or pretreated with indicated concentrations of calphostin C and then incubated for 16 h in medium containing 10% LPDS or 10% LPDS supplemented with 10 μg of cholesterol per ml and 10 μg of 25-hydroxycholesterol per ml. Total cellular RNA was subjected to Northern blotting to determine the amounts of LDL receptor, SS, and actin mRNAs. Autoradiographs were quantitated densitometrically, as described previously (55). LDL receptor mRNA levels were normalized by comparison with levels of actin mRNA. In the bottom panel, results are expressed as X-fold induction by 10% LPDS in the presence of calphostin C compared with untreated cells incubated in 10% LPDS plus sterols (given an arbitrary value of 1). Values shown are the averages of two different experiments. The experiment was repeated two times with similar results.