Fig. 6.

PCSK9 regulates basal intestinal LDLR protein levels in jejunum. (A) Immunoblot analysis of jejunocyte and liver membrane fractions from 13- to 16-week-old male wild-type or PCSK9 knockout mice fed diets with or without 0.01% ezetimibe for five days. Jejunocytes or livers (four mice per group) were fractionated and subjected to SDS-PAGE and immunoblot analysis as described in Fig. 1. (B) Comparison of relative hepatic and jejunocyte mRNA levels. Total RNA from jejunocytes or livers (four mice per group) was isolated and subjected to quantitative real-time PCR as described in Fig. 1. Wild-type animals are indicated by open circles, whereas PCSK9 knockout mice are indicated by filled circles. Ezetimibe administration is as indicated. mRNA levels from wild-type mice that did not receive ezetimibe were normalized to 1.0. (C) Quantitation of LDLR protein levels. Immunoblots from panel A were quantified by densitometry. Each bar represents the relative LDLR protein level from each group as described in panel A; protein levels from wild-type mice that did not receive ezetimibe were normalized to 1.0. (D) Relationship between IDOL expression and LDLR protein levels in jejunum of wild-type and PCSK9 knockout mice. Relative LDLR protein levels from panels A and C are plotted against IDOL mRNA from panel B. Wild-type mice that did not receive ezetimibe were normalized to 1.0 for protein and mRNA levels.