Role of phosphatidic acid phosphatase type 2 domain containing 2 (PPAPDC2) in squalestatin 1‐mediated CYP2B1 induction in primary cultured rat hepatocytes

Abstract

Inhibition of squalene synthase causes accumulation of farnesyl pyrophosphate (FPP) in primary cultured rat hepatocytes, which increases CYP2B expression through activation of the constitutive androstane receptor (CAR). However, the identity of the CAR‐activating isoprenoid has not been established. Since the lipid phosphatase PPAPDC2 has recently been reported to catalyze FPP dephosphorylation (Miriyala et al., J Biol Chem 285:13918–13929, 2010), we determined the effect of PPAPDC2 overexpression and knockdown on squalestatin 1 (SQ1)‐mediated activation of a CAR‐responsive CYP2B1 luciferase reporter in primary cultured rat hepatocytes. Treatment with 100 nM SQ1 increased reporter expression ~11‐fold in hepatocytes that were co‐transfected with empty expression plasmid. The SQ1‐mediated induction was enhanced ~2‐ or 1.5‐fold when the hepatocytes were co‐transfected with an expression plasmid for rat or human PPAPDC2. SQ1‐inducible reporter expression was not affected by co‐transfection of a non‐targeting shRNA but was reduced ~60% by co‐transfection with a PPAPDC2 shRNA. These results indicate that PPAPDC2 plays an important role in SQ1‐mediated CYP2B1 induction, most probably by catalyzing the conversion of FPP to farnesol. This work was supported by NIH grant R01HL050710. Asmita Pant is supported by a Thomas Rumble Fellowship.