Cytochrome P450 metabolism of the post-lanosterol intermediates explains enigmas of cholesterol synthesis.

Jure Ačimovič,Damjana Rozman,Marko Goličnik,Žiga Urlep,Ales Belič,F Peter Guengerich,Martina Perše,Rok Košir,Sandeep Goyal

doi:10.1038/srep28462

Abstract

Cholesterol synthesis is among the oldest metabolic pathways, consisting of the Bloch and Kandutch-Russell branches. Following lanosterol, sterols of both branches are proposed to be dedicated to cholesterol. We challenge this dogma by mathematical modeling and with experimental evidence. It was not possible to explain the sterol profile of testis in cAMP responsive element modulator tau (Crem τ) knockout mice with mathematical models based on textbook pathways of cholesterol synthesis. Our model differs in the inclusion of virtual sterol metabolizing enzymes branching from the pathway. We tested the hypothesis that enzymes from the cytochrome P450 (CYP) superfamily can participate in the catalysis of non-classical reactions. We show that CYP enzymes can metabolize multiple sterols in vitro, establishing novel branching points of cholesterol synthesis. In conclusion, sterols of cholesterol synthesis can be oxidized further to metabolites not dedicated to production of cholesterol. Additionally, CYP7A1, CYP11A1, CYP27A1, and CYP46A1 are parts of a broader cholesterol synthesis network.

Highlights

Cholesterol synthesis is among the oldest metabolic pathways, consisting of the Bloch and KandutchRussell branches
The relative expression levels of 15 cholesterogenic genes, Crem−/− compared to wild-types (WT), are shown in Fig. 1, with 13 of them being involved in the cholesterol synthesis pathway and two in post-cholesterol synthesis transformations of cholesterol (cytochrome P450-family11-subfamily-A-polypeptide-1 (Cyp11a1) gene and cytochrome P450, family 27, subfamily A, polypeptide 1 (Cyp27a1) gene)
Five genes of the cholesterol synthesis pathway showed statistically significant higher expressions in Crem−/− compared to WT animals, Hmgcr (1.65-fold), Fdft[1] (3.09-fold), Sqle (1.42-fold), Hsd17b7 (1.55-fold) and Ebp (1.81-fold), with p-values lower than 0.001, 0.001, 0.05, 0.001, and 0.001, respectively

Summary

Introduction

Cholesterol synthesis is among the oldest metabolic pathways, consisting of the Bloch and KandutchRussell branches. Cholesterol synthesis is a basic pathway believed to take place in virtually all mammalian cells In this anabolic pathway the cholesterol molecule is built from acetate in over 30 reactions and enzymes from different protein families. In the Bloch branch, the final reaction to form cholesterol involves the conversion of desmosterol to cholesterol by sterol-Δ24-reductase (DHCR24); all intermediates from lanosterol to desmosterol contain an unsaturated Δ24 bond. We show here that intermediates of the Bloch and K-R branches leak from the pathway and can be metabolized by enzymes of the cytochrome P450 (CYP) superfamily in the testes of mice with defective post-lanosterol cholesterol synthesis. In this work we provide evidence of novel branching points in the post-lanosterol cholesterol synthesis and reveal new roles of CYP enzymes in cholesterol homeostasis

Methods

Results

Discussion

Conclusion