title: Effect of Cholesterol on the Interaction of Cytochrome P450 Substrate Drug Chlorzoxazone with the Phosphatidylcholine Bilayer.
abstract: Many drugs are oxidized by membrane protein cytochrome P450 (CYP) enzymes during their metabolism process. CYPs are located mainly in endoplasmic reticulum (ER) membranes. Recent studies have suggested that CYP substrate drugs first bind the lipid bilayers of ER membranes and then the drugs reach the active site of CYP by way of an access channel. The entrance of the channel is located in the hydrophobic regions of the lipid bilayers. One of the features of the ER membrane is a cholesterol content that is lower than those of other biomembranes. In this study, the cholesterol concentration dependence of the interaction of a CYP substrate drug, chlorzoxazone (CZX), with model membranes composed of phosphatidylcholine (PC) and cholesterol was examined via differential scanning calorimetry (DSC), UV-visible spectroscopy, and X-ray diffraction. Experimental results indicated that CZX can bind to pure PC bilayers in the absence of cholesterol and that, by contrast, a high cholesterol concentration (30-50 mol %) tends to prevent CZX from binding to PC bilayers. Interestingly, the effect of cholesterol on the binding and insertion of CZX was biphasic. In the case of palmitoyloleoylphosphatidylcholine (POPC) bilayers containing 5-10 mol % cholesterol, the CZX's binding and penetration into the bilayer were found to be greater than those with pure POPC bilayers. The concentration of 5-10 mol % nearly corresponds to the cholesterol concentration of ER membranes. The low cholesterol contents (12-20 mol %) of ER membranes might be the most suitable for the CYP drug metabolism process in ER membranes.
authors.affiliation: Biophysics Laboratory, Division of Pure and Applied Science, Graduate School of Science and Technology, Gunma University , 4-2 Aramaki, Maebashi, Gunma 371-8510, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Yamada
authors.affiliation: Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization , 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Shimizu
authors.affiliation: RIKEN SPring-8 Center , 1-1-1 Kouto, Sayo, Hyougo 679-5148, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Hikima
authors.affiliation: RIKEN SPring-8 Center , 1-1-1 Kouto, Sayo, Hyougo 679-5148, Japan.|Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Takata
authors.affiliation: Lipid Biology Laboratory, RIKEN , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Biophysics Laboratory, Division of Pure and Applied Science, Graduate School of Science and Technology, Gunma University , 4-2 Aramaki, Maebashi, Gunma 371-8510, Japan.|RIKEN SPring-8 Center , 1-1-1 Kouto, Sayo, Hyougo 679-5148, Japan.|Lipid Biology Laboratory, RIKEN , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D002753:Chlorzoxazone / Q000378:metabolism*; D002784:Cholesterol / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol; D002753:Chlorzoxazone