title: Cytochrome P450 system proteins reside in different regions of the endoplasmic reticulum.
abstract: Cytochrome P450 (P450) function is dependent on the ability of these enzymes to successfully interact with their redox partners, NADPH-cytochrome P450 reductase (CPR) and cytochrome b5, in the endoplasmic reticulum (ER). Because the ER is heterogeneous in lipid composition, membrane microdomains with different characteristics are formed. Ordered microdomains are more tightly packed, and enriched in saturated fatty acids, sphingomyelin and cholesterol, whereas disordered regions contain higher levels of unsaturated fatty acids. The goal of the present study was to determine whether the P450 system proteins localize to different regions of the ER. The localization of CYP1A2, CYP2B4 and CYP2E1 within the ER was determined by partial membrane solubilization with Brij 98, centrifugation on a discontinuous sucrose gradient and immune blotting of the gradient fractions to identify ordered and disordered microdomains. CYP1A2 resided almost entirely in the ordered regions of the ER with CPR also localized predominantly to this region. CYP2B4 was equally distributed between the ordered and disordered domains. In contrast, CYP2E1 localized to the disordered membrane regions. Removal of cholesterol (an important constituent of ordered domains) led to the relocation of CYP1A2, CYP2B4 and CPR to the disordered regions. Interestingly, CYP1A1 and CYP1A2 localized to different membrane microdomains, despite their high degree of sequence similarity. These data demonstrate that P450 system enzymes are organized in specific membrane regions, and their localization can be affected by depletion of membrane cholesterol. The differential localization of different P450 in specific membrane regions may provide a novel mechanism for modulating P450 function.
authors.affiliation: *Department of Pharmacology and Experimental Therapeutics, Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, 533 Bolivar St. New Orleans, LA 70112, U.S.A.
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Park
authors.affiliation: *Department of Pharmacology and Experimental Therapeutics, Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, 533 Bolivar St. New Orleans, LA 70112, U.S.A.
authors.forename: James R
authors.initials: JR
authors.lastname: Reed
authors.affiliation: *Department of Pharmacology and Experimental Therapeutics, Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, 533 Bolivar St. New Orleans, LA 70112, U.S.A.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Brignac-Huber
authors.affiliation: *Department of Pharmacology and Experimental Therapeutics, Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, 533 Bolivar St. New Orleans, LA 70112, U.S.A.
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Backes
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000737:chemistry* / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000737:chemistry* / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000737:chemistry* / Q000378:metabolism; D000072467:Cytochrome P450 Family 2; D004721:Endoplasmic Reticulum / Q000737:chemistry* / Q000201:enzymology; D021962:Membrane Microdomains / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D010938:Plant Oils / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D011817:Rabbits
chemical_list: D010743:Phospholipids; D010938:Plant Oils; D011092:Polyethylene Glycols; C033084:polyethylene glycol oleyl ether; D019392:Cytochrome P-450 CYP2E1; D001189:Aryl Hydrocarbon Hydroxylases; D019388:Cytochrome P-450 CYP1A2; D000072467:Cytochrome P450 Family 2; C465241:cytochrome P-450 CYP2B4 (rabbit); D009251:NADPH-Ferrihemoprotein Reductase