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Organization of NADPH‐Cytochrome P450 Reductase and CYP1A2 in the Endoplasmic Reticulum – Microdomain localization affects monooxygenase function
Author(s) -
BrignacHuber Lauren Michelle,
Reed James,
Backes Wayne L
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1014.11
Subject(s) - endoplasmic reticulum , cyp1a2 , lipid microdomain , sphingomyelin , phosphatidylcholine , microsome , reductase , cytochrome p450 , chemistry , cytochrome , biochemistry , vesicle , cytochrome p450 reductase , cholesterol , metabolism , enzyme , phospholipid , cytochrome c , membrane , coenzyme q – cytochrome c reductase , mitochondrion
Cytochrome P450 is found in the endoplasmic reticulum (ER), with its catalytic function requiring interactions with NADPH‐cytochrome P450 reductase (CPR). The goals of this study were to examine how the P450 system proteins are organized in the membrane and to determine if they are distributed in detergent‐resistant lipid microdomains (DRM). Liver microsomes from untreated rabbits were treated with 1% Brij 98, and DRMs were isolated via sucrose gradient centrifugation. Lipid analysis showed that DRM fractions were enriched in cholesterol and sphingomyelin, similar to that found at the plasma membrane DRMs. Approximately 73% of CYP1A2 and 68% of CPR resided in DRM fractions as compared to only 33% of total ER proteins. Cholesterol depletion experiments suggest that these DRMs are cholesterol‐dependent. CYP1A2 function was studied in three purified lipid vesicles consisting of 1) phosphatidylcholine (V‐PC), 2) lipids with composition similar to ER lipids (V‐ER) and 3) lipids with composition similar to the DRMs (V‐DRM). Association between CPR and CYP1A2 were measured and V‐ER and V‐DRM vesicles produced lower apparent K m values compared to V‐PC without any significant change in V max . These findings suggest that CYP1A2 and CPR reside in ER‐DRMs and that the unique lipid components of these domains enhance CYP1A2 substrate metabolism through more efficient CPR‐CYP1A2 binding. Supported by NIEHS ES004344