title: The Localization of Cytochrome P450s CYP1A1 and CYP1A2 into Different Lipid Microdomains Is Governed by Their N-terminal and Internal Protein Regions.
abstract: In cellular membranes, different lipid species are heterogeneously distributed forming domains with different characteristics. Ordered domains are tightly packed with cholesterol, sphingomyelin, and saturated fatty acids, whereas disordered domains contain high levels of unsaturated fatty acids. Our laboratory has shown that membrane heterogeneity affects the organization of cytochrome P450s and their cognate redox partner, the cytochrome P450 reductase (CPR). Despite the high degree of sequence similarity, CYP1A1 was found to localize to disordered regions, whereas CYP1A2 resided in ordered domains. We hypothesized that regions of amino acid sequence variability may contain signal motifs that direct CYP1A proteins into ordered or disordered domains. Thus, chimeric constructs of CYP1A1 and CYP1A2 were created, and their localization was tested in HEK293T cells. CYP1A2, containing the N-terminal regions from CYP1A1, no longer localized in ordered domains, whereas the N terminus of CYP1A2 partially directed CYP1A1 into ordered regions. In addition, intact CYP1A2 containing a 206-302-residue peptide segment of CYP1A1 had less affinity to bind to ordered microdomains. After expression, the catalytic activity of CYP1A2 was higher than that of the CYP1A1-CYP1A2 chimera containing the N-terminal end of CYP1A1 with subsaturating CPR concentrations, but it was approximately equal with excess CPR suggesting that the localization of the CYP1A enzyme in ordered domains favored its interaction with CPR. These data demonstrate that both the N-terminal end and an internal region of CYP1A2 play roles in targeting CYP1A2 to ordered domains, and domain localization may influence P450 function under conditions that resemble those found in vivo.
authors.affiliation: From the Department of Pharmacology and Experimental Therapeutics, and The Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, New Orleans, Louisiana 70112.
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Park
authors.affiliation: From the Department of Pharmacology and Experimental Therapeutics, and The Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, New Orleans, Louisiana 70112.
authors.forename: James R
authors.initials: JR
authors.lastname: Reed
authors.affiliation: From the Department of Pharmacology and Experimental Therapeutics, and The Stanley S. Scott Cancer Center, Louisiana State University Health Science Center, New Orleans, Louisiana 70112 wbacke@lsuhsc.edu.
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Backes
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry*; D018613:Microscopy, Confocal; D008862:Microsomes, Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D008055:Lipids; D009841:Oligonucleotides; D011993:Recombinant Fusion Proteins; C569463:CYP1A1 protein, human; C504573:CYP1A2 protein, human; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2
keywords: cytochrome P450; endoplasmic reticulum (ER); lipid microdomains; lipid raft; membrane protein; microdomain localization; microdomain targeting motifs; protein chimera; protein domain; protein-lipid interaction