title: Progesterone receptor membrane component 1 inhibits the activity of drug-metabolizing cytochromes P450 and binds to cytochrome P450 reductase.
abstract: Progesterone receptor membrane component 1 (PGRMC1) has been shown to interact with several cytochromes P450 (P450s) and to activate enzymatic activity of P450s involved in sterol biosynthesis. We analyzed the interactions of PGRMC1 with the drug-metabolizing P450s, CYP2C2, CYP2C8, and CYP3A4, in transfected cells. Based on coimmunoprecipitation assays, PGRMC1 bound efficiently to all three P450s, and binding to the catalytic cytoplasmic domain of CYP2C2 was much more efficient than to a chimera containing only the N-terminal transmembrane domain. Down-regulation of PGRMC1 expression levels in human embryonic kidney 293 and HepG2 cell lines stably expressing PGRMC1-specific small interfering RNA had no effect on the endoplasmic reticulum localization and expression levels of P450s, whereas enzymatic activities of CYP2C2, CYP2C8, and CYP3A4 were slightly higher in PGRMC1-deficient cells. Cotransfection of cells with P450s and PGRMC1 resulted in PGRMC1 concentration-dependent inhibition of the P450 activities, and this inhibition was partially reversed by increased expression of the P450 reductase (CPR). In contrast, CYP51 activity was decreased by down-regulation of PGRMC1 and expression of PGRMC1 in the PGRMC1-deficient cells increased CYP51 activity. In cells cotransfected with CPR and PGRMC1, strong binding of CPR to PGRMC1 was observed; however, in the presence of CYP2C2, interaction of PGRMC1 with CPR was significantly reduced, suggesting that CYP2C2 competes with CPR for binding to PGRMC1. These data show that in contrast to sterol synthesizing P450, PGRMC1 is not required for the activities of several drug-metabolizing P450s, and its overexpression inhibits those P450 activities. Furthermore, PGRMC1 binds to CPR, which may influence P450 activity.
authors.affiliation: Department of Molecular and Integrative Physiology, College of Medicine at Urbana-Champaign, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Szczesna-Skorupa
authors.forename: Byron
authors.initials: B
authors.lastname: Kemper
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D002460:Cell Line; D065727:Cytochrome P-450 CYP2C8; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D053833:Wetlands
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D008565:Membrane Proteins; C115296:PGRMC1 protein, human; D011980:Receptors, Progesterone; D003577:Cytochrome P-450 Enzyme System; C084930:cytochrome P-450 2C2; D001189:Aryl Hydrocarbon Hydroxylases; C450259:CYP2C8 protein, human; D065727:Cytochrome P-450 CYP2C8; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D009251:NADPH-Ferrihemoprotein Reductase