title: Co-regulation of CYP3A4 and CYP3A5 and contribution to hepatic and intestinal midazolam metabolism.
abstract: We recently demonstrated that a variant allele of CYP3A5 (CYP3A5*3) confers low CYP3A5 expression as a result of improper mRNA splicing. In this study, we further evaluated the regulation of CYP3A5 in liver and jejunal mucosa from white donors. For all tissues, high levels of CYP3A5 protein were strongly concordant with the presence of a wild-type allele of the CYP3A5 gene (CYP3A5*1). CYP3A5 represented greater than 50% of total CYP3A content in nearly all of the livers and jejuna that carried the CYP3A5*1 wild-type allele. Overall, CYP3A5 protein content accounted for 31% of the variability in hepatic midazolam hydroxylation activity. Improperly spliced mRNA (SV1-CYP3A5) was found only in tissues containing a CYP3A5*3 allele. Properly spliced CYP3A5 mRNA (wt-CYP3A5) was detected in all tissues, but the median wt-CYP3A5 mRNA was 4-fold higher in CYP3A5*1/*3 livers compared with CYP3A5*3/*3 livers. Differences in wt-CYP3A5 and CYP3A4 mRNA content explained 53 and 51% of the interliver variability in CYP3A5 and CYP3A4 content, respectively. Hepatic CYP3A4 and CYP3A5 contents were not correlated when all livers were compared. However, for CYP3A5*1/*3 livers, levels of the two proteins were strongly correlated (r = 0.93) as were wt-CYP3A5 and CYP3A4 mRNA (r = 0.76). These findings suggest that CYP3A4 and CYP3A5 genes share a common regulatory pathway for constitutive expression, possibly involving conserved elements in the 5'-flanking region.
authors.affiliation: Department of Pharmaceutics, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Yvonne S
authors.initials: YS
authors.lastname: Lin
authors.forename: Amy L S
authors.initials: AL
authors.lastname: Dowling
authors.forename: Sean D
authors.initials: SD
authors.lastname: Quigley
authors.forename: Federico M
authors.initials: FM
authors.lastname: Farin
authors.forename: Jiong
authors.initials: J
authors.lastname: Zhang
authors.forename: Jatinder
authors.initials: J
authors.lastname: Lamba
authors.forename: Erin G
authors.initials: EG
authors.lastname: Schuetz
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Thummel
mesh_terms: D000483:Alleles; D014151:Anti-Anxiety Agents / Q000378:metabolism / Q000493:pharmacokinetics*; D001483:Base Sequence; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D005838:Genotype; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000201:enzymology / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D008874:Midazolam / Q000378:metabolism / Q000493:pharmacokinetics*; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid
chemical_list: D014151:Anti-Anxiety Agents; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D008874:Midazolam