RT Journal Article SR Electronic T1 Co-Regulation of CYP3A4 and CYP3A5 and Contribution to Hepatic and Intestinal Midazolam Metabolism JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 162 OP 172 DO 10.1124/mol.62.1.162 VO 62 IS 1 A1 Yvonne S. Lin A1 Amy L. S. Dowling A1 Sean D. Quigley A1 Federico M. Farin A1 Jiong Zhang A1 Jatinder Lamba A1 Erin G. Schuetz A1 Kenneth E. Thummel YR 2002 UL http://molpharm.aspetjournals.org/content/62/1/162.abstract AB 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 theCYP3A5 gene (CYP3A5*1).CYP3A5 represented greater than 50% of total CYP3A content in nearly all of the livers and jejuna that carried the CYP3A5*1wild-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 splicedCYP3A5 mRNA (wt-CYP3A5) was detected in all tissues, but the median wt-CYP3A5 mRNA was 4-fold higher in CYP3A5*1/*3 livers compared withCYP3A5*3/*3 livers. Differences inwt-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, forCYP3A5*1/*3 livers, levels of the two proteins were strongly correlated (r = 0.93) as werewt-CYP3A5 and CYP3A4 mRNA (r = 0.76). These findings suggest thatCYP3A4 and CYP3A5 genes share a common regulatory pathway for constitutive expression, possibly involving conserved elements in the 5′-flanking region.