Expression of constitutive androstane receptor splice variants in human tissues and their functional consequences. J Pharmacol Exp Ther 2004 Nov;311(2):811-21
Date
06/15/2004Pubmed ID
15194709DOI
10.1124/jpet.104.069310Scopus ID
2-s2.0-6344266966 (requires institutional sign-in at Scopus site) 91 CitationsAbstract
The constitutive androstane receptor (CAR) NR1I3 is a transcription factor that upon activation by xenobiotics induces transcription of drug-metabolizing and drug transporter genes. Our goal was to identify whether alternative splicing of CAR makes an important contribution to the generation of novel CAR proteins. The wild-type CAR mRNA (CAR.1) and splice variants (SVs) were amplified from human liver cDNAs and in a panel of cDNAs from 36 human tissues, using exon 1- and 3'-untranslated region primers, cloned and sequenced. Twenty-two unique hCAR splice variants (CAR-SVs) containing different combinations of splicing (deletion of exons 2, 4, 5, 7, partial deletion of exon 9, or insertion of 12 or 15 base pairs from introns 6 or 7) were identified. CAR mRNAs were expressed in small intestine, kidney, testis, adrenal, and brain caudate nucleus. Intestine expressed only CAR.1 mRNA, whereas spleen, heart, and prostate expressed only CAR-SVs. In vitro transcription and translation of CAR-SVs lacking exon 2 (missing ATG start site) generated CAR proteins that differed in M(r) from CAR.1. These CAR-SVs used a translation initiation site in exon 1, generating CAR with a unique amino-terminal sequence. Transcripts lacking part of exon 9 altered the CAR reading frame generating CAR proteins with a unique carboxy-terminal end. CAR-SVs demonstrated compromised binding to CYP2B6 NR elements and transcriptional activation of a CYP2B6 luciferase reporter. The expression of CAR in additional human cell types increases the range of tissue specific transcriptional responses regulated by this receptor, suggesting additional biological roles for CAR and CAR-SV proteins in these tissues.
Author List
Lamba JK, Lamba V, Yasuda K, Lin YS, Assem M, Thompson E, Strom S, Schuetz EAuthor
Mahfoud Assem PharmD Associate Professor in the School of Pharmacy Administration department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Alternative SplicingAmino Acid Sequence
Base Sequence
Computational Biology
DNA
Gene Expression Profiling
Gene Expression Regulation
Humans
Molecular Sequence Data
Protein Isoforms
RNA, Messenger
Receptors, Cytoplasmic and Nuclear
Transcription Factors
Transcriptional Activation
