Abstract/Details

Regulation of two P450 isoforms: CYP2D6 and CYP4F11


2009 2009

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Abstract (summary)

Cytochromes P450 catalyze a monooxygenase reaction in which molecular oxygen is split and one oxygen atom is incorporated into the substrate. As a whole, P450 researchers have focused most of their attention on substrate metabolism and relatively little on how these enzymes are regulated. This study will focus on the regulation of two P450 isoforms known as, CYP2D6 and CYP4F11.

The human CYP2D gene locus contains two pseudogenes and one functional gene known as CYP2D6. This locus is highly polymorphic and produces several alternatively spliced transcripts from the pseudogene CYP2D7. My objective was to understand the role of SV5-in (splice variant 5), one of several alternative splice variants transcribed from the CYP2D7 pseudogene. My results indicate that SV5-in mRNA causes an increase in CYP2D6 protein levels and suggest that there is a role for SV5-in in regulation of CYP2D6 expression.

Second, CYP4F11 is a recently discovered and uncharacterized isoform, derived from the CYP4F subfamily. It metabolizes several clinically relevant drugs (i.e.—erythromycin and benzphetamine) and some endogenous inflammatory mediators (i.e.—LTB4). After evaluation of microarray data, I observed an increase in CYP4F11 mRNA levels from wild-type HCT116 cells compared to p53-null cells. Our objectives were to explore and understand this connection between p53 and CYP4F11. Microarray data were confirmed by Q-PCR, after which this effect was again observed at the protein level via Western blot and again at the promoter level via luciferase assay and chromatin immunoprecipitation. Our results indicate that p53 protein regulates expression of CYP4F11 mRNA and protein through CYP4F11 promoter binding (note that p53 binding to CYP4F11 DNA was not shown to be direct). These results signify a whole new level of regulation of drug metabolizing enzymes by p53.

An understanding of CYP4F11 regulation by p53 could help us understand another pathway leading to apoptosis or cell growth arrest. This can aid future drug studies and discover new drug metabolism pathways under the control of a tumor suppressor protein. An understanding of the CYP2D6 regulation pathway could illuminate the role of non-coding RNAs in the P450 field and potentially explain several inter-individual drug response variations observed in clinical medicine that are not yet completely explained by genotyping analysis.

Indexing (details)


Subject
Molecular biology;
Cellular biology;
Biochemistry
Classification
0307: Molecular biology
0379: Cellular biology
0487: Biochemistry
Identifier / keyword
Pure sciences; Biological sciences; Cytochrome P450; Splice variants; p53
Title
Regulation of two P450 isoforms: CYP2D6 and CYP4F11
Author
Ryder, Daniel J.
Number of pages
112
Publication year
2009
Degree date
2009
School code
2034
Source
DAI-B 70/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9781109377248
Advisor
Strobel, Henry W.
University/institution
The University of Texas Graduate School of Biomedical Sciences at Houston
University location
United States -- Texas
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3376899
ProQuest document ID
305173152
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305173152
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