INBRE

The long-term goal of this project is to determine the molecular factors that govern the endotoxin and xenobiotic induced regulation of drug metabolizing enzymes (DME) and corresponding transporters. The major biological model for this project is C. elegans, however, all accumulated data will be compared to vertebrate models including humans. In the past several years, the nuclear receptor (NR) SXR has been implicated as a key mediator in endotoxin and xenobiotic activation of cytochromes P450 (CYP) in many species. In collaboration with Dr. Ron Evans from the Salk Institute, we accumulated data which demonstrates that SXR is also a critical regulator of UDP-glucuronosyltransferase (UGT) gene expression and activation of this receptor correlates to UGT induction. Two facts suggest that NR regulation of detoxification protein expression is a broadly conserved NR function. First, we have demonstrated that a nematode member of the SXR subfamily of NRs, NHR-8, contributes to C. elegans xenobiotic resistance. Secondly, within the genome of C. elegans, we have identified 38 open reading frames that encode proteins similar to the mammalian UGTs. Based on this analysis, we will study NHR-8 regulation of UGT expression in this nematode model system. The central hypothesis is that NHR-8 regulates the expression of the nematode detoxification network in response to the presence of endogenous and xenobiotic toxic compounds in a manner similar to the vertebrate model. We will (1) identify glucuronosyltransferase ( UGTs) and other drug metabolizing enzymes (DMEs) in the C. elegans genome, (2) characterize C. elegans UGT protein levels, expression, enzymatic activity and subcellular localization and (3) identify NHR-8 target loci within the UGT, CYP, and multidrug resistance gene families through the use of DNA microarray and quantitative RT-PCR analyses. It is anticipated that this project will demonstrate that detoxification via xenobiotic-sensing NRs is highly conserved in evolution. It is further postulated that the nematode detoxification network will exhibit a mammalian style mechanism of induction but might also exhibit unique nematode characteristics such as a more limited UGT substrate specificity. This research will generate the data we intend to utilize for the production of humanized nematode models of UGTs endotoxin and xenobiotic detoxification. Such a system would allow rapid and accurate analyses of drug modification and detoxification in a highly tractable and genetically amenable system. Further, this research lays the foundation for NHR-8 ligand discovery.

Back

Updated 10/28/2005

The Arkansas INBRE is Supported by a grant from the National Institutes of Health
and the National Center for Research Resources (P20 RR-16460).

Please contact Caroline Miller Robinson regarding questions or comments about this site or our program. For more information about the University of Arkansas for Medical Sciences visit http://www.uams.edu.