Regulation of Xenobiotic- and Endobiotic-Metabolizing Enzyme Expression and Function

Xenobiotic/endobiotic-metabolizing enzymes catalyze the bioactivation and detoxification of drugs, carcinogens, environmental toxicants, and endogenous chemicals. A LONG-TERM GOAL of my research program is to understand how biochemical, molecular, and cellular factors regulate these enzymes and their biological functions, thereby advancing the fundamental science underlying individual variations in response to chemicals. A focus of my research program is on a xenobiotic/endobiotic-metabolizing enzyme known as aldehyde oxidase-1 (AOX1), which metabolizes azaheterocyclic drugs, other xenobiotics, and endogenous chemicals of physiological importance. It has contributed to chemical-induced toxicity in humans and failures in drug development. AOX1 expression and catalytic activity show large individual variations, but the underlying mechanisms for this biological phenomenon and its physiological functions are not known. Given the large knowledge gap on the fundamental biology of AOX1, an increasingly important yet relatively uncharacterized enzyme expressed in many tissues, the OVERALL OBJECTIVE of my current NSERC DG application is to unravel the fundamental mechanisms regulating AOX1 gene expression and function, and determine how genetic and non-genetic factors impact AOX1 biological functions. The SPECIFIC AIMS are to 1) elucidate the biochemical, molecular, and cellular mechanisms by which various nuclear receptors transcriptionally regulate AOX1 expression and function; 2) investigate how naturally-occurring AOX1 genetic variants affect its expression, chemical-enzyme interaction, and enzymatic function; and 3) explore the role of microRNAs (epigenetic modulators) in the post-transcriptional regulation of AOX1 expression and function. METHODOLOGY. The experimental approaches will include various biochemical, molecular biology, and pharmacological techniques in cell culture models. State-of-art technologies, including ultra-high-performance liquid chromatography-tandem mass spectrometry, quantitative targeted proteomics, chromatin immunoprecipitation-sequencing, and gene editing, will be used. IMPACT. My research program will discover new fundamental concepts of AOX1 regulation by nuclear receptors, genetic/transcript variants, microRNAs, various exogenous/endogenous chemicals, and the complex interplay or cross-regulation among the regulatory factors. The mechanistic information generated will 1) identify novel biochemical and molecular approaches to modulate the biological function of an enzyme; 2) provide novel insights into the molecular and genetic basis on why individuals respond differently to certain drugs, toxicants, other xenobiotics, and endogenous chemicals; and 3) allow us to predict individual variations in AOX1-mediated chemical action and toxicity. My research program will train the next generation of research scientists for the life sciences/biotechnology/pharmaceutical sectors in Canada.