My background is in chemical biology, metabolism and systems biology. I am broadly interested in developing innovative approaches to study the inner workings of biological systems. My previous research has focused on developing and applying genetically encoded tools for manipulation of redox balance and on using natural products to identify inhibitors of previously undruggable proteins. In future, I plan to build on my previous work to develop a suite of genetically encoded tools for compartment-specific manipulation of intracellular metabolic parameters and apply them to study the regulation of metabolism with the goal of gaining mechanistic insight into the beneficial effects of diet and exercise on age-associated disorders.
NAD+ and NADH are coenzymes used to catalyze redox reactions. Changes in the NAD+/NADH ratio are implicated in regulation of many metabolic pathways and are correlated with several pathologic conditions including cancer, diabetes and the aging process itself. The causal relationship between changes in the NAD+/NADH ratio and physiological effects remains poorly understood. An important barrier to understanding the role of changes in the NAD+/NADH ratio in regulation of biological processes is the lack of methods for compartment-specific manipulation of this parameter. During my postdoctoral training, I have developed a genetically encoded tool for compartment-specific increase of the NAD+/NADH ratio in mammalian cells. This tool is based on the water-forming NADH oxidase from Lactobacillus brevis (LbNOX), which catalyzes the reaction between NADH and oxygen to make NAD+ and water. LbNOX represents a new genetic toolkit for manipulation of redox metabolism and can be used to study the regulation and physiological role of compartment- and tissue-specific changes of the NAD+/NADH ratio.
Mitochondrial electron transport chain (ETC) catalyzes two important reactions: i) maintenance of the NAD+/NADH ratio by oxidation of NADH to NAD+ and ii) generation of mitochondrial membrane potential by pumping protons outside of mitochondria. It has been impossible to determine if a phenotype caused by ETC dysfunction is the result of the inhibition of the first or second reaction because they are coupled to each other and occur simultaneously. This is however critical as a decline in ETC activity is associated with many human diseases. To uncouple these two mechanisms, I used LbNOX, which only catalyzes the first reaction, to induce a compartment-specific increase of the NAD+/NADH ratio in human cells. Expression of LbNOX in the cytosol or mitochondria of mammalian cell lines fully rescued the proliferative and metabolic defects caused by an impaired ETC. This result demonstrates that maintenance of the NAD+/NADH ratio, not ATP synthesis, is an essential function of the ETC that is required for mammalian cell proliferation. In future, tissue- and compartment-specific LbNOX expression in model organisms can be used to determine whether maintenance of the NAD+/NADH ratio or generation of mitochondrial membrane potential is responsible for different phenotypes observed due to ETC dysfunction.
Identification of the target of the bioactive natural product triptolide