Faculty Research Page

Denis Titov

Denis Titov

Pending Appointment in Cell and Developmental Biology

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Research Interests

Aging is the result of progressive damage of cellular components throughout the lifespan of an organism. The accumulation of damaged molecules eventually leads to the breakdown of cellular and organismal homeostasis. The long-term goal of my laboratory is to understand the molecular basis of inactivation of cellular functions during aging. In particular, we are interested in addressing the following broad questions: What are the molecular mechanisms of age-associated damage to proteins, nucleic acids and lipids? Why do some damaged components get repaired, while others accumulate? How do environmental and genetic factors modulate the rate of accumulation of age-associated damage?

In order to tackle these questions we are using a combination of biochemistry, physiology, mathematical modeling and novel tool development to study aging in cell culture and model organisms.

Current Projects

Current projects in the laboratory are focused on understanding how changes in metabolism induced by diet and exercise modulate aging and age-associated diseases. Many studies have demonstrated that diet and exercise are associated with increase in lifespan of model organisms and a decrease in human mortality from various diseases including heart disease, stroke, diabetes, cancer and neurodegenerative disorders. We are working on creating a suite of novel genetically encoded tools for manipulation of metabolism in living organisms that will allow us to identify the specific changes in metabolism that mediate the beneficial effects of diet and exercise.

Genetically encoded tools for manipulation of metabolism (GEMMs)
At a cellular level, the key response to dietary manipulations and exercise involves changes in intracellular metabolic parameters such as ATP/ADP, NADH/NAD+, NADPH/NADP+, GSH/GSSG ratios and mitochondrial membrane potential (ΔΨm). The causal relationship between changes in these crucial parameters and downstream effects of diet and exercise is currently unknown. A key bottleneck in understanding the role of intracellular metabolic parameters in regulation of metabolism has been the lack of methods for direct manipulation of these parameters in vivo. To fill this methodological gap, we have introduced two genetically encoded tools for manipulation of NADH/NAD+ and NADPH/NADP+ ratios in living cells. We are currently working on expanding this toolkit to other metabolic parameters, which will allow us to mimic metabolic changes induced by exercise and dietary changes in cell culture and model organisms.

Mechanism of lifespan extension by calorie restriction
Calorie restriction (CR) has been shown to extend the lifespan of yeast, worms, flies, mice and primates, which makes it the most robust method of lifespan extension known to date. Elucidation of the mechanism of CR-mediated lifespan extension will dramatically increase our understanding of the aging process. CR induces dramatic changes in energy metabolism but it remains unclear which specific changes in metabolism are responsible for mediating the beneficial effects of calorie restriction. We're using GEMMs to mimic the effect of CR on different energy metabolism pathways of C. elegans to uncover the specific metabolic changes that are necessary and sufficient for CR-mediated extension of lifespan.

Regulation of energy metabolism
Modulation of energy metabolism is implicated in mediating the beneficial effects of diet and exercise on aging and age-associated diseases. Regulation of energy metabolism pathways is incompletely understood because most of our knowledge about regulation of these pathways is based on experiments with purified enzymes, tissue extracts and isolated mitochondria that do not fully capture the complexities of the intracellular environment. We are using GEMMs to study the mechanisms of regulation of energy metabolism pathways in living mammalian cells. Specifically, we want to address several unanswered questions about the
 regulation of energy metabolism pathways: Do cells communicate intracellular energy status through autocrine, paracrine or endocrine signaling? How do changes in metabolic parameters affect ROS production? What is the mechanism of Crabtree, Warburg and Pasteur effects?

Selected Publications

Titov D.V.*, Cracan V.*, Goodman R.P., Peng J., Grabarek Z., Mootha V.K. Complementation of mitochondrial electron transport chain by manipulation of NAD+/NADH ratio. Science. 2016 Apr 8; 352(6282):231-5.

Cracan V.*, Titov D.V.*, Sheng H., Grabarek Z., Mootha V.K. Genetically encoded tool for manipulation of NADP+/NADPH ratio. Nature Chemical Biology. 2017 Oct; 13(10):1088-1095.

Titov D.V., Gilman B., He Q.-L., Bhat S., Low W.-K., Dang Y., Smeaton M., Demain A.L., Miller P.S., Kugel J.F., Goodrich J.A., Liu J.O. XPB, a Subunit of TFIIH, is a Target of the Natural Product Triptolide. Nature Chemical Biology. 2011 Mar;7(3):182-8.

* – these authors contributed equally to this work.

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Last Updated 2017-09-25