Research
Of the many fungal species that exist in the environment, only a select few cause disease in humans. Yet, the fungi that are pathogens of humans result in a significant number of deaths worldwide each year. Despite the importance of developing novel strategies and therapeutics for the control of fungal pathogens, the details of many molecular mechanisms that allow fungi to cause disease remain elusive.
How can the many saprophytic fungi survive host environments using mechanisms of thermotolerance, adaptation to different nutrient availability and fluctuations in pH and oxygens levels to become pathogens? How do these unique pathways intersect with other cellular processes in various pathogenic fungi? How do evolutionary forces that occur in temperate climates enable saprophytic fungi to acquire thermotolerance?
Our lab studies the molecular mechanisms of fungal pathogenesis, seeking to understand how fungal pathogens survive and proliferate in the presence of multiple stressors in the host environment. In particular, our lab aims to achieve a comprehensive understanding of the trehalose biosynthesis pathway in fungal pathogens and its role in thermotolerance and virulence. For this, we use techniques in structural biology, biochemistry and fungal genetics.
We combine structural, functional and pharmacological studies of fungal pathways involved in stress tolerance in hosts to (1) identify the fungal pathways/macromolecular machines involved in host survival, (2) understand the structural and functional determinants of fungal survival in the host and (3) develop new drugs to prevent proliferation of pathogenic fungi in hosts in vivo.
Trehalose Biosynthesis.
One of the current goals of the Washington laboratory is to determine the structure and function of proteins involved in trehalose biosynthesis. We are particularly interested in how this pathway contributes to fungal pathogenesis and how we can exploit it as an antifungal drug target.
Trehalose is a disaccharide composed of two molecules of glucose that is required for pathogenic fungi to survive in their human hosts. Trehalose biosynthesis is a two-step process. Trehalose-6-phosphate synthase (Tps1) converts UDP-glucose (UDP-Glc) and glucose-6-phosphate (G6P) to trehalose-6-phosphate (T6P). Subsequently, trehalose-6-phosphate phosphatase (Tps2) converts T6P to trehalose. Additionally, C. albicans and A. fumigatus express Tps3, a protein predicted to lack catalytic activity and mediate protein-protein interactions. The trehalose biosynthesis pathway is conserved among all major fungal pathogens and yet is absent in mammals.
Trehalose plays a major role as a stress molecule in fungal pathogens. Trehalose biosynthesis is induced by heat stress. We are particularly interested in how trehalose is induced by heat stress and how trehalose contributes to fungal thermotolerance.
The canonical trehalose biosyntheis pathway in fungal pathogens. The trehalose biosynthesis protein, Tps1, homo-tetramer from Cryptococcus neoformans (Washington et al (2024) PNAS).
Antifungal Drug Design.
The current arsenal of antifungal drugs is limited due to toxicity and antifungal drug resistance. The trehalose biosynthesis pathway is conserved among fungal pathogens, yet is not found in humans. Therefore, the trehalose biosynthesis pathway may be a critical antifungal drug target. Furthermore, genetically disrupting the trehalose biosynthesis pathway results in fungicidal effects during infections.
In the Washington lab, we developing the trehalose biosynthesis pathway as an antifungal drug target. Our ability to purify large amounts of both Tps1 and Tps2 enables us to perform high throughput screens.
This work is done in collaboration with the Brennan lab (Duke), the Lee lab (St. Jude) and the Perfect lab (Duke).
Climate Change.
Changes in the environment due to climate change have major consequences in the realm of infectious diseases. It has been hypothesized that new fungal pathogens are emerging due to climate change. One method by which new fungal pathogens can emerge is by acquiring thermotolerance, or the ability to survive in high temperatures. The trehalose biosynthesis pathway is required for thermotolerance in major fungal pathogens.
Our goal is to understand how trehalose biosynthesis contributes to thermotolerance in both commonly used lab strains as well as environmental and clinical strains.
Trehalose biosynthesis increases during heat stress.
