Mara Duncan, PhD

In the Duncan lab, we ask fundamental questions about how cells work. Our projects seek to understand the proteins important for membrane traffic, the process by which trans-membrane proteins and proteins inside organelle arrive at their correct location. Our work investigates the molecular mechanisms underlying the movement of proteins between organelles, we identify the proteins that function in this process, how they interact with one another, and broadly how the process of membrane traffic contributes to global cell functions including nutrient responses, signal transduction, and morphology at the cellular and tissue level.

Intracellular organelles allow eukaryotic cells to perform complex biochemical and cellular behaviors. Organelles such as the E.R., Golgi, endosomes and lysosome are completely enclosed in a lipid membrane. This complete enclosure allows each compartment to maintain an environment of chemical properties and enzymatic content distinct from the rest of the cell. The ability to maintain a unique environment, allows organelles to perform specialized chemical reactions that would not be possible without the complete separation afforded by the lipid membrane.

Although the lipid membrane is essential for the function of the organelles, it poses a problem; the membrane forms an impenetrable barrier to proteins. The cell therefore has specialized mechanisms that allow the enzymatic proteins needed for organelle function to get into each organelle. This mechanism is membrane traffic. In membrane traffic, proteins move between organelles via vesicles or related larger membrane bounded carriers. The formation of transport carriers is a complex process. Projects in the lab examine the molecular mechanisms leading to the formation of transport carriers.

The molecular mechanisms and biophysics of clathrin coat assembly:
Clathrin is a major player in traffic at many locations in the cell. Determining how clathrin mediates traffic is critical to our understanding of how the process is regulated and ultimately how it contributes to cellular behavior. We are investigating how clathrin dependent carriers form at the trans-Golgi Network (TGN) and endosomes in the yeast Saccharomyces cerevisiae. This eukaryotic model organism provides many advantages over larger model organisms for biophysical studies. Using highly efficient homologous recombination, we re-engineer genes to express proteins with altered binding affinities to test models of how proteins contribute to clathrin mediated traffic. Using cutting edge imaging and analysis technologies, we evaluate the effects of such changes on the kinetics and efficiency of membrane traffic. Using whole cell phenotypic analysis, we investigate the functional consequences of such changes to cell behavior. The goal our work is to understand clathrin carrier formation at the molecular level.

The contribution of membrane traffic to physiology :
Membrane traffic is critical for nearly every cellular function, from signaling to morphology to nutrient uptake. Many genes involved in membrane traffic are required at the earliest stages of development. We are leveraging cutting edge developments in gene editing and stem cell biology to examine the roles of membrane traffic diverse developmental contexts.