The primary research interest of the Kenworthy laboratory is in cell membrane structure. Over the past 15 years, a model has emerged that emphasizes the role of lateral heterogeneities in regulating membrane structure and function. This model, termed the lipid raft hypothesis, postulates that cholesterol- and sphingolipid-enriched membrane microdomains act as platforms that function to organize proteins, concentrating some proteins together within the same raft while segregating raft from non-raft proteins. Lipid rafts are now thought to participate in a wide range of cellular functions, ranging from membrane trafficking, to cell signaling, to pathogen exit and entry from cells. Despite the widespread implications of this model for human health, many of the fundamental properties of lipid rafts, such as their structure, composition, and lifetime are still poorly understood. To gain better insights into the features of these elusive domains, the lab is using a combination of cell biology and quantitative fluorescence microscopy to study the spatial distribution and dynamics of raft-associated proteins and lipids in cells, such as the glycolipid-binding bacterial toxin, cholera toxin. The Kenworthy lab is also investigating how the membrane curvature-inducing protein caveolin-1 contributes to the assembly of another class of plasma membrane domains known as caveolae, as well as functions of caveolin-1 at novel sites within the cell.