Structure and Assembly of Membrane Proteins at Tight Junctions

Project Summary Three families of membrane proteins in the apical compartments of epithelial and endothelial cells govern key structures and functions across human tissues that include cell adhesion, molecular transport, and cell signaling. As these membrane proteins bridge the intracellular, membrane, and extracellular spaces, they interact uniquely with each other and other proteins to assemble intricate ultrastructures. These ultrastructures regulate molecular transport function between cells at tight junctions and cell/cell communication at apical cell surfaces, enabling tissues to maintain homeostatic physiology. However, breakdowns in tissue integrity and cell signaling linked to mis-assembly of these tight junction membrane proteins cause tissue-specific pathologies like cancers, Alzheimer’s, Parkinson’s, Huntington’s, stroke, food poisoning and inflammatory bowel disease, renal wasting, hepatitis, and diseases of the skin, eyes, and ears. Therefore, the structures tight junction membrane proteins employ and the biophysical rules governing their assembly, which are currently unresolved, remain critical barriers that limit our understanding of the fundamental physiological processes that these membrane proteins regulate. This lack of knowledge also hinders development of new strategies to treat disorders associated with their mis-assembly. We propose a multi-disciplinary research program with specialized focus in structural biology and protein biophysics aimed to determine the structures and mechanisms of assembly these membrane proteins use to regulate tissue homeostasis. Our program has advanced integrative approaches, pioneered application of state-of-the-art techniques, and developed new tools specific to tight junction membrane proteins to achieve these goals. In the near term, our program will resolve the underlying molecular structures and biophysical principles governing the assembly of a subset of proteins from each of the three protein families. In the long term, the laboratory intends to provide complete high-resolution “pictures” of tight junction membrane proteins in functional assemblies. This research has potential to advance design and application of novel therapeutics to remedy tissue-specific ailments that are linked to disruptions in tight junction membrane protein assembly and ultrastructure.