Monitoring Transmembrane and Peripheral Membrane Protein Interactions by Förster Resonance Energy Transfer Using Fluorescence Lifetime Imaging Microscopy

Caveolae are bulb-shaped invaginations of the plasma membrane that are enriched in specific lipids including cholesterol, phosphatidylserine and sphingolipids. Caveolae have many described cellular roles and functions, including endocytic transport, transcytosis, mechanosensing, and serving as a buffer against plasmalemmal stress. Caveola are formed through interactions between integral membrane proteins (Caveolin) and a cavin family of peripheral proteins (Cavins). Nearly half of the human proteome resides within or at the surface of membranes. Studying protein–protein interactions, especially of transmembrane domain containing proteins can be challenging. Fortunately, sophisticated biophysical methods allow for the monitoring of protein interactions in intact cells. Here, we describe the principles of Förster resonance energy transfer, fluorescence lifetime, and how their properties can be used to assess protein–protein interactions. Additionally, we discuss and demonstrate how fluorescence lifetime can be monitored microscopically thereby providing caveolin–cavin interaction data from living cells.