Receptor-linked environment-sensitive probe monitors the local membrane environment surrounding the insulin receptor

Functional membrane proteins in the plasma membrane are suggested to have specific membrane environments that play important roles to maintain and regulate the function of proteins. However, the local membrane environments of membrane proteins remain largely unexplored due to the lack of techniques allowing to monitor them in living cells. We have developed a method to probe the local membrane environment surrounding a membrane protein in the plasma membrane by covalently tethering a solvatochromic, environment-sensitive dye, Nile red, to a membrane protein via a flexible linker. Our direct imaging reported on the spatio-temporal properties of membrane fluidity of the local environment surrounding the insulin receptor. The local environment was distinct from the average plasma membrane fluidity and was quite dynamic and heterogeneous. Upon addition of insulin, the local membrane environment surrounding the receptor increased in fluidity in an insulin receptor-kinase dependent manner. This new technology should allow researchers to examine changes in membrane properties caused by receptor activation and devise ways to address the role of these changes in physiological processes.