Monitoring receptor oligomerization by line-scan fluorescence cross-correlation spectroscopy.

Membrane-localized receptor proteins are involved in many signaling cascades, and diffusion and oligomerization are key processes controlling their activity. In order to study these processes in living cells, fluorescence fluctuation spectroscopy techniques have been developed that allow the quantification of concentration levels, diffusion rates, and interactions between fluorescently labeled receptor proteins at the nanomolar concentration level. This chapter presents a brief introduction to the technique and a protocol to measure and quantify the diffusion and oligomerization of human histamine1 receptor complexes in living HeLa cells using line-scanning fluorescence cross-correlation spectroscopy.