Fluorescence correlation spectroscopy and photon counting histogram on membrane proteins: functional dynamics of the glycosylphosphatidylinositol-anchored urokinase plasminogen activator receptor

Abstract

The dynamic properties of a protein have a crucial role in determining what function a protein serves within the cell and how, when, and where it may physically interact with other proteins and macromolecules in response to extracellular stimuli. Glycosylphosphatidylinositol (GPI)–anchored proteins are particular membrane proteins linked to the membrane by a GPI tail. The oligomerization of GPI-anchored proteins is thought to regulate their association with membrane domains known as lipid rafts, their subcellular sorting, as well as their biological function.^{1, 2} However, the regulation of the oligomerization of GPI-anchored proteins and their molecular dynamics and confinement in microdomains has not been comprehensively explored in well-characterized model systems. These systems should imply the use of living cells in unperturbed conditions and in the absence of any artificial clustering agents such as chemical cross-linkers or antibodies³; they should exploit fluorescently tagged chimeras, which fully retain the biological activity of the wild-type proteins, and respond to physiological relevant macromolecular interactions.