Differences between the lateral organization of conventional and inositol phospholipid-anchored membrane proteins. A further definition of micrometer scale membrane domains.

Abstract

Abstract. Plasma membranes of many cells appear to be divided into domains, areas whose composition and function differ from the average for an entire membrane. We have previously used fluorescence photobleaching and recovery to demonstrate one type of membrane domain, with dimensions of micrometers (Yechiel, E., and M. Edidin. 1987. J. Cell Biol. 105: 755-760). The presence of membrane domains is inferred from the dependence of the apparent mobile fraction of labeled molecules on the size of the membrane area probed. We now find that by this definition classical class I MHC molecules, H-2D b, are concentrated in domains in the membranes of K78-2 hepatoma cells, while the nonclassical class I-related molecules, Qa-2, are free to pass the boundaries of these domains. The two proteins are highly homologous but differ in their mode of anchorage to the membrane lipid bilayer. H-2D b is anchored by a transmembrane peptide, while Qa-2 is anchored by a glycosylphosphatidylinositol (GPI) anchor. A mutant class I protein with its external portion derived from Qa-2 but with transmembrane and cytoplasmic sequences from a classical class I molecule shows a dependence of its mobile fraction on the area of membrane probed, while a mutant whose external portions are a mixture of classical and nonclassical class I sequences, GPI-linked to the bilayer, does not show this dependence and hence by our definition is not restricted to membrane domains.

What do diffusion measurements tell us about membrane compartmentalisation? Emergence of the role of interprotein interactions

“…The first indication of the presence of micrometer-sized domains was obtained by FRAP. Yechiel and Edidin found a decrease of the mobile fraction with increasing radius of the bleaching spot ( [7,8] and see "Appendix 1").…”

“…Such an approach was first developed by Yechiel and Edidin [7] and Edidin and Stroynowski [8] and has been applied in the analysis of dynamic compartmentalisation of the NK2, hMOR, CCR5 and CD4 receptors [88,89].…”

GPI-anchored protein organization and dynamics at the cell surface

“…However, measuring the diffusion properties across a range of observation areas provided more resolved understanding. In fact, FRAP studies had already exploited the scale-dependence of the mobile fraction and diffusion coeffi cient to infer on the size of membrane domains ( 59 ). Marguet and coworkers implemented this approach in FCS and developed a simulation-based approach to interpret the scale-dependence data.…”

Lateral diffusion of Toll-like receptors reveals that they are transiently confined within lipid rafts on the plasma membrane

“…Patches, corals or lateral domains in the plasma membrane were first identified as structures that hinder protein diffusion in the plasma membrane as detected by FRAP (Yechiel and Edidin, 1987;Edidin and Stoynowski, 1991;Pfeiffer et al, 2001). It is believed that the domains on the plasma membrane arise through the confinement of diffusible membrane proteins Journal of Cell Science 117 (17) The values are the mean±standard deviation from several determinations (f10).…”