Dynamic molecular confinement in the plasma membrane by microdomains and the cytoskeleton meshwork

Abstract

It is by now widely recognized that cell membranes show complex patterns of lateral organization. Two mechanisms involving either a lipid-dependent (microdomain model) or cytoskeleton-based (meshwork model) process are thought to be responsible for these plasma membrane organizations. In the present study, fluorescence correlation spectroscopy measurements on various spatial scales were performed in order to directly identify and characterize these two processes in live cells with a high temporal resolution, without any loss of spatial information. Putative raft markers were found to be dynamically compartmented within tens of milliseconds into small microdomains (+o120 nm) that are sensitive to the cholesterol and sphingomyelin levels, whereas actin-based cytoskeleton barriers are responsible for the confinement of the transferrin receptor protein. A free-like diffusion was observed when both the lipid-dependent and cytoskeleton-based organizations were disrupted, which suggests that these are two main compartmentalizing forces at work in the plasma membrane.

Lateral Diffusion of Gαs in the Plasma Membrane Is Decreased after Chronic but not Acute Antidepressant Treatment: Role of Lipid Raft and Non-Raft Membrane Microdomains

“…Other groups have shown through methyl-b-cyclodextrin treatment that cholesterol chelation restricts diffusion of a variety of raft and non-raft membrane-associated fluorescent proteins. Furthermore, they demonstrated diffusion better correlates with type of membrane anchor, rather than raft localization (Lenne et al, 2006). Our results are consistent with these, as FRAP measurements of integral membrane proteins GFP-b-AR and GFP-AC8 were significantly slower than peripheral membrane proteins GFP-Ga s and GFP-Ga i1 (Figures 4b and c).…”

“…The latter does not actually visualize protein clustering in microdomains, but instead measures protein diffusion over a larger area. The speed of diffusion, as measured by FRAP, is dependent on a number of factors, such as the size of the molecule in question, as well as such potentially limiting factors as protein-protein interaction, or interaction between protein and cytoskeleton (Lenne et al, 2006;Reits and Neefjes, 2001).…”

Fluorescence fluctuations analysis in nanoapertures: physical concepts and biological applications

“…It is important to mention that the t 0 value indicates a type of conWnement in terms of physical boundaries (impermeable obstacles, dynamic partitioning into discrete domains or free diVusion restricted by corrals), but not the biochemical nature of these impediments. This should be identiWed by appropriate pharmacologic treatments to further characterize the origin of the conWnement (see Lasserre et al 2008;Lenne et al 2006).…”

Characterizing anomalous diffusion in crowded polymer solutions and gels over five decades in time with variable-lengthscale fluorescence correlation spectroscopy

“…Many possible reasons have been advanced to explain deviations from simple Fickian diffusion in complex environments, notably temporary confinement 3,21,22 , molecular crowding 15,16,23,24 and reversible binding to traps 25,26 . Accordingly, numerous models have been proposed to describe anomalous diffusion processes (see Refs.…”