The use of Light-Induced lo Domains in Giant Unilamellar Vesicles to Mimick raft Dynamics: Application to the Effect of the Ganglioside GM1

Abstract

Cholesterol and sphingolipid-enriched raft lipid domains play important roles in numerous cellular processes. Recently, giant unilamellar vesicles containing lo domains have become valuable tools for the modeling of raft properties. One topic which has been adressed is the dynamics of micrometer-sized lo domains formation in GUVs. This is usually done by varying the lipid composition and temperature. However, these slow procedures cannot reproduce the very dynamics of raft formation and size modulation in biomembranes, that can occur in subsecond timescales. Here, we propose a simple method which allows one to monitor the dynamics of lo domain formation in GUVs on a faster timescale. The method is derived from the initial observation by several authors of a photosensitizing effect of the fluorescent probes used for lo domain detection in GUVs, which promotes lipid oxidation. Such oxidized lipids are able as such to induce raft formation. It has been relevantly emphasized that such photooxidation may lead to artifacts. Here, we show that such oxidation-induced lo domain formation can also be purposely used, since it provides a way to trigger raft-type microdomain growth in GUVs on a faster timescale, relevant to cellular processes, and to study the effect of any parameter on such dynamics. We illustrate the usefulness of this approach by studying the effect of the ganglioside GM1, an essential component of cellular rafts. We show that GM1 has a profound influence on lo domain formation, dynamics and stability in GUVs, which may bear relevance to physiological situations.