Phospholipids Diffusion on the Surface of Model Lipid Droplets

Abstract

Lipid droplets (LD) are suborganelles localized in the membrane of the Endoplasmic Reticulum (ER) that play an important role in metabolic functions. They consist of a core of neutral lipids surrounded by a monolayer of phosphoplipids and proteins resembling to an oil-in-water emulsion droplet. Many studies have been focused on the biophysical properties of these LDs. However, despite numerous efforts, we are lacking information on the mobility of phospholipids on the surface of LDs surface, although they may play a key role in the protein distribution. In this article, we developed a microfluidic setup that allows the formation of a triolein-buffer interface decorated with a phospholipid monolayer. Using this setup, we measured the motility of phospholipid molecules by performing Fluorescent Recovery After Photobleaching (FRAP) experiments for different lipidic compositions. The results of the FRAP measurements reveal that the motility of phospholipids is controlled by the monolayer packing decorating the interface.

A comparison of lipid diffusive dynamics in monolayers and bilayers in the context of interleaflet coupling

“…Interestingly, the absolute lipid diffusion values in LDs are ca. 4 times smaller than those measured in air-water monolayers, as expected, due to the high viscosity of the surrounding media (i.e., water and oil vs. water and air) and as it was recently reported for DOPC and POPC oil-water monolayers 101 .…”

“…simple models that mimic each leaflet of a bilayer 100,101 . Previous works have reported Dm values for monolayers with few specific lipid compositions 43,44,[102][103][104] , however, systematic studies of Dm values as a function of sn-1 and sn-2 acyl chain structure are limited 102 . Here, monolayers were prepared with the same set of lipids as for GUV samples, using a previously described setup 42,43 .…”