Membrane Heterogeneity Beyond the Plasma Membrane

Abstract

The structure and organization of cellular membranes have received intense interest, particularly in investigations of the raft hypothesis. The vast majority of these investigations have focused on the plasma membrane of mammalian cells, yielding significant progress in understanding membrane heterogeneity in terms of lipid composition, molecular structure, dynamic regulation, and functional relevance. In contrast, investigations on lipid organization in other membrane systems have been comparatively scarce, despite the likely relevance of membrane domains in these contexts. In this review, we summarize recent observations on lipid organization in organellar membranes, including endoplasmic reticulum, Golgi, endo-lysosomes, lipid droplets, and secreted membranes like lung surfactant, milk fat globule membranes, and viral membranes. Across these non-plasma membrane systems, it seems that the biophysical principles underlying lipid self-organization contribute to lateral domains.

Keywords: Golgi; endoplasmic reticulum; lipid raft; membrane domain; organelle.

FIGURE 1

Lipid domains are present on membrane systems, including not only the PM of mammalian cells but also many organellular membranes [endoplasmic reticulum (ER), Golgi, endosomes, lysosomes, lipid droplets (LDs)], viral membranes, and cell-secreted membrane structures like lung surfactants and milk fat globule membranes (MFGMs). Green color represents ordered domains (either liquid or solid). Other abbreviations: TGN, trans-Golgi network; TG, triglyceride; TMD, transmembrane domain; GPI-AP, GPI-anchored protein; FA, fatty acid.