The lipid raft hypothesis revisited--new insights on raft composition and function from super-resolution fluorescence microscopy.

Recently developed super-resolution microscopy techniques are changing our understanding of lipid rafts and membrane organisation in general. The lipid raft hypothesis postulates that cholesterol can drive the formation of ordered domains within the plasma membrane of cells, which may serve as platforms for cell signalling and membrane trafficking. There is now a wealth of evidence for these domains. However, their study has hitherto been hampered by the resolution limit of optical microscopy, making the definition of their properties problematic and contentious. New microscopy techniques circumvent the resolution limit and, for the first time, allow the fluorescence imaging of structures on length scales below 200 nm. This review describes such techniques, particularly as applied to the study of membrane organisation, synthesising newly emerging facets of lipid raft biology into a state-of-the art model.