Lipid Dynamics: A field of study that’s moving

Story contributed by Ken Jacobson (University of North Carolina, Chapel Hill)  and Ivan R. Nabi (University of British Colombia).

This Minisymposium focused on membrane domains and included discussions on caveolar and non-caveolar domains, invadopodia, lectins in dendritic cells, CD36 diffusion, and nanoscopic raft domains. 

• Ken Jacobson (University of North Carolina, Chapel Hill) introduced the session by describing the challenges of elucidating structure-function relationships in domains of varying protein-lipid composition, stressing the importance of lipid protein interactions.
• Ivan Nabi (University of British Colombia) demonstrated that non-caveolar caveolin-1 domains functionally regulate raft-dependent endocytosis of the ganglioside GM1, and also presented proteomics data defining the differential protein composition of caveolar and non-caveolar raft domains.
• Giuisi Caldieri’s (Consorzio Mario Negri Sud, Santa Maria Imbaro, Italy) talk addressed invadopodia, cholesterol-rich domains whose formation and ability to degrade the extracellular matrix depends on caveolin-1 regulation of cholesterol homeostasis in the plasma membrane. 
• Raman Deep Singh (Mayo Clinic, Rochester, MN) described how sialic acid residues of cell surface gangliosides support the structural integrity of caveolae and maintain caveolar endocytosis.
• Aaron Neumann (University of North Carolina, Chapel Hill) discussed properties of DC-SIGN, CD206 and dectin, transmembrane lectins that can be mulitiplexed within the same pathogen recognition domains in dendritic cells. These domains lead to the appearance of a novel protrusive structure, called a fungipod, when yeast particles are phagocytosed.
• Khuloud Jaqaman (The Scripps Research Institute, La Jolla, CA) presented single particle tracking studies of the CD36 receptor in macrophages (Jaqaman, K. et al., 2008). Accomplished within a field that contains many particles, analysis of CD36 movement demonstrated an unexpected, linearly constrained diffusion of this receptor. Channeled by the actin and microtubule cytoskeletons, movement of CD36 facilitates receptor oligomerization and enhances requisite downstream signaling upon ligand binding.
• Christian Eggling (Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany) elegantly demonstrated that sphingolipids and GPI-anchored proteins, but not phospholipids, are selectively trapped in cholesterol dependent nanodomains for around 10 ms using STED microscopy (Eggeling et al., 2008). These ‘raft’ domains are less than 30 nm in dimension—consistent with the concept that the elementary lipid raft is a dynamic nanoscale domain.