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. 2013 Nov;195(3):871–881. doi: 10.1534/genetics.113.155192

Figure 10.

Figure 10

Model for lipid uptake at the fat body surface. Cortical lipid droplets (cLD) in the larval fat body are intimately associated with the plasma membrane in surface protuberances (top). We propose that this structure represents a lipid uptake apparatus that carries lipid cargo from extracellular lipophorin to the hydrophobic core of the cytoplasmic lipid dropet. The plasma membrane is uniformly lined with αβ-spectrin (red rectangles) and the surface of the small cortical lipid droplets is covered with the perilipin Lsd-2 (green). Since formation of cLD is dependent on the presence of both αβ-spectrin and Lsd-2, we suggest that these proteins are part of a stable complex that links lipid transport proteins in the plasma membrane to the cLD. Nascent lipid droplets are thought to arise from the ER membrane (bottom). We speculate that Lsd-2 on these lipid droplets directly or indirectly triggers initial association with spectrin on the plasma membrane and ultimately zips the two surfaces together into a tightly associated complex. LD growth may proceed until the lipid droplet reaches a size that causes dissociation of Lsd-2, allowing the lipid droplet to fall away from the plasma membrane and fuse with larger lipid droplets in the cytoplasm.