Fig. 2.

Lipid import and trafficking by Giardia. The figure shows that BODIPY-ceramide, NBD-SM, and NBD-PG could be imported by actin-dependent endocytic pathways and targeted to ER/perinuclear membranes (steps 1–3) (Hernandez et al. 2008; Castillo et al. 2009). Membrane lipids and fatty acids like ceramide, SM, PC, and PalmA can also be taken up by a flippase-dependent, non-vesicular mechanism and migrated intracellularly. Lipid-binding proteins and microtubule filaments may participate in this process (steps 4–5). Membrane phospholipids like PC, which is mostly localised in the plasma membrane (Das et al. 2001), can be flipped back to the plasma membrane (step 6), although the mechanism of this outward movement is not known. It is possible that the internalised lipids are remodelled at the ER/perinuclear regions (step 7) and utilised by the parasite for the synthesis of membranes and organelles. SM, sphingomyelin; PG, phosphatidylglycerol; PalmA, palmitic acid; PC, phosphatidylcholine; MT, microtubule.