The parasite Trypanosoma brucei has a single polarised flagellum that drives cellular motility. Some plasma-membrane-associated proteins localise specifically to the flagellum, but what are the mechanisms responsible for their targeting and retention? On , David Engman and colleagues propose a role for lipid rafts – which are detergent-resistant, highly ordered plasma-membrane microdomains – in targeting flagellar proteins. The authors first show that several molecules that are thought to be raft components are enriched in the flagellum. In addition, they use laurdan (an amphiphilic fluor) to show that the flagellar membrane possesses increased liquid order; together, these data indicate that flagella are enriched in lipid rafts. The authors next show that the flagellar calcium-sensing protein calflagin Tb24 concentrates in detergent-resistant membranes; in an accompanying paper (), the group shows that calflagin Tb24 must be palmitoylated to localise to flagella, and identifies the specific palmitoyl acyltransferase that modifies it. Importantly, calflagin Tb24 redistributes to other domains when lipid rafts are destabilised. Thus, association with lipid rafts directs the flagellar localisation of calflagin Tb24 and might, the authors propose, be a general mechanism for the trafficking of specific proteins to the membrane of flagella and cilia.
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