title: Flagellar membrane localization via association with lipid rafts.
abstract: The eukaryotic flagellar membrane has a distinct composition from other domains of the plasmalemma. Our work shows that the specialized composition of the trypanosome flagellar membrane reflects increased concentrations of sterols and saturated fatty acids, correlating with direct observation of high liquid order by laurdan fluorescence microscopy. These findings indicate that the trypanosome flagellar membrane possesses high concentrations of lipid rafts: discrete regions of lateral heterogeneity in plasma membranes that serve to sequester and organize specialized protein complexes. Consistent with this, a dually acylated Ca(2+) sensor that is concentrated in the flagellum is found in detergent-resistant membranes and mislocalizes if the lipid rafts are disrupted. Detergent-extracted cells have discrete membrane patches localized on the surface of the flagellar axoneme, suggestive of intraflagellar transport particles. Together, these results provide biophysical and biochemical evidence to indicate that lipid rafts are enriched in the trypanosome flagellar membrane, providing a unique mechanism for flagellar protein localization and illustrating a novel means by which specialized cellular functions may be partitioned to discrete membrane domains.
authors.affiliation: BioMedical Research Centre, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Tyler
authors.forename: Alina
authors.initials: A
authors.lastname: Fridberg
authors.forename: Krista M
authors.initials: KM
authors.lastname: Toriello
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Olson
authors.forename: John A
authors.initials: JA
authors.lastname: Cieslak
authors.forename: Theodore L
authors.initials: TL
authors.lastname: Hazlett
authors.forename: David M
authors.initials: DM
authors.lastname: Engman
mesh_terms: D000818:Animals; D054468:Axoneme / Q000187:drug effects / Q000648:ultrastructure; D002135:Calcium-Binding Proteins / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D005407:Flagella / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000187:drug effects; D015800:Protozoan Proteins / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002135:Calcium-Binding Proteins; D003902:Detergents; D015800:Protozoan Proteins; C061478:flagellar calcium-binding protein, Trypanosoma cruzi