title: Cycling of the signaling protein phospholipase D through cilia requires the BBSome only for the export phase.
abstract: The BBSome is a complex of seven proteins, including BBS4, that is cycled through cilia by intraflagellar transport (IFT). Previous work has shown that the membrane-associated signaling protein phospholipase D (PLD) accumulates abnormally in cilia of Chlamydomonas reinhardtii bbs mutants. Here we show that PLD is a component of wild-type cilia but is enriched ∼150-fold in bbs4 cilia; this accumulation occurs progressively over time and results in altered ciliary lipid composition. When wild-type BBSomes were introduced into bbs cells, PLD was rapidly removed from the mutant cilia, indicating the presence of an efficient BBSome-dependent mechanism for exporting ciliary PLD. This export requires retrograde IFT. Importantly, entry of PLD into cilia is BBSome and IFT independent. Therefore, the BBSome is required only for the export phase of a process that continuously cycles PLD through cilia. Another protein, carbonic anhydrase 6, is initially imported normally into bbs4 cilia but lost with time, suggesting that its loss is a secondary effect of BBSome deficiency.
authors.affiliation: Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA. lechtrek@uga.edu
authors.forename: Karl F
authors.initials: KF
authors.lastname: Lechtreck
authors.forename: Jason M
authors.initials: JM
authors.lastname: Brown
authors.forename: Julio L
authors.initials: JL
authors.lastname: Sampaio
authors.forename: Julie M
authors.initials: JM
authors.lastname: Craft
authors.forename: Andrej
authors.initials: A
authors.lastname: Shevchenko
authors.forename: James E
authors.initials: JE
authors.lastname: Evans
authors.forename: George B
authors.initials: GB
authors.lastname: Witman
mesh_terms: D002459:Cell Fusion; D016825:Chlamydomonas reinhardtii / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D002923:Cilia / Q000201:enzymology*; D004075:Diglycerides / Q000378:metabolism; D004705:Endocytosis; D005407:Flagella / Q000378:metabolism; D050356:Lipid Metabolism; D046912:Multiprotein Complexes / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010739:Phospholipase D / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D004075:Diglycerides; D046912:Multiprotein Complexes; D010940:Plant Proteins; D010739:Phospholipase D