title: Polyphosphoinositides are enriched in plant membrane rafts and form microdomains in the plasma membrane.
abstract: In this article, we analyzed the lipid composition of detergent-insoluble membranes (DIMs) purified from tobacco (Nicotiana tabacum) plasma membrane (PM), focusing on polyphosphoinositides, lipids known to be involved in various signal transduction events. Polyphosphoinositides were enriched in DIMs compared with whole PM, whereas all structural phospholipids were largely depleted from this fraction. Fatty acid composition analyses suggest that enrichment of polyphosphoinositides in DIMs is accompanied by their association with more saturated fatty acids. Using an immunogold-electron microscopy strategy, we were able to visualize domains of phosphatidylinositol 4,5-bisphosphate in the plane of the PM, with 60% of the epitope found in clusters of approximately 25 nm in diameter and 40% randomly distributed at the surface of the PM. Interestingly, the phosphatidylinositol 4,5-bisphosphate cluster formation was not significantly sensitive to sterol depletion induced by methyl-beta-cyclodextrin. Finally, we measured the activities of various enzymes of polyphosphoinositide metabolism in DIMs and PM and showed that these activities are present in the DIM fraction but not enriched. The putative role of plant membrane rafts as signaling membrane domains or membrane-docking platforms is discussed.
authors.affiliation: Laboratoire de Biogenèse Membranaire, UMR 5200, CNRS-Université Victor Segalen Bordeaux 2, 33076 Bordeaux, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Furt
authors.forename: Sabine
authors.initials: S
authors.lastname: König
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Bessoule
authors.forename: Françoise
authors.initials: F
authors.lastname: Sargueil
authors.forename: Rémi
authors.initials: R
authors.lastname: Zallot
authors.forename: Thomas
authors.initials: T
authors.lastname: Stanislas
authors.forename: Elodie
authors.initials: E
authors.lastname: Noirot
authors.forename: Jeanine
authors.initials: J
authors.lastname: Lherminier
authors.forename: Françoise
authors.initials: F
authors.lastname: Simon-Plas
authors.forename: Ingo
authors.initials: I
authors.lastname: Heilmann
authors.forename: Sébastien
authors.initials: S
authors.lastname: Mongrand
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*
chemical_list: D018129:Phosphatidylinositol Phosphates