title: Cell-free transfer of phospholipids between the endoplasmic reticulum and the Golgi apparatus of leek seedlings.
abstract: The transfer of lipids between the endoplasmic reticulum and the Golgi apparatus was investigated in vitro using a cell-free system from leek seedlings. Lipids of the donor membranes (endoplasmic reticulum) were radiolabeled either by incubating leek seedlings with [1-14C]acetate or [3H]acetate. Acceptor membranes (Golgi apparatus) were unlabeled and immobilized on nitrocellulose strips. The assay measured the lipid transfer resulting from both an ATP-independent process and an ATP- and cytosol-dependent process. A significant ATP- and cytosol-dependent lipid transfer was observed only in the case of the endoplasmic reticulum as donor and the Golgi apparatus as acceptor. Lipids transferred in an ATP-dependent manner were chiefly phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. The stimulation of lipid transfer by ATP as compared to the ATP-independent process was +79% (PC), +123% (PS) and +69% (PE). On the other hand, PI was not transferred in an ATP-dependent manner (the stimulation by ATP was only 20%). This supports the theory that a sorting of phospholipids takes place in the donor membrane. Moreover, a formation of lysoPC was observed only in the presence of ATP (+330%). The ATP-dependent lipid transfer was inhibited by N-ethylmaleimide, indicating the involvement of cytosolic (but no phospholipid transfer proteins) or membrane proteins in the transfer process. The ATP-dependent transfer of lipids was also diminished at 12 degrees C showing the sensitivity to low temperatures of the transfer of lipids between the endoplasmic reticulum and the Golgi apparatus.
authors.affiliation: IBC-CNRS, Université Bordeaux II, France.
authors.forename: B
authors.initials: B
authors.lastname: Sturbois
authors.forename: P
authors.initials: P
authors.lastname: Moreau
authors.forename: L
authors.initials: L
authors.lastname: Maneta-Peyret
authors.forename: D J
authors.initials: DJ
authors.lastname: Morré
authors.forename: C
authors.initials: C
authors.lastname: Cassagne
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000490:Allium; D001692:Biological Transport; D001693:Biological Transport, Active; D002474:Cell-Free System; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*
chemical_list: D010743:Phospholipids; D000255:Adenosine Triphosphate