title: Arabidopsis Rab-E GTPases exhibit a novel interaction with a plasma-membrane phosphatidylinositol-4-phosphate 5-kinase.
abstract: Rab GTPases of the Arabidopsis Rab-E subclass are related to mammalian Rab8 and are implicated in membrane trafficking from the Golgi to the plasma membrane. Using a yeast two-hybrid assay, Arabidopsis phosphatidylinositol-4-phosphate 5-kinase 2 (PtdIns(4)P 5-kinase 2; also known as PIP5K2), was shown to interact with all five members of the Rab-E subclass but not with other Rab subclasses residing at the Golgi or trans-Golgi network. Interactions in yeast and in vitro were strongest with RAB-E1d[Q74L] and weakest with the RAB-E1d[S29N] suggesting that PIP5K2 interacts with the GTP-bound form. PIP5K2 exhibited kinase activity towards phosphatidylinositol phosphates with a free 5-hydroxyl group, consistent with PtdIns(4)P 5-kinase activity and this activity was stimulated by Rab binding. Rab-E proteins interacted with PIP5K2 via its membrane occupancy and recognition nexus (MORN) domain which is missing from animal and fungal PtdIns(4)P 5-kinases. In plant cells, GFP:PIP5K2 accumulated at the plasma membrane and caused YFP:RAB-E1d to relocate there from its usual position at the Golgi. GFP:PIP5K2 was rapidly turned over by proteasomal activity in planta, and overexpression of YFP:PIP5K2 caused pleiotropic growth abnormalities in transgenic Arabidopsis. We propose that plant cells exhibit a novel interaction in which PIP5K2 binds GTP-bound Rab-E proteins, which may stimulate temporally or spatially localized PtdIns(4,5)P(2) production at the plasma membrane.
authors.affiliation: Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK.
authors.forename: Luísa
authors.initials: L
authors.lastname: Camacho
authors.forename: Andrei P
authors.initials: AP
authors.lastname: Smertenko
authors.forename: José
authors.initials: J
authors.lastname: Pérez-Gómez
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Hussey
authors.forename: Ian
authors.initials: I
authors.lastname: Moore
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology* / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D020691:rab GTP-Binding Proteins