title: Calcium-dependent regulation of Rab activation and vesicle fusion by an intracellular P2X ion channel.
abstract: Rab GTPases play key roles in the delivery, docking and fusion of intracellular vesicles. However, the mechanism by which spatial and temporal regulation of Rab GTPase activity is controlled is poorly understood. Here we describe a mechanism by which localized calcium release through a vesicular ion channel controls Rab GTPase activity. We show that activation of P2XA, an intracellular ion channel localized to the Dictyostelium discoideum contractile vacuole system, results in calcium efflux required for downregulation of Rab11a activity and efficient vacuole fusion. Vacuole fusion and Rab11a downregulation require the activity of CnrF, an EF-hand-containing Rab GAP found in a complex with Rab11a and P2XA. CnrF Rab GAP activity for Rab11a is enhanced by the presence of calcium and the EF-hand domain. These findings suggest that P2XA activation results in vacuolar calcium release, which triggers activation of CnrF Rab GAP activity and subsequent downregulation of Rab11a to allow vacuole fusion.
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: Katie
authors: K
authors: Parkinson
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: Abigail E
authors: AE
authors: Baines
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: Thomas
authors: T
authors: Keller
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: Nicole
authors: N
authors: Gruenheit
authors: Faculty of Medical and Human Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: Laricia
authors: L
authors: Bragg
authors: 1] Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK [2] Faculty of Medical and Human Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: R Alan
authors: RA
authors: North
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
authors: Christopher R L
authors: CR
authors: Thompson
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism*; D004023:Dictyostelium / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D020690:GTPase-Activating Proteins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D008561:Membrane Fusion / Q000187:drug effects; D008856:Microscopy, Fluorescence; D009154:Mutation / Q000235:genetics; D064587:Osmoregulation / Q000187:drug effects; D010641:Phenotype; D011485:Protein Binding / Q000187:drug effects; D015800:Protozoan Proteins / Q000378:metabolism; D058469:Receptors, Purinergic P2X / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D000255:Adenosine Triphosphate; D002118:Calcium; D020690:GTPase-Activating Proteins; D049452:Green Fluorescent Proteins; D015800:Protozoan Proteins; D058469:Receptors, Purinergic P2X; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins