title: RasGAP mediates neuronal survival in Drosophila through direct regulation of Rab5-dependent endocytosis.
abstract: The GTPase Ras can either promote or inhibit cell survival. Inactivating mutations in Drosophila RasGAP (encoded by vap), a Ras GTPase-activating protein, lead to age-related brain degeneration. Genetic interactions implicate the epidermal growth factor receptor (EGFR)-Ras pathway in promoting neurodegeneration but the mechanism is not known. Here, we show that the Src homology 2 (SH2) domains of RasGAP are essential for its neuroprotective function. By using affinity purification and mass spectrometry, we identify a complex containing RasGAP together with Sprint, which is a Ras effector and putative activator of the endocytic GTPase Rab5. Formation of the RasGAP-Sprint complex requires the SH2 domains of RasGAP and tyrosine phosphorylation of Sprint. RasGAP and Sprint colocalize with Rab5-positive early endosomes but not with Rab7-positive late endosomes. We demonstrate a key role for this interaction in neurodegeneration: mutation of Sprint (or Rab5) suppresses neuronal cell death caused by the loss of RasGAP. These results indicate that the long-term survival of adult neurons in Drosophila is crucially dependent on the activities of two GTPases, Ras and Rab5, regulated by the interplay of RasGAP and Sprint.
authors.affiliation: The Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
authors.forename: Behzad
authors.initials: B
authors.lastname: Rowshanravan
authors.affiliation: The Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Woodcock
authors.affiliation: Lehrstuhl für Entwicklungsbiologie, Universität Regensburg, 93040 Regensburg, Germany.
authors.forename: José A
authors.initials: JA
authors.lastname: Botella
authors.affiliation: Research Unit Comparative Medicine, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Kiermayer
authors.affiliation: Lehrstuhl für Entwicklungsbiologie, Universität Regensburg, 93040 Regensburg, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Schneuwly
authors.affiliation: The Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK david.a.hughes@manchester.ac.uk.
authors.forename: David A
authors.initials: DA
authors.lastname: Hughes
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D005260:Female; D008297:Male; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins / Q000378:metabolism*
chemical_list: D020703:ras GTPase-Activating Proteins; D020696:rab5 GTP-Binding Proteins
keywords: Drosophila; Guanine-nucleotide-exchange factor; Rab5; RasGAP; Sprint; Tyrosine phosphorylation; Vap