title: A direct and functional interaction between Go and Rab5 during G protein-coupled receptor signaling.
abstract: Rab5 is a small guanosine triphosphatase (GTPase) that regulates the early stages of endocytosis and is conserved in eukaryotes. Rab5 regulates the internalization of receptors and other membrane-associated signaling proteins. The function of Rab5 in these processes is considered relatively passive, so that the endocytic capacity of Rab5 is used during, for example, beta-arrestin-dependent internalization of G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors (GPCRs). Direct recruitment or activation of Rab5 by the components of these signaling pathways has not been reported. Here, we demonstrate an interaction of Drosophila Rab5 and an immediate transducer of GPCR signaling, the G protein G(o), in vitro and in vivo. Rab5 and G(o) bound to each other as purified proteins, as well as in fly extracts. In cellular assays, G(o) led to Rab5 activation and endosome fusion. We further showed that the G(o)-Rab5 interaction functioned in Drosophila planar cell polarity and Wingless signal transduction, pathways initiated by GPCRs of the Frizzled (Fz) family. Additionally, the recycling Rab GTPases Rab4 and Rab11 functioned in Fz- and G(o)-mediated signaling to favor planar cell polarity over canonical Wingless signaling. The interplay between heterotrimeric G proteins and Rab GTPases controlled receptor internalization, revealing a previously uncharacterized regulatory mechanism in GPCR signaling.
authors.affiliation: Department of Biology, University of Konstanz, Konstanz 78457, Germany. vladimir.katanaev@uni-konstanz.de
authors.forename: Vladimir
authors.initials: V
authors.lastname: Purvanov
authors.forename: Alexey
authors.initials: A
authors.lastname: Koval
authors.forename: Vladimir L
authors.initials: VL
authors.lastname: Katanaev
mesh_terms: D000818:Animals; D016764:Cell Polarity / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D029721:Drosophila Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043562:Receptors, G-Protein-Coupled; D051155:Wnt1 Protein; D020691:rab GTP-Binding Proteins; D020695:rab4 GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C074622:wg protein, Drosophila