title: Drosophila Ric-8 regulates Galphai cortical localization to promote Galphai-dependent planar orientation of the mitotic spindle during asymmetric cell division.
abstract: Localization and activation of heterotrimeric G proteins have a crucial role during asymmetric cell division. The asymmetric division of the Drosophila sensory precursor cell (pl) is polarized along the antero-posterior axis by Frizzled signalling and, during this division, activation of Galphai depends on Partner of Inscuteable (Pins). We establish here that Ric-8, which belongs to a family of guanine nucleotide-exchange factors for Galphai, regulates cortical localization of the subunits Galphai and Gbeta13F. Ric-8, Galphai and Pins are not necessary for the control of the anteroposterior orientation of the mitotic spindle during pl cell division downstream of Frizzled signalling, but they are required for maintainance of the spindle within the plane of the epithelium. On the contrary, Frizzled signalling orients the spindle along the antero-posterior axis but also tilts it along the apico-basal axis. Thus, Frizzled and heterotrimeric G-protein signalling act in opposition to ensure that the spindle aligns both in the plane of the epithelium and along the tissue polarity axis.
authors.affiliation: Institute Curie, CNRS UMR 144, 26 rue d'Ulm, Paris 75248, France. nicolas.david@curie.fr
authors.forename: Nicolas B
authors.initials: NB
authors.lastname: David
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Martin
authors.forename: Marion
authors.initials: M
authors.lastname: Segalen
authors.forename: François
authors.initials: F
authors.lastname: Rosenfeld
authors.forename: François
authors.initials: F
authors.lastname: Schweisguth
authors.forename: Yohanns
authors.initials: Y
authors.lastname: Bellaïche
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism / Q000502:physiology; D051157:Frizzled Receptors / Q000502:physiology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000502:physiology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D008941:Spindle Apparatus / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000502:physiology
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D051157:Frizzled Receptors; D044387:GTP-Binding Protein beta Subunits; D020662:Guanine Nucleotide Exchange Factors; D016212:Transforming Growth Factor beta; C089440:gbb protein, Drosophila; C507319:ric8a protein, Drosophila; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go