title: Galphai generates multiple Pins activation states to link cortical polarity and spindle orientation in Drosophila neuroblasts.
abstract: Drosophila neuroblasts divide asymmetrically by aligning their mitotic spindle with cortical cell polarity to generate distinct sibling cell types. Neuroblasts asymmetrically localize Galphai, Pins, and Mud proteins; Pins/Galphai direct cortical polarity, whereas Mud is required for spindle orientation. It is currently unknown how Galphai-Pins-Mud binding is regulated to link cortical polarity with spindle orientation. Here, we show that Pins forms a "closed" state via intramolecular GoLoco-tetratricopeptide repeat (TPR) interactions, which regulate Mud binding. Biochemical, genetic, and live imaging experiments show that Galphai binds to the first of three Pins GoLoco motifs to recruit Pins to the apical cortex without "opening" Pins or recruiting Mud. However, Galphai and Mud bind cooperatively to the Pins GoLocos 2/3 and tetratricopeptide repeat domains, respectively, thereby restricting Pins-Mud interaction to the apical cortex and fixing spindle orientation. We conclude that Pins has multiple activity states that generate cortical polarity and link it with mitotic spindle orientation.
authors.affiliation: Institute of Molecular Biology, Department of Chemistry, University of Oregon, Eugene, OR 97403, USA.
authors.forename: Rick W
authors.initials: RW
authors.lastname: Nipper
authors.forename: Karsten H
authors.initials: KH
authors.lastname: Siller
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Smith
authors.forename: Chris Q
authors.initials: CQ
authors.lastname: Doe
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Prehoda
mesh_terms: D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000378:metabolism*; D018797:Cell Cycle Proteins; D016764:Cell Polarity; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding; D008941:Spindle Apparatus / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D008565:Membrane Proteins; C411670:Mud protein, Drosophila; D009419:Nerve Tissue Proteins; C405164:Pins protein, Drosophila; D019206:GTP-Binding Protein alpha Subunits, Gi-Go