Abstract
Coupling of spindle orientation to cellular polarity is a prerequisite for epithelial asymmetric cell divisions. The current view posits that the adaptor Inscuteable (Insc) bridges between Par3 and the spindle tethering machinery assembled on NuMALGNGαi(GDP), thus triggering apico-basal spindle orientation. The crystal structure of the Drosophila ortholog of LGN (known as Pins) in complex with Insc reveals a modular interface contributed by evolutionary conserved residues. The structure also identifies a positively charged patch of LGN binding to an invariant EPE-motif present on both Insc and NuMA. In vitro competition assays indicate that Insc competes with NuMA for LGN binding, displaying a higher affinity, and that it is capable of opening the LGN conformational switch. The finding that Insc and NuMA are mutually exclusive interactors of LGN challenges the established model of force generators assembly, which we revise on the basis of the newly discovered biochemical properties of the intervening components.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Antigens, Nuclear / genetics
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Antigens, Nuclear / metabolism
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Asymmetric Cell Division / physiology*
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Binding, Competitive / physiology
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Cell Cycle Proteins
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Cell Polarity / physiology
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Chickens
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Chromatography, Affinity
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Chromatography, Ion Exchange
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Crystallization
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Cytoskeletal Proteins / genetics*
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Cytoskeletal Proteins / metabolism
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Drosophila
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Drosophila Proteins / genetics*
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Drosophila Proteins / metabolism
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Electrophoresis, Polyacrylamide Gel
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Epithelial Cells / physiology*
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Fluorescence Polarization
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Guanine Nucleotide Dissociation Inhibitors / genetics*
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Guanine Nucleotide Dissociation Inhibitors / metabolism
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Humans
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Membrane Proteins / genetics*
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Membrane Proteins / metabolism
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Mice
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Models, Molecular*
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Molecular Sequence Data
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Nerve Tissue Proteins / genetics*
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Nerve Tissue Proteins / metabolism
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Nuclear Matrix-Associated Proteins / genetics
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Nuclear Matrix-Associated Proteins / metabolism
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Oryzias
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Protein Conformation
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Sequence Alignment
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Spindle Apparatus / physiology
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Static Electricity
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Xenopus laevis
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Zebrafish
Substances
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Antigens, Nuclear
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Cell Cycle Proteins
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Cytoskeletal Proteins
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Drosophila Proteins
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Guanine Nucleotide Dissociation Inhibitors
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Membrane Proteins
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Mud protein, Drosophila
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NUMA1 protein, human
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Nerve Tissue Proteins
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Nuclear Matrix-Associated Proteins
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Pins protein, Drosophila
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insc protein, Drosophila