title: Mammalian Pins is a conformational switch that links NuMA to heterotrimeric G proteins.
abstract: During asymmetric cell divisions, mitotic spindles align along the axis of polarization. In invertebrates, spindle positioning requires Pins or related proteins and a G protein alpha subunit. A mammalian Pins, called LGN, binds Galphai and also interacts through an N-terminal domain with the microtubule binding protein NuMA. During mitosis, LGN recruits NuMA to the cell cortex, while cortical association of LGN itself requires the C-terminal Galpha binding domain. Using a FRET biosensor, we find that LGN behaves as a conformational switch: in its closed state, the N and C termini interact, but NuMA or Galphai can disrupt this association, allowing LGN to interact simultaneously with both proteins, resulting in their cortical localization. Overexpression of Galphai or YFP-LGN causes a pronounced oscillation of metaphase spindles, and NuMA binding to LGN is required for these spindle movements. We propose that a related switch mechanism might operate in asymmetric cell divisions in the fly and nematode.
authors.affiliation: Center for Cell Signaling, Department of Microbiology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
authors.forename: Quansheng
authors.initials: Q
authors.lastname: Du
authors.forename: Ian G
authors.initials: IG
authors.lastname: Macara
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear; D002352:Carrier Proteins / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002460:Cell Line; D002461:Cell Line, Transformed; D016764:Cell Polarity; D002875:Chromosomes / Q000502:physiology; D004285:Dogs; D031541:Fluorescence Resonance Energy Transfer; D044385:GTP-Binding Protein alpha Subunits; D020962:Heterotrimeric GTP-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008870:Microtubules / Q000502:physiology; D008954:Models, Biological; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D008941:Spindle Apparatus / Q000502:physiology*; D014162:Transfection
chemical_list: D034961:Antigens, Nuclear; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C102754:GPSM2 protein, human; D044385:GTP-Binding Protein alpha Subunits; D047908:Intracellular Signaling Peptides and Proteins; C050045:NUMA1 protein, human; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D020962:Heterotrimeric GTP-Binding Proteins