The Centrosome Is a Selective Condensate That Nucleates Microtubules by Concentrating Tubulin

Cell. 2017 Jun 1;169(6):1066-1077.e10. doi: 10.1016/j.cell.2017.05.028.

Abstract

Centrosomes are non-membrane-bound compartments that nucleate microtubule arrays. They consist of nanometer-scale centrioles surrounded by a micron-scale, dynamic assembly of protein called the pericentriolar material (PCM). To study how PCM forms a spherical compartment that nucleates microtubules, we reconstituted PCM-dependent microtubule nucleation in vitro using recombinant C. elegans proteins. We found that macromolecular crowding drives assembly of the key PCM scaffold protein SPD-5 into spherical condensates that morphologically and dynamically resemble in vivo PCM. These SPD-5 condensates recruited the microtubule polymerase ZYG-9 (XMAP215 homolog) and the microtubule-stabilizing protein TPXL-1 (TPX2 homolog). Together, these three proteins concentrated tubulin ∼4-fold over background, which was sufficient to reconstitute nucleation of microtubule asters in vitro. Our results suggest that in vivo PCM is a selective phase that organizes microtubule arrays through localized concentration of tubulin by microtubule effector proteins.

Keywords: Centrosome; Polo Kinase; SPD-5; TPX2; XMAP215; microtubule-organizing center; pericentriolar material; phase separation; scaffold.

MeSH terms

  • Animals
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / metabolism*
  • Carrier Proteins / metabolism
  • Cell Cycle Proteins / metabolism*
  • Centrosome / chemistry*
  • Centrosome / metabolism
  • Microtubules / metabolism*
  • Protein-Serine-Threonine Kinases / metabolism
  • Tubulin / metabolism*

Substances

  • Caenorhabditis elegans Proteins
  • Carrier Proteins
  • Cell Cycle Proteins
  • SPD-2 protein, C elegans
  • SPD-5 protein, C elegans
  • TPXL-1 protein, C elegans
  • Tubulin
  • ZYG-9 protein, C elegans
  • Protein-Serine-Threonine Kinases
  • plk-1 protein, C elegans