A novel mechanism for activation of the protein kinase Aurora A

Curr Biol. 2003 Apr 15;13(8):691-7. doi: 10.1016/s0960-9822(03)00166-0.

Abstract

Segregation of chromosomes during mitosis requires interplay between several classes of protein on the spindle, including protein kinases, protein phosphatases, and microtubule binding motor proteins [1-4]. Aurora A is an oncogenic cell cycle-regulated protein kinase that is subject to phosphorylation-dependent activation [5-11]. Aurora A localization to the mitotic spindle depends on the motor binding protein TPX2 (Targeting Protein for Xenopus kinesin-like protein 2), but the protein(s) involved in Aurora A activation are unknown [11-13]. Here, we purify an activator of Aurora A from Xenopus eggs and identify it as TPX2. Remarkably, Aurora A that has been fully deactivated by Protein Phosphatase 2A (PP2A) becomes phosphorylated and reactivated by recombinant TPX2 in an ATP-dependent manner. Increased phosphorylation and activation of Aurora A requires its own kinase activity, suggesting that TPX2 stimulates autophosphorylation and autoactivation of the enzyme. Consistently, wild-type Aurora A, but not a kinase inactive mutant, becomes autophosphorylated on the regulatory T loop residue (Thr 295) after TPX2 treatment. Active Aurora A from bacteria is further activated at least 7-fold by recombinant TPX2, and TPX2 also impairs the ability of protein phosphatases to inactivate Aurora A in vitro. This concerted mechanism of stimulation of activation and inhibition of deactivation implies that TPX2 is the likely regulator of Aurora A activity at the mitotic spindle and may explain why loss of TPX2 in model systems perturbs spindle assembly [14-16]. Our finding that a known binding protein, and not a conventional protein kinase, is the relevant activator for Aurora A suggests a biochemical model in which the dynamic localization of TPX2 on mitotic structures directly modulates the activity of Aurora A for spindle assembly.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aurora Kinases
  • Autoradiography
  • Cell Cycle Proteins*
  • Chromosome Segregation / physiology
  • Enzyme Reactivators / metabolism*
  • Microtubule-Associated Proteins / isolation & purification
  • Microtubule-Associated Proteins / metabolism*
  • Mitosis / physiology*
  • Neoplasm Proteins*
  • Nuclear Proteins*
  • Phosphoproteins*
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases
  • Spindle Apparatus / physiology*
  • Xenopus
  • Xenopus Proteins*

Substances

  • Cell Cycle Proteins
  • Enzyme Reactivators
  • Microtubule-Associated Proteins
  • Neoplasm Proteins
  • Nuclear Proteins
  • Phosphoproteins
  • TPX2 protein, Xenopus
  • Xenopus Proteins
  • Protein Kinases
  • AURKA protein, Xenopus
  • Aurora Kinases
  • Protein-Serine-Threonine Kinases