Activation of Aurora-A Kinase by Protein Partner Binding and Phosphorylation Are Independent and Synergistic

Abstract

Background: Phosphorylation and TPX2 act together to stabilize the active conformation of Aurora-A. Results: TPX2 activates unphosphorylated Aurora-A, although phosphorylation makes a 2-fold greater energetic contribution to catalysis than TPX2. Conclusion: Either activator partially stabilizes the active conformation and stimulates kinase activity. Significance: Our revised model of kinase activation and mechanistic analysis might be applicable to other kinases.

Dynamic Equilibrium of the Aurora A Kinase Activation Loop Revealed by Single‐Molecule Spectroscopy

“…The relative areas of the peaks indicate that in solution the majority of molecules adopt an active T‐loop conformation and a minority an inactive conformation (Table 1). This is consistent with the active T‐loop conformation observed in X‐ray structures of uninhibited kinase and with the high catalytic activity of phosphorylated Aurora A 4b. Contrary to the model of a locked phosphorylated T‐loop, our data indicate that the activation loop of phosphorylated Aurora A exists in a dynamic structural equilibrium ( K eq =0.3±0.1).…”

“…To determine whether this result represents a mixture of binary Aurora A–MLN8054 and Aurora A–TPX2 complexes or population of an Aurora A–TPX2–MLN8054 triple complex, we calculated the expected experimental result for the mixture of binary complexes based on the published affinities of the two ligands4b, 5b (see the Supporting Information). A mixture of binary complexes would result in an inactive T‐loop population of 43 %, which is inconsistent with the experimental result (15 %; Table 1).…”

Spatial regulation of Aurora A activity during mitotic spindle assembly requires RHAMM to correctly localize TPX2

“…21,22,33 TPX2 is the most prominent coactivator of Aurora A during mitosis. 13,14,23 Thus, the regulation of spatial availability of TPX2 determines local Aurora A activity and promotes mitotic spindle assembly. Here, we identify RHAMM as a new and central regulator for Aurora A activity through the modulation of TPX2 abundance and localization.…”

“…6,10 TPX2 is also a co-factor for Aurora A and is both sufficient to activate the kinase above basal levels and necessary for optimal kinase activity. 13,14 As 40-60% of TPX2 is in a complex with RHAMM in human mitotic cells, 7 a regulatory relationship between RHAMM and Aurora A activity has been postulated 10,11,15 but not yet been demonstrated. Aurora A promotes microtubule assembly by targeting its substrates to sites of assembly [2][3][4][5]16,17 and by protecting these substrates from proteolytic degradation.…”

Haspin kinase regulates microtubule-organizing center clustering and stability through Aurora kinase C in mouse oocytes

“…In somatic cells (Ma et al, 2011), upon binding a microtubule-binding protein called TPX2, AURKA auto-activates and regulates the building of the bipolar spindle by recruiting other PCM proteins, promoting microtubule nucleation and anti-parallel sliding forces, and maintaining the integrity of astral microtubules with the cortex (Dodson and Bayliss, 2012;Giubettini et al, 2011;Kufer et al, 2002;Li et al, 2008;Scrofani et al, 2015). In mouse oocytes, overexpression of AURKA increases MTOC numbers prematurely (Saskova et al, 2008;Solc et al, 2012), and its depletion causes disorganized meiosis I spindles (Saskova et al, 2008).…”