Rac1-dependent recruitment of PAK2 to G₂ phase centrosomes and their roles in the regulation of mitotic entry

Abstract

During mitotic entry, the centrosomes provide a scaffold for initial activation of the CyclinB/Cdk1 complex, the mitotic kinase Aurora A, and the Aurora A-activating kinase p21-activated kinase (PAK). The activation of PAK at the centrosomes is yet regarded to happen independently of the Rho-GTPases Rac/Cdc42. In this study, Rac1 (but not RhoA or Cdc42) is presented to associate with the centrosomes from early G₂ phase until prometaphase in a cell cycle-dependent fashion, as evidenced by western blot analysis of prepared centrosomes and by immunolabeling. PAK associates with the G₂/M-phase centrosomes in a Rac1-dependent fashion. Furthermore, specific inhibition of Rac1 by C. difficile toxinB-catalyzed glucosylation or by knockout results in inhibited activation of PAK1/2, Aurora A, and the CyclinB/Cdk1 complex in late G₂ phase/prophase and delayed mitotic entry. Inhibition of PAK activation at late G₂-phase centrosomes caused by Rac1 inactivation coincides with impeded activation of Aurora A and the CyclinB/Cdk1 complex and delayed mitotic entry.

Keywords: :

• Rho
• C. difficile toxin B
• Cdc42
• Aurora
• CyclinB
• Cdk1
• mono-O-glucosylation

This article is referred to by:

Mitotic entry elucidated with bacterial toxin toolbox

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Funding

This work is supported by Deutsche Forschungsgemeinschaft Priority program 1150 to H.G. and K.R.