p27Kip1 controls cytokinesis via the regulation of citron kinase activation
Murielle P. Serres, … , Nisar P. Malek, Arnaud Besson
Murielle P. Serres, … , Nisar P. Malek, Arnaud Besson
Published February 1, 2012
Citation Information: J Clin Invest. 2012;122(3):844-858. https://doi.org/10.1172/JCI60376.
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Research Article Oncology

p27Kip1 controls cytokinesis via the regulation of citron kinase activation

Abstract

p27Kip1 (p27) acts as a tumor suppressor by inhibiting cyclin–cyclin-dependent kinase (cyclin-CDK) activity. However, mice expressing a form of p27 that is unable to bind or inhibit cyclin-CDK complexes (p27CK–) have increased incidence of tumor development as compared with wild-type and p27–/– mice, revealing an oncogenic role for p27. Here, we identified a phenotype of multinucleation and polyploidy in p27CK– mice not present in p27–/– animals, suggesting a role for p27 in G2/M that is independent of cyclin-CDK regulation. Further analysis revealed that p27CK– expression caused a cytokinesis and abscission defect in mouse embryonic fibroblasts. We identified the Rho effector citron kinase (citron-K) as a p27-interacting protein in vitro and in vivo and found that p27 and citron-K colocalized at the contractile ring and mid-body during telophase and cytokinesis. Moreover, overexpression of the minimal p27-binding domain of citron-K was sufficient to rescue the phenotype caused by p27CK–. Conversely, expression of a mutant p27CK– unable to bind citron-K did not induce multinucleation. Finally, by binding to citron-K, p27 prevented the interaction of citron-K with its activator RhoA. Taken together, these data suggest a role for p27 during cytokinesis via the regulation of citron-K activity.

Authors

Murielle P. Serres, Uta Kossatz, Yong Chi, James M. Roberts, Nisar P. Malek, Arnaud Besson

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Figure 2

Multinucleation and centrosome amplification in p27CK– MEFs.

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Multinucleation and centrosome amplification in p27CK– MEFs. (A) Pri...
(A) Primary MEFs (passages 2–3) derived from p27+/+, p27–/–, and p27CK– mice were stained with anti–β-catenin and anti–lamin-A antibodies to visualize plasma membrane and nuclear envelope, respectively (original magnification, ×400). For each experiment, 500 cells were counted per genotype. The graph shows the mean of 3 independent experiments. Results were analyzed by 1-way ANOVA with the Tukey-Kramer multiple comparison test. p27+/+ versus p27CK–, ***P < 0.001. (B) The number of nuclei per cell was counted in two lines of immortalized MEFs per genotype. Cells were stained as in A, and 500 cells per line were counted (original magnification, ×400). The graph shows the average of 4 independent experiments. Statistical analyses were performed as in A. p27+/+ versus p27CK–, **P < 0.01. (C) Centrosomes were visualized by γ-tubulin staining and counted in 300 cells per genotype (original magnification, ×600). Graph shows the average of 2 different MEF lines per genotype in 4 independent experiments. Statistical analyses were performed as in A; p27+/+ versus p27CK–, ***P < 0.001. Error bars in A–C represent SEM.