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Journal of Biomedicine and Biotechnology
Volume 2009 (2009), Article ID 805709, 11 pages
Research Article

Activation of Cyclin-Dependent Kinase 5 Is a Consequence of Cell Death

1Department of Biology, Queens College and Graduate Center of the City University of New York, Flushing, NY 11367, USA
2Department of Technology and Health, Higher Institute for Health, 00161 Rome, Italy
3Department of Drug Research and Evaluation, Highest Institute for Health, 00161 Rome, Italy
4Department of Biological Sciences, St. John's University, Jamaica, NY 11439, USA

Received 28 April 2009; Revised 20 June 2009; Accepted 14 July 2009

Academic Editor: Mauro Piacentini

Copyright © 2009 Yixia Ye et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Cyclin-dependent kinase 5 (Cdk5) is similar to other Cdks but is activated during cell differentiation and cell death rather than cell division. Since activation of Cdk5 has been reported in many situations leading to cell death, we attempted to determine if it was required for any form of cell death. We found that Cdk5 is activated during apoptotic deaths and that the activation can be detected even when the cells continue to secondary necrosis. This activation can occur in the absence of Bim, calpain, or neutral cathepsins. The kinase is typically activated by p25, derived from p35 by calpain-mediated cleavage, but inhibition of calpain does not affect cell death or the activation of Cdk5. Likewise, RNAi-forced suppression of the synthesis of Cdk5 does not affect the incidence or kinetics of cell death. We conclude that Cdk5 is activated as a consequence of metabolic changes that are common to many forms of cell death. Thus its activation suggests processes during cell death that will be interesting or important to understand, but activation of Cdk5 is not necessary for cells to die.