Cyclin-Dependent Kinase (CDK) Inhibitors

Hoodless, Laura J., Robb, Calum T., Felton, Jennifer M., Tucker, Carl S., Rossi, Adriano G., Laura J. Hoodless, Calum T. Robb, Jennifer M. Felton, Carl S. Tucker, Adriano G. Rossi

Cyclin-dependent kinases (CDKs) have been traditionally associated with the cell cycle. However, it is now known that CDK7 and CDK9 regulate transcriptional activity via phosphorylation of RNA polymerase II and subsequent synthesis of, for example, inflammatory mediators and factors that influence the apoptotic process; including apoptosis of granulocytes such as neutrophils and eosinophils. Successful resolution of inflammation and restoration of normal tissue homeostasis requires apoptosis of these inflammatory cells and subsequent clearance of apoptotic bodies by phagocytes such as macrophages. It is believed that CDK7 and CDK9 influence resolution of inflammation since they are involved in the transcription of anti-apoptotic proteins such as Mcl-1 which is especially important in granulocyte survival.This chapter describes various in vitro and in vivo models used to investigate CDKs and their inhibitors in granulocytes and particularly the role of CDKs in the apoptosis pathway. This can be performed in vitro by isolation and use of primary granulocytes and in vivo using animal models of inflammatory disease in rodents and zebrafish. Some of the methods described here to assess the role of CDKs in inflammation and apoptosis include flow cytometry and western blotting, together with imaging and quantification of apoptosis in fixed tissue, as well as in vivo models of inflammation.