A curious case of cyclin-dependent kinases in neutrophils.

Neutrophils are terminally differentiated, short-lived white blood cells critical for innate immunity. Although cyclin-dependent kinases (CDKs) are typically related to cell cycle progression, increasing evidence has shown that they regulate essential functions of neutrophils. This review highlights the roles of CDKs and their partners, cyclins, in neutrophils, outside of cell cycle regulation. CDK1-10 and several cyclins are expressed in neutrophils, albeit at different levels. Observed phenotypes associated with specific inhibition or genetic loss of CDK2 indicate its role in modulating neutrophil migration. CDK4 and 6 regulate neutrophil extracellular traps (NETs) formation, while CDK5 regulates neutrophil degranulation. CDK7 and 9 are critical in neutrophil apoptosis, contributing to inflammation resolution. In addition to the CDKs that regulate mature neutrophil functions, cyclins are essential in hematopoiesis and granulopoiesis. The pivotal roles of CDKs in neutrophils present an untapped potential in targeting CDKs for treating neutrophil-dominant inflammatory diseases and understanding the regulation of the neutrophil life cycle.