Mitogen-activated protein kinase-activated protein kinase 2 in neuroinflammation, heat shock protein 27 phosphorylation, and cell cycle: role and targeting.

Mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MAPKAPK-2 or MK2) is a downstream substrate of the p38 MAPK responsible for the signaling events influencing inflammation, cell division and differentiation, apoptosis, and cell motility in response to a wide range of extracellular stimuli. After the failure of p38 MAPK inhibitors in clinical trials, MK2 was unveiled as a potential target to regulate inflammatory cytokines' mRNA stability and translation. Recent work suggests that this mechanism may underlie the pathophysiology of brain disorders associated with inflammation. In addition, MK2 is a prominent kinase that phosphorylates heat shock protein 27 (Hsp27), an intensively investigated biomarker of cancer progression. This phosphorylation decreases the chaperone properties of Hsp27, making MK2 an endogenous inhibitor of Hsp27. MK2 is also one of the major players in the signal transduction pathways activated in response to DNA damage. Experimental evidence highlights the role of MK2 in G(2)/M and the mitotic spindle checkpoints, two mechanisms by which MK2 contributes to the maintenance of genomic stability. Thus, MK2 is considered a good molecular target to increase, in combination with chemotherapeutic agents, the sensitivity of treatment, especially in p53-mutated tumors. This review looks at the functions of MK2 in inflammation, Hsp27 regulation, and cell cycle checkpoint control with a focus on brain pathologies. Analysis of MK2 signaling in various disease models and a summary of the data on MK2 inhibitors suggest novel indications for MK2 inhibitors in addition to their mainstream use against peripheral inflammatory disorders.