Targeting Mitogen-Activated Protein Kinase Phosphatase-1 (MKP-1): Structure-Based Design of MKP-1 Inhibitors and Upregulators

Mitogen-activated protein kinase phosphatases (MKPs) are dual specificity protein phosphatases (DUSPs) that dephosphorylate both phospho-tyrosine and phospho-threonine residues on mitogen-activated protein kinases (MAPKs). Because the MAPK family of signalling molecules (phospho-p38 MAPK, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)) play essential roles in cell signalling pathways that regulate cell growth and inflammation, controlling MAPK-mediated pathways is a therapeutically attractive strategy. While small molecule MAPK inhibitors have utility, in this review we will focus on exploring the potential of targeting the endogenous MAPK deactivator - MKP-1. Importantly, there is a strong justification for developing both inhibitors and upregulators of MKP-1 because of the diverse roles played by MAPKs in disease: for example, in cancer, MKP-1 inhibitors may prove beneficial, as MKP-1 is overexpressed and is considered responsible for the failure of JNK-driven apoptotic pathways induced by chemotherapeutics; conversely, in inflammatory diseases such as asthma and arthritis, MKP-1 reduces MAPKmediated signalling and developing novel ligands to upregulate MKP-1 levels would be a therapeutically attractive anti-inflammatory strategy. Thus, in this review we utilise MKP-1 homology modeling to highlight the structural features of MKP-1 inhibitors that permit potent and selective inhibition, and to provide insights into the structural requirements for selective MKP-1 upregulators.