New Therapeutic Targets in Cardiology

The p38 mitogen-activated protein kinases (p38s) are members of a key signaling pathway that responds to varied stresses, including those that contribute to heart failure. This review will focus on the ways in which p38 can be manipulated based on its mechanisms of activation and structure and how this knowledge has led to current cardiovascular clinical trials.Phosphorylation is the process through which extracellular signals are communicated to the interior of the cell and it is catalyzed by kinases. The protein kinases transfer the terminal phosphate group from ATP to the hydroxyl group of a serine, threonine, or tyrosine residue. This posttranslational modification can transform the function of the substrate protein by changing its binding partners, subcellular location, stability, and/or activity. In turn, these transformations have an impact on diverse fundamental cellular processes to alter transcription, translation, metabolism, contractility, growth, death, and/or differentiation. The 518 known protein kinases occupy a relatively high proportion (1.7%) of the human proteome of which an even higher proportion (≈30%) is modified by phosphorylation.1The dysregulation of kinases is a common feature of many cancers, because growth signals can be inappropriately amplified by mutations that render kinases constitutively active. Consequently, drugs to inhibit kinases are the most successful and rapidly growing of the recent advances in cancer therapy. This success has occurred despite initial concerns of the constraints imposed by the high degree of homology between the ATP binding sites of different protein kinases and of the need to compete with millimolar concentrations of ATP. Initial success was achieved with imatinib (Gleevec) that targets an abnormal fusion protein kinase formed in the translocation event that creates the Philadelphia Chromosome in chronic myeloid leukemia.2 Another early success was the targeting of the human epidermal growth factor receptor 2 tyrosine kinase that is abnormally active …