MAPKAPK3

MAPKAPK3, originally named 3pK and now often MK3, is the closest paralog of MK2. It is activated by p38 mitogen-activated protein kinase and, like MK2, phosphorylates small heat shock proteins including HSP27, sharing considerable substrate overlap and partly compensating for MK2 loss, which explains the milder inflammatory phenotype of MK2-null mice relative to p38 deletion. MK3 shows more restricted expression than MK2, and unique reported substrates such as the basic helix-loop-helix transcription factor E47 suggest additional roles in myogenic differentiation. The enzyme thus illustrates partial functional redundancy combined with isoform-specific specialization within the p38-activated kinase branch.