p38 alpha/beta MAPK is well established as a promyogenic kinase, but the mechanism by which it is activated during differentiation is not well understood. CDO, JLP and p38 form a ternary complex and it is anticipated that in its role as a scaffold, JLP brings additional components of the pathway, such as MKKs, to these complexes and cooperate to activate p38 alpha/beta MAPK pathway. p38 is activated by phosphorylation on a canonical TxY motif by dual specificity kinases MKK6 and MKK3. MKK6 is the most abundant in skeletal muscles and displays minimal substrate selectivity among all p38 isoforms.