Extracellular signal-regulated kinase 3 (ERK3) is an atypical mitogen-activated protein kinase (MAPK), which is regulated by protein stability. However, its function is unknown and no physiological substrates for ERK3 have yet been identified. Here we demonstrate a specific interaction between ERK3 and MAPK-activated protein kinase-5 (MK5). Binding results in nuclear exclusion of both ERK3 and MK5 and is accompanied by ERK3-dependent phosphorylation and activation of MK5 in vitro and in vivo. Endogenous MK5 activity is significantly reduced by siRNA-mediated knockdown of ERK3 and also in fibroblasts derived from ERK3-/- mice. Furthermore, increased levels of ERK3 protein detected during nerve growth factor-induced differentiation of PC12 cells are accompanied by an increase in MK5 activity. Conversely, MK5 depletion causes a dramatic reduction in endogenous ERK3 levels. Our data identify the first physiological protein substrate for ERK3 and suggest a functional link between these kinases in which MK5 is a downstream target of ERK3, while MK5 acts as a chaperone for ERK3. Our findings provide valuable tools to further dissect the regulation and biological roles of both ERK3 and MK5.
- Signal transduction
- Extracellular signal-regulated kinase 3 (ERK3)
- MAPK-activated protein kinase-5 (MK5)
Seternes, O-M., Mikalsen, T., Johansen, B., Michaelsen, E., Armstrong, C. G., Morrice, N. A., Turgeon, B., Meloche, S., Moens, U., & Keyse, S. M. (2004). Activation of MK5/PRAK by the atypical MAP kinase ERK3 defines a novel signal transduction pathway. The EMBO Journal, 23(24), 4780-4791. https://doi.org/10.1038/sj.emboj.7600489