title: Activation of MK5/PRAK by the atypical MAP kinase ERK3 defines a novel signal transduction pathway.
abstract: 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.
authors.affiliation: Department of Pharmacology, Institute of Medical Biology, University of Tromsø, Tromsø, Norway. olems@fagmed.uit.no
authors.forename: Ole-Morten
authors.initials: OM
authors.lastname: Seternes
authors.forename: Theresa
authors.initials: T
authors.lastname: Mikalsen
authors.forename: Bjarne
authors.initials: B
authors.lastname: Johansen
authors.forename: Espen
authors.initials: E
authors.lastname: Michaelsen
authors.forename: Chris G
authors.initials: CG
authors.lastname: Armstrong
authors.forename: Nick A
authors.initials: NA
authors.lastname: Morrice
authors.forename: Benjamin
authors.initials: B
authors.lastname: Turgeon
authors.forename: Sylvain
authors.initials: S
authors.lastname: Meloche
authors.forename: Ugo
authors.initials: U
authors.lastname: Moens
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Keyse
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D018345:Mice, Knockout; D048053:Mitogen-Activated Protein Kinase 6 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D020798:Two-Hybrid System Techniques; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C111049:MAP-kinase-activated kinase 5; D017346:Protein Serine-Threonine Kinases; C474633:Mapk6 protein, mouse; D048053:Mitogen-Activated Protein Kinase 6; D048051:p38 Mitogen-Activated Protein Kinases