title: Regulation of MAPK-activated protein kinase 5 activity and subcellular localization by the atypical MAPK ERK4/MAPK4.
abstract: MAPK-activated protein kinase 5 (MK5) was recently identified as a physiological substrate of the atypical MAPK ERK3. Complex formation between ERK3 and MK5 results in phosphorylation and activation of MK5, concomitant stabilization of ERK3, and the nuclear exclusion of both proteins. However, ablation of ERK3 in HeLa cells using small interfering RNA or in fibroblasts derived from ERK3 null mice reduces the activity of endogenous MK5 by only 50%, suggesting additional mechanisms of MK5 regulation. Here we identify the ERK3-related kinase ERK4 as a bona fide interaction partner of MK5. Binding of ERK4 to MK5 is accompanied by phosphorylation and activation of MK5. Furthermore, complex formation also results in the relocalization of MK5 from nucleus to cytoplasm. However unlike ERK3, ERK4 is a stable protein, and its half-life is not modified by the presence or absence of MK5. Finally, although knock-down of ERK4 protein in HeLa cells reduces endogenous MK5 activity by approximately 50%, a combination of small interfering RNAs targeting both ERK4 and ERK3 causes a further reduction in the MK5 activity by more than 80%. We conclude that MK5 activation is dependent on both ERK3 and ERK4 in these cells and that these atypical MAPKs are both physiological regulators of MK5 activity.
authors.affiliation: Department of Pharmacology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway, and Cancer Research UK Stress Response Laboratory, Biomedical Research Centre, Ninewells Hospital and Medical School, Dundee, UK.
authors.forename: Espen
authors.initials: E
authors.lastname: Aberg
authors.forename: Maria
authors.initials: M
authors.lastname: Perander
authors.forename: Bjarne
authors.initials: B
authors.lastname: Johansen
authors.forename: Catherine
authors.initials: C
authors.lastname: Julien
authors.forename: Sylvain
authors.initials: S
authors.lastname: Meloche
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Keyse
authors.forename: Ole-Morten
authors.initials: OM
authors.lastname: Seternes
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000595:Amino Acid Sequence; D001483:Base Sequence; D003593:Cytoplasm / Q000201:enzymology; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C111049:MAP-kinase-activated kinase 5; D017346:Protein Serine-Threonine Kinases; D020929:Mitogen-Activated Protein Kinase Kinases