title: Regulation of a mitogen-activated protein kinase kinase kinase, MLTK by PKN.
abstract: PKNalpha is a fatty acid- and Rho-activated serine/threonine protein kinase having a catalytic domain homologous to members of the protein kinase C family. Recently it was reported that PKNalpha is involved in the p38 mitogen-activated protein kinase (MAPK) signaling pathway. To date, however, how PKNalpha regulates the p38gamma MAPK signaling pathway is unclear. Here we demonstrate that PKNalpha efficiently phosphorylates MLTKalpha (MLK-like mitogen-activated protein triple kinase), which was recently identified as a MAPK kinase kinase (MAPKKK) for the p38 MAPK cascade. Phosphorylation of MLTKalpha by PKNalpha enhances its kinase activity in vitro. Expression of the kinase-negative mutant of PKNalpha inhibited the mobility shift of MLTKalpha caused by osmotic shock in SDS-PAGE. Furthermore, PKNalpha associates with each member of the p38gamma MAPK signaling pathway (p38gamma, MKK6, and MLTKalpha). These results suggest that PKNalpha functions as not only an upstream activator of MLTKalpha but also a putative scaffold protein for the p38gamma MAPK signaling pathway.
authors.affiliation: Biosignal Research Center and Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Gotoh
authors.forename: Takayuki
authors.initials: T
authors.lastname: Isagawa
authors.forename: Tamako
authors.initials: T
authors.lastname: Nishimura
authors.forename: Emiko
authors.initials: E
authors.lastname: Goyama
authors.forename: Hon-Song
authors.initials: HS
authors.lastname: Kim
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Mukai
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ono
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D048669:MAP Kinase Kinase 6; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: C061570:protein kinase N; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C428384:MLK-like mitogen-activated protein triple kinase; D048669:MAP Kinase Kinase 6; C482566:MAP2K6 protein, human; C482567:Map2k6 protein, mouse