title: Regulation of mitogen-activated protein kinases by a calcium/calmodulin-dependent protein kinase cascade.
abstract: Membrane depolarization of NG108 cells gives rapid (< 5 min) activation of Ca2+/calmodulin-dependent protein kinase IV (CaM-KIV), as well as activation of c-Jun N-terminal kinase (JNK). To investigate whether the Ca2+-dependent activation of mitogen-activated protein kinases (ERK, JNK, and p38) might be mediated by the CaM kinase cascade, we have transfected PC12 cells, which lack CaM-KIV, with constitutively active mutants of CaM kinase kinase and/or CaM-KIV (CaM-KKc and CaM-KIVc, respectively). In the absence of depolarization, CaM-KKc transfection had no effect on Elk-dependent transcription of a luciferase reporter gene, whereas CaM-KIVc alone or in combination with CaM-KKc gave 7- to 10-fold and 60- to 80-fold stimulations, respectively, which were blocked by mitogen-activated protein (MAP) kinase phosphatase cotransfection. When epitope-tagged constructs of MAP kinases were co-transfected with CaM-KKc plus CaM-KIVc, the immunoprecipitated MAP kinases were activated 2-fold (ERK-2) and 7- to 10-fold (JNK-1 and p38). The JNK and p38 pathways were further investigated using specific c-Jun or ATF2-dependent transcriptional assays. We found that c-Jun/ATF2-dependent transcriptions were enhanced 7- to 10-fold by CaM-KIVc and 20- to 30-fold by CaM-KKc plus CaM-KIVc. In the case of the Jun-dependent transcription, this effect was not due to direct phosphorylation of c-Jun by activated CaM-KIV, since transcription was blocked by a dominant-negative JNK and by two MAP kinase phosphatases. Mutation of the phosphorylation site (Thr196) in CaM-KIV, which mediates its activation by CaM-KIV kinase, prevented activation of Elk-1, c-Jun, and ATF2 by the CaM kinase cascade. These results establish a new Ca2+-dependent mechanism for regulating MAP kinase pathways and resultant transcription.
authors.affiliation: Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
authors.forename: H
authors.initials: H
authors.lastname: Enslen
authors.forename: H
authors.initials: H
authors.lastname: Tokumitsu
authors.forename: P J
authors.initials: PJ
authors.lastname: Stork
authors.forename: R J
authors.initials: RJ
authors.lastname: Davis
authors.forename: T R
authors.initials: TR
authors.lastname: Soderling
mesh_terms: D051698:Activating Transcription Factor 2; D000818:Animals; D002118:Calcium / Q000502:physiology; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D016716:PC12 Cells; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D050807:ets-Domain Protein Elk-1; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; C497107:Atf2 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; C494114:Elk1 protein, rat; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; C517683:CAMK4 protein, human; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517686:Camk4 protein, rat; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium