Protein kinase C(mu) regulation of the JNK pathway is triggered via phosphoinositide-dependent kinase 1 and protein kinase C(epsilon).
The protein kinase C (PKC)-related enzyme PKC(mu)/PKD (protein kinase D) is activated by activation loop phosphorylation through PKC(eta). Here we demonstrate that PKC(mu) is activated by the direct phosphorylation of PKC(epsilon). PKC(mu) colocalizes with PKC(epsilon) in HEK293 and MCF7 cells as shown by confocal immunofluorescence analyses. PDK1, known as the upstream kinase for several PKC isozymes, associates intracellularly with PKC(epsilon) and PKC(eta). PKC(eta) is phosphorylated by PDK1 in vitro, leading to kinase activation as similarly reported for PKC(epsilon) activation by PDK1. Coexpression of PDK1, PKC(epsilon) and PKC(mu) in HEK293 cells results in PKC(mu) activation. In contrast, the coexpression of PDK1 and PKC(eta) with PKC(mu) does not activate PKC(eta) or consequently PKC(mu). PDK1/PKC(epsilon)-triggered activation of PKC(mu) inhibits JNK, a downstream effector of PKC(mu), whereas upon transient expression of PDK1, PKC(eta), and PKC(mu), JNK is not affected. These data implicate PKC(epsilon) as the biologically important upstream kinase for PKC(mu) in HEK293 cells, regulating downstream effectors. Our results further indicate a PDK1/PKC(eta)/PKC(mu) controlled negative regulation of PKC(eta) kinase activity. In this study, we show that differentially activated kinase cascades involving PDK1 and novel PKC isotypes are responsible for the regulation of PKC(mu) activity and consequently inhibit the JNK pathway.
Brändlin
Ilona
I
Fraunhofer Institute for Interfacial Engineering, Nobelstrabetae 12, 70569 Stuttgart, Germany.
Eiseler
Tim
T
Salowsky
Rüdiger
R
Johannes
Franz-Josef
FJ
D064413:3-Phosphoinositide-Dependent Protein Kinases; D004789:Enzyme Activation; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; C119190:protein kinase C nu; C089212:protein kinase D; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578562:PDPK1 protein, human; D017346:Protein Serine-Threonine Kinases; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases