Protein kinase C-associated kinase can activate NFkappaB in both a kinase-dependent and a kinase-independent manner.
Protein kinase C-associated kinase (PKK, also known as RIP4/DIK) activates NFkappaB when overexpressed in cell lines and is required for keratinocyte differentiation in vivo. However, very little is understood about the factors upstream of PKK or how PKK activates NFkappaB. Here we show that certain catalytically inactive mutants of PKK can activate NFkappaB, although to a lesser degree than wild type PKK. The deletion of specific domains of wild type PKK diminishes the ability of this enzyme to activate NFkappaB; the same deletions made on a catalytically inactive PKK background completely ablate NFkappaB activation. PKK may be phosphorylated by two specific mitogen-activated protein kinase kinase kinases, MEKK2 and MEKK3, and this interaction may in part be mediated through a critical activation loop residue, Thr184. Catalytically inactive PKK mutants that block phorbol ester-induced NFkappaB activation do not interfere with, but unexpectedly enhance, the activation of NFkappaB by these two mitogen-activated protein kinase kinase kinases. Taken together, these data indicate that PKK may function in both a kinase-dependent as well as a kinase-independent manner to activate NFkappaB.
Moran
Stewart T
ST
Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149, 13th Street, Charlestown, MA 02129, USA.
Haider
Khaleda
K
Ow
Yongkai
Y
Milton
Peter
P
Chen
Luojing
L
Pillai
Shiv
S
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002454:Cell Differentiation; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D017353:Gene Deletion; D005799:Genes, Dominant; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D048730:MAP Kinase Kinase Kinase 2; D048748:MAP Kinase Kinase Kinase 3; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013912:Threonine / Q000737:chemistry; D014162:Transfection; D014407:Tumor Cells, Cultured
D016328:NF-kappa B; D013912:Threonine; D008156:Luciferases; C417187:RIPK4 protein, human; D017346:Protein Serine-Threonine Kinases; D048730:MAP Kinase Kinase Kinase 2; D048748:MAP Kinase Kinase Kinase 3; D020930:MAP Kinase Kinase Kinases; C482618:MAP3K2 protein, human; C482625:MAP3K3 protein, human