PKC-zeta-associated CK2 participates in the turnover of free IkappaBalpha

J Mol Biol. 2000 Apr 14;297(5):1245-58. doi: 10.1006/jmbi.2000.3630.

Abstract

The atypical PKC isoenzymes, zeta and iota, activate NF-kappaB, a mechanism thought to mediate the anti-apoptotic and proliferative features of these kinases. PKC-zeta has been shown to be associated with an IkappaBalpha kinase in resting cells. In this study, we have sought to identify the PKC-zeta associated kinase and understand how PKC-zeta mediates basal IkappaBalpha turnover in vivo. We demonstrate that the PKC-zeta-associated IkappaBalpha kinase is CK2. This kinase, previously shown to phosphorylate the PEST domain of IkappaB molecules, co-precipitates with PKC-zeta in resting cells. In vitro, PKC-zeta interacts with CK2-beta. The in vivo PKC-zeta-associated CK2 preferentially phosphorylates S293 of IkappaBalpha as compared to non-associated CK2. The functional relevance of this observation is supported by the fact that the turnover of free IkappaBalpha in resting cells is S293-dependent. Moreover, overexpressing PKC-zeta results in lower steady-state protein levels of free IkappaBalpha, which is dependent on S293. Lastly, it is shown that PKC-zeta wt but not kinase dead leads to the in vitro phosphorylation of both CK2-alpha and beta. These studies demonstrate that the association between CK2 and PKC-zeta may play a major role in the control of the basal turnover of free IkappaBalpha, in the absence of extracellular stimuli.

MeSH terms

  • Animals
  • Casein Kinase II
  • Catalytic Domain
  • Cell Line
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Activation
  • Gene Expression Regulation
  • Genes, Reporter / genetics
  • Half-Life
  • Heparin / metabolism
  • Holoenzymes / chemistry
  • Holoenzymes / genetics
  • Holoenzymes / metabolism
  • Humans
  • I-kappa B Proteins*
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Mice
  • Molecular Weight
  • Mutation / genetics
  • NF-KappaB Inhibitor alpha
  • Phosphorylation
  • Phosphoserine / metabolism
  • Precipitin Tests
  • Protein Binding
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism*
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / chemistry
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Ribosomal Protein S6 Kinases / genetics
  • Ribosomal Protein S6 Kinases / metabolism
  • Transfection

Substances

  • DNA-Binding Proteins
  • Holoenzymes
  • I-kappa B Proteins
  • Isoenzymes
  • NFKBIA protein, human
  • Nfkbia protein, mouse
  • Recombinant Fusion Proteins
  • NF-KappaB Inhibitor alpha
  • Phosphoserine
  • Heparin
  • Casein Kinase II
  • Protein Serine-Threonine Kinases
  • Ribosomal Protein S6 Kinases
  • protein kinase C zeta
  • Protein Kinase C