PKC gamma mutations in spinocerebellar ataxia type 14 affect C1 domain accessibility and kinase activity leading to aberrant MAPK signaling

J Cell Sci. 2008 Jul 15;121(Pt 14):2339-49. doi: 10.1242/jcs.027698. Epub 2008 Jun 24.


Spinocerebellar ataxia type 14 (SCA14) is a neurodegenerative disorder caused by mutations in the neuronal-specific protein kinase C gamma (PKCgamma) gene. Since most mutations causing SCA14 are located in the PKCgamma C1B regulatory subdomain, we investigated the impact of three C1B mutations on the intracellular kinetics, protein conformation and kinase activity of PKCgamma in living cells. SCA14 mutant PKCgamma proteins showed enhanced phorbol-ester-induced kinetics when compared with wild-type PKCgamma. The mutations led to a decrease in intramolecular FRET of PKCgamma, suggesting that they ;open' PKCgamma protein conformation leading to unmasking of the phorbol ester binding site in the C1 domain. Surprisingly, SCA14 mutant PKCgamma showed reduced kinase activity as measured by phosphorylation of PKC reporter MyrPalm-CKAR, as well as downstream components of the MAPK signaling pathway. Together, these results show that SCA14 mutations located in the C1B subdomain ;open' PKCgamma protein conformation leading to increased C1 domain accessibility, but inefficient activation of downstream signaling pathways.

MeSH terms

  • Amino Acid Sequence
  • Cell Membrane / drug effects
  • Cell Membrane / enzymology
  • Cell Nucleus / drug effects
  • Cell Nucleus / enzymology
  • Cell Survival / drug effects
  • Enzyme Activation / drug effects
  • HeLa Cells
  • Humans
  • Kinetics
  • MAP Kinase Signaling System* / drug effects
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Molecular Sequence Data
  • Mutation / genetics*
  • Protein Kinase C / chemistry*
  • Protein Kinase C / genetics*
  • Protein Structure, Tertiary
  • Protein Transport / drug effects
  • Spinocerebellar Ataxias / enzymology*
  • Spinocerebellar Ataxias / genetics*
  • Subcellular Fractions / drug effects
  • Subcellular Fractions / enzymology
  • Tetradecanoylphorbol Acetate / pharmacology


  • protein kinase C gamma
  • Protein Kinase C
  • Mitogen-Activated Protein Kinase 1
  • Tetradecanoylphorbol Acetate