Phosphorylation at the Hydrophobic Site of Protein Kinase C Apl II Is Increased During Intermediate Term Facilitation

Neuroscience. 2006 Aug 11;141(1):277-85. doi: 10.1016/j.neuroscience.2006.03.063. Epub 2006 May 4.


In Aplysia, persistent increases in synaptic strength are paralleled by the persistent activation of the novel protein kinase C Apl II. We raised a phosphospecific antibody against serine 725, the hydrophobic motif in protein kinase C Apl II. Phosphorylation of serine 725 increased in parallel to the persistent activation of the kinase. We expressed protein kinase C where this site was mutated to an alanine to prevent phosphorylation. The mutated protein kinase C showed decreased specific activity consistent with a model where the kinase is less stable in the absence of phosphorylation of this site. Endogenous phosphorylation of protein kinase C Apl II at serine 725 was unaffected by either activation of protein kinase C by phorbol esters, or inhibition of protein kinase C using two distinct inhibitors, suggesting the site is not autophosphorylated. Consistent with this, overexpressed kinase-dead protein kinase C Apl II still was phosphorylated at serine 725, although to a lesser extent than wild-type protein kinase C Apl II. While PDK appears to interact with the serine 725 site, it is not responsible for its phosphorylation. Finally inhibition of phosphoinositide-3 kinase or the target of rapamycin by pharmacological agents did not block basal phosphorylation of serine 725 in Aplysia ganglia. Our results suggest trans-phosphorylation of protein kinase C Apl II as Ser 725 occurs during persistent activation of the kinase, but this does not appear to be downstream of phosphoinositide-3 kinase.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaloids
  • Amino Acid Motifs / physiology
  • Animals
  • Aplysia
  • Benzophenanthridines
  • Blotting, Western / methods
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cytosol / drug effects
  • Cytosol / metabolism
  • Enzyme Inhibitors / pharmacology
  • Functional Laterality
  • Ganglia, Invertebrate / cytology
  • Ganglia, Invertebrate / drug effects
  • Ganglia, Invertebrate / metabolism*
  • Gene Expression / drug effects
  • Isoenzymes / metabolism*
  • Mutation / physiology
  • Phenanthridines / pharmacology
  • Phorbol Esters / pharmacology
  • Protein Kinase C / metabolism*
  • Serine / metabolism*
  • Temperature


  • Alkaloids
  • Benzophenanthridines
  • Enzyme Inhibitors
  • Isoenzymes
  • Phenanthridines
  • Phorbol Esters
  • Serine
  • chelerythrine
  • Apl II protein kinase C
  • Protein Kinase C