Involvement of 14-3-3 protein post-translational modifications in Giardia duodenalis encystation

Int J Parasitol. 2010 Feb;40(2):201-13. doi: 10.1016/j.ijpara.2009.07.010. Epub 2009 Sep 3.


14-3-3s are a family of phosphoserine/phosphothreonine binding proteins directly affecting many protein functions by regulating enzyme activity, intracellular localisation or mediating protein-protein interaction. The single 14-3-3 (g14-3-3) of the flagellated parasite Giardia duodenalis is phosphorylated at residue threonine 214 (T214) and polyglycylated at the extreme C-terminus in a stage-specific manner. To define the role of each post-translational modification, Giardia transgenic lines expressing a N-terminally FLAG-tagged g14-3-3, or the single point mutant T214A, or the E246A and the E247A mutants of the putative polyglycylation sites, were generated in this study. By affinity chromatography and MALDI-MS analysis, Glu246 was identified as the only site of polyglycylation. The absence of a polyglycine chain results in the nuclear localisation of the protein at any parasite life-stage, suggesting a role for polyglycylation in 14-3-3 nucleo/cytoplasm shuttling. Moreover, cyst formation was strongly induced in parasites expressing the E246A mutant and delayed in those harbouring the T214A mutant. Finally, in vitro overlay assays with a GST_T214E mutant indicated that phosphorylation can alter in vitro the binding properties of 14-3-3. The present data suggest that g14-3-3 post-translational modifications act in combination to affect encystation efficiency in Giardia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / chemistry
  • 14-3-3 Proteins / genetics
  • 14-3-3 Proteins / metabolism*
  • Giardia / genetics
  • Giardia / growth & development*
  • Giardia / metabolism*
  • Peptides / metabolism
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Protein Transport
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*


  • 14-3-3 Proteins
  • Peptides
  • Protozoan Proteins
  • polyglycine