Characterisation of two Toxoplasma PROPPINs homologous to Atg18/WIPI suggests they have evolved distinct specialised functions

PLoS One. 2018 Apr 16;13(4):e0195921. doi: 10.1371/journal.pone.0195921. eCollection 2018.

Abstract

Toxoplasma gondii is a parasitic protist possessing a limited set of proteins involved in the autophagy pathway, a self-degradative machinery for protein and organelle recycling. This distant eukaryote has even repurposed part of this machinery, centered on protein ATG8, for a non-degradative function related to the maintenance of the apicoplast, a parasite-specific organelle. However, some evidence also suggest Toxoplasma is able to generate autophagic vesicles upon stress, and that some autophagy-related proteins, such as ATG9, might be involved solely in the canonical autophagy function. Here, we have characterised TgPROP1 and TgPROP2, two Toxoplasma proteins containing WD-40 repeat that can bind lipids for their recruitment to vesicular structures upon stress. They belong to the PROPPIN family and are homologues to ATG18/WIPI, which are known to be important for the autophagic process. We conducted a functional analysis of these two Toxoplasma PROPPINs. One of them is dispensable for normal in vitro growth, although it may play a role for parasite survival in specific stress conditions or for parasite fitness in the host, through a canonical autophagy-related function. The other, however, seems important for parasite viability in normal growth conditions and could be primarily involved in a non-canonical function. These divergent roles for two proteins from the same family illustrate the functional versatility of the autophagy-related machinery in Toxoplasma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Autophagy / genetics
  • Autophagy-Related Proteins / chemistry
  • Autophagy-Related Proteins / genetics*
  • Autophagy-Related Proteins / metabolism
  • Cell Line
  • Cluster Analysis
  • Evolution, Molecular*
  • Genome, Protozoan
  • Humans
  • Multigene Family
  • Mutation
  • Open Reading Frames
  • Protein Binding
  • Protein Multimerization
  • Protein Transport
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics*
  • Protozoan Proteins / metabolism
  • Stress, Physiological / genetics
  • Toxoplasma / genetics*
  • Toxoplasma / metabolism

Substances

  • Autophagy-Related Proteins
  • Protozoan Proteins

Grants and funding

Work in S.B.’s laboratory is supported by a grant from Agence Nationale de la Recherche (ANR-13-JSV3-0003) and core support from the Fondation pour la Recherche Médicale (Equipe FRMDEQ20130326508) and the Labex Parafrap (Agence Nationale de la Recherche) (ANR-11-LABX-0024). Work in F.T.’s laboratory is supported by grants from the National Natural Science Foundation of China (81672052), the Zhejiang Natural Science Funds for Distinguished Young Scientists (LR17H190001) and Zhejiang Xinmiao talent plan (2017R413062). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.