Biological functions of the autophagy-related proteins Atg4 and Atg8 in Cryptococcus neoformans

PLoS One. 2020 Apr 6;15(4):e0230981. doi: 10.1371/journal.pone.0230981. eCollection 2020.

Abstract

Autophagy is a mechanism responsible for intracellular degradation and recycling of macromolecules and organelles, essential for cell survival in adverse conditions. More than 40 autophagy-related (ATG) genes have been identified and characterized in fungi, among them ATG4 and ATG8. ATG4 encodes a cysteine protease (Atg4) that plays an important role in autophagy by initially processing Atg8 at its C-terminus region. Atg8 is a ubiquitin-like protein essential for the synthesis of the double-layer membrane that constitutes the autophagosome vesicle, responsible for delivering the cargo from the cytoplasm to the vacuole lumen. The contributions of Atg-related proteins in the pathogenic yeast in the genus Cryptococcus remain to be explored, to elucidate the molecular basis of the autophagy pathway. In this context, we aimed to investigate the role of autophagy-related proteins 4 and 8 (Atg4 and Atg8) during autophagy induction and their contribution with non-autophagic events in C. neoformans. We found that Atg4 and Atg8 are conserved proteins and that they interact physically with each other. ATG gene deletions resulted in cells sensitive to nitrogen starvation. ATG4 gene disruption affects Atg8 degradation and its translocation to the vacuole lumen, after autophagy induction. Both atg4 and atg8 mutants are more resistant to oxidative stress, have an impaired growth in the presence of the cell wall-perturbing agent Congo Red, and are sensitive to the proteasome inhibitor bortezomib (BTZ). By that, we conclude that in C. neoformans the autophagy-related proteins Atg4 and Atg8 play an important role in the autophagy pathway; which are required for autophagy regulation, maintenance of amino acid levels and cell adaptation to stressful conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism
  • Autophagy / genetics
  • Autophagy / physiology
  • Autophagy-Related Protein 8 Family / genetics
  • Autophagy-Related Protein 8 Family / physiology*
  • Autophagy-Related Proteins / genetics
  • Autophagy-Related Proteins / physiology*
  • Bortezomib / pharmacology
  • Cryptococcosis / drug therapy
  • Cryptococcosis / microbiology
  • Cryptococcus neoformans / drug effects
  • Cryptococcus neoformans / genetics
  • Cryptococcus neoformans / physiology*
  • Drug Resistance, Fungal
  • Fungal Proteins / genetics
  • Fungal Proteins / physiology*
  • Genes, Fungal
  • Genetic Complementation Test
  • Humans
  • In Vitro Techniques
  • Mutation
  • Nitrogen / metabolism
  • Oxidative Stress / genetics
  • Proteasome Inhibitors / pharmacology
  • Protein Processing, Post-Translational
  • Vacuoles / metabolism

Substances

  • Amino Acids
  • Autophagy-Related Protein 8 Family
  • Autophagy-Related Proteins
  • Fungal Proteins
  • Proteasome Inhibitors
  • Bortezomib
  • Nitrogen

Grants and funding

This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) grants #2015/04400-9, #2016/50185-5 to MAV and #2016/14542-8 to RCP, by the SPRINT-University of Melbourne travel grant to AI, and by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) grants #001 and #88881.133481/2016-01 to TNR.