Amino acid permeases in Cryptococcus neoformans are required for high temperature growth and virulence; and are regulated by Ras signaling

PLoS One. 2019 Jan 25;14(1):e0211393. doi: 10.1371/journal.pone.0211393. eCollection 2019.

Abstract

Cryptococcosis is an Invasive Fungal Infection (IFI) caused by Cryptococcus neoformans, mainly in immunocompromised patients. Therapeutic failure due to pathogen drug resistance, treatment inconstancy and few antifungal options is a problem. The study of amino acid biosynthesis and uptake represents an opportunity to explore possible development of novel antifungals. C. neoformans has 10 amino acids permeases, two of them (Aap3 and Aap7) not expressed at the conditions tested, and five were studied previously (Aap2, Aap4, Aap5, Mup1 and Mup3). Our previous results showed that Aap4 and Aap5 are major permeases with overlapping functions. The aap4Δ/aap5Δ double mutant fails to grow in amino acids as sole nitrogen source and is avirulent in animal model. Here, we deleted the remaining amino acid permeases (AAP1, AAP6, AAP8) that showed gene expression modulation by nutritional condition and created a double mutant (aap1Δ/aap2Δ). We studied the virulence attributes of these mutants and explored the regulatory mechanism behind amino acid uptake in C. neoformans. The aap1Δ/aap2Δ strain had reduced growth at 37°C in L-amino acids, reduced capsule production and was hypovirulent in the Galleria mellonella animal model. Our data, along with previous studies, (i) complement the analysis for all 10 amino acid permeases mutants, (ii) corroborate the idea that these transporters behave as global permeases, (iii) are required during heat and nutritional stress, and (iv) are important for virulence. Our study also indicates a new possible link between Ras1 signaling and amino acids uptake.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Transport Systems / chemistry
  • Amino Acid Transport Systems / genetics
  • Amino Acid Transport Systems / metabolism*
  • Amino Acids / metabolism
  • Cryptococcus neoformans / growth & development
  • Cryptococcus neoformans / physiology*
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Mutagenesis
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Sequence Alignment
  • Signal Transduction*
  • Stress, Physiological
  • Temperature
  • Virulence / genetics*
  • ras Proteins / genetics
  • ras Proteins / metabolism*

Substances

  • Amino Acid Transport Systems
  • Amino Acids
  • Fungal Proteins
  • Protein Isoforms
  • ras Proteins

Grants and funding

This study was funded by Fundação de Amparo à Pesquisa do Estado de São Paulo (grants 2016/14542-8 to Dr. Renata C Pascon, 2015/04400-9 to Dr Marcelo Afonso Vallim, 2016/23890-0 to João Miguel Nunes), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (awarded to Ms Crislaine Lambiase Calvete and Kevin Felipe Martho). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.