Novel aspects of iron homeostasis in pathogenic bloodstream form Trypanosoma brucei.
File(s)ppat.1009696_1.pdf (7.81 MB)
Accepted version
Author(s)
Type
Journal Article
Abstract
Iron is an essential regulatory signal for virulence factors in many pathogens. Mammals and bloodstream form (BSF) Trypanosoma brucei obtain iron by receptor-mediated endocytosis of transferrin bound to receptors (TfR) but the mechanisms by which T. brucei subsequently handles iron remains enigmatic. Here, we analyse the transcriptome of T. brucei cultured in iron-rich and iron-poor conditions. We show that adaptation to iron-deprivation induces upregulation of TfR, a cohort of parasite-specific genes (ESAG3, PAGS), genes involved in glucose uptake and glycolysis (THT1 and hexokinase), endocytosis (Phosphatidic Acid Phosphatase, PAP2), and most notably a divergent RNA binding protein RBP5, indicative of a non-canonical mechanism for regulating intracellular iron levels. We show that cells depleted of TfR by RNA silencing import free iron as a compensatory survival strategy. The TfR and RBP5 iron response are reversible by genetic complementation, the response kinetics are similar, but the regulatory mechanisms are distinct. Increased TfR protein is due to increased mRNA. Increased RBP5 expression, however, occurs by a post-transcriptional feedback mechanism whereby RBP5 interacts with its own, and with PAP2 mRNAs. Further observations suggest that increased RBP5 expression in iron-deprived cells has a maximum threshold as ectopic overexpression above this threshold disrupts normal cell cycle progression resulting in an accumulation of anucleate cells and cells in G2/M phase. This phenotype is not observed with overexpression of RPB5 containing a point mutation (F61A) in its single RNA Recognition Motif. Our experiments shed new light on how T. brucei BSFs reorganise their transcriptome to deal with iron stress revealing the first iron responsive RNA binding protein that is co-regulated with TfR, is important for cell viability and iron homeostasis; two essential processes for successful proliferation.
Date Issued
2021-06-23
Date Acceptance
2021-06-04
Citation
PLoS Pathogens, 2021, 17 (6), pp.1-34
ISSN
1553-7366
Publisher
Public Library of Science (PLoS)
Start Page
1
End Page
34
Journal / Book Title
PLoS Pathogens
Volume
17
Issue
6
Copyright Statement
© 2021 Gilabert Carbajo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
License URL
Sponsor
Wellcome Trust
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/34161395
PII: PPATHOGENS-D-21-00219
Grant Number
208780/Z/17/Z
Subjects
Virology
0605 Microbiology
1107 Immunology
1108 Medical Microbiology
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2021-06-23