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Iron chelators modulate the fusogenic properties of Salmonella-containing phagosomes
Nada Jabado1, Patricia Cuellar-Mata, Sergio Grinstein
1Department of Biochemistry, McGill University, Montreal, QC, Canada H3G-1Y6.
Abstract:
In macrophages, the divalent cations transporter Nramp1 is recruited from the lysosomal compartment to the membrane of phagosomes formed in these cells. Nramp1 mutations cause susceptibility to infection with intracellular pathogens such as Salmonella and Mycobacterium. Intracellular survival of Salmonella involves segregation in an endomembrane compartment (Salmonella-containing vacuole, SCV) that remains negative for the mannose-6-phosphate receptor (M6PR) and that is inaccessible to the endocytic pathway. Expression of Nramp1 at the membrane of SCVs stimulates both acquisition of M6PR and accessibility to newly formed endosomes. The possible role of Nramp1-mediated iron transport on SCV maturation was investigated with membrane-permeant iron chelators. Pretreatment of primary macrophages from Nramp1 mutant mice or of RAW264.7 macrophages (from BALBc mice bearing an Nramp1(D169)-deficient allele) with either desferrioxamine or salicylaldehyde isocotinoyl hydrazone restored recruitment of M6PR and delivery of the fluid phase marker rhodamine dextran to SCVs to levels similar to those seen in macrophages expressing WT Nramp1. The effect was specific and dose-dependent and could be abrogated by preincubation with excess iron. These data suggest that Nramp1-mediated deprivation of iron and possibly of other divalent metals in macrophages antagonizes the ability of Salmonella to alter phagosome maturation.
Insights
The divalent cations transporter Nramp1 in macrophages influences Salmonella survival. Iron deprivation by Nramp1 antagonizes Salmonella
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Nramp1 (divalent cations transporter) is crucial for macrophage defense against intracellular pathogens.
- Nramp1 mutations increase susceptibility to infections like Salmonella.
- Salmonella resides in Salmonella-containing vacuoles (SCVs) that evade the endocytic pathway.
Purpose of the Study:
- To investigate the role of Nramp1-mediated iron transport in Salmonella-containing vacuole (SCV) maturation.
- To understand how Nramp1 influences the acquisition of mannose-6-phosphate receptor (M6PR) and endosome delivery to SCVs.
Main Methods:
- Utilized membrane-permeant iron chelators (desferrioxamine, salicylaldehyde isocotinoyl hydrazone) on Nramp1 mutant and wild-type macrophages.
- Assessed the recruitment of M6PR and delivery of rhodamine dextran to SCVs.
- Examined the effect of iron chelation and iron repletion on SCV maturation.
Main Results:
- Iron chelation restored M6PR recruitment and endosome delivery to SCVs in Nramp1-deficient macrophages.
- The observed effects were dose-dependent and specific to iron chelation.
- The chelator's effect was reversed by preincubation with excess iron.
Conclusions:
- Nramp1-mediated iron deprivation in macrophages inhibits Salmonella's manipulation of phagosome maturation.
- Nramp1's role in iron transport is critical for controlling intracellular pathogen survival within macrophages.
- Targeting Nramp1-mediated metal transport may offer strategies against Salmonella infections.