Proteome profiling indicates a link between mitochondrial pathways and the host-microbial sensor ELMO1 following Salmonella infection

TL;DR

This study shows that ELMO1, a protein that detects bacteria, influences mitochondrial activity and immune responses during Salmonella infection.

Contribution

The study reveals a novel role for ELMO1 in modulating mitochondrial functions and inflammatory responses during Salmonella infection.

Findings

ELMO1 depletion alters mitochondrial metabolism from oxidative phosphorylation to glycolysis during Salmonella infection.

Mitochondrial fission protein DRP1 is upregulated in ELMO1-depleted cells, linking ELMO1 to mitochondrial dynamics.

Pharmacological inhibition of DRP1 reduces pro-inflammatory cytokine TNF-α, highlighting the ELMO1-DRP1 pathway's role in immune regulation.

Abstract

The host EnguLfment and cell MOtility protein 1 (ELMO1) is a cytosolic microbial sensor that binds bacterial effector proteins, including pathogenic effectors from Salmonella (Salmonella enterica serovar Typhimurium) and controls host innate immune signaling. To understand the ELMO1-regulated host pathways, we have performed liquid chromatography Multinotch MS3-Tandem Mass Tag (TMT) multiplexed proteomics to determine the global quantification of proteins regulated by ELMO1 in macrophages during Salmonella infection. Comparative proteome analysis of control and ELMO1-depleted murine J774 macrophages after Salmonella infection quantified more than 7000 proteins with a notable enrichment in mitochondrial-related proteins. Gene ontology enrichment analysis revealed 19 upregulated and 11 downregulated proteins exclusive to ELMO1-depleted cells during infection, belonging to mitochondrial functions, metabolism, vesicle transport, and the immune system. Seahorse analysis showed that Salmonella infection alters mitochondrial metabolism from oxidative phosphorylation to glycolysis-a shift significantly influenced by the depletion of ELMO1. Furthermore, ELMO1 depletion decreased the ATP rate index following Salmonella infection, indicating its importance in counteracting the effects of Salmonella on immunometabolism. Among the proteins involved in mitochondrial pathways, the mitochondrial fission protein DRP1 was significantly upregulated in ELMO1-depleted cells and ELMO1-KO mice intestine following Salmonella infection. Pharmacological inhibition of DRP1 identified the role of ELMO1-DRP1 pathway in the regulation of pro-inflammatory cytokine TNF-α following infection. The role of ELMO1 has been further characterized by a Proteome profiling of ELMO1-depleted macrophage infected with SifA mutant displayed the involvement of ELMO1-SifA in mitochondrial function, metabolism and host immune/defense responses. Collectively, these findings reveal a novel role for ELMO1 in modulating mitochondrial functions, potentially pivotal in modulating inflammatory responses.

Figures