Dual proteomics of infected macrophages reveal bacterial and host players involved in the Francisella intracellular life cycle and cell to cell dissemination by merocytophagy

• Published in: Scientific reports Vol. 14; no. 1; p. 7797
• Main Authors: Rytter, Héloïse, Roger, Kevin, Chhuon, Cerina, Ding, Xiongqi, Coureuil, Mathieu, Jamet, Anne, Henry, Thomas, Guerrera, Ida Chiara, Charbit, Alain
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 02-04-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 631/326/41/2533; 631/326/421; Aconitate decarboxylase; Actin; Actins; Actins - metabolism; Animals; Bacterial Proteins; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biosynthesis; Biotin; Biotin - metabolism; Flow cytometry; Francisella; Francisella tularensis; Francisella tularensis - genetics; Genomic Islands; Humanities and Social Sciences; Intracellular; Life Cycle Stages; Life cycles; Life Sciences; Macrophages; Macrophages - metabolism; Molecular modelling; multidisciplinary; Pathogenicity; Pathogens; Polymerization; Proteins; Proteomes; Proteomics; Replication; Science; Science (multidisciplinary); Tularemia; Tularemia - microbiology; Pathogens; Bacterial host response
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-024-58261-x

Bacterial pathogens adapt and replicate within host cells, while host cells develop mechanisms to eliminate them. Using a dual proteomic approach, we characterized the intra-macrophage proteome of the facultative intracellular pathogen,
Francisella novicida
. More than 900
Francisella
proteins were identified in infected macrophages after a 10-h infection. Biotin biosynthesis-related proteins were upregulated, emphasizing the role of biotin-associated genes in Francisella replication. Conversely, proteins encoded by the
Francisella
pathogenicity island (FPI) were downregulated, supporting the importance of the
F. tularensis
Type VI Secretion System for vacuole escape, not cytosolic replication. In the host cell, over 300 proteins showed differential expression among the 6200 identified during infection. The most upregulated host protein was cis-aconitate decarboxylase IRG1, known for itaconate production with antimicrobial properties in
Francisella
. Surprisingly, disrupting IRG1 expression did not impact
Francisella
’s intracellular life cycle, suggesting redundancy with other immune proteins or inclusion in larger complexes. Over-representation analysis highlighted cell–cell contact and actin polymerization in macrophage deregulated proteins. Using flow cytometry and live cell imaging, we demonstrated that merocytophagy involves diverse cell-to-cell contacts and actin polymerization-dependent processes. These findings lay the groundwork for further exploration of merocytophagy and its molecular mechanisms in future research.
Data are available via ProteomeXchange with identifier PXD035145.