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Shotgun proteomic profiling of dormant, 'non-culturable' Mycobacterium tuberculosis

ABSTRACT: Dormant cells of Mycobacterium tuberculosis, in addition to low metabolic activity and a high level of drug resistance, are characterized by ‘non-culturability’ – a specific reversible state of the inability of the cells to grow on solid media. The biochemical characterization of this physiological state of the pathogen is only superficial, pending clarification of the metabolic processes that may exist in such cells. In this study, applying LC-MS proteomic profiling, we report the analysis of proteins accumulated in dormant, ‘non-culturable’ M. tuberculosis cells in an in vitro model of self-acidification of mycobacteria in the post-stationary phase, simulating the in vivo persistence conditions. This approach revealed the preservation of 1379 proteins in cells after 5 months of storage in dormancy; among them, 468 proteins were statistically different from those in the actively growing cells and bore a positive fold change (FC). Differential analysis revealed the proteins of the pH-dependent regulatory system PhoP and allowed the reconstruction of the reactions of central carbon/glycerol metabolism, as well as revealing the salvaged pathways of mycothiol and UMP biosynthesis, establishing the cohort of survival enzymes of dormancy. The annotated pathways mirror the adaptation of the mycobacterial metabolic machinery to life within lipid-rich macrophages: especially the involvement of the methyl citrate and glyoxylate pathways. Thus, the current in vitro model of M. tuberculosis self-acidification reflects the biochemical adaptation of these bacteria to persistence in vivo. Comparative analysis with published proteins displaying antigenic properties makes it possible to distinguish immunoreactive proteins among the proteins bearing a positive FC in dormancy, which may include specific antigens of latent tuberculosis. Additionally, the biotransformatory enzymes (oxidoreductases and hydrolases) capable of prodrug activation and stored up in the dormant state were annotated. These findings may potentially lead to the discovery of immunodiagnostic tests for early latent tuberculosis and trigger the discovery of efficient drugs/prodrugs with potency against non-replicating, dormant populations of mycobacteria.

INSTRUMENT(S): Synapt MS

ORGANISM(S): Mycobacterium Tuberculosis H37rv

TISSUE(S): Cell Culture

SUBMITTER: Filip Dyčka

LAB HEAD: Arseny S. Kaprelyants

PROVIDER: PXD028849 | Pride | 2022-07-07

REPOSITORIES: Pride

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Project description:Seed dormancy is the inability for seeds to germinate even under favorable conditions. In the Arabidopsis Landsberg erecta (Ler) ecotype, 2 weeks of dry storage, called after-ripening, is sufficient to relieve seed dormancy. Such seed is referred to as after-ripened (AR) and has a high rate of germination when imbibed. While widespread transcriptome changes have been previously observed with seed dormancy loss, this experiment was designed to characterize transcriptional changes associated with the increased seed dormancy and dormancy loss of the gibberellin (GA) hormone-insensitive sleepy1-2 (sly1-2) mutant. The SLY1 gene encodes the F-box subunit of an SCF E3 ubiquitin ligase needed for GA-triggered proteolysis of DELLA repressors of seed germination. In the sly1-2 mutant, GA-directed DELLA proteolysis cannot occur leading to DELLA protein accumulation and increased dormancy. sly1-2 mutant seeds are fully dormant at 2 weeks of dry storage (0% germination), but germinate well with very long after-ripening (51% germination after 19 months). sly1-2 seed germination can also be rescued by overexpression of the GA receptor, GA-INSENSITIVE DWARF1b (GID1b-OE), which resulted in 74% germination at 2 weeks of dry storage. In this experiment, we compared seeds of wild-type Ler at 2 weeks of dry storage (non-dormant), dormant sly1-2 (2 weeks of dry storage; sly1-2(D)), long after-ripened sly1-2 (non-dormant, 19 months of dry storage; sly1-2(AR)), and sly1-2 GID1b-OE (non-dormant, 2 weeks of dry storage). Samples were collected at two imbibition timepoints: 1) a 0h timepoint after 4 days at 4°C, and 2) a 12h timepoint after 4 days at 4°C followed by 12 hours in the light at 22°C. These timepoints were selected to capture the transcriptomes at an early and late time in Phase II of imbibition. Using this experimental design we were able to determine transcriptome differences associated with seed dormancy in the sly1-2 mutation (Ler wt vs sly1-2(D)), and changes associated with sly1-2 dormancy loss through dry after-ripening (sly1-2(AR) vs sly1-2(D)) or through GID1b-overexpression (sly1-2 GID1b-OE vs sly1-2(D)). Seeds for Ler wt, sly1-2(D), and sly1-2 GID1b-OE were grown alongside each other under the same conditions and after-ripened for 2 weeks. Seeds from sly1-2(AR) were grown under the same conditions in advance of the other lines to allow for the long after-ripening requirement. RNA was extracted using a phenol-chloroform-based extraction from three biological replicates per treatment.

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Shotgun proteomic profiling of dormant, 'non-culturable' Mycobacterium tuberculosis

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