Biology subjects

Lavin, J. L.

Publications and source records attributed to Lavin, J. L..

3 recordsLinked to original sources

bioRxiv2023

Maintenance of cell wall remodeling and vesicle production are connected in Mycobacterium tuberculosis

Pathogenic and nonpathogenic mycobacteria secrete extracellular vesicles (EVs) under various conditions. EVs produced by Mycobacterium tuberculosis (Mtb) have raised significant interest for their potential in cell communication, nutrient acquisition, and immune evasion. However, the relevance of vesicle secretion during tuberculosis infection remains unknown due to the limited understanding of mycobacterial vesicle biogenesis. We have previously shown that a transposon mutant in the LCP-related gene virR (virRmut) manifested a strong attenuated phenotype during experimental macrophage and murine infections, concomitant to enhanced vesicle release. In this study, we aimed to understand the role of VirR in the vesicle production process in Mtb. We employ genetic, transcriptional, proteomics, ultrastructural and biochemical methods to investigate the underlying processes explaining the enhanced vesiculogenesis phenomenon observed in the virRmut. Our results establish that VirR is critical to sustain proper cell permeability via regulation of cell envelope remodeling possibly through the interaction with similar cell envelope proteins, which control the link between peptidoglycan and arabinogalactan. These findings advance our understanding of mycobacterial extracellular vesicle biogenesis and suggest that these set of proteins could be attractive targets for therapeutic intervention.

microbiology↗

bioRxiv2020

A conserved rRNA switch is central to decoding site maturation on the small ribosomal subunit

While a structural description of the molecular mechanisms guiding ribosome assembly in eukaryotic systems is emerging, bacteria employ an unrelated core set of assembly factors for which high-resolution structural information is still missing. To address this, we used single-particle cryo-EM to visualize the effects of bacterial ribosome assembly factors RimP, RbfA, RsmA, and RsgA on the conformational landscape of the 30S ribosomal subunit and obtained eight snapshots representing late steps in the folding of the decoding center. Analysis of these structures identifies a conserved secondary structure switch in the 16S rRNA central to decoding site maturation, and suggests both a sequential order of action and molecular mechanisms for the assembly factors in coordinating and controlling this switch. Structural and mechanistic parallels between bacterial and eukaryotic systems indicate common folding features inherent to all ribosomes.

microbiology↗

bioRxiv2020

Dynamin-like proteins are essential for vesicle biogenesis in Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) secretes pathogenicity factors and immunologically active molecules via membrane vesicles. However, nothing is known about the mechanisms involved in mycobacterial vesicle biogenesis. This study investigates molecular determinants of membrane vesicle production in Mtb by analyzing Mtb cells under conditions of high vesicle production: iron limitation and VirR restriction. Ultrastructural analysis showed extensive cell envelope restructuring in association with vesicle release that correlated with downregulation of cell surface lipid biosynthesis and peptidoglycan alterations. Comparative transcriptomics showed common upregulation of the iniBAC operon in association with high vesicle production in Mtb cells. Vesicle production analysis demonstrated that the dynamin-like proteins (DLPs) encoded by this operon, IniA and IniC, are necessary for release of EV by Mtb in culture and in infected macrophages. Isoniazid, a first-line antibiotic, used in tuberculosis treatment, was found to stimulate vesicle release in a DLP-dependent manner. Our results provide a new understanding of the function of mycobacterial DLPs and mechanistic insights into vesicle biogenesis. The findings will enable further understanding of the relevance of Mtb-derived extracellular vesicles in the pathogenesis of tuberculosis and may open new avenues for therapeutic research. IMPORTANCEIron is an essential nutrient that promotes survival and growth of M. tuberculosis, the bacterium that causes human tuberculosis (TB). Limited availability of iron, often encountered in the host environment, stimulates M. tuberculosis to secrete membrane-bound extracellular vesicles containing molecules that may help it evade the immune system. Characterizing the bacterial factors and mechanisms involved in the production of mycobacterial vesicles is important for envisioning ways to interfere with this process. Here, we report the discovery of proteins required by M. tuberculosis for vesicle biogenesis in culture and during host cell infection. We also demonstrate a connection between antibiotic response and extracellular vesicle production. The work provides insights into the mechanisms underlying vesicle biogenesis in M. tuberculosis and permits better understanding of the significance of vesicle production to M. tuberculosis-host interactions and antibiotic stress response.

microbiology↗