Copper homeostasis in tuberculous mycobacteria: implications for the intracellular battle and antibiotic tolerance

• Grant number: 23/13388-9
• Support Opportunities: Regular Research Grants
• Start date: August 01, 2024
• End date: July 31, 2026
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal Investigator: Ana Marcia de Sá Guimarães
• Grantee: Ana Marcia de Sá Guimarães
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Kevin Waldron

Abstract

The pathogens of the Mycobacterium tuberculosis complex (MTBC), which cause tuberculosis (TB) in humans and animals, have different virulence and host tropism profiles, but highly similar genomes that are incapable of horizontally transferring genes. My laboratory has sought to understand how the small genotypic variations of these genomes result in different MTBC phenotypes. Recently, we detected differences in the copper metabolism among these pathogens. During infection, these organisms encounter fluctuations in copper concentrations as part of the nutritional immunity exerted by the host. This strategy modulates the availability of the metal to kill the pathogen through starvation or intoxication. However, we discovered that Mycobacterium africanum lineage 6 (MafL6), one of the pathogens of human TB, has a defect in its ability to regulate copper bioavailability. Furthermore, the toxicity induced by copper, characterized by the production of reactive oxygen species and mismetallation of proteins with Fe-S clusters, suggests that exposure to the metal may lead to the emergence of populations that tolerate host stressors and antibiotics. This tolerance may be mediated by mechanisms such as dormancy and variations in the envelope lipids. We also observed that both M. tuberculosis (Mtb) and MafL6 present subpopulations tolerant to copper overload, suggesting the existence of pre-established phenotypic heterogeneity. In agreement with our previous studies, we believe that phase-variation of genes through frameshifts can contribute to this heterogeneity. Therefore, in this project we will test three hypotheses: (i) that copper homeostasis differs between species of tuberculous mycobacteria, determining their ability to enter dormancy and/or a non-replicative state; (ii) that Mtb, MafL5 and MafL6 become more tolerant to antimicrobials when pre-exposed to high concentrations of copper; and (iii) that frameshift changes are associated with copper tolerance states in Mtb and MafL6. The results of this study will help to understand the patho-evolution of the MTBC, and the mechanisms associated with the persistence of these pathogens within cells and in face of antibiotics. These discoveries may unveil targets for future strategies to combat the disease. (AU)