RESUMO
It is urgent to understand the regulatory mechanism of drug resistance in widespread bacterial pathogens. In Mycobacterium tuberculosis, several transcriptional regulators have been found to play essential roles in regulating its drug resistance. In this study, we found that an ArsR family transcription regulator encoded by Rv2642 (CdiR) responds to isoniazid (INH), a widely used anti-tuberculosis (TB) drug. CdiR negatively regulates self and adjacent genes, including arsC (arsenic-transport integral membrane protein ArsC). CdiR directly interacts with INH and Cd(II). The binding of INH and Cd(II) both reduce its DNA-binding activity. Disrupting cdiR increased the drug susceptibility to INH, whereas overexpressing cdiR decreased the susceptibility. Strikingly, overexpressing arsC increased the drug susceptibility as well as cdiR. Additionally, both changes in cdiR and arsC expression caused sensitivity to other drugs such as rifamycin and ethambutol, where the minimal inhibitory concentrations in the cdiR deletion strain were equal to those of the arsC-overexpressing strain, suggesting that the function of CdiR in regulating drug resistance primarily depends on arsC. Furthermore, we found that Cd(II) enhances bacterial resistance to INH in a CdiR-dependent manner. As a conclusion, CdiR has a critical role in directing the interplay between Cd(II) metal ions and drug susceptibility in mycobacteria.
Assuntos
Antituberculosos/farmacologia , Proteínas de Bactérias/metabolismo , Cádmio/metabolismo , Isoniazida/farmacologia , Mycobacterium tuberculosis/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/genética , Farmacorresistência Bacteriana/efeitos dos fármacos , Etambutol/farmacologia , Regulação Bacteriana da Expressão Gênica , Humanos , Testes de Sensibilidade Microbiana/métodos , Mycobacterium/genética , Mycobacterium/metabolismo , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Rifamicinas/farmacologia , Fatores de Transcrição/genéticaRESUMO
The bacteria drug resistance is not only associated with the gain of drug resistance gene but also relied on the adaptation of bacterial cells to antibiotics by transcriptional regulation. However, only a few transcription factors that regulate drug resistance have been characterized in mycobacteria. In this study, a TetR family transcriptional factor (OxiR), encoded by Rv0067c in Mycobacterium tuberculosis, was found to be an isoniazid (INH) resistance regulator. Comparing with the wild-type strain, the oxiR overexpressing strain is four times resistant to INH, whereas the oxiR knockout strain is eight times sensitive to INH. However, the rifamycin and ethambutol resistance were not influenced by oxiR. OxiR can bind to self-promoter at a 66 bp imperfect palindromic motifs. Interestingly, OxiR directly binds to INH, and thereby alleviate the self-repression. Furthermore, OxiR negatively regulated an oxidoreductase encoded by Rv0068. And the susceptibility of the Rv0068-overexpressing and oxiR knockout strains to all the three above-mentioned anti-tuberculosis drugs was equivalent, suggesting that the effect of oxiR to INH susceptibility is attributed to the derepression of Rv0068. In conclusion, we showed that OxiR can specifically modulate INH susceptibility by regulating an oxidoreductase encoding gene, both of which have not been associated with drug-resistance previously.
Assuntos
Antituberculosos/farmacologia , Proteínas de Bactérias/genética , Farmacorresistência Bacteriana/genética , Isoniazida/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Fatores de Transcrição/genética , Regulação Bacteriana da Expressão Gênica , Mycobacterium tuberculosis/genética , Oxirredutases/genética , Tuberculose/microbiologiaRESUMO
The ferric uptake regulator A (FurA) plays an essential role in responding to oxidative stress in mycobacteria. The genome of Mycobacterium smegmatis harbours three FurA orthologs; however, the potential cross-talk and contribution to drug resistance of different furA operon remain underdetermined. In this study, we characterized the cross-regulation and effect in drug resistance of these orthologs from M. smegmatis. Cross-binding of FurA protein to furA promoter was observed. The binding of FurA1 to furA3p and FurA2 to furA1p or furA3p is even more pronounced than their self-binding. The three FurA proteins are all functional at repressing the expression of the peroxidase enzyme katG1/katG2 in vivo. When overexpressing any of the furA orthologs in M. smegmatis, the bacteria become more resistant to isoniazid (INH). This pattern is consistent with that in Mycobacterium bovis. However, the knockdown of furA does not affect the INH sensitivity. This is the first report of cross-talk and contribution to drug resistance of all three furA orthologs in M. smegmatis.
