Transcriptomic Profile of Mycobacterium smegmatis in Response to an Imidazo[1,2-b][1,2,4,5]tetrazine Reveals Its Possible Impact on Iron Metabolism

Aleksey A Vatlin,Egor A Shitikov,Ksenia M Klimina,Alan Christoffels,Valery N Danilenko,Mohd Shahbaaz,Dmitry A Bespiatykh,Dmitry A Maslov

doi:10.3389/fmicb.2021.724042

Abstract

Tuberculosis (TB), caused by the Mycobacterium tuberculosis complex bacteria, is one of the most pressing health problems. The development of new drugs and new therapeutic regimens effective against the pathogen is one of the greatest challenges in the way of tuberculosis control. Imidazo[1,2-b][1,2,4,5]tetrazines have shown promising activity against M. tuberculosis and M. smegmatis strains. Mutations in MSMEG_1380 lead to mmpS5–mmpL5 operon overexpression, which provides M. smegmatis with efflux-mediated resistance to imidazo[1,2-b][1,2,4,5]tetrazines, but the exact mechanism of action of these compounds remains unknown. To assess the mode of action of imidazo[1,2-b][1,2,4,5]tetrazines, we analyzed the transcriptomic response of M. smegmatis to three different concentrations of 3a compound: 1/8×, 1/4×, and 1/2× MIC. Six groups of genes responsible for siderophore synthesis and transport were upregulated in a dose-dependent manner, while virtual docking revealed proteins involved in siderophore synthesis as possible targets for 3a. Thus, we suggest that imidazo[1,2-b][1,2,4,5]tetrazines may affect mycobacterial iron metabolism.

Highlights

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is one of the most successful bacterial pathogens
The transcriptomic analysis of M. smegmatis mc2 155, exposed to increasing doses of the imidazo[1,2-b][1,2,4,5]tetrazine 3a has revealed a dose-dependent change in the expression of many genes involved in iron metabolism, including the genes responsible for siderophore synthesis and transport: the gene cluster responsible for exochelin synthesis and transport, mbtAG and mbtK-N clusters, ESX-3 operon, irtA-B, mmpS5–mmpL5, and bfrA-B operons
Our observations based on docking studies suggest that imidazo[1,2-b][1,2,4,5]tetrazine 3a could inhibit the iron metabolizing enzymes and may target the proteins involved in mycobactin biosynthesis, but relatively higher affinities were observed with the proteins involved in exochelin biosynthetic pathways

Summary

Introduction

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is one of the most successful bacterial pathogens. Despite many attempts to control the disease, it remains one of the world’s major health problems that causes more than 1.4 million deaths annually. The situation is complicated by the emergence of drug-resistant forms of the disease [World Health Organization (WHO)., 2020]. If the initial mathematical models suggested that resistant isolates should. Imidazotetrazines Target Mycobacterial Iron Metabolism be less transmissible and unlikely to spread successfully in human populations, it is clear that compensatory evolution and other factors drive the successful distribution of multidrug-resistant tuberculosis (Gagneux, 2009). Infection with such isolates leads to longer treatment time with more toxic and costlier than the first-line drugs-based regimens and low treatment success (Rajbhandary et al, 2004). There is an urgent need for novel drugs that are active against M. tuberculosis

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