Altered drug efflux under iron deprivation unveils abrogated MmpL3 driven mycolic acid transport and fluidity in mycobacteria
Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) is a global threat to human health hence better understanding of the MTB pathogenesis for improved therapeutics requires immediate attention. Emergence of drug-resistant strains has stimulated an urgent need for adopting new strategies that could be implemented to control TB. One of the contributing mechanisms by which MTB evades drug doses is overexpression of drug efflux pumps. Thus blocking or modulating the functionality of efflux pumps represents an attractive approach to combat drug resistance. Iron is a critical micronutrient required for MTB survival and not freely available inside the host. In this study, we demonstrated that iron deprivation impairs drug efflux pump activity and confers synergism for anti-TB drugs in presence of efflux pump inhibitors against MTB. Mechanistic insights revealed that iron deprivation inhibit resistance nodulation division superfamily transporter activity. This was evident from enhanced Nile red accumulation and reduced expression of MmpL3, a transmembrane promising target involved in mycolic acid transport across membrane. Furthermore, iron deprivation led to abrogated MA transport particularly of class methoxy-MA which was confirmed by TLC and mass spectrometry based lipidome analysis. Additionally, iron deprivation leads to enhanced membrane fluidity in MTB. Together, MmpL3 being a promiscuous anti-TB target, metal chelation strategy could be adopted to boost the effectiveness of current anti-TB drug regimes to combat drug resistance TB.
KeywordsMycobacterium Iron Efflux pump MmpL3 Mycolic acid Membrane fluidity
Z.F. thanks from Board of Research in Nuclear Sciences (BRNS), Mumbai (2013/37B/45/BRNS/1903) for the financial assistance. We are grateful to Mandira Varma-Basil, Graham F. Hatfull, Sarman Singh and Yossef Av-Gay for providing MTB (H37Rv), siderophore mutant ∆011-14, M. smegmatis mc2155 and ∆PknG mutant as generous gifts respectively. We thank Sanjeev Kanojiya, Central Drug Research Institute (CDRI), Lucknow for assisting us in mass spectrometry experiments. We thank Varatharajan Sabareesh for his intellectual support in mass spectrometry data analysis.
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