ESAT-6 modulates Calcimycin-induced autophagy through microRNA-30a in mycobacteria infected macrophages

J Infect. 2019 Aug;79(2):139-152. doi: 10.1016/j.jinf.2019.06.001. Epub 2019 Jun 8.


Objective: Mycobacterium tuberculosis (M. tb) has a sumptuous repertoire of effector molecules to counter host defenses. Some of these antigens inhibit autophagy but the exact mechanism of this inhibition is poorly understood.

Methods: Purified protein derivative (PPD) was fractionated using 10 (PPD 10, antigenic molecular weight > 10 kDa) and 3 (PPD 3, mol. weight > 3 kDa) kDa cutters. Effect of these fractions on Calcimycin-induced autophagy and intracellular mycobacterial viability was then studied using different experimental approaches.

Result: We found significant downregulation of autophagy by PPD 3 pre-treatment in Calcimycin-treated dTHP-1 cells compared to PPD 10. This reduction in autophagy also corroborated with the enhanced survival of mycobacteria in macrophages. We demonstrate that recombinant early secreted antigenic target 6 (rESAT-6) is responsible to inhibit Calcimycin-induced autophagy and enhance intracellular survival of mycobacteria. We also show that pre-treatment with rESAT-6 upregulates microRNA (miR)-30a-3p expression and vis-a-vis downregulates miR-30a-5p expression in Calcimycin-treated dTHP-1 cells. Transfection studies with either miR-30a-3p inhibitor or miR-30a-5p mimic clearly elucidated the opposing roles of miR-30a-3p and miR-30a-5p in rESAT-6 mediated mycobacterial survival through autophagy inhibition.

Conclusion: Taken together, our result evidently highlights that rESAT-6 enhances intracellular survival of mycobacteria by modulating miR-30a-3p and miR-30a-5p expression.

Keywords: Autophagy; Calcimycin; ESAT-6; Human macrophages; Tuberculosis; micro-RNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Bacterial / metabolism*
  • Autophagy / drug effects*
  • Bacterial Proteins / metabolism*
  • Calcimycin / pharmacology*
  • Cell Line
  • Gene Expression Regulation / drug effects
  • Host-Pathogen Interactions*
  • Humans
  • Macrophages / metabolism*
  • Macrophages / microbiology*
  • MicroRNAs / genetics*
  • Microbial Viability / drug effects
  • Models, Biological
  • Mycobacterium bovis
  • Mycobacterium tuberculosis / drug effects*
  • Signal Transduction
  • Tuberculosis / genetics
  • Tuberculosis / metabolism
  • Tuberculosis / microbiology


  • Antigens, Bacterial
  • Bacterial Proteins
  • ESAT-6 protein, Mycobacterium tuberculosis
  • MIRN30b microRNA, human
  • MicroRNAs
  • Calcimycin