Calcimycin mediates mycobacterial killing by inducing intracellular calcium-regulated autophagy in a P2RX7 dependent manner.

Phenotypic screening led to the identification of calcimycin as a potent inhibitor of Mycobacterium bovis BCG (M. bovis BCG) growth in vitro and in THP-1 cells. In the present study, we aim to decipher the mechanism of antimycobacterial activity of calcimycin. We noticed that treatment with calcimycin led to up-regulation of different autophagy markers like Beclin-1, autophagy-related gene (Atg) 7, Atg 3 and enhanced microtubule-associated protein 1A/1B-light chain 3-I (LC3-I) to LC3-II conversion in macrophages. This calcimycin-mediated killing of intracellular M. smegmatis and M. bovis BCG was abrogated in the presence of 3-methyladenine (3-MA). We also demonstrate that calcimycin binding with purinergic receptor P2X7 (P2RX7) led to increase in intracellular calcium level that regulates the extracellular release of ATP. ATP was able to regulate calcimycin-induced autophagy through P2RX7 in an autocrine fashion. Blocking of either P2RX7 expression by 1-[N,O-bis(5-Isoquinolinesulfonyl)-N-methyl-l-tyrosyl]-4-phenylpiperazine (KN-62) or reducing intracellular calcium levels by 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra (acetoxy-methyl) ester (BAPTA-AM) abrogated the antimycobacterial activity of calcimycin. Taken together, these results showed that calcimycin exerts its antimycobacterial effect by regulating intracellular calcium-dependent ATP release that induces autophagy in a P2RX7 dependent manner. Copyright © 2017 Elsevier B.V. All rights reserved.

Citation

Shradha Mawatwal, Assirbad Behura, Abhirupa Ghosh, Saqib Kidwai, Abtar Mishra, Amar Deep, Sakshi Agarwal, Sudipto Saha, Ramandeep Singh, Rohan Dhiman. Calcimycin mediates mycobacterial killing by inducing intracellular calcium-regulated autophagy in a P2RX7 dependent manner. Biochimica et biophysica acta. 2017 Dec;1861(12):3190-3200

PMID: 28935606

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