The M. tuberculosis HAD phosphatase (Rv3042c) interacts with host proteins and is inhibited by Clofazimine

Abstract

Mycobacterium tuberculosis codes for a HAD-phosphatase, Rv3042c (MtSerB2), that has earlier been characterized as a metabolic enzyme. Here we demonstrate that MtSerB2 is secreted into the cytosol of infected macrophages and is found in bronchoalveolar lavage samples of tuberculosis patients. MtSerB2 induces significant cytoskeleton rearrangements through cofilin activation and affects the expression of genes that regulate actin dynamics. It specifically interacts with HSP90, HSP70 and HSP27 that block apoptotic pathways and not with other HSPs. It actively dephosphorylates MAPK-p38 and NF-kappa B p65 that play crucial roles in inflammatory and immune responses. This in turn leads to down-regulation of Interleukin 8, a chemotactic and inflammatory cytokine. Finally, during evaluation of inhibitors against MtSerB2 we found that Clofazimine, a drug being evaluated for XDR and MDR tuberculosis, inhibits MtSerB2 phosphatase activity and reverses the above effects and interactions with host proteins. Overall, the study identifies that MtSerB2 has new functions that might help the pathogen to evade the host's immune response.

Bacterial Virulence Factors: Secreted for Survival

“…SerB2 is the most recent addition in the repertoire of Mtb's secreted virulence factors [30]. Initially characterized as an enzyme involved in the dephosphorylation of O-phospho-L-serine to L-serine [31], MtSerB2 has been recently shown to be secreted into the cytoplasm of infected THP1 cells and is hypothesized to help the bacterium in immune invasion and evasion [30].…”

“…Initially characterized as an enzyme involved in the dephosphorylation of O-phospho-L-serine to L-serine [31], MtSerB2 has been recently shown to be secreted into the cytoplasm of infected THP1 cells and is hypothesized to help the bacterium in immune invasion and evasion [30]. SerB2 belongs to the haloacid dehalogenase (HAD) class of enzymes.…”

“…1 continued keratinocytes) [35,37,38]. Recently, the same group published a follow-up study and showed that MtSerB2 was secreted in the cytoplasm of infected THP1 macrophages [30]. MtSerB2 was shown to interact with various host proteins involved in actin remodelling (actin, cofilin, a/b tubulin, etc.)…”

Nuclear Factor κB Activation Pathways During Infection

“…Through suppressing NF-κB activation, M. tuberculosis favors production of anti-inflammatory cytokines by epithelial cells, such as IL-22 and IL-10. 140 Shree and colleagues 141 reported that Rv3042c (also known as MtSerB2), a bacterial haloacid dehalogenase phosphatase, interacts with HSP90, HSP70, and HSP27 and inhibits apoptotic pathways in host cells, which in turn has been shown to be required for mycobacterial elimination. 142 Indeed, MtSerB2 dephosphorylates NF-κB and MAPK-p38, which results in cell deactivation and failure of host resistance against M. tuberculosis.…”

“…142 Indeed, MtSerB2 dephosphorylates NF-κB and MAPK-p38, which results in cell deactivation and failure of host resistance against M. tuberculosis. Pharmacologic inhibition of MtSerB2 with clofazimine, a drug used for the treatment of extensively drug resistant and multidrug resistant TB cases, is thought to successfully restore antimycobacterial cellular response, 141 reinforcing the idea that M. tuberculosis directly dampens NF-κB activation to suppress host resistance.…”