Expression, production and release of the Eis protein by Mycobacterium tuberculosis during infection of macrophages and its effect on cytokine secretion

Abstract

The eis gene of Mycobacterium tuberculosis has been shown to play a role in the survival of the avirulent Mycobacterium smegmatis within the macrophage. In vitro and in vivo analysis of Deis deletion mutants and complemented strains showed no effect on survival of M. tuberculosis in U-937 macrophages or in a mouse aerosol infection model, respectively. Further studies were done in an attempt to determine the role of eis in M. tuberculosis intracellular survival and to define a phenotypic difference between wild-type and the Deis deletion mutant. Bioinformatic analysis indicated that Eis is an acetyltransferase of the GCN5-related family of N-acetyltransferases. Immunofluorescence microscopy and Western blot analysis studies demonstrated that Eis is released into the cytoplasm of M. tuberculosis-infected U-937 macrophages. Eis was also found in the extravesicular fraction and culture supernatant of M. tuberculosis-infected macrophages. The effect of Eis on human macrophage cytokine secretion was also examined. Eis modulated the secretion of IL-10 and TNF-a by primary human monocytes in response both to infection with M. tuberculosis and to stimulation with recombinant Eis protein. These results suggest that Eis is a mycobacterial effector that is released into the host cell to modulate inflammatory responses, possibly via transcriptional or post-translational means.

Unusual regioversatility of acetyltransferase Eis, a cause of drug resistance in XDR-TB

“…The biological function of Eis in Mtb has been the subject of recent interest (6,7,(22)(23)(24)(25)(26)(27)(28)(29). The biochemical and structural studies described in this report provide clear evidence for an unprecedented multiacetylation capability of Eis that inactivates AG antibiotics.…”

Activation of the eis gene in a W-Beijing strain of Mycobacterium tuberculosis correlates with increased SigA levels and enhanced intracellular growth

“…It is possible that Eis of M. tuberculosis has functions lacked by the homologous genes. Eis is a member of the GNAT superfamily of acetyltransferases (Samuel et al, 2007), and although there are some conserved motifs within these enzymes, they also have extensive sequence variation and a broad array of roles (Vetting et al, 2005). Comparative analyses of the mycobacterial orthologues may give insights into the regions of the M. tuberculosis gene that are important in host-pathogen interactions, and shed light on the function of M. tuberculosis Eis.…”

“…An eis deletion mutant induces higher levels of TNF-a and lower levels of IL-10 in monocytes than those induced by control strains (Samuel et al, 2007), suggesting that Eis induces secretion of IL-10, which is known to inhibit TNF-a production. However, the eis mutant shows no growth defect in a macrophage cell line or in mice (Samuel et al, 2007). Eis reduces TNF-a and IL-4 production by mitogen-stimulated human T-cells (Lella & Sharma, 2007), indicating that Eis affects T-cell function.…”

“…Subsequent studies from the same laboratory indicate that the Eis protein is present in cytosolic and cell envelope fractions of M. tuberculosis, and that it is released into culture supernatants and into the cytoplasm of infected macrophages (Dahl et al, 2001;Samuel et al, 2007). In one study, sera from 40 % of pulmonary tuberculosis patients were positive for anti-Eis antibody, indicating that the protein is antigenic (Dahl et al, 2001).Bioinformatic analyses suggest that Eis is an acetyltransferase (Samuel et al, 2007), and additional evidence indicates that it modulates the host immune response (Lella & Sharma, 2007;Samuel et al, 2007), but the precise function of Eis is unclear. An eis deletion mutant induces higher levels of TNF-a and lower levels of IL-10 in monocytes than those induced by control strains (Samuel et al, 2007), suggesting that Eis induces secretion of IL-10, which is known to inhibit TNF-a production.…”

“…The eis gene was originally identified by the Friedman laboratory based on the ability of the M. tuberculosis gene to enhance survival of the non-pathogenic species Mycobacterium smegmatis in macrophages, hence the name 'eis' for 'enhanced intracellular survival ' (Wei et al, 2000). Subsequent studies from the same laboratory indicate that the Eis protein is present in cytosolic and cell envelope fractions of M. tuberculosis, and that it is released into culture supernatants and into the cytoplasm of infected macrophages (Dahl et al, 2001;Samuel et al, 2007). In one study, sera from 40 % of pulmonary tuberculosis patients were positive for anti-Eis antibody, indicating that the protein is antigenic (Dahl et al, 2001).…”