Mycobacterium tuberculosisChaperonin 60.1 Is a More Potent Cytokine Stimulator than Chaperonin 60.2 (Hsp 65) and Contains a CD14-Binding Domain

Abstract

Much attention has focused on the Mycobacterium tuberculosis molecular chaperone chaperonin (Cpn) 60.2 (Hsp 65) in the pathology of tuberculosis because of its immunogenicity and ability to directly activate human monocytes and vascular endothelial cells. However, M. tuberculosis is one of a small group of bacteria that contain multiple genes encoding Cpn 60 proteins. We have now cloned and expressed both M. tuberculosis proteins and report that the novel chaperonin 60, Cpn 60.1, is a more potent inducer of cytokine synthesis than is Cpn 60.2. This is in spite of 76% amino acid sequence similarity between the two mycobacterial chaperonins. The M. tuberculosis Cpn 60.2 protein activates human peripheral blood mononuclear cells by a CD14-independent mechanism, whereas Cpn 60.1 is partially CD14 dependent and contains a peptide sequence whose actions are blocked by anti-CD14 monoclonal antibodies. The cytokine-inducing activity of both chaperonins is extremely resistant to heat. Cpn 60.1 may be an important virulence factor in tuberculosis, able to activate cells by diverse receptor-driven mechanisms.

Mycobacterium tuberculosis Rv2224c modulates innate immune responses

“…Although it is unlikely to be the only target of Rv2224c, GroEL2 has been implicated in modulating proinflammatory cytokine responses in macrophages, which is consistent with our observations of dampened inflammatory milieu (Fig. 5C) (14,19,20). A detailed analysis of Rv2224c enzymatic activity toward GroEL2 and additional physiological substrates should help elucidate the precise biochemical function of Rv2224c.…”

“…6A) (15,16). GroEL2 is induced by heat, nutrient starvation, hypoxia, phagocytosis, and reactive oxygen radicals and is shown to modulate macrophage cytokine responses (14,(17)(18)(19)(20). We sought to further delineate the role of Rv2224c in GroEL2 cleavage by structure-function analysis of the Rv2224c protein.…”

Unfolding the relationship between secreted molecular chaperones and macrophage activation states

“…Indeed, one of the first reports of the signalling actions of molecular chaperones was that the M. tuberculosis Hsp60.2 protein activated human monocytes to synthesise pro-inflammatory cytokines (Friedland et al 1993). Both proteins, when used in vitro at microgram per milliliter concentrations stimulate human monocytes to secrete a range of pro-inflammatory cytokines (Lewthwaite et al 2001). These findings suggest that the M. tuberculosis chaperonins are inducers of the classically activated state.…”

Endocytosis of Mycobacterium tuberculosis Heat Shock Protein 60 Is Required to Induce Interleukin-10 Production in Macrophages*

“…Several microbial heat shock proteins (HSPs) have been demonstrated to modulate the macrophage effector function by inducing various cytokines in both TLR-dependent and -independent ways in addition to their classical chaperonin functions (22)(23)(24)(25)(26)(27). Among the M. tuberculosis heat shock proteins, HSP65 and HSP70 were found to induce pro-inflammatory cytokines in human dermal endothelial cells in TLR2-and TLR4-dependent ways (28).…”