Energy-Generating Enzymes ofBurkholderia cepaciaand Their Interactions with Macrophages

Abstract

We previously demonstrated that several clinical and environmental isolates of Burkholderia cepacia secreted ATP-utilizing enzymes to the medium; the secretion of these enzymes by cystic fibrosis lung isolate strain 38 was shown to be greatly enhanced in the presence of ␣ 2 -macroglobulin. Fractionation of the growth medium of cystic fibrosis isolate strain 71 belonging to genomovar I demonstrated the presence of two additional proteins, homologues of Pseudomonas aeruginosa azurin and cytochrome c 551 , which are normally involved in electron transfer during denitrification. A Q-Sepharose column flowthrough fraction of the growth medium of B. cepacia strain 71 enriched with the azurin and cytochrome c 551 homologues triggered apoptosis in macrophages and mast cells, leading to their death. Incubation of the Q-Sepharose column flowthrough fraction with antiazurin and anti-cytochrome c 551 antibodies greatly reduced cell death. We cloned and hyperexpressed a gene from B. cepacia strain 71 that encodes the homologue of P. aeruginosa azurin. Such azurin homologues were detected in the growth medium of several strains belonging to genomovars I, III, and VI but not in the growth medium of strains belonging to other genomovars. The growth medium of the strains that elaborated the azurin homologue had high cytotoxicity towards macrophages. Purified azurin homologue was shown to induce apoptosis in macrophages in a caspase-dependent manner and was localized in both the cytosol and nucleus when incubated with or microinjected into macrophages. This is an interesting example of the interaction of a bacterial protein normally involved in cellular energetics with macrophages to effect their cell death.

New generation of cell‐penetrating peptides: Functionality and potential clinical application

“…Moreover, after intensive studies, the group of Das Gupta patented some azurin fragments with low toxicity for their use in cancer prevention. However, in contrast to this group, Puni et al, 102 found that azurin can induce apoptosis in macrophages in a caspase‐dependent manner. Very recently Sasidharan et al 103 proposed to use azurin and its fragment p28, as anti‐SARS‐CoV‐2 inhibitor.…”

Differential modulation of innate immune cell functions by theBurkholderia cepaciacomplex:Burkholderia cenocepaciabut notBurkholderia multivoransdisrupts maturation and induces necrosis in human dendritic cells

“…Both apoptotic and necrotic cell death have been described in murine macrophages and human neutrophils following exposure to purified secreted BCC enzymes such as hemolysin, ATP-utilizing enzymes, azurin and cytochrome c551 (Hutchison et al, 1998;Melnikov et al, 2000;Punj et al, 2003). In rodent models, extracellular proteases are associated with tissue damage, and the production of at least one zinc metalloprotease is required for virulence (McKevitt et al, 1989;Kooi et al, 2006).…”

“…In rodent models, extracellular proteases are associated with tissue damage, and the production of at least one zinc metalloprotease is required for virulence (McKevitt et al ., 1989; Kooi et al ., 2006). Of particular interest, azurin and ZmpB are secreted by B. cenocepacia but not by B. multivorans (Punj et al ., 2003; Kooi et al ., 2006) . The relevance of those studies to the present one is unclear because, in our investigations, DCs remained viable when exposed to BCC supernatants.…”

“…Indeed, in a murine pulmonary infection model, B. multivorans persists within mononuclear phagocytes in the absence of inflammation, while B. cenocepacia induces greater inflammation and toxicity (Chu et al, 2004). Secreted bacterial products from this group of pathogens also induce apoptosis or necrosis in neutrophils and macrophages (Hutchison et al, 1998;Melnikov et al, 2000;Punj et al, 2003).…”

Outer membrane vesicles produced by Burkholderia cepacia cultured with subinhibitory concentrations of ceftazidime enhance pro-inflammatory responses

“…These results suggest that subinhibitory concentrations of CAZ modulate the biogenesis of OMVs and stimulate the association of cytotoxic factors with B. cepacia OMVs. Azurin homologue in the culture supernatant of B. cepacia and hemolysin from B. cepacia genomovar III were found to be cytotoxic to host cells [49,50]. However, the present study did not determine the cytotoxic factors of B. cepacia OMVs and it is necessary to clarify cytotoxic factors packaged in B. cepacia OMVs and their association with host cell death.…”