Burkholderia cenocepacia BC2L-C Is a Super Lectin with Dual Specificity and Proinflammatory Activity

Abstract

Lectins and adhesins are involved in bacterial adhesion to host tissues and mucus during early steps of infection. We report the characterization of BC2L-C, a soluble lectin from the opportunistic pathogen Burkholderia cenocepacia, which has two distinct domains with unique specificities and biological activities. The N-terminal domain is a novel TNF-α-like fucose-binding lectin, while the C-terminal part is similar to a superfamily of calcium-dependent bacterial lectins. The C-terminal domain displays specificity for mannose and l-glycero-d-manno-heptose. BC2L-C is therefore a superlectin that binds independently to mannose/heptose glycoconjugates and fucosylated human histo-blood group epitopes. The apo form of the C-terminal domain crystallized as a dimer, and calcium and mannose could be docked in the binding site. The whole lectin is hexameric and the overall structure, determined by electron microscopy and small angle X-ray scattering, reveals a flexible arrangement of three mannose/heptose-specific dimers flanked by two fucose-specific TNF-α-like trimers. We propose that BC2L-C binds to the bacterial surface in a mannose/heptose-dependent manner via the C-terminal domain. The TNF-α-like domain triggers IL-8 production in cultured airway epithelial cells in a carbohydrate-independent manner, and is therefore proposed to play a role in the dysregulated proinflammatory response observed in B. cenocepacia lung infections. The unique architecture of this newly recognized superlectin correlates with multiple functions including bacterial cell cross-linking, adhesion to human epithelia, and stimulation of inflammation.

Structure of the Chlamydia trachomatis Immunodominant Antigen Pgp3

“…The Bc2L-C TNF-␣-like domains trigger inerleukin-8 production in cultured airway epithelial cells in a carbohydrate-independent manner and are proposed to play a role in the deregulated proinflammatory response observed in B. cenocepacia lung infections (60), suggesting a given TNF-like trimer can perform more than one function. Full-length and CTD Pgp3 constructs containing an His 8 tag were screened against ϳ460 distinct mammalian glycans in chip-based glycan array experiments, but both were negative for glycan binding (data not shown).…”

Fucose-binding Lectin from Opportunistic Pathogen Burkholderia ambifaria Binds to Both Plant and Human Oligosaccharidic Epitopes

“…protein receptors with high specificity for glycoconjugates, to recognize and adhere to human tissues (12,13). More particularly, fucosylated glycoconjugates are present in higher quantity in CF lungs (14) and appear to be a target for lectins from pathogenic bacteria such as Pseudomonas aeruginosa (15) and Burkholderia cenocepacia (16,17). Fucosylated glycans are also present in plant cell walls and can act as targets for bacterial receptors (18).…”

Synthesis and Characterization of Linker‐Armed Fucose‐Based Glycomimetics

“…The interaction of the glycomimetics with FITC-labeled fucose-binding lectins was tested at different protein concentrations [ Figure 6a (0.001 mg/mL of protein) and Figure 6b (0.01 mg/mL of protein)]. After incubation with plant lectin from Ulex europaeus [23] as well as bacterial lectins LecB (PA-IIL), [24] RSL, [25] and BC2LC-Nt, [26] intense binding-signals for the interaction of 24 and 25 with RSL were detected at the lowest tested protein concentration of 0.001 mg/mL (Figure 6, a). Isothermal calo- Figure 5.…”