Biology subjects

Bumba, L.

Publications and source records attributed to Bumba, L..

4 recordsLinked to original sources

bioRxiv2026

C-terminal domain of the filamentous hemagglutinin FhaB is crucial for interaction of Bordetella pertussis with ciliated epithelial cells

Bordetella pertussis, the causative agent of whooping cough, produces a [~]370 kDa filamentous hemagglutinin FhaB that serves as a major bacterial adhesin in airway infection. FhaB is secreted via a two-partner secretion pathway and under in vitro culture conditions it is proteolytically processed to the shed [~]230 kDa FHA antigen used currently in acellular pertussis vaccines. We show that FhaB remains largely unprocessed during B. pertussis adhesion to ciliated airway epithelial cells and that its C-terminal domain (CT) is essential for the adhesin function of FhaB. CT deletion did not affect FhaB folding, secretion, or surface exposure, but abolished B. pertussis adhesion to primary human nasal ciliated epithelial cells, thus preventing bacterial colonization of the nasal mucosa and shedding and transmission of the pathogen in a murine nasal infection model. In situ cryo-electron tomography revealed a structural reorganization of the FhaB filaments upon contact with the cilia, presumably due to export of the CT from bacterial periplasm and its subsequent delivery across the ciliary membrane. These findings establish the CT of FhaB as a critical determinant of upper airway colonization by B. pertussis and identify the unprocessed FhaB as the biologically relevant adhesin form involved in airway infection. The revised model of FhaB biogenesis underpins its unique mode of action in pertussis pathogenesis and makes the CT domain to a candidate antigen for future pertussis vaccines.

microbiology↗

bioRxiv2025

Bacteria deliver a microtubule-binding protein into mammalian cells to promote colonization

Pathogenic Bordetella bacteria infect the ciliated respiratory epithelia of mammalian and avian hosts. Several bacterial proteins mediate host cell adhesion, but filamentous hemagglutinin (FhaB) is a principal adhesin because mutants lacking this protein exhibit profound colonization defects. Here, we show that FhaB carries a C-terminal microtubule-binding domain (FhaB-CT), which is translocated into the host-cell cytoplasm to promote bacterial colonization. Cryogenic electron microscopy of microtubule-bound FhaB-CT shows that the domain binds primarily to -tubulin through a network of polar interactions. Live-cell microscopy of infected tracheal explants reveals that FhaB-CT delivery is required for Bordetella to occupy a niche at the base of cilia on airway epithelia. Finally, we demonstrate that the microtubule-binding domain is required for long-term colonization of the mouse nasal cavity by B. pertussis. These observations suggest that the FhaB-CT domain is delivered into motile cilia, where it interacts with axonemal microtubules. We propose that Bordetella initially adhere to the tips of cilia, then deploy multiple FhaB adhesin molecules to migrate to the base of the cilial forest. This mechanism enables Bordetella to resist removal by the mucociliary escalator that clears the respiratory tract of microbes and debris.

microbiology↗

bioRxiv2022

The AAA+ ATPase RavA and its binding partner ViaA modulate E. coli aminoglycoside sensitivity through interaction with the inner membrane

Enteric bacteria have to adapt to environmental stresses in the human gastrointestinal tract such as acid and nutrient stress, oxygen limitation and exposure to antibiotics. Membrane lipid composition has recently emerged as a key factor for stress adaptation. The E. coli ravA-viaA operon is essential for aminoglycoside bactericidal activity under anaerobiosis but its mechanism of action is unclear. Here we characterise the VWA domain-protein ViaA and its interaction with the AAA+ ATPase RavA, and find that both proteins localise at the inner cell membrane. We demonstrate that RavA and ViaA target specific phospholipids and subsequently identify their lipid-binding sites. We further show that mutations abolishing interaction with lipids restore induced changes in cell membrane morphology and lipid composition. Finally we reveal that these mutations render E. coli gentamicin-resistant under fumarate respiration conditions. Our work thus uncovers a ravA-viaA-based pathway which is mobilised in response to antibiotics under anaerobiosis and has a major impact on cell membrane regulation.

microbiology↗

bioRxiv2020

Lipid binding by N-terminal motif mediates plasma membrane localization of Bordetella effector protein BteA

The classical Bordetella species, B. pertussis and B. bronchiseptica, employ a type III secretion system (T3SS) to inject a 69-kDa BteA effector into the host cells. Upon injection, BteA localizes to the cytosolic leaflet of lipid rafts via its N-terminal lipid raft targeting (LRT) domain and induces cell death. The plasma membrane targeting and cytotoxicity mechanisms of BteA are poorly understood. Using protein-lipid overlay assay and surface plasmon resonance, we showed here that the recombinant LRT domain, which adopts a four-helix bundle topology of membrane localization domains, specifically binds negatively charged membrane phospholipids. The binding affinity for phosphatidylinositol 4,5-bisphosphate (PIP2)-containing liposomes with Kd ~450 nM was higher than for those enriched in phosphatidylserine (Kd ~1.2 M) while both phospholipids were required for plasma membrane targeting in yeast cells. The membrane association of LRT further depended on its electrostatic and hydrophobic interactions and involved a loop L1-located leucine residue. Importantly, charge-reversal substitutions within the L1 region disrupted plasma membrane localization of BteA effector without hampering its cytotoxic activity during B. bronchiseptica infection of HeLa cells. The LRT-mediated targeting of BteA to the cytosolic leaflet of the plasma membrane of host cells is, hence, dispensable for the effector cytotoxicity. Author summaryThe respiratory pathogens of humans and other animals, Bordetella pertussis and Bordetella bronchiseptica, produce a type III secretion system effector protein BteA. This effector consists of two functional domains, an N-terminal lipid raft targeting (LRT) domain, and a cytotoxic C-terminal domain, which induces non-apoptotic and caspase-1-independent host cell death. We found here that the LRT domain of BteA associates with plasma membrane by binding to negatively charged phospholipids. We further discovered that the mechanism of membrane association by LRT is reminiscent of the one used by three other diverse families of toxins: clostridial glucosyltransferase toxins, multifunctional-autoprocessing RTX toxins (MARTX), and Pasteurella multocida-like toxins. Intriguingly, we also report that plasma membrane targeting by the LRT domain does not contribute to cytotoxic activity of BteA during B. bronchiseptica infection. Overall, our work elucidated the mechanism of plasma membrane association by LRT, and further provided the basis for future research on cellular activities of BteA and the mechanism of BteA-induced cell death.

microbiology↗