Bordetella Adenylate Cyclase Toxin Elicits Airway Mucin Secretion through Activation of the cAMP Response Element Binding Protein

Abstract

The mucus layer protects airway epithelia from damage by noxious agents. Intriguingly, Bordetella pertussis bacteria provoke massive mucus production by nasopharyngeal epithelia during the initial coryza-like catarrhal stage of human pertussis and the pathogen transmits in mucus-containing aerosol droplets expelled by sneezing and post-nasal drip-triggered cough. We investigated the role of the cAMP-elevating adenylate cyclase (CyaA) and pertussis (PT) toxins in the upregulation of mucin production in B. pertussis-infected airway epithelia. Using human pseudostratified airway epithelial cell layers cultured at air–liquid interface (ALI), we show that purified CyaA and PT toxins (100 ng/mL) can trigger production of the major airway mucins Muc5AC and Muc5B. Upregulation of mucin secretion involved activation of the cAMP response element binding protein (CREB) and was blocked by the 666-15-Calbiochem inhibitor of CREB-mediated gene transcription. Intriguingly, a B. pertussis mutant strain secreting only active PT and producing the enzymatically inactive CyaA-AC– toxoid failed to trigger any important mucus production in infected epithelial cell layers in vitro or in vivo in the tracheal epithelia of intranasally infected mice. In contrast, the PT– toxoid-producing B. pertussis mutant secreting the active CyaA toxin elicited a comparable mucin production as infection of epithelial cell layers or tracheal epithelia of infected mice by the wild-type B. pertussis secreting both PT and CyaA toxins. Hence, the cAMP-elevating activity of B. pertussis-secreted CyaA was alone sufficient for activation of mucin production through a CREB-dependent mechanism in B. pertussis-infected airway epithelia in vivo.

Selective Enhancement of the Cell-Permeabilizing Activity of Adenylate Cyclase Toxin Does Not Increase Virulence of Bordetella pertussis

“…The adenylate cyclase toxin (CyaA) belongs to the key virulence factors produced by B. pertussis and plays an important role in the early stages of respiratory tract infection [ 1 , 2 , 5 , 6 , 7 , 8 , 9 ]. CyaA is a 1706 residues-long polypeptide consisting of an N-terminal adenylate cyclase (AC) enzyme domain (~384 residues) and a pore-forming RTX (Repeats in ToXin) hemolysin (Hly) moiety (~1322 residues) [ 8 , 10 , 11 , 12 ].…”

Filamentous Hemagglutinin of Bordetella pertussis Does Not Interact with the β2 Integrin CD11b/CD18

“…B. pertussis attaches to the ciliated cells of respiratory epithelia and elicits increased mucus secretion, infiltration of inflammatory cells, and local tissue damage [ 1 , 2 , 4 ]. The bacterium is a particularly well-equipped pathogen that produces a number of virulence factors, comprising two potently immunosuppressive protein toxins, the pertussis toxin (PT) and the adenylate cyclase toxin-hemolysin (CyaA, ACT or AC-Hly), several adhesins, numerous autotransporter proteins and complement resistance factors, which play important roles in the pathogenesis of pertussis [ 1 , 2 , 5 , 6 ].…”