Bordetella pertussis adenylate cyclase toxin translocation across a tethered lipid bilayer

Abstract

Significance Many bacterial toxins can cross biological membranes to reach the cytosol of mammalian cells, although how they pass through a lipid bilayer remains largely unknown. Bordetella pertussis adenylate cyclase (CyaA) toxin delivers its catalytic domain directly across the cell membrane. To characterize this unique translocation process, we designed an in vitro assay based on a tethered lipid bilayer assembled over a biosensor surface derivatized with calmodulin, a natural activator of the toxin. CyaA activation by calmodulin provided a highly sensitive readout for toxin translocation across the bilayer. CyaA translocation was calcium- and membrane potential-dependent but independent of any additional eukaryotic protein. This biomimetic membrane will permit in vitro studies of protein translocation in precisely defined conditions.

Engineered nanoparticles mimicking cell membranes for toxin neutralization

“…Employment of this indirect approach is likely due to the fact that direct entry from the cell surface is disruptive and too traumatic of an event. One of the only exceptions to this is adenylate cyclase toxin produced by the bacterium Bordetella pertussis that is responsible for whooping cough; in this case the catalytic domain is translocated across the plasma membrane directly into the cytoplasm [82]. …”

Calcium, Acylation, and Molecular Confinement Favor Folding of Bordetella pertussis Adenylate Cyclase CyaA Toxin into a Monomeric and Cytotoxic Form

“…It is believed that after binding of RD to the CD11b/CD18 receptor, the hydrophobic regions of CyaA may insert into the plasma membrane of the target cells. The catalytic domain is then delivered through the plasma membrane, possibly through a transient and local destabilization of the membrane integrity (8,9,42,43), to reach the cytosol, where, upon binding to the endogenous CaM, its enzymatic activity is stimulated to generate supraphysiologic levels of cAMP (37,44). Moreover, CyaA, after insertion into the membrane, can also form cation-selective pores, which impair membrane impermeability and ultimately cause cell lysis (6,40,45).…”

Structure and function of RTX toxins

“…How CyaA crosses the plasma membrane of the target cells remains largely unknown. The translocation is dependent on calcium, temperature, and negative potential across the target cell membrane [54,55,276,280,[328][329][330], and may involve a transient destabilization of the lipid bilayer by the translocation domain located between AC and the hydrophobic region [320,321]. Interestingly, an atypical entry of CyaA into polarized T84 epithelial cells via their basolateral membranes has been reported [331].…”