Bordetella pertussis tracheal cytotoxin and other muramyl peptides: distinct structure-activity relationships for respiratory epithelial cytopathology.

Abstract

Tracheal cytotoxin (TCT) is a disaccharidetetrapeptide released by Bordetella pertussis, the causative agent of pertussis (whooping cough). We have previously determined the structure of TCT to be GIcNAc-1,6-anhydroMurNAc-L-Ala-y-D-Glu-meso-A2pm-D-Ala, where MurNAc = N-acetylmuramic acid and A2pm = diaminopimelic acid. Purified TCT reproduces the respiratory cytopathology observed during pertussis, including ciliostasis and extrusion of ciliated cells. We have tested structural analogs of TCT for their ability to reproduce native TCT toxicity in explanted hamster tracheal tissue and hamster trachea epithelial (HTE) cell cultures. Other investigators have evaluated many of these analogs, which are muramyl or desmuramyl peptides, for muramyl peptide activities such as immunopotentiation, induction of slow-wave sleep, and pyrogenicity. Four desmuramyl peptides were produced in our laboratory from B. pertussis peptidoglycan or by chemical synthesis, including unusual peptides containing a-aminopimelic acid in place of A2pm. Based on the relative ability of compounds to inhibit DNA synthesis in HTE cells, truncated analogs lacking A2pm entirely or lacking only the side-chain amine or carboxyl group of A2pm were less active than TCT by a factor of at least 1000. All active analogs included a native or near-native peptide moiety, independent of the presence, absence, or substitution of the sugar moiety. We conclude that the structural requirements for TCT toxicity differ considerably from those for most other muramyl peptide activities, in that the disaccharide moiety is irrelevant for toxicity and both the free amino and carboxyl groups of the A2pm side chain are required for activity.Tracheal cytotoxin (TCT) is a low molecular weight glycopeptide released during logarithmic-phase growth of Bordetella pertussis. It is the only B. pertussis product that reproduces the respiratory cytopathology observed during pertussis (whooping cough) (1). This pathology includes ciliostasis and specific extrusion of ciliated cells from the respiratory epithelium. In the absence of ciliary activity, coughing becomes the only way to clear the airways of accumulating mucus, bacteria, and inflammatory debris. Thus, TCT-mediated destruction of ciliated cells may trigger the violent coughing episodes symptomatic of pertussis. In addition, the absence of a ciliary clearance mechanism predisposes patients to secondary pulmonary infections, the primary cause of pertussis mortality (2).We have previously reported the purification of TCT by reversed-phase HPLC (RP-HPLC) and determined its structure by fast atom bombardment (FAB)-MS to be GlcNAc-1,6-anhydro-MurNAc-L-Ala-y-D-Glu-meso-A2pm-D-Ala (Fig. 1) (3), where MurNAc is N-acetylmuramic acid and A2pm is diaminopimelic acid. TCT belongs to a family of compounds known as muramyl peptides, which have many biological activities including adjuvanticity, somnogenicity, and pyrogenicity (4-6). Naturally occurring muramyl peptides are of bacterial origin; they are fragments of peptidoglycan, t...

Peptidoglycan structure of Salmonella typhimurium growing within cultured mammalian cells

“…These changes could be associated with intracellular release of peptidoglycan-derived products, which have profound biological effects on mammalian cells (Burroughs et al, 1993;Luker et al, 1993;. More precisely, action of the amidase on monomeric muropeptides or in 5/5Ј and 6/6Ј muropeptides, would release peptides within the vacuole that S. typhimurium inhabits.…”

“…More precisely, action of the amidase on monomeric muropeptides or in 5/5Ј and 6/6Ј muropeptides, would release peptides within the vacuole that S. typhimurium inhabits. These types of peptides have been shown to be extremely potent in activating mammalian cells (Burroughs et al, 1993;Luker et al, 1993;. If this phenomenon occurs within the intracellular eukaryotic environment, new therapeutic strategies could be designed.…”

Genetic determination of the meso-diaminopimelate biosynthetic pathway of mycobacteria

“…This fact results in an unusually high DAP content in the mycobacterial cell wall. The importance of the DAP molecule has been further suggested by work with Bordetella pertussis, for which DAP has been shown to play a key role in the structure of a cytotoxin (13).…”

Enzyme Degradation and Proinflammatory Activity in Arthritogenic and NonarthritogenicEubacterium aerofaciensCell Walls

“…Stem peptides, also called muramyl peptides, are short peptides of four to five amino acids bound to MurNAc. PG and muramyl peptides possess multiple immune activities (3,17,24,25,42). For instance, PG can bind to CD14 (6) and to Toll-like receptor 2 (36, 51) to stimulate T cells and monocytes to produce inflammatory cytokines, including tumor necrosis factor alpha (TNF-␣), interleukin (IL-8), and monocyte chemoattractant protein 1 (MCP-1) (48, 49), and to cause gram-positive shock (5, 16).…”