NAD-dependent inhibition of protein synthesis by Pseudomonas aeruginosa toxin,.

Abstract

Pseudomonas aeruginosa toxin (PA toxin) inhibits protein synthesis in a reticulocyte cell-free system. The inhibition requires NAD and results in a block at an elongation step of polypeptide assembly. PA Pseudomonas aeruginosa produces a variety of extracellular substances (1-11). Although the role of each of these substances in the pathogenesis of pseudomonas infections in humans is poorly understood, the most likely virulence factor is the trypsin-sensitive, heat-labile protein exotoxin (PA toxin) originally described by Liu (3). PA toxin in very low concentrations produces hypotensive shock in dogs (6) and monkeys (12) and is lethal for mice (4). Furthermore, passive immunization with antibody produced against PA toxin prevents the lethal effects of infection with live cultures of Pseudomonas aeruginosa (13).Previous data suggest that PA toxin inhibits RNA and protein synthesis in cultured mammalian cells (14) and protein synthesis in the liver, kidney, and spleen of intoxicated mice (15). Protein synthesis in cultured 3T3 mouse cells is inhibited by 2 hr incubation with as little as 0.02 jug/ml of PA toxin, whereas at this concentration RNA synthesis is not inhibited until 4-5 hr incubation (L. P. Elwell and B. H. Iglewski, unpublished observations). However, the sequence of events by which PA toxin inhibits protein synthesis has not been established and it is not known whether the inhibition is a primary or secondary effect of PA toxin action.This report describes the NAD-dependent inhibitory effect of PA toxin on protein synthesis in a rabbit reticulocyte cellfree lysate and identifies an enzymatic activity of PA toxin which appears to be similar to the NAD-dependent ADPribosyl transferase activity which has been established for the A-fragment of diphtheria toxin (16-18). In both cases elongation factor 2 (EF-2) is covalently modified and thereby inactivated. However, the two toxins are dissimilar in cellular specificities, molecular and immunological properties, and in the diseases for which they are apparently responsible. METHODS AND MATERIALSToxin and Antisera. A nonproteolytic strain of Pseudomonas aeruginosa (PA-103) kindly provided by P. V. Liu (19) was used throughout this study. PA toxin purified by precipitations with zinc acetate and (NH4)2SO4 and chromatographed on columns of DEAE-cellulose and Sephadex G-200 (20) Abbreviations: PA toxin, Pseudomonas aeruginosa toxin; EF-2, elongation factor 2.

Experimental infections with protease-deficient mutants of Pseudomonas aeruginosa in mice (Plate VIII)

“…The histopathological changes are not specific for the toxin but are produced, for example, by agents interfering with protein synthesis of the liver (Lombardi, 1966). Exotoxin A and diphtheria toxin inhibit protein synthesis in mammalian cells by the same mechanism (Iglewski and Kabat, 1975). Similar changes in liver histology have been described for bacteriaemic P .…”

Interspecies competition triggers virulence and mutability in Candida albicans–Pseudomonas aeruginosa mixed biofilms

“…Consistent with a role for pyoverdine as a signaling molecule that controls the production of virulence factors, we observed an increased concentration of Exotoxin A in coculture supernatants (Supplementary Table S3), which is one of the most powerful extracellular virulence factors produced by P. aeruginosa (Iglewski and Kabat, 1975).…”

Pseudomonas aeruginosa mediated apoptosis requires the ADP-ribosylating activity of ExoS

“…To successfully colonize and maintain an infectious cycle the organism carefully orchestrates production of a suite of virulence determinants including pili (Hahn, 1997 ;Wall & Kaiser, 1999) and non-pilus adhesins (Simpson et al, 1995), extracellular enzymes (Ohman et al, 1980 ;Salyers & Whitt, 1994), and exotoxins (Iglewski & Kabat, 1975). Some virulence factors are produced and secreted directly into the host cell using the cell-contact-mediated type III secretion machinery.…”