Studies on the Mode of Action of Diphtheria Toxin

Abstract

PLATES 110 ZO 112 (Received for publication 5 August 1966)The factor which confers virulence to specific strains of Corynebacterium dipktheriae is the capacity to synthesize a protein exotoxin in the naso-pharyngeal tissues of infected individuals. The protein toxin has been purified and crystallized and has been characterized extensively both chemically and immunologically (1-3). These studies however have not contributed to an understanding of either the chemical moiety responsible for toxicity or to elucidation of the biochemical mode of action of diphtheria toxin. Presently, hypotheses concerning the biological action of the toxin are based primarily on information derived from tissue culture systems. Indeed, the beautiful experiments of Pappenheimer and Williams (4), who utilized the developing cecropia silkworm as the experimental animal, which pointed to the inhibition of tissue cytochrome systems as the mode of action of the toxin, had to be reevaluated in the light of tissue culture experiments which followed. Strauss and Hendee (5) made the initial significant observation that diphtheria toxin when incubated with HeLa cell cultures caused a virtual cessation of protein synthesis as measured by the incorporation of S~5-methionine into cell proteins. Inhibition of de novo synthesis moreover, occurred several hours before any evidence of the toxin's cytopathic effect became manifest. In view of the fact that the metabolism of HeLa cells (derived from a human neoplasm) is primarily glycolytic in nature, the complete inhibition of protein synthesis by the toxin could not be explained solely by an effect on the aerobic respiratory chain of which the cytochrome system is an integral part. Subsequent experiments by Collier and Pappenheimer (6) who used cell-free protein-synthesizing systems, provided unequivocal evidence that the toxin inhibited de novo protein synthesis mediated by both natural and synthetic messenger RNA. They concluded that cells sensitive *

Action of Diphtheria Toxin in the Guinea Pig

“…Within a few hours the label has been found in all tissues examined (except nerve and brain) and, contrary to the findings of Bonventre and his co-workers (8,9), we have observed a marked reduction in amino acid incorporation in all tissues where label can be found. In the tissues of both intoxicated guinea pigs and rabbits the diminished capacity to synthesize protein has been found to be associated with a reduction in T2 content.…”

Studies on the Mode of Action of Diphtheria Toxin

“…We may now ask the question: Can this same mechanism be used to explain the inhibition by toxin of amino acid incorporation by living cells in tissue culture, and can it eventually be extended so as to explain the lethal action of toxin when injected into susceptible animals? With regard to the latter question, the recent results reported by Bonventre and Imhoff (21) suggest that the answer may be exceedingly complex. Using radioautograms and incorporation of isotopes into tissue proteins, only the heart and the pancreas showed marked inhibition in intoxicated guinea pigs.…”

Immunoprecipitation and partial characterization of diphtheria toxin-binding glycoproteins from surface of guinea pig cells.

“…Values were corrected for 125I crossover into the 3H channel. RESULTS Guinea pigs are extremely sensitive to the effects of DT (1,19,20). Furthermore, guinea pig lymphoid tissue has been demonstrated to be sensitive to the toxic effects of DT in vitro (20).…”