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Hirsutellin A: A Paradigmatic Example of the Insecticidal Function of Fungal Ribotoxins.

Herrero-Galán E, García-Ortega L, Olombrada M, Lacadena J, Del Pozo ÁM, Gavilanes JG, Oñaderra M - Insects (2013)

Bottom Line: Thus, the consideration of hirsutellin A, an insecticidal protein, as a singular ribotoxin recalled the idea of the biological activity of these toxins as insecticidal agents.Further studies have demonstrated that the most representative member of the ribotoxin family, α-sarcin, also shows strong toxic action against insect cells.The aim of this review is to serve as a compilation of the facts that allow identification of HtA as a paradigmatic example of the insecticidal function of fungal ribotoxins.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, 28040 Madrid, Spain. eherrero@cnb.csic.es.

ABSTRACT
The fungal pathogen Hirsutella thompsonii produces an insecticidal protein named hirsutellin A (HtA), which has been described to be toxic to several species of mites, insect larvae, and cells. On the other hand, on the basis of an extensive biochemical and structural characterization, HtA has been considered to be a member of the ribotoxins family. Ribotoxins are fungal extracellular ribonucleases, which inactivate ribosomes by specifically cleaving a single phosphodiester bond located at the large rRNA. Although ribotoxins were brought to light in the 1960s as antitumor agents, their biological function has remained elusive. Thus, the consideration of hirsutellin A, an insecticidal protein, as a singular ribotoxin recalled the idea of the biological activity of these toxins as insecticidal agents. Further studies have demonstrated that the most representative member of the ribotoxin family, α-sarcin, also shows strong toxic action against insect cells. The determination of high resolution structures, the characterization of a large number of mutants, and the toxicity assays against different cell lines have been the tools used for the study of the mechanism of action of ribotoxins at the molecular level. The aim of this review is to serve as a compilation of the facts that allow identification of HtA as a paradigmatic example of the insecticidal function of fungal ribotoxins.

No MeSH data available.


Related in: MedlinePlus

(a)Galleria mellonella larvae; (b) Histogram representing the survival of G. mellonella larvae after ten days of being injected with 8 μL of 0.9% NaCl containing different (μM) concentrations of wild-type α-sarcin, a catalytically inactive mutant (H137Q) or wild-type HtA. The initial number of individuals in each group represented was 15. Results correspond to the average of three independent experiments. Bars represent the standard deviation error.
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insects-04-00339-f005: (a)Galleria mellonella larvae; (b) Histogram representing the survival of G. mellonella larvae after ten days of being injected with 8 μL of 0.9% NaCl containing different (μM) concentrations of wild-type α-sarcin, a catalytically inactive mutant (H137Q) or wild-type HtA. The initial number of individuals in each group represented was 15. Results correspond to the average of three independent experiments. Bars represent the standard deviation error.

Mentions: The insecticidal activity of hirsutellin has been well documented [29]. However, no proven data of this activity have been obtained for any of the other members of the ribotoxin family although some studies had suggested that insecticidal activity could be the natural function of ribotoxins [17,18]. Therefore, a study comparing HtA and α-sarcin has been recently performed with the goal of elucidating this idea [31]. The results obtained show that both α-sarcin and hirsutellin A are highly toxic against G. mellonella larvae (Figure 5). Injection of α-sarcin or HtA caused larvae death and pupation delay. Virulence was dependent on ribotoxin concentration. Data analysis revealed that there was statistically significant difference between the treatment with α-sarcin and HtA, being HtA more effective in terms of less amount of protein needed to produce the same death levels. Indeed, injection of the catalytically inactive α-sarcin H137Q mutant [56] had an almost negligible effect on survival for identical incubation times and doses, correlating toxicity with the ribonucleolytic activity of these proteins.


Hirsutellin A: A Paradigmatic Example of the Insecticidal Function of Fungal Ribotoxins.

Herrero-Galán E, García-Ortega L, Olombrada M, Lacadena J, Del Pozo ÁM, Gavilanes JG, Oñaderra M - Insects (2013)

(a)Galleria mellonella larvae; (b) Histogram representing the survival of G. mellonella larvae after ten days of being injected with 8 μL of 0.9% NaCl containing different (μM) concentrations of wild-type α-sarcin, a catalytically inactive mutant (H137Q) or wild-type HtA. The initial number of individuals in each group represented was 15. Results correspond to the average of three independent experiments. Bars represent the standard deviation error.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4553468&req=5

insects-04-00339-f005: (a)Galleria mellonella larvae; (b) Histogram representing the survival of G. mellonella larvae after ten days of being injected with 8 μL of 0.9% NaCl containing different (μM) concentrations of wild-type α-sarcin, a catalytically inactive mutant (H137Q) or wild-type HtA. The initial number of individuals in each group represented was 15. Results correspond to the average of three independent experiments. Bars represent the standard deviation error.
Mentions: The insecticidal activity of hirsutellin has been well documented [29]. However, no proven data of this activity have been obtained for any of the other members of the ribotoxin family although some studies had suggested that insecticidal activity could be the natural function of ribotoxins [17,18]. Therefore, a study comparing HtA and α-sarcin has been recently performed with the goal of elucidating this idea [31]. The results obtained show that both α-sarcin and hirsutellin A are highly toxic against G. mellonella larvae (Figure 5). Injection of α-sarcin or HtA caused larvae death and pupation delay. Virulence was dependent on ribotoxin concentration. Data analysis revealed that there was statistically significant difference between the treatment with α-sarcin and HtA, being HtA more effective in terms of less amount of protein needed to produce the same death levels. Indeed, injection of the catalytically inactive α-sarcin H137Q mutant [56] had an almost negligible effect on survival for identical incubation times and doses, correlating toxicity with the ribonucleolytic activity of these proteins.

Bottom Line: Thus, the consideration of hirsutellin A, an insecticidal protein, as a singular ribotoxin recalled the idea of the biological activity of these toxins as insecticidal agents.Further studies have demonstrated that the most representative member of the ribotoxin family, α-sarcin, also shows strong toxic action against insect cells.The aim of this review is to serve as a compilation of the facts that allow identification of HtA as a paradigmatic example of the insecticidal function of fungal ribotoxins.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, 28040 Madrid, Spain. eherrero@cnb.csic.es.

ABSTRACT
The fungal pathogen Hirsutella thompsonii produces an insecticidal protein named hirsutellin A (HtA), which has been described to be toxic to several species of mites, insect larvae, and cells. On the other hand, on the basis of an extensive biochemical and structural characterization, HtA has been considered to be a member of the ribotoxins family. Ribotoxins are fungal extracellular ribonucleases, which inactivate ribosomes by specifically cleaving a single phosphodiester bond located at the large rRNA. Although ribotoxins were brought to light in the 1960s as antitumor agents, their biological function has remained elusive. Thus, the consideration of hirsutellin A, an insecticidal protein, as a singular ribotoxin recalled the idea of the biological activity of these toxins as insecticidal agents. Further studies have demonstrated that the most representative member of the ribotoxin family, α-sarcin, also shows strong toxic action against insect cells. The determination of high resolution structures, the characterization of a large number of mutants, and the toxicity assays against different cell lines have been the tools used for the study of the mechanism of action of ribotoxins at the molecular level. The aim of this review is to serve as a compilation of the facts that allow identification of HtA as a paradigmatic example of the insecticidal function of fungal ribotoxins.

No MeSH data available.


Related in: MedlinePlus