Two secretory T2 RNases from a fungal pathogen target distinct insect cell transmembrane proteins to cause...

Area of Science:

• Mycology
• Insect Pathology
• Molecular Biology

Background:

• Fungal pathogens secrete ribonuclease T2 (RNase T2) proteins that degrade host RNA, contributing to virulence.
• The mechanism by which these fungal RNase T2 proteins enter host cells remains largely unknown.
• Previous work identified two RNase T2 proteins, BbRNT2 and BbTrv, from Beauveria bassiana that cause cytotoxic damage to insect cells.

Purpose of the Study:

• To investigate the interaction of fungal RNase T2 proteins with insect cells.
• To identify specific insect cell proteins involved in the entry of fungal RNase T2 proteins.
• To elucidate the mechanism of cytotoxic molecule entry during fungal pathogenesis.

Main Methods:

• Utilized Spodoptera frugiperda ovarian epithelial (sf9) cells as an insect cell model.
• Employed protein immunoprecipitation, yeast-two hybrid assays, and protein pull-down assays to identify interacting proteins.
• Used RNA interference to assess the role of identified insect transmembrane proteins in RNase T2 entry.

Main Results:

• Identified two transmembrane proteins, SfABCG (an ABC transporter) and Sfinx (an Innexin 7-like protein), that interact with BbRNT2 and BbTrv, respectively.
• RNA interference of SfABCG or Sfinx significantly reduced insect cell sensitivity to BbRNT2 and BbTrv.
• These findings suggest that SfABCG and Sfinx are crucial for the entry of fungal RNase T2 proteins into insect cells.

Conclusions:

• Fungal RNase T2 proteins enter insect cells by interacting with specific insect cell transmembrane proteins.
• This interaction facilitates the cytotoxic action of fungal RNase T2 proteins, contributing to fungal virulence.
• The study reveals a novel mechanism for the entry of pathogen-secreted cytotoxic molecules into host cells.