The mode of action of hirsutellin A on eukaryotic cells

Abstract

A 16-kDa protein toxin was purified from Hirsutella thompsonii var thompsonii and named hirsutellin A (HtA). At 0.5 and 5.0 microM concentrations, HtA caused detectable cytopathic effects on Spodoptera frugiperda cells (Sf-9) within 2-4 hr and completely inhibited Sf-9 cell growth at 4 days posttreatment. Electron microscope data showed that the HtA treated Sf-9 cells became hypotrophied and internal organelles and cell membranes were disrupted. At the same concentration, HtA effectively inhibited Brome mosaic virus protein synthesis of both rabbit reticulocyte and wheat germ in vitro translation system. The ribosomal RNA extracted from HtA treated Sf-9 cells produced a smaller RNA (approximately 528 bases) than untreated Sf-9 cells. In summary, HtA is the first mycotoxin of a invertebrate mycopathogen determined to possess ribosomal inhibiting activity and appears to possess some specificity to invertebrate cells.

Part of CIRS Nexus · Curated by Lauren Lowenstein, The Biotoxin Lady