Genome-wide RNAi screens identify genes required for Ricin and PE intoxications

Area of Science:

• Cell Biology
• Molecular Toxicology
• Membrane Trafficking

Background:

• Protein toxins like Ricin and Pseudomonas exotoxin (PE) are significant public health threats.
• Both toxins utilize host cell machinery for entry, retrograde transport from endosomes to the ER, and cytosol translocation.
• The specific genetic dependencies of these toxins within shared intracellular pathways remain largely uncharacterized.

Purpose of the Study:

• To identify and compare the genes essential for Ricin and PE intoxication.
• To elucidate the similarities and differences in their intracellular trafficking pathways.
• To understand the complexity of retrograde membrane transport.

Main Methods:

• Conducted two genome-wide RNA interference (RNAi) screens to identify genes critical for intoxication.
• Analyzed gene requirements for both Ricin and PE.
• Utilized morphological analysis and colocalization studies with cellular markers.

Main Results:

• Identified distinct gene requirements for PE and Ricin, with only 13% overlap.
• Found shared factors involved in transport from endosomes to the ER for both toxins.
• Observed that Ricin, unlike PE, requires Golgi complex integrity and colocalizes with medial Golgi markers.

Conclusions:

• Ricin and PE intoxication rely on strikingly different sets of host genes, despite sharing common trafficking steps.
• The intracellular pathways for these toxins appear as intertwined networks that converge and diverge.
• These findings reveal the intricate nature of retrograde membrane trafficking in mammalian cells.