Influence of the endoplasmic reticulum localization sequence on the cytotoxicity of Pseudomonas exotoxin A-based recombinant immunotoxins

Abstract

Recombinant immunotoxins (RITs) are chimeric proteins that are engineered to join an antibody to a protein toxin. The antibody allows for receptor-specific targeting of cells while the toxin is internalized and subsequently induces cell death. One of the most commonly utilized RITs is based on Pseudomonas exotoxin A (PE), a bacterial toxin secreted by Pseudomonas aeruginosa. An important feature of the toxin is a C-terminal endoplasmic reticulum (ER) retention sequence, REDLK, which is analogous to the canonical KDEL found at the C-terminus of ER resident proteins. The goal of this project was to assess how mutations to the ER localization sequence affect cytotoxicity when different fragments of PE are incorporated into RITs. The replacement of REDLK with KDEL and the deletion of REDLK have varying effects on the cytotoxicity of the different PE fragments, and the relative cytotoxicity is further influenced by the cell type and the surface protein target.