Endocytosis and intracellular transport of protein toxins

Errors in trafficking and signalling are associated with different diseases, including cancer. This project aims at increasing our knowledge about intracellular transport processes to provide a more rational basis for treatment and prevention of disease. Protein toxins such as Shiga toxin and the plant toxin ricin are used as tools to obtain increased knowledge about basic transport mechanisms and signalling, and the toxins are investigated to provide insight into their use in targeted drug delivery. The toxins here investigated act by first binding to cell surface receptors, then they are endocytosed and transported retrogradely to the Golgi apparatus and to the ER, and finally they are translocated to the cytosol (for instance ricin, Shiga toxin, chole ra toxin). The toxins are valuable to study all the steps along their retrograde pathway. They can be used to study different types of endocytosis, the pathways operating between endosomes and the Golgi apparatus, retrograde transport from the Golgi to th e ER and protein translocation across the membrane to the cytosol. Their final action, protein synthesis inhibition, provides us with a sensitive test system for entry into the cytosol, and genetically modified toxins with sulfation sites (sulfation is a Golgi modification) and glycosylation sites (to monitor ER arrival) allow us to quantify intermediary steps. By using a combination of morphological (electron and confocal microscopy), biochemical and molecular biological approaches (for instance antisens e and RNAi technology), we are investigating various aspects of intracellular transport.