An Investigation of the Intracellular Trafficking of Two Pathological Proteins

Download or read book An Investigation of the Intracellular Trafficking of Two Pathological Proteins written by Kathleen FitzGerald and published by . This book was released on 2004 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Endocytosis is a process whereby cargo is transported to and from the plasma membrane, and between organelles, in membrane-bound vesicles. The HIV encoded Nef protein is immunosuppressive and substantially contributes to the overall state of immune dysfunction associated with acquired immune deficiency syndrome. The pathological Nef protein has been implicated in modifying the receptor-mediated endocytic pathway. The transmissible spongiform encephalopathies caused by the infectious prion protein from a group of fatal neurodegenerative disorders that affect both animals and human. The trafficking of the prion protein is considered to play an essential role in its pathogenic conversion while the route and mechanism of the pathological prion protein remain controversial. The objective of this work was to investigate the intracellular trafficking of these two pathological proteins, Nef and prion, with emphasis on the localization and effects of Nef on proteins associated with the receptor-mediated endocytic pathway and emphasis on the cellular trafficking of the prion protein. Nef localizes primarily to the early sorting endosome and shows dramatic effects on the redistribution of the recycling compartment-associated proteins, Rab 11 and REM-1. Expression of the Nef mutant E160A, which is disrupted in its' ability to recruit the adaptor protein complex AP-3, resulted in a redistribution of the Rab11-positive compartment while having no effect on the localization of the RME-1 positive tubules. In contrast, expression of the Nef mutant LL164/165AA, which is disrupted in its' ability to recruit AP-1 and AP-3, results in a normal recycling compartment phenotype. These results suggest that Nefs' effect on the receptor-mediated endocytic pathway relies on its' ability to interact with adaptor protein complexes. A proportion of the pathological prion protein localized to the Rab4-positive early sorting endosome and recycling compartment. Analysis of the Rab4-positive compartment revealed that the form of the prion protein present was unglycosylated. Subsequently it was shown that trafficking of the prion protein through the caveolar pathway converged with the receptor-mediated endocytic pathway. The cause and significance of two distint pathways converging, with respect to prion protein trafficking, remains to be determined. This work raises the possibility that conversion may take place in the Rab4-positive compartment as it is consistent with previous data stating that conversion from normal to infectious prion protein takes place in an acidic environment similar to that found in endosomes and that conversion of the prion protein favours the unglycosylated form of the protein.