Subversion of cellular autophagy by rotavirus

Abstract

Autophagy is a fundamental process which occurs in cells of all known eukaryotic organisms for the lysosomal degradation of cytosolic organelles and macromolecular complexes. The primordial function was thought to represent an adaptation to stress, principally nutrient deprivation, through the regeneration of amino acid pools required for continual protein synthesis. More recently, autophagy has been recognised for its role in the degradation of intracellular pathogens such as viruses. Some viruses have evolved the ability to modulate the autophagic process, either by antagonising the initiation of autophagy or alternatively utilising elements of the autophagic pathway to facilitate their own replication and dissemination. This project investigated how rotavirus may affect the autophagic pathway. The results show a progressive accumulation of autophagosomes following rotavirus infection of a cell line stably expressing GFP-Atg8/LC3, a common marker of autophagosome formation. Rotavirus infection appears to cause an increase in autophagosome formation early in the infection cycle. Further analysis by flow cytometry, western blotting and confocal microscopy demonstrates that later in infection the virus can specifically inhibit the degradation of pre-existing autophagosomes through preventing the fusion of autophagosomes to acidified compartments such as lysosomes, effectively reducing autophagic flux. Chemical inhibition of the autophagic pathway leads to a significant reduction in the titre of rotavirus. Thus the data suggests that rotavirus requires autophagosomes for maximal replication and has evolved a mechanism to increase and maintain autophagosomes in the infected cell to enhance its replication.