Enemy at the gate: a novel mechanism of paracrine stress granule induction by viruses

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Cells within the body respond to external stimuli in many ways, the most common of which is via the regulation of gene expression. In response to stress such as infection, cells can pause protein synthesis, or translation, and thus the decoding of genetic information, by storing messenger RNAs (mRNAs) away in cellular compartments called stress granules. This defence mechanism allows cells to survive by limiting the use of energy and nutrients that protein synthesis requires until the stress is resolved. It also blocks the spread of viruses as they are dependent on host cell resources to produce viral proteins and replicate. Because stress granules also act as sentinels to sense viral attack, viruses have developed strategies to disable their function. Stress granules are also of increasing importance because of recent observations that they are implicated in neurodegenerative diseases such as amyotrophic lateral sclerosis and Alzheimer's disease, as well as resistance to cancer chemotherapy.Caliciviruses are an important family of small viruses that can cause diseases both in humans and animals. In humans they primarily cause gastroenteritis but also cause general and respiratory infections in animals. Using animal caliciviruses, we previously made significant advances in identifying new mechanisms that viruses use to manipulate the host cell and counteract the cell's defence systems. Based on our recent results, we are now proposing that in response to virus infection, a novel mechanism allows uninfected cells to activate stress responses and prepare for viral assault. This mechanism is novel and we think it represents a new line of defence against viruses. Therefore, our objectives are to use a combination of cell biology, virology and biochemical methods to 1- characterise the composition of stress granules assembled in response to infection; understand their role in 2- the remodelling of protein synthesis and 3- the antiviral response, and 4- identify which soluble molecules stimulate this mechanism.From this work we expect to fully understand how viruses regulate the assembly of stress granules, and prime an antiviral state. We can then identify new ways to inhibit virus replication. Therefore, our work will characterise a new mechanism of antiviral response. It will advance our basic knowledge of how stress granules control gene expression and aid in the development of novel antiviral therapies for this important group of viruses, and later other viruses that control stress pathways.