Determining how sub-cellular localisation of interleukin-1alpha regulates immunity.

Inflammation is a response of the body to danger, such as an infection. During inflammation the immune system is activated and innate immune cells such as macrophages are alerted to remove the specific danger, for example a virus, and restore health. Inflammation is dysregulated with aging as well as during many diseases. Hence it is very important that we understand the basic mechanisms that control inflammation. Macrophages are important cells in the inflammatory process as they produce molecules that coordinate other immune cells to fight infection. The most important of these molecules are called cytokines.

This project will investigate the role of the cytokine Interleukin-1alpha. This interleukin is unique, in that it has a nuclear localisation sequence, that allows it to move between the cytosol and the nucleus of the cell. We believe that this allows this cytokine to play a dual role during inflammation, and infection. First, we think trafficking to the nucleus prevents unnecessary release of this cytokine, preventing an excessive and unwanted inflammatory response. Second, we propose that interleukin-1alpha plays a role in controlling production of other molecules produced by macrophages that are important for inflammation and its resolution.

To investigate these hypotheses, we have generated a mouse in which interleukin-1alpha cannot enter the nucleus allowing us to differentiate the inflammatory response from these mice, and mice that have a normal interleukin-1alpha. Also, we have established a technique to detect molecules that are very close to interleukin-1alpha and that could therefore regulate its activity. This research will uncover new ways by which this cytokine is regulated and new molecules that are important for inflammation. This will be very interesting as it will result in new knowledge on mechanisms of defence against infection that might also be applicable to other areas of research such as aging or disease.

Inflammation is an essential host response to infection and injury, and a contributor to the ageing process. Cytokines can be pro- or anti-inflammatory, and their balance and function is critical for a healthy immune system. Members of the interleukin-1 (IL-1) cytokine family, namely IL-1a and IL-1B, are crucial pro-inflammatory molecules which are central to host responses to infection, but which also cause tissue injury when activated in disease. Both cytokines are produced as precursor molecules, activated by cleavage, and bind to the same receptor (IL-1R1). However, the regulation of their activation and release is different and they can play different roles in inflammation, for instance during infection. An important feature of pro-IL-1a, not present in pro-IL-1B, is a nuclear localization sequence (NLS) in the N-terminus that allows localization to the nucleus. However, it is still not clear what the impact of the nuclear localization of this cytokine is on the immune response, mainly due to a lack of appropriate tools to perform these studies until now.

Here we propose that nuclear localization of pro-IL-1a represents a sub-cellular regulatory mechanism that limits IL-1a processing and release, and that is also important for the control of gene expression involved in inflammatory responses. Thus, the overall aim of this proposal is to understand how sub-cellular localization of pro-IL-1a influences its activity and function, and the impact this has during viral infection. To address this, we will use a multidisciplinary and unbiassed approach applying new and unique tools that combine the use of in vitro and in vivo models. This research will uncover new biological processes and potential targets that control inflammation and could be manipulated to restore health when needed, for instance during viral infections which constitutes an increased risk in the elderly.