Dissecting the function of Bcl-3 in NF-kB signaling in B cells.

In healthy people, the immune system can recognise, attack and destroy potentially harmful infectious agents wherever they are in the body, while avoiding mounting similar attacks against healthy cells and tissues. However, aberrant or inappropriate immune responses can lead to chronic or overwhelming infection, or contribute to the development of a host of autoimmune or chronic inflammatory diseases, such as Crohn's disease, rheumatoid arthritis, and atherosclerosis. In fact, it is now clear that inflammation and the immune system contribute to virtually all diseases in humans, including cancer and neurodegeneration. Moreover, the accumulation of DNA mutations in cells of the immune system leads to the development of lymphomas and leukaemias. Thus, a thorough knowledge of the immune system and immune cells is of fundamental biological importance, and has the potential to improve our understanding and treatment of a broad spectrum of human diseases.
The biological and pathological processes driven by the immune system are profoundly influenced by how immune cells detect and respond to their environment. 'Molecular signals' received at the surface of immune cells are conveyed to the cell's nucleus where they are integrated and interpreted, leading to alterations in the profile of genes 'expressed' by that cell. This in turn leads to fundamental changes in the molecular constituents of the entire cell, which ultimately determines its biological or pathological function. Arguably the most important molecules regulating immune cell responses in this way are a family of intracellular proteins collectively known as Nuclear Factor kappaB (NF-kB). These proteins are critical for changing gene expression in immune cells in response to a wide variety of molecular signals emanating from either neighbouring cells or from invading pathogenic microorganisms. As a result, they are of fundamental importance in the development, maintenance and function of the immune cells, and contribute to both beneficial and detrimental immune responses.
We are broadly interested in understanding how these complex intracellular processes are orchestrated and regulated, with a view to developing new therapies that manipulate immune cell function to control disease. The current application aims to determine the function of Bcl-3, a protein present in the nucleus of immune cells that is known to influence NF-kB function. Bcl-3 is found in many different types of cells, but it plays particularly prominent roles in the biology of B cells. These are important immune cells because they have the capacity to make antibodies, and antibodies contribute to all beneficial and detrimental immune responses. Bcl-3 controls the survival, proliferation and immune function of B cells, while too much Bcl-3 can lead to the development of B cell-derived lymphomas and leukaemias. However, it is far from clear how Bcl-3 does these things. The work we are proposing exploits and integrates state-of-the-art technologies to examine the importance of Bcl-3 at the molecular, cellular and whole animal level. The results of our study will provide novel and unprecedented insights into how normal and elevated levels of this protein regulate B cell biology, and these findings will have broad physiological and pathological implications. In addition, and importantly, they will provide a firm foundation upon which we can further explore the therapeutic potential of blocking or mimicking Bcl-3 function.

NF-kB transcription factors are essential for immune system development and homeostasis, and are key regulators of innate and adaptive immunity. Two signalling pathways exist that couple the activation of immunoreceptors to NF-kB-dependent changes in gene expression. These are the classical pathway, which involves NF-kB dimers containing p65, c-Rel or p50, and the non-canonical pathway, which produces dimers composed of RelB or p52. These NF-kB dimers bind kB sites in promoters to regulate gene transcription. Despite activating distinct NF-kB dimers, the two pathways share a common nuclear component, Bcl-3, which selectively interacts with, and regulates, homodimers of p50 or p52. Bcl-3 and both NF-kB pathways play prominent roles in the biology of B cells. Bcl-3 deficiency alters B cell proliferation, survival, and TLR responses, while its over-expression drives B cell expansion and is associated with leukaemogenesis. However, the molecular functions of Bcl-3 and p50/p52 homodimers are poorly understood. Based on published studies and preliminary data presented in this proposal, we hypothesise that Bcl-3 is a context-dependent component of both NF-kB signalling pathways that can either repress or activate NF-kB-dependent gene transcription depending on its level of expression, the dimers it is bound to, and the properties of individual target gene promoters. We will rigorously test this hypothesis by employing a broad range of molecular, cellular and whole animal techniques that will provide unprecedented insights into the role of Bcl-3 and NF-kB pathways in immunoreceptor signalling in primary B cells, and reveal the molecular basis for the long recognised, but poorly understood, oncogenicity of Bcl-3 in B cells. Moreover, these insights could inform our ongoing efforts to develop novel Bcl-3-based therapies, which, given the importance of NF-kB in inflammatory disease, autoimmunity, and cancer, could find wide-ranging application in many diseases.

This proposal aims to investigate the role of Bcl-3 in regulating NF-kB in B cells. The data will provide unprecedented insights into how normal and elevated levels of this protein regulate B cell biology, and these findings will have broad physiological and pathological implications. In addition, and importantly, they will provide a firm foundation upon which we can further explore the therapeutic potential of blocking or mimicking Bcl-3 function.

The impact of the proposed research can therefore be identified as follows:

1) Academic
The data from the proposed research will be of importance to academic and private sector researchers both in the UK and internationally, and in a wide range of disciplines including, but not limited to, immunology, cancer biology, cardiovascular biology and neurobiology. The impact of this proposal on UK based researchers will be to advance the knowledge economy. In addition, by communicating the research through our continued teaching and outreach activities we also hope to inform and educate, with impact, other beneficiaries in the University of Glasgow and local communities.

2) Private sector/biotech industry
The proposed research will investigate the molecular mechanisms controlling context specific NF-kB transcriptional activity, which is critical for any potential exploitation of NF-kB for therapeutic benefit. We are actively developing Bcl-3 mimetic agents with the aim of testing their therapeutic potential. The data from this proposal will be of benefit in assessing the immunomodulatory effects of such compounds with potential for attracting R&D investment and developing intellectual property in this area.

3) Economic and societal impact
NF-kB is intimately linked to the pathology of a wide range of diseases with profound social and economic consequences. These include chronic inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease and autoimmunity, as well as cancer, atherosclerosis and neurodegenerative disease. This proposal focuses on a fundamental aspect of NF-kB biology that is relevant to the future development of therapies in these areas. Such therapies have the potential to benefit the quality of life, health and well being of UK citizens.

4) Training of researchers at an advanced level
This proposal exploits state-of-the-art techniques in transcription factor analysis, including the use of next generation sequencing and chromatin immunoprecipitation, integrated with in vivo models of B cell function. The multidisciplinary approach to addressing our research questions offers exceptional opportunities for the training of researchers at an advanced level.