Role of Wnk1 kinase in T cell adhesion and migration

White blood cells are a key part of the body's immune system, playing a critical role in combating infections by viruses, bacteria and other pathogens. Our research is focussed on a type white blood cell called a T cell, which can detect the presence of an infectious agent such as a virus inside other cells. We are interested in understanding the mechanism by which a T cell recognises whether another cell contains an infectious agent within it. As part of this process, the T cell and the infected cell have to adhere tightly to each other and we are studying this process of adhesion.

In recent work we have identified that a protein called Wnk1 plays an important role in regulating T cell adhesion, and in the research we are now proposing, we will extend this work by examining how the T cells function when they lack the protein, and whether this makes them defective in contributing to normal immune responses. We suspect that Wnk1 may also control how the T cells migrate through the body. Normal T cells are continuously on the move, trafficking between the blood and lymph nodes and the spleen. This continuous movement is a vital feature of the T cells as it allows them to patrol the body looking for signs of infection. We will investigate this potential function of the Wnk1 protein in controlling T cell migration.

We suspect that Wnk1 functions as a signalling protein, transmitting signals from the surface of the cell to adhesion molecules. We will investigate this hypothesis further by looking for other proteins to which Wnk1 transmits a signal. Overall our aim is to understand how Wnk1 controls T cell adhesion and migration. Such knowledge will reveal new opportunities for the design of rational drugs that could modulate the function of T cells and thereby the whole immune system.

A critical step in the initiation of the adaptive immune response is the activation of T cells by signaling from the T cell antigen receptor (TCR), following binding of the receptor to peptide:MHC complexes on antigen-presenting cells (APCs). This TCR signal results in activation of integrins on the T cell, leading to firm adhesion between the T cell and APC, a process required for full activation. Furthermore, integrins are also regulated by signaling from chemokine receptors, a process that is critical for T cell migration into and through lymphoid organs. Using an RNAi genetic screen in a T cell leukaemic cell line we have identified a number novel of signaling proteins involved in the regulation of integrin function on T cells. One of these is the kinase Wnk1, which has never previously been implicated in T cell function or in the regulation of integrins and thus is an attractive candidate for further studies.

We now propose to analyse the function of Wnk1 in the activation, adhesion and migration of primary T cells. Other studies have shown that Wnk1 is involved in the regulation of ion homeostasis in the kidney through a pathway in which Wnk1 phosphorylates and activates the Spak and Osr1 kinases, which in turn phosphorylate and activate the NKCC1 Na+/K+/Cl- co-transporter. We will investigate if this pathway also operates in primary T cells, whether it is regulated by signals from the TCR, chemokine receptors, or integrins themselves. Using genetic knockout or knockdown we will investigate if Wnk1, Spak, Osr1 and NKCC1 are involved in the adhesion, migration or activation of primary T cells. More broadly, we will evaluate the role of Wnk1 in the transduction of signals from the TCR to integrin activation, focusing on regulation of proteins known to play important functions in this inside-out signalling pathway.

Who will benefit from this research and how?

There will be three main beneficiaries from this research.

Firstly, the project will support the career of the Researcher Co-Investigator Dr Robert Köchl, by providing him with the experience and research track record to either apply for group leader jobs in academia (Universities and Research Institutes), or for jobs within the commercial sector (pharma or biotech).

Secondly, the research will benefit the MRC, as they will be owners of any intellectual property (IP) generated from results, know-how and reagents coming from this work. Such IP in turn will be licensed by MRC to the commercial sector, thereby providing economic return to the MRC, which in turn will be re-invested in research.

Thirdly the proposed work will be of direct benefit to the pharmaceutical or biotech industry. Within the commercial sector there is a huge interest in interventions that modulate the function of the immune system. For example suppressing immune responses may be beneficial in the context of autoimmunity and enhancing immunity may be useful in combating cancer. The knowledge we gain from this work will be of direct use to the pharmaceutical and biotechnology industries in identifying new targets for rational drug intervention, as well as highlighting targets that should be avoided because of possible serious side effects. There is already considerable interest in drugs against Wnk kinases that could be used to treat hypertension, so our results would be of direct interest and benefit to companies working in this area, as it would alert them to possible unwanted side-effects, or identify novel indications for drugs being developed for hypertension. Thus the work will contribute directly to economic competitiveness, and to quality of life and health.