Molecular and genetic dissection of the cytosolic ADP-Heptose-ALPK1-TIFA signaling pathway

ADP-DD-heptose is a bacterial metabolite required for the synthesis of lipopolysaccharide, a component of the cell wall of gram negative bacteria. Recently, a new innate immune signal transduction pathway present in the cytosol of human cells has been identified. In this pathway ADP-DD-heptose activates alpha protein kinase 1 (ALPK1), an atypical protein kinase that is unrelated to the main subfamily of protein kinases. ALPK1 phosphorylates the protein TIFA, inducing it's oligomerisation and interaction with TRAF6. TRAF6 then undergoes oligomerisation activating it's E3 ligase activity. Similar to the role of TRAF6 in other innate immune signalling pathways, the TRAF6 E3 ligase was proposed to generate Lys63-linked ubiquitin oligomers thereby activating the master protein kinase TAK1 which drives all the subsequent events that lead to the production and secretion of the inflammatory mediators to combat the bacterial infection. We have confirmed that the expression of TRAF6 is essential for the operation of the pathway, but surprisingly found that the E3 ligase activity of TRAF6 is not. This finding indicates that much still remins to be discovered about this novel signalling pathway. Interestingly, particular mutations in ALPK1 have been found to to be the cause of several human diseases, including spiroadenoma, spiroadenocarcinoma and ROSAH, an immune disease that was only discovered in 2019. The aim of the project is to dissect the molecular details of the cytosolic ADP-DD-Heptose-ALPK1-TIFA signaling pathway, to identify novel components of the pathway and to understand how mutations in ALPK1 cause human disease. The project will involve training in a variety of state of the art techniques in molecular and cell biology, protein chemistry, cell signalling and immunology.. Project provides training in Quantitative Skills