Reprogramming kinase substrate specificity

This proposal stems from a remarkable phenomenon I discovered recently: the reprogramming of canonical kinase specificity to a different amino acid and substrate by a small non-enzymatic bacterial (Salmonella) virulence protein, SteE. Phosphorylation of serine (S), threonine (T) and tyrosine (Y) residues isa widespread regulatory system in cells that provides a vast and reversible expansion to proteome function.

I found that SteE interacts with the well-characterised eukaryotic S/T kinase, GSK3, and that this causesGSK3 to phosphorylates Y residues on two non-canonical substrates: SteE and the host transcription factor STAT3.SteE phosphorylation is required for STAT3 phosphorylation by GSK3, and this drives anti-inflammatory macrophage polarisation and Salmonella virulence. Therefore, S/T kinase phospho-acceptor site reprogramming is both mechanistically feasible and biologically relevant yet only described for one example.

New preliminary data suggests the existence of previously unstudied, putative, kinase reprogramming proteins that are encoded by diverse bacteria. I will study these to test the hypothesis that kinase reprogramming represents a more general mechanism that can change the phospho-acceptor site specificity of diverse eukaryotic kinases and decipher the molecular basis of reprogramming across different kinases.

I will also investigate whether eukaryotic proteins have kinase reprogramming activity. In this way, I will challenge the dogma that assigns kinases as either S/T-directed or dual specificity (phosphorylatesS/T and Y) and anticipate identifying a group of S/T kinases that can phosphorylate Y residues only when bound by a regulatory protein.

Finally, through directed evolution I aim to begin the design of synthetic kinase-altering proteins as this could revolutionise the development of kinase-based therapeutics. Overall, this work will change our understanding of kinase regulation during health and disease.