Optical control of T-cell signalling dynamics
We have a near-complete characterisation of the components for many biological signalling networks, but their dynamic interconnections remain poorly understood. Current methods to investigate intracellular signalling generally disrupt one point in the network and compare cell function afterwards. However, the intervention can never be made without perturbing the rest of the system and rarely provides the dynamic information required for a mechanistic understanding of network function. We investigate cell signalling by providing quantitative and dynamic inputs to the intact network, measure the corresponding functional outputs and then infer characteristics of the underlying system. To achieve the required spatio-temporal control over signalling, we have developed light-controlled biological components that enable us to modulate both the intensity and frequency of signalling within the network. We currently focus on the intracellular signalling of T-cells, an essential immune cell-type that detect infected cells and orchestrate their removal.
I will discuss two projects from my lab in the talk. The first part is on LCK, a tyrosine kinase that is essential for initiating T-cell antigen receptor (TCR) signalling. We have used genetic code expansion to engineer a photocaged version of LCK that can be switched ‘on’ through brief light stimulation. Using this approach, we have found that in live cells, autophosphorylation of the LCK active-site loop is indispensable for its catalytic activity. We have leveraged the power of this approach to show that CD4 and CD8, the T-cell coreceptors, can enhance LCK activity, thereby helping to explain their effect in physiological TCR signalling.
For the second project, we have engineered an optically-controlled chimeric antigen receptor (OptoCAR) that provides a means to rapidly and reversibly manipulate the flux through the TCR signalling pathway. We have used this exciting new tool to directly investigate whether the downstream signalling network has the capacity to integrate or ‘remember’ previous antigen-presenting cell encounters, and the timescales over which this could occur.
Using our new tools, our key goal is to provide a quantitative understanding of how different T-cell inputs are decoded by the dynamics of the signalling pathways to specify the appropriate response. Through this, we hope to discover parts of the network that could be fine-tuned therapeutically to alleviate diseases when T-cell function becomes deleterious.
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