We seek to understand the biophysical and molecular mechanisms of how cells sense, transmit and process chemical information to make decisions. We study this problem in the biological context of immune cell signalling. To keep us healthy and free of disease we depend on a complex network of cells that comprise our immune system. A functioning immune system must detect foreign invaders, such as viruses and pathogenic bacteria, and distinguish them from our own healthy tissues. How do the many morphological distinct cell types that make up our immune system detect and respond to the chemical signals of infection and disease? How do these diverse cell types coordinate their behaviour to activate an immune response that clears the body of infection? 

 

Immune cells are masters at information processing and decision making: they can detect signals that are vanishingly small and can accurately discriminate between closely related signals.  At the molecular level immune cell decision making is dependent on complex networks of proteins. These protein networks are the biochemical circuitry that allows immune cells to process chemical data. These networks of proteins are able to rapidly respond to chemical signals and activate an appropriate cellular response.

 

We are interested in the following questions of how these protein signalling networks work:

How is immune signaling spatially and temporally controlled? 

How are extracellular signals accurately transduced across the plasma membrane to activate intracellular signaling reactions? How are signaling protein recruited and activated at precise locations and moments in time? What are the underlying physical and chemical mechanism of this spatial and temporal control?

 

In our previous work we engineered a DNA based T cell receptor (also known as a Chimeric Antigen Receptor -CAR). Combining this synthetic engineered system with supported lipid bilayer technology allowed us to give a precise biochemical signal to a T cell and monitor signalling outputs at single molecule resolution.

 

In the movie shown on the right you can see DNA ligands (magenta channel) clustering in response to binding to our designed DNA receptor. Receptor engagement induces the formation of receptor-ligand clusters that recruit 

How do immune signaling networks work in the complex chemical environment of the cellular cytoplasm?

The cellular cytoplasm is a complex environment containing networks of cytoskeletal polymers, membrane bound and membrane-less organelles. We seek to understand how the subcellular localisation of biochemical signalling reactions modify signalling outputs. We are interested in the interplay between cytoplasmic organisation and signal transduction. We seek to understand how signaling networks interface and modulate the architecture and chemical properties of the cellular cytosol. 

 

How do signalling networks reorganise the cellular cytoplasm?

 

How does the organisation of the cytoplasm control or regulate the flux of information through a signalling pathway?

How do cells convert the random behavior of molecules/complexes into a graded or binary cellular response?

How do cell create precise descisions based the noisy random fluctuations of molecules?  We are using multi-colour single molecule imaging to understand how single receptor ligand binding are transduced into the intracellular biochemistry of signaling. In the movie on the right you can see a single molecule of DNA ligand (red spots) binding and unbinding on the surface of a T cell (shown in green). Single receptor/ligand binding events are detected using a long time exposure (~500ms).

 

By combining multi-colour imaging, quantitative image analysis with theoretical approaches we can construct mechanistic models that links the collective behaviour of signalling molecules to immune cell activation.

Approaches and ongoing projects

To answer these questions we use a synthetic approach that combines cell engineering, high resolution microscopy and theory. We strive to create experimental systems that allow us to ask questions about the underlying biophysical and molecular mechanisms.   

Current ongoing projects in the lab:

1. Re-engineering T cell signalling using rationally designed receptors

2. Digital signalling at single molecule resolution

3. The spatial and temporal dynamics of innate immune signalling

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