Our cells possess an intrinsic ability to fight infection. This provides a crucial last line of defence when the innate and adaptive immune systems have failed to control a pathogen. In 2010 it was discovered that antibodies brought into the cell by invading viruses and bacteria are detected by a protein called TRIM21 (Mallery et al. 2010 PNAS). This activates a rapid and specific degradation response by the cell’s waste disposal system, the proteasome, that prevents infection. Though TRIM21 acts in a cell-autonomous manner, it can also alerts the wider immune system to the site of infection through the activation of inflammatory transcriptional networks (McEwan et al. 2013 Nat Immunol). Cytoplasmic antibodies therefore act as a potent danger signal to control viral infection (review McEwan 2016 Antibodies).
The specificity of TRIM21 is dictated solely by the antibody to which it has bound. Antibodies are widely used in molecular biology and an enormous diversity of antibodies targeting the majority of human proteins has been amassed by the research community. Introducing antibodies into cell by electroporation or microinjection enables the rapid and selective degradation of cellular proteins (Clift et al. 2017 Cell). Trim-Away represents the first broadly-applicable protein-level depletion technique that does not rely on prior genetic modification of the target protein. It therefore complements techniques that act on DNA (CRISPR/Cas9) and RNA (RNA interference) to enable functional studies of genes at the three fundamental levels of biological information.
Using TRIM21 to target pathological proteins
The use of monoclonal antibodies has been revolutionary in modern medicine. For example adalimumab (Humira), which targets TNFα, has transformed the treatment of numerous auto-immune and inflammatory diseases. However, current approaches can only target proteins accessible to the extracellular space, leaving a sizeable proportion of the proteome out of reach. The enduring problem is an inability to introduce large biomolecules to the intracellular environment (Benn, Mukadam & McEwan 2021). We are developing new solutions to these problems that permit antibody, or antibody-like constructs, to exert activity in the intracellular domain.
Understanding how tau pathology occurs will be critical to developing mechanism-guided therapeutic strategies in Alzheimer’s disease and other tauopathies. One possibility is that tau ‘seeds’ spread from cell to cell, inducing conformational changes in native tau pools. Our lab undertakes work in to the basic mechanisms of how this propagation occurs, including:
- the uptake and entry of tau assemblies to cells (Tuck et al 2022)
- the behaviour of tau assemblies in 3D culture models (Miller, Mukadam et al 2021)
- genetic factors implicated in susceptibility to seeded aggregation
- the role of innate immune signalling in tau aggregation (Sanford & McEwan 2022)
We work within academia and with industrial partners to develop target-directed and unbiased drug discovery programmes in these areas.