Development of a Synthetic Genetic Feedback Circuit to Sense and Modulate Neurodegenerative Protein Aggregation

Protein aggregation is a pathological hallmark of many neurodegenerative disorders, such as Alzheimer’s Disease, that affect an expanding proportion of the human population¹. Despite the significant burden caused by protein aggregation diseases, there are currently no effective therapies that address the underlying pathology. Recent efforts have focused on modulating common molecular mechanisms, such as enhancing proteostasis, or inhibiting protein aggregation². Here, we propose an alternative therapeutic solution: an adaptive gene therapy based on a synthetic feedback circuit that senses pathological aggregation of a target protein, and responds by expressing an aggregation-modulatory “therapeutic” gene.

The design of our genetic circuit is based on aggregation-dependent reconstitution of a split TEV protease, a well-established genetic system, recently used to engineer complex protein-based circuits in mammalian cells³. Here, we fuse each subunit of a split TEV protease to the aggregation-prone region of a disease-relevant protein. Protein assembly/aggregation leads to TEV reconstitution, the specific cleavage of a degron and subsequent activation of a therapeutic protein.

To validate circuit components, we first demonstrate sensing of TDP43 and Tau aggregation, two proteins critically involved in Alzheimer’s disease, in HEK293T and SH-SY5Y neuronal cell lines. Second, using a cellular model of Tau pathology, we have developed a screen to identify potential therapeutic genes, capable of modulating pathological aggregation in cells. Our cell-autonomous genetic circuit can be encoded on a single viral vector, and may facilitate the development of next-generation gene therapies for neurodegeneration.

1. Hou, Y. et al. Ageing as a risk factor for neurodegenerative disease. Nature Reviews Neurology (2019). doi:10.1038/s41582-019-0244-7
2. Scannevin, R. H. Therapeutic strategies for targeting neurodegenerative protein misfolding disorders. Curr. Opin. Chem. Biol. 44, 66–74 (2018).
3. Gao, X. J., Chong, L. S., Kim, M. S. & Elowitz, M. B. Programmable protein circuits in living cells. Science (80-. ). 361, 1252–1258 (2018).