Reverting protein aggregation by peptide targeting

Axin is a scaffold protein playing a central role in the formation and regulation of both the destruction complex and the signalosome in the canonical Wnt pathway. Many naturally occurring mutations in the Axin sequence correlates with various kinds of cancer. The L106R mutation in the RGS domain of Axin induces in vivo the formation of an aberrant multiprotein aggregate and the uncontrolled activation of the pathway, while RGS L106R alone spontaneously aggregates in vitro¹. In the case of Axin, protein aggregation is the molecular etiology of the cancer phenotype and it represents an important study case of cancer as an aggregation disease. Our aim was to develop peptide inhibitors for RGS L106R aggregation that will be able to restore the functionality of the mutant to that of Axin wild type. We performed a detailed biophysical characterization of the aggregation process of RGS L106R and determined at a molecular level the hotspots for aggregation. We then designed a library of peptide binders specific for RGS L106R using a peptide array and tested them as potential aggregation inhibitors using an ANS-based aggregation assay, whose results were validated by DLS and TEM. Two peptides inhibited the aggregation of RGS L106R and disaggregated its preformed aggregates. To reveal the molecular determinants for the aggregation inhibition/reversion activity, we analysed the sequence properties of the two active peptides. Based on this, we identified new putative anti-aggregation peptides that inhibited and reverted RGS L106R aggregation. We then applied different molecular design strategies to modify rationally the sequences of the active peptides, resulting in improved peptides with strongly enhanced anti-aggregation activity².

[1] Anvarian Z. et al. (2016). "Axin cancer mutants form nanoaggregates to rewire the Wnt signaling network". Nat Struct Mol Biol 23, 324-332.

[2] Provisional patent application [62646466]: "Peptides that inhibit and revert protein aggregation in cancer".