Bifunctional molecules that induce targeted degradation and transcytosis of extracellular proteins in brain cells

We present the application of Angiopep-2 as a molecular degrader of extracellular proteins (MoDE) promoting target protein removal by both transcytosis and lysosomal degradation mechanisms in brain endothelial cells. The accumulation of pathogenic proteins is a hallmark of many neurodegenerative diseases, and removal of these species is a promising avenue for the development of novel therapies. Targeted protein degradation technologies are emerging as efficacious therapeutic strategies in a wide range of diseases. However, there are no existing methods for the degradation of extracellular proteins in the central nervous system (CNS). Angiopep-2, a brain-targeting peptide derived from aprotinin, has previously been employed as a covalent tag to facilitate receptor-mediated transcytosis of therapeutics across the blood brain barrier (BBB). MoDEs/LyTACs consisting of Angiopep-2 modified with biotin or a chloroalkane ligand triggered endocytosis of streptavidin and HaloTag protein, respectively. Interestingly, uptake occurred independently of LRP-1, which is the reported receptor for Angiopep-2. MoDE-mediated endocytosis of streptavidin in a bEnd.3 BBB model resulted in two mechanisms of protein removal: both bi-directional transcytosis and lysosomal degradation. This study demonstrates that Angiopep-2-based MoDEs can recruit, endocytose, and degrade proteins of interest in CNS cells, supporting their further development as molecular degraders of pathogenic neuroproteins.