Designed Endocytosis-Triggering Proteins mediate Targeted Degradation

Programming DNA Nanoassemblies into Polyvalent Lysosomal Degraders for Potent Degradation of Pathogenic Membrane Proteins

Lysosome-targeting chimera (LYTAC) shows great promise for protein-based therapeutics by targeted degradation of disease-associated membrane or extracellular proteins, yet its efficiency is constrained by the limited binding affinity between LYTAC reagents and designated proteins. Here, we established a programmable and multivalent LYTAC system by tandem assembly of DNA into a high-affinity protein degrader, a heterodimer aptamer nanostructure targeting both pathogenic membrane protein and lysosome-targeting receptor (insulin-like growth factor 2 receptor, IGF2R) with adjustable spatial distribution or organization pattern. The DNA-based multivalent LYTACs showed enhanced efficacy in removing immune-checkpoint protein programmable death-ligand 1 (PD-L1) and vascular endothelial growth factor receptor 2 (VEGFR2) in tumor cell membrane that respectively motivated a significant increase in T cell activity and a potent effect on cancer cell growth inhibition. With high programmability and versatility, this multivalent LYTAC system holds considerable promise for realizing protein therapeutics with enhanced activity.

Targeted protein degradation directly engaging lysosomes or proteasomes

Targeted protein degradation (TPD) has been established as a viable alternative to attenuate the function of a specific protein of interest in both biological and clinical contexts. The unique TPD mode-of-action has allowed previously undruggable proteins to become feasible targets, expanding the landscape of "druggable" properties and "privileged" target proteins. As TPD continues to evolve, a range of innovative strategies, which do not depend on recruiting E3 ubiquitin ligases as in proteolysis-targeting chimeras (PROTACs), have emerged. Here, we present an overview of direct lysosome- and proteasome-engaging modalities and discuss their perspectives, advantages, and limitations. We outline the chemical composition, biochemical activity, and pharmaceutical characteristics of each degrader. These alternative TPD approaches not only complement the first generation of PROTACs for intracellular protein degradation but also offer unique strategies for targeting pathologic proteins located on the cell membrane and in the extracellular space.

Insulin-like Growth Factor 2 (IGF2)-Fused Lysosomal Targeting Chimeras for Degradation of Extracellular and Membrane Proteins

Targeted degradation of the cell-surface and extracellular proteins via the endogenous lysosomal degradation pathways, such as lysosome-targeting chimeras (LYTACs), has recently emerged as an attractive tool to expand the scope of extracellular chemical biology. Herein, we report a series of recombinant proteins genetically fused to insulin-like growth factor 2 (IGF2), which we termed iLYTACs, that can be conveniently obtained in high yield by standard cloning and bacterial expression in a matter of days. We showed that both type-I iLYTACs, in which IGF2 was fused to a suitable affibody or nanobody capable of binding to a specific protein target, and type-II iLYTAC (or IGF2-Z), in which IGF2 was fused to the IgG-binding Z domain that served as a universal antibody-binding adaptor, could be used for effective lysosomal targeting and degradation of various extracellular and membrane-bound proteins-of-interest. These heterobifunctional iLYTACs are fully genetically encoded and can be produced on a large scale from conventional E. coli expression systems without any form of chemical modification. In the current study, we showed that iLYTACs successfully facilitated the cell uptake, lysosomal localization, and efficient lysosomal degradation of various disease-relevant protein targets from different mammalian cell lines, including EGFR, PD-L1, CD20, and α-synuclein. The antitumor properties of iLYTACs were further validated in a mouse xenograft model. Overall, iLYTACs represent a general and modular strategy for convenient and selective targeted protein degradation, thus expanding the potential applications of current LYTACs and related techniques.