Intelligent delivery of autophagy-targeting chimeric peptides by engineered exosomes for the degradation of α-synuclein

Targeted degradation of the aggregated α-synuclein holds tremendous potential for treating Parkinson's disease (PD). However, most of the developed aggregated α-synuclein-specific degraders, e.g., autophagy-targeting chimeric peptides, are limited by the blood-brain barrier (BBB), substantia nigra (SN) neuron targetability, and intracytoplasmic release. To overcome these obstacles, we constructed an engineered exosome (EXO) equipped with surficial glucose-regulated protein 94 (GRP94)-targeting peptide N, luminal α-synuclein-degrading peptide P1, and cathepsin-B-cleavable GFLG as the linker between the exosome skeleton protein and P1, termed N^EXOGFLG-P1. We verified that the N^EXOGFLG-P1 exosomes could cross the BBB and target diseased SN neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-induced PD model mice. Following fusion with endosomes, the exposed P1 was released into the cytoplasm by cytoplasmic cathepsin B-mediated GFLG cleavage to degrade α-synuclein. Collectively, the N^EXOGFLG-P1 exosomes exhibit a significant degradation effect on α-synuclein aggregates, providing a proof-of-concept platform for treating PD. STATEMENT OF SIGNIFICANCE: Targeted degradation of α-synuclein aggregates holds tremendous potential for the etiological treatment of Parkinson's disease (PD). However, most of current α-synuclein-specific degraders are stuck with low blood-brain barrier permeability, poor targetability for diseased cells, and uncontrolled release. Notably, α-synuclein predominantly affects neurons in the substantia nigra (SN) region rather than the whole brain. To overcome these obstacles, we constructed an engineered exosome, termed N^EXOGFLG-P1, to specially deliver and release autophagy-targeting chimeric peptide to degrade α-synuclein in the diseased SN neurons through the autophagy-lysosomal pathway. The engineered exosomes exhibit the great potential in targeting diseased SN neurons and degrading α-synuclein aggregates, providing a proof-of-concept therapeutic platform for treating PD.