LRP1 is a neuronal receptor for [alpha]-synuclein uptake and spread

• Published in: Molecular neurodegeneration Vol. 17; no. 1
• Main Authors: Chen, Kai, Martens, Yuka A, Meneses, Axel, Ryu, Daniel H, Lu, Wenyan, Raulin, Ana Caroline, Li, Fuyao, Zhao, Jing, Chen, Yixing, Jin, Yunjung, Linares, Cynthia, Goodwin, Marshall, Li, Yonghe, Liu, Chia-Chen, Kanekiyo, Takahisa, Holtzman, David M, Golde, Todd E, Bu, Guojun, Zhao, Na
• Format: Journal Article
• Language: English
• Published: BioMed Central Ltd 02.09.2022
• Subjects: Analysis; Dementia; Diagnostic reagents industry; Low density lipoproteins; Lysine; Nervous system diseases; Neurons; Oligomers; Physiological aspects; Stem cells; Canada
• ISSN: 1750-1326; 1750-1326
• DOI: 10.1186/s13024-022-00560-w

Background The aggregation and spread of [alpha]-synuclein ([alpha]-Syn) protein and related neuronal toxicity are the key pathological features of Parkinson's disease (PD) and Lewy body dementia (LBD). Studies have shown that pathological species of [alpha]-Syn and tau can spread in a prion-like manner between neurons, although these two proteins have distinct pathological roles and contribute to different neurodegenerative diseases. It is reported that the low-density lipoprotein receptor-related protein 1 (LRP1) regulates the spread of tau proteins; however, the molecular regulatory mechanisms of [alpha]-Syn uptake and spread, and whether it is also regulated by LRP1, remain poorly understood. Methods We established LRP1 knockout (LRP1-KO) human induced pluripotent stem cells (iPSCs) isogenic lines using a CRISPR/Cas9 strategy and generated iPSC-derived neurons (iPSNs) to test the role of LRP1 in [alpha]-Syn uptake. We treated the iPSNs with fluorescently labeled [alpha]-Syn protein and measured the internalization of [alpha]-Syn using flow cytometry. Three forms of [alpha]-Syn species were tested: monomers, oligomers, and pre-formed fibrils (PFFs). To examine whether the lysine residues of [alpha]-Syn are involved in LRP1-mediated uptake, we capped the amines of lysines on [alpha]-Syn with sulfo-NHS acetate and then measured the internalization. We also tested whether the N-terminus of [alpha]-Syn is critical for LRP1-mediated internalization. Lastly, we investigated the role of Lrp1 in regulating [alpha]-Syn spread with a neuronal Lrp1 conditional knockout (Lrp1-nKO) mouse model. We generated adeno-associated viruses (AAVs) that allowed for distinguishing the [alpha]-Syn expression versus spread and injected them into the hippocampus of six-month-old Lrp1-nKO mice and the littermate wild type (WT) controls. The spread of [alpha]-Syn was evaluated three months after the injection. Results We found that the uptake of both monomeric and oligomeric [alpha]-Syn was significantly reduced in iPSNs with LRP1-KO compared with the WT controls. The uptake of [alpha]-Syn PFFs was also inhibited in LRP1-KO iPSNs, albeit to a much lesser extent compared to [alpha]-Syn monomers and oligomers. The blocking of lysine residues on [alpha]-Syn effectively decreased the uptake of [alpha]-Syn in iPSNs and the N-terminus of [alpha]-Syn was critical for LRP1-mediated [alpha]-Syn uptake. Finally, in the Lrp1-nKO mice, the spread of [alpha]-Syn was significantly reduced compared with the WT littermates. Conclusions We identified LRP1 as a key regulator of [alpha]-Syn neuronal uptake, as well as an important mediator of [alpha]-Syn spread in the brain. This study provides new knowledge on the physiological and pathological role of LRP1 in [alpha]-Syn trafficking and pathology, offering insight for the treatment of synucleinopathies. Keywords: Low-density lipoprotein receptor-related protein 1, [alpha]-Synuclein, Human induced pluripotent stem cells, Parkinson's disease, Lewy body dementia