N-acetyl-l-leucine lowers α-synuclein levels and improves synaptic function in Parkinson’s disease models
Pingping Song, Chuyu Chen, Rossella Franchini, Bryan Duong, Yi-Zhi Wang, Robert Coukos, Zhong Xie, Jeffrey N. Savas, Yueqin Zhou, Mariarita Bertoldi, D. James Surmeier, Loukia Parisiadou, Dimitri Krainc
Pingping Song, Chuyu Chen, Rossella Franchini, Bryan Duong, Yi-Zhi Wang, Robert Coukos, Zhong Xie, Jeffrey N. Savas, Yueqin Zhou, Mariarita Bertoldi, D. James Surmeier, Loukia Parisiadou, Dimitri Krainc
View: Text | PDF
Research Article Cell biology Neuroscience

N-acetyl-l-leucine lowers α-synuclein levels and improves synaptic function in Parkinson’s disease models

Abstract

N-acetyl-l-leucine (NALL), a derivative of the branched-chain amino acid leucine, has shown therapeutic potential for neurodegenerative diseases, including in prodromal stages of Parkinson’s disease (PD). However, the mechanism of its protective effects has been largely unknown. Using human induced pluripotent stem cell–derived dopaminergic neurons from patients carrying GBA1, LRRK2, or VPS35 mutations, as well as from sporadic PD cases, we found that NALL treatment markedly reduced Ser129 phosphorylated α-synuclein (pS129-syn). Discovery-based proteomic analysis revealed that NALL treatment upregulated lysosomal, mitochondrial, and synaptic proteins without inducing cytotoxicity. The reduction of pS129-syn was dependent on serine protease HTRA1, which was robustly induced by NALL. Moreover, NALL increased the expression of wild-type parkin in mutant dopaminergic neurons, leading to increased glycosylated dopamine transporter, elevated synaptic membrane-associated synaptojanin-1, and accelerated synaptic vesicle endocytosis, suggesting improved synaptic function. Furthermore, in LRRK2R1441C knockin mice, NALL administration decreased pS129-syn, elevated parkin levels, and ameliorated dopamine-dependent motor learning deficits. These findings highlight the therapeutic potential of NALL for PD by its protective effects on α-synuclein pathology and synaptic function in vulnerable dopaminergic neurons.

Authors

Pingping Song, Chuyu Chen, Rossella Franchini, Bryan Duong, Yi-Zhi Wang, Robert Coukos, Zhong Xie, Jeffrey N. Savas, Yueqin Zhou, Mariarita Bertoldi, D. James Surmeier, Loukia Parisiadou, Dimitri Krainc

×

Figure 2

The effect of NALL on pS129-syn was mediated through increasing HTRA1.

Options: View larger image (or click on image) Download as PowerPoint
The effect of NALL on pS129-syn was mediated through increasing HTRA1. (...
(A) Heatmap showing proteins significantly altered (adjusted P < 0.05) by 30 days of NALL treatment in GBA1 L444P mutant neurons (n = 3 biological replicates; 3,801 total proteins). (B) Volcano plot of protein changes induced by 10 mM NALL versus nontreated (NT) controls. HTRA1 (green) and other significantly altered proteins. Dashed line, adjusted P = 0.05 threshold (1-way ANOVA with Benjamini-Hochberg correction). (C–H) Representative Western blots and corresponding quantification of HTRA1 and pS129-syn in total lysates (C and D), Triton-soluble fractions (E and F), and Triton-insoluble fractions (G and H) of GBA1 L444P neurons treated with increasing NALL concentrations for 30 days. β-III-tubulin, GAPDH, or total protein staining served as loading controls (n = 3 independent experiments). (I–K) Western blot analysis (I) and quantification of HTRA1 (J) and pS129-syn (K) in GBA1 L444P neurons following HTRA1 knockdown (KD-1 and KD-2) with or without 10 mM NALL. Data were normalized to GAPDH or β-III-tubulin and expressed relative to NT-scramble controls (n = 4 independent experiments). Statistical significance was determined by 1-way ANOVA with Benjamini-Hochberg correction (B), 1-way ANOVA (D, F, H, and J right), or 2-way ANOVA (J left and K). Data represent mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.005, and ****P < 0.001.