A rare TMEM175 mutation drives Parkinson’s disease pathology by disrupting proton gating and lysosomal acidification
Xiaotong Yang, Ping Li, Man Lv, Lingyong Wang, Ruyi Shan, Zikai Jiang, Danzhen Chen, Fangqian Huang, Weijie Cai, Liding Zhao, Zuoyou Guo, Xinhui Chen, Zhidong Cen, Yichang Wang, Wei Yang, Xinran Li, Wei Luo, Lin Yang, Meiqin Hu, Haoxing Xu
Xiaotong Yang, Ping Li, Man Lv, Lingyong Wang, Ruyi Shan, Zikai Jiang, Danzhen Chen, Fangqian Huang, Weijie Cai, Liding Zhao, Zuoyou Guo, Xinhui Chen, Zhidong Cen, Yichang Wang, Wei Yang, Xinran Li, Wei Luo, Lin Yang, Meiqin Hu, Haoxing Xu
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Research Article Aging Cell biology Development

A rare TMEM175 mutation drives Parkinson’s disease pathology by disrupting proton gating and lysosomal acidification

Abstract

Transmembrane protein 175 (TMEM175), implicated in Parkinson’s disease (PD) risk, has been variably proposed to function as a background K+ “leak” channel or a proton-activated proton channel in lysosomes. Here, we identified the rare TMEM175 variant p.L275R in a patient with early onset PD. Electrophysiological analyses revealed that TMEM175-L275R mutant proteins retain normal lysosomal expression and K+ “leak” activity, but specifically lose proton- and agonist-dependent activation gating. In skin fibroblasts isolated from the patient with PD harboring the monoallelic p.L275R mutation (TMEM175+/L275R), and in derived induced pluripotent stem cells and induced dopaminergic neurons, lysosomal H+ flux, acidification, and degradation were impaired. These lysosomal defects were corrected upon genome editing to produce the isogenic WT allele (+/+Cor), but appeared when the mutant allele was introduced onto a WT background (+/L275RMut). Pathological α-synuclein aggregation was facilitated in patient-derived (+/L275R) and mutation-introduced (+/L275RMut) neurons. Consistent with these genetic findings, pharmacological activation of TMEM175 with small-molecule agonists restored lysosomal functions and reduced α-synuclein aggregation in TMEM175+/L275R neurons. In in-vivo studies, equivalent-site–mutation knock-in mice demonstrated synucleinopathy and PD-like motor phenotypes. Collectively, our work provides genetic and pharmacological evidence that severe loss-of-function mutations may contribute causally to the onset age and pathogenesis of PD and identifies lysosomal proton channels and transporters as potential therapeutic targets for PD intervention.

Authors

Xiaotong Yang, Ping Li, Man Lv, Lingyong Wang, Ruyi Shan, Zikai Jiang, Danzhen Chen, Fangqian Huang, Weijie Cai, Liding Zhao, Zuoyou Guo, Xinhui Chen, Zhidong Cen, Yichang Wang, Wei Yang, Xinran Li, Wei Luo, Lin Yang, Meiqin Hu, Haoxing Xu

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Figure 1

The PD patient–derived L275R mutation selectively disrupts the activation gating of the TMEM175 channel.

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The PD patient–derived L275R mutation selectively disrupts the activatio...
(A) Diagram of whole-cell patch-clamp recordings of H+ currents through TMEM175 channels carrying PD patient–derived rare variants (MAF < 0.01) in a heterologous overexpression system. TMEM175 rare variants were identified from a WES/WGS database for a local PD cohort. (B and C) Whole-cell H+ currents recorded in HEK293T cells overexpressing TMEM175WT or TMEM175L275R with cytosolic pH (pHC) set to 7.2, and extracellular/luminal pH (pHE/L) varied as indicated. Nontransfected cells served as the negative control (Ctrl). Unless otherwise indicated, all recording solutions contained NMDG+ and MSA– as the major ions; n = 6 (Ctrl); 16 (WT); 27 (L275R) cells. (D and E) Whole-cell H+ currents recorded in HEK293T cells overexpressing TMEM175WT or TMEM175L275R in response to DCPIB (10 μM); n = 3–4 cells. Each dashed line represents the same cell before and after DCPIB application. (F and G) Whole-cell Cs+ currents recorded in HEK293T cells overexpressing TMEM175WT or TMEM175L275R. The recording solutions contained 140 mM Cs or Na-MSA (pH 7.2); n = 4–5 cells. Unless otherwise indicated, data are means ± SEM with dots representing samples from ≥ 3 biological replicates. ***P < 0.001, *P < 0.05; by 1-way ANOVA test.