Dopamine transporter and synaptic vesicle sorting defects initiate auxilin-linked Parkinson’s disease

Abstract

Auxilin participates in the uncoating of clathrin-coated vesicles (CCVs), thereby facilitating synaptic vesicle (SV) regeneration at presynaptic sites. Auxilin (DNAJC6/PARK19) loss-of-function mutations cause early-onset Parkinson's disease (PD). Here, we utilized auxilin-knockout (KO) mice to elucidate the mechanisms through which auxilin deficiency and clathrin-uncoating deficits lead to PD. We demonstrate that auxilin KO mice display the cardinal features of PD, including progressive motor deficits, α-synuclein pathology, nigral dopaminergic loss, and neuroinflammation. Through unbiased proteomic and neurochemical analyses, we demonstrate that dopamine homeostasis is disrupted in auxilin KO brains, including via slower dopamine reuptake kinetics in vivo, an effect associated with dopamine transporter misrouting into axonal membrane deformities in the dorsal striatum. We also show that elevated macroautophagy and defective SV protein sorting contribute to ineffective dopamine sequestration and homeostasis, ultimately leading to neurodegeneration. This study advances our knowledge of how presynaptic endocytosis deficits lead to dopaminergic vulnerability and pathogenesis of PD.

ER-lysosome lipid transfer protein VPS13C/PARK23 prevents aberrant mtDNA-dependent STING signaling

“…We did not observe any obvious motor phenotypes, including hindlimb clasping, in the Vps13c −/− mice up to 2 yr of age, nor did we observe any effect on lifespan. We assessed for motor phenotypes that had shown differences in other PD mouse models ( Cao et al, 2017 ; Vidyadhara et al, 2022 ). Balance beam testing at 6 mo of age showed no difference between Vps13c −/− mice and heterozygous controls ( Fig.…”

Cocaine-regulated trafficking of dopamine transporters in cultured neurons revealed by a pH sensitive reporter

“…They have been previously reported to be potential axonal branching points 55 and are presently viewed to be highly relevant in neural injury and neurodegeneration. 56 , 57 , 58 We found that only varicosities, but not axonal shafts or boutons exhibited a robust NH 4 Cl response ( Figures 4 B and 4C). No significant difference was observed for the MES responses ( Figure 4 C).…”

“…Recent studies have suggested molecules important for clathrin coat removal, such as synaptojanin1 (Synj1) or auxilin1, play a crucial role in DAT expression and/or trafficking. 40 , 57 , 58 We therefore decided to investigate if Synj1 deficiency influences cocaine-regulated DAT trafficking using this new reporter. Of interest, in neurons carrying a heterozygous mutation of Synj1 ( Synj1 +/− ), a larger deflection was observed ( Figures 6 A and 6B), which could suggest increased endocytosis of DAT or delivery of DAT to more acidic intracellular structures.…”

Impaired pre-synaptic plasticity and visual responses in auxilin-knockout mice

“… 13 , 14 , 15 Aux-KOs can be used to build a faithful model of DNAJC6 -linked PD in mice and Drosophila, recapitulating the cardinal features of nigrostriatal neuronal loss, alpha-synuclein pathology, and motor deficits. 16 , 17 , 18 As auxilin is broadly expressed in the brain and its endocytic function is universal to all synapses in the central nervous system, loss-of-auxilin is likely to impact the functions of brain regions beyond documented regions such as the hippocampus, dorsal striatum, and substantia nigra. 18 , 19 Because cognitive deficits are a common symptom of PD patients, including PARK19 patients, we utilized Aux-KO to explore the basis of these symptoms.…”

“… 16 , 17 , 18 As auxilin is broadly expressed in the brain and its endocytic function is universal to all synapses in the central nervous system, loss-of-auxilin is likely to impact the functions of brain regions beyond documented regions such as the hippocampus, dorsal striatum, and substantia nigra. 18 , 19 Because cognitive deficits are a common symptom of PD patients, including PARK19 patients, we utilized Aux-KO to explore the basis of these symptoms. We chose to investigate the primary visual cortex due to the ease of assays to interrogate cortical functions and as a subset of PD patients suffers from visual disturbances, such as visual hallucinations and pattern recognition deficits, attributed partially to malfunctions of the primary visual cortex in humans.…”