Nagaraja, S. R. | bioRxiv Science

bioRxiv2025

VMAT2 dysfunction impairs vesicular dopamine uptake, driving its oxidation and α-synuclein pathology in DJ-1-linked Parkinson's disease neurons

Parkinsons disease (PD) is characterized by -synuclein accumulation and dopaminergic neuron degeneration, with dopamine (DA) oxidation emerging as a key pathological driver. However, the mechanisms underlying this neurotoxic process remain unclear. Using PD patient-derived and CRISPR-engineered iPSC midbrain dopaminergic neurons lacking DJ-1, we identified defective sequestration of cytosolic DA into synaptic vesicles, which culminated in DA oxidation and -synuclein accumulation. In-depth proteomics, state-of-the-art imaging, and ultrasensitive DA probes uncovered that decreased VMAT2 protein and function impaired vesicular DA uptake, resulting in reduced vesicle availability and abnormal vesicle morphology. Furthermore, VMAT2 activity and vesicle endocytosis are processes dependent on ATP, which is notably reduced in DJ-1-deficient dopaminergic neurons. ATP supplementation restored vesicular function and alleviated DA-related pathologies in mutant dopaminergic neurons. This study reveals an ATP-sensitive mechanism that regulates DA homeostasis through VMAT2 and vesicle dynamics in midbrain dopaminergic neurons, highlighting enhanced DA sequestration as a promising therapeutic strategy for PD. TeaserLoss of DJ-1 interferes with VMAT2 function and vesicle dynamics, leading to DA oxidation and -synuclein pathology in PD neurons.

neuroscience↗

bioRxiv2022

Co-translational binding of importins to nascent proteins

Various cellular quality control mechanisms support proteostasis. While, ribosome-associated chaperones prevent misfolding of nascent chains during translation, importins were shown to prevent the aggregation of specific cargoes in a post-translational mechanism prior the import into the nucleoplasm. Here, we hypothesized that importins may already bind ribosome-associated cargo in a co-translational manner. We systematically measured the nascent chain association of all importins in Saccharomyces cerevisiae by selective ribosome profiling. We identified a subset of importins that bind to a wide range of nascent, often uncharacterized cargoes. This included ribosomal proteins, chromatin remodelers and RNA binding proteins that are aggregation prone in the cytosol. We show that importins act consecutively with other ribosome-associated chaperones. Thus, the nuclear import system is directly intertwined with nascent chain folding and chaperoning. One-Sentence SummaryWe describe an unanticipated connection between co-translational protein chaperoning and the nuclear import system.

molecular biology↗