Hopfner, F. | Search bioRxiv

bioRxiv2024

Neuronal and oligodendroglial but not astroglial tau translates to in vivo tau-PET signals in primary tauopathies

Tau-PET receives growing interest as an imaging biomarker for the 4-repeat tauopathy progressive supranuclear palsy (PSP). However, the translation of in vitro 4R-tau binding to in vivo tau-PET signals is still unclear. Therefore, we conducted a longitudinal [18F]PI-2620 PET/MRI study in a 4-repeat-tau mouse model (PS19) and found elevated [18F]PI-2620 PET signal in the presence of high neuronal tau. Cell sorting after radiotracer injection in vivo revealed higher tracer uptake in single neurons compared to astrocytes of PS19 mice. Regional [18F]PI-2620 tau-PET signals during lifetime correlated with abundance of fibrillary tau in subsequent autopsy samples of PSP patients and disease controls. In autoradiography, tau-positive neurons and oligodendrocytes with high AT8 density but not tau-positive astrocytes were the driver of [18F]PI-2620 autoradiography signals in PSP. In summary, neuronal and oligodendroglial tau constitutes the dominant source of tau-PET radiotracer binding in 4-repeat-tauopathies, yielding the capacity to translate to an in vivo signal.

neuroscience↗

bioRxiv2024

A genome-wide RNA interference screening reveals protectiveness of SNX5 knockdown in a Parkinson`s disease cell model

BackgroundAlpha-synuclein is a major player in the pathophysiology of a group of diseases called synucleinopathies, which include Parkinsons disease, dementia with Lewy bodies, and multiple system atrophy. To date, there is no disease-modifying therapy available for these synucleinopathies. Furthermore, the intracellular mechanisms by which alpha-synuclein confers toxicity are not yet fully understood. Therefore, it is of utmost importance to investigate the pathophysiology of alpha-synuclein-induced toxicity in order to identify novel molecular targets for the development of disease-modifying therapies. MethodsIn the present study, we performed the first genome-wide siRNA modifier screening in a human postmitotic neuronal cell model using alpha-synuclein-induced toxicity as read-out. In a multi-step approach, we identified several genes, whose knockdown protected from alpha-synuclein-induced toxicity. The main hit was further validated by different methods, including immunofluorescence microscopy, qPCR, and Western blot. ResultsThe highest protection was achieved by knockdown of SNX5, which encodes the SNX5 protein, a component of the retromer complex. We confirmed the protective efficacy of SNX5 knockdown with an independent siRNA system. SNX5 protein is part of SNX-BAR heterodimers, which are part of the retromer complex. We found that extracellular and overexpressed intracellular alpha-synuclein led to fragmentation of the trans-Golgi network, which was prevented by SNX5 knockdown by confining alpha-synuclein in early endosomes. ConclusionIn summary, our data suggest that SNX5 plays an important role in trafficking and toxicity of alpha-synuclein. Therefore, SNX5 appears to be a possible target for therapeutic interventions in synucleinopathies.

neuroscience↗