Biology subjects

Pifl, C.

Publications and source records attributed to Pifl, C..

3 recordsLinked to original sources

bioRxiv2024

Viral overexpression of human alpha-synuclein in mouse substantia nigra dopamine neurons results in hyperdopaminergia but no neurodegeneration

Loss of select neuronal populations such as midbrain dopamine (DA) neurons is a pathological hallmark of Parkinsons disease (PD). The small neuronal protein -synuclein has been related both genetically and neuropathologically to PD, yet how it contributes to selective vulnerability remains elusive. Here, we describe the generation of a novel adeno-associated viral vector (AAV) for Cre-dependent overexpression of wild-type human -synuclein. Our strategy allows us to restrict -synuclein to select neuronal populations and hence investigate the cell-autonomous effects of elevated -synuclein in genetically-defined cell types. Since DA neurons in the substantia nigra pars compacta (SNc) are particularly vulnerable in PD, we investigated in more detail the effects of increased -synuclein in these cells. AAV-mediated overexpression of wildtype human -synuclein in SNc DA neurons increased the levels of -synuclein within these cells and augmented phosphorylation of -synuclein at serine-129, which is considered a pathological feature of PD and other synucleinopathies. However, despite abundant -synuclein overexpression and hyperphosphorylation we did not observe any DA neurodegeneration up to 90 days post virus infusion. In contrast, we noticed that overexpression of -synuclein resulted in increased locomotor activity and elevated striatal DA levels suggesting that -synuclein enhanced dopaminergic activity. We therefore conclude that cell-autonomous effects of elevated -synuclein are not sufficient to trigger acute DA neurodegeneration.

neuroscience↗

bioRxiv2023

Crucial neuroprotective roles of the metabolite BH4 in dopaminergic neurons

Dopa-responsive dystonia (DRD) and Parkinsons disease (PD) are movement disorders caused by the dysfunction of nigrostriatal dopaminergic neurons. Identifying druggable pathways and biomarkers for guiding therapies is crucial due to the debilitating nature of these disorders. Recent genetic studies have identified variants of GTP cyclohydrolase-1 (GCH1), the rate-limiting enzyme in tetrahydrobiopterin (BH4) synthesis, as causative for these movement disorders. Here, we show that genetic and pharmacological inhibition of BH4 synthesis in mice and human midbrain-like organoids accurately recapitulates motor, behavioral and biochemical characteristics of these human diseases, with severity of the phenotype correlating with extent of BH4 deficiency. We also show that BH4 deficiency increases sensitivities to several PD-related stressors in mice and PD human cells, resulting in worse behavioral and physiological outcomes. Conversely, genetic and pharmacological augmentation of BH4 protects mice from genetically- and chemically induced PD-related stressors. Importantly, increasing BH4 levels also protects primary cells from PD-affected individuals and human midbrain-like organoids (hMLOs) from these stressors. Mechanistically, BH4 not only serves as an essential cofactor for dopamine synthesis, but also independently regulates tyrosine hydroxylase levels, protects against ferroptosis, scavenges mitochondrial ROS, maintains neuronal excitability and promotes mitochondrial ATP production, thereby enhancing mitochondrial fitness and cellular respiration in multiple preclinical PD animal models, human dopaminergic midbrain-like organoids and primary cells from PD-affected individuals. Our findings pinpoint the BH4 pathway as a key metabolic program at the intersection of multiple protective mechanisms for the health and function of midbrain dopaminergic neurons, identifying it as a potential therapeutic target for PD.

neuroscience↗

bioRxiv2021

Handling of intracellular K + determines voltage dependence of plasmalemmal monoamine transporter function

The concentrative power of the transporters for dopamine (DAT), norepinephrine (NET) and serotonin (SERT) is thought to be fueled by the transmembrane Na+ gradient, but it is conceivable that they can also tap other energy sources, e.g. membrane voltage and/or the transmembrane K+ gradient. We address this by recording uptake of endogenous substrates or the fluorescent substrate APP+ ((4-(4-dimethylamino)phenyl-1-methylpyridinium) under voltage control in cells expressing DAT, NET or SERT. We show that DAT and NET differ from SERT in intracellular handling of K+. In DAT and NET, substrate uptake was voltage-dependent due to the transient nature of intracellular K+ binding, which precluded K+ antiport. SERT, however, antiports K+ and achieves voltage-independent transport. Thus, there is a trade-off between maintaining constant uptake and harvesting membrane potential for concentrative power, which we conclude to occur due to subtle differences in the kinetics of co-substrate ion binding in closely related transporters.

biophysics↗