Project description:Dopaminergic (DA) neurons are the predominant cell type in the midbrain that synthesize dopamine, a neurotransmitter implicated in various behavioural processes, including motor function, the reward pathway, and satiety. In diseases affecting these neurons, such as in Parkinson’s disease (PD), there is growing evidence that the gut-brain axis and selective vulnerability of DA neurons plays a crucial role in disease. Most investigations relating to DA neurons in the gut rely on immunoreactivity to tyrosine hydroxylase (TH) - a rate-limiting enzyme in the production of dopamine. However, the reliability of TH staining as a marker of DA neurons has been questioned in recent years. Our aim is to perform a comprehensive characterization of DA neurons in the gut using a well-accepted reporter mouse line, expressing a fluorescent protein under the dopamine transporter promoter (DAT). Our findings confirm a unique localization of DA neurons in the gut, and unveil that there are discrete subtypes of DA neurons in the gut, which we characterized using both immunofluorescence and single-cell transcriptomics. We observed distinct subtypes of DAT neurons expressing co-transmitters and modulators across both plexuses; some of them likely co-releasing acetylcholine, and a smaller population likely releasing nitric oxide; while others were positive for a slew of canonical DA markers (Vmat2, Girk2, Foxa2). Given the clear heterogeneity of DA gut neurons, further investigation is warranted to define their functional signatures and discover their inherent biological differences that predispose these cells to neurodegeneration.
Project description:We used Drosophila genetic and behavioral models to examine AMPH-induced transcriptional changes in DAT-dependent manner, as those would be the most relevant to the stimulatory effects of the drug in the brain. We previously showed that flies respond to AMPH by increasing their locomotor activity and decreasing their sleep in a dopamine-dependent manner. Flies that carry a loss-of-function mutation in the gene encoding the Drosophila DAT homolog (dDATfmn, henceforth referred to as DAT mutants) exhibit heightened activity levels at baseline, consistent with increased levels of extracellular dopamine caused by the impairment of reuptake. In this study we compared gene expression changes in response to AMPH in brains of isogenic w1118 strain (WT) and DAT mutants. We found genes involved in the control of mRNA translation to be significantly upregulated in response to AMPH in a DAT-dependent manner.
Project description:The dopamine transporter facilitates dopamine reuptake from the extracellular space to terminate neurotransmission. The transporter belongs to the neurotransmitter:sodium symporter family, which includes transporters for serotonin, norepinephrine, and GABA that utilize the Na+ gradient to drive the uptake of substrate. Decades ago, it was shown that the serotonin transporter also antiports K+, but investigations of K+-coupled transport in other neurotransmitter:sodium symporters have been inconclusive. Here, we show that ligand binding to the drosophila- and human dopamine transporters are inhibited by K+, and the conformational dynamics of the drosophila dopamine transporter in K+ are divergent from the apo- and Na+-states. Furthermore, we found that K+ increased dopamine uptake by the drosophila dopamine transporter in liposomes, and visualized Na+ and K+ fluxes in single proteoliposomes using fluorescent ion indicators. Our results expand on the fundamentals of dopamine transport and prompt a reevaluation of the impact of K+ on other transporters in this pharmacologically important family.
Project description:The dopamine transporter is a member of the neurotransmitter:sodium symporters (NSSs), which are responsible for termination of neurotransmission through Na+-driven reuptake of neurotransmitter from the extracellular space. Experimental evidence elucidating the coordinated conformational rearrangements related to the transport mechanism has so far been limited. Here we probe the global Na+- and dopamine-induced conformational dynamics of the wild-type Drosophila melanogaster dopamine transporter using hydrogen-deuterium exchange mass spectrometry. We identify Na+- and dopamine-induced changes in specific regions of the transporter, suggesting their involvement in protein conformational transitions. Furthermore, we detect ligand-dependent slow cooperative fluctuations of helical stretches in several domains of the transporter, which could be a molecular mechanism that assists in the transporter function. Our results provide a framework for understanding the molecular mechanism underlying the function of NSSs by revealing detailed insight into the state-dependent conformational changes associated with the alternating access model of the dopamine transporter.
Project description:The study aimed to find out quantitative changes at the protein level in the total membrane fraction enriched in synaptosomes and mitochondria upon the absence of the dopamine transporter in rat brain. Therefore, the brain of male rats (Wister Han) DAT-wildtype and DAT-knockout animals, were dissected and the striatum was used for the enrichment of the synaptic and mitochondrial membrane fraction. The proteins of the total membrane fraction were further tryptically digested and analysed via label-free LC-MSMS.
Project description:Dopaminergic (DA) neurons marked by the dopamine transporter (DAT) have multiple physiological functions and are involved in the regulation of mental and neurological diseases, prompting in-depth studies into their development and functions. This research explores the spatiotemporal proteomic and transcriptomic changes in DAT+ DA neurons within key brain regions involved in DA signaling—the nucleus accumbens (NAc), substantia nigra (SNc), and ventral tegmental area (VTA). Utilizing cutting-edge multi-omics techniques, such as ultrasensitive trace sample proteomics and SMART_x0002_seq2 for transcriptomics, we examine the DA neuronal system at critical postnatal milestones: postnatal day 7 (P7), postnatal day 30 (P30), and postnatal day 60 (P60). The study reveals unique molecular profiles within DA neuron populations, showcasing their varied functional roles and developmental progression. Immunofluorescence mapping illustrates these molecular distributions, validating the quantitative data and highlighting the dynamic molecular structure of DA neurons. Our findings notably highlight a marked increase over time in Aldh1a1 expression, an essential enzyme for retinoic acid production, suggesting its evolving role in neuronal development and specific functions. This comprehensive analysis offers a profound molecular perspective on DAT+ DA neuron development, enhancing our understanding of their functional diversity and potential relevance in DA-related diseases.
Project description:Here, we performed transcriptome-profiling experiments on control scramble shRNA and shSLC6A3 HCT116 cells to study the impact DAT silencing on gene networks associated with neoplastic stemness. We also treated control HCT116 cells with the DAT agonist vanoxerine (VXN) to identify commonly regulated networks between DAT knockdown and pharmacological antagonism.