SLC10A4 is a vesicular amine-associated transporter modulating dopamine homeostasis

Diverse genetic alteration dysregulates neuropeptide and intracellular signalling in the suprachiasmatic nuclei

In mammals, intrinsic 24 h or circadian rhythms are primarily generated by the suprachiasmatic nuclei (SCN). Rhythmic daily changes in the transcriptome and proteome of SCN cells are controlled by interlocking transcription-translation feedback loops (TTFLs) of core clock genes and their proteins. SCN cells function as autonomous circadian oscillators, which synchronize through intercellular neuropeptide signalling. Physiological and behavioural rhythms can be severely disrupted by genetic modification of a diverse range of genes and proteins in the SCN. With the advent of next generation sequencing, there is unprecedented information on the molecular profile of the SCN and how it is affected by genetically targeted alteration. However, whether the expression of some genes is more readily affected by genetic alteration of the SCN is unclear. Here, using publicly available datasets from recent RNA-seq assessments of the SCN from genetically altered and control mice, we evaluated whether there are commonalities in transcriptome dysregulation. This was completed for four different phases across the 24 h cycle and was augmented by Gene Ontology Molecular Function (GO:MF) and promoter analysis. Common differentially expressed genes (DEGs) and/or enriched GO:MF terms included signalling molecules, their receptors, and core clock components. Finally, examination of the JASPAR database indicated that E-box and CRE elements in the promoter regions of several commonly dysregulated genes. From this analysis, we identify differential expression of genes coding for molecules involved in SCN intra- and intercellular signalling as a potential cause of abnormal circadian rhythms.

The role of exosomal molecular cargo in exosome biogenesis and disease diagnosis

Exosomes represent a type of extracellular vesicles derived from the endosomal pathway that transport diverse molecular cargoes such as proteins, lipids, and nucleic acids. These cargoes have emerged as crucial elements impacting disease diagnosis, treatment, and prognosis, and are integral to the process of exosome formation. This review delves into the essential molecular cargoes implicated in the phases of exosome production and release. Emphasis is placed on their significance as cancer biomarkers and potential therapeutic targets, accompanied by an exploration of the obstacles and feasible applications linked to these developments.

Unraveling the role of Slc10a4 in auditory processing and sensory motor gating: Implications for neuropsychiatric disorders?

BACKGROUND

Psychiatric disorders, such as schizophrenia, are complex and challenging to study, partly due to the lack of suitable animal models. However, the absence of the Slc10a4 gene, which codes for a monoaminergic and cholinergic associated vesicular transporter protein, in knockout mice (Slc10a4-/-), leads to the accumulation of extracellular dopamine. A major challenge for studying schizophrenia is the lack of suitable animal models that accurately represent the disorder. We sought to overcome this challenge by using Slc10a4-/- mice as a potential model, considering their altered dopamine levels. This makes them a potential animal model for schizophrenia, a disorder known to be associated with altered dopamine signaling in the brain.

METHODS

The locomotion, auditory sensory filtering and prepulse inhibition (PPI) of Slc10a4-/- mice were quantified and compared to wildtype (WT) littermates. Intrahippocampal electrodes were used to record auditory event-related potentials (aERPs) for quantifying sensory filtering in response to paired-clicks. The channel above aERPs phase reversal was chosen for reliably comparing results between animals, and aERPs amplitude and latency of click responses were quantified. WT and Slc10a4-/- mice were also administered subanesthetic doses of ketamine to provoke psychomimetic behavior.

RESULTS

Baseline locomotion during auditory stimulation was similar between Slc10a4-/- mice and WT littermates. In WT animals, normal auditory processing was observed after i.p saline injections, and it was maintained under the influence of 5 mg/kg ketamine, but disrupted by 20 mg/kg ketamine. On the other hand, Slc10a4-/- mice did not show significant differences between N40 S1 and S2 amplitude responses in saline or low dose ketamine treatment. Auditory gating was considered preserved since the second N40 peak was consistently suppressed, but with increased latency. The P80 component showed higher amplitude, with shorter S2 latency under saline and 5 mg/kg ketamine treatment in Slc10a4-/- mice, which was not observed in WT littermates. Prepulse inhibition was also decreased in Slc10a4-/- mice when the longer interstimulus interval of 100 ms was applied, compared to WT littermates.

CONCLUSION

The Slc10a4-/- mice responses indicate that cholinergic and monoaminergic systems participate in the PPI magnitude, in the temporal coding (response latency) of the auditory sensory gating component N40, and in the amplitude of aERPs P80 component. These results suggest that Slc10a4-/- mice can be considered as potential models for neuropsychiatric conditions.

Single-cell spatial transcriptomic and translatomic profiling of dopaminergic neurons in health, aging, and disease

The brain is spatially organized and contains unique cell types, each performing diverse functions and exhibiting differential susceptibility to neurodegeneration. This is exemplified in Parkinson's disease with the preferential loss of dopaminergic neurons of the substantia nigra pars compacta. Using a Parkinson's transgenic model, we conducted a single-cell spatial transcriptomic and dopaminergic neuron translatomic analysis of young and old mouse brains. Through the high resolving capacity of single-cell spatial transcriptomics, we provide a deep characterization of the expression features of dopaminergic neurons and 27 other cell types within their spatial context, identifying markers of healthy and aging cells, spanning Parkinson's relevant pathways. We integrate gene enrichment and genome-wide association study data to prioritize putative causative genes for disease investigation, identifying CASR as a regulator of dopaminergic calcium handling. These datasets represent the largest public resource for the investigation of spatial gene expression in brain cells in health, aging, and disease.

Exploring a novel seven-gene marker and mitochondrial gene TMEM38A for predicting cervical cancer radiotherapy sensitivity using machine learning algorithms

Background

Radiotherapy plays a crucial role in the management of Cervical cancer (CC), as the development of resistance by cancer cells to radiotherapeutic interventions is a significant factor contributing to treatment failure in patients. However, the specific mechanisms that contribute to this resistance remain unclear. Currently, molecular targeted therapy, including mitochondrial genes, has emerged as a new approach in treating different types of cancers, gaining significant attention as an area of research in addressing the challenge of radiotherapy resistance in cancer.

Methods

The present study employed a rigorous screening methodology within the TCGA database to identify a cohort of patients diagnosed with CC who had received radiotherapy treatment. The control group consisted of individuals who demonstrated disease stability or progression after undergoing radiotherapy. In contrast, the treatment group consisted of patients who experienced complete or partial remission following radiotherapy. Following this, we identified and examined the differentially expressed genes (DEGs) in the two cohorts. Subsequently, we conducted additional analyses to refine the set of excluded DEGs by employing the least absolute shrinkage and selection operator regression and random forest techniques. Additionally, a comprehensive analysis was conducted in order to evaluate the potential correlation between the expression of core genes and the extent of immune cell infiltration in patients diagnosed with CC. The mitochondrial-associated genes were obtained from the MITOCARTA 3.0. Finally, the verification of increased expression of the mitochondrial gene TMEM38A in individuals with CC exhibiting sensitivity to radiotherapy was conducted using reverse transcription quantitative polymerase chain reaction and immunohistochemistry assays.

Results

This process ultimately led to the identification of 7 crucial genes, viz., GJA3, TMEM38A, ID4, CDHR1, SLC10A4, KCNG1, and HMGCS2, which were strongly associated with radiotherapy sensitivity. The enrichment analysis has unveiled a significant association between these 7 crucial genes and prominent signaling pathways, such as the p53 signaling pathway, KRAS signaling pathway, and PI3K/AKT/MTOR pathway. By utilizing these 7 core genes, an unsupervised clustering analysis was conducted on patients with CC, resulting in the categorization of patients into three distinct molecular subtypes. In addition, a predictive model for the sensitivity of CC radiotherapy was developed using a neural network approach, utilizing the expression levels of these 7 core genes. Moreover, the CellMiner database was utilized to predict drugs that are closely linked to these 7 core genes, which could potentially act as crucial agents in overcoming radiotherapy resistance in CC.

Conclusion

To summarize, the genes GJA3, TMEM38A, ID4, CDHR1, SLC10A4, KCNG1, and HMGCS2 were found to be closely correlated with the sensitivity of CC to radiotherapy. Notably, TMEM38A, a mitochondrial gene, exhibited the highest degree of correlation, indicating its potential as a crucial biomarker for the modulation of radiotherapy sensitivity in CC.

Role of the Sodium-Dependent Organic Anion Transporter (SOAT/SLC10A6) in Physiology and Pathophysiology

The sodium-dependent organic anion transporter (SOAT, gene symbol SLC10A6) specifically transports 3'- and 17'-monosulfated steroid hormones, such as estrone sulfate and dehydroepiandrosterone sulfate, into specific target cells. These biologically inactive sulfo-conjugated steroids occur in high concentrations in the blood circulation and serve as precursors for the intracrine formation of active estrogens and androgens that contribute to the overall regulation of steroids in many peripheral tissues. Although SOAT expression has been detected in several hormone-responsive peripheral tissues, its quantitative contribution to steroid sulfate uptake in different organs is still not completely clear. Given this fact, the present review provides a comprehensive overview of the current knowledge about the SOAT by summarizing all experimental findings obtained since its first cloning in 2004 and by processing SOAT/SLC10A6-related data from genome-wide protein and mRNA expression databases. In conclusion, despite a significantly increased understanding of the function and physiological significance of the SOAT over the past 20 years, further studies are needed to finally establish it as a potential drug target for endocrine-based therapy of steroid-responsive diseases such as hormone-dependent breast cancer.

The Pathological Effects of Circulating Hydrophobic Bile Acids in Alzheimer's Disease

Recent clinical studies have revealed that the serum levels of toxic hydrophobic bile acids (deoxy cholic acid, lithocholic acid [LCA], and glycoursodeoxycholic acid) are significantly higher in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) when compared to control subjects. The elevated serum bile acids may be the result of hepatic peroxisomal dysfunction. Circulating hydrophobic bile acids are able to disrupt the blood-brain barrier and promote the formation of amyloid-β plaques through enhancing the oxidation of docosahexaenoic acid. Hydrophobic bile acid may find their ways into the neurons via the apical sodium-dependent bile acid transporter. It has been shown that hydrophobic bile acids impose their pathological effects by activating farnesoid X receptor and suppressing bile acid synthesis in the brain, blocking NMDA receptors, lowering brain oxysterol levels, and interfering with 17β-estradiol actions such as LCA by binding to E2 receptors (molecular modelling data exclusive to this paper). Hydrophobic bile acids may interfere with the sonic hedgehog signaling through alteration of cell membrane rafts and reducing brain 24(S)-hydroxycholesterol. This article will 1) analyze the pathological roles of circulating hydrophobic bile acids in the brain, 2) propose therapeutic approaches, and 3) conclude that consideration be given to reducing/monitoring toxic bile acid levels in patients with AD or aMCI, prior/in combination with other treatments.

The role and application of small extracellular vesicles in breast cancer

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related deaths in women worldwide. Currently, patients’ survival remains a challenge in BC due to the lack of effective targeted therapies and the difficult condition of patients with higher aggressiveness, metastasis and drug resistance. Small extracellular vesicles (sEVs), which are nanoscale vesicles with lipid bilayer envelopes released by various cell types in physiological and pathological conditions, play an important role in biological information transfer between cells. There is growing evidence that BC cell-derived sEVs may contribute to the establishment of a favorable microenvironment that supports cancer cells proliferation, invasion and metastasis. Moreover, sEVs provide a versatile platform not only for the diagnosis but also as a delivery vehicle for drugs. This review provides an overview of current new developments regarding the involvement of sEVs in BC pathogenesis, including tumor proliferation, invasion, metastasis, immune evasion, and drug resistance. In addition, sEVs act as messenger carriers carrying a variety of biomolecules such as proteins, nucleic acids, lipids and metabolites, making them as potential liquid biopsy biomarkers for BC diagnosis and prognosis. We also described the clinical applications of BC derived sEVs associated MiRs in the diagnosis and treatment of BC along with ongoing clinical trials which will assist future scientific endeavors in a more organized direction.

Transcriptomics of Parental Care in the Hypothalamic-Septal Region of Female Zebra Finch Brain

(1) Background: The objective of this study was to uncover genomic causes of parental care. Since birds do not lactate and, therefore, do not show the gene expressional changes required for lactation, we investigate gene expression associated with parenting in caring and non-caring females in an avian species, the small passerine bird zebra finch (Taeniopygia guttata). Here, we compare expression patterns in the hypothalamic–septal region since, previously, we showed that this area is activated in parenting females. (2) Methods: Transcriptome sequencing was first applied in a dissected part of the zebra finch brain related to taking care of the nestlings as compared to a control group of social pairs without nestlings. (3) Results: We found genes differentially expressed between caring and non-caring females. When introducing a log2fold change threshold of 1.5, 13 annotated genes were significantly upregulated in breeding pairs, while 39 annotated genes were downregulated. Significant enrichments of dopamine and acetylcholine biosynthetic processes were identified among upregulated pathways, while pro-opiomelanocortin and thyroid hormone pathways were downregulated, suggesting the importance of these systems in parental care. Network analysis further suggested neuro-immunological changes in mothers. (4) Conclusions: The results confirm the roles of several hypothesized major pathways in parental care, whereas novel pathways are also proposed.

Subcellular proteomics of dopamine neurons in the mouse brain

Dopaminergic neurons modulate neural circuits and behaviors via dopamine (DA) release from expansive, long range axonal projections. The elaborate cytoarchitecture of these neurons is embedded within complex brain tissue, making it difficult to access the neuronal proteome using conventional methods. Here, we demonstrate APEX2 proximity labeling within genetically targeted neurons in the mouse brain, enabling subcellular proteomics with cell-type specificity. By combining APEX2 biotinylation with mass spectrometry, we mapped the somatodendritic and axonal proteomes of midbrain dopaminergic neurons. Our dataset reveals the proteomic architecture underlying proteostasis, axonal metabolism, and neurotransmission in these neurons. We find that most proteins encoded by DA neuron-enriched genes are localized within striatal dopaminergic axons, including ion channels with previously undescribed axonal localization. These proteomic datasets provide a resource for neuronal cell biology, and this approach can be readily adapted for study of other neural cell types.

SLC10A7, an orphan member of the SLC10 family involved in congenital disorders of glycosylation

SLC10A7, encoded by the so-called SLC10A7 gene, is the seventh member of a human sodium/bile acid cotransporter family, known as the SLC10 family. Despite similarities with the other members of the SLC10 family, SLC10A7 does not exhibit any transport activity for the typical SLC10 substrates and is then considered yet as an orphan carrier. Recently, SLC10A7 mutations have been identified as responsible for a new Congenital Disorder of Glycosylation (CDG). CDG are a family of rare and inherited metabolic disorders, where glycosylation abnormalities lead to multisystemic defects. SLC10A7-CDG patients presented skeletal dysplasia with multiple large joint dislocations, short stature and amelogenesis imperfecta likely mediated by glycosaminoglycan (GAG) defects. Although it has been demonstrated that the transporter and substrate specificities of SLC10A7, if any, differ from those of the main members of the protein family, SLC10A7 seems to play a role in Ca²⁺ regulation and is involved in proper glycosaminoglycan biosynthesis, especially heparan-sulfate, and N-glycosylation. This paper will review our current knowledge on the known and predicted structural and functional properties of this fascinating protein, and its link with the glycosylation process.

Gene expression in the amygdala and hippocampus of cyclic and acyclic gilts

Age at first estrus is the earliest phenotypic indicator of future reproductive success of gilts. Prebreeding anestrus is a major reason for reproductive failure leading to culling of replacement gilts. The two types of prebreeding anestrus are delay in attaining puberty (prepubertal anestrus, PPA) and silent ovulation (behavioral anestrus, BA). Neural tissues such as amygdala and hippocampus play a major role in regulating sexual behavior, social interactions, and receptivity to males. Differences in gene expression in the amygdala and hippocampus of gilts were analyzed in three comparisons: 1) PPA cases and cyclic controls at follicular phase of estrous cycle, 2) BA cases and cyclic controls at luteal phase of estrous cycle, and 3) gilts at different stages of the ovarian cycle (cyclic gilts at follicular phase and luteal phase of estrous cycle) to gain functional understanding of how these rarely studied tissues may differ between pubertal phenotypes and different stages of the estrous cycle of gilts. Differentially expressed genes (DEG) between PPA and BA cases and their respective cyclic controls were involved in neurological and behavioral disorders as well as nervous system functions that could directly or indirectly involved in development of behaviors related to estrus. The comparison between cyclic follicular and luteal phase control gilts identified the greatest number of DEG in the hippocampus and amygdala. These DEG were involved in adult neurogenesis and neural synapse (e.g., GABAergic, dopamine, cholinergic), suggesting that these tissues undergo structural changes and synaptic plasticity in gilts. This is the first report to demonstrate that the stage of estrous cycle is associated with dynamic changes in gene expression within porcine hippocampus and amygdala and indicates a role of gonadal steroids in regulating their biology.

Localization, proteomics, and metabolite profiling reveal a putative vesicular transporter for UDP-glucose

Vesicular neurotransmitter transporters (VNTs) mediate the selective uptake and enrichment of small-molecule neurotransmitters into synaptic vesicles (SVs) and are therefore a major determinant of the synaptic output of specific neurons. To identify novel VNTs expressed on SVs (thus identifying new neurotransmitters and/or neuromodulators), we conducted localization profiling of 361 solute carrier (SLC) transporters tagging with a fluorescent protein in neurons, which revealed 40 possible candidates through comparison with a known SV marker. We parallelly performed proteomics analysis of immunoisolated SVs and identified seven transporters in overlap. Ultrastructural analysis further supported that one of the transporters, SLC35D3, localized to SVs. Finally, by combining metabolite profiling with a radiolabeled substrate transport assay, we identified UDP-glucose as the principal substrate for SLC35D3. These results provide new insights into the functional role of SLC transporters in neurotransmission and improve our understanding of the molecular diversity of chemical transmitters.

Hidden proteome of synaptic vesicles in the mammalian brain

Mammalian central synapses of diverse functions contribute to highly complex brain organization, but the molecular basis of synaptic diversity remains open. This is because current synapse proteomics are restricted to the “average” composition of abundant synaptic proteins. Here, we demonstrate a subcellular proteomic workflow that can identify and quantify the deep proteome of synaptic vesicles, including previously missing proteins present in a small percentage of central synapses. This synaptic vesicle proteome revealed many proteins of physiological and pathological relevance, particularly in the low-abundance range, thus providing a resource for future investigations on diversified synaptic functions and neuronal dysfunctions.

Current proteomic studies clarified canonical synaptic proteins that are common to many types of synapses. However, proteins of diversified functions in a subset of synapses are largely hidden because of their low abundance or structural similarities to abundant proteins. To overcome this limitation, we have developed an “ultra-definition” (UD) subcellular proteomic workflow. Using purified synaptic vesicle (SV) fraction from rat brain, we identified 1,466 proteins, three times more than reported previously. This refined proteome includes all canonical SV proteins, as well as numerous proteins of low abundance, many of which were hitherto undetected. Comparison of UD quantifications between SV and synaptosomal fractions has enabled us to distinguish SV-resident proteins from potential SV-visitor proteins. We found 134 SV residents, of which 86 are present in an average copy number per SV of less than one, including vesicular transporters of nonubiquitous neurotransmitters in the brain. We provide a fully annotated resource of all categorized SV-resident and potential SV-visitor proteins, which can be utilized to drive novel functional studies, as we characterized here Aak1 as a regulator of synaptic transmission. Moreover, proteins in the SV fraction are associated with more than 200 distinct brain diseases. Remarkably, a majority of these proteins was found in the low-abundance proteome range, highlighting its pathological significance. Our deep SV proteome will provide a fundamental resource for a variety of future investigations on the function of synapses in health and disease.

Functional and molecular heterogeneity of D2R neurons along dorsal ventral axis in the striatum

Action control is a key brain function determining the survival of animals in their environment. In mammals, neurons expressing dopamine D2 receptors (D2R) in the dorsal striatum (DS) and the nucleus accumbens (Acb) jointly but differentially contribute to the fine regulation of movement. However, their region-specific molecular features are presently unknown. By combining RNAseq of striatal D2R neurons and histological analyses, we identified hundreds of novel region-specific molecular markers, which may serve as tools to target selective subpopulations. As a proof of concept, we characterized the molecular identity of a subcircuit defined by WFS1 neurons and evaluated multiple behavioral tasks after its temporally-controlled deletion of D2R. Consequently, conditional D2R knockout mice displayed a significant reduction in digging behavior and an exacerbated hyperlocomotor response to amphetamine. Thus, targeted molecular analyses reveal an unforeseen heterogeneity in D2R-expressing striatal neuronal populations, underlying specific D2R's functional features in the control of specific motor behaviors.

Seasonal Theanine Accumulation and Related Gene Expression in the Roots and Leaf Buds of Tea Plants (Camellia Sinensis L.)

Theanine, a unique and abundant non-proteinogenic amino acid in tea, confers to the tea infusion its umami taste and multiple health benefits. Its content in new tea shoots is dynamic in winter and spring. However, its seasonal accumulation pattern and the underlying regulation mechanism of tea plants remain largely unknown. In this study, we measured the theanine contents in the roots and leaf buds of 13 tea cultivars at four time points from winter to spring (Dec. 12, Mar. 1, Mar. 23, and Apr. 13). We found theanine accumulated significantly in the roots to as high as ∼6% dry weight. We found theanine content in the roots was constant or slightly decreased on Mar. 1 compared with Dec.12 but increased consistently on Mar. 23 and then decreased on Apr. 13 in all 13 cultivars. In the leaf buds, theanine content kept increasing from Mar. 1 to Mar. 23 and decreasing from Apr. 13 in most of the 13 cultivars, meaning it was probably both season- and developmental stage-dependent. The expression of theanine biosynthesis and amino acid transporter genes in the roots and buds at the four time points was then examined. The correlation analyses between the gene expression and theanine content suggested the expression of theanine-biosynthesis genes was generally and negatively correlated with theanine content; however, the expression of amino acid transporter genes including CsLHT was generally and positively correlated with theanine contents. Finally, we showed that CsLHT has theanine transport activity. Taken together, this study provided insight into the seasonal regulation of theanine biosynthesis and transport in tea plants during winter and spring.

Characterization of Dmrt3-Derived Neurons Suggest a Role within Locomotor Circuits

Neuronal networks within the spinal cord, collectively known as the central pattern generator (CPG), coordinate rhythmic movements underlying locomotion. The transcription factor doublesex and mab-3-related transcription factor 3 (DMRT3) is involved in the differentiation of the dorsal interneuron 6 class of spinal cord interneurons. In horses, a non-sense mutation in the Dmrt3 gene has major effects on gaiting ability, whereas mice lacking the Dmrt3 gene display impaired locomotor activity. Although the Dmrt3 gene is necessary for normal spinal network formation and function in mice, a direct role for Dmrt3-derived neurons in locomotor-related activities has not been demonstrated. Here we present the characteristics of the Dmrt3-derived spinal cord interneurons. Using transgenic mice of both sexes, we characterized interneurons labeled by their expression of Cre driven by the endogenous Dmrt3 promoter. We used molecular, retrograde tracing and electrophysiological techniques to examine the anatomical, morphological, and electrical properties of the Dmrt3-Cre neurons. We demonstrate that inhibitory Dmrt3-Cre neurons receive extensive synaptic inputs, innervate surrounding CPG neurons, intrinsically regulate CPG neuron's electrical activity, and are rhythmically active during fictive locomotion, bursting at frequencies independent to the ventral root output. The present study provides novel insights on the character of spinal Dmrt3-derived neurons, data demonstrating that these neurons participate in locomotor coordination.SIGNIFICANCE STATEMENT In this work, we provide evidence for a role of the Dmrt3 interneurons in spinal cord locomotor circuits as well as molecular and functional insights on the cellular and microcircuit level of the Dmrt3-expressing neurons in the spinal cord. Dmrt3 neurons provide the first example of an interneuron population displaying different oscillation frequencies. This study presents novel findings on an under-reported population of spinal cord neurons, which will aid in deciphering the locomotor network and will facilitate the design and development of therapeutics for spinal cord injury and motor disorders.

Induction of the Immunoproteasome Subunit Lmp7 Links Proteostasis and Immunity in α-Synuclein Aggregation Disorders

Accumulation of aggregated α-synuclein into Lewy bodies is thought to contribute to the onset and progression of dopaminergic neuron degeneration in Parkinson's disease (PD) and related disorders. Although protein aggregation is associated with perturbation of proteostasis, how α-synuclein aggregation affects the brain proteome and signaling remains uncertain. In a mouse model of α-synuclein aggregation, 6% of 6215 proteins and 1.6% of 8183 phosphopeptides changed in abundance, indicating conservation of proteostasis and phosphorylation signaling. The proteomic analysis confirmed changes in abundance of proteins that regulate dopamine synthesis and transport, synaptic activity and integrity, and unearthed changes in mRNA binding, processing and protein translation. Phosphorylation signaling changes centered on axonal and synaptic cytoskeletal organization and structural integrity. Proteostatic responses included a significant increase in the levels of Lmp7, a component of the immunoproteasome. Increased Lmp7 levels and activity were also quantified in postmortem human brains with PD and dementia with Lewy bodies. Functionally, the immunoproteasome degrades α-synuclein aggregates and generates potentially antigenic peptides. Expression and activity of the immunoproteasome may represent testable targets to induce adaptive responses that maintain proteome integrity and modulate immune responses in protein aggregation disorders.

Sigmoid colon mucosal gene expression supports alterations of neuronal signaling in irritable bowel syndrome with constipation

Peripheral factors likely play a role in at least a subset of irritable bowel syndrome (IBS) patients. Few studies have investigated mucosal gene expression using an unbiased approach. Here, we performed mucosal gene profiling in a sex-balanced sample to identify relevant signaling pathways and gene networks and compare with publicly available profiling data from additional cohorts. Twenty Rome III+ IBS patients [10 IBS with constipation (IBS-C), 10 IBS with diarrhea (IBS-D), 5 men/women each), and 10 age-/sex-matched healthy controls (HCs)] underwent sigmoidoscopy with biopsy for gene microarray analysis, including differential expression, weighted gene coexpression network analysis (WGCNA), gene set enrichment analysis, and comparison with publicly available data. Expression levels of 67 genes were validated in an expanded cohort, including the above samples and 18 additional participants (6 each of IBS-C, IBS-D, HCs) using NanoString nCounter technology. There were 1,270 differentially expressed genes (FDR < 0.05) in IBS-C vs. HCs but none in IBS or IBS-D vs. HCs. WGNCA analysis identified activation of the cAMP/protein kinase A signaling pathway. Nine of 67 genes were validated by the NanoString nCounter technology (FDR < 0.05) in the expanded sample. Comparison with publicly available microarray data from the Mayo Clinic and University of Nottingham supports the reproducibility of 17 genes from the microarray analysis and three of nine genes validated by nCounter in IBS-C vs. HCs. This study supports the involvement of peripheral mechanisms in IBS-C, particularly pathways mediating neuronal signaling. NEW & NOTEWORTHY Peripheral factors play a role in the pathophysiology of irritable bowel syndrome (IBS), which, to date, has been mostly evident in IBS with diarrhea. Here, we show that sigmoid colon mucosal gene expression profiles differentiate IBS with constipation from healthy controls. These profiling data and analysis of additional cohorts also support the concept that peripheral neuronal pathways contribute to IBS pathophysiology.

The MINDVIEW project: First results

We present the first results of the MINDVIEW project. An innovative imaging system for the human brain examination, allowing simultaneous acquisition of PET/MRI images, has been designed and constructed. It consists of a high sensitivity and high resolution PET scanner integrated in a novel, head-dedicated, radio frequency coil for a 3T MRI scanner. Preliminary measurements from the PET scanner show sensitivity 3 times higher than state-of-the-art PET systems that will allow safe repeated studies on the same patient. The achieved spatial resolution, close to 1 mm, will enable differentiation of relevant brain structures for schizophrenia. A cost-effective and simple method of radiopharmaceutical production from ¹¹C-carbon monoxide and a mini-clean room has been demonstrated. It has been shown that ¹¹C-raclopride has higher binding potential in a new VAAT null mutant mouse model of schizophrenia compared to wild type control animals. A significant reduction in TSPO binding has been found in gray matter in a small sample of drug-naïve, first episode psychosis patients, suggesting a reduced number or an altered function of immune cells in brain at early stage schizophrenia.

SLC10A4 regulates IgE-mediated mast cell degranulation in vitro and mast cell-mediated reactions in vivo

Mast cells act as sensors in innate immunity and as effector cells in adaptive immune reactions. Here we demonstrate that SLC10A4, also referred to as the vesicular aminergic-associated transporter, VAAT, modifies mast cell degranulation. Strikingly, Slc10a4 -/- bone marrow-derived mast cells (BMMCs) had a significant reduction in the release of granule-associated mediators in response to IgE/antigen-mediated activation, whereas the in vitro development of mast cells, the storage of the granule-associated enzyme mouse mast cell protease 6 (mMCP-6), and the release of prostaglandin D2 and IL-6 were normal. Slc10a4-deficient mice had a strongly reduced passive cutaneous anaphylaxis reaction and a less intense itching behaviour in response to the mast cell degranulator 48/80. Live imaging of the IgE/antigen-mediated activation showed decreased degranulation and that ATP was retained to a higher degree in mast cell granules lacking SLC10A4. Furthermore, ATP was reduced by two thirds in Slc10a4 -/- BMMCs supernatants in response to IgE/antigen. We speculate that SLC10A4 affects the amount of granule-associated ATP upon IgE/antigen-induced mast cell activation, which affect the release of granule-associated mast cell mediators. In summary, SLC10A4 acts as a regulator of degranulation in vitro and of mast cell-related reactions in vivo.

Recent advances in understanding hepatic drug transport

Cells need to strictly control their internal milieu, a function which is performed by the plasma membrane. Selective passage of molecules across the plasma membrane is controlled by transport proteins. As the liver is the central organ for drug metabolism, hepatocytes are equipped with numerous drug transporters expressed at the plasma membrane. Drug disposition includes absorption, distribution, metabolism, and elimination of a drug and hence multiple passages of drugs and their metabolites across membranes. Consequently, understanding the exact mechanisms of drug transporters is essential both in drug development and in drug therapy. While many drug transporters are expressed in hepatocytes, and some of them are well characterized, several transporters have only recently been identified as new drug transporters. Novel powerful tools to deorphanize (drug) transporters are being applied and show promising results. Although a large set of tools are available for studying transport in vitro and in isolated cells, tools for studying transport in living organisms, including humans, are evolving now and rely predominantly on imaging techniques, e.g. positron emission tomography. Imaging is an area which, certainly in the near future, will provide important insights into "transporters at work" in vivo.

Characterization of cognitive impairments and neurotransmitter changes in a novel transgenic mouse lacking Slc10a4

An orphan member of the solute carrier (SLC) family SLC10, SLC10A4 has been found to be enriched in midbrain and brainstem neurons and has been found to co-localize with and to affect dopamine (DA) homeostasis. We generated an SLC10A4 knockout mouse (Slc10a4(Δ/Δ)) using Cre-targeted recombination, and characterized behavioral measures of motor and cognitive function as well as DA and acetylcholine (ACh) levels in midbrain and brainstem. In agreement with previous studies, Slc10a4 mRNA was preferentially expressed in neurons in the brains of wild-type (Slc10a4(+/+)) mice and was enriched in dopaminergic and cholinergic regions. Slc10a4(Δ/Δ) mice had no impairment in motor function or novelty-induced exploratory behaviors but performed significantly worse in measures of spatial memory and cognitive flexibility. Slc10a4(Δ/Δ) mice also did not differ from Slc10a4(+/+) in measures of anxiety. High-performance liquid chromatography (HPLC) measures on tissue punches taken from the dorsal and ventral striatum reveal a decrease in DA content and a corresponding increase in the metabolite 3,4-dihydroxyphenylacetic acid (DOPAC), indicating an increase in DA turnover. Punches taken from the brainstem revealed a decrease in ACh as compared with Slc10a4(+/+) littermates. Together, these data indicate that loss of SLC10A4 protein results in neurotransmitter imbalance and cognitive impairment.

Expression, sorting and transport studies for the orphan carrier SLC10A4 in neuronal and non-neuronal cell lines and in Xenopus laevis oocytes

Background

SLC10A4 belongs to the solute carrier family SLC10 whose founding members are the Na⁺/taurocholate co-transporting polypeptide (NTCP, SLC10A1) and the apical sodium-dependent bile acid transporter (ASBT, SLC10A2). These carriers maintain the enterohepatic circulation of bile acids between the liver and the gut. SLC10A4 was identified as a novel member of the SLC10 carrier family with the highest phylogenetic relationship to NTCP. The SLC10A4 protein was detected in synaptic vesicles of cholinergic and monoaminergic neurons of the peripheral and central nervous system, suggesting a transport function for any kind of neurotransmitter. Therefore, in the present study, we performed systematic transport screenings for SLC10A4 and also aimed to identify the vesicular sorting domain of the SLC10A4 protein.

Results

We detected a vesicle-like expression pattern of the SLC10A4 protein in the neuronal cell lines SH-SY5Y and CAD. Differentiation of these cells to the neuronal phenotype altered neither SLC10A4 gene expression nor its vesicular expression pattern. Functional transport studies with different neurotransmitters, bile acids and steroid sulfates were performed in SLC10A4-transfected HEK293 cells, SLC10A4-transfected CAD cells and in Xenopus laevis oocytes. For these studies, transport by the dopamine transporter DAT, the serotonin transporter SERT, the choline transporter CHT1, the vesicular monoamine transporter VMAT2, the organic cation transporter Oct1, and NTCP were used as positive control. SLC10A4 failed to show transport activity for dopamine, serotonin, norepinephrine, histamine, acetylcholine, choline, acetate, aspartate, glutamate, gamma-aminobutyric acid, pregnenolone sulfate, dehydroepiandrosterone sulfate, estrone-3-sulfate, and adenosine triphosphate, at least in the transport assays used. When the C-terminus of SLC10A4 was replaced by the homologous sequence of NTCP, the SLC10A4-NTCP chimeric protein revealed clear plasma membrane expression in CAD and HEK293 cells. But this chimera also did not show any transport activity, even when the N-terminal domain of SLC10A4 was deleted by mutagenesis.

Conclusions

Although different kinds of assays were used to screen for transport function, SLC10A4 failed to show transport activity for a series of neurotransmitters and neuromodulators, indicating that SLC10A4 does not seem to represent a typical neurotransmitter transporter such as DAT, SERT, CHT1 or VMAT2.