Synaptic Vesicle Glycoprotein Research Articles

Pharmacokinetic Characterization of [18F]UCB-H PET Radiopharmaceutical in the Rat Brain.

The synaptic vesicle glycoprotein 2A (SV2A), a protein essential to the proper nervous system function, is found in presynaptic vesicles. Thus, SV2A targeting, using dedicated radiotracers combined with positron emission tomography (PET), allows the assessment of synaptic density in the living brain. The first-in-class fluorinated SV2A specific radioligand, [18F]UCB-H, is now available at high activity through an efficient radiosynthesis compliant with current good manufacturing practices (cGMP). We report here a noninvasive method to quantify [18F]UCB-H binding in rat brain with microPET. Validation study in rats confirmed the need of high enantiomeric purity to target SV2A in vivo. We demonstrated the reliability of a population-based input function to quantify SV2A in preclinical microPET setting. Finally, we investigated the in vivo metabolism of [18F]UCB-H and confirmed the negligible amount of radiometabolites in the rat brain. Hence, the in vivo quantification of SV2A using [18F]UCB-H microPET seems a promising tool for the assessment of the synaptic density in the rat brain, and opens the way for longitudinal follow-up in neurodegenerative disease rodent models.

Therapeutic Role of Synaptic Vesicle Glycoprotein 2A (SV2A) in Modulating Epileptogenesis.

Dysfunction of synaptic neurotransmitter release is closely involved in the pathogenesis of various central nervous system diseases. Synaptic vesicle glycoprotein 2A (SV2A) is a membrane protein specifically expressed in synaptic vesicles and it modulates action potential-dependent neurotransmitter release in the brain. Since 1) SV2A-knockout mice exhibit severe convulsive seizures, 2) SV2A expression in the brain is reportedly altered in various epileptic disorders both in animal models (e.g., kindling and genetic models) and humans (e.g., intractable temporal lobe epilepsy and focal cortical dysplasia) and 3) SV2A serves as a specific binding site for the antiepileptic drug, levetiracetam and its analogues, it is considered that SV2A is involved in the pathogenesis and treatment of epilepsy. In addition, a recent clinical study demonstrated that a missense mutation in the SV2A gene caused intractable epilepsy with involuntary movements and developmental retardation, illustrating a causative role of SV2A dysfunction in epilepsy. Although the functional mechanisms of SV2A in regulating epileptogenesis remain unknown, studies using animals carrying the Sv2a missense mutation showed that the dysfunction of SV2A preferentially disrupts action potential-induced γ-aminiobutyric acid (GABA), but not glutamate, released in the limbic regions (i.e., hippocampus and amygdala) and markedly facilitates kindling epileptogenesis. All these evidences indicate that the SV2A-GABAergic system plays a crucial role in modulating epileptogenesis and encourages research on the novel antiepileptic agents which enhance SV2A function.

U18666A, an activator of sterol regulatory element binding protein pathway, modulates presynaptic dopaminergic phenotype of SH-SY5Y neuroblastoma cells.

The therapeutic use of statins has been associated to a reduced risk of Parkinson's disease (PD) and may hold neuroprotective potential by counteracting the degeneration of dopaminergic neurons. Transcriptional activation of the sterol regulatory element-binding protein (SREBP) is one of the major downstream signaling pathways triggered by the cholesterol-lowering effect of statins. In a previous study in neuroblastoma cells, we have shown that statins consistently induce the upregulation of presynaptic dopaminergic proteins and changes of their function and these effects were accompanied by downstream activation of SREBP. In this study, we aimed to determine the direct role of SREBP pathway in the modulation of dopaminergic phenotype. We demonstrate that treatment of SH-SY5Y cells with U18666A, an SREBP activator, increases the translocation of SREBPs into the nucleus, increases the expression of SREBP-1, SREBP-2, and of the presynaptic dopaminergic markers such as vesicular monoamine transporter 2, synaptic vesicle glycoprotein 2 A and 2 C, synaptogyrin-3, and tyrosine hydroxylase. The addition of SREBP inhibitor, PF-429242, blocks the increase of U18666A-induced expression of SREBPs and presynaptic markers. Our results, in line with previously reported effects of statins, demonstrate that direct stimulation of SREBP translocation is associated to differentiation toward a dopaminergic-like phenotype and suggest that SREBP-mediated transcriptional activity may lead to the restoration of the presynaptic dopamine markers and may contribute to neuroprotection of dopaminergic neurons. These findings further support the potential protective role of statin in PD and shed light upon SREBP as a potential new target for developing disease-modifying treatment in PD.

Crystal Structure of the Receptor-Binding Domain of Botulinum Neurotoxin Type HA, Also Known as Type FA or H.

Botulinum neurotoxins (BoNTs), which have been exploited as cosmetics and muscle-disorder treatment medicines for decades, are well known for their extreme neurotoxicity to humans. They pose a potential bioterrorism threat because they cause botulism, a flaccid muscular paralysis-associated disease that requires immediate antitoxin treatment and intensive care over a long period of time. In addition to the existing seven established BoNT serotypes (BoNT/A–G), a new mosaic toxin type termed BoNT/HA (aka type FA or H) was reported recently. Sequence analyses indicate that the receptor-binding domain (HC) of BoNT/HA is ~84% identical to that of BoNT/A1. However, BoNT/HA responds differently to some potent BoNT/A-neutralizing antibodies (e.g., CR2) that target the HC. Therefore, it raises a serious concern as to whether BoNT/HA poses a new threat to our biosecurity. In this study, we report the first high-resolution crystal structure of BoNT/HA-HC at 1.8 Å. Sequence and structure analyses reveal that BoNT/HA and BoNT/A1 are different regarding their binding to cell-surface receptors including both polysialoganglioside (PSG) and synaptic vesicle glycoprotein 2 (SV2). Furthermore, the new structure also provides explanations for the ~540-fold decreased affinity of antibody CR2 towards BoNT/HA compared to BoNT/A1. Taken together, these new findings advance our understanding of the structure and function of this newly identified toxin at the molecular level, and pave the way for the future development of more effective countermeasures.

Synaptic vesicle glycoprotein 2C (SV2C) modulates dopamine release and is disrupted in Parkinson disease.

Members of the synaptic vesicle glycoprotein 2 (SV2) family of proteins are involved in synaptic function throughout the brain. The ubiquitously expressed SV2A has been widely implicated in epilepsy, although SV2C with its restricted basal ganglia distribution is poorly characterized. SV2C is emerging as a potentially relevant protein in Parkinson disease (PD), because it is a genetic modifier of sensitivity to l-DOPA and of nicotine neuroprotection in PD. Here we identify SV2C as a mediator of dopamine homeostasis and report that disrupted expression of SV2C within the basal ganglia is a pathological feature of PD. Genetic deletion of SV2C leads to reduced dopamine release in the dorsal striatum as measured by fast-scan cyclic voltammetry, reduced striatal dopamine content, disrupted α-synuclein expression, deficits in motor function, and alterations in neurochemical effects of nicotine. Furthermore, SV2C expression is dramatically altered in postmortem brain tissue from PD cases but not in Alzheimer disease, progressive supranuclear palsy, or multiple system atrophy. This disruption was paralleled in mice overexpressing mutated α-synuclein. These data establish SV2C as a mediator of dopamine neuron function and suggest that SV2C disruption is a unique feature of PD that likely contributes to dopaminergic dysfunction.

Synaptic Vesicle Glycoprotein 2A Ligands in the Treatment of Epilepsy and Beyond.

The synaptic vesicle glycoprotein SV2A belongs to the major facilitator superfamily (MFS) of transporters and is an integral constituent of synaptic vesicle membranes. SV2A has been demonstrated to be involved in vesicle trafficking and exocytosis, processes crucial for neurotransmission. The anti-seizure drug levetiracetam was the first ligand to target SV2A and displays a broad spectrum of anti-seizure activity in various preclinical models. Several lines of preclinical and clinical evidence, including genetics and protein expression changes, support an important role of SV2A in epilepsy pathophysiology. While the functional consequences of SV2A ligand binding are not fully elucidated, studies suggest that subsequent SV2A conformational changes may contribute to seizure protection. Conversely, the recently discovered negative SV2A modulators, such as UCB0255, counteract the anti-seizure effect of levetiracetam and display procognitive properties in preclinical models. More broadly, dysfunction of SV2A may also be involved in Alzheimer’s disease and other types of cognitive impairment, suggesting potential novel therapies for levetiracetam and its congeners. Furthermore, emerging data indicate that there may be important roles for two other SV2 isoforms (SV2B and SV2C) in the pathogenesis of epilepsy, as well as other neurodegenerative diseases. Utilization of recently developed SV2A positron emission tomography ligands will strengthen and reinforce the pharmacological evidence that SV2A is a druggable target, and will provide a better understanding of its role in epilepsy and other neurological diseases, aiding in further defining the full therapeutic potential of SV2A modulation.

Enabling Efficient Positron Emission Tomography (PET) Imaging of Synaptic Vesicle Glycoprotein 2A (SV2A) with a Robust and One-Step Radiosynthesis of a Highly Potent 18F-Labeled Ligand ([18F]UCB-H).

We herein describe the straightforward synthesis of a stable pyridyl(4-methoxyphenyl)iodonium salt and its [18F] radiolabeling within a one-step, fully automated and cGMP compliant radiosynthesis of [18F]UCB-H ([18F]7), a PET tracer for the imaging of synaptic vesicle glycoprotein 2A (SV2A). Over the course of 1 year, 50 automated productions provided 34 ± 2% of injectable [18F]7 from up to 285 GBq (7.7 Ci) of [18F]fluoride in 50 min (uncorrected radiochemical yield, specific activity of 815 ± 185 GBq/μmol). The successful implementation of our synthetic strategy within routine, high-activity, and cGMP productions attests to its practicality and reliability for the production of large doses of [18F]7. In addition to enabling efficient and cost-effective clinical research on a range of neurological pathologies through the imaging of SV2A, this work further demonstrates the real value of iodonium salts for the cGMP 18F-PET tracer manufacturing industry, and their ability to fulfill practical and regulatory requirements in that field.

Expression of messenger molecules and receptors in rat and human sphenopalatine ganglion indicating therapeutic targets.

BackgroundMigraine and Cluster Headache (CH) are two primary headaches with severe disease burden. The disease expression and the mechanisms involved are poorly known. In some attacks of migraine and in most attacks of CH, there is a release of vasoactive intestinal peptide (VIP) originating from parasympathetic cranial ganglia such as the sphenopalatine ganglion (SPG). Patients suffering from these diseases are often deprived of effective drugs. The aim of the study was to examine the localization of the botulinum toxin receptor element synaptic vesicle glycoprotein 2A (SV-2A) and the vesicular docking protein synaptosomal-associated protein 25 (SNAP25) in human and rat SPG. Additionally the expression of the neurotransmitters pituitary adenylate cyclase activating polypeptide (PACAP-38), nitric oxide synthase (nNOS), VIP and 5-hydroxttryptamine subtype receptors (5-HT1B,1D,1F) were examined.MethodsSPG from adult male rats and from humans, the later removed at autopsy, were prepared for immunohistochemistry using specific antibodies against neurotransmitters, 5-HT1B,1D,1F receptors, and botulinum toxin receptor elements.ResultsWe found that the selected neurotransmitters and 5-HT receptors were expressed in rat and human SPG. In addition, we found SV2-A and SNAP25 expression in both rat and human SPG. We report that all three 5-HT receptors studied occur in neurons and satellite glial cells (SGCs) of the SPG. 5-HT1B receptors were in addition found in the walls of intraganglionic blood vessels.ConclusionsRecent focus on the SPG has emphasized the role of parasympathetic mechanisms in the pathophysiology of mainly CH. The development of next generation’s drugs and treatment of cranial parasympathetic symptoms, mediated through the SPG, can be modulated by treatment with BoNT-A and 5-HT receptor agonists.

Only the complex N559-glycan in the synaptic vesicle glycoprotein 2C mediates high affinity binding to botulinum neurotoxin serotype A1.

The extraordinary potency of botulinum neurotoxins (BoNTs) is mediated by their high neurospecificity, targeting peripheral cholinergic motoneurons leading to flaccid paralysis and successive respiratory failure. Complex polysialo gangliosides accumulate BoNTs on the plasma membrane and facilitate subsequent binding to synaptic vesicle membrane proteins which results in toxin endocytosis. The luminal domain 4 (LD4) of the three synaptic vesicle glycoprotein 2 (SV2) isoforms A-C mediates uptake of the clinically most relevant serotype BoNT/A1. SV2C-LD4 exhibits the strongest protein-protein interaction and comprises five putative N-glycosylation sites (PNG sites). Here, we expressed human SV2C-LD4 fused to human IgG-Fc in prokaryotic and eukaryotic expression systems to analyse the effect of N-glycosylation of SV2C on the interaction with BoNT/A1. Mass spectrometric analysis of gSV2CLD-Fc demonstrates glycosylation of N534, N559 and N565, the latter two residing at the BoNT/A interface. Mutational analysis demonstrates that only the N559-glycan, but not N565-glycan increases affinity of BoNT/A for human gSV2C-LD4. The N559-glycan was characterised as a complex core-fucosylated typewith a heterogeneity ranging up to tetra-antennary structure with bisecting N-acetylglucosamine which can establish extensive interactions with BoNT/A. The mutant gSV2CLD-Fc N559A displayed a 50-fold increased dissociation rate kd resulting in an overall 12-fold decreased binding affinity in surface plasmon resonance (SPR) experiments. The delayed dissociation might provide BoNT/A more time for endocytosis into synaptic vesicles. In conclusion, we show the importance of the complex N559-glycan of SV2C-LD4, adding a third anchor point beside a ganglioside and the SV2C-LD4 peptide, for BoNT/A neuronal cell surface binding and uptake.

Synaptic vesicle glycoprotein 2C modulates vesicular dopamine release and contributes to behaviors associated with reward

Synaptic vesicle glycoprotein 2C modulates vesicular dopamine release and contributes to behaviors associated with reward

Seeing synapses misfiring

Neurology Nerve junctions (or synapses) electrically transmit (or fire) information from one neuron to another. Many diseases are characterized by misfiring synapses. Finnema et al. have developed a noninvasive imaging approach that targets the synaptic vesicle glycoprotein 2A. Now human synapses can be observed firing in the living brain. In the brains of patients with epilepsy, synaptic density was found to be asymmetric, which is consistent with damage to certain regions. Thus, this imaging method permits monitoring of synaptic loss in the brains of people with various neurological and psychiatric diseases, which could contribute prognostic information. ![Figure][1] Positron emission tomography image of a subject with epilepsy PHOTO: FINNEMA ET AL. Sci. Transl. Med. 8 , 348ra96 (2016). [1]: pending:yes

A Missense Mutation of the Gene Encoding Synaptic Vesicle Glycoprotein 2A (SV2A) Confers Seizure Susceptibility by Disrupting Amygdalar Synaptic GABA Release

Synaptic vesicle glycoprotein 2A (SV2A) is specifically expressed in the membranes of synaptic vesicles and modulates action potential-dependent neurotransmitter release. To explore the role of SV2A in the pathogenesis of epileptic disorders, we recently generated a novel rat model (Sv2aL174Q rat) carrying a missense mutation of the Sv2a gene and showed that the Sv2aL174Q rats were hypersensitive to kindling development (Tokudome et al., 2016). Here, we further conducted behavioral and neurochemical studies to clarify the pathophysiological mechanisms underlying the seizure vulnerability in Sv2aL174Q rats. Sv2aL174Q rats were highly susceptible to pentylenetetrazole (PTZ)-induced seizures, yielding a significantly higher seizure scores and seizure incidence than the control animals. Brain mapping analysis of Fos expression, a biological marker of neural excitation, revealed that the seizure threshold level of PTZ region-specifically elevated Fos expression in the amygdala in Sv2aL174Q rats. In vivo microdialysis study showed that the Sv2aL174Q mutation preferentially reduced high K+ (depolarization)-evoked GABA release, but not glutamate release, in the amygdala. In addition, specific control of GABA release by SV2A was supported by its predominant expression in GABAergic neurons, which were co-stained with antibodies against SV2A and glutamate decarboxylase 1. The present results suggest that dysfunction of SV2A by the missense mutation elevates seizure susceptibility in rats by preferentially disrupting synaptic GABA release in the amygdala, illustrating the crucial role of amygdalar SV2A-GABAergic system in epileptogenesis.

Synaptic vesicle glycoprotein 2A (SV2A) regulates kindling epileptogenesis via GABAergic neurotransmission.

Synaptic vesicle glycoprotein 2A (SV2A) is a prototype synaptic vesicle protein regulating action potential-dependent neurotransmitters release. SV2A also serves as a specific binding site for certain antiepileptics and is implicated in the treatment of epilepsy. Here, to elucidate the role of SV2A in modulating epileptogenesis, we generated a novel rat model (Sv2aL174Q rat) carrying a Sv2a-targeted missense mutation (L174Q) and analyzed its susceptibilities to kindling development. Although animals homozygous for the Sv2aL174Q mutation exhibited normal appearance and development, they are susceptible to pentylenetetrazole (PTZ) seizures. In addition, development of kindling associated with repeated PTZ treatments or focal stimulation of the amygdala was markedly facilitated by the Sv2aL174Q mutation. Neurochemical studies revealed that the Sv2aL174Q mutation specifically reduced depolarization-induced GABA, but not glutamate, release in the hippocampus without affecting basal release or the SV2A expression level in GABAergic neurons. In addition, the Sv2aL174Q mutation selectively reduced the synaptotagmin1 (Syt1) level among the exocytosis-related proteins examined. The present results demonstrate that dysfunction of SV2A due to the Sv2aL174Q mutation impairs the synaptic GABA release by reducing the Syt1 level and facilitates the kindling development, illustrating the crucial role of SV2A-GABA system in modulating kindling epileptogenesis.

Botulinum Neurotoxin Serotype A Recognizes Its Protein Receptor SV2 by a Different Mechanism than Botulinum Neurotoxin B Synaptotagmin.

Botulinum neurotoxins (BoNTs) exhibit extraordinary potency due to their exquisite neurospecificity, which is achieved by dual binding to complex polysialo-gangliosides and synaptic vesicle proteins. The luminal domain 4 (LD4) of the three synaptic vesicle glycoprotein 2 isoforms, SV2A‐C, identified as protein receptors for the most relevant serotype BoNT/A, binds within the 50 kDa cell binding domain HC of BoNT/A. Here, we deciphered the BoNT/A‐SV2 interactions in more detail. In pull down assays, the binding of HCA to SV2-LD4 isoforms decreases from SV2C >> SV2A > SV2B. A binding constant of 200 nM was determined for BoNT/A to rat SV2C-LD4 in GST pull down assay. A similar binding constant was determined by surface plasmon resonance for HCA to rat SV2C and to human SV2C, the latter being slightly lower due to the substitution L563F in LD4. At pH 5, as measured in acidic synaptic vesicles, the binding constant of HCA to hSV2C is increased more than 10-fold. Circular dichroism spectroscopy reveals that the quadrilateral helix of SV2C-LD4 already exists in solution prior to BoNT/A binding. Hence, the BoNT/A‐SV2C interaction is of different nature compared to BoNT/B‐Syt-II. In particular, the preexistence of the quadrilateral β-sheet helix of SV2 and its pH-dependent binding to BoNT/A via backbone–backbone interactions constitute major differences. Knowledge of the molecular details of BoNT/A‐SV2 interactions drives the development of high affinity peptides to counteract BoNT/A intoxications or to capture functional BoNT/A variants in innovative detection systems for botulism diagnostic.

Brivaracetam: First Global Approval.

Brivaracetam (Briviact(®)), a 4-n-propyl analogue of levetiracetam developed by UCB Pharma, has been approved in the EU as an adjunctive therapy for the treatment of partial-onset seizures. Brivaracetam binds to synaptic vesicle glycoprotein 2a (SV2A) in the brain with greater selectivity and 15- to 30-fold higher affinity than levetiracetam, as demonstrated in preclinical models, and has demonstrated efficacy in reducing the frequency of partial onset seizures in clinical trials. This article summarizes the milestones in the development of brivaracetam leading to this first approval for use as adjunctive therapy for uncontrolled partial-onset seizures in adults with epilepsy.

Role of DHA in aging-related changes in mouse brain synaptic plasma membrane proteome

Aging has been related to diminished cognitive function, which could be a result of ineffective synaptic function. We have previously shown that synaptic plasma membrane proteins supporting synaptic integrity and neurotransmission were downregulated in docosahexaenoic acid (DHA)–deprived brains, suggesting an important role of DHA in synaptic function. In this study, we demonstrate aging-induced synaptic proteome changes and DHA-dependent mitigation of such changes using mass spectrometry–based protein quantitation combined with western blot or messenger RNA analysis. We found significant reduction of 15 synaptic plasma membrane proteins in aging brains including fodrin-α, synaptopodin, postsynaptic density protein 95, synaptic vesicle glycoprotein 2B, synaptosomal-associated protein 25, synaptosomal-associated protein-α, N-methyl-D-aspartate receptor subunit epsilon-2 precursor, AMPA2, AP2, VGluT1, munc18-1, dynamin-1, vesicle-associated membrane protein 2, rab3A, and EAAT1, most of which are involved in synaptic transmission. Notably, the first 9 proteins were further reduced when brain DHA was depleted by diet, indicating that DHA plays an important role in sustaining these synaptic proteins downregulated during aging. Reduction of 2 of these proteins was reversed by raising the brain DHA level by supplementing aged animals with an omega-3 fatty acid sufficient diet for 2 months. The recognition memory compromised in DHA-depleted animals was also improved. Our results suggest a potential role of DHA in alleviating aging-associated cognitive decline by offsetting the loss of neurotransmission-regulating synaptic proteins involved in synaptic function.

Synthesis and Preclinical Evaluation of 11C-UCB-J as a PET Tracer for Imaging the Synaptic Vesicle Glycoprotein 2A in the Brain.

The synaptic vesicle glycoprotein 2A (SV2A) is found in secretory vesicles in neurons and endocrine cells. PET with a selective SV2A radiotracer will allow characterization of drugs that modulate SV2A (e.g., antiepileptic drugs) and potentially could be a biomarker of synaptic density (e.g., in neurodegenerative disorders). Here we describe the synthesis and characterization of the SV2A PET radiotracer (11)C-UCB-J ((R)-1-((3-((11)C-methyl-(11)C)pyridin-4-yl)methyl)-4-(3,4,5-trifluorophenyl)pyrrolidin-2-one) in nonhuman primates, including whole-body biodistribution. (11)C-UCB-J was prepared by C-(11)C-methylation of the 3-pyridyl trifluoroborate precursor with (11)C-methyl iodide via the Suzuki-Miyaura cross-coupling method. Rhesus macaques underwent multiple scans including coinjection with unlabeled UCB-J (17, 50, and 150 μg/kg) or preblocking with the antiepileptic drug levetiracetam at 10 and 30 mg/kg. Scans were acquired for 2 h with arterial sampling and metabolite analysis to measure the input function. Regional volume of distribution (VT) was estimated using the 1-tissue-compartment model. Target occupancy was assessed using the occupancy plot; the dissociation constant (Kd) was determined by fitting self-blocking occupancies to a 1-site model, and the maximum number of receptor binding sites (Bmax) values were derived from baseline VT and from the estimated Kd and the nondisplaceable distribution volume (VND). (11)C-UCB-J was synthesized with greater than 98% purity. (11)C-UCB-J exhibited high free fraction (0.46 ± 0.02) and metabolized at a moderate rate (39% ± 5% and 24% ± 3% parent remaining at 30 and 90 min) in plasma. In the monkey brain, (11)C-UCB-J displayed high uptake and fast kinetics. VT was high (∼25-55 mL/cm(3)) in all gray matter regions, consistent with the ubiquitous expression of SV2A. Preblocking with 10 and 30 mg/kg of levetiracetam resulted in approximately 60% and 90% occupancy, respectively. Analysis of the self-blocking scans yielded a Kd estimate of 3.4 nM and Bmax of 125-350 nM, in good agreement with the in vitro inhibition constant (Ki) of 6.3 nM and regional Bmax in humans. Whole-body biodistribution revealed that the liver and the brain are the dose-limiting organs for males and females, respectively. (11)C-UCB-J exhibited excellent characteristics as an SV2A PET radiotracer in nonhuman primates. The radiotracer is currently undergoing first-in-human evaluation.

Harnessing the trophic and modulatory potential of statins in a dopaminergic cell line.

The identification of an effective disease-modifying treatment for the neurodegenerative progression in Parkinson's disease (PD) remains a major challenge. Epidemiological studies have reported that intake of statins, cholesterol lowering drugs, could be associated to a reduced risk of developing PD. In-vivo studies suggest that statins may reduce the severity of dopaminergic neurodegeneration. The trophic potential of statins and their impact on the expression of dopaminergic synaptic markers and dopamine (DA) transport function in SH-SY5Y cells has been investigated. The findings showed that statin treatment induces neurite outgrowth involving a specific effect on the complexity of the neurite branching pattern. Statins increased the levels of presynaptic dopaminergic biomarkers such as vesicular monoamine transporter 2 (VMAT2), synaptic vesicle glycoproteins 2A and 2C (SV2C), and synaptogyrin-3 (SYNGR3). Gene expression analysis confirmed a rapid statin-induced up-regulation of VMAT2-, SV2C-, and SYNGR3-mRNA levels. Assessment of [(3) H]DA transport in statin-treated cells showed a reduction in DA uptake concomitant to a modification of VMAT2 pharmacological properties. It was also observed that a nuclear translocation of the sterol regulatory element-binding protein 1 (SREBP-1). The results suggested that statins induced phenotypic changes in dopaminergic cells characterized by an increase of growth, complexity of structural synaptic elements, and expression of key presynaptic proteins with functional impact on the DA transport capacity. Statin-induced changes are likely the result of a downstream modulation of SREBP-1 pathway. Overall, these mechanisms may contribute to the neuroprotective or neurorestorative effects observed in the dopaminergic system and strengthen the therapeutic potential of statins for PD.

Brivaracetam: new compound approved for the treatment of epilepsy.

Brivaracetam was approved in the E.U. and U.S. at the beginning of 2016 for the adjunctive treatment of focal epilepsies in patients over 16 years of age. This compound is a novel high-affinity synaptic vesicle glycoprotein 2A (SV2A) ligand, with a selectivity for this protein that is 10- to 30-fold higher than that shown by levetiracetam. Preclinical studies show that brivaracetam might have a stronger anticonvulsant effect and distributes in the brain more quickly, when compared to levetiracetam. The agent has linear and simple pharmacokinetics and a low interaction potential. Six double-blind placebo-controlled studies have assessed doses from 5 to 200 mg/day. Significant efficacy has been observed from doses of 50 mg/day, but there was not a clear dose-effect relationship. Short-term tolerability was excellent with all doses. Adverse events significantly associated with brivaracetam were dizziness, somnolence, fatigue and irritability. An excellent tolerability profile has been found after administration of a formulation for intravenous use.

Two Feet on the Membrane: Uptake of Clostridial Neurotoxins.

The extraordinary potency of botulinum neurotoxins (BoNT) and tetanus neurotoxin (TeNT) is mediated by their high neurospecificity, targeting peripheral cholinergic motoneurons leading to flaccid and spastic paralysis, respectively, and successive respiratory failure. Complex polysialo gangliosides accumulate BoNT and TeNT on the plasma membrane. The ganglioside binding in BoNT/A, B, E, F, G, and TeNT occurs via a conserved ganglioside-binding pocket within the most carboxyl-terminal 25kDa domain HCC, whereas BoNT/C, DC, and D display here two different ganglioside binding sites. This enrichment step facilitates subsequent binding of BoNT/A, B, DC, D, E, F, and G to the intraluminal domains of the synaptic vesicle glycoprotein 2 (SV2) isoforms A-C and synaptotagmin-I/-II, respectively. Whereas an induced α-helical 20-mer Syt peptide binds via side chain interactions to the tip of the HCC domain of BoNT/B, DC and G, the preexisting, quadrilateral β-sheet helix of SV2C-LD4 binds the clinically most relevant serotype BoNT/A mainly through backbone-backbone interactions at the interface of HCC and HCN. In addition, the conserved, complex N559-glycan branch of SV2C establishes extensive interactions with BoNT/A resulting in delayed dissociation providing BoNT/A more time for endocytosis into synaptic vesicles. An analogous interaction occurs between SV2A/B and BoNT/E. Altogether, the nature of BoNT-SV2 recognition clearly differs from BoNT-Syt. Subsequently, the synaptic vesicle is recycled and the bound neurotoxin is endocytosed. Acidification of the vesicle lumen triggers membrane insertion of the translocation domain, pore formation, and finally translocation of the enzymatically active light chain into the neuronal cytosol to halt release of neurotransmitters.