Expression and pharmacology of endogenous Cav channels in SH-SY5Y human neuroblastoma cells

Novel Scorpion Toxin ω-Buthitoxin-Hf1a Selectively Inhibits Calcium Influx via CaV3.3 and CaV3.2 and Alleviates Allodynia in a Mouse Model of Acute Postsurgical Pain

Venom peptides have evolved to target a wide range of membrane proteins through diverse mechanisms of action and structures, providing promising therapeutic leads for diseases, including pain, epilepsy, and cancer, as well as unique probes of ion channel structure-function. In this work, a high-throughput FLIPR window current screening assay on T-type CaV3.2 guided the isolation of a novel peptide named ω-Buthitoxin-Hf1a from scorpion Hottentotta franzwerneri crude venom. At only 10 amino acid residues with one disulfide bond, it is not only the smallest venom peptide known to target T-type CaVs but also the smallest structured scorpion venom peptide yet discovered. Synthetic Hf1a peptides were prepared with C-terminal amidation (Hf1a-NH2) or a free C-terminus (Hf1a-OH). Electrophysiological characterization revealed Hf1a-NH2 to be a concentration-dependent partial inhibitor of CaV3.2 (IC50 = 1.18 μM) and CaV3.3 (IC50 = 0.49 μM) depolarized currents but was ineffective at CaV3.1. Hf1a-OH did not show activity against any of the three T-type subtypes. Additionally, neither form showed activity against N-type CaV2.2 or L-type calcium channels. The three-dimensional structure of Hf1a-NH2 was determined using NMR spectroscopy and used in docking studies to predict its binding site at CaV3.2 and CaV3.3. As both CaV3.2 and CaV3.3 have been implicated in peripheral pain signaling, the analgesic potential of Hf1a-NH2 was explored in vivo in a mouse model of incision-induced acute post-surgical pain. Consistent with this role, Hf1a-NH2 produced antiallodynia in both mechanical and thermal pain.

Microelectrode Arrays Measure Blocking of Voltage-Gated Calcium Ion Channels on Supported Lipid Bilayers Derived from Primary Neurons

Drug studies targeting neuronal ion channels are crucial to understand neuronal function and develop therapies for neurological diseases. The traditional method to study neuronal ion-channel activities heavily relies on the whole-cell patch clamp as the industry standard. However, this technique is both technically challenging and labour-intensive, while involving the complexity of keeping cells alive with low throughput. Therefore, the shortcomings are limiting the efficiency of ion-channel-related neuroscience research and drug testing. Here, this work reports a new system of integrating neuron membranes with organic microelectrode arrays (OMEAs) for ion-channel-related drug studies. This work demonstrates that the supported lipid bilayers (SLBs) derived from both neuron-like (neuroblastoma) cells and primary neurons are integrated with OMEAs for the first time. The increased expression of voltage-gated calcium (CaV) ion channels on differentiated SH-SY5Y SLBs  compared to non-differentiated ones is sensed electrically. Also, dose-response of the CaV ion-channel blocking effect on primary cortical neuronal SLBs from rats is monitored. The dose range causing ion channel blocking is comparable to literature. This system overcomes the major challenges from traditional methods (e.g., patch clamp) and showcases an easy-to-test, rapid, ultra-sensitive, cell-free, and high-throughput platform to monitor dose-dependent ion-channel blocking effects on native neuronal membranes.

Cav 1.3-selective inhibitors of voltage-gated L-type Ca2+ channels: Fact or (still) fiction?

Voltage-gated L-type Ca2+ -channels (LTCCs) are the target of Ca2+ -channel blockers (CCBs), which are in clinical use for the evidence-based treatment of hypertension and angina. Their cardiovascular effects are largely mediated by the Cav 1.2-subtype. However, based on our current understanding of their physiological and pathophysiological roles, Cav 1.3 LTCCs also appear as attractive drug targets for the therapy of various diseases, including treatment-resistant hypertension, spasticity after spinal cord injury and neuroprotection in Parkinson's disease. Since CCBs inhibit both Cav 1.2 and Cav 1.3, Cav 1.3-selective inhibitors would be valuable tools to validate the therapeutic potential of Cav 1.3 channel inhibition in preclinical models. Despite a number of publications reporting the discovery of Cav 1.3-selective blockers, their selectivity remains controversial. We conclude that at present no pharmacological tools exist that are suitable to confirm or refute a role of Cav 1.3 channels in cellular responses. We also suggest essential criteria for a small molecule to be considered Cav 1.3-selective.

A bivalent remipede toxin promotes calcium release via ryanodine receptor activation

Multivalent ligands of ion channels have proven to be both very rare and highly valuable in yielding unique insights into channel structure and pharmacology. Here, we describe a bivalent peptide from the venom of Xibalbanus tulumensis, a troglobitic arthropod from the enigmatic class Remipedia, that causes persistent calcium release by activation of ion channels involved in muscle contraction. The high-resolution solution structure of φ-Xibalbin3-Xt3a reveals a tandem repeat arrangement of inhibitor-cysteine knot (ICK) domains previously only found in spider venoms. The individual repeats of Xt3a share sequence similarity with a family of scorpion toxins that target ryanodine receptors (RyR). Single-channel electrophysiology and quantification of released Ca²⁺ stores within skinned muscle fibers confirm Xt3a as a bivalent RyR modulator. Our results reveal convergent evolution of RyR targeting toxins in remipede and scorpion venoms, while the tandem-ICK repeat architecture is an evolutionary innovation that is convergent with toxins from spider venoms.

Targeting neuronal calcium channels and GSK3β for Alzheimer's disease with naturally-inspired Diels-Alder adducts

The complexity of neurodegenerative diseases, among which Alzheimer's disease plays a pivotal role, poses one of the tough therapeutic challenges of present time. In this perspective, a multitarget approach appears as a promising strategy to simultaneously interfere with different defective pathways. In this paper, a structural simplification plan was performed on our previously reported multipotent polycyclic compounds, in order to obtain a simpler pharmacophoric central core with improved pharmacokinetic properties, while maintaining the modulating activity on neuronal calcium channels and glycogen synthase kinase 3-beta (GSK-3β), as validated targets to combat Alzheimer's disease. The molecular pruning approach applied here led to tetrahydroisoindole-dione (1), tetrahydromethanoisoindole-dione (2) and tetrahydroepoxyisoindole-dione (3) structures, easily affordable by Diels-Alder cycloaddition. Preliminary data indicated structure 3 as the most appropriate, thus a SAR study was performed by introducing different substituents, selected on the basis of the commercial availability of the furan derivatives required for the synthetic procedure. The results indicated compound 10 as a promising, structurally atypical, safe and BBB-penetrating Ca_v modulator, inhibiting both L- and N-calcium channels, likely responsible for the Ca²⁺ overload observed in Alzheimer's disease. In a multitarget perspective, compound 11 appeared as an effective prototype, endowed with improved Ca_v inhibitory activity, with respect to the reference drug nifedipine, and encouraging modulating activity on GSK-3β.

Diindolylmethane Derivatives: New Selective Blockers for T-Type Calcium Channels

The natural product indole-3-carbinol (I3C) and its major digestive product 3,3′-diindolylmethane (DIM) have shown clinical promise in multiple forms of cancer including breast cancer. In this study, we explored the calcium channel activity of DIM, its synthetic derivative 3,3′-Diindolylmethanone (DIM-one) and related I3C and DIM-one analogs. For the first time, DIM, DIM-one and analog IX were identified as selective blockers for T-type Ca_V3.3 (IC₅₀s DIM 2.09 µM; DIM-one 9.07 µM) while compound IX inhibited both Ca_V3.2 (6.68 µM) and Ca_V3.3 (IC₅₀ = 3.05 µM) using a FLIPR cell-based assay to measure inhibition of T-type calcium channel window current. Further characterization of DIM by electrophysiology revealed it inhibited inward Ca²⁺ current through Ca_V3.1 (IC₅₀ = 8.32 µM) and Ca_V3.3 (IC₅₀ = 9.63 µM), while IX partially blocked Ca_V3.2 and Ca_V3.3 inward Ca²⁺ current. In contrast, DIM-one preferentially blocked Ca_V3.1 inward Ca²⁺ current (IC₅₀ = 1.53 µM). The anti-proliferative activities of these compounds revealed that oxidation of the methylene group of DIM shifted the selectivity of DIMs from breast cancer cell line MCF-7 to colon cancer cell line HT-29.

Inhibition of N-type calcium ion channels by tricyclic antidepressants - experimental and theoretical justification for their use for neuropathic pain

A number of tricyclic antidepressants (TCAs) are commonly prescribed off-label for the treatment of neuropathic pain. The blockade of neuronal calcium ion channels is often invoked to partially explain the analgesic activity of TCAs, but there has been very limited experimental or theoretical evidence reported to support this assertion. The N-type calcium ion channel (CaV2.2) is a well-established target for the treatment of neuropathic pain and in this study a series of eleven TCAs and two closely related drugs were shown to be moderately effective inhibitors of this channel when endogenously expressed in the SH-SY5Y neuroblastoma cell line. A homology model of the channel, which matches closely a recently reported Cryo-EM structure, was used to investigate via docking and molecular dynamics experiments the possible mode of inhibition of CaV2.2 channels by TCAs. Two closely related binding modes, that occur in the channel cavity that exists between the selectivity filter and the internal gate, were identified. The TCAs are predicted to position themselves such that their ammonium side chains interfere with the selectivity filter, with some, such as amitriptyline, also appearing to hinder the channel's ability to open. This study provides the most comprehensive evidence to date that supports the notion that the blockade of neuronal calcium ion channels by TCAs is at least partially responsible for their analgesic effect.

Modulation of Gq/PLC-Mediated Signaling by Acute Lithium Exposure

Although lithium has long been one of the most widely used pharmacological agents in psychiatry, its mechanisms of action at the cellular and molecular levels remain poorly understood. One of the targets of Li+ is the phosphoinositide pathway, but whereas the impact of Li+ on inositol lipid metabolism is well documented, information on physiological effects at the cellular level is lacking. We examined in two mammalian cell lines the effect of acute Li+ exposure on the mobilization of internal Ca2+ and phospholipase C (PLC)-dependent membrane conductances. We first corroborated by Western blots and immunofluorescence in HEK293 cells the presence of key signaling elements of a muscarinic PLC pathway (M1AchR, Gq, PLC-β1, and IP3Rs). Stimulation with carbachol evoked a dose-dependent mobilization of Ca, as determined with fluorescent indicators. This was due to release from internal stores and proved susceptible to the PLC antagonist U73122. Li+ exposure reproducibly potentiated the Ca response in a concentration-dependent manner extending to the low millimolar range. To broaden those observations to a neuronal context and probe potential Li modulation of electrical signaling, we next examined the cell line SHsy5y. We replicated the potentiating effects of Li on the mobilization of internal Ca, and, after characterizing the basic properties of the electrical response to cholinergic stimulation, we also demonstrated an equally robust upregulation of muscarinic membrane currents. Finally, by directly stimulating the signaling pathway at different links downstream of the receptor, the site of action of the observed Li effects could be narrowed down to the G protein and its interaction with PLC-β. These observations document a modulation of Gq/PLC/IP3-mediated signaling by acute exposure to lithium, reflected in distinct physiological changes in cellular responses.

A Deep Learning Approach with Data Augmentation to Predict Novel Spider Neurotoxic Peptides

As major components of spider venoms, neurotoxic peptides exhibit structural diversity, target specificity, and have great pharmaceutical potential. Deep learning may be an alternative to the laborious and time-consuming methods for identifying these peptides. However, the major hurdle in developing a deep learning model is the limited data on neurotoxic peptides. Here, we present a peptide data augmentation method that improves the recognition of neurotoxic peptides via a convolutional neural network model. The neurotoxic peptides were augmented with the known neurotoxic peptides from UniProt database, and the models were trained using a training set with or without the generated sequences to verify the augmented data. The model trained with the augmented dataset outperformed the one with the unaugmented dataset, achieving accuracy of 0.9953, precision of 0.9922, recall of 0.9984, and F1 score of 0.9953 in simulation dataset. From the set of all RNA transcripts of Callobius koreanus spider, we discovered neurotoxic peptides via the model, resulting in 275 putative peptides of which 252 novel sequences and only 23 sequences showing homology with the known peptides by Basic Local Alignment Search Tool. Among these 275 peptides, four were selected and shown to have neuromodulatory effects on the human neuroblastoma cell line SH-SY5Y. The augmentation method presented here may be applied to the identification of other functional peptides from biological resources with insufficient data.

Ladostigil Attenuates Induced Oxidative Stress in Human Neuroblast-like SH-SY5Y Cells

A hallmark of the aging brain is the robust inflammation mediated by microglial activation. Pathophysiology of common neurodegenerative diseases involves oxidative stress and neuroinflammation. Chronic treatment of aging rats by ladostigil, a compound with antioxidant and anti-inflammatory function, prevented microglial activation and learning deficits. In this study, we further investigate the effect of ladostigil on undifferentiated SH-SY5Y cells. We show that SH-SY5Y cells exposed to acute (by H₂O₂) or chronic oxidative stress (by Sin1, 3-morpholinosydnonimine) induced apoptotic cell death. However, in the presence of ladostigil, the decline in cell viability and the increase of oxidative levels were partially reversed. RNA-seq analysis showed that prolonged oxidation by Sin1 resulted in a simultaneous reduction of the expression level of endoplasmic reticulum (ER) genes that participate in proteostasis. By comparing the differential gene expression profile of Sin1 treated cells to cells incubated with ladostigil before being exposed to Sin1, we observed an over-expression of Clk1 (Cdc2-like kinase 1) which was implicated in psychophysiological stress in mice and Alzheimer’s disease. Ladostigil also suppressed the expression of Ccpg1 (Cell cycle progression 1) and Synj1 (Synaptojanin 1) that are involved in ER-autophagy and endocytic pathways. We postulate that ladostigil alleviated cell damage induced by oxidation. Therefore, under conditions of chronic stress that are observed in the aging brain, ladostigil may block oxidative stress processes and consequently reduce neurotoxicity.

Cell-Based Reporter Release Assay to Determine the Activity of Calcium-Dependent Neurotoxins and Neuroactive Pharmaceuticals

The suitability of a newly developed cell-based functional assay was tested for the detection of the activity of a range of neurotoxins and neuroactive pharmaceuticals which act by stimulation or inhibition of calcium-dependent neurotransmitter release. In this functional assay, a reporter enzyme is released concomitantly with the neurotransmitter from neurosecretory vesicles. The current study showed that the release of a luciferase from a differentiated human neuroblastoma-based reporter cell line (SIMA-hPOMC1-26-GLuc cells) can be stimulated by a carbachol-mediated activation of the Gq-coupled muscarinic-acetylcholine receptor and by the Ca²⁺-channel forming spider toxin α-latrotoxin. Carbachol-stimulated luciferase release was completely inhibited by the muscarinic acetylcholine receptor antagonist atropine and α-latrotoxin-mediated release by the Ca²⁺-chelator EGTA, demonstrating the specificity of luciferase-release stimulation. SIMA-hPOMC1-26-GLuc cells express mainly L- and N-type and to a lesser extent T-type VGCC on the mRNA and protein level. In accordance with the expression profile a depolarization-stimulated luciferase release by a high K⁺-buffer was effectively and dose-dependently inhibited by L-type VGCC inhibitors and to a lesser extent by N-type and T-type inhibitors. P/Q- and R-type inhibitors did not affect the K⁺-stimulated luciferase release. In summary, the newly established cell-based assay may represent a versatile tool to analyze the biological efficiency of a range of neurotoxins and neuroactive pharmaceuticals which mediate their activity by the modulation of calcium-dependent neurotransmitter release.

A short isoform of STIM1 confers frequency-dependent synaptic enhancement

Store-operated Ca2+-entry (SOCE) regulates basal and receptor-triggered Ca2+ signaling with STIM proteins sensing the endoplasmic reticulum (ER) Ca2+ content and triggering Ca2+ entry by gating Orai channels. Although crucial for immune cells, STIM1's role in neuronal Ca2+ homeostasis is controversial. Here, we characterize a splice variant, STIM1B, which shows exclusive neuronal expression and protein content surpassing conventional STIM1 in cerebellum and of significant abundance in other brain regions. STIM1B expression results in a truncated protein with slower kinetics of ER-plasma membrane (PM) cluster formation and ICRAC, as well as reduced inactivation. In primary wild-type neurons, STIM1B is targeted by its spliced-in domain B to presynaptic sites where it converts classic synaptic depression into Ca2+- and Orai-dependent short-term synaptic enhancement (STE) at high-frequency stimulation (HFS). In conjunction with altered STIM1 splicing in human Alzheimer disease, our findings highlight STIM1 splicing as an important regulator of neuronal calcium homeostasis and of synaptic plasticity.

A novel transgenic zebrafish line allows for in vivo quantification of autophagic activity in neurons

The pathophysiology of most neurodegenerative diseases includes aberrant accumulation of protein aggregates. Recent evidence highlights the role of protein degradation pathways in neurodegeneration. Concurrently, genetic tools have been generated to enable zebrafish, Danio rerio, to be used as an animal model to study neurodegenerative processes. In addition to optical clarity and fast ex utero development, the zebrafish brain is relatively small and has conserved structures with its mammalian counterparts. To take advantage of this model organism and to aid further studies on autophagy and neurodegeneration, we created a stable transgenic zebrafish line that expresses eGFP-Map1lc3b specifically in post-mitotic neurons under the elavl3 promoter. This line is useful for indirectly monitoring autophagic activity in neurons in vivo and screening for macroautophagy/autophagy-modulating compounds. We determined the applicability of this transgenic line by modulating and quantifying the number of autophagosomes via treatment with a known autophagy inducer (rapamycin) and inhibitors (3-methyladenine, protease inhibitors). Additionally, we proposed an in vivo method for quantifying rates of autophagosome accumulation, which can be used to infer occurrence of autophagic flux. Last, we tested two FDA-approved drugs currently undergoing clinical studies for Parkinson disease, isradipine and nilotinib, and found that isradipine did not modulate autophagy, whereas nilotinib induced both autophagosome number and autophagic flux. It is hoped that others will find this line useful as an in vivo vertebrate model to find or validate autophagy modulators that might be used to halt the progression of neurodegenerative diseases. Abbreviations: 3MA: 3-methyladenine; BafA: bafilomycin A1; dd: dorsal diencephalon; dpf: days post fertilization; e: eye; eGFP: enhanced green fluorescent protein; Elavl3: ELAV like neuron-specific RNA binding protein 3; FDA: Food and Drug Administration; hb: habenula; hpt, hours post treatment; Map1lc3b: microtubule-associated protein 1 light chain 3 beta; nt: neural tube; ot, optic tectum; P/E: pepstatin A and E64d; PD: Parkinson disease; PMTs: photomultiplier tubes; PTU: 1-phenyl-2-thiourea; Ta: annealing temperature; Tel, telencephalon.

Novel conorfamides from Conus austini venom modulate both nicotinic acetylcholine receptors and acid-sensing ion channels

Conorfamides are a poorly studied family of cone snail venom peptides with broad biological activities, including inhibition of glutamate receptors, acid-sensing ion channels, and voltage-gated potassium channels. The aim of this study was to characterize the pharmacological activity of two novel linear conorfamides (conorfamide_As1a and conorfamide_As2a) and their non-amidated counterparts (conopeptide_As1b and conopeptide_As2b) that were isolated from the venom of the Mexican cone snail Conus austini. Although As1a, As2a, As1b and As2b were identified by activity-guided fractionation using a high-throughput fluorescence imaging plate reader (FLIPR) assay assessing α7 nAChR activity, sequence determination revealed activity associated with four linear peptides of the conorfamide rather than the anticipated α-conotoxin family. Pharmacological testing revealed that the amidated peptide variants altered desensitization of acid-sensing ion channels (ASICs) 1a and 3, and the native lysine to arginine mutation differentiating As1a and As1b from As2a and As2b introduced ASIC1a peak current potentiation. Surprisingly, these conorfamides also inhibited α7 and muscle-type nicotinic acetylcholine receptors (nAChR) at nanomolar concentrations. This is the first report of conorfamides with dual activity, with the nAChR activity being the most potent molecular target of any conorfamide discovered to date.

'Messy' Processing of χ-conotoxin MrIA Generates Homologues with Reduced hNET Potency

Integrated venomics techniques have shown that variable processing of conotoxins from Conus marmoreus resulted in a dramatic expansion in the number of expressed conotoxins. One conotoxin from C. marmoreus, the χ-conotoxin MrIA, is a selective inhibitor of human norepinephrine transporters (hNET) and therefore a drug candidate for attenuating chronic neuropathic pain. It has been found that “messy” processing of the MrIA transcripts results in the expression of MrIA analogs with different truncations of the pro-peptide that contains portions of the MrIA molecule. The aim of this study was to investigate if variable processing of the expressed peptides results in modulation of the existing hNET pharmacology or creates new pharmacologies. To this end, a number of MrIA analogs found in C. marmoreus venom were synthesized and evaluated for their activity at hNET receptors. While several of the analogs exhibited norepinephrine transporter inhibitory activity comparable to that of MrIA, none significantly improved on the potency of conotoxin MrIA, and those analogs with disrupted pharmacophores produced greatly reduced NET inhibition, confirming previous structure-activity relationships seen on χ-class conopeptides. Additionally, analogs were screened for new activities on ion channels using calcium influx assays, although no major new pharmacology was revealed.

Synthesis of Pseudellone Analogs and Characterization as Novel T-type Calcium Channel Blockers

T-type calcium channel (Ca_V3.x) blockers are receiving increasing attention as potential therapeutics for the treatment of pathophysiological disorders and diseases, including absence epilepsy, Parkinson's disease (PD), hypertension, cardiovascular diseases, cancers, and pain. However, few clinically approved Ca_V3.x blockers are available, and selective pharmacological tools are needed to further unravel the roles of individual Ca_V3.x subtypes. In this work, through an efficient synthetic route to the marine fungal product pseudellone C, we obtained bisindole alkaloid analogs of pseudellone C with a modified tryptophan moiety and identified two Ca_V3.2 (2, IC₅₀ = 18.24 µM; 3, IC₅₀ = 6.59 µM) and Ca_V3.3 (2, IC₅₀ = 7.71 µM; 3, IC₅₀ = 3.81 µM) selective blockers using a FLIPR cell-based assay measuring Ca_V3.x window currents. Further characterization by whole-cell patch-clamp revealed a preferential block of Ca_V3.1 activated current (2, IC₅₀ = 5.60 µM; 3, IC₅₀ = 9.91 µM), suggesting their state-dependent block is subtype specific.

Novel analgesic ω-conotoxins from the vermivorous cone snail Conus moncuri provide new insights into the evolution of conopeptides

Cone snails are a diverse group of predatory marine invertebrates that deploy remarkably complex venoms to rapidly paralyse worm, mollusc or fish prey. ω-Conotoxins are neurotoxic peptides from cone snail venoms that inhibit Ca_v2.2 voltage-gated calcium channel, demonstrating potential for pain management via intrathecal (IT) administration. Here, we isolated and characterized two novel ω-conotoxins, MoVIA and MoVIB from Conus moncuri, the first to be identified in vermivorous (worm-hunting) cone snails. MoVIA and MoVIB potently inhibited human Ca_v2.2 in fluorimetric assays and rat Ca_v2.2 in patch clamp studies, and both potently displaced radiolabeled ω-conotoxin GVIA (¹²⁵I-GVIA) from human SH-SY5Y cells and fish brain membranes (IC₅₀ 2–9 pM). Intriguingly, an arginine at position 13 in MoVIA and MoVIB replaced the functionally critical tyrosine found in piscivorous ω-conotoxins. To investigate its role, we synthesized MoVIB-[R13Y] and MVIIA-[Y13R]. Interestingly, MVIIA-[Y13R] completely lost Ca_v2.2 activity and MoVIB-[R13Y] had reduced activity, indicating that Arg at position 13 was preferred in these vermivorous ω-conotoxins whereas tyrosine 13 is preferred in piscivorous ω-conotoxins. MoVIB reversed pain behavior in a rat neuropathic pain model, confirming that vermivorous cone snails are a new source of analgesic ω-conotoxins. Given vermivorous cone snails are ancestral to piscivorous species, our findings support the repurposing of defensive venom peptides in the evolution of piscivorous Conidae.

STIM1 deficiency is linked to Alzheimer's disease and triggers cell death in SH-SY5Y cells by upregulation of L-type voltage-operated Ca2+ entry

Abstract

STIM1 is an endoplasmic reticulum protein with a role in Ca²⁺ mobilization and signaling. As a sensor of intraluminal Ca²⁺ levels, STIM1 modulates plasma membrane Ca²⁺ channels to regulate Ca²⁺ entry. In neuroblastoma SH-SY5Y cells and in familial Alzheimer’s disease patient skin fibroblasts, STIM1 is cleaved at the transmembrane domain by the presenilin-1-associated γ-secretase, leading to dysregulation of Ca²⁺ homeostasis. In this report, we investigated expression levels of STIM1 in brain tissues (medium frontal gyrus) of pathologically confirmed Alzheimer’s disease patients, and observed that STIM1 protein expression level decreased with the progression of neurodegeneration. To study the role of STIM1 in neurodegeneration, a strategy was designed to knock-out the expression of STIM1 gene in the SH-SY5Y neuroblastoma cell line by CRISPR/Cas9-mediated genome editing, as an in vitro model to examine the phenotype of STIM1-deficient neuronal cells. It was proved that, while STIM1 is not required for the differentiation of SH-SY5Y cells, it is absolutely essential for cell survival in differentiating cells. Differentiated STIM1-KO cells showed a significant decrease of mitochondrial respiratory chain complex I activity, mitochondrial inner membrane depolarization, reduced mitochondrial free Ca²⁺ concentration, and higher levels of senescence as compared with wild-type cells. In parallel, STIM1-KO cells showed a potentiated Ca²⁺ entry in response to depolarization, which was sensitive to nifedipine, pointing to L-type voltage-operated Ca²⁺ channels as mediators of the upregulated Ca²⁺ entry. The stable knocking-down of CACNA1C transcripts restored mitochondrial function, increased mitochondrial Ca²⁺ levels, and dropped senescence to basal levels, demonstrating the essential role of the upregulation of voltage-operated Ca²⁺ entry through Ca_v1.2 channels in STIM1-deficient SH-SY5Y cell death.

Key messages

STIM1 protein expression decreases with the progression of neurodegeneration in Alzheimer’s disease.

STIM1 is essential for cell viability in differentiated SH-SY5Y cells.

STIM1 deficiency triggers voltage-regulated Ca²⁺ entry-dependent cell death.

Mitochondrial dysfunction and senescence are features of STIM1-deficient differentiated cells.

Electronic supplementary material

The online version of this article (10.1007/s00109-018-1677-y) contains supplementary material, which is available to authorized users.

A novel variant in TAF1 affects gene expression and is associated with X-linked TAF1 intellectual disability syndrome

We investigated the genome of a 5-year-old male who presented with global developmental delay (motor, cognitive, and speech), hypotonia, possibly ataxia, and cerebellar hypoplasia of unknown origin. Whole genome sequencing (WGS) and mRNA sequencing (RNA-seq) were performed on a family having an affected proband, his unaffected parents, and maternal grandfather. To explore the molecular and functional consequences of the variant, we performed cell proliferation assays, quantitative real-time PCR (qRT-PCR) array, immunoblotting, calcium imaging, and neurite outgrowth experiments in SH-SY5Y neuroblastoma cells to compare the properties of the wild-type TATA-box-binding protein factor 1 (TAF1), deletion of TAF1, and TAF1 variant p.Ser1600Gly samples. The whole genome data identified several gene variants. However, the genome sequence data failed to implicate a candidate gene as many of the variants were of unknown significance. By combining genome sequence data with transcriptomic data, a probable candidate variant, p.Ser1600Gly, emerged in TAF1. Moreover, the RNA-seq data revealed a 90:10 extremely skewed X-chromosome inactivation (XCI) in the mother. Our results showed that neuronal ion channel genes were differentially expressed between TAF1 deletion and TAF1 variant p.Ser1600Gly cells, when compared with their respective controls, and that the TAF1 variant may impair neuronal differentiation and cell proliferation. Taken together, our data suggest that this novel variant in TAF1 plays a key role in the development of a recently described X-linked syndrome, TAF1 intellectual disability syndrome, and further extends our knowledge of a potential link between TAF1 deficiency and defects in neuronal cell function.

Recent advances in the development of T-type calcium channel blockers for pain intervention

Cav 3.2 T-type calcium channels are important regulators of pain signals in the afferent pain pathway, and their activities are dysregulated during various chronic pain states. Therefore, it is reasonable to predict that inhibiting T-type calcium channels in dorsal root ganglion neurons and in the spinal dorsal horn can be targeted for pain relief. This is supported by early pharmacological studies with T-type channel blockers, such as ethosuximide, and by analgesic effects of siRNA depletion of Cav 3.2 channels. In the past 5 years, considerable effort has been applied towards identifying novel classes of T-type calcium channel blockers. Here, we review recent developments in the discovery of novel classes of T-type calcium channel blockers, and their analgesic effects in animal models of pain and in clinical trials.

LINKED ARTICLES

This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

An SAR study of hydroxy-trifluoromethylpyrazolines as inhibitors of Orai1-mediated store operated Ca2+ entry in MDA-MB-231 breast cancer cells using a convenient Fluorescence Imaging Plate Reader assay

The proteins Orai1 and STIM1 control store-operated Ca²⁺ entry (SOCE) into cells. SOCE is important for migration, invasion and metastasis of MDA-MB-231 human triple negative breast cancer (TNBC) cells and has been proposed as a target for cancer drug discovery. Two hit compounds from a medium throughput screen, displayed encouraging inhibition of SOCE in MDA-MB-231 cells, as measured by a Fluorescence Imaging Plate Reader (FLIPR) Ca²⁺ assay. Following NMR spectroscopic analysis of these hits and reassignment of their structures as 5-hydroxy-5-trifluoromethylpyrazolines, a series of analogues was prepared via thermal condensation reactions between substituted acylhydrazones and trifluoromethyl 1,3-dicarbonyl arenes. Structure-activity relationship (SAR) studies showed that small lipophilic substituents at the 2- and 3-positions of the RHS and 2-, 3- and 4-postions of the LHS terminal benzene rings improved activity, resulting in a novel class of potent and selective inhibitors of SOCE.

New insights on Parkinson's disease from differentiation of SH-SY5Y into dopaminergic neurons: An involvement of aquaporin4 and 9

The purpose of this research was to explore the behavior of aquaporins (AQPs) in an in vitro model of Parkinson's disease that is a recurrent neurodegenerative disorder caused by the gradual, progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Because of postmortem studies have provided evidences for oxidative damage and alteration of water flow and energy metabolism, we carried out an investigation about AQP4 and 9, demonstrated in the brain to maintain water and energy homeostasis. As an appropriate in vitro cell model, we used SH-SY5Y cultures and induced their differentiation into a mature dopaminergic neuron phenotype with retinoic acid (RA) alone or in association with phorbol-12-myristate-13-acetate (MPA). The association RA plus MPA provided the most complete and mature neuron phenotype, as demonstrated by high levels of β-Tubulin III, MAP-2, and tyrosine hydroxylase. After validation of cell differentiation, the neurotoxin 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) and H₂O₂ were applied to reproduce a Parkinson's-like stress. The results confirmed RA/MPA differentiated SH-SY5Y as a useful in vitro system for studying neurotoxicity and for using in a MPTP and H₂O₂-induced Parkinson's disease cell model. Moreover, the data demonstrated that neuronal differentiation, neurotoxicity, neuroinflammation, and oxidative stress are strongly correlated with dynamic changes of AQP4 and 9 transcription and transduction. New in vitro and in vivo experiments are needed to confirm these innovative outcomes.

Crotalphine desensitizes TRPA1 ion channels to alleviate inflammatory hyperalgesia

Crotalphine is a structural analogue to a novel analgesic peptide that was first identified in the crude venom from the South American rattlesnake Crotalus durissus terrificus. Although crotalphine's analgesic effect is well established, its direct mechanism of action remains unresolved. The aim of the present study was to investigate the effect of crotalphine on ion channels in peripheral pain pathways. We found that picomolar concentrations of crotalphine selectively activate heterologously expressed and native TRPA1 ion channels. TRPA1 activation by crotalphine required intact N-terminal cysteine residues and was followed by strong and long-lasting desensitization of the channel. Homologous desensitization of recombinant TRPA1 and heterologous desensitization in cultured dorsal root ganglia neurons was observed. Likewise, crotalphine acted on peptidergic TRPA1-expressing nerve endings ex vivo as demonstrated by suppression of calcitonin gene-related peptide release from the trachea and in vivo by inhibition of chemically induced and inflammatory hypersensitivity in mice. The crotalphine-mediated desensitizing effect was abolished by the TRPA1 blocker HC030031 and absent in TRPA1-deficient mice. Taken together, these results suggest that crotalphine is the first peptide to mediate antinociception selectively and at subnanomolar concentrations by targeting TRPA1 ion channels.

Redesigned Spider Peptide with Improved Antimicrobial and Anticancer Properties

Gomesin, a disulfide-rich antimicrobial peptide produced by the Brazilian spider Acanthoscurria gomesiana, has been shown to be potent against Gram-negative bacteria and to possess selective anticancer properties against melanoma cells. In a recent study, a backbone cyclized analogue of gomesin was shown to be as active but more stable than its native form. In the current study, we were interested in improving the antimicrobial properties of the cyclic gomesin, understanding its selectivity toward melanoma cells and elucidating its antimicrobial and anticancer mode of action. Rationally designed analogues of cyclic gomesin were examined for their antimicrobial potency, selectivity toward cancer cells, membrane-binding affinity, and ability to disrupt cell and model membranes. We improved the activity of cyclic gomesin by ∼10-fold against tested Gram-negative and Gram-positive bacteria without increasing toxicity to human red blood cells. In addition, we showed that gomesin and its analogues are more toxic toward melanoma and leukemia cells than toward red blood cells and act by selectively targeting and disrupting cancer cell membranes. Preference toward some cancer types is likely dependent on their different cell membrane properties. Our findings highlight the potential of peptides as antimicrobial and anticancer leads and the importance of selectively targeting cancer cell membranes for drug development.

Discovery and mode of action of a novel analgesic β-toxin from the African spider Ceratogyrus darlingi

Spider venoms are rich sources of peptidic ion channel modulators with important therapeutical potential. We screened a panel of 60 spider venoms to find modulators of ion channels involved in pain transmission. We isolated, synthesized and pharmacologically characterized Cd1a, a novel peptide from the venom of the spider Ceratogyrus darlingi. Cd1a reversibly paralysed sheep blowflies (PD₅₀ of 1318 pmol/g) and inhibited human Ca_v2.2 (IC₅₀ 2.6 μM) but not Ca_v1.3 or Ca_v3.1 (IC₅₀ > 30 μM) in fluorimetric assays. In patch-clamp electrophysiological assays Cd1a inhibited rat Ca_v2.2 with similar potency (IC₅₀ 3 μM) without influencing the voltage dependence of Ca_v2.2 activation gating, suggesting that Cd1a doesn’t act on Ca_v2.2 as a classical gating modifier toxin. The Cd1a binding site on Ca_v2.2 did not overlap with that of the pore blocker ω-conotoxin GVIA, but its activity at Ca_v2.2-mutant indicated that Cd1a shares some molecular determinants with GVIA and MVIIA, localized near the pore region. Cd1a also inhibited human Na_v1.1–1.2 and Na_v1.7–1.8 (IC₅₀ 0.1–6.9 μM) but not Na_v1.3–1.6 (IC₅₀ > 30 μM) in fluorimetric assays. In patch-clamp assays, Cd1a strongly inhibited human Na_v1.7 (IC₅₀ 16 nM) and produced a 29 mV depolarising shift in Na_v1.7 voltage dependence of activation. Cd1a (400 pmol) fully reversed Na_v1.7-evoked pain behaviours in mice without producing side effects. In conclusion, Cd1a inhibited two anti-nociceptive targets, appearing to interfere with Ca_v2.2 inactivation gating, associated with the Ca_v2.2 α-subunit pore, while altering the activation gating of Na_v1.7. Cd1a was inactive at some of the Na_v and Ca_v channels expressed in skeletal and cardiac muscles and nodes of Ranvier, apparently contributing to the lack of side effects at efficacious doses, and suggesting potential as a lead for development of peripheral pain treatments.

L- and T-type calcium channel blockers protect against the inhibitory effects of mipafox on neurite outgrowth and plasticity-related proteins in SH-SY5Y cells

Some organophosphorus compounds (OP), including the pesticide mipafox, produce late onset distal axonal degeneration, known as organophosphorus-induced delayed neuropathy (OPIDN). The underlying mechanism involves irreversible inhibition of neuropathy target esterase (NTE) activity, elevated intracellular calcium levels, increased activity of calcium-activated proteases and impaired neuritogenesis. Voltage-gated calcium channels (VGCC) appear to play a role in several neurologic disorders, including OPIDN. Therefore, this study aimed to examine and compare the neuroprotective effects of T-type (amiloride) and L-type (nimodipine) VGCC blockers induced by the inhibitory actions of mipafox on neurite outgrowth and axonal proteins of retinoic-acid-stimulated SH-SY5Y human neuroblastoma cells, a neuronal model widely employed to determine the neurotoxicity attributed to OP. Both nimodipine and amiloride significantly blocked augmentation of intracellular calcium levels and activity of calpains, as well as decreased neurite length, number of differentiated cells, and lowered concentrations of growth-associated protein 43 (GAP-43) and synapsin induced by mipafox. Only nimodipine inhibited reduction of synaptophysin levels produced by mipafox. These findings demonstrate a role for calcium and VGCC in the impairment of neuronal plasticity mediated by mipafox. Data also demonstrated the neuroprotective potential of T-type and L-type VGCC blockers to inhibit OP-mediated actions, which may be beneficial to counteract cases of pesticide poisoning.

Human neuronal cell based assay: A new in vitro model for toxicity evaluation of ciguatoxin

Ciguatoxins (CTXs) are emerging marine neurotoxins representing the main cause of ciguatera fish poisoning, an intoxication syndrome which configures a health emergency and constitutes an evolving issue constantly changing due to new vectors and derivatives of CTXs, as well as their presence in new non-endemic areas. The study applied the neuroblastoma cell model of human origin (SH-SY5Y) to evaluate species-specific mechanistic information on CTX toxicity. Metabolic functionality, cell morphology, cytosolic Ca²⁺_i responses, neuronal cell growth and proliferation were assessed after short- (4-24h) and long-term exposure (10days) to P-CTX-3C. In SH-SY5Y, P-CTX-3C displayed a powerful cytotoxicity requiring the presence of both Veratridine and Ouabain. SH-SY5Y were very sensitive to Ouabain: 10 and 0.25nM appeared the optimal concentrations, for short- and long-term toxicity studies, respectively, to be used in co-incubation with Veratridine (25μM), simulating the physiological and pathological endogenous Ouabain levels in humans. P-CTX-3C cytotoxic effect, on human neurons co-incubated with OV (Ouabain+Veratridine) mix, was expressed starting from 100pM after short- and 25pM after long-term exposure. Notably, P-CTX-3C alone at 25nM induced cytotoxicity after 24h and prolonged exposure. This human brain-derived cell line appears a suitable cell-based-model to evaluate cytotoxicity of CTX present in marine food contaminated at low toxic levels and to characterize the toxicological profile of other/new congeners.

Paracrine Maturation and Migration of SH-SY5Y Cells by Dental Pulp Stem Cells

Neurological disorders are characterized by neurodegeneration and/or loss of neuronal function, which cannot be adequately repaired by the host. Therefore, there is need for novel treatment options such as cell-based therapies that aim to salvage or reconstitute the lost tissue or that stimulate host repair. The present study aimed to evaluate the paracrine effects of human dental pulp stem cells (hDPSCs) on the migration and neural maturation of human SH-SY5Y neuroblastoma cells. The hDPSC secretome had a significant chemoattractive effect on SH-SY5Y cells as shown by a transwell assay. To evaluate neural maturation, SH-SY5Y cells were first induced toward neuronal cells, after which they were exposed to the hDPSC secretome. In addition, SH-SY5Y cells subjected to the hDPSC secretome showed increased neuritogenesis compared with nonexposed cells. Maturated cells were shown to increase immune reactivity for neuronal markers compared with controls. Ultrastructurally, retinoic acid (RA) signaling and subsequent exposure to the hDPSC secretome induced a gradual rise in metabolic activity and neuronal features such as multivesicular bodies and cytoskeletal elements associated with cellular communication. In addition, electrophysiological recordings of differentiating cells demonstrated a transition toward a neuronal electrophysiological profile based on the maximum tetrodotoxin (TTX)–sensitive, Na+ current. Moreover, conditioned medium (CM)–hDPSC–maturated SH-SY5Y cells developed distinct features including, Cd2+-sensitive currents, which suggests that CM-hDPSC–maturated SH-SY5Y acquired voltage-gated Ca2+ channels. The results reported in this study demonstrate the potential of hDPSCs to support differentiation and recruitment of cells with neuronal precursor characteristics in a paracrine manner. Moreover, this in vitro experimental design showed that the widely used SH-SY5Y cell line can improve and simplify the preclinical in vitro research on the molecular mechanisms of stem cell–mediated neuronal regeneration.

Evaluation of known and novel inhibitors of Orai1-mediated store operated Ca2+ entry in MDA-MB-231 breast cancer cells using a Fluorescence Imaging Plate Reader assay

The Orai1 Ca²⁺ permeable ion channel is an important component of store operated Ca²⁺ entry (SOCE) in cells. It's over-expression in basal molecular subtype breast cancers has been linked with poor prognosis, making it a potential target for drug development. We pharmacologically characterised a number of reported inhibitors of SOCE in MDA-MB-231 breast cancer cells using a convenient Fluorescence Imaging Plate Reader (FLIPR) assay, and show that the rank order of their potencies in this assay is the same as those reported in a wide range of published assays. The assay was also used in a screening project seeking novel inhibitors. Following a broad literature survey of classes of calcium channel inhibitors we used simplified ligand structures to query the ZINC on-line database, and following two iterations of refinement selected a novel Orai1-selective dichlorophenyltriazole hit compound. Analogues of this were synthesized and evaluated in the FLIPR assay to develop structure-activity relationships (SAR) for the three domains of the hit; triazole (head), dichlorophenyl (body) and substituted phenyl (tail). For this series, the results suggested the need for a lipophilic tail domain and an out-of-plane twist between the body and tail domains.

Isolation and characterization of a structurally unique β-hairpin venom peptide from the predatory ant Anochetus emarginatus

BACKGROUND

Most ant venoms consist predominantly of small linear peptides, although some contain disulfide-linked peptides as minor components. However, in striking contrast to other ant species, some Anochetus venoms are composed primarily of disulfide-rich peptides. In this study, we investigated the venom of the ant Anochetus emarginatus with the aim of exploring these novel disulfide-rich peptides.

METHODS

The venom peptidome was initially investigated using a combination of reversed-phase HPLC and mass spectrometry, then the amino acid sequences of the major peptides were determined using a combination of Edman degradation and de novo MS/MS sequencing. We focused on one of these peptides, U1-PONTX-Ae1a (Ae1a), because of its novel sequence, which we predicted would form a novel 3D fold. Ae1a was chemically synthesized using Fmoc chemistry and its 3D structure was elucidated using NMR spectroscopy. The peptide was then tested for insecticidal activity and its effect on a range of human ion channels.

RESULTS

Seven peptides named poneritoxins (PONTXs) were isolated and sequenced. The three-dimensional structure of synthetic Ae1a revealed a novel, compact scaffold in which a C-terminal β-hairpin is connected to the N-terminal region via two disulfide bonds. Synthetic Ae1a reversibly paralyzed blowflies and inhibited human L-type voltage-gated calcium channels (CaV1).

CONCLUSIONS

Poneritoxins from Anochetus emarginatus venom are a novel class of toxins that are structurally unique among animal venoms.

GENERAL SIGNIFICANCE

This study demonstrates that Anochetus ant venoms are a rich source of novel ion channel modulating peptides, some of which might be useful leads for the development of biopesticides.

Gramine Derivatives Targeting Ca(2+) Channels and Ser/Thr Phosphatases: A New Dual Strategy for the Treatment of Neurodegenerative Diseases

We describe the synthesis of gramine derivatives and their pharmacological evaluation as multipotent drugs for the treatment of Alzheimer's disease. An innovative multitarget approach is presented, targeting both voltage-gated Ca(2+) channels, classically studied for neurodegenerative diseases, and Ser/Thr phosphatases, which have been marginally aimed, even despite their key role in protein τ dephosphorylation. Twenty-five compounds were synthesized, and mostly their neuroprotective profile exceeded that offered by the head compound gramine. In general, these compounds reduced the entry of Ca(2+) through VGCC, as measured by Fluo-4/AM and patch clamp techniques, and protected in Ca(2+) overload-induced models of neurotoxicity, like glutamate or veratridine exposures. Furthermore, we hypothesize that these compounds decrease τ hyperphosphorylation based on the maintenance of the Ser/Thr phosphatase activity and their neuroprotection against the damage caused by okadaic acid. Hence, we propose this multitarget approach as a new and promising strategy for the treatment of neurodegenerative diseases.

CaV channels and cancer: canonical functions indicate benefits of repurposed drugs as cancer therapeutics

The importance of ion channels in the hallmarks of many cancers is increasingly recognised. This article reviews current knowledge of the expression of members of the voltage-gated calcium channel family (Ca_V) in cancer at the gene and protein level and discusses their potential functional roles. The ten members of the Ca_V channel family are classified according to expression of their pore-forming α-subunit; moreover, co-expression of accessory α2δ, β and γ confers a spectrum of biophysical characteristics including voltage dependence of activation and inactivation, current amplitude and activation/inactivation kinetics. Ca_V channels have traditionally been studied in excitable cells including neurones, smooth muscle, skeletal muscle and cardiac cells, and drugs targeting the channels are used in the treatment of hypertension and epilepsy. There is emerging evidence that several Ca_V channels are differentially expressed in cancer cells compared to their normal counterparts. Interestingly, a number of Ca_V channels also have non-canonical functions and are involved in transcriptional regulation of the expression of other proteins including potassium channels. Pharmacological studies show that Ca_V canonical function contributes to the fundamental biology of proliferation, cell-cycle progression and apoptosis. This raises the intriguing possibility that calcium channel blockers, approved for the treatment of other conditions, could be repurposed to treat particular cancers. Further research will reveal the full extent of both the canonical and non-canonical functions of Ca_V channels in cancer and whether calcium channel blockers are beneficial in cancer treatment.

Neuronal cell lines as model dorsal root ganglion neurons: A transcriptomic comparison

BACKGROUND

Dorsal root ganglion neuron-derived immortal cell lines including ND7/23 and F-11 cells have been used extensively as in vitro model systems of native peripheral sensory neurons. However, while it is clear that some sensory neuron-specific receptors and ion channels are present in these cell lines, a systematic comparison of the molecular targets expressed by these cell lines with those expressed in intact peripheral neurons is lacking.

RESULTS

In this study, we examined the expression of RNA transcripts in the human neuroblastoma-derived cell line, SH-SY5Y, and two dorsal root ganglion hybridoma cell lines, F-11 and ND7/23, using Illumina next-generation sequencing, and compared the results with native whole murine dorsal root ganglions. The gene expression profiles of these three cell lines did not resemble any specific defined dorsal root ganglion subclass. The cell lines lacked many markers for nociceptive sensory neurons, such as the Transient receptor potential V1 gene, but expressed markers for both myelinated and unmyelinated neurons. Global gene ontology analysis on whole dorsal root ganglions and cell lines showed similar enrichment of biological process terms across all samples.

CONCLUSIONS

This paper provides insights into the receptor repertoire expressed in common dorsal root ganglion neuron-derived cell lines compared with whole murine dorsal root ganglions, and illustrates the limits and potentials of these cell lines as tools for neuropharmacological exploration.

Inhibitory gene expression of the Cav3.1 T-type calcium channel to improve neuronal injury induced by lidocaine hydrochloride

Cav3.1 is a low-voltage-activated (LVA) calcium channel that plays a key role in regulating intracellular calcium ion levels. In this study, we observed the effects of lidocaine hydrochloride on the pshRNA-CACNA1G-SH-SY5Y cells that silenced Cav3.1 mRNA by RNA interference, and investigated the roles of p38 MAPK in these effects. We constructed the pNC-puro-CACNA1G-SH-SY5Y cells and pshRNA-CACNA1G -SH-SY5Y cells by the RNA interference. All the cells were cultured with or without 10mM lidocaine hydrochloride for 24 h. The cell morphology, cell viability, Cav3.1 and p38 protein expression, cell apoptosis rate and intracellular calcium ion concentration were detected. We found that all cells treated with 10mM lidocaine hydrochloride for 24 h showed cellular rounding, axonal regression, and cellular floating. Compared with the cells in SH-SY5Y+Lido group and NC+Lido group, those in the RNAi+Lido group showed similar changes, but of smaller magnitude. Additionally, following lidocaine hydrochloride all cells displayed increased Cav3.1 and p38 MAPK protein, apoptosis rate, and intracellular calcium ion levels; however,these changes in the RNAi+Lido group were less pronounced than in the SH-SY5Y+Lido and NC+Lido groups. The cell viability decreased following lidocaine hydrochloride treatment, but viability of the cells in the RNAi+Lido group was higher than in the SH-SY5Y+Lido and NC+Lido groups. The results showed that Cav3.1 may be involved in neuronal injury induced by lidocaine hydrochloride and that p38 MAPK phosphorylation was reduced upon Cav3.1 gene silencing.

A novel acetylcholinesterase inhibitor and calcium channel blocker SCR-1693 improves Aβ25-35-impaired mouse cognitive function

RATIONALE

The mechanism involved in AD is complex, which has prompted to develop compounds that could simultaneously interact with several potential targets. Here, we report a new synthesized compound SCR-1693 which is designed to target both AChE and calcium channels that are potential for AD therapy.

OBJECTIVES

We investigated the effects of SCR-1693 on AChE and calcium channels, the effects of neuroprotection and anti-amnesia in icv-Aβ25-35-injected mice, and the potential mechanisms.

METHODS

AChE activity assay, intracellular Ca(2+) content and calcium currents measurement, and Aβ25-35-induced cellular death determine were performed for validation of designed targets and neuroprotection of SCR-1693. Mice were orally administrated with SCR-1693 once daily after an Aβ25-35 injection. The Morris water maze and Y-maze test, and hippocampal protein detection were conducted on days 5-10, day 11, and day 8. The pyramidal neuron number, hippocampal AChE activity, and synaptic transmission were measured on day 12.

RESULTS

SCR-1693 acted as a selective, reversible, and noncompetitive inhibitor of AChE, and a nonselective voltage-gated calcium channel blocker. SCR-1693 also inhibited the increase of AChE activity in the mouse hippocampus. SCR-1693 was more effective than donepezil and memantine in preventing Aβ25-35-induced long-term and short-term memory impairment, maintaining the basal transmission of Schaffer collateral-CA1 synapses, and sustaining LTP in mouse hippocampus. SCR-1693 attenuated Aβ25-35-induced death of SH-SY5Y cell and the loss of hippocampal pyramidal neurons, and regulated Aβ25-35-induced signal cascade in neurons.

CONCLUSIONS

All these findings indicated that SCR-1693, as a double-target-direction agent, is a considerable candidate for AD therapy.

Bioactive Mimetics of Conotoxins and other Venom Peptides

Ziconotide (Prialt^®), a synthetic version of the peptide ω-conotoxin MVIIA found in the venom of a fish-hunting marine cone snail Conus magnus, is one of very few drugs effective in the treatment of intractable chronic pain. However, its intrathecal mode of delivery and narrow therapeutic window cause complications for patients. This review will summarize progress in the development of small molecule, non-peptidic mimics of Conotoxins and a small number of other venom peptides. This will include a description of how some of the initially designed mimics have been modified to improve their drug-like properties.

Comparative Venomics Reveals the Complex Prey Capture Strategy of the Piscivorous Cone Snail Conus catus

Venomous marine cone snails produce a unique and remarkably diverse range of venom peptides (conotoxins and conopeptides) that have proven to be invaluable as pharmacological probes and leads to new therapies. Conus catus is a hook-and-line fish hunter from clade I, with ∼20 conotoxins identified, including the analgesic ω-conotoxin CVID (AM336). The current study unravels the venom composition of C. catus with tandem mass spectrometry and 454 sequencing data. From the venom gland transcriptome, 104 precursors were recovered from 11 superfamilies, with superfamily A (especially κA-) conotoxins dominating (77%) their venom. Proteomic analysis confirmed that κA-conotoxins dominated the predation-evoked milked venom of each of six C. catus analyzed and revealed remarkable intraspecific variation in both the intensity and type of conotoxins. High-throughput FLIPR assays revealed that the predation-evoked venom contained a range of conotoxins targeting the nAChR, Cav, and Nav ion channels, consistent with α- and ω-conotoxins being used for predation by C. catus. However, the κA-conotoxins did not act at these targets but induced potent and rapid immobilization followed by bursts of activity and finally paralysis when injected intramuscularly in zebrafish. Our venomics approach revealed the complexity of the envenomation strategy used by C. catus, which contains a mix of both excitatory and inhibitory venom peptides.

Identification and Characterization of ProTx-III [μ-TRTX-Tp1a], a New Voltage-Gated Sodium Channel Inhibitor from Venom of the Tarantula Thrixopelma pruriens

Spider venoms are a rich source of ion channel modulators with therapeutic potential. Given the analgesic potential of subtype-selective inhibitors of voltage-gated sodium (NaV) channels, we screened spider venoms for inhibitors of human NaV1.7 (hNaV1.7) using a high-throughput fluorescent assay. Here, we describe the discovery of a novel NaV1.7 inhibitor, μ-TRTX-Tp1a (Tp1a), isolated from the venom of the Peruvian green-velvet tarantula Thrixopelma pruriens. Recombinant and synthetic forms of this 33-residue peptide preferentially inhibited hNaV1.7 > hNaV1.6 > hNaV1.2 > hNaV1.1 > hNaV1.3 channels in fluorescent assays. NaV1.7 inhibition was diminished (IC50 11.5 nM) and the association rate decreased for the C-terminal acid form of Tp1a compared with the native amidated form (IC50 2.1 nM), suggesting that the peptide C terminus contributes to its interaction with hNaV1.7. Tp1a had no effect on human voltage-gated calcium channels or nicotinic acetylcholine receptors at 5 μM. Unlike most spider toxins that modulate NaV channels, Tp1a inhibited hNaV1.7 without significantly altering the voltage dependence of activation or inactivation. Tp1a proved to be analgesic by reversing spontaneous pain induced in mice by intraplantar injection in OD1, a scorpion toxin that potentiates hNaV1.7. The structure of Tp1a as determined using NMR spectroscopy revealed a classic inhibitor cystine knot (ICK) motif. The molecular surface of Tp1a presents a hydrophobic patch surrounded by positively charged residues, with subtle differences from other ICK spider toxins that might contribute to its different pharmacological profile. Tp1a may help guide the development of more selective and potent hNaV1.7 inhibitors for treatment of chronic pain.

Inhibition of N-type calcium channels by fluorophenoxyanilide derivatives

A set of fluorophenoxyanilides, designed to be simplified analogues of previously reported ω-conotoxin GVIA mimetics, were prepared and tested for N-type calcium channel inhibition in a SH-SY5Y neuroblastoma FLIPR assay. N-type or Ca_v2.2 channel is a validated target for the treatment of refractory chronic pain. Despite being significantly less complex than the originally designed mimetics, up to a seven-fold improvement in activity was observed.

Seven novel modulators of the analgesic target NaV 1.7 uncovered using a high-throughput venom-based discovery approach

BACKGROUND AND PURPOSE

Chronic pain is a serious worldwide health issue, with current analgesics having limited efficacy and dose-limiting side effects. Humans with loss-of-function mutations in the voltage-gated sodium channel NaV 1.7 (hNaV 1.7) are indifferent to pain, making hNaV 1.7 a promising target for analgesic development. Since spider venoms are replete with NaV channel modulators, we examined their potential as a source of hNaV 1.7 inhibitors.

EXPERIMENTAL APPROACH

We developed a high-throughput fluorescent-based assay to screen spider venoms against hNaV 1.7 and isolate 'hit' peptides. To examine the binding site of these peptides, we constructed a panel of chimeric channels in which the S3b-S4 paddle motif from each voltage sensor domain of hNaV 1.7 was transplanted into the homotetrameric KV 2.1 channel.

KEY RESULTS

We screened 205 spider venoms and found that 40% contain at least one inhibitor of hNaV 1.7. By deconvoluting 'hit' venoms, we discovered seven novel members of the NaSpTx family 1. One of these peptides, Hd1a (peptide μ-TRTX-Hd1a from venom of the spider Haplopelma doriae), inhibited hNaV 1.7 with a high level of selectivity over all other subtypes, except hNaV 1.1. We showed that Hd1a is a gating modifier that inhibits hNaV 1.7 by interacting with the S3b-S4 paddle motif in channel domain II. The structure of Hd1a, determined using heteronuclear NMR, contains an inhibitor cystine knot motif that is likely to confer high levels of chemical, thermal and biological stability.

CONCLUSION AND IMPLICATIONS

Our data indicate that spider venoms are a rich natural source of hNaV 1.7 inhibitors that might be useful leads for the development of novel analgesics.

Evolution of separate predation- and defence-evoked venoms in carnivorous cone snails

Venomous animals are thought to inject the same combination of toxins for both predation and defence, presumably exploiting conserved target pharmacology across prey and predators. Remarkably, cone snails can rapidly switch between distinct venoms in response to predatory or defensive stimuli. Here, we show that the defence-evoked venom of Conus geographus contains high levels of paralytic toxins that potently block neuromuscular receptors, consistent with its lethal effects on humans. In contrast, C. geographus predation-evoked venom contains prey-specific toxins mostly inactive at human targets. Predation- and defence-evoked venoms originate from the distal and proximal regions of the venom duct, respectively, explaining how different stimuli can generate two distinct venoms. A specialized defensive envenomation strategy is widely evolved across worm, mollusk and fish-hunting cone snails. We propose that defensive toxins, originally evolved in ancestral worm-hunting cone snails to protect against cephalopod and fish predation, have been repurposed in predatory venoms to facilitate diversification to fish and mollusk diets.

Neuroprotective effect of steroidal alkaloids on glutamate-induced toxicity by preserving mitochondrial membrane potential and reducing oxidative stress

Several evidences suggest that enhanced oxidative stress is involved in the pathogenesis and/or progression of several neurodegenerative diseases. The aim of this study was to investigate for the first time whether both extracts from tomato plant (Lycopersicon esculentum Mill.) leaves and their isolated steroidal alkaloids (tomatine and tomatidine) afford neuroprotective effect against glutamate-induced toxicity in SH-SY5Y neuroblastoma cells and to elucidate the mechanisms underlying this protection. Steroidal alkaloids from tomato are well known for their cholinesterases' inhibitory capacity and the results showed that both purified extracts and isolated compounds, at non-toxic concentrations for gastric (AGS), intestinal (Caco-2) and neuronal (SH-SY5Y) cells, have the capacity to preserve mitochondria membrane potential and to decrease reactive oxygen species levels of SH-SY5Y glutamate-insulted cells. Moreover, the use of specific antagonists of cholinergic receptors allowed observing that tomatine and tomatidine can interact with nicotinic receptors, specifically with the α7 type. No effect on muscarinic receptors was noticed. In addition to the selective cholinesterases' inhibition revealed by the compounds/extracts, these results provide novel and important insights into their neuroprotective mechanism. This work also demystifies the applicability of these compounds in therapeutics, by demonstrating that their toxicity was overestimated for long time.

The potential role of CAMSAP1L1 in symptomatic epilepsy

In a recent genome-wide association study (GWAS) of symptomatic epilepsy in the Chinese population, the most significant single nucleotide polymorphism (SNP) allele was rs2292096 [G] (P=1.0×10(-8), odds ratio [OR]=0.63), in the CAMSAP1L1 gene (also known as CAMSAP2). Here, we report that rs2292096 genotypes tended to associate with expression of CAMSAP1L1 RNA in the temporal lobe (p=0.054) and hippocampus (p=0.20) of epilepsy surgery patients, with expression tending to increase with the G allele. CAMSAP1L1 and β-tubulin double immunofluorescence exhibited partial overlap. CAMSAP1L1 siRNA transfection of human SH-SY5Y neuroblastoma cells treated with or without retinoic acid reduced the CAMSAP1L1 protein level nearly 60% and stimulated neurite outgrowth, as measured by total length, number of processes and number of branches. Therefore, the rs2292096 G allele of CAMSAP1L1, which was associated with reduced risk of symptomatic epilepsy, tended to associate with increased expression of CAMSAP1L1, which represses neurite outgrowth. Greater neurite growth in response to brain insults might increase formation of ectopic neural circuits and thus the risk of epileptogenesis.