alpha-Latrotoxin and its receptors

Structural basis of α-latrotoxin transition to a cation-selective pore

The potent neurotoxic venom of the black widow spider contains a cocktail of seven phylum-specific latrotoxins (LTXs), but only one, α-LTX, targets vertebrates. This 130 kDa toxin binds to receptors at presynaptic nerve terminals and triggers a massive release of neurotransmitters. It is widely accepted that LTXs tetramerize and insert into the presynaptic membrane, thereby forming Ca2+-conductive pores, but the underlying mechanism remains poorly understood. LTXs are homologous and consist of an N-terminal region with three distinct domains, along with a C-terminal domain containing up to 22 consecutive ankyrin repeats. Here we report cryoEM structures of the vertebrate-specific α-LTX tetramer in its prepore and pore state. Our structures, in combination with AlphaFold2-based structural modeling and molecular dynamics simulations, reveal dramatic conformational changes in the N-terminal region of the complex. Four distinct helical bundles rearrange and together form a highly stable, 15 nm long, cation-impermeable coiled-coil stalk. This stalk, in turn, positions an N-terminal pair of helices within the membrane, thereby enabling the assembly of a cation-permeable channel. Taken together, these data give insight into a unique mechanism for membrane insertion and channel formation, characteristic of the LTX family, and provide the necessary framework for advancing novel therapeutics and biotechnological applications.

Envenomation by the Indian ornamental tarantula (Poecilotheria regalis): A case report on treatment with Latrodectus mactans antivenom

Poecilotheria spiders are considered theraphosids of underestimated clinical importance, with bites from these species inducing symptoms such as severe pain and intense muscle cramps. However, there is no specific treatment for the envenomation caused by these species, which, while native to India and Sri Lanka, are widely distributed worldwide. The present study reports the case of a 31-year-old man bitten by a Poecilotheria regalis specimen. The patient's clinical presentation was similar to Latrodectus envenomation, and patient was treated with an L. mactans antivenom. Most of patient's symptoms improved (fasciculations, pain, erythema, and local swelling), except muscle cramps. A toxicological study conducted on mice did not show that L. mactans antivenom has a neutralizing effect on the toxicity of P. regalis. The present report discusses the envenoming process of Poecilotheria species and the possible neutralizing effect exerted by L. mactans antivenom.

Diversely evolved xibalbin variants from remipede venom inhibit potassium channels and activate PKA-II and Erk1/2 signaling

BACKGROUND

The identification of novel toxins from overlooked and taxonomically exceptional species bears potential for various pharmacological applications. The remipede Xibalbanus tulumensis, an underwater cave-dwelling crustacean, is the only crustacean for which a venom system has been described. Its venom contains several xibalbin peptides that have an inhibitor cysteine knot (ICK) scaffold.

RESULTS

Our screenings revealed that all tested xibalbin variants particularly inhibit potassium channels. Xib1 and xib13 with their eight-cysteine domain similar to spider knottins also inhibit voltage-gated sodium channels. No activity was noted on calcium channels. Expanding the functional testing, we demonstrate that xib1 and xib13 increase PKA-II and Erk1/2 sensitization signaling in nociceptive neurons, which may initiate pain sensitization. Our phylogenetic analysis suggests that xib13 either originates from the common ancestor of pancrustaceans or earlier while xib1 is more restricted to remipedes. The ten-cysteine scaffolded xib2 emerged from xib1, a result that is supported by our phylogenetic and machine learning-based analyses.

CONCLUSIONS

Our functional characterization of synthesized variants of xib1, xib2, and xib13 elucidates their potential as inhibitors of potassium channels in mammalian systems. The specific interaction of xib2 with Kv1.6 channels, which are relevant to treating variants of epilepsy, shows potential for further studies. At higher concentrations, xib1 and xib13 activate the kinases PKA-II and ERK1/2 in mammalian sensory neurons, suggesting pain sensitization and potential applications related to pain research and therapy. While tested insect channels suggest that all probably act as neurotoxins, the biological function of xib1, xib2, and xib13 requires further elucidation. A novel finding on their evolutionary origin is the apparent emergence of X. tulumensis-specific xib2 from xib1. Our study is an important cornerstone for future studies to untangle the origin and function of these enigmatic proteins as important components of remipede but also other pancrustacean and arthropod venoms.

α-Latrotoxin Tetramers Spontaneously Form Two-Dimensional Crystals in Solution and Coordinated Multi-Pore Assemblies in Biological Membranes

α-Latrotoxin (α-LTX) was found to form two-dimensional (2D) monolayer arrays in solution at relatively low concentrations (0.1 mg/mL), with the toxin tetramer constituting a unit cell. The crystals were imaged using cryogenic electron microscopy (cryoEM), and image analysis yielded a ~12 Å projection map. At this resolution, no major conformational changes between the crystalline and solution states of α-LTX tetramers were observed. Electrophysiological studies showed that, under the conditions of crystallization, α-LTX simultaneously formed multiple channels in biological membranes that displayed coordinated gating. Two types of channels with conductance levels of 120 and 208 pS were identified. Furthermore, we observed two distinct tetramer conformations of tetramers both when observed as monodisperse single particles and within the 2D crystals, with pore diameters of 11 and 13.5 Å, suggestive of a flickering pore in the middle of the tetramer, which may correspond to the two states of toxin channels with different conductance levels. We discuss the structural changes that occur in α-LTX tetramers in solution and propose a mechanism of α-LTX insertion into the membrane. The propensity of α-LTX tetramers to form 2D crystals may explain many features of α-LTX toxicology and suggest that other pore-forming toxins may also form arrays of channels to exert maximal toxic effect.

Perioral Paresthesia, Generalize Muscle Cramps, and Rhabdomyolysis After a Socotra Island Blue Baboon Tarantula (Monocentropus Balfouri) Bite

BACKGROUND

Literature on systemic envenomation caused by tarantula bites, particularly from the Theraphosidae family, is relatively scarce. This case report provides a formal description of the first known instance of systemic envenomation caused by the Socotra Island Blue Baboon Tarantula (Monocentropus balfouri).

CASE REPORT

In this case, a 23-year-old employee of an exotic pet shop suffered from perioral paresthesia, generalized muscle cramps, and rhabdomyolysis because of a Monocentropus balfouri bite. His symptoms were successfully relieved with oral benzodiazepines. EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case highlights the potential for serious complications resulting from the bite of Monocentropus balfouri, a species gaining popularity among global exotic pet collectors.

Visible Light Control over the Cytolytic Activity of a Toxic Pore-Forming Protein

Enabling control over the bioactivity of proteins with light, along with the principles of photopharmacology, has the potential to generate safe and targeted medical treatments. Installing light sensitivity in a protein can be achieved through its covalent modification with a molecular photoswitch. The general challenge in this approach is the need for the use of low energy visible light for the regulation of bioactivity. In this study, we report visible light control over the cytolytic activity of a protein. A water-soluble visible-light-operated tetra-ortho-fluoro-azobenzene photoswitch was synthesized by utilizing the nucleophilic aromatic substitution reaction for installing a solubilizing sulfonate group onto the electron-poor photoswitch structure. The azobenzene was attached to two cysteine mutants of the pore-forming protein fragaceatoxin C (FraC), and their respective activities were evaluated on red blood cells. For both mutants, the green-light-irradiated sample, containing predominantly the cis-azobenzene isomer, was more active compared to the blue-light-irradiated sample. Ultimately, the same modulation of the cytolytic activity pattern was observed toward a hypopharyngeal squamous cell carcinoma. These results constitute the first case of using low energy visible light to control the biological activity of a toxic protein.

GPR56 C-terminal fragment mediates signal received by N-terminal fragment of another adhesion GPCR Latrophilin1 in neurons

Adhesion GPCRs (aGPCRs) are a subfamily of GPCRs that are involved in cell adhesion, cell proliferation, and cell migration in various tissues. G protein-coupled receptor proteolytic site (GPS) of aGPCR is required to cleave the extracellular domain autocatalytically, generating two fragments; a N-terminal fragment (NTF) and a C-terminal fragment (CTF) containing seven transmembrane structure. NTF can interact with CTF non-covalently after cleavage, however the physiological significance of the cleavage of aGPCR at GPS, and also the interaction between NTF and CTF have not been fully clarified yet. In this study, we first investigated the expression profiles of two aGPCRs, GPR56/ADGRG1, and LPHN1/ADGRL1 in mouse brain, and found that the NTF and CTF of GPR56 independently expressed in different brain region at different developmental stages. Immunoprecipitation of GPR56CTF co-immunoprecipitated LPHN1NTF from mouse brain and HEK293T cells expressing both fragments. Stimulation with LPHN1 ligand, α-Latrotoxin N4C (αLTXN4C), to cells expressing LPHN1NTF and GPR56CTF increased intracellular Ca²⁺ concentration ([Ca²⁺ ]i). We also demonstrated that GPR56KO mouse neurons attenuated their Ca²⁺ response to αLTXN4C. These results suggest the possibility of functional and chimeric complex containing LPHN1NTF and GPR56CTF in neuronal signal transduction.

Hydrogen peroxide induced by nerve injury promotes axon regeneration via connective tissue growth factor

Regeneration of the neuromuscular junction (NMJ) leverages on extensive exchange of factors released from motor axon terminals (MATs), muscle fibers and perisynaptic Schwann cells (PSCs), among which hydrogen peroxide (H₂O₂) is a major pro-regenerative signal. To identify critical determinants of NMJ remodeling in response to injury, we performed temporal transcriptional profiling of NMJs from 2 month-old mice during MAT degeneration/regeneration, and cross-referenced the differentially expressed genes with those elicited by H₂O₂ in SCs. We identified an enrichment in extracellular matrix (ECM) transcripts, including Connective Tissue Growth Factor (Ctgf), which is usually expressed during development. We discovered that Ctgf levels are increased in a Yes-associated protein (YAP)-dependent fashion in response to rapid, local H₂O₂ signaling generated by stressed mitochondria in the injured sciatic nerve, a finding highlighting the importance of signals triggered by mechanical force to motor nerve repair. Through sequestration of Ctgf or inactivation of H₂O₂, we delayed the recovery of neuromuscular function by impairing SC migration and, in turn, axon-oriented re-growth. These data indicate that H₂O₂ and its downstream effector Ctgf are pro-regenerative factors that enable axonal growth, and reveal a striking ECM remodeling process during nerve regeneration upon local H₂O₂ signaling. Our study identifies key transcriptomic changes at the regenerating NMJ, providing a rich source of pro-regenerative factors with potential for alleviating the consequences of peripheral nerve injuries.

Role of Teneurin C-Terminal Associated Peptides (TCAP) on Intercellular Adhesion and Communication

The teneurin C-terminal associated peptides (TCAP) are encoded by the terminal exon of all metazoan teneurin genes. Evidence supports the liberation of a soluble TCAP peptide either by proteolytic cleavage from the mature transmembrane teneurin protein or by a separately transcribed mRNA. Synthetic versions of TCAP, based on its genomic structure, are efficacious at regulating intercellular communication by promoting neurite outgrowth and increasing dendritic spine density in vitro and in vivo in rodent models. This is achieved through cytoskeletal re-arrangement and metabolic upregulation. The putative receptors for TCAPs are the latrophilin (LPHN) family of adhesion G-protein coupled receptors, which facilitate TCAP’s actions through G-proteins associated with cAMP and calcium-regulating signalling pathways. The teneurin/TCAP and latrophilin genes are phylogenetically ancient, likely serving primitive functions in cell adhesion and energy regulation which have been since adapted for a more complex role in synaptogenesis in vertebrate nervous systems.

Pain-related toxins in scorpion and spider venoms: a face to face with ion channels

Pain is a common symptom induced during envenomation by spiders and scorpions. Toxins isolated from their venom have become essential tools for studying the functioning and physiopathological role of ion channels, as they modulate their activity. In particular, toxins that induce pain relief effects can serve as a molecular basis for the development of future analgesics in humans. This review provides a summary of the different scorpion and spider toxins that directly interact with pain-related ion channels, with inhibitory or stimulatory effects. Some of these toxins were shown to affect pain modalities in different animal models providing information on the role played by these channels in the pain process. The close interaction of certain gating-modifier toxins with membrane phospholipids close to ion channels is examined along with molecular approaches to improve selectivity, affinity or bioavailability in vivo for therapeutic purposes.

Molecular architecture of black widow spider neurotoxins

Latrotoxins (LaTXs) are presynaptic pore-forming neurotoxins found in the venom of Latrodectus spiders. The venom contains a toxic cocktail of seven LaTXs, with one of them targeting vertebrates (α-latrotoxin (α-LTX)), five specialized on insects (α, β, γ, δ, ε- latroinsectotoxins (LITs), and one on crustaceans (α-latrocrustatoxin (α-LCT)). LaTXs bind to specific receptors on the surface of neuronal cells, inducing the release of neurotransmitters either by directly stimulating exocytosis or by forming Ca²⁺-conductive tetrameric pores in the membrane. Despite extensive studies in the past decades, a high-resolution structure of a LaTX is not yet available and the precise mechanism of LaTX action remains unclear. Here, we report cryoEM structures of the α-LCT monomer and the δ-LIT dimer. The structures reveal that LaTXs are organized in four domains. A C-terminal domain of ankyrin-like repeats shields a central membrane insertion domain of six parallel α-helices. Both domains are flexibly linked via an N-terminal α-helical domain and a small β-sheet domain. A comparison between the structures suggests that oligomerization involves major conformational changes in LaTXs with longer C-terminal domains. Based on our data we propose a cyclic mechanism of oligomerization, taking place prior membrane insertion. Both recombinant α-LCT and δ-LIT form channels in artificial membrane bilayers, that are stabilized by Ca²⁺ ions and allow calcium flux at negative membrane potentials. Our comparative analysis between α-LCT and δ-LIT provides first crucial insights towards understanding the molecular mechanism of the LaTX family.

The venom of Latrodectus spiders contains seven Latrotoxins (LaTXs), among them α-latrocrustatoxin (LCT) and δ- latroinsectotoxins δ-LIT. LaTXs bind to specific receptors on the surface of neuronal cells and target the molecular exocytosis machinery. Here, the authors present the cryo-EM structure of the α-LCT monomer and the δ-LIT dimer, which reveal that LaTXs are organized in four domains and they discuss the potential oligomerisation mechanism that takes place before LaTXs membrane insertion. Both recombinant α-LCT and δ-LIT form channels in artificial membrane bilayers, that are stabilized by Ca²⁺ ions.

Widow spiders in the New World: a review on Latrodectus Walckenaer, 1805 (Theridiidae) and latrodectism in the Americas

Humankind has always been fascinated by venomous animals, as their toxic substances have transformed them into symbols of power and mystery. Over the centuries, researchers have been trying to understand animal venoms, unveiling intricate mixtures of molecules and their biological effects. Among venomous animals, Latrodectus Walckenaer, 1805 (widow spiders) have become feared in many cultures worldwide due to their extremely neurotoxic venom. The Latrodectus genus encompasses 32 species broadly spread around the globe, 14 of which occur in the Americas. Despite the high number of species found in the New World, the knowledge on these spiders is still scarce. This review covers the general knowledge on Latrodectus spp. from the Americas. We address widow spiders' taxonomy; geographical distribution and epidemiology; symptoms and treatments of envenomation (latrodectism); venom collection, experimental studies, proteome and transcriptome; and biotechnological studies on these Latrodectus spp. Moreover, we discuss the main challenges and limitations faced by researchers when trying to comprehend this neglected group of medically important spiders. We expect this review to help overcome the lack of information regarding widow spiders in the New World.

The biology and evolution of spider venoms

Spiders are diverse, predatory arthropods that have inhabited Earth for around 400 million years. They are well known for their complex venom systems that are used to overpower their prey. Spider venoms contain many proteins and peptides with highly specific and potent activities suitable for biomedical or agrochemical applications, but the key role of venoms as an evolutionary innovation is often overlooked, even though this has enabled spiders to emerge as one of the most successful animal lineages. In this review, we discuss these neglected biological aspects of spider venoms. We focus on the morphology of spider venom systems, their major components, biochemical and chemical plasticity, as well as ecological and evolutionary trends. We argue that the effectiveness of spider venoms is due to their unprecedented complexity, with diverse components working synergistically to increase the overall potency. The analysis of spider venoms is difficult to standardize because they are dynamic systems, fine-tuned and modified by factors such as sex, life-history stage and biological role. Finally, we summarize the mechanisms that drive spider venom evolution and highlight the need for genome-based studies to reconstruct the evolutionary history and physiological networks of spider venom compounds with more certainty.

The protective effect and potential mechanism of NRXN1 on learning and memory in ADHD rat models

The learning and memory network is highly complex and remains unclear. The hippocampus is the location of learning and memory function. Impairment of synaptic morphology and synaptic plasticity (i.e., long-term potentiation) appears to cause learning and memory deficits. Several studies have indicated the role of NRXN1 in regulating the synaptic function, but little is known on its role in learning and memory dysfunction associated with attention deficit and hyperactivity disorder (ADHD). Our results showed that overexpression and interference of NRXN1 in vivo, respectively, affected learning and memory, as was assessed by Morris water maze tests, in spontaneously hypertensive rats (SHRs) and Sprague Dawley (SD) rats. We found that SD rats performed better after methylphenidate (MPH) treatment in salvage trials. Accordingly, the change of NRXN1 led to altered synapse-related gene (PSD95, SYN1, GAP43, NLGN1) expression, further providing evidence of its role in the maintenance of synaptic plasticity. We also verified that the expression of synapse-related genes synchronously changed with NRXN1expression in the behavioral assessment. The expression of NRXN1 was confirmed to affect the expression of synapse-related genes after its interference and overexpression in the primary hippocampal neurons in vitro. These results confirmed our hypothesis that NRXN1 might nucleate an overall trans-synaptic signaling network that controls synaptic plasticity and is responsible for impairments in learning and memory in ADHD. These findings suggest a possible protective role of NRXN1 in learning and memory in ADHD. Further RNA-seq sequencing revealed significant differences in the expression of 5-hydroxytryptamine receptor (5-HT₆R), which was further verified at the cellular level, and the mechanism of NRXN1 affecting synaptic plasticity was preliminarily discussed.

Melatonin promotes regeneration of injured motor axons via MT1 receptors

Melatonin is an ancient multi-tasking molecule produced by the pineal gland and by several extrapineal tissues. A variety of activities has been ascribed to this hormone in different physiological and pathological contexts, but little is known about its role in peripheral neuroregeneration. Here, we have exploited two different types of injury to test the capability of melatonin to stimulate regeneration of motor axons: (a) the acute and reversible presynaptic degeneration induced by the spider neurotoxin α-Latrotoxin and (b) the compression/transection of the sciatic nerve. We found that in both cases melatonin administration accelerates the process of nerve repair. This pro-regenerative action is MT1 -mediated, and at least in part due to a sustained activation of the ERK1/2 pathway. These findings reveal a receptor-mediated, pro-regenerative action of melatonin in vivo that holds important clinical implications, as it posits melatonin as a safe candidate molecule for the treatment of a number of peripheral neurodegenerative conditions.

Discovery of a Recombinant Human Monoclonal Immunoglobulin G Antibody Against α-Latrotoxin From the Mediterranean Black Widow Spider (Latrodectus tredecimguttatus)

Widow spiders are among the few spider species worldwide that can cause serious envenoming in humans. The clinical syndrome resulting from Latrodectus spp. envenoming is called latrodectism and characterized by pain (local or regional) associated with diaphoresis and nonspecific systemic effects. The syndrome is caused by α-latrotoxin, a ~130 kDa neurotoxin that induces massive neurotransmitter release. Due to this function, α-latrotoxin has played a fundamental role as a tool in the study of neuroexocytosis. Nevertheless, some questions concerning its mode of action remain unresolved today. The diagnosis of latrodectism is purely clinical, combined with the patient's history of spider bite, as no analytical assays exist to detect widow spider venom. By utilizing antibody phage display technology, we here report the discovery of the first recombinant human monoclonal immunoglobulin G antibody (TPL0020_02_G9) that binds α-latrotoxin from the Mediterranean black widow spider (Latrodectus tredecimguttatus) and show neutralization efficacy ex vivo. Such antibody can be used as an affinity reagent for research and diagnostic purposes, providing researchers with a novel tool for more sophisticated experimentation and analysis. Moreover, it may also find therapeutic application in future.

Signals Orchestrating Peripheral Nerve Repair

The peripheral nervous system has retained through evolution the capacity to repair and regenerate after assault from a variety of physical, chemical, or biological pathogens. Regeneration relies on the intrinsic abilities of peripheral neurons and on a permissive environment, and it is driven by an intense interplay among neurons, the glia, muscles, the basal lamina, and the immune system. Indeed, extrinsic signals from the milieu of the injury site superimpose on genetic and epigenetic mechanisms to modulate cell intrinsic programs. Here, we will review the main intrinsic and extrinsic mechanisms allowing severed peripheral axons to re-grow, and discuss some alarm mediators and pro-regenerative molecules and pathways involved in the process, highlighting the role of Schwann cells as central hubs coordinating multiple signals. A particular focus will be provided on regeneration at the neuromuscular junction, an ideal model system whose manipulation can contribute to the identification of crucial mediators of nerve re-growth. A brief overview on regeneration at sensory terminals is also included.

Venomics Approach Reveals a High Proportion of Lactrodectus-Like Toxins in the Venom of the Noble False Widow Spider Steatoda nobilis

The noble false widow spider Steatoda nobilis originates from the Macaronesian archipelago and has expanded its range globally. Outside of its natural range, it may have a negative impact on native wildlife, and in temperate regions it lives in synanthropic environments where it frequently encounters humans, subsequently leading to envenomations. S. nobilis is the only medically significant spider in Ireland and the UK, and envenomations have resulted in local and systemic neurotoxic symptoms similar to true black widows (genus Latrodectus). S. nobilis is a sister group to Latrodectus which possesses the highly potent neurotoxins called α-latrotoxins that can induce neuromuscular paralysis and is responsible for human fatalities. However, and despite this close relationship, the venom composition of S. nobilis has never been investigated. In this context, a combination of transcriptomic and proteomic cutting-edge approaches has been used to deeply characterise S. nobilis venom. Mining of transcriptome data for the peptides identified by proteomics revealed 240 annotated sequences, of which 118 are related to toxins, 37 as enzymes, 43 as proteins involved in various biological functions, and 42 proteins without any identified function to date. Among the toxins, the most represented in numbers are α-latrotoxins (61), δ-latroinsectotoxins (44) and latrodectins (6), all of which were first characterised from black widow venoms. Transcriptomics alone provided a similar representation to proteomics, thus demonstrating that our approach is highly sensitive and accurate. More precisely, a relative quantification approach revealed that latrodectins are the most concentrated toxin (28%), followed by α-latrotoxins (11%), δ-latroinsectotoxins (11%) and α-latrocrustotoxins (11%). Approximately two-thirds of the venom is composed of Latrodectus-like toxins. Such toxins are highly potent towards the nervous system of vertebrates and likely responsible for the array of symptoms occurring after envenomation by black widows and false widows. Thus, caution should be taken in dismissing S. nobilis as harmless. This work paves the way towards a better understanding of the competitiveness of S. nobilis and its potential medical importance.

C-terminal phosphorylation of latrophilin-1/ADGRL1 affects the interaction between its fragments

Latrophilin-1 is an adhesion G protein-coupled receptor that mediates the effect of α-latrotoxin, causing massive release of neurotransmitters from nerve terminals and endocrine cells. Autoproteolysis cleaves latrophilin-1 into two parts: the extracellular N-terminal fragment (NTF) and the heptahelical C-terminal fragment (CTF). NTF and CTF can exist as independent proteins in the plasma membrane, but α-latrotoxin binding to NTF induces their association and G protein-mediated signaling. We demonstrate here that CTF in synapses is phosphorylated on multiple sites. Phosphorylated CTF has a high affinity for NTF and copurifies with it on affinity columns and sucrose density gradients. Dephosphorylated CTF has a lower affinity for NTF and can behave as a separate protein. α-Latrotoxin (and possibly other ligands of latrophilin-1) binds both to the NTF-CTF complex and receptor-like protein tyrosine phosphatase σ, bringing them together. This leads to CTF dephosphorylation and facilitates CTF release from the complex. We propose that ligand-dependent phosphorylation-dephosphorylation of latrophilin-1 could affect the interaction between its fragments and functions as a G protein-coupled receptor.

Pore-Forming Proteins from Cnidarians and Arachnids as Potential Biotechnological Tools

Animal venoms are complex mixtures of highly specialized toxic molecules. Cnidarians and arachnids produce pore-forming proteins (PFPs) directed against the plasma membrane of their target cells. Among PFPs from cnidarians, actinoporins stand out for their small size and molecular simplicity. While native actinoporins require only sphingomyelin for membrane binding, engineered chimeras containing a recognition antibody-derived domain fused to an actinoporin isoform can nonetheless serve as highly specific immunotoxins. Examples of such constructs targeted against malignant cells have been already reported. However, PFPs from arachnid venoms are less well-studied from a structural and functional point of view. Spiders from the Latrodectus genus are professional insect hunters that, as part of their toxic arsenal, produce large PFPs known as latrotoxins. Interestingly, some latrotoxins have been identified as potent and highly-specific insecticides. Given the proteinaceous nature of these toxins, their promising future use as efficient bioinsecticides is discussed throughout this Perspective. Protein engineering and large-scale recombinant production are critical steps for the use of these PFPs as tools to control agriculturally important insect pests. In summary, both families of PFPs, from Cnidaria and Arachnida, appear to be molecules with promising biotechnological applications.

A de novo variant in ADGRL2 suggests a novel mechanism underlying the previously undescribed association of extreme microcephaly with severely reduced sulcation and rhombencephalosynapsis

Extreme microcephaly and rhombencephalosynapsis represent unusual pathological conditions, each of which occurs in isolation or in association with various other cerebral and or extracerebral anomalies. Unlike microcephaly for which several disease-causing genes have been identified with different modes of inheritance, the molecular bases of rhombencephalosynapsis remain unknown and rhombencephalosynapsis presents mainly as a sporadic condition consistent with de novo dominant variations. We report for the first time the association of extreme microcephaly with almost no sulcation and rhombencephalosynapsis in a fœtus for which comparative patient-parent exome sequencing strategy revealed a heterozygous de novo missense variant in the ADGRL2 gene. ADGRL2 encodes latrophilin 2, an adhesion G-protein-coupled receptor whose exogenous ligand is α-latrotoxin. Adgrl2 immunohistochemistry and in situ hybridization revealed expression in the telencephalon, mesencephalon and rhombencephalon of mouse and chicken embryos. In human brain embryos and fœtuses, Adgrl2 immunoreactivity was observed in the hemispheric and cerebellar germinal zones, the cortical plate, basal ganglia, pons and cerebellar cortex. Microfluorimetry experiments evaluating intracellular calcium release in response to α-latrotoxin binding showed significantly reduced cytosolic calcium release in the fœtus amniocytes vs amniocytes from age-matched control fœtuses and in HeLa cells transfected with mutant ADGRL2 cDNA vs wild-type construct. Embryonic lethality was also observed in constitutive Adgrl2^−/− mice. In Adgrl2^+/− mice, MRI studies revealed microcephaly and vermis hypoplasia. Cell adhesion and wound healing assays demonstrated that the variation increased cell adhesion properties and reduced cell motility. Furthermore, HeLa cells overexpressing mutant ADGRL2 displayed a highly developed cytoplasmic F-actin network related to cytoskeletal dynamic modulation. ADGRL2 is the first gene identified as being responsible for extreme microcephaly with rhombencephalosynapsis. Increased cell adhesion, reduced cell motility and cytoskeletal dynamic alterations induced by the variant therefore represent a new mechanism responsible for microcephaly.

CXCL12α/SDF-1 from perisynaptic Schwann cells promotes regeneration of injured motor axon terminals

The neuromuscular junction has retained through evolution the capacity to regenerate after damage, but little is known on the inter-cellular signals involved in its functional recovery from trauma, autoimmune attacks, or neurotoxins. We report here that CXCL12α, also abbreviated as stromal-derived factor-1 (SDF-1), is produced specifically by perisynaptic Schwann cells following motor axon terminal degeneration induced by α-latrotoxin. CXCL12α acts via binding to the neuronal CXCR4 receptor. A CXCL12α-neutralizing antibody or a specific CXCR4 inhibitor strongly delays recovery from motor neuron degeneration in vivo Recombinant CXCL12α in vivo accelerates neurotransmission rescue upon damage and very effectively stimulates the axon growth of spinal cord motor neurons in vitro These findings indicate that the CXCL12α-CXCR4 axis plays an important role in the regeneration of the neuromuscular junction after motor axon injury. The present results have important implications in the effort to find therapeutics and protocols to improve recovery of function after different forms of motor axon terminal damage.

The teneurin C-terminal domain possesses nuclease activity and is apoptogenic

Teneurins are type 2 transmembrane proteins expressed by developing neurons during periods of synaptogenesis and apoptosis. Neurons expressing teneurin-1 synapse with other teneurin-1-expressing neurons, and neurons expressing teneurin-2 synapse with other teneurin-2-expressing neurons. Knockdowns and mutations of teneurins lead to abnormal neuronal connections, but the mechanisms underlying teneurin action remain unknown. Teneurins appear to have evolved via horizontal gene transfer from prokaryotic proteins involved in bacterial self-recognition. The bacterial teneurin-like proteins contain a cytotoxic C-terminal domain that is encapsulated in a tyrosine-aspartic acid repeat barrel. Teneurins are likely to be organized in the same way, but it is unclear if the C-terminal domains of teneurins have cytotoxic properties. Here we show that expression of teneurin C-terminal domains or the addition of purified teneurin C-terminal domains leads to an increase in apoptosis in vitro. The C-terminal domains of teneurins are most similar to bacterial nucleases, and purified C-terminal domains of teneurins linearize pcDNA3 and hydrolyze mitochondrial DNA. We hypothesize that yet to be identified stimuli lead to the release of the encapsulated teneurin C-terminal domain into the intersynaptic region, resulting in programmed cell death or the disruption of mitochondrial DNA and the subsequent pruning of inappropriate contacts.

Summary: Teneurins are transmembrane proteins found in the developing nervous system that are related to bacterial toxins. Teneurins also have cytotoxic properties that may help regulate apoptosis or pruning.

Animal models for studying motor axon terminal paralysis and recovery

An extraordinary property of the peripheral nervous system is that nerve terminals can regenerate after damage caused by different physical, chemical, or biological pathogens. Regeneration is the result of a complex and ill-known interplay among the nerve, the glia, the muscle, the basal lamina and, in some cases, the immune system. This phenomenon has been studied using different injury models mainly in rodents, particularly in mice, where a lesion can be produced in a chosen anatomical area. These approaches differ significantly among them for the nature of the lesion and the final outcomes. We have reviewed here the most common experimental models employed to induce motor axon injury, the relative advantages and drawbacks, and the principal read-outs used to monitor the regenerative process. Recently introduced tools for inducing reversible damage to the motor axon terminal that overcome some of the drawbacks of the more classical approaches are also discussed. Animal models have provided precious information about the cellular components involved in the regenerative process and on its electrophysiological features. Methods and tools made available recently allow one to identify and study molecules that are involved in the crosstalk among the components of the endplate. The time-course of the intercellular signaling and of the intracellular pathways activated will draw a picture of the entire process of regeneration as seen from a privileged anatomical site of observation. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.

Antivenom Efficacy in Neutralizing Histopathological Complications Following Latrodectus dahli Envenomation

BACKGROUND

Nowadays use of specific antivenin for latrodectism is considered as the most effective treatment in the world. This study was undertaken to investigate the efficacy of specific antivenom against histopathological complications caused by Latrodectus dahli venom on liver, heart and kidneys tissues within 72h.

METHODS

Two groups were selected, each one contained 6 male New Zealand rabbits weighing 2±0.5kg. The animals were anesthetized with 0.5ml ketamine and 0.5ml xylazine by intramuscular route. The L. dahli venom (0.5mg/kg) was injected subcutaneously to both the groups. The second group of rabbits 24h after the venom injection received specific antivenom by intravenous route. Seventy-two hours after the venom and antivenom injections, the rabbits were dissected to obtain heart, liver and kidney tissues. The tissues were stained by hematoxylin and eosin stains and histopathological studies were examined by optical microscope.

RESULTS

In group one, the venom induced myocytolysis, myocarditis, coagulation necrosis in the heart tissue and the liver tissue showed central vein congestion, congested vessels, dilated sinusoids and inflammation. However, no significant histopathological complications were observed in kidney tissues. In the second group, antivenom injection greatly prevented escalation of the complications on foresaid tissues.

CONCLUSION

Latrodectus dahli venom induces histopathological complications on vital organs. Specific antivenom injection, 24h after the venom injection, could protect the tissues from incidence and intensification of histopathological complications. Future studies in human beings should be conducted to assess the protection against the specific-Latrodectus antivenin.

Structure of purotoxin-2 from wolf spider: modular design and membrane-assisted mode of action in arachnid toxins

Traditionally, arachnid venoms are known to contain two particularly important groups of peptide toxins. One is disulfide-rich neurotoxins with a predominance of β-structure that specifically target protein receptors in neurons or muscle cells. The other is linear cationic cytotoxins that form amphiphilic α-helices and exhibit rather non-specific membrane-damaging activity. In the present paper, we describe the first 3D structure of a modular arachnid toxin, purotoxin-2 (PT2) from the wolf spider Alopecosa marikovskyi (Lycosidae), studied by NMR spectroscopy. PT2 is composed of an N-terminal inhibitor cystine knot (ICK, or knottin) β-structural domain and a C-terminal linear cationic domain. In aqueous solution, the C-terminal fragment is hyper-flexible, whereas the knottin domain is very rigid. In membrane-mimicking environment, the C-terminal domain assumes a stable amphipathic α-helix. This helix effectively tethers the toxin to membranes and serves as a membrane-access and membrane-anchoring device. Sequence analysis reveals that the knottin + α-helix architecture is quite widespread among arachnid toxins, and PT2 is therefore the founding member of a large family of polypeptides with similar structure motifs. Toxins from this family target different membrane receptors such as P2X in the case of PT2 and calcium channels, but their mechanism of action through membrane access may be strikingly similar.

ATP Released by Injured Neurons Activates Schwann Cells

Injured nerve terminals of neuromuscular junctions (NMJs) can regenerate. This remarkable and complex response is governed by molecular signals that are exchanged among the cellular components of this synapse: motor axon nerve terminal (MAT), perisynaptic Schwann cells (PSCs), and muscle fiber. The nature of signals that govern MAT regeneration is ill-known. In the present study the spider toxin α-latrotoxin has been used as tool to investigate the mechanisms underlying peripheral neuroregeneration. Indeed this neurotoxin induces an acute, specific, localized and fully reversible damage of the presynaptic nerve terminal, and its action mimics the cascade of events that leads to nerve terminal degeneration in injured patients and in many neurodegenerative conditions. Here we provide evidence of an early release by degenerating neurons of adenosine triphosphate as alarm messenger, that contributes to the activation of a series of intracellular pathways within Schwann cells that are crucial for nerve regeneration: Ca(2+), cAMP, ERK1/2, and CREB. These results contribute to define the cross-talk taking place among degenerating nerve terminals and PSCs, involved in the functional recovery of the NMJ.

Specific Antivenom Ability in Neutralizing Hepatic and Renal Changes 24 Hours after Latrodectus dahli Envenomation

BACKGROUND

Latrodectism, a syndrome caused by Latrodectus genus, is one of the clinical problems that occur predominantly in north east of Iran. Nowadays antivenom therapy has become the most useful treatment for animal bites; however there is still a controversy about route and time of antivenom administration in spider bite. The aim of the present study was to determine the efficacy of specific antivenom in neutralizing hepatic and renal symptoms 24 h after Latrodectus dahli envenomation.

METHODS

We selected a group of male New Zealand white rabbits, weighing 2±0.3 kg. The L. dahli venom (0.5 mg/kg) was injected subcutaneously. Specific antivenom (2.5 ml, I.V) was injected 24 h following venom injection. Blood sampling was performed before and 24 h after venom injection, as well within 24, 48 and 72 h after antivenom administration. Serum levels of (aspartate amino transferase (AST) alanine amino transferase (ALT), alkaline phosphatase (ALP), urea, bilirubin, creatinine and albumin were determined in all the sam.

RESULTS

Latrodectus dahli venom caused significant increase (P< 0.05) in all foresaid serum parameters. Antivenom reversed the AST, ALP, creatinine, urea and bilirubin to normal levels, but failed about ALT level, also non-significant decrease was observed in albumin levels.

CONCLUSION

Antivenom administration 24 h after venom injection can greatly reverse symptoms caused by venom. Future studies in human beings should be conducted to assess the protection against the specific-Latrodectus anti-venom.

Snake and Spider Toxins Induce a Rapid Recovery of Function of Botulinum Neurotoxin Paralysed Neuromuscular Junction

Botulinum neurotoxins (BoNTs) and some animal neurotoxins (β-Bungarotoxin, β-Btx, from elapid snakes and α-Latrotoxin, α-Ltx, from black widow spiders) are pre-synaptic neurotoxins that paralyse motor axon terminals with similar clinical outcomes in patients. However, their mechanism of action is different, leading to a largely-different duration of neuromuscular junction (NMJ) blockade. BoNTs induce a long-lasting paralysis without nerve terminal degeneration acting via proteolytic cleavage of SNARE proteins, whereas animal neurotoxins cause an acute and complete degeneration of motor axon terminals, followed by a rapid recovery. In this study, the injection of animal neurotoxins in mice muscles previously paralyzed by BoNT/A or /B accelerates the recovery of neurotransmission, as assessed by electrophysiology and morphological analysis. This result provides a proof of principle that, by causing the complete degeneration, reabsorption, and regeneration of a paralysed nerve terminal, one could favour the recovery of function of a biochemically- or genetically-altered motor axon terminal. These observations might be relevant to dying-back neuropathies, where pathological changes first occur at the neuromuscular junction and then progress proximally toward the cell body.

Recent Advances in Research on Widow Spider Venoms and Toxins

Widow spiders have received much attention due to the frequently reported human and animal injures caused by them. Elucidation of the molecular composition and action mechanism of the venoms and toxins has vast implications in the treatment of latrodectism and in the neurobiology and pharmaceutical research. In recent years, the studies of the widow spider venoms and the venom toxins, particularly the α-latrotoxin, have achieved many new advances; however, the mechanism of action of the venom toxins has not been completely clear. The widow spider is different from many other venomous animals in that it has toxic components not only in the venom glands but also in other parts of the adult spider body, newborn spiderlings, and even the eggs. More recently, the molecular basis for the toxicity outside the venom glands has been systematically investigated, with four proteinaceous toxic components being purified and preliminarily characterized, which has expanded our understanding of the widow spider toxins. This review presents a glance at the recent advances in the study on the venoms and toxins from the Latrodectus species.

The Rise and Fall of an Evolutionary Innovation: Contrasting Strategies of Venom Evolution in Ancient and Young Animals

Animal venoms are theorized to evolve under the significant influence of positive Darwinian selection in a chemical arms race scenario, where the evolution of venom resistance in prey and the invention of potent venom in the secreting animal exert reciprocal selection pressures. Venom research to date has mainly focused on evolutionarily younger lineages, such as snakes and cone snails, while mostly neglecting ancient clades (e.g., cnidarians, coleoids, spiders and centipedes). By examining genome, venom-gland transcriptome and sequences from the public repositories, we report the molecular evolutionary regimes of several centipede and spider toxin families, which surprisingly accumulated low-levels of sequence variations, despite their long evolutionary histories. Molecular evolutionary assessment of over 3500 nucleotide sequences from 85 toxin families spanning the breadth of the animal kingdom has unraveled a contrasting evolutionary strategy employed by ancient and evolutionarily young clades. We show that the venoms of ancient lineages remarkably evolve under the heavy constraints of negative selection, while toxin families in lineages that originated relatively recently rapidly diversify under the influence of positive selection. We propose that animal venoms mostly employ a ‘two-speed’ mode of evolution, where the major influence of diversifying selection accompanies the earlier stages of ecological specialization (e.g., diet and range expansion) in the evolutionary history of the species–the period of expansion, resulting in the rapid diversification of the venom arsenal, followed by longer periods of purifying selection that preserve the potent toxin pharmacopeia–the period of purification and fixation. However, species in the period of purification may re-enter the period of expansion upon experiencing a major shift in ecology or environment. Thus, we highlight for the first time the significant roles of purifying and episodic selections in shaping animal venoms.

While the influence of positive selection in diversifying animal venoms is widely recognized, the role of purifying selection that conserves the amino acid sequence of venom components such as peptide toxins has never been considered. In addition to unraveling the unique strategies of evolution of toxin gene families in centipedes and spiders, which are amongst the first terrestrial venomous lineages, we highlight the significant role of purifying selection in shaping the composition of animal venoms. Analysis of numerous toxin families, spanning the breadth of the animal kingdom, has revealed a striking contrast between the evolution of venom in ancient and evolutionarily young animal groups. Our findings enable the postulation of a new theory of venom evolution. The proposed ‘two-speed’ mode of evolution of venom captures the fascinating evolutionary history and the dynamics of this complex biochemical cocktail.

Transient reverse takotsubo cardiomyopathy following a spider bite in Greece: a case report

Black widow spider is endemic in the Mediterranean area and although envenomations are rare, may occasionally lead to death. We present a case of a 64-year-old female developing a rare variant of takotsubo, stress-induced, cardiomyopathy after a spider bite. This resulted in acute heart failure within 24  hours of the bite. With medical treatment and supportive care, the patient's clinical condition improved. Reverse takotsubo cardiomyopathy was diagnosed by echocardiography, which was transient. Clinical and echocardiographic findings have been completely resolved on follow-up 46 days later. Reverse takotsubo cardiomyopathy has not been yet described following a spider bite. Doctors in the emergency department of endemic countries should be familiar with this potential complication.

Mitochondrial alarmins released by degenerating motor axon terminals activate perisynaptic Schwann cells

An acute and highly reproducible motor axon terminal degeneration followed by complete regeneration is induced by some animal presynaptic neurotoxins, representing an appropriate and controlled system to dissect the molecular mechanisms underlying degeneration and regeneration of peripheral nerve terminals. We have previously shown that nerve terminals exposed to spider or snake presynaptic neurotoxins degenerate as a result of calcium overload and mitochondrial failure. Here we show that toxin-treated primary neurons release signaling molecules derived from mitochondria: hydrogen peroxide, mitochondrial DNA, and cytochrome c. These molecules activate isolated primary Schwann cells, Schwann cells cocultured with neurons and at neuromuscular junction in vivo through the MAPK pathway. We propose that this inter- and intracellular signaling is involved in triggering the regeneration of peripheral nerve terminals affected by other forms of neurodegenerative diseases.

Physiological and biochemical characterization of egg extract of black widow spiders to uncover molecular basis of egg toxicity

Background

Black widow spider (L. tredecimguttatus) has toxic components not only in the venomous glands, but also in other parts of the body and its eggs. It is biologically important to investigate the molecular basis of the egg toxicity.

Results

In the present work, an aqueous extract was prepared from the eggs of the spider and characterized using multiple physiological and biochemical strategies. Gel electrophoresis and mass spectrometry demonstrated that the eggs are rich in high-molecular-mass proteins and the peptides below 5 kDa. The lyophilized extract of the eggs had a protein content of 34.22% and was shown to have a strong toxicity towards mammals and insects. When applied at a concentration of 0.25 mg/mL, the extract could completely block the neuromuscular transmission in mouse isolated phrenic nerve-hemidiaphragm preparations within 12.0 ± 1.5 min. Using whole-cell patch-clamp technique, the egg extract was demonstrated to be able to inhibit the voltage-activated Na⁺, K⁺ and Ca²⁺ currents in rat DRG neurons. In addition, the extract displayed activities of multiple hydrolases. Finally, the molecular basis of the egg toxicity was discussed.

Conclusions

The eggs of black widow spiders are rich in proteinous compounds particularly the high-molecular-mass proteins with different types of biological activity The neurotoxic and other active compounds in the eggs are believed to play important roles in the eggs’ toxic actions.

Different transporter systems regulate extracellular GABA from vesicular and non-vesicular sources

Tonic GABA type A (GABA_A) conductance is a key factor regulating neuronal excitability and computation in neuronal networks. The magnitude of the tonic GABA_A conductance depends on the concentration of ambient GABA originating from vesicular and non-vesicular sources and is tightly regulated by GABA uptake. Here we show that the transport system regulating ambient GABA responsible for tonic GABA_A conductances in hippocampal CA1 interneurons depends on its source. In mice, GABA from vesicular sources is regulated by mouse GABA transporter 1 (mGAT1), while that from non-vesicular sources by mouse GABA transporters 3/4 (mGAT3/4). This finding suggests that the two transporter systems do not just provide backup for each other, but regulate distinct signaling pathways. This allows individual tuning of the two signaling systems and indicates that drugs designed to act at specific transporters will have distinct therapeutic actions.

MKP3 eliminates depolarization-dependent neurotransmitter release through downregulation of L-type calcium channel Cav1.2 expression

Release of neurotransmitters is a fundamental and regulated process that is essential for normal brain functioning. Regulation of this process is potentially important for any neuronal process, and disruption of the release process may contribute to the pathophysiology associated with psychiatric diseases. In this work it is shown that expression of the negative regulator of mitogen-activated protein kinase (MAPK) signaling the MAPK phosphatase MKP3/DUSP6 eliminates depolarization-dependent release of dopamine in rat PC12 cells. Pharmacologic interventions with latrotroxin (LTX) or A23187, which make the cells permeable to calcium, reestablish the dopamine release. Calcium imaging also reveals that calcium influx is impaired in MKP3-expressing cells. Because acute pharmacologic inhibition of MAPKs has no effect on dopamine release in naïve PC12 cells, the MKP3-mediated elimination of neurotransmitter release must be caused by a long-term process, such as changes in gene expression. In support of this the expression of the L-type calcium channel cav1.2 alpha subunit (Cacna1c) is decreased in MKP3-expressing PC12 cells. With the reintroduction of cav1.2 expression, neurotransmitter release is restored in the MKP3-expressing PC12 cells. Thus, MKP3 expression reduces neurotransmitter release by decreasing the expression of cav1.2. Because MKP3 is increased when neuronal activity is elevated, this process could play a role in regulating neurotransmitter homeostasis.

Calpains participate in nerve terminal degeneration induced by spider and snake presynaptic neurotoxins

α-latrotoxin and snake presynaptic phospholipases A2 neurotoxins target the presynaptic membrane of axon terminals of the neuromuscular junction causing paralysis. These neurotoxins display different biochemical activities, but similarly alter the presynaptic membrane permeability causing Ca(2+) overload within the nerve terminals, which in turn induces nerve degeneration. Using different methods, here we show that the calcium-activated proteases calpains are involved in the cytoskeletal rearrangements that we have previously documented in neurons exposed to α-latrotoxin or to snake presynaptic phospholipases A2 neurotoxins. These results indicate that calpains, activated by the massive calcium influx from the extracellular medium, target fundamental components of neuronal cytoskeleton such as spectrin and neurofilaments, whose cleavage is functional to the ensuing nerve terminal fragmentation.

Spider-venom peptides as bioinsecticides

Over 10,000 arthropod species are currently considered to be pest organisms. They are estimated to contribute to the destruction of ~14% of the world's annual crop production and transmit many pathogens. Presently, arthropod pests of agricultural and health significance are controlled predominantly through the use of chemical insecticides. Unfortunately, the widespread use of these agrochemicals has resulted in genetic selection pressure that has led to the development of insecticide-resistant arthropods, as well as concerns over human health and the environment. Bioinsecticides represent a new generation of insecticides that utilise organisms or their derivatives (e.g., transgenic plants, recombinant baculoviruses, toxin-fusion proteins and peptidomimetics) and show promise as environmentally-friendly alternatives to conventional agrochemicals. Spider-venom peptides are now being investigated as potential sources of bioinsecticides. With an estimated 100,000 species, spiders are one of the most successful arthropod predators. Their venom has proven to be a rich source of hyperstable insecticidal mini-proteins that cause insect paralysis or lethality through the modulation of ion channels, receptors and enzymes. Many newly characterized insecticidal spider toxins target novel sites in insects. Here we review the structure and pharmacology of these toxins and discuss the potential of this vast peptide library for the discovery of novel bioinsecticides.

Alpha-latrotoxin rescues SNAP-25 from BoNT/A-mediated proteolysis in embryonic stem cell-derived neurons

The botulinum neurotoxins (BoNTs) exhibit zinc-dependent proteolytic activity against members of the core synaptic membrane fusion complex, preventing neurotransmitter release and resulting in neuromuscular paralysis. No pharmacologic therapies have been identified that clinically relieve botulinum poisoning. The black widow spider venom α-latrotoxin (LTX) has the potential to attenuate the severity or duration of BoNT-induced paralysis in neurons via the induction of synaptic degeneration and remodeling. The potential for LTX to antagonize botulinum poisoning was evaluated in embryonic stem cell-derived neurons (ESNs), using a novel screening assay designed around the kinetics of BoNT/A activation. Exposure of ESNs to 400 pM LTX for 6.5 or 13 min resulted in the nearly complete restoration of uncleaved SNAP-25 within 48 h, whereas treatment with 60 mM K⁺ had no effect. Time-lapse imaging demonstrated that LTX treatment caused a profound increase in Ca²⁺ influx and evidence of excitotoxicity, though ESNs remained viable 48 h after LTX treatment. This is the first instance of a cell-based treatment that has shown the ability to eliminate BoNT activity. These data suggest that LTX treatment may provide the basis for a new class of therapeutic approach to BoNT intoxication and may contribute to an improved understanding of long-term mechanisms of BoNT intoxication and recovery. They further demonstrate that ESNs are a novel, responsive and biologically relevant model for LTX research and BoNT therapeutic drug discovery.

Prediction of epitopes in closely related proteins using a new algorithm

Latrophilin 1 (presynaptic receptor) binds α-latrotoxin from black widow spider venom and regulates neurotransmitter release from nerve endings. The study of the mechanism of action of this receptor is impeded by the existence of closely related latrophilins 2 and 3. A profile of differences detecting the most differing and identical sites in several proteins was developed in order to obtain highly specific antibodies for differentiation between isoforms of related proteins. In addition, we used an algorithm for prediction of immunogenic sites of the protein, based on the basic vector method. The peptides selected using this algorithm were used for immunization of animals. The resultant sera exhibited the estimated specificity and high affinity for the corresponding receptor forms.

Screening of human LPHN3 for variants with a potential impact on ADHD susceptibility

Attention deficit hyperactivity disorder (ADHD) is the most common behavioral disorder in childhood, and often has effects detectable into adulthood. Advances in genetic linkage and association analysis have begun to elucidate some of the genetic factors underlying this complex disorder. Recently, we identified LPHN3, a novel ADHD susceptibility gene harbored in 4q, and showed that a LPHN3 common haplotype confers susceptibility to ADHD and predicts effectiveness of stimulant medication. Here we present the mutational analysis of the entire coding region of LPHN3 in a cohort of 139 ADHD subjects and 52 controls from across the USA. We identified 21 variants, of which 14 have been reported and 7 are novel. These include 5 missense, 8 synonymous, and 8 intronic changes. Interestingly, neither susceptibility nor protective haplotype alleles are associated with obviously significant coding region changes, or canonical splice site alterations, suggesting that non-coding variations determining the quantity and/or quality of LPHN3 isoforms are the likely contributors to this common behavioral disorder.

From the black widow spider to human behavior: Latrophilins, a relatively unknown class of G protein-coupled receptors, are implicated in psychiatric disorders

The findings of a recent study associate LPHN3, a member of the latrophilin family, with an increased risk of developing attention deficit/hyperactivity disorder (ADHD), the most common psychiatric disorder in childhood and adolescence. Latrophilins comprise a new family of G protein-coupled receptors of unknown native physiological function that mediate the neurotoxic effects of α-latrotoxin, a potent toxin found in black widow spider venom. This receptor-toxin interaction has helped to elucidate the mechanistic aspects of neurotransmitter and hormone release in vertebrates. Such unprecedented discovery points to a new direction in the assessment of ADHD and suggest that further study of this receptor family may provide novel insights into the etiology and treatment of ADHD and other related psychiatric conditions.

Complex and multidimensional lipid raft alterations in a murine model of Alzheimer's disease

Various animal models of Alzheimer's disease (AD) have been created to assist our appreciation of AD pathophysiology, as well as aid development of novel therapeutic strategies. Despite the discovery of mutated proteins that predict the development of AD, there are likely to be many other proteins also involved in this disorder. Complex physiological processes are mediated by coherent interactions of clusters of functionally related proteins. Synaptic dysfunction is one of the hallmarks of AD. Synaptic proteins are organized into multiprotein complexes in high-density membrane structures, known as lipid rafts. These microdomains enable coherent clustering of synergistic signaling proteins. We have used mass analytical techniques and multiple bioinformatic approaches to better appreciate the intricate interactions of these multifunctional proteins in the 3xTgAD murine model of AD. Our results show that there are significant alterations in numerous receptor/cell signaling proteins in cortical lipid rafts isolated from 3xTgAD mice.