Acid-sensing ion channel (ASIC) structure and function: insights from spider, snake and sea anemone venoms

Acid-sensing ion channels (ASICs) are proton-activated cation channels that are expressed in a variety of neuronal and non-neuronal tissues. As proton-gated channels, they have been implicated in many pathophysiological conditions where pH is perturbed. Venom derived compounds represent the most potent and selective modulators of ASICs described to date, and thus have been invaluable as pharmacological tools to study ASIC structure, function, and biological roles. There are now ten ASIC modulators described from animal venoms, with those from snakes and spiders favouring ASIC1, while the sea anemones preferentially target ASIC3. Some modulators, such as the prototypical ASIC1 modulator PcTx1 have been studied in great detail, while some of the newer members of the club remain largely unstudied. Here we review the current state of knowledge on venom derived ASIC modulators, with a particular focus on their molecular interaction with ASICs, what they have taught us about channel structure, and what they might still reveal about ASIC function and pathophysiological roles

Discovery and molecular interaction studies of a highly stable, tarantula peptide modulator of acid-sensing ion channel 1

Acute pharmacological inhibition of acid-sensing ion channel 1a (ASIC1a) is efficacious in rodent models in alleviating symptoms of neurological diseases such as stroke and multiple sclerosis. Thus, ASIC1a is a promising therapeutic target and selective ligands that modulate it are invaluable research tools and potential therapeutic leads. Spider venoms have provided an abundance of voltage-gated ion channel modulators, however, only one ASIC modulator (PcTx1) has so far been isolated from this source. Here we report the discovery, characterization, and chemical stability of a second spider venom peptide that potently modulates ASIC1a and ASIC1b, and investigate the molecular basis for its subtype selectivity. π-TRTX-Hm3a (Hm3a) is a 37-amino acid peptide isolated from Togo starburst tarantula (Heteroscodra maculata) venom with five amino acid substitutions compared to PcTx1, and is also three residues shorter at the C-terminus. Hm3a pH-dependently inhibited ASIC1a with an IC of 1–2 nM and potentiated ASIC1b with an EC of 46.5 nM, similar to PcTx1. Using ASIC1a to ASIC1b point mutants in rat ASIC1a revealed that Glu177 and Arg175 in the palm region opposite α-helix 5 play an important role in the Hm3a-ASIC1 interaction and contribute to the subtype-dependent effects of the peptide. Despite its high sequence similarity with PcTx1, Hm3a showed higher levels of stability over 48 h. Overall, Hm3a represents a potent, highly stable tool for the study of ASICs and will be particularly useful when stability in biological fluids is required, for example in long term in vitro cell-based assays and in vivo experiments. This article is part of the Special Issue entitled ‘Venom-derived Peptides as Pharmacological Tools.

Pain-causing stinging nettle toxins target TMEM233 to modulate NaV1.7 function

Voltage-gated sodium (NaV) channels are critical regulators of neuronal excitability and are targeted by many toxins that directly interact with the pore-forming α subunit, typically via extracellular loops of the voltage-sensing domains, or residues forming part of the pore domain. Excelsatoxin A (ExTxA), a pain-causing knottin peptide from the Australian stinging tree Dendrocnide excelsa, is the first reported plant-derived NaV channel modulating peptide toxin. Here we show that TMEM233, a member of the dispanin family of transmembrane proteins expressed in sensory neurons, is essential for pharmacological activity of ExTxA at NaV channels, and that co-expression of TMEM233 modulates the gating properties of NaV1.7. These findings identify TMEM233 as a previously unknown NaV1.7-interacting protein, position TMEM233 and the dispanins as accessory proteins that are indispensable for toxin-mediated effects on NaV channel gating, and provide important insights into the function of NaV channels in sensory neurons

Mutations in the voltage-gated potassium channel gene KCNH1 cause Temple-Baraitser syndrome and epilepsy (vol 47, pg 73, 2015)

"Mutations in the voltage-gated potassium channel gene KCNH1 cause Temple-Baraitser syndrome and epilepsy" published in Nature Genetics (2015), volume 47, pp.73-77

Discovery and modulation of acid-sensing ion channel modulating venom peptides

Pengarsipan merupakan hal yang perlu diperhatikan oleh instansi/organisasi sehubungannya dengan kegiatan administrasi. Tujuan penulisan laporan Proyek Akhir ini adalah untuk mengetahui pengelolaan kearsipan pada Dinas Pekerjaan Umum Bina Marga Kabupaten Sidoarjo. Metode yang digunakan dalam penulisan ini laporan Proyek Akhir adalah menggunakan observasi, interview dan studi literatur. Hasil observasi dan interview didapatkan bahwa pengelolaan kearsipan di Dinas Pekerjaan Umum Bina Marga Kabupaten Sidoarjo kurang baik, karena sistem pengarsipan disana masih menggunakan sistem manual dan belum tertata dengan rapi, sehingga dapat mengalami kesulitan dalam penyimpanan surat-surat dan penemuan kembali surat-surat di bagian Bagian Umum dan Kepegawaian Dinas Pekerjaan Umum Bina Marga. Dari permasalahan diatas, maka penulis membuat sistem pengarsipan secara elektronik untuk memperbaiki sistem yang telah ada sebelumnya. Pengembangan sistem pengarsipan secara elektronik diharapkan dapat meningkatkan kinerja pegawai

Defining the role of post-synaptic α-neurotoxins in paralysis due to snake envenoming in humans

Snake venom α-neurotoxins potently inhibit rodent nicotinic acetylcholine receptors (nAChRs), but their activity on human receptors and their role in human paralysis from snakebite remain unclear. We demonstrate that two short-chain α-neurotoxins (SαNTx) functionally inhibit human muscle-type nAChR, but are markedly more reversible than against rat receptors. In contrast, two long-chain α-neurotoxins (LαNTx) show no species differences in potency or reversibility. Mutant studies identified two key residues accounting for this. Proteomic and clinical data suggest that paralysis in human snakebites is not associated with SαNTx, but with LαNTx, such as in cobras. Neuromuscular blockade produced by both subclasses of α-neurotoxins was reversed by antivenom in rat nerve–muscle preparations, supporting its effectiveness in human post-synaptic paralysis

Three Peptide Modulators of the Human Voltage-Gated Sodium Channel 1.7, an Important Analgesic Target, from the Venom of an Australian Tarantula

Voltage-gated sodium (NaV) channels are responsible for propagating action potentials in excitable cells. NaV1.7 plays a crucial role in the human pain signalling pathway and it is an important therapeutic target for treatment of chronic pain. Numerous spider venom peptides have been shown to modulate the activity of NaV channels and these peptides represent a rich source of research tools and therapeutic lead molecules. The aim of this study was to determine the diversity of NaV1.7-active peptides in the venom of an Australian Phlogius sp. tarantula and to characterise their potency and subtype selectivity. We isolated three novel peptides, μ-TRTX-Phlo1a, -Phlo1b and -Phlo2a, that inhibit human NaV1.7 (hNaV1.7). Phlo1a and Phlo1b are 35-residue peptides that differ by one amino acid and belong in NaSpTx family 2. The partial sequence of Phlo2a revealed extensive similarity with ProTx-II from NaSpTx family 3. Phlo1a and Phlo1b inhibit hNaV1.7 with IC50 values of 459 and 360 nM, respectively, with only minor inhibitory activity on rat NaV1.2 and hNaV1.5. Although similarly potent at hNaV1.7 (IC50 333 nM), Phlo2a was less selective, as it also potently inhibited rNaV1.2 and hNaV1.5. All three peptides cause a depolarising shift in the voltage-dependence of hNaV1.7 activation

Animal toxins — Nature's evolutionary-refined toolkit for basic research and drug discovery

Venomous animals have evolved toxins that interfere with specific components of their victim's core physiological systems, thereby causing biological dysfunction that aids in prey capture, defense against predators, or other roles such as intraspecific competition. Many animal lineages evolved venom systems independently, highlighting the success of this strategy. Over the course of evolution, toxins with exceptional specificity and high potency for their intended molecular targets have prevailed, making venoms an invaluable and almost inexhaustible source of bioactive molecules, some of which have found use as pharmacological tools, human therapeutics, and bioinsecticides. Current biomedically-focused research on venoms is directed towards their use in delineating the physiological role of toxin molecular targets such as ion channels and receptors, studying or treating human diseases, targeting vectors of human diseases, and treating microbial and parasitic infections. We provide examples of each of these areas of venom research, highlighting the potential that venom molecules hold for basic research and drug development