SNX-482 ammonium

SNX-482 is usually supplied as the ammonium salt, SNX-482 ammonium. SNX-482 (CAS No.: 203460-30-4) is a 41-amino-acid inhibitory cystine knot (ICK) peptide derived from the venom of the African tarantula (*Hysterocrates gigas*). Its peptide sequence is H-Gly-Val-Asp-Lys-Ala-Gly-Cys-Arg-Tyr-Met-Phe-Gly-Gly-Cys-Ser-Val-Asn-Asp-Asp-Cys-Cys-Pro-Arg-Leu-Gly-Cys-His-Ser-Leu-Phe-Ser-Tyr-Cys-Ala-Trp-Asp-Leu-Thr-Phe-Ser-Asp-OH, and three intramolecular disulfide bonds—Cys7→Cys21, Cys14→Cys26, and Cys20→Cys33—form a stable ICK structure. The primary targets of SNX-482 are the voltage-gated calcium channel CaV2.3 (E/R-type) and the voltage-gated potassium channels Kv4.3 and Kv4.2. By binding to their voltage-sensing domains (VSDs), it antagonizes these channels through gating modification, shifting the voltage dependence of activation toward depolarized potentials, slowing activation/inactivation kinetics, and reducing maximal currents under strong depolarization. It thereby regulates neuronal calcium signaling and the A-type transient outward potassium current (I_A), affects neuronal excitability and neural signal transmission, and may downregulate pathways involving NK1 receptor internalization and c-fos expression associated with neuropathic pain.

At the cellular level, SNX-482 is mainly used in electrophysiological studies of CaV2.3 and Kv4.x channel function in HEK-293 cells stably expressing cloned channels and in models such as acutely isolated mouse substantia nigra dopaminergic neurons, rat posterior pituitary cells, and hippocampal granule cells. In 192C cells expressing human CaV2.3, its IC₅₀ for inhibition of CaV2.3 currents is approximately 30 nM; in rat posterior pituitary cells, its IC₅₀ for CaV2.3 currents is approximately 4 nM. Its IC₅₀ values for A- and B-type calcium channels are >280 nM and ~800 nM, respectively, and its IC₅₀ values for Kv1.1, Kv1.2, and Kv1.4 are all >140 nM, indicating relatively high selectivity for CaV2.3. In HEK-293 cells stably expressing Kv4.3, its IC₅₀ for inhibition of Kv4.3 is <3 nM, with approximately 20-fold greater potency than for CaV2.3; inhibition of Kv4.2 is less potent and requires higher concentrations. Functional studies typically use 30–60 nM for CaV2.3 and 1–10 nM for Kv4.3, whereas studies of Kv4.2 generally require higher concentrations of 60–500 nM to investigate its effects on channel gating mechanisms and neuronal excitability.

In animal experiments, SNX-482 is mainly used as a therapeutic tool compound in disease models to validate causal relationships between CaV2.3/Kv4.3-related pathways and pathological states. In a rat formalin-induced neuropathic pain model, intrathecal administration at 0.5 μg/animal can significantly inhibit NK₁ receptor internalization and c-fos expression in the spinal dorsal horn and reduce formalin-induced nociceptive tail-flick responses, thereby validating its role in alleviating inflammatory/neuropathic pain behaviors by modulating CaV2.3-related signaling and neuronal excitability.

References:

[1] Kimm T, Bean BP. Inhibition of A-type potassium current by the peptide toxin SNX-482. J Neurosci. 2014 Jul 9;34(28):9182-9. doi: 10.1523/JNEUROSCI.0339-14.2014. PMID: 25009251; PMCID: PMC4087201.

[2] Mellado G, Espinoza N, Garate JA, Neely A. Spider Toxin SNX-482 Gating Modifier Spontaneously Partitions in the Membrane Guided by Electrostatic Interactions. Membranes (Basel). 2022 Jun 6;12(6):595. doi: 10.3390/membranes12060595. PMID: 35736302; PMCID: PMC9231009.