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The emperor scorpion, Pandinus imperator, is a species of scorpion native to rainforests and savannas in West Africa. It is one of the largest scorpions in the world and lives for 6–8 years. Its body is black, but like other scorpions it glows pastel green or blue under ultraviolet light. It is a popular species in the pet trade, and is protected by CITES to prevent over-collecting that might impact the species survival.
Ryanodine receptors form a class of intracellular calcium channels in various forms of excitable animal tissue like muscles and neurons. There are three major isoforms of the ryanodine receptor, which are found in different tissues and participate in different signaling pathways involving calcium release from intracellular organelles. The RYR2 ryanodine receptor isoform is the major cellular mediator of calcium-induced calcium release (CICR) in animal cells.
Tityustoxin is a toxin found in the venom of scorpions from the subfamily Tityinae. By binding to voltage-dependent sodium ion channels and potassium channels, they cause sialorrhea, lacrimation and rhinorrhea.
Margatoxin (MgTX) is a peptide that selectively inhibits Kv1.3 voltage-dependent potassium channels. It is found in the venom of Centruroides margaritatus, also known as the Central American Bark Scorpion. Margatoxin was first discovered in 1993. It was purified from scorpion venom and its amino acid sequence was determined.
A calcium spark is the microscopic release of calcium (Ca2+) from a store known as the sarcoplasmic reticulum (SR), located within muscle cells. This release occurs through an ion channel within the membrane of the SR, known as a ryanodine receptor (RyR), which opens upon activation. This process is important as it helps to maintain Ca2+ concentration within the cell. It also initiates muscle contraction in skeletal and cardiac muscles and muscle relaxation in smooth muscles. Ca2+ sparks are important in physiology as they show how Ca2+ can be used at a subcellular level, to signal both local changes, known as local control, as well as whole cell changes.
Cobatoxin is a toxin present in the venom of the scorpion Centruroides noxius. It blocks two potassium channel subtypes; voltage-gated and calcium-activated channels.
BeKm-1 is a toxin from the Central Asian scorpion Buthus eupeus. BeKm-1 acts by selectively inhibiting the human Ether-à-go-go Related Gene (hERG) channels, which are voltage gated potassium ion channels.
Bukatoxin is an α-scorpion toxin found in the venom of the Chinese scorpion Buthus martensi Karsch. By blocking the inactivation of sodium ion channels, α-scorpion toxins prolong action potentials.
Helothermine is a toxin from the venom of the Mexican beaded lizard Heloderma horridum horridum. Helothermine inhibits ryanodine receptors, calcium channels and potassium channels. Helothermine can cause lethargy, partial paralysis of rear limbs and lowering of the body temperature.
Hanatoxin is a toxin found in the venom of the Grammostola spatulata tarantula. The toxin is mostly known for inhibiting the activation of voltage-gated potassium channels, most specifically Kv4.2 and Kv2.1, by raising its activation threshold.
Huwentoxins (HWTX) are a group of neurotoxic peptides found in the venom of the Chinese bird spider Haplopelma schmidti. The species was formerly known as Haplopelma huwenum, Ornithoctonus huwena and Selenocosmia huwena. While structural similarity can be found among several of these toxins, HWTX as a group possess high functional diversity.
Pandinotoxins are toxins from the venom of the emperor scorpion Pandinus imperator. They are selective blockers of voltage-gated potassium channels
Hadrucalcin is a peptide toxin from the venom of the scorpion Hadrurus gertschi. Hadrucalcin modifies the Ryanodine receptor channels RyR1 and RyR2, found in the sarcoplasmic reticulum, to a long-lasting subconductance state, thus inducing the release of calcium from the sarcoplasmic reticulum.
The ryanodine-inositol 1,4,5-triphosphate receptor Ca2+ channel (RIR-CaC) family includes Ryanodine receptors and Inositol trisphosphate receptors. Members of this family are large proteins, some exceeding 5000 amino acyl residues in length. This family belongs to the Voltage-gated ion channel (VIC) superfamily. Ry receptors occur primarily in muscle cell sarcoplasmic reticular (SR) membranes, and IP3 receptors occur primarily in brain cell endoplasmic reticular (ER) membranes where they effect release of Ca2+ into the cytoplasm upon activation (opening) of the channel. They are redox sensors, possibly providing a partial explanation for how they control cytoplasmic Ca2+. Ry receptors have been identified in heart mitochondria where they provide the main pathway for Ca2+ entry. Sun et al. (2011) have demonstrated oxygen-coupled redox regulation of the skeletal muscle ryanodine receptor-Ca2+ release channel (RyR1;TC# 1.A.3.1.2) by NADPH oxidase 4.
Pi4 is a short toxin from the scorpion Pandinus imperator that blocks specific potassium channels.
Noxiustoxin (NTX) is a toxin from the venom of the Mexican scorpion Centruroides noxius Hoffmann which block voltage-dependent potassium channels and calcium-activated potassium channels.
Pi5 toxin is a peptide found in the venom of the African emperor scorpion Pandinus imperator. Pi5 inhibits human Kv1.2 and Kv1.3 channels as well as Drosophila Shaker B potassium channels.
Vejocalcin (VjCa, also called Vejocalcine) is a toxin from the venom of the Mexican scorpion Vaejovis mexicanus. Vejocalcin is a member of the calcin family of toxins. It acts as a cell-penetrating peptide (CPP); it binds with high affinity and specificity to skeletal ryanodine receptor 1 (RYR1) of the sarcoplasmic reticulum, thereby triggering calcium release from intracellular Ca2+ stores.
Intrepicalcin (ViCaTx1) is a short peptide toxin found in the venom of scorpion Vaejovis intrepidus. It is one of a group of short, basic peptides called calcins, which bind to ryanodine receptors (RyRs) and thereby trigger calcium release from the sarcoplasmic reticulum.
LmαTX5 is an α-scorpion toxin which inhibits the fast inactivation of voltage-gated sodium channels. It has been identified through transcriptome analysis of the venom gland of Lychas mucronatus, also known as the Chinese swimming scorpion – a scorpion species which is widely distributed in Southeast Asia.
References
- 1 2 Valdivia, Hector H.; Kirby, Mark S.; Lederer, W. Jonathan; Coronado, Roberto (1992). "Scorpion Toxins Targeted Against the Sarcoplasmic Reticulum Ca2+- Release Channel of Skeletal and Cardiac Muscle". Proceedings of the National Academy of Sciences. 89 (24): 12185–9. Bibcode:1992PNAS...8912185V. doi: 10.1073/pnas.89.24.12185 . JSTOR 2360882. PMC 50723 . PMID 1334561.
- ↑ Franzini-Armstrong, C; Protasi, F (1997). "Ryanodine receptors of striated muscles: A complex channel capable of multiple interactions". Physiological Reviews. 77 (3): 699–729. doi:10.1152/physrev.1997.77.3.699. PMID 9234963.
- 1 2 Simeoni, Ilenia; Rossi, Daniela; Zhu, Xinsheng; Garcı́a, Jesus; Valdivia, Hector H.; Sorrentino, Vincenzo (2001). "Imperatoxin A (IpTxa) from Pandinus imperator stimulates [3H]ryanodine binding to RyR3 channels". FEBS Letters. 508 (1): 5–10. doi:10.1016/S0014-5793(01)03013-7. PMID 11707258. S2CID 24194429.
- ↑ Zamudio, F. Z.; Conde, R; Arévalo, C; Becerril, B; Martin, BM; Valdivia, HH; Possani, LD (1997). "The Mechanism of Inhibition of Ryanodine Receptor Channels by Imperatoxin I, a Heterodimeric Protein from the Scorpion Pandinus imperator". Journal of Biological Chemistry. 272 (18): 11886–94. doi: 10.1074/jbc.272.18.11886 . PMID 9115249.
- ↑ Santonastasi, Marco; Wehrens, Xander H T (2007). "Ryanodine receptors as pharmacological targets for heart disease". Acta Pharmacologica Sinica. 28 (7): 937–44. doi: 10.1111/j.1745-7254.2007.00582.x . PMID 17588328.
