Protoxin-I

Last updated

Protoxin-I, also known as ProTx-I, or Beta/omega-theraphotoxin-Tp1a, is a 35-amino-acid peptide neurotoxin extracted from the venom of the tarantula Thrixopelma pruriens . Protoxin-I belongs to the inhibitory cystine knot (ICK) family of peptide toxins, which have been known to potently inhibit voltage-gated ion channels. Protoxin-I selectively blocks low voltage threshold T-type calcium channels, [1] [2] voltage gated sodium channels [3] [4] and the nociceptor cation channel TRPA1. [5] Due to its unique ability to bind to TRPA1, Protoxin-I has been implicated as a valuable pharmacological reagent with potential applications in clinical contexts with regards to pain and inflammation [5]

Contents

Origin

Protoxin-I is a toxin extracted from the venom of the tarantula spider Thrixopelma pruriens , also known as the Peruvian green velvet spider. It is used by the spider to immobilise and catch prey. [6] The primary structure of the mature toxin peptide is homologous to that of Beta/omega-theraphotoxin-Bp1a from the tarantula spider Bumba pulcherrimaklaasi, suggesting a common toxin within the subfamily Theraphosinae . [7]

Structure and active site

Protoxin-I is a peptide possessing a 35 amino acid sequence of Glu-Cys-Arg-Tyr-Trp-Leu-Gly-Gly-Cys-Ser-Ala-Gly-Gln-Thr-Cys-Cys-Lys-His-Leu-Val-Cys-Ser-Arg-Arg-His-Gly-Trp-Cys-Val-Trp-Asp-Gly-Thr-Phe-Ser (see Table 1 for one-letter sequence) with 3 disulphide bonds between Cys2-Cys16, Cys9-Cys21 and Cys15-Cys28. [7] Nuclear Magnetic Resonance Spectroscopy of Protoxin-I revealed two beta strands in the protein structure. [5] Gating-modifier toxins isolated from spider venom all share a conserved molecular structure consisting of a hydrophobic patch, populated by hydrophobic residues, and surrounded by a ring of positively- and negatively charged residues that promote the binding of the peptide to the lipid membrane. [8]

Table 1: Protoxin-I Sequence
15101520253035
ECRYWLGGCSAGQTCCKHLVCSRRHGWCVWDGTFS
Surface profile of Protoxin-I coloured in accordance to residue characteristic: hydrophobic (green), positively charged (blue), negatively charged (red), uncharged (grey). Prototoxin-1 Surface Profile.png
Surface profile of Protoxin-I coloured in accordance to residue characteristic: hydrophobic (green), positively charged (blue), negatively charged (red), uncharged (grey).

By systematically exchanging single amino acids by an alanine, features responsible for Protoxin-I toxicity can be revealed. As such, the replacements R3A, W5A, K17E, L19A, S22A, R23A, W27A, V29A, W30A, D31A, G31A, F34A reduce the toxin's ability to inhibit sodium channels NaV1.2. [5] [7]   Similarly, the replacements L6A, L19A, W27A, V29A, W30A, D31A also reduce its inhibitory effects on NaV1.7 sodium channels. [7] Lastly, the replacements Q13A, L19A, S22A, W30A, F34A, S35A reveal the active sites for Protoxin-I binding to TRPA1 receptors. [5] These loss-of-function replacements primarily represent residues in the hydrophobic patch and positively- and negatively charged rings, further supporting the idea that these regions play an important role in ion channel binding. [8]

Toxicodynamics

Like other gating-modifier spider toxins, Protoxin-I preferentially binds to anionic lipid-containing membranes where it exhibits complex allosteric interactions with ion channel voltage sensor domains. [9] [10] After binding to the lipid membrane, Protoxin-I adopts a shallow position on the anionic membrane with the help of tryptophan residues within the hydrophobic patch, [8] where the positively- and negatively charged rings on the toxin are then able to bind to conserved sequences of hydrophobic and anionic residues on voltage gated ion channels. [11] [12]

Voltage-gated sodium channels

Similar to other gating-modifier toxins of the ICK family, Protoxin-I works by shifting the voltage dependence of activation of voltage-gated sodium channels to more positive potentials. [3] Protoxin-I differs from other ICK toxins as Protoxin-I exhibits little selectivity between sodium channels, and is thus able to potently inhibit TTX-resistant sodium currents in sensory neurons through interaction with the Nav1.8 channel. [3] [4] Protoxin-I has been found to potently bind to NaV1.2, NaV1.6, NaV1.7 and NaV1.8. [3] [7] The pore-forming α subunit of voltage-gated sodium channels consists of 4 homologous domains, each having their own voltage sensor domain. Research has shown that Protoxin-I interacts with the voltage sensor domains of domain II and domain IV, thereby functionally inhibiting the channel. [7] Protoxin-I promiscuity in binding to voltage-gated sodium channels is believed to be because of the high amount of positively charged residues on the peptide surface, which bind to conserved amino acid sequences on the surface of the voltage-sensor domain on sodium channels. [8] This notion is further back by the fact that Protoxin-I binds less potently to NaV1.4 and NaV1.5, which exhibit relatively fewer anionic residues on the voltage sensor domain. [8]

Voltage-Gated T-type calcium channels

Protoxin-I has also been found to shift the voltage dependence of activation of the T-type calcium channels. [1] [3] In particular, Protoxin-I is able to differentiate CaV3.1 channels from other human T-type calcium channels, exhibiting a 160-fold increase in potency over that of CaV3.2, [1] and a 10-fold increase in potency over that of CaV3.3. [2] Protoxin-I shifts the voltage dependence of activation of T-type calcium channels to more positive potentials, without changing its voltage dependence of inactivation. [3] Through the use of chimeric channel proteins, the S3-S4 linker on domain IV of the CaV3.1 channel protein has been identified in having greater sensitivity towards Protoxin-I, suggesting that this domain exhibits specific residues that are susceptible to Protoxin-I binding. [1] [2]

Transient receptor potential ankyrin 1 (TRPA1)

Protoxin was identified to be the first high-affinity peptide TRPA1 antagonist. [5] TRPA1 is a primary nociceptor channel expressed on the plasma membrane of many human and animal cells. NaV1.2 and TRPA1 were found to have partially homologous binding sites by which Protoxin-I binds to these ion channels. These binding surfaces are, similar to that of sodium channels, located on the extracellular loops of the S1-S4 gating domain of the TRPA1 channel. [5]

Therapeutic uses

In vivo testing in mice revealed that intrathecal injection of Protoxin-I reduces the response to formalin in acute pain and inflammation without signs of neurotoxicity. [13]

Modifications to Protoxin-I can induce altered specificity in binding, producing peptides that only bind to either the TRPA1 or NaV1.2 gating mechanism. [5] This may provide a deeper insight into the biophysiological function and mechanisms underlying TRPA1, with potential clinical applications in pain and inflammation treatment. TRPA1 represents the final common pathway for many pronociceptive induced pathophysiological pain, therefore, pain therapy using TRPA1 antagonists can be expected to have applicable pharmacological use [14]

Related Research Articles

<span class="mw-page-title-main">Poneratoxin</span> Paralyzing neurotoxic peptide

Poneratoxin is a paralyzing neurotoxic peptide made by the bullet ant Paraponera clavata. It prevents inactivation of voltage gated sodium channels and therefore blocks synaptic transmission in the central nervous system. Specifically, poneratoxin acts on voltage gated sodium channels in skeletal muscle fibers, causing paralysis, and nociceptive fibers, causing pain. It is rated as a 4 plus on the Schmidt sting pain index, the highest possible rating with that system, and its effects can cause waves of pain up to twelve hours after a single sting. It is additionally being studied for its uses in biological insecticides.

omega-Grammotoxin SIA (ω-grammotoxin SIA) is a protein toxin that inhibits P, Q, and N voltage-gated calcium channels (Ca2+ channels) in neurons.

<span class="mw-page-title-main">Grammotoxin</span>

Grammotoxin is a toxin in the venom of the tarantula Grammostola spatulata. It is a protein toxin that inhibits P-, Q- and N-type voltage-gated calcium channels in neurons. Grammotoxin is also known as omega-grammotoxin SIA.

<span class="mw-page-title-main">Scorpion toxin</span>

Scorpion toxins are proteins found in the venom of scorpions. Their toxic effect may be mammal- or insect-specific and acts by binding with varying degrees of specificity to members of the Voltage-gated ion channel superfamily; specifically, voltage-gated sodium channels, voltage-gated potassium channels, and Transient Receptor Potential (TRP) channels. The result of this action is to activate or inhibit the action of these channels in the nervous and cardiac organ systems. For instance, α-scorpion toxins MeuNaTxα-12 and MeuNaTxα-13 from Mesobuthus eupeus are neurotoxins that target voltage-gated Na+ channels (Navs), inhibiting fast inactivation. In vivo assays of MeuNaTxα-12 and MeuNaTxα-13 effects on mammalian and insect Navs show differential potency. These recombinants exhibit their preferential affinity for mammalian and insect Na+ channels at the α-like toxins' active site, site 3, in order to inactivate the cell membrane depolarization faster[6]. The varying sensitivity of different Navs to MeuNaTxα-12 and MeuNaTxα-13 may be dependent on the substitution of a conserved Valine residue for a Phenylalanine residue at position 1630 of the LD4:S3-S4 subunit or due to various changes in residues in the LD4:S5-S6 subunit of the Navs. Ultimately, these actions can serve the purpose of warding off predators by causing pain or to subdue predators.

<span class="mw-page-title-main">Guangxitoxin</span>

Guangxitoxin, also known as GxTX, is a peptide toxin found in the venom of the tarantula Plesiophrictus guangxiensis. It primarily inhibits outward voltage-gated Kv2.1 potassium channel currents, which are prominently expressed in pancreatic β-cells, thus increasing insulin secretion.

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.

Thrixopelma pruriens, known as the Peruvian green velvet tarantula, is a species of tarantula found in Chile and Perú in South America.

Cangitoxin, also known as CGTX or CGX, is a toxin purified from the venom of the sea anemone Bunodosoma cangicum, which most likely acts by prolonging the inactivation of voltage-gated sodium channels.

CgNa is a peptide toxin isolated from the sea anemone Condylactis gigantea. It causes an increased action potential duration by slowing down the inactivation of tetrodotoxin-sensitive sodium channels.

GTx1-15 is a toxin from the Chilean tarantula venom that acts as both a voltage-gated calcium channel blocker and a voltage-gated sodium channel blocker.

Beta-mammal toxin Cn2, also known as Cn2 toxin, is a single chain β-scorpion neurotoxic peptide and the primary toxin in the venom of the Centruroides noxius Hoffmann scorpion. The toxin specifically targets mammalian Nav1.6 voltage-gated sodium channels (VGSC).

<span class="mw-page-title-main">Wasabi receptor toxin</span>

Wasabi receptor toxin (WaTx) is the active component of the venom of the Australian black rock scorpion Urodacus manicatus. WaTx targets TRPA1, also known as the wasabi receptor or irritant receptor. WaTx is a cell-penetrating toxin that stabilizes the TRPA1 channel open state while reducing its Ca2+-permeability, thereby eliciting pain and pain hypersensitivity without the neurogenic inflammation that typically occurs in other animal toxins.

Protoxin-II, also known as ProTx-II, PT-II or β/ω-TRTX-Tp2a, is a neurotoxin that inhibits certain voltage-gated calcium and voltage-gated sodium channels. This toxin is a 30-residue disulfide-rich peptide that has unusually high affinity and selectivity toward the human Nav1.7. channel.

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.

μ-THTX-Cl6a, also known as Cl6a, is a 33-residue peptide toxin extracted from the venom of the spider Cyriopagopus longipes. The toxin acts as an inhibitor of the tetrodotoxin-sensitive (TTX-S) voltage-gated sodium channel (NaV1.7), thereby causing sustained reduction of NaV1.7 currents.

<span class="mw-page-title-main">GiTx1</span>

GiTx1 (β/κ-theraphotoxin-Gi1a) is a peptide toxin present in the venom of Grammostola iheringi. It reduces both inward and outward currents by blocking voltage-gated sodium and potassium channels, respectively.

<span class="mw-page-title-main">Versutoxin</span>

Delta hexatoxin Hv1 is a neurotoxic component found in the venom of the Australian funnel web spider.

<span class="mw-page-title-main">GsMTx-4</span> Grammostola mechanotoxin 4

Grammostola mechanotoxin #4, also known as M-theraphotoxin-Gr1a (M-TRTX-Gr1a), is a neurotoxin isolated from the venom of the spider Chilean rose tarantula Grammostola spatulate. This amphiphilic peptide, which consists of 35 amino acids, belongs to the inhibitory cysteine knot (ICK) peptide family. It reduces mechanical sensation by inhibiting mechanosensitive channels (MSCs).

Phlotoxin is a neurotoxin from the venom of the tarantula Phlogiellus that targets mostly voltage-sensitive sodium channels and mainly Nav1.7. The only non-sodium voltage-sensitive channel that is inhibited by Phlotoxin is Kv3.4. Nav1.4 and Nav1.6 seem to be Phlotoxin-1-sensitive to some extent as well.

References

  1. 1 2 3 4 Ohkubo, Tsuyako; Yamazaki, Jun; Kitamura, Kenji (2010). "Tarantula Toxin ProTx-I Differentiates Between Human T-type Voltage-Gated Ca2+ Channels Cav3.1 and Cav3.2". Journal of Pharmacological Sciences. 112 (4): 452–458. doi: 10.1254/jphs.09356FP . PMID   20351484. S2CID   29721634.
  2. 1 2 3 Bladen, Chris; Hamid, Jawed; Souza, Ivana A.; Zamponi, Gerald W. (2014-05-09). "Block of T-type calcium channels by protoxins I and II". Molecular Brain. 7 (1): 36. doi: 10.1186/1756-6606-7-36 . ISSN   1756-6606. PMC   4030284 . PMID   24886690.
  3. 1 2 3 4 5 6 Middleton, Richard E.; Warren, Vivien A.; Kraus, Richard L.; Hwang, Jeremy C.; Liu, Chou J.; Dai, Ge; Brochu, Richard M.; Kohler, Martin G.; Gao, Ying-Duo; Garsky, Victor M.; Bogusky, Michael J. (2002-12-01). "Two Tarantula Peptides Inhibit Activation of Multiple Sodium Channels". Biochemistry. 41 (50): 14734–14747. doi:10.1021/bi026546a. ISSN   0006-2960. PMID   12475222.
  4. 1 2 Priest, Birgit T.; Blumenthal, Kenneth M.; Smith, Jaime J.; Warren, Vivien A.; Smith, McHardy M. (2007-02-01). "ProTx-I and ProTx-II: Gating modifiers of voltage-gated sodium channels". Toxicon. Gating Modifier Peptides of Ion Channels. 49 (2): 194–201. doi:10.1016/j.toxicon.2006.09.014. ISSN   0041-0101. PMID   17087985.
  5. 1 2 3 4 5 6 7 8 Gui, Junhong; Liu, Boyi; Cao, Guan; Lipchik, Andrew M.; Perez, Minervo; Dekan, Zoltan; Mobli, Mehdi; Daly, Norelle L.; Alewood, Paul F.; Parker, Laurie L.; King, Glenn F. (2014-03-03). "A Tarantula-Venom Peptide Antagonizes the TRPA1 Nociceptor Ion Channel by Binding to the S1–S4 Gating Domain". Current Biology. 24 (5): 473–483. doi:10.1016/j.cub.2014.01.013. ISSN   0960-9822. PMC   3949122 . PMID   24530065. S2CID   7479469.
  6. ↑ King, Glenn F.; Hardy, Margaret C. (2013-01-07). "Spider-Venom Peptides: Structure, Pharmacology, and Potential for Control of Insect Pests". Annual Review of Entomology. 58 (1): 475–496. doi:10.1146/annurev-ento-120811-153650. ISSN   0066-4170. PMID   23020618.
  7. 1 2 3 4 5 6 Rupasinghe, Darshani B.; Herzig, Volker; Vetter, Irina; Dekan, Zoltan; Gilchrist, John; Bosmans, Frank; Alewood, Paul F.; Lewis, Richard J.; King, Glenn F. (2020-11-01). "Mutational analysis of ProTx-I and the novel venom peptide Pe1b provide insight into residues responsible for selective inhibition of the analgesic drug target NaV1.7". Biochemical Pharmacology. Pharmacology and Therapeutic Potential of Venom Peptides. 181: 114080. doi:10.1016/j.bcp.2020.114080. ISSN   0006-2952. PMID   32511987. S2CID   219549375.
  8. 1 2 3 4 5 Agwa, Akello J.; Peigneur, Steve; Chow, Chun Yuen; Lawrence, Nicole; Craik, David J.; Tytgat, Jan; King, Glenn F.; Henriques, Sónia Troeira; Schroeder, Christina I. (June 2018). "Gating modifier toxins isolated from spider venom: Modulation of voltage-gated sodium channels and the role of lipid membranes". Journal of Biological Chemistry. 293 (23): 9041–9052. doi: 10.1074/jbc.RA118.002553 . PMC   5995520 . PMID   29703751.
  9. ↑ Shen, Huaizong; Li, Zhangqiang; Jiang, Yan; Pan, Xiaojing; Wu, Jianping; Cristofori-Armstrong, Ben; Smith, Jennifer J.; Chin, Yanni K. Y.; Lei, Jianlin; Zhou, Qiang; King, Glenn F. (2018-10-19). "Structural basis for the modulation of voltage-gated sodium channels by animal toxins". Science. 362 (6412): eaau2596. doi: 10.1126/science.aau2596 . ISSN   0036-8075. PMID   30049784. S2CID   206667555.
  10. ↑ Deplazes, Evelyne; Henriques, Sónia Troeira; Smith, Jennifer J.; King, Glenn F.; Craik, David J.; Mark, Alan E.; Schroeder, Christina I. (2016-04-01). "Membrane-binding properties of gating modifier and pore-blocking toxins: Membrane interaction is not a prerequisite for modification of channel gating". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1858 (4): 872–882. doi: 10.1016/j.bbamem.2016.02.002 . ISSN   0005-2736. PMID   26850736.
  11. ↑ Minassian, Natali A.; Gibbs, Alan; Shih, Amy Y.; Liu, Yi; Neff, Robert A.; Sutton, Steven W.; Mirzadegan, Tara; Connor, Judith; Fellows, Ross; Husovsky, Matthew; Nelson, Serena (August 2013). "Analysis of the Structural and Molecular Basis of Voltage-sensitive Sodium Channel Inhibition by the Spider Toxin Huwentoxin-IV (μ-TRTX-Hh2a)". Journal of Biological Chemistry. 288 (31): 22707–22720. doi: 10.1074/jbc.M113.461392 . PMC   3829356 . PMID   23760503.
  12. ↑ Cai, Tianfu; Luo, Ji; Meng, Er; Ding, Jiuping; Liang, Songping; Wang, Sheng; Liu, Zhonghua (June 2015). "Mapping the interaction site for the tarantula toxin hainantoxin-IV (β-TRTX-Hn2a) in the voltage sensor module of domain II of voltage-gated sodium channels". Peptides. 68: 148–156. doi:10.1016/j.peptides.2014.09.005. PMID   25218973. S2CID   5610614.
  13. ↑ Nicolas, Sébastien; Zoukimian, Claude; Bosmans, Frank; Montnach, Jérôme; Diochot, Sylvie; Cuypers, Eva; De Waard, Stephan; Béroud, Rémy; Mebs, Dietrich; Craik, David; Boturyn, Didier (2019-06-21). "Chemical Synthesis, Proper Folding, Nav Channel Selectivity Profile and Analgesic Properties of the Spider Peptide Phlotoxin 1". Toxins. 11 (6): 367. doi: 10.3390/toxins11060367 . ISSN   2072-6651. PMC   6628435 . PMID   31234412.
  14. ↑ Koivisto, Ari; Jalava, Niina; Bratty, Raymond; Pertovaara, Antti (2018-11-01). "TRPA1 Antagonists for Pain Relief". Pharmaceuticals. 11 (4): 117. doi: 10.3390/ph11040117 . ISSN   1424-8247. PMC   6316422 . PMID   30388732.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.