| Structural highlights
Function
[CXM3A_CONPU] Mu-conotoxins block voltage-gated sodium channels (Nav). This toxin potently blocks rNav1.4/SCN4A. It also moderately blocks rNav1.1/SCN1A, rNav1.2/SCN2A, rNav1.3/SCN3A, mNav1.6/SCN8A, and h/rNav1.7/SCN9A. This inhibition is reversible. The block of SCN1A, SCN2A, and SCN8A is modified when beta-subunits are coexpressed with alpha subunits. Hence, blocks of channels containing the beta-1 and beta-3 subunits are more potent (compared to channels without beta subunits), whereas blocks of channels containing the beta-2 and beta-4 are less potent (compared to channels without beta subunits). This peptide causes flaccid paralysis in both mice and fish.[1] [2] [3] [4] [5]
Publication Abstract from PubMed
Mu-conotoxins are peptide inhibitors of voltage-sensitive sodium channels (VSSCs). Synthetic forms of mu-conotoxins PIIIA and PIIIA-(2-22) were found to inhibit tetrodotoxin (TTX)-sensitive VSSC current but had little effect on TTX-resistant VSSC current in sensory ganglion neurons. In rat brain neurons, these peptides preferentially inhibited the persistent over the transient VSSC current. Radioligand binding assays revealed that PIIIA, PIIIA-(2-22), and mu-conotoxins GIIIB discriminated among TTX-sensitive VSSCs in rat brain, that these and GIIIC discriminated among the corresponding VSSCs in human brain, and GIIIA had low affinity for neuronal VSSCs. (1)H NMR studies found that PIIIA adopts two conformations in solution due to cis/trans isomerization at hydroxyproline 8. The major trans conformation results in a three-dimensional structure that is significantly different from the previously identified conformation of mu-conotoxins GIIIA and GIIIB that selectively target TTX-sensitive muscle VSSCs. Comparison of the structures and activity of PIIIA to muscle-selective mu-conotoxins provides an insight into the structural requirements for inhibition of different TTX-sensitive sodium channels by mu-conotoxins.
Solution structure of mu-conotoxin PIIIA, a preferential inhibitor of persistent tetrodotoxin-sensitive sodium channels.,Nielsen KJ, Watson M, Adams DJ, Hammarstrom AK, Gage PW, Hill JM, Craik DJ, Thomas L, Adams D, Alewood PF, Lewis RJ J Biol Chem. 2002 Jul 26;277(30):27247-55. Epub 2002 May 2. PMID:12006587[6]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Holford M, Zhang MM, Gowd KH, Azam L, Green BR, Watkins M, Ownby JP, Yoshikami D, Bulaj G, Olivera BM. Pruning nature: Biodiversity-derived discovery of novel sodium channel blocking conotoxins from Conus bullatus. Toxicon. 2009 Jan;53(1):90-8. doi: 10.1016/j.toxicon.2008.10.017. Epub 2008 Nov, 20. PMID:18950653 doi:http://dx.doi.org/10.1016/j.toxicon.2008.10.017
- ↑ Favreau P, Benoit E, Hocking HG, Carlier L, D'hoedt D, Leipold E, Markgraf R, Schlumberger S, Cordova MA, Gaertner H, Paolini-Bertrand M, Hartley O, Tytgat J, Heinemann SH, Bertrand D, Boelens R, Stocklin R, Molgo J. Pharmacological characterization of a novel mu-conopeptide, CnIIIC, indicates potent and preferential inhibition of sodium channel subtypes (Na(V) 1.2/1.4) and reveals unusual activity on neuronal nicotinic acetylcholine receptors. Br J Pharmacol. 2012 Jan 9. doi: 10.1111/j.1476-5381.2012.01837.x. PMID:22229737 doi:10.1111/j.1476-5381.2012.01837.x
- ↑ Wilson MJ, Yoshikami D, Azam L, Gajewiak J, Olivera BM, Bulaj G, Zhang MM. mu-Conotoxins that differentially block sodium channels NaV1.1 through 1.8 identify those responsible for action potentials in sciatic nerve. Proc Natl Acad Sci U S A. 2011 Jun 21;108(25):10302-7. doi:, 10.1073/pnas.1107027108. Epub 2011 Jun 7. PMID:21652775 doi:http://dx.doi.org/10.1073/pnas.1107027108
- ↑ Zhang MM, Wilson MJ, Azam L, Gajewiak J, Rivier JE, Bulaj G, Olivera BM, Yoshikami D. Co-expression of Na(V)beta subunits alters the kinetics of inhibition of voltage-gated sodium channels by pore-blocking mu-conotoxins. Br J Pharmacol. 2013 Apr;168(7):1597-610. doi: 10.1111/bph.12051. PMID:23146020 doi:http://dx.doi.org/10.1111/bph.12051
- ↑ Tietze AA, Tietze D, Ohlenschlager O, Leipold E, Ullrich F, Kuhl T, Mischo A, Buntkowsky G, Gorlach M, Heinemann SH, Imhof D. Structurally diverse mu-conotoxin PIIIA isomers block sodium channel NaV 1.4. Angew Chem Int Ed Engl. 2012 Apr 23;51(17):4058-61. doi: 10.1002/anie.201107011. , Epub 2012 Mar 12. PMID:22407516 doi:http://dx.doi.org/10.1002/anie.201107011
- ↑ Nielsen KJ, Watson M, Adams DJ, Hammarstrom AK, Gage PW, Hill JM, Craik DJ, Thomas L, Adams D, Alewood PF, Lewis RJ. Solution structure of mu-conotoxin PIIIA, a preferential inhibitor of persistent tetrodotoxin-sensitive sodium channels. J Biol Chem. 2002 Jul 26;277(30):27247-55. Epub 2002 May 2. PMID:12006587 doi:10.1074/jbc.M201611200
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