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Chemical Compound Review:

alpha-Ctx-imi (3S)-4-[(2S)-2-[[(1S)-1- [[(1S)-1-[[(1S)-1...

Synonyms: Conotoxin IMI, alpha-CTX IMI, CHEMBL500076, CTX IMI, AC1L3206, ...

Pereira, E.F. et al., López, M.G. et al., Courjaret, R. et al., Kaiser, S. et al., Ellison, M. et al., et al.

Ellison, McIntosh, Olivera,

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High impact information on alpha-Ctx-imi

These supramaximal concentrations of alpha7 nicotinic receptor blockers depressed by 30% (MLA), 25% (alpha-bungarotoxin), and 50% (alpha-conotoxin ImI) the inward current generated by 1-s pulses of 100 microM ACh, applied to voltage-clamped chromaffin cells [1].
Furthermore, functional studies in oocytes indicate that there is no overlap between functional binding sites of alpha-CTx ImI and alpha-CTx ImII [2].
Because alpha-CTx ImI and alpha-CTx ImII share extensive sequence homology, the inability of alpha-CTx ImII to compete with alpha-BgTx is surprising [2].
We found that two distinct components underlying the biphasic curve differed in their ionic permeability and pharmacology (one being sensitive to d-tubocurarine, and the other affected only by mecamylamine and alpha-conotoxin ImI) [3].
Responses to a high concentration of anatoxin-a (25 microM) in slices (but not in synaptosomes) were partially blocked by ionotropic glutamate receptor antagonists (kynurenic acid, 6,7-dinitroquinoxaline-2,3-dione) and by alpha7*-selective nAChR antagonists (alpha-bungarotoxin, alpha-conotoxin-ImI, methyllycaconitine) in a nonadditive manner [4].

Biological context of alpha-Ctx-imi

Several lines of evidence revealed that the inhibitory effect of alpha-conotoxin-ImI was competitive with respect to the agonist (IC50 approximately 85 nM) and reversible by washing [5].

Anatomical context of alpha-Ctx-imi

In contrast, alpha-CTX ImI had no effect at the neuromuscular junction over the concentration range 1-20 microM [6].
The competitive and reversible nature of the alpha-conotoxin-ImI-induced inhibition of native alpha 7-bearing neuronal nicotinic receptors makes this peptide a valuable new tool for the functional and structural characterization of these receptors in the central nervous system [5].
Neither methyllycaconitine, alpha-bungarotoxin, nor alpha-conotoxin-ImI affected nicotine-evoked [3H]DA release from either striatum or prefrontal cortex [7].
Comparative structure-function studies have been carried out for alpha-conotoxin GI acting on nicotinic acetylcholine receptors (AChR) from mammalian muscles and from the electric organ of the Torpedo californica ray and for alpha-conotoxin ImI, which targets the neuronal alpha7 AChR [8].

Associations of alpha-Ctx-imi with other chemical compounds

Methyllycaconitine (MLA), alpha-conotoxin ImI, and alpha-bungarotoxin inhibited the release of catecholamines triggered by brief pulses of acetylcholine (ACh) (100 microM, 5 s) applied to fast-superfused bovine adrenal chromaffin cells, with IC50s of 100 nM for MLA and 300 nM for alpha-conotoxin ImI and alpha-bungarotoxin [1].

Analytical, diagnostic and therapeutic context of alpha-Ctx-imi

In the present study, the patch-clamp technique was applied to rat hippocampal neurons or myoballs in culture to study the actions of alpha-conotoxin-ImI on the native alpha-bungarotoxin-sensitive, presumably alpha 7-bearing, neuronal nicotinic receptor and on other ligand-gated channels [5].

References

Unmasking the functions of the chromaffin cell alpha7 nicotinic receptor by using short pulses of acetylcholine and selective blockers. López, M.G., Montiel, C., Herrero, C.J., García-Palomero, E., Mayorgas, I., Hernández-Guijo, J.M., Villarroya, M., Olivares, R., Gandía, L., McIntosh, J.M., Olivera, B.M., García, A.G. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
Alpha-conotoxins ImI and ImII. Similar alpha 7 nicotinic receptor antagonists act at different sites. Ellison, M., McIntosh, J.M., Olivera, B.M. J. Biol. Chem. (2003) [Pubmed]
Complex intracellular messenger pathways regulate one type of neuronal alpha-bungarotoxin-resistant nicotinic acetylcholine receptors expressed in insect neurosecretory cells (dorsal unpaired median neurons). Courjaret, R., Lapied, B. Mol. Pharmacol. (2001) [Pubmed]
alpha-bungarotoxin-sensitive nicotinic receptors indirectly modulate [(3)H]dopamine release in rat striatal slices via glutamate release. Kaiser, S., Wonnacott, S. Mol. Pharmacol. (2000) [Pubmed]
Alpha-conotoxin-ImI: a competitive antagonist at alpha-bungarotoxin-sensitive neuronal nicotinic receptors in hippocampal neurons. Pereira, E.F., Alkondon, M., McIntosh, J.M., Albuquerque, E.X. J. Pharmacol. Exp. Ther. (1996) [Pubmed]
Alpha-conotoxin ImI inhibits the alpha-bungarotoxin-resistant nicotinic response in bovine adrenal chromaffin cells. Broxton, N.M., Down, J.G., Gehrmann, J., Alewood, P.F., Satchell, D.G., Livett, B.G. J. Neurochem. (1999) [Pubmed]
Different nicotinic acetylcholine receptor subtypes mediating striatal and prefrontal cortical [3H]dopamine release. Cao, Y.J., Surowy, C.S., Puttfarcken, P.S. Neuropharmacology (2005) [Pubmed]
A comparative study on selectivity of alpha-conotoxins GI and ImI using their synthetic analogues and derivatives. Kasheverov, I.E., Zhmak, M.N., Maslennikov, I.V., Utkin, Y.N., Tsetlin, V.I. Neurochem. Res. (2003) [Pubmed]

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