The marine phycotoxin gymnodimine targets muscular and neuronal nicotinic acetylcholine receptor subtypes with high affinity.
Gymnodimines (GYMs) are phycotoxins exhibiting unusual structural features including a spirocyclic imine ring system and a trisubstituted tetrahydrofuran embedded within a 16-membered macrocycle. The toxic potential and the mechanism of action of GYM-A, highly purified from contaminated clams, have been assessed. GYM-A in isolated mouse phrenic hemidiaphragm preparations produced a concentration- and time-dependent block of twitch responses evoked by nerve stimulation, without affecting directly elicited muscle twitches, suggesting that it may block the muscle nicotinic acetylcholine (ACh) receptor (nAChR). This was confirmed by the blockade of miniature endplate potentials and the recording of subthreshold endplate potentials in GYM-A paralyzed frog and mouse isolated neuromuscular preparations. Patch-clamp recordings in Xenopus skeletal myocytes revealed that nicotinic currents evoked by constant iontophoretical ACh pulses were blocked by GYM-A in a reversible manner. GYM-A also blocked, in a voltage-independent manner, homomeric human alpha7 nAChR expressed in Xenopus oocytes. Competition-binding assays confirmed that GYM-A is a powerful ligand interacting with muscle-type nAChR, heteropentameric alpha3beta2, alpha4beta2, and chimeric alpha7-5HT(3) neuronal nAChRs. Our data show for the first time that GYM-A broadly targets nAChRs with high affinity explaining the basis of its neurotoxicity, and also pave the way for designing specific tests for accurate GYM-A detection in shellfish samples.
Kharrat
Riadh
R
Laboratoire de Neurobiologie Cellulaire et Moléculaire-UPR9040, CNRS, Institut de Neurobiologie Alfred Fessard-FRC2118, Gif sur Yvette, France.
Servent
Denis
D
Girard
Emmanuelle
E
Ouanounou
Gilles
G
Amar
Muriel
M
Marrouchi
Riadh
R
Benoit
Evelyne
E
Molgó
Jordi
J
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D049872:Bivalvia / Q000737:chemistry; D002038:Bungarotoxins / Q000378:metabolism; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D015870:Gene Expression / Q000187:drug effects; D006575:Heterocyclic Compounds, 3-Ring / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000494:pharmacology*; D006801:Humans; D006844:Hydrocarbons, Cyclic / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000494:pharmacology*; D007097:Imines / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D032342:Muscle Cells / Q000187:drug effects* / Q000378:metabolism; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011485:Protein Binding / Q000187:drug effects; D011978:Receptors, Nicotinic / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects; D014982:Xenopus laevis; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002038:Bungarotoxins; C579167:Chrna7 protein, human; C579166:Chrna7 protein, mouse; D006575:Heterocyclic Compounds, 3-Ring; D006844:Hydrocarbons, Cyclic; D007097:Imines; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; C407350:gymnodimine; D000109:Acetylcholine