Neurotoxicity of channel mutations in heterologously expressed alpha7-nicotinic acetylcholine receptors.
Nicotinic acetylcholine receptors (nAChR) composed of chick alpha7 subunits mutated to threonine at amino acid valine-251 in the putative channel-lining M2 domain were expressed heterologously in several neuron-like and non-neuronal mammalian cell lines. Expression of mutant alpha7-nAChR is toxic to neuron-like cells of the human neuroblastoma cell lines SH-SY5Y and IMR-32, but not to several other cell types. Growth in the presence of the alpha7-nAChR antagonist methyllycaconitine (MLA) protects against neurotoxicity, as does gradual downregulation of functional, mutant alpha7-nAChR in surviving transfected SH-SY5Y cells. Relative to wild-type alpha7-nAChR, functional alpha7-nAChR mutants show a higher affinity for agonists, slower rates of desensitization, and sensitivity to dihydro-beta-erythroidine (DHbetaE) as an agonist, but they retain sensitivity to MLA as a competitive antagonist. These findings demonstrate that expression of hyperfunctional, mutant forms of Ca2+-permeable alpha7-nAChR is toxic to neuron-like cells.
Lukas
R J
RJ
Division of Neurobiology, Barrow Neurological Institute, Phoenix, AZ 85013, USA. rlukas@chw.edu
Lucero
L
L
Buisson
B
B
Galzi
J L
JL
Puchacz
E
E
Fryer
J D
JD
Changeux
J P
JP
Bertrand
D
D
D000157:Aconitine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002038:Bungarotoxins / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002645:Chickens; D004594:Electrophysiology; D006801:Humans; D007473:Ion Channels / Q000235:genetics* / Q000502:physiology; D051379:Mice; D009154:Mutation / Q000502:physiology*; D009447:Neuroblastoma / Q000473:pathology / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018722:Nicotinic Agonists / Q000378:metabolism; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D002038:Bungarotoxins; D007473:Ion Channels; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; C054634:methyllycaconitine; D000157:Aconitine