RGD Reference Report - Five ADNFLE mutations reduce the Ca2+ dependence of the mammalian alpha4beta2 acetylcholine response. - Rat Genome Database

RGD Reference Report - Five ADNFLE mutations reduce the Ca2+ dependence of the mammalian alpha4beta2 acetylcholine response. - Rat Genome Database

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Five ADNFLE mutations reduce the Ca2+ dependence of the mammalian alpha4beta2 acetylcholine response.
Authors:	Rodrigues-Pinguet, N Jia, L Li, M Figl, A Klaassen, A Truong, A Lester, HA Cohen, BN
Citation:	Rodrigues-Pinguet N, etal., J Physiol 2003 Jul 1;550(Pt 1):11-26. Epub 2003 May 16.
RGD ID:	1358637
Pubmed:	PMID:12754307 (View Abstract at PubMed)
PMCID:	PMC2343021 (View Article at PubMed Central)
DOI:	DOI:10.1113/jphysiol.2002.036681 (Journal Full-text)
Five nicotinic acetylcholine receptor (nAChR) mutations are currently linked to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). The similarity of their clinical symptoms suggests that a common functional anomaly of the mutations underlies ADNFLE seizures. To identify this anomaly, we constructed rat orthologues (S252F, +L264, S256L, V262L, V262M) of the human ADNFLE mutations, expressed them in Xenopus oocytes with the appropriate wild-type (WT) subunit (alpha4 or beta2), and studied the Ca2+ dependence of their ACh responses. All the mutations significantly reduced 2 mM Ca2+-induced increases in the 30 microM ACh response (P < 0.05). Consistent with a dominant mode of inheritance, this reduction persisted in oocytes injected with a 1:1 mixture of mutant and WT cRNA. BAPTA injections showed that the reduction was not due to a decrease in the secondary activation of Ca2+-activated Cl- currents. The S256L mutation also abolished 2 mM Ba2+ potentiation of the ACh response. The S256L, V262L and V262M mutations had complex effects on the ACh concentration-response relationship but all three mutations shifted the concentration-response relationship to the left at [ACh] >= 30 microM. Co-expression of the V262M mutation with a mutation (E180Q) that abolished Ca2+ potentiation resulted in 2 mM Ca2+ block, rather than potentiation, of the 30 microM ACh response, suggesting that the ADNFLE mutations reduce Ca2+ potentiation by enhancing Ca2+ block of the alpha4beta2 nAChR. Ca2+ modulation may prevent presynaptic alpha4beta2 nAChRs from overstimulating glutamate release at central excitatory synapses during bouts of synchronous, repetitive activity. Reducing the Ca2+ dependence of the ACh response could trigger seizures by increasing alpha4beta2-mediated glutamate release during such bouts.

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Term	Qualifier	Evidence	With	Reference	Notes	Source	Original Reference(s)
synaptic transmission, cholinergic		IMP		1358637		RGD

Objects Annotated

Genes (Rattus norvegicus)

Chrnb2 (cholinergic receptor nicotinic beta 2 subunit)

Objects referenced in this article

Gene	Chrna4	cholinergic receptor nicotinic alpha 4 subunit	Rattus norvegicus

Additional Information