Cellular neuroscienceTransgenic mice over-expressing human β-amyloid have functional nicotinic alpha 7 receptors
Section snippets
Cloning of human and mouse nicotinic α7 receptors
A human α7 nicotinic acetylcholine (ACh) receptor cDNA, corresponding to GenBank accession number U62436 (Elliott et al., 1996) with the exception of a single silent base pair substitution, was isolated from a human cerebellum library and subcloned into the PvuII site of the episomal vector pCEP4 (Invitrogen Ltd., Paisley, UK). The resulting expression construct was transfected into the rat pituitary tumor GH4C1 cell line (European Collection of Cell Cultures, Salisbury, UK) as described
Nicotinic α7 receptors expressed in GH4C1 cells
We initially characterized the basic response properties of the human α7 receptor using whole-cell patch clamp recordings (Vhold −74 mV) from GH4C1 cells stably expressing an appropriate construct. In response to 250 ms challenges with high concentrations of either ACh (300–1000μM) or nicotine (100μM), these cells typically exhibited rapidly and almost completely desensitizing inward currents, with an average amplitude of around 1 nA. Choline was also found to be an effective agonist albeit at
Discussion
In support of previous data reporting an inhibitory activity of Aβ peptide on both recombinant and native α7 receptors (Liu et al 2001, Pettit et al 2001, Tozaki et al 2002, Lee and Wang 2003), we have found that human Aβ1–42 can inhibit human α7 receptors stably expressed in a GH4C1 cell line. Given that AD, and the associated accumulation of Aβ, is a condition suffered by more than 20 million humans we feel these data are a useful extension to the previous important work performed on
Conclusions
In conclusion, we have confirmed that the human amyloid peptide is capable of inhibiting recombinant human and mouse α7 receptors. In contrast we are unable to identify a correlate of this inhibition in a transgenic mouse model of AD. Thus, we suggest that postsynaptic α7 receptors on hippocampal interneurones may be spared from any significant inhibition by excess Aβ. Furthermore, the fact that we never observe a complete block of α7 receptors by Aβ in the recombinant cell lines does suggest
References (49)
- et al.
Amyloid-beta: a chameleon walking in two worlds: a review of the trophic and toxic properties of amyloid-beta
Brain Res Brain Res Rev
(2003) - et al.
A neuronal nicotinic acetylcholine receptor subunit (alpha 7) is developmentally regulated and forms a homo-oligomeric channel blocked by alpha-BTX
Neuron
(1990) - et al.
Inhibition of nicotinic acetylcholine receptors by bicuculline
Neuropharmacology
(2001) - et al.
beta-Amyloid peptide activates alpha 7 nicotinic acetylcholine receptors expressed in Xenopus oocytes
J Biol Chem
(2002) - et al.
Accelerated plaque accumulation, associative learning deficits, and up-regulation of alpha 7 nicotinic receptor protein in transgenic mice co-expressing mutant human presenilin 1 and amyloid precursor proteins
J Biol Chem
(2002) - et al.
Serotonin antagonizes the human neuronal alpha7 nicotinic acetylcholine receptor and becomes an agonist after L248T alpha7 mutation
Neuroscience
(2002) - et al.
Fractional Ca(2+) current through human neuronal alpha7 nicotinic acetylcholine receptors
Cell Calcium
(2003) - et al.
Beta-amyloid peptide blocks the fast-inactivating K+ current in rat hippocampal neurons
Biophys J
(1996) - et al.
Reduced levels of Abeta 40 and Abeta 42 in brains of smoking controls and Alzheimer’s patients
Neurobiol Dis
(2004) - et al.
Cognitive correlates of Abeta deposition in male and female mice bearing amyloid precursor protein and presenilin-1 mutant transgenes
Brain Res
(2004)