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Upregulation of alpha7 Nicotinic Receptors by Acetylcholinesterase C-Terminal Peptides.

Bond CE, Zimmermann M, Greenfield SA - PLoS ONE (2009)

Bottom Line: Of more long-term significance, these peptides also induce upregulation of alpha7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane.The results reported here demonstrate a hitherto unknown relationship between the alpha7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain.Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.

View Article: PubMed Central - PubMed

Affiliation: Institute for the Future of the Mind, Department of Pharmacology, Oxford University, Oxford, UK. cherie.bond@pharm.ox.ac.uk

ABSTRACT

Background: The alpha-7 nicotinic acetylcholine receptor (alpha7-nAChR) is well known as a potent calcium ionophore that, in the brain, has been implicated in excitotoxicity and hence in the underlying mechanisms of neurodegenerative disorders such as Alzheimer's disease. Previous research implied that the activity of this receptor may be modified by exposure to a peptide fragment derived from the C-terminal region of the enzyme acetylcholinesterase. This investigation was undertaken to determine if the functional changes observed could be attributed to peptide binding interaction with the alpha7-nAChR, or peptide modulation of receptor expression.

Methodology/principal findings: This study provides evidence that two peptides derived from the C-terminus of acetylcholinesterase, not only selectively displace specific bungarotoxin binding at the alpha7-nAChR, but also alter receptor binding properties for its familiar ligands, including the alternative endogenous agonist choline. Of more long-term significance, these peptides also induce upregulation of alpha7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane.

Conclusions/significance: The results reported here demonstrate a hitherto unknown relationship between the alpha7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain. Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.

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AChE and control polypeptides used in this study.All isoforms of AChE are derived from a single gene transcript and contain the invariable exons 2, 3 and 4. The T-AChE isoform arises through alternative mRNA splicing of exon 6 to the invariable exons. Truncated AChE (T548) is a recombinant protein, translated from cDNA containing exons 2, 3, and 4, but lacking a C-terminal exon. The underlined amino acid sequence highlights the unique C-terminus of the T-AChE isoform derived from exon 6 of the AChE gene with the location and sequence of AChE peptides indicated. Control peptides used in experimentation include: S14, a scrambled version of AChE T14 peptide; B14, comprising the 14 amino acid region in butyrylcholinesterase (BuChE) that is homologous to AChE T14; and SB14, the scrambled version of the same region of BuChE.
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pone-0004846-g001: AChE and control polypeptides used in this study.All isoforms of AChE are derived from a single gene transcript and contain the invariable exons 2, 3 and 4. The T-AChE isoform arises through alternative mRNA splicing of exon 6 to the invariable exons. Truncated AChE (T548) is a recombinant protein, translated from cDNA containing exons 2, 3, and 4, but lacking a C-terminal exon. The underlined amino acid sequence highlights the unique C-terminus of the T-AChE isoform derived from exon 6 of the AChE gene with the location and sequence of AChE peptides indicated. Control peptides used in experimentation include: S14, a scrambled version of AChE T14 peptide; B14, comprising the 14 amino acid region in butyrylcholinesterase (BuChE) that is homologous to AChE T14; and SB14, the scrambled version of the same region of BuChE.

Mentions: Similarly, it has been proposed that acetylcholinesterase (AChE, EC 3.1.1.7) could have non-enzymatic functions unrelated to the cholinergic synapse [2], [24]–[26]. Previous evidence, albeit indirect, has indicated that a 14-amino acid peptide sequence in the C-terminus of AChE independently modulates α7-nAChR responses to agonists [27]–[28]. This peptide bears a striking homology and structural similarity to Aβ [2] and replicates [29]–[33] many of the non-hydrolytic actions now well established for the enzyme in a wide range of preparations and particular situations, such as development [25]–[26], [34]–[36] and apoptosis [37]–[38]. However, recent detailed analyses of critical amino acid residues [39]–[40], potential protease cleavage sites in the C-terminus of AChE [41], and structural features [39]–[41], have now identified a larger candidate bioactive motif of 30 amino acids that encompasses the originally recognized 14 amino acid sequence (Fig. 1). Since both peptides are derived from the “tailed” (T) isoform of AChE and are comprised of 14 and 30 amino acids respectively, for convenience they are referred to as ‘T14’ and ‘T30’.


Upregulation of alpha7 Nicotinic Receptors by Acetylcholinesterase C-Terminal Peptides.

Bond CE, Zimmermann M, Greenfield SA - PLoS ONE (2009)

AChE and control polypeptides used in this study.All isoforms of AChE are derived from a single gene transcript and contain the invariable exons 2, 3 and 4. The T-AChE isoform arises through alternative mRNA splicing of exon 6 to the invariable exons. Truncated AChE (T548) is a recombinant protein, translated from cDNA containing exons 2, 3, and 4, but lacking a C-terminal exon. The underlined amino acid sequence highlights the unique C-terminus of the T-AChE isoform derived from exon 6 of the AChE gene with the location and sequence of AChE peptides indicated. Control peptides used in experimentation include: S14, a scrambled version of AChE T14 peptide; B14, comprising the 14 amino acid region in butyrylcholinesterase (BuChE) that is homologous to AChE T14; and SB14, the scrambled version of the same region of BuChE.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2654408&req=5

pone-0004846-g001: AChE and control polypeptides used in this study.All isoforms of AChE are derived from a single gene transcript and contain the invariable exons 2, 3 and 4. The T-AChE isoform arises through alternative mRNA splicing of exon 6 to the invariable exons. Truncated AChE (T548) is a recombinant protein, translated from cDNA containing exons 2, 3, and 4, but lacking a C-terminal exon. The underlined amino acid sequence highlights the unique C-terminus of the T-AChE isoform derived from exon 6 of the AChE gene with the location and sequence of AChE peptides indicated. Control peptides used in experimentation include: S14, a scrambled version of AChE T14 peptide; B14, comprising the 14 amino acid region in butyrylcholinesterase (BuChE) that is homologous to AChE T14; and SB14, the scrambled version of the same region of BuChE.
Mentions: Similarly, it has been proposed that acetylcholinesterase (AChE, EC 3.1.1.7) could have non-enzymatic functions unrelated to the cholinergic synapse [2], [24]–[26]. Previous evidence, albeit indirect, has indicated that a 14-amino acid peptide sequence in the C-terminus of AChE independently modulates α7-nAChR responses to agonists [27]–[28]. This peptide bears a striking homology and structural similarity to Aβ [2] and replicates [29]–[33] many of the non-hydrolytic actions now well established for the enzyme in a wide range of preparations and particular situations, such as development [25]–[26], [34]–[36] and apoptosis [37]–[38]. However, recent detailed analyses of critical amino acid residues [39]–[40], potential protease cleavage sites in the C-terminus of AChE [41], and structural features [39]–[41], have now identified a larger candidate bioactive motif of 30 amino acids that encompasses the originally recognized 14 amino acid sequence (Fig. 1). Since both peptides are derived from the “tailed” (T) isoform of AChE and are comprised of 14 and 30 amino acids respectively, for convenience they are referred to as ‘T14’ and ‘T30’.

Bottom Line: Of more long-term significance, these peptides also induce upregulation of alpha7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane.The results reported here demonstrate a hitherto unknown relationship between the alpha7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain.Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.

View Article: PubMed Central - PubMed

Affiliation: Institute for the Future of the Mind, Department of Pharmacology, Oxford University, Oxford, UK. cherie.bond@pharm.ox.ac.uk

ABSTRACT

Background: The alpha-7 nicotinic acetylcholine receptor (alpha7-nAChR) is well known as a potent calcium ionophore that, in the brain, has been implicated in excitotoxicity and hence in the underlying mechanisms of neurodegenerative disorders such as Alzheimer's disease. Previous research implied that the activity of this receptor may be modified by exposure to a peptide fragment derived from the C-terminal region of the enzyme acetylcholinesterase. This investigation was undertaken to determine if the functional changes observed could be attributed to peptide binding interaction with the alpha7-nAChR, or peptide modulation of receptor expression.

Methodology/principal findings: This study provides evidence that two peptides derived from the C-terminus of acetylcholinesterase, not only selectively displace specific bungarotoxin binding at the alpha7-nAChR, but also alter receptor binding properties for its familiar ligands, including the alternative endogenous agonist choline. Of more long-term significance, these peptides also induce upregulation of alpha7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane.

Conclusions/significance: The results reported here demonstrate a hitherto unknown relationship between the alpha7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain. Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.

Show MeSH
Related in: MedlinePlus