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The butyrylcholinesterase K variant confers structurally derived risks for Alzheimer pathology.

Podoly E, Shalev DE, Shenhar-Tsarfaty S, Bennett ER, Ben Assayag E, Wilgus H, Livnah O, Soreq H - J. Biol. Chem. (2009)

Bottom Line: Here, we report that BChE-K is inherently unstable as compared with the "usual" BChE (BChE-U), resulting in reduced hydrolytic activity and predicting prolonged acetylcholine maintenance and protection from AD.A synthetic peptide derived from the C terminus of BChE-K (BSP-K), which displayed impaired intermolecular interactions, was less potent in suppressing Abeta oligomerization than its BSP-U counterpart.Dual activity structurally derived changes due to the A539T substitution can thus account for both neuroprotective characteristics caused by sustained acetylcholine levels and elevated AD risk due to inefficient interference with amyloidogenic processes.

View Article: PubMed Central - PubMed

Affiliation: The Alexander Silberman Life Sciences Institute, Hebrew University of Jerusalem, Jerusalem 91904, Israel.

ABSTRACT
The K variant of butyrylcholinesterase (BChE-K, 20% incidence) is a long debated risk factor for Alzheimer disease (AD). The A539T substitution in BChE-K is located at the C terminus, which is essential both for BChE tetramerization and for its capacity to attenuate beta-amyloid (Abeta) fibril formation. Here, we report that BChE-K is inherently unstable as compared with the "usual" BChE (BChE-U), resulting in reduced hydrolytic activity and predicting prolonged acetylcholine maintenance and protection from AD. A synthetic peptide derived from the C terminus of BChE-K (BSP-K), which displayed impaired intermolecular interactions, was less potent in suppressing Abeta oligomerization than its BSP-U counterpart. Correspondingly, highly purified recombinant human rBChE-U monomers suppressed beta-amyloid fibril formation less effectively than dimers, which also protected cultured neuroblastoma cells from Abeta neurotoxicity. Dual activity structurally derived changes due to the A539T substitution can thus account for both neuroprotective characteristics caused by sustained acetylcholine levels and elevated AD risk due to inefficient interference with amyloidogenic processes.

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rBChE-U dimers attenuate Aβ fibril formation more effectively than monomers. A, initial dimer and monomer content in rBChE-U preparation. B, modeled BChE-U monomers and dimers built according to PDB structure 1EEAY of the tetrameric structure of AChE-S. AU, arbitrary units. C, ThT fluorescence demonstrating that highly purified dimers of rBChE-U suppressed Aβ fibril formation more efficiently than monomeric rBChE-U. Inset, percentage of attenuated Aβ fibril formation elicited by monomers (m) and dimers (d). D and E, rates of fluorescence changes demonstrating the difference in the capacity for attenuating fibril formation by human recombinant rBChE dimers (d) or serum-derived tetramers (t). F, bis-ANS kinetics demonstrating an apparently similar time scale and sustained fluorescence signal in the presence of bis-ANS as compared with the suppressed signal with ThT, both supporting our working hypothesis.
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Figure 4: rBChE-U dimers attenuate Aβ fibril formation more effectively than monomers. A, initial dimer and monomer content in rBChE-U preparation. B, modeled BChE-U monomers and dimers built according to PDB structure 1EEAY of the tetrameric structure of AChE-S. AU, arbitrary units. C, ThT fluorescence demonstrating that highly purified dimers of rBChE-U suppressed Aβ fibril formation more efficiently than monomeric rBChE-U. Inset, percentage of attenuated Aβ fibril formation elicited by monomers (m) and dimers (d). D and E, rates of fluorescence changes demonstrating the difference in the capacity for attenuating fibril formation by human recombinant rBChE dimers (d) or serum-derived tetramers (t). F, bis-ANS kinetics demonstrating an apparently similar time scale and sustained fluorescence signal in the presence of bis-ANS as compared with the suppressed signal with ThT, both supporting our working hypothesis.

Mentions: The C-terminal domains of both BChE dimers and monomers are relatively exposed to the surrounding environment, as modeled based on the tetrameric structure of AChE-S (Fig. 4A). Separate fractions of BChE dimers and monomers were used to compare the effects caused by these C termini. rBChE-U production in the milk of transgenic goats yielded primarily dimeric protein, with ∼10% monomeric fraction, as shown by mass spectrometry (46) (Fig. 4B). Column chromatography was used to separate monomers from dimers. ThT fluorescence measurements showed that isolated fractions of highly purified rBChE-U monomers and dimers both attenuated fibril formation at a molar ratio of 1:100 to Aβ. However, monomeric and dimeric rBChE-U showed different durations of the lag and growth phases in the fibril formation process (Fig. 4C). Dimeric rBChE-U attenuated Aβ fibril formation more than the monomeric BChE and presented a longer lag time and 20% less fluorescent signal at the plateau (Fig. 4C and inset). Furthermore, calculating the rate of fibril formation revealed that recombinant BChE dimers (Fig. 4D), and yet more so, native BChE from human serum (Fig. 4E) attenuate this process, suggesting direct association of this rate with the number of enzyme subunits. Inversely, a bis-ANS response curve to rBChE interaction with Aβ showed an apparently similar time scale and sustained fluorescence signal, unlike the reduced signal in the thioflavin T tests (Fig. 4F), both supporting our working hypothesis.


The butyrylcholinesterase K variant confers structurally derived risks for Alzheimer pathology.

Podoly E, Shalev DE, Shenhar-Tsarfaty S, Bennett ER, Ben Assayag E, Wilgus H, Livnah O, Soreq H - J. Biol. Chem. (2009)

rBChE-U dimers attenuate Aβ fibril formation more effectively than monomers. A, initial dimer and monomer content in rBChE-U preparation. B, modeled BChE-U monomers and dimers built according to PDB structure 1EEAY of the tetrameric structure of AChE-S. AU, arbitrary units. C, ThT fluorescence demonstrating that highly purified dimers of rBChE-U suppressed Aβ fibril formation more efficiently than monomeric rBChE-U. Inset, percentage of attenuated Aβ fibril formation elicited by monomers (m) and dimers (d). D and E, rates of fluorescence changes demonstrating the difference in the capacity for attenuating fibril formation by human recombinant rBChE dimers (d) or serum-derived tetramers (t). F, bis-ANS kinetics demonstrating an apparently similar time scale and sustained fluorescence signal in the presence of bis-ANS as compared with the suppressed signal with ThT, both supporting our working hypothesis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2719355&req=5

Figure 4: rBChE-U dimers attenuate Aβ fibril formation more effectively than monomers. A, initial dimer and monomer content in rBChE-U preparation. B, modeled BChE-U monomers and dimers built according to PDB structure 1EEAY of the tetrameric structure of AChE-S. AU, arbitrary units. C, ThT fluorescence demonstrating that highly purified dimers of rBChE-U suppressed Aβ fibril formation more efficiently than monomeric rBChE-U. Inset, percentage of attenuated Aβ fibril formation elicited by monomers (m) and dimers (d). D and E, rates of fluorescence changes demonstrating the difference in the capacity for attenuating fibril formation by human recombinant rBChE dimers (d) or serum-derived tetramers (t). F, bis-ANS kinetics demonstrating an apparently similar time scale and sustained fluorescence signal in the presence of bis-ANS as compared with the suppressed signal with ThT, both supporting our working hypothesis.
Mentions: The C-terminal domains of both BChE dimers and monomers are relatively exposed to the surrounding environment, as modeled based on the tetrameric structure of AChE-S (Fig. 4A). Separate fractions of BChE dimers and monomers were used to compare the effects caused by these C termini. rBChE-U production in the milk of transgenic goats yielded primarily dimeric protein, with ∼10% monomeric fraction, as shown by mass spectrometry (46) (Fig. 4B). Column chromatography was used to separate monomers from dimers. ThT fluorescence measurements showed that isolated fractions of highly purified rBChE-U monomers and dimers both attenuated fibril formation at a molar ratio of 1:100 to Aβ. However, monomeric and dimeric rBChE-U showed different durations of the lag and growth phases in the fibril formation process (Fig. 4C). Dimeric rBChE-U attenuated Aβ fibril formation more than the monomeric BChE and presented a longer lag time and 20% less fluorescent signal at the plateau (Fig. 4C and inset). Furthermore, calculating the rate of fibril formation revealed that recombinant BChE dimers (Fig. 4D), and yet more so, native BChE from human serum (Fig. 4E) attenuate this process, suggesting direct association of this rate with the number of enzyme subunits. Inversely, a bis-ANS response curve to rBChE interaction with Aβ showed an apparently similar time scale and sustained fluorescence signal, unlike the reduced signal in the thioflavin T tests (Fig. 4F), both supporting our working hypothesis.

Bottom Line: Here, we report that BChE-K is inherently unstable as compared with the "usual" BChE (BChE-U), resulting in reduced hydrolytic activity and predicting prolonged acetylcholine maintenance and protection from AD.A synthetic peptide derived from the C terminus of BChE-K (BSP-K), which displayed impaired intermolecular interactions, was less potent in suppressing Abeta oligomerization than its BSP-U counterpart.Dual activity structurally derived changes due to the A539T substitution can thus account for both neuroprotective characteristics caused by sustained acetylcholine levels and elevated AD risk due to inefficient interference with amyloidogenic processes.

View Article: PubMed Central - PubMed

Affiliation: The Alexander Silberman Life Sciences Institute, Hebrew University of Jerusalem, Jerusalem 91904, Israel.

ABSTRACT
The K variant of butyrylcholinesterase (BChE-K, 20% incidence) is a long debated risk factor for Alzheimer disease (AD). The A539T substitution in BChE-K is located at the C terminus, which is essential both for BChE tetramerization and for its capacity to attenuate beta-amyloid (Abeta) fibril formation. Here, we report that BChE-K is inherently unstable as compared with the "usual" BChE (BChE-U), resulting in reduced hydrolytic activity and predicting prolonged acetylcholine maintenance and protection from AD. A synthetic peptide derived from the C terminus of BChE-K (BSP-K), which displayed impaired intermolecular interactions, was less potent in suppressing Abeta oligomerization than its BSP-U counterpart. Correspondingly, highly purified recombinant human rBChE-U monomers suppressed beta-amyloid fibril formation less effectively than dimers, which also protected cultured neuroblastoma cells from Abeta neurotoxicity. Dual activity structurally derived changes due to the A539T substitution can thus account for both neuroprotective characteristics caused by sustained acetylcholine levels and elevated AD risk due to inefficient interference with amyloidogenic processes.

Show MeSH
Related in: MedlinePlus