Comparison of three amyloid assembly inhibitors: the sugar scyllo-inositol, the polyphenol epigallocatechin gallate, and the molecular tweezer CLR01
Authors: Thomas Schrader
Gal Bitan
Panchanan Maiti
Chunyu Wang
Zhenming Du
Sharmistha Sinha
Frank-Gerrit Klärner
Journal: ACS Chemical Neuroscience (2012)
Discipline: NEUROSCIENCE & BEHAVIOR
Keywords: compounds; inhibitors; modulators; amyloid β-protein; assembly
Affiliations: Department of Neurology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California, USA., Department of Biology, Rensselaer Polytechnic Institute, Troy, New York, United States, Institute of Organic Chemistry, University of Duisburg-Essen, Germany

Abstract:  Many compounds have been tested as inhibitors or modulators of amyloid β-protein (Aβ) assembly in hope that they would lead to effective, disease-modifying therapy for Alzheimer's disease (AD). These compounds typically were either designed to break apart β-sheets or selected empirically. Two such compounds, the natural inositol derivative scyllo-inositol and the green-tea-derived flavonoid epigallocatechin gallate (EGCG), currently are in clinical trials. Similar to most of the compounds tested thus far, the mechanism of action of scyllo-inositol and EGCG is not understood. Recently, we discovered a novel family of assembly modulators, Lys-specific molecular tweezers, which act by binding specifically to Lys residues and modulate the self-assembly of amyloid proteins, including Aβ, into formation of nontoxic oligomers by a process-specific mechanism (Sinha, S., Lopes, D. H., Du, Z., Pang, E. S., Shanmugam, A., Lomakin, A., Talbiersky, P., Tennstaedt, A., McDaniel, K., Bakshi, R., Kuo, P. Y., Ehrmann, M., Benedek, G. B., Loo, J. A., Klarner, F. G., Schrader, T., Wang, C., and Bitan, G. (2011) Lysine-specific molecular tweezers are broad-spectrum inhibitors of assembly and toxicity of amyloid proteins. J. Am. Chem. Soc.133, 16958-16969). Here, we compared side-by-side the capability of scyllo-inositol, EGCG, and the molecular tweezer CLR01 to inhibit Aβ aggregation and toxicity. We found that EGCG and CLR01 had comparable activity whereas scyllo-inositol was a weaker inhibitor. Exploration of the binding of EGCG and CLR01 to Aβ using heteronuclear solution-state NMR showed that whereas CLR01 bound to the two Lys and single Arg residues in Aβ monomers, only weak, nonspecific binding was detected for EGCG, leaving the binding mode of the latter unresolved. 

Retracted: No

PubPeer comments:
 There appear to be issues with the representative dot blots shown in Figure 3 of this paper. ![file] First, for the loading control blots labeled with the 6E10 antibody, the blots shown for the control and CLR01 groups are duplicated for the EGCG and *scyllo*-inositol groups. (Compare the blots outlined in red to the blots outlined in blue.) ![file] Second, for the blots labeled with the A11 antibody, it appears from the white splotches (marked with red arrows) that the blots may have been manipulated to reduce the appearance of A11 reactivity in the EGCG group. (I have reduced the brightness and increased the contrast in the below image to make the splotches more apparent.) ![file] , 
 In addition to the issues noted above, Figure 3 of this paper contains images that are highly similar to the dot blots in a 2011 paper published by the same group. Link here: https: doi.org 10.1021 ja206279b Here is Figure 5, Panel A from the 2011 paper: ![file] Here is the top two rows of the A11 dot blots from Figure 5A, compared to the first two columns from Figure 3 in the 2012 paper. I rotated the 2012 image 90 degrees and flipped it horizontally. Note the similar elements highlighted in red, green, and blue. ![file] And here is the top two rows of the 6E10 loading control dot blots in Figure 5A, compared to the 6E10 loading control dot blots from Figure 3 of the 2012 paper. Again, I rotated the 2012 image 90 degrees and flipped it horizontally. I also darkened both images and resized the bottom image to highlight the similarities. ![file] , 
 Publication Date: August 24, 2022 Figure 3. Inhibition of Au03b242 oligomerization. Au03b2 oligomerization in the presence or absence of scyllo-inositol, EGCG, or CLR01 was probed using dot blots with polyclonal antibody A11. Identical membranes were probed using monoclonal antibody 6E10 as a loading control. First, in the dot blot probed by antibody 6E10, the image for EGCG and scyllo-inositol was a duplication of the image for the control condition (no compound) and CLR01. The corrected Figure is shown above. Second, the images for the control condition and CLR01 in both the dot blots (probed using antibodies A11 or 6E10) had been used previously (1) yet this was not mentioned in the paper by mistake. These images were reused for comparison with EGCG and scyllo-inositol. ![file] ,