Simon Ebbinghaus, Ph.D. Ruhr-University, Bochum, Germany
Simon Ebbinghaus is a Juniorprofessor at the Ruhr-University Bochum, Germany since 2011. Previously, he was a postdoc with Martin Gruebele at the University of Illinois, Urbana-Champaign between 2008-2010). He received his Ph.D. (Dr. rer. nat.) at the Ruhr-University Bochum in 2007.
Using in-cell temperature jumps, the Ebbinghaus group applies new techniques to study folding and aggregation kinetics in a single living cells (Ebbinghaus et al., Nature Methods 2010). Our lab has investigated how molecular tweezers act on protein aggregation pathways.
In a recent study, in collaboration with the Sanchez-Garcia group, we found that CLR01 inhibited the formation of protein aggregates formed by the huntingtin protein (Htt), which are implicated in Huntongton’s disease (HD) (Vöpel et al., J. Am. Chem. Soc. 2017). Our study used the N-terminal part of the Htt protein with the expanded polyglutamine sequence that causes the mutant protein to self-associate into neurotoxic oligomers and aggregates. We found that CLR01 perturbed the structure of a key amino-acid sequence of the protein, called N17 and thereby prevented the molecular interactions that lead to Htt aggregation. Importantly, we could demonstrate that CLR01 inhibited the aggregation of Htt not only in the test tube, but also in living cells.
The inhibition of the aggregation of the mutant Htt protein with an expanded polyglutamine sequence was surprising because CLR01 binds to lysine and arginine residues, which are absent in the expended ployglutamine sequence. It turned out that the existence of three lysines in the N17 sequence, which is immediately adjacent to the polyglutamine sequence, was sufficient to allow CLR01 to inhibit the aggregation of the mutant Htt protein. This discovery has implications for therapy development, not only for HD, but also for other diseases in which mutant polyglutamine sequences cause proteins to aggregate and become toxic, such as fragile-X syndrome and different forms of spinocerebellar ataxia.
Figure 1. Left: The three-dimensional structure of the N17 sequence, which is crucial for mutant Htt aggregation, shows that hydrophobic amino acids (blue) align on one side. This clustering of the hydrophobic amino acids creates a sticky surface that promotes aggregation of these molecules with each other. CLR01 pertubes the structure and breakes the large hydrophobic surface into smaller ones. Right: Measurement of the aggregation time in live cells shows that in the presence of CLR01, but not the negative-control derivative, CLR03, a key step of the aggregation of the mutant Htt protein is delayed from 200 minutes to 800 minutes.