Daniel Segal, Ph.D.
Tel Aviv University

Protein misfolding – role in disease and potential therapeutic target

Conformational diseases are characterized by misfolding of a specific protein, leading to loss of its function, as well as to clustering of the misfolded monomers into toxic aggregates and fibrils. Best known are Aβ and tau protein in Alzheimer’s disease and α-synuclein in Parkinson’s disease, which accumulate in the brain as harmful amyloid deposits. We use a variety of techniques and biological systems to identify natural and synthetic bioactive compounds for inhibiting the misfolding and aggregations of these proteins.

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Using biophysical know-how and computational structural biology approaches we design novel compounds as candidate inhibitors of the toxic aggregates of various amyloidogenic proteins associated with neurodegenerative diseases, e.g., Aβ, tau and α-synuclein mentioned above, as well as TDP-43 (involved in amyotrophic lateral sclerosis (ALS) and amylin (involved in Type-2 diabetes). Comparable deleterious aggregates are typical also of certain cancers (e.g., p53 in various types of malignancies; and pVHL in the von-Hippel-Lindau syndrome).

We examine the ability of the candidate compounds to inhibit in vitro aggregations of the amyloidogenic peptides using a variety of assays based on spectrophotometry, including absorbance, ThT fluorescence, circular dichroism, differential light scattering, differential calorimetry, gel-based assays, and electron microscopy. We also examine the ability of the candidate compounds to inhibit the cytotoxic effects of the amyloidogenic peptides towards cells in culture (MTT viability assay).

Study of molecular tweezers’ impact on mutant p53 aggregation and toxicity

Recently, we studied the effect of the molecular tweezer, CLR01, on the aggregation and toxicity of mutant p53 variants known to cause cancer. Our study showed that CLR01 stabilized intermediate-size assemblies that had high ThT fluorescence but were not fibrillar. Stabilization of these intermediate structures was evident by the acceleration of early self-assembly of the p53 mutants and attenuation of further aggregation. The interaction with CLR01 prevented the toxicity of the p53 mutant aggregates. The study was featured in the Spotlights of Chemical Research in Toxicology.

Selected list of recent publications

  1. Herzog, G., Shmueli, M.D., Levi, L., Engel, L., Gazit, E., Klärner, F.-G., Schrader, T., Bitan, G., and Segal, D. (2015) The Lys-specific molecular tweezer, CLR01, modulates aggregation of mutant p53 DNA binding domain and inhibits its toxicity, Biochemistry, 54: 3729–3738.
  2. Scherzer-Attali, R, Pellarin, R., Marino Convertino, M., Frydman-Marom, A., Egoz-Matia, N., Peled, S., Levy-Sakin, M., Shalev, DE., Caflisch, A., Gazit, E., and Segal, D. (2010). Complete Phenotypic Recovery of Alzheimer’s Disease Model by a Quinone-Tryptophan Hybrid Aggregation Inhibitor. PLoS One 5: e11101.
  3. Shaltiel-Karyo, R., Frenkel-Pinter, M., Frydman-Marom, A., Shalev, D.E., Segal, D. and Gazit, E. (2010). Inhibition of a-synuclein oligomerization by stable cell-penetrating b-synuclein fragments results in phenotypic recovery of Parkinson’s disease model flies. PLoS One 5(11):e13863.
  4. Frydman-Marom, A., Levin, A., Farfara, D., Benromano, T., Scherzer-Attali, R., Peled, S., Vassar, R., Segal, D., Gazit, E., Frenkel, D., and Ovadia, M. (2011). Orally administrated cinnamon extract reduces b-amyloid oligomerization and corrects cognitive impairment in Alzheimer’s disease animal models. PLoS One, 6(1): e16564.