Inhibition of Prion Propagation by 3,4-Dimethoxycinnamic Acid Ivan Zanyatkin, 1 Yulia Stroylova, 1,2 Sofia Tishina, 1 Victor Stroylov, 3 Aleksandra Melnikova, 1 Thomas Haertle 4 and Vladimir Muronetz 1 * 1 Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow StateUniversity, Moscow, Leninskye gory, 1/40, 119234, Russia 2 Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Trubetskaya St. 8, Bldg. 2, 119991, Moscow, Russia 3 Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, MoscowLeninsky Prospect, 47, 119991, Russia 4 UR 1268 Biopolymères Interactions Assemblages, INRA, équipe Fonctions et Interactions des Protéines, B.P. 71627, 44316, Nantes, Cedex 3, France Neurodegenerative diseases are associated with accumulation of amyloid-type protein misfolding products. Prion protein (PrP) is known for its ability to aggregate into soluble oligomers that in turn associate into amyloid fibrils. Preventing the formation of these infective and neurotoxic entities represents a viable strategy to control prion diseases. Numerous attempts to find dietary compounds with anti-prion properties have been made; however, the most promising agent found so far was curcumin, which is poorly soluble and merely bioavailable. In the present work, we identify 3,4-dimethoxycinnamic acid (DMCA) which is a bioavailable coffee component as a perspective anti-prion compound. 3,4-Dimethoxycinnamic acid was found to bind potently to prion protein with a Kd of 405 nM. An in vitro study of DMCA effect on PrP oligomerization and fibrillization was undertaken using isothermal titration calorimetry (ITC), dynamic light scattering (DLS) and circular dichroism (CD) methodologies. We demonstrated that DMCA affects PrP oligomer formation reducing the oligomer content by 30–40%, and enhancing SH-SY5Y cell viability treated with prion oligomers. Molecular docking studies allowed to suggest a site where DMCA is able to bind stabilizing PrP tertiary structure. We suggest that DMCA is a perspective dietary compound for prophylaxis of neurodegenerative diseases that needs further research. Copyright © 2017 John Wiley & Sons, Ltd. Keywords: prion protein; amyloid aggregation; 3,4-dimethoxycinnamic acid; coffee metabolites. INTRODUCTION Conversion of a prion protein (PrP) into its amyloid form is known to cause such neurodegenerative diseases as Creutzfeldt–Jacob’s syndrome, fatal familial insomnia, kuru and scrapie (Prusiner and DeArmond, 1990). During such conversion, PrP experiences considerable structural changes: 2 alpha-helices in C-terminal domain are thought to unwind, exposing hydrophobic residues to bulk solvent and finally converting into one β-strand (Pan et al., 1993). The resulting molecule is called a prion and possesses amyloidogenic and infective properties. Prion monomers can interact via newly formed β-strands, consecutively forming intermediate oligomers (Rezaei et al., 2005), and finally the amyloid fibrils (Breydo et al., 2008a). The former are considered to be the most dangerous and infectious prion form (Silveira et al., 2005; Simoneau et al., 2007). Accumulation of such aggregates is considered to cause vacuolization, transport degradation and death of neuronal cells (Polyakova et al., 2009). Lack of effective therapy and lethality of such diseases arise from such factors as prolonged incubation period, cumulative onset of pathology and difficult diagnostics. No effective treatment of prion diseases is known by now, despite considerable effort taken in this direction. Therefore, search for safe compounds capable of preventing prion pathological aggregation among dietary compounds and their metabolites is of considerable interest (Ferreira et al., 2012; Attanasio et al., 2013). In the present work, a molecular docking approach was taken to screen a KEGG database of natural compounds for putative amyloid conversion inhibitors, and the found candidate—3,4-dimethoxycinnamic acid (DMCA)—was tested in in vitro protein and cellular assays. Hydroxycinnamic acid derivatives including DMCA are known to be a component of coffee beans; however, DMCA is of special interest as it is contained in coffee as an aglycone, as opposed to numerous related compounds, and can be detected in plasma after consumption of coffee. Peak plasma concentration of DMCA was shown to reach 380 nM after 60 min from a coffee drink (Nagy et al., 2011). Interestingly, while DMCA and ferulic acid are both found in coffee beans in 3:100 ratio, plasma ratio amounts to 24:100, which can be caused by catechol O-methyl transferase mediated O-methylation. It is also possible, that upon oral consumption of coffee in humans, naturally abundant quinyl dimethoxycinnamates are hydrolyzed more rapidly than their quinyl caffeate analogs (Nagy et al., 2011). Moreover, coffee consumption is known to * Correspondence to: Vladimir I. Muronetz, Belozersky Institute of Physico-Chemical Biology and Faculty of Bioengineering and Bioinformatics, Moscow State University, 119234 Moscow, Russia. E-mail: vimuronets@belozersky.msu.ru PHYTOTHERAPY RESEARCH Phytother. Res. (2017) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ptr.5824 Copyright © 2017 John Wiley & Sons, Ltd. Received 13 November 2016 Revised 01 April 2017 Accepted 05 April 2017