Role of Mono- and Divalent Ions in Peptide Glu-Asp-Arg-DNA Interaction

Neuroepigenetic Mechanisms of Action of Ultrashort Peptides in Alzheimer's Disease

Epigenetic regulation of gene expression is necessary for maintaining higher-order cognitive functions (learning and memory). The current understanding of the role of epigenetics in the mechanism of Alzheimer’s disease (AD) is focused on DNA methylation, chromatin remodeling, histone modifications, and regulation of non-coding RNAs. The pathogenetic links of this disease are the misfolding and aggregation of tau protein and amyloid peptides, mitochondrial dysfunction, oxidative stress, impaired energy metabolism, destruction of the blood–brain barrier, and neuroinflammation, all of which lead to impaired synaptic plasticity and memory loss. Ultrashort peptides are promising neuroprotective compounds with a broad spectrum of activity and without reported side effects. The main aim of this review is to analyze the possible epigenetic mechanisms of the neuroprotective action of ultrashort peptides in AD. The review highlights the role of short peptides in the AD pathophysiology. We formulate the hypothesis that peptide regulation of gene expression can be mediated by the interaction of short peptides with histone proteins, cis- and transregulatory DNA elements and effector molecules (DNA/RNA-binding proteins and non-coding RNA). The development of therapeutic agents based on ultrashort peptides may offer a promising addition to the multifunctional treatment of AD.

Peptide Regulation of Gene Expression: A Systematic Review

Peptides are characterized by their wide range of biological activity: they regulate functions of the endocrine, nervous, and immune systems. The mechanism of such action of peptides involves their ability to regulate gene expression and protein synthesis in plants, microorganisms, insects, birds, rodents, primates, and humans. Short peptides, consisting of 2-7 amino acid residues, can penetrate into the nuclei and nucleoli of cells and interact with the nucleosome, the histone proteins, and both single- and double-stranded DNA. DNA-peptide interactions, including sequence recognition in gene promoters, are important for template-directed synthetic reactions, replication, transcription, and reparation. Peptides can regulate the status of DNA methylation, which is an epigenetic mechanism for the activation or repression of genes in both the normal condition, as well as in cases of pathology and senescence. In this context, one can assume that short peptides were evolutionarily among the first signaling molecules that regulated the reactions of template-directed syntheses. This situation enhances the prospects of developing effective and safe immunoregulatory, neuroprotective, antimicrobial, antiviral, and other drugs based on short peptides.

Structures and Dissociation Products of Ce/Peptide Complexes: Competition between Coordination and Charge Delocalization

Structures of [Ce(GGG)]³⁺ and [Ce(GGG ? H)]²⁺ have been investigated by DFT calculations. The two lowest-energy structures of the triply charged metal complex have the peptide in either the iminol or conventional zwitterionic form, and these ions have almost identical energies. In the doubly charged complex, the iminol and charge-solvated structures are the best structures on the potential energy surface, but the latter is favored. In both iminol structures, the metal ion coordinates to the iminol oxygen rather than to the nitrogen, unlike in previously reported iminol-containing complexes. Triply charged [Ce(peptide)]³⁺ complexes are fragile and not easily isolated in a mass spectrometer, whereas the doubly charged [Ce(peptide ? H)]²⁺ complexes are more robust. Here, we studied the fragmentations of 37 [Ce(peptide ? H)]²⁺ and 30 [Ce(peptide)(peptide ? H)]²⁺ complexes and the results are systematically summarized. Losses of CO and/or H₂O are the most commonly observed fragmentation channels for [Ce(peptide ? H)]²⁺ complexes and these dissociation pathways are modeled by DFT calculations. For [Ce(peptide)(peptide ? H)]²⁺ complexes the neutral peptide plays the role of a solvent molecule but, unlike in the dissociations of [Ce(CH₃CN)(peptide ? H)]²⁺ complexes, the loss of the solvent molecule is not observed. Instead, fragmentation occurs by cleavage of the second amide bond of the solvating peptide molecule.