Rpt5-Derived Analogs Stimulate Human Proteasome Activity in Cells and Degrade Proteins Forming Toxic Aggregates in Age-Related Diseases.

Aging and age-related diseases are associated with a decline in the capacity of protein turnover. Intrinsically disordered proteins, as well as proteins misfolded and oxidatively damaged, prone to aggregation, are preferentially digested by the ubiquitin-independent proteasome system (UIPS), a major component of which is the 20S proteasome. Therefore, boosting 20S activity constitutes a promising strategy to counteract a decrease in total proteasome activity during aging. One way to enhance the proteolytic removal of unwanted proteins appears to be the use of peptide-based activators of the 20S. In this study, we synthesized a series of peptides and peptidomimetics based on the C-terminus of the Rpt5 subunit of the 19S regulatory particle. Some of them efficiently stimulated human 20S proteasome activity. The attachment of the cell-penetrating peptide TAT allowed them to penetrate the cell membrane and stimulate proteasome activity in HEK293T cells, which was demonstrated using a cell-permeable substrate of the proteasome, TAS3. Furthermore, the best activator enhanced the degradation of aggregation-prone α-synuclein and Tau-441. The obtained compounds may therefore have the potential to compensate for the unbalanced proteostasis found in aging and age-related diseases.

Peptidomimetics Based on C-Terminus of Blm10 Stimulate Human 20S Proteasome Activity and Promote Degradation of Proteins.

Degradation of misfolded, redundant and oxidatively damaged proteins constitutes one of the cellular processes which are influenced by the 20S proteasome. However, its activity is generally thought to decrease with age which leads to the gradual accumulation of abnormal proteins in cells and their subsequent aggregation. Therefore, increasing proteasomal degradation constitutes a promising strategy to delay the onset of various age-related diseases, including neurodegenerative disorders. In this study we designed and obtained a series of peptidomimetic stimulators of 20S comprising in their sequences the C-terminal fragment of Blm10 activator. Some of the compounds were capable of enhancing the degradation of natively unfolded and oxidatively damaged proteins, such as α-synuclein and enolase, whose applicability as proteasome substrates was evaluated by microscale thermophoresis (MST). Furthermore, they increased the ChT-L activity of the proteasome in HEK293T cell extracts. Our studies indicate that the 20S proteasome-mediated protein substrates hydrolysis may be selectively increased by peptide-based stimulators acting in an allosteric manner. These compounds, after further optimization, may have the potential to counteract proteasome impairment in patients suffering from age-related diseases.

Novel chalcone-derived pyrazoles as potential therapeutic agents for the treatment of non-small cell lung cancer.

Lung cancer is considered to account for approximately one-fifth of all malignant tumor-related deaths worldwide and is therefore one of the most lethal malignancies. Pyrazole scaffold possesses a wide range of biological and pharmacological activities, which play important roles in medicinal chemistry. The present study reports the synthesis and in vitro biological characterization of nine pyrazoles derived from chalcones as potential anticancer agents for non-small cell lung cancer A-549, H226, and H460 cell lines. Most of the compounds efficiently inhibited the growth of all the tested cancer cell lines at micromolar concentrations. One of the most active compounds (PCH-1) was further evaluated for its effect on cell cycle distribution, apoptosis, migration, epithelial-mesenchymal transition, and oxidative stress. Furthermore, studies on the mechanism of action revealed that PCH-1 disrupts microtubule assembly, leading to cancer cell death. Molecular modeling studies confirmed the potent interaction of PCH-1 with the vinblastine binding site on tubulin. Overall, this study provides novel opportunities to identify anticancer agents in the pyrazole series.

Nostocyclopeptides as New Inhibitors of 20S Proteasome.

Nostocyclopeptides (Ncps) are a small class of bioactive nonribosomal peptides produced solely by cyanobacteria of the genus Nostoc. In the current work, six Ncps were isolated from Nostoc edaphicum strain CCNP1411. The bioactivity of these compounds was tested in vitro against 20S proteasome, a proteolytic complex that plays an important role in maintaining cellular proteostasis. Dysfunction of the complex leads to many pathological disorders. The assays indicated selective activity of specific Ncp variants. For two linear peptide aldehydes, Ncp-A2-L and Ncp-E2-L, the inhibitory effects on chymotrypsin-like activity were revealed, while the cyclic variant, Ncp-A2, inactivated the trypsin-like site of this enzymatic complex. The aldehyde group was confirmed to be an important element of the chymotrypsin-like activity inhibitors. The nostocyclopeptides, as novel inhibitors of 20S proteasome, increased the number of natural products that can be considered potential regulators of cellular processes.