Proteasome inhibition and mechanism of resistance to a synthetic, library-based hexapeptide

Construction and evaluation of detachable bone-targeting MOF carriers for the delivery of proteasome inhibitors

Tumor bone metastasis is an important cause of tumor recurrence and death. Although bone-targeting nanoparticles decorated with targeting ligands have shown good affinity for bone tissues with the properties of adhesion to the bone matrix, it is not easy to detach from the surface of the bone matrix in the tumor-bone microenvironment, attributed to the robust coordination force between the targeting ligands, such as bisphosphates with bone-deposited calcium. This may hinder the transport of nanoparticles from bone tissue to bone metastatic tumors. In this research, we designed a bone-targeting nanocarrier with detachable bone-targeting character for the therapy of bone metastases. The nanoparticles were constructed by using ZIF-8 and bone-targeting and MMP enzyme sensitive polypeptide-modified hyaluronic acid as a carrier and proteasome inhibitor Bortezomib (BTZ) as cargo. The results show that the constructed D8-M3-HA-ZIF8@BTZ nanoparticles possessed several favorable properties such as good colloidal stability, acid-sensitive drug release, D8 peptide mediated bone targeting and MMP enzyme-responsive desorption. Besides, nanoparticle endocytosis and cytotoxicity were enhanced through HA-mediated targeting to CD44 over-expressing tumor cells. Altogether, this study provides a potential cascade targeting strategy for improving the delivery effects of bone targeted nanoparticles for the delivery of proteasome inhibitors.

Tumor bone metastasis is an important cause of tumor recurrence and death.

Merging the Versatile Functionalities of Boronic Acid with Peptides

Peptides inherently feature the favorable properties of being easily synthesized, water-soluble, biocompatible, and typically non-toxic. Thus, boronic acid has been widely integrated with peptides with the goal of discovering peptide ligands with novel biological activities, and this effort has led to broad applications. Taking the integration between boronic acid and peptide as a starting point, we provide an overview of the latest research advances and highlight the versatile and robust functionalities of boronic acid. In this review, we summarize the diverse applications of peptide boronic acids in medicinal chemistry and chemical biology, including the identification of covalent reversible enzyme inhibitors, recognition, and detection of glycans on proteins or cancer cell surface, delivery of siRNAs, development of pH responsive devices, and recognition of RNA or bacterial surfaces. Additionally, we discuss boronic acid-mediated peptide cyclization and peptide modifications, as well as the facile chemical synthesis of peptide boronic acids, which paved the way for developing a growing number of peptide boronic acids.

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.

Antitumor Effect of Inula viscosa Extracts on DMBA-Induced Skin Carcinoma Are Mediated by Proteasome Inhibition

The aim of this work is to evaluate the antitumor effect mediated by the proteasome inhibitors of Inula viscosa extracts on skin carcinogenesis. Female Swiss albino mice were divided into five groups depending on the combination of skin cancer-inducing 7,12-dimethylbenz(a)anthracene (DMBA) and extract of Inula viscosa treatments. Histology of the affected skin and measurement of proteasome activity were performed to demonstrate the effect of Inula viscosa on mice. The identification of the molecules responsible for this inhibitory activity was carried out through the docking studies. The results showed that Inula viscosa extracts inhibit the development of papilloma in mice. Therefore, the best chemopreventive action of Inula viscosa was observed on mice in which extract treatment was performed before and after the induction of skin carcinogenesis. It was revealed that the ingestion of extracts Inula viscosa delays the formation of skin papillomas in animals and simultaneously decreases the size and number of papillomas, which is also reflected on the skin histology of the mice treated. Structure-activity relationship information obtained from component of Inula viscosa particularly tomentosin, inuviscolide, and isocosticacid demonstrated that distinct bonding modes in β ₁, β ₂, and β ₅ subunits determine its selectivity and potent inhibition for β ₅ subunit.

Viral entry and the ubiquitin-proteasome system

Viruses confiscate cellular components of the ubiquitin-proteasome system (UPS) to facilitate many aspects of the infectious cycle. The 26S proteasome is an ATP-dependent, multisubunit proteolytic machine present in all eukaryotic cells. The proteasome executes the controlled degradation of functional proteins, as well as the hydrolysis of aberrantly folded polypeptides. There is growing evidence for the role of the UPS in viral entry. The UPS assists in several steps of the initiation of infection, including endosomal escape of the entering virion, intracellular transport of incoming nucleocapsids and uncoating of the viral genome. Inhibitors of proteasome activity, including MG132, epoxomicin, lactacystin and bortezomib have been integral to developments in this area. Here, we review the mechanistic details of UPS involvement in the entry process of viruses from a multitude of families. The possibility of proteasome inhibitors as therapeutic antiviral agents is highlighted.

The γ-secretase inhibitor GSI-I interacts synergistically with the proteasome inhibitor bortezomib to induce ALK+ anaplastic large cell lymphoma cell apoptosis

Single agent treatment of the γ-secretase inhibitor (GSI-I) or proteasome inhibitor in anaplastic lymphoma kinase positive anaplastic large cell lymphoma (ALK+ ALCL) shows limited response and considerable toxicity. Here, we examined the effects of the combination of low dose GSI-I and the proteasome inhibitor bortezomib (BTZ) in ALK+ ALCL cells in vivo and in vitro. We found that ALK+ ALCL cells treated with the BTZ and GSI-I combination treatment showed elevated apoptosis, consistent with increased caspase activation, compared with BTZ or GSI-I alone. The combination treatment also inhibited AKT and extracellular signal-related kinase pathways, as well as stress-related cascades, including the c-jun N-terminal kinase and stress-activated kinases. Moreover, combined treatment in a murine xenograft model resulted in increased apoptosis in tumor tissues and reduced tumor growth. Our results reveal the synergistic anti-tumor effects of low dose inhibitors against γ-secretase and the proteasome and suggest the potential application of the tolerable BTZ/GSI-I combined agents in treating ALK+ ALCL in future clinical treatment.