Endoplasmic Reticulum-Associated Degradation (ERAD)

The newly synthesized proteins are kept in the endoplasmic reticulum (ER) until their maturation is completed. The accurate protein folding is vital for homeostasis, but this process is error-prone since it is chemically complicated. Aberrant folding may result in aggregates having a toxic gain of function or may lead to a loss of protein function; therefore, protein misfolding can lead to several pathologies. The ER protein quality control mechanism monitors the fidelity of protein folding. Those proteins that fail to fold or assemble properly are subjected to degradation via a process known as ER-associated degradation (ERAD). Besides clearing proteins having folding problems, ERAD is also known to regulate the levels of some physiological proteins including 3-hydroxy-3-methylglutaryl-coenzymeA reductase (HMGR) catalyzing the rate-limiting step of cholesterol biosynthesis. ERAD is a complex, multistep process starting with the recognition and targeting of substrates, followed by ubiquitination, retrotranslocation and proteasomal degradation. A large number of ERAD factors functioning in different molecular machineries increases the complexity of mammalian ERAD. ERAD is fundamental for human health and there is increasing evidence linking ERAD with various diseases. Here, the different modules/machineries of the ERAD process together with its tight regulation will be discussed

A new underlying mechanism for the neuroprotective effect of bosutinib: Reverting toxicity-induced PARylation in SIN1-mediated neurotoxicity

Increased levels of reactive oxygen and nitrogen species play an important role in the development and progression of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. The overproduction of these highly reactive chemical species leads to DNA damage and subsequent activation of the poly(ADP-ribose)polymerase (PARP) enzyme. Several studies have demonstrated the potential use of PARP inhibitors for neuroprotection. We previously reported that the dual Src/Abl kinase inhibitor bosutinib (BOS) decreases PARP activity and acts as a chemosensitizer in cancer cells. In this study, we evaluated the neuroprotective potential of BOS with respect to its inhibitory effect on cellular poly(ADP-ribos)ylation (PARylation) using a 3-morpholinosydnonimine (SIN1)-mediated cellular toxicity model. Our data suggest that pretreatment with BOS, especially at lower doses, significantly decreased the level of SIN1-induced cellular PARylation. This regulation pattern of PARylation was found to be associated with the protective effect of BOS against SIN1 on the viability of retinoic acid-differentiated SH-SY5Y cells. Furthermore, while PARP-1 expression was decreased, phosphorylation of SAPK/JNK was not reverted at the observed neuroprotective doses of BOS. In conclusion, we suggest a novel mechanism for the neuroprotective effect of BOS involving the inhibition of cellular PARylation.Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (BIDEB)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (BIDEB

The role of cycloastragenol at the intersection of NRF2/ARE, telomerase, and proteasome activity

Aging is well-characterized by the gradual decline of cellular functionality. As redox balance, proteostasis, and telomerase systems have been found to be associated with aging and age-related diseases, targeting these systems with small compounds has been considered a promising therapeutic approach. Cycloastragenol (CA), a small molecule telomerase activator obtained from Astragalus species, has been reported to positively affect several age-related pathophysiologies, but the mechanisms underlying CA activity have yet to be reported. Here, we presented that CA increased NRF2 nuclear localization and activity leading to upregulation of cytoprotective enzymes and attenuation of oxidative stress-induced ROS levels. Furthermore, CA-mediated induction of telomerase activity was found to be regulated by NRF2. CA not only increased the expression of hTERT but also its nuclear localization via upregulating the Hsp90-chaperon complex. In addition to modulating nuclear hTERT levels at unstressed conditions, CA alleviated oxidative stress-induced mitochondrial hTERT levels while increasing nuclear hTERT levels. Concomitantly, H2O2-induced mitochondrial ROS level was found to be significantly decreased by CA administration. Our data also revealed that CA strongly enhanced proteasome activity and assembly. More importantly, the proteasome activator effect of CA is dependent on the induction of telomerase activity, which is mediated by NRF2 system. In conclusion, our results not only revealed the cross-talk among NRF2, telomerase, and proteasome systems but also that CA functions at the intersection of these three major aging-related cellular pathways.Scientific and Technological Research Council of Turkey (TUBITAK) [119Z086]Funding This study was supported by Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 119Z086)

Synthesis and Bioactivity Studies of Some Naphthoquinone Derivatives as Potential Proteasome Inhibitors

The ubiquitine–proteasome pathway (UPP) plays. [...

Neuroprotective metabolites via fungal biotransformation of a novel sapogenin, cyclocephagenol

Cyclocephagenol (1), a novel cycloartane-type sapogenin with tetrahydropyran unit, is only encountered in Astragalus species. This rare sapogenin has never been a topic of biological activity or modification studies. The objectives of this study were; (i) to perform microbial transformation studies on cyclocephagenol (1) using Astragalus endophyte, Alternaria eureka 1E1BL1, followed by isolation and structural characterization of the metabolites; (ii) to investigate neuroprotective activities of the metabolites; (iii) to understand structure-activity relationships towards neuroprotection. The microbial transformation of cyclocephagenol (1) using Alternaria eureka resulted in the production of twenty-one (2-22) previously undescribed metabolites. Oxidation, monooxygenation, dehydration, methyl migration, epoxidation, and ring expansion reactions were observed on the triterpenoid skeleton. Structures of the compounds were established by 1D-, 2D-NMR, and HR-MS analyses. The neuroprotective activities of metabolites and parent compound (1) were evaluated against H2O2-induced cell injury. The structure-activity relationship (SAR) was established, and the results revealed that 1 and several other metabolites had potent neuroprotective activity. Further studies revealed that selected compounds reduced the amount of ROS and preserved the integrity of the mitochondrial membrane. This is the first report of microbial transformation of cyclocephagenol (1).This project was supported by Ege University Office of Scientific Research Projects (Project No: GAP-23729). We thank the Pharmaceutical Sciences Research Centre (FABAL, Ege University, Faculty of Pharmacy) for equipment support. We are very grateful to Bionorm Natural Products for providing cyclocephagenol and cycloastragenol.Ege University Office of Scientific Research Projects [GAP-23729

Evaluation of Alkylating and Intercalating Properties of Mannich Bases for Cytotoxic Activity

WOS: 000341643300006A series of new "hybrid compounds", Mannich base derivatives of planar polycyclic/heterocyclic starting materials, was designed and synthesized. The structures of the compounds were confirmed by spectroscopic methods and elemental analysis. Cytotoxicity of compounds was investigated in three cancer cell lines (PC3, HeLa, and MCF7) and one non-tumoral cell line (293 HEK). We tested the DNA-intercalating capability of the molecules by ethidium bromide (EtBr) fluorescence displacement experiment. Compounds' alkylation potency was investigated via in vitro incubation test using 2-mercaptoethanol, a biomimetic nucleophile. The five of the compounds (7s, 9d, 10b, 11b, 12c) are reported for first time in the literature. Our results suggest that compound 9d has a biological activity close to the reference compound doxorubicin, an intercalating agent in clinical use.TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110S082]; [09ECZ016]The authors would like to thank 110S082 TUBITAK and 09ECZ016, for providing financial support and infrastructure

Non-apoptotic cell death induction via sapogenin based supramolecular pArticles

The discovery of novel chemotherapeutics that act through different mechanisms is critical for dealing with tumor heterogeneity and therapeutic resistance. We previously reported a saponin analog (AG-08) that induces non-canonical necrotic cell death and is auspicious for cancer therapy. Here, we describe that the key element in triggering this unique cell death mechanism of AG-08 is its ability to form supramolecular pArticles. These self-assembled pArticles are internalized via a different endocytosis pathway than those previously described. Microarray analysis suggested that AG-08 supramolecular structures affect several cell signaling pathways, including unfolded protein response, immune response, and oxidative stress. Finally, through investigation of its 18 analogs, we further determined the structural features required for the formation of particulate structures and the stimulation of the unprecedented cell death mechanism of AG-08. The unique results of AG-08 indicated that supramolecular assemblies of small molecules are promising for the field of anticancer drug development, although they have widely been accepted as nuisance in drug discovery studies.Scientific and Technological Research Council of Turkey (TUBITAK) [118S709]; Scientific Research Projects Coordination Unit of Izmir Institute of Technology (IZTECH BAP) [2017IYTE71]We are very grateful to Bionorm Natural Products for donating CG, AG-01, CG-01, and SCG, and Doc. Dr. Rukan Genc Alturk for donating Nile red. Also, we thank the Pharmaceutical Sciences Research Centre (FABAL, Ege University, Faculty of Pharmacy) and Biotechnology and Bioengineering Application and Research Centre (BIYOMER, zmir Institute of Technology) for equipmental support. Additionally, we thank Izmir Biomedicine and Genome Center (IBG) for STEM microscope analysis. This project was supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Project No: 118S709) and Scientific Research Projects Coordination Unit of Izmir Institute of Technology (IZTECH BAP, Project No: 2017IYTE71)

Identification of a Noncanonical Necrotic Cell Death Triggered via Enhanced Proteolysis by a Novel Sapogenol Derivative

Kirmizibayrak, Petek Ballar/0000-0002-6189-1818; Bedir, Erdal/0000-0003-1262-063XWOS:000599310100019PubMed: 33136369Small molecules which activate distinct cell death pathways have promising high potential for anticancer drug research. Especially, regulated necrosis draws attention as an alternative cell death mechanism to overcome the drug resistance. Here, we report that a new semisynthetic saponin analogue (AG-08) triggers necrotic cell death with unprecedented pathways. AG-08-mediated necrosis depends on enhanced global proteolysis involving calpains, cathepsins, and caspases. Moreover, AG-08 generates several alterations in lysosomal function and physiology including membrane permeabilization, redistribution toward the perinuclear area, and lastly excessive tubulation. As a consequence of lysosomal impairment, the autophagic process was abolished via AG-08 treatment. Collectively, in addition to its ability to induce necrotic cell death, which makes AG-08 a promising candidate to cope with drug resistance, its unique activity mechanisms including autophagy/lysosome impairment and enhancement of proteolysis leading a strong death capacity emphasizes its potential for anticancer drug research.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [118S709, 109S345]This project was supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Project No: 118S709) as a continuation of a prior project (TUBITAK, Project No: 109S345)

Design, Synthesis and Evaluation of the Biological Activities of Some New Carbohydrazide and Urea Derivatives

WOS: 000450780900010Objectives: Urea and carbohydrazide derivatives are important compounds exhibiting cytotoxic activities. In this study, a series of new urea and carbohydrazide derivatives containing an pyridine ring were synthesized and evaluated for cytotoxic activity. Materials and Methods: The proposed structures of the synthesized compounds were confirmed using elemental analysis, IR, and H-1-NMR spectroscopic techniques. The cytotoxic potencies of synthesized compounds were determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) on BRCA mutant-carrying HCC1937 and Capan-1 cell lines, as well as on MCF7, HeLa, and MRC5 cells. Results: 3a, 3b, 3c and 3d showed cytotoxic activity against all cancer cell lines. Conclusion: Our data indicate that compounds 3a-d are more selective to cancer cells compared with nontumoral fibroblasts; however, these compounds are not more potent on HR defective cells with BRCA mutants.TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [215S112]; Marmara University Scientific Research CommissionMarmara University [SAG-C-DRP-100616-0260]This study was supported by TUBITAK 215S112 and Marmara University Scientific Research Commission (project number: SAG-C-DRP-100616-0260)