Structural and biochemical basis of apoptotic activation by Smac/DIABLO

SNAr-Based Labeling of Proteins with Trityl Radicals Enables High-Precision, High-Sensitivity, and Long-Range Distance Measurement

Distance measurement using pulsed dipolar electron paramagnetic resonance spectroscopy (PD-EPR) coupled with site-directed spin labeling is a powerful approach to study the structure and dynamics of biomolecules in nearly native environments. However, the accuracy and sensitivity of the distance measurement in cellular systems is often limited by long, flexible, and/or reduction-sensitive linker of spin labels and their low biostability. Herein, we report the first class of aryl-linked trityl spin labels in which pyrimidine and pyridine methylsulfones (FPS1-2) act as protein tagging groups and are directly conjugated to the trityl moiety. FPS1 underwent a specific nucleophilic aromatic substitution (SNAr) reaction with cysteine (Cys) as its free form or in glutathione (GSH) and proteins to produce stable C-S conjugation. The resulting conjugates experienced negligible hydrolysis after a long-term measurement and exhibited high biostability to the commonly used reducing agents and also in cell lysates, which is in contrast to the conjugates of the maleimide spin label, CT02MA. PD-EPR studies on the FPS1-labeled immunoglobulin G-binding protein (GB1) and second-mitochondrion-derived activator of caspases (Smac) demonstrated that FPS1 enables highly sensitive and long-range distance measurement in the proteins. Importantly, due to its short and rigid aryl linker, the use of FPS1 provides significantly narrower distance distributions than those from the maleimide spin labels CT02MA and OXMA. Moreover, using FPS1, the longest distance measurement (∼6.01 nm) so far in all of the trityl-labeled protein samples has also been achieved in the FPS1-labeled Smac. Overall, this work demonstrates that the SNAr-based aryl groups can be ideally united into the skeleton of trityl radicals, and the resulting spin labels enable sensitive, precise, and ultralong distance measurements in proteins under diverse conditions.

Peptide-modified nanoparticles for doxorubicin delivery: Strategies to overcome chemoresistance and perspectives on carbohydrate polymers

Chemotherapy serves as the primary treatment for cancers, facing challenges due to the emergence of drug resistance. Combination therapy has been developed to combat cancer drug resistance, yet it still suffers from lack of specific targeting of cancer cells and poor accumulation at the tumor site. Consequently, targeted administration of chemotherapy medications has been employed in cancer treatment. Doxorubicin (DOX) is one of the most frequently used chemotherapeutics, functioning by inhibiting topoisomerase activity. Enhancing the anti-cancer effects of DOX and overcoming drug resistance can be accomplished via delivery by nanoparticles. This review will focus on the development of peptide-DOX conjugates, the functionalization of nanoparticles with peptides, the co-delivery of DOX and peptides, as well as the theranostic use of peptide-modified nanoparticles in cancer treatment. The peptide-DOX conjugates have been designed to enhance the targeted delivery to cancer cells by interacting with receptors that are overexpressed on tumor surfaces. Moreover, nanoparticles can be modified with peptides to improve their uptake in tumor cells via endocytosis. Nanoparticles have the ability to co-deliver DOX along with therapeutic peptides for enhanced cancer treatment. Finally, nanoparticles modified with peptides can offer theranostic capabilities by facilitating both imaging and the delivery of DOX (chemotherapy).

Sustained cancer-relevant alternative RNA splicing events driven by PRMT5 in high-risk neuroblastoma

Protein arginine methyltransferase 5 (PRMT5) is over-expressed in a wide variety of cancers and is implicated as having a key oncogenic role, achieved in part through its control of the master transcription regulator E2F1. We investigated the relevance of PRMT5 and E2F1 in neuroblastoma (NB) and found that elevated expression of PRMT5 and E2F1 occurs in poor prognosis high-risk disease and correlates with an amplified Myelocytomatosis viral-related oncogene, neuroblastoma-derived (MYCN) gene. Our results show that MYCN drives the expression of splicing factor genes that, together with PRMT5 and E2F1, lead to a deregulated alternative RNA splicing programme that impedes apoptosis. Pharmacological inhibition of PRMT5 or inactivation of E2F1 restores normal splicing and renders NB cells sensitive to apoptosis. Our findings suggest that a sustained cancer-relevant alternative RNA splicing programme desensitises NB cells to apoptosis, and identify PRMT5 as a potential therapeutic target for high-risk disease.

Inducing apoptosis in acute myeloid leukemia; mechanisms and limitations

Acute myeloid leukemia is the expansion of leukemic stem cells which might originate from a stem cell or a progenitor which has acquired self-renewal capacity. An aggregation of leukemic blasts in bone marrow, peripheral blood, and extramedullary tissue will result in acute myeloid leukemia. The main difficulty in treating acute myeloid leukemia is multidrug resistance, leading to treatment failure. This unfortunate phenomenon is practically elevated because of apoptosis inhibition in tumor cells. Two general apoptotic pathways are the Bcl-2 regulated pathway (the intrinsic pathway) and the death receptor pathway. Deficiencies in each of these apoptotic pathways can cause the usual resistance mechanism in this disease. This article reviews and highlights different antiapoptotic pathways, currently-used treatments, and new findings in this field, which may lead to the development of treatment methods for acute myeloid leukemia.

Drug Discovery Approaches to Target E3 Ligases

Targeting E3 ligases is a challenging area in drug discovery. Despite the human genome encoding for more than 600 E3 ubiquitin ligases, only a handful of E3 ligases have been pharmacologically modulated or exploited for targeted protein degradation (TPD) strategies. The main obstacle for hijacking these E3 ligases is the lack of small-molecule ligands. As research into this field advances, the identification of new small molecules capable of binding to E3 ligases has become an essential pursuit. These ligases not only expand the repertoire of druggable targets but also offer the potential for increased specificity and selectivity in protein degradation. The synergy between academia and industry is key, as it combines academic expertise in fundamental research with the industrial capabilities of translating these findings into novel therapeutics. In this review, we provide an overview of the different strategies employed in academia and industry to the discovery of new E3 ligases ligands, showing them with illustrative cases.

A Comprehensive Insight into Apoptosis: Molecular Mechanisms, Signaling Pathways, and Modulating Therapeutics

Apoptosis, or programmed cell death, is a fundamental biological process essential for maintaining tissue homeostasis. Dysregulation of apoptosis is implicated in a variety of diseases, including cancer, neurodegenerative disorders, and autoimmune conditions. This review provides an in-depth insight into the molecular mechanisms and signaling pathways that regulate apoptosis, highlighting both intrinsic and extrinsic pathways. Additionally, the review explains the tumor microenvironment's influence on apoptosis and its implications for cancer therapy resistance. Understanding the complex interplay between apoptotic signaling and cellular responses is crucial for developing targeted therapies that can effectively manage diseases associated with apoptosis dysregulation. The effects of conventional therapeutics and alternative substances with natural sources such as herbal compounds, alongside vitamins, minerals, and trace elements on cellular homeostasis and disease pathogenesis have been thoroughly investigated. Moreover, recent advances in therapeutic strategies aimed at modulating apoptosis are discussed, with a focus on novel interventions such as nutrition bio shield dietary supplement. These emerging approaches offer potential benefits beyond conventional treatments by selectively targeting apoptotic pathways to inhibit cancer progression and metastasis. By integrating insights from recent studies, this review aims to enhance our understanding of apoptosis and guide future research in developing innovative therapeutic approaches.

Examining the potential causal relationships among smoking behaviors, blood DNA methylation profiles, and the development of coronary heart disease and myocardial infarction

BACKGROUND

Smoking has been identified as a standalone risk factor for coronary heart disease (CHD) and myocardial infarction (MI), but the precise underlying mechanisms remain incompletely elucidated.

RESULTS

In this study, we conducted a two-sample Mendelian randomization analysis to examine the impact of smoking behaviors (including smoking initiation, age of smoking initiation, cigarettes per day, and smoking cessation) and smoking-related DNA methylation at CpG sites on CHD and MI based on the UK Biobank dataset. Additionally, we included the FinnGen and Biobank Japan datasets as replications and performed a meta-analysis to combine the results from different data sources. We further validated our results using genetic colocalization analysis. In genomic analysis, we provided compelling evidence on the association between genetically predicted smoking initiation and increased susceptibility to CHD and MI. In epigenetic analysis, we identified 11 smoking-related CpG sites linked to CHD risk and 10 smoking-related CpG sites associated with the risk of MI based on the UK Biobank dataset. Subsequently, some of these CpG sites were further replicated using the FinnGen or BBJ datasets. Ultimately, a meta-analysis was conducted to integrate findings from various data sources (3 for CHD, and 2 for MI), revealing that 7 of 11 CpG sites were linked to CHD risk; whereas, 7 of 10 CpG sites were associated with MI risk. Furthermore, we performed genetic colocalization analysis and found that cg19744173 (FBLN7), cg00395063 (ARHGEF12), and cg16822035 (MCF2L) exhibited robust evidence of colocalization with coronary heart disease; whereas, cg19529732 (DIABLO), cg26405020 (FES), and cg08940075 (CNN3) demonstrated strong colocalization evidence with the risk of myocardial infarction.

CONCLUSIONS

Our research offers a novel insight into the impact of smoking on the susceptibility to CHD and MI through the lens of epigenetic DNA methylation.

Metals at the Helm: Revolutionizing Protein Assembly and Applications

Protein assembly is an essential process in biological systems, where proteins self-assemble into complex structures with diverse functions. Inspired by the exquisite control over protein assembly in nature, scientists have been exploring ways to design and assemble protein structures with precise control over their topologies and functions. One promising approach for achieving this goal is through metal coordination, which utilizes metal-binding motifs to mediate protein-protein interactions and assemble protein complexes with controlled stoichiometry and geometry. Metal coordination provides a modular and tunable approach for protein assembly and de novo structure design, where the metal ion acts as a molecular glue that holds the protein subunits together in a specific orientation. Metal-coordinated protein assemblies have shown great potential for developing functional metalloproteinase, novel biomaterials and integrated drug delivery systems. In this review, an overview of the recent advances in protein assemblies benefited from metal coordination is provided, focusing on various protein arrangements in different dimensions including protein oligomers, protein nanocage and higher-order protein architectures. Moreover, the key metal-binding motifs and strategies used to assemble protein structures with precise control over their properties are highlighted. The potential applications of metal-mediated protein assemblies in biotechnology and biomedicine are also discussed.

A comparative anticancer analysis of iron oxide nanoparticles of Hippophae rhamnoides and Cichorium intybus found in the Karakoram Range of Gilgit Baltistan against liver cancer targeting the RhoA gene

OBJECTIVE

The current research work focused on the evaluation of of H. rhamnoides and C. intybus Fe2O3 NPs against liver cancer cell line (HepG2) by performing antiproliferative assay targeting the RhoA gene and apoptotic pathway genes and proteins.

METHODS

Fe2O3 NPs were synthesized using extracts of H. rhamnoides and C. intybus and characterized by UV-Vis spectroscopy, FTIR, SEM/EDS and XRD. MTT assay was used to study cytotoxicity against the HepG2 cells. Real-time qPCR and ELISA were used for the gene and protein analysis.

RESULTS

An absorbance peak at 300 nm for H. rhamnoides and 289 nm for C. intybus nanoparticles were observed by UV-Vis analysis. The FTIR bands of H. rhamnoide Fe2O3 NPs suggested the presence of aldehydes, alcohols and polyols whereas bands of C. intybus Fe2O3 NPs suggested the presence of carboxyl groups, hydroxyl groups, alkynes and amines. The size of Fe2O3 NPs was found to be 27 ± 5nm for H. rhamnoides and 84 ± 4nm for C. intybus. The IC50 value of 41.69 µM for H. rhmnoides and 71.04 µM for C. intybus Fe2O3 NPs compared to plant extract (78.10 and 96.03 µM for H. rhamnoides and C. intybus, respectively) were found against HepG2 cells. The gene expression and protein levels of RhoA were decreased whereas those of bax, caspase 3, caspase 8 and caspase 9 were found increased.

CONCLUSION

Nanoparticles and extract of H. rhamnoides were found more effective as compared to C. intybus, which was evident by the results of cytotoxicity and analysis of studied genes and proteins.

In Vivo Self-Sorting of Peptides via In Situ Assembly Evolution

Despite significant progress achieved in artificial self-sorting in solution, operating self-sorting in the body remains a considerable challenge. Here, we report an in vivo self-sorting peptide system via an in situ assembly evolution for combined cancer therapy. The peptide E3C16-SS-EIY consists of two disulfide-connected segments, E3C16SH and SHEIY, capable of independent assembly into twisted or flat nanoribbons. While E3C16-SS-EIY assembles into nanorods, exposure to glutathione (GSH) leads to the conversion of the peptide into E3C16SH and SHEIY, thus promoting in situ evolution from the nanorods into self-sorted nanoribbons. Furthermore, incorporation of two ligand moieties targeting antiapoptotic protein XIAP and organellar endoplasmic reticulum (ER) into the self-sorted nanoribbons allows for simultaneous inhibition of XIAP and accumulation surrounding ER. This leads to the cytotoxicity toward the cancer cells with elevated GSH levels, through activating caspase-dependent apoptosis and inducing ER dysfunction. In vivo self-sorting of E3C16-SS-EIY decorated with ligand moieties is thoroughly validated by tissue studies. Tumor-bearing mouse experiments confirm the therapeutic efficacy of the self-sorted assemblies for inhibiting tumor growth, with excellent biosafety. Our findings demonstrate an efficient approach to develop in vivo self-sorting systems and thereby facilitating in situ formulation of biomedical agents.

ARTS and small-molecule ARTS mimetics upregulate p53 levels by promoting the degradation of XIAP

Mutations resulting in decreased activity of p53 tumor suppressor protein promote tumorigenesis. P53 protein levels are tightly regulated through the Ubiquitin Proteasome System (UPS). Several E3 ligases were shown to regulate p53 stability, including MDM2. Here we report that the ubiquitin E3 ligase XIAP (X-linked Inhibitors of Apoptosis) is a direct ligase for p53 and describe a novel approach for modulating the levels of p53 by targeting the XIAP pathway. Using in vivo (live-cell) and in vitro (cell-free reconstituted system) ubiquitylation assays, we show that the XIAP-antagonist ARTS regulates the levels of p53 by promoting the degradation of XIAP. XIAP directly binds and ubiquitylates p53. In apoptotic cells, ARTS inhibits the ubiquitylation of p53 by antagonizing XIAP. XIAP knockout MEFs express higher p53 protein levels compared to wild-type MEFs. Computational screen for small molecules with high affinity to the ARTS-binding site within XIAP identified a small-molecule ARTS-mimetic, B3. This compound stimulates apoptosis in a wide range of cancer cells but not normal PBMC (Peripheral Blood Mononuclear Cells). Like ARTS, the B3 compound binds to XIAP and promotes its degradation via the UPS. B3 binding to XIAP stabilizes p53 by disrupting its interaction with XIAP. These results reveal a novel mechanism by which ARTS and p53 regulate each other through an amplification loop to promote apoptosis. Finally, these data suggest that targeting the ARTS binding pocket in XIAP can be used to increase p53 levels as a new strategy for developing anti-cancer therapeutics.

Interaction of SMAC with a survivin-derived peptide alters essential cancer hallmarks: Tumor growth, inflammation, and immunosuppression

Second mitochondrial-derived activator of caspase (SMAC), also known as direct inhibitor of apoptosis-binding proteins with low pI (Diablo), is known as a pro-apoptotic mitochondrial protein released into the cytosol in response to apoptotic signals. We recently reported SMAC overexpression in cancers as essential for cell proliferation and tumor growth due to non-apoptotic functions, including phospholipid synthesis regulation. These functions may be associated with its interactions with partner proteins. Using a peptide array with 768 peptides derived from 11 selected SMAC-interacting proteins, we identified SMAC-interacting sequences. These SMAC-binding sequences were produced as cell-penetrating peptides targeted to the cytosol, mitochondria, or nucleus, inhibiting cell proliferation and inducing apoptosis in several cell lines. For in vivo study, a survivin/baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5)-derived peptide was selected, due to its overexpression in many cancers and its involvement in mitosis, apoptosis, autophagy, cell proliferation, inflammation, and immune responses, as a target for cancer therapy. Specifically, a SMAC-targeting survivin/BIRC5-derived peptide, given intratumorally or intravenously, strongly inhibited lung tumor growth, cell proliferation, angiogenesis, and inflammation, induced apoptosis, and remodeled the tumor microenvironment. The peptide promoted tumor infiltration of CD-8+ cells and increased cell-intrinsic programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1) expression, resulting in cancer cell self-destruction and increased tumor cell death, preserving immune cells. Thus, targeting the interaction between the multifunctional proteins SMAC and survivin represents an innovative therapeutic cancer paradigm.

Mechanisms of Biological Effects of Ionic Liquids: From Single Cells to Multicellular Organisms

The review presents a detailed discussion of the evolving field studying interactions between ionic liquids (ILs) and biological systems. Originating from molten salt electrolytes to present multiapplication substances, ILs have found usage across various fields due to their exceptional physicochemical properties, including excellent tunability. However, their interactions with biological systems and potential influence on living organisms remain largely unexplored. This review examines the cytotoxic effects of ILs on cell cultures, biomolecules, and vertebrate and invertebrate organisms. Our understanding of IL toxicity, while growing in recent years, is yet nascent. The established findings include correlations between harmful effects of ILs and their ability to disturb cellular membranes, their potential to trigger oxidative stress in cells, and their ability to cause cell death via apoptosis. Future research directions proposed in the review include studying the distribution of various ILs within cellular compartments and organelles, investigating metabolic transformations of ILs in cells and organisms, detailed analysis of IL effects on proteins involved in oxidative stress and apoptosis, correlation studies between IL doses, exposure times and resulting adverse effects, and examination of effects of subtoxic concentrations of ILs on various biological objects. This review aims to serve as a critical analysis of the current body of knowledge on IL-related toxicity mechanisms. Furthermore, it can guide researchers toward the design of less toxic ILs and the informed use of ILs in drug development and medicine.

Design, in silico evaluation, and in vitro verification of new bivalent Smac mimetics with pro-apoptotic activity

Bivalent Smac mimetics have been shown to possess binding affinity and pro-apoptotic activity similar to or more potent than that of native Smac, a protein dimer able to neutralize the anti-apoptotic activity of an inhibitor of caspase enzymes, XIAP, which endows cancer cells with resistance to anticancer drugs. We design five new bivalent Smac mimetics, which are formed by various linkers tethering two diazabicyclic cores being the IAP binding motifs. We built in silico models of the five mimetics by the TwistDock workflow and evaluated their conformational tendency, which suggests that compound 3, whose linker is n-hexylene, possess the highest binding potency among the five. After synthesis of these compounds, their ability in tumour cell growth inhibition and apoptosis induction displayed in experiments with SK-OV-3 and MDA-MB-231 cancer cell lines confirms our prediction. Among the five mimetics, compound 3 displays promising pro-apoptotic activity and deserves further optimization.

Recent trends and advances in novel formulations as an armament in Bcl-2/Bax targeted breast cancer

Breast cancer (BC) remains a significant health burden worldwide, necessitating the development of innovative therapeutic strategies. The B-cell lymphoma 2 (Bcl-2) family proteins, Bcl-2 and Bax, play a crucial role in regulating apoptosis and thus are promising targets for BC therapy. We focus on the recent advancements in novel formulations that specifically target Bcl-2/Bax pathway to combat BC. It provides an overview on biological functions of Bcl-2/Bax in apoptosis regulation, emphasizing their significance in pathogenesis and progression of the disease while covering the numerous therapeutic approaches aimed at modulating the Bcl-2/Bax pathway, including small-molecule inhibitors, peptides, gene-based therapies and other repurposed drugs harboured onto cutting-edge technologies and nanocarrier systems employed to enhance the targeted delivery of Bcl-2/Bax inhibitors tumor cells. These advanced formulations aim to improve therapeutic efficacy, minimize off-target effects, and overcome drug resistance, offering promising prospects in its treatment. In conclusion, it illuminates the diverse and evolving landscape of novel formulations as an essential armament in targeting these proteins while bridging and unravelling the obscurity of Bcl-2/Bax pathway-targeted drug delivery systems which are presently in their nascent stages of exploration for BC therapy which can benefit researchers, clinicians, and pharmaceutical scientists.

The novel drug candidate S2/IAPinh improves survival in models of pancreatic and ovarian cancer

Cancer selective apoptosis remains a therapeutic challenge and off-target toxicity has limited enthusiasm for this target clinically. Sigma-2 ligands (S2) have been shown to enhance the cancer selectivity of small molecule drug candidates by improving internalization. Here, we report the synthesis of a novel drug conjugate, which was created by linking a clinically underperforming SMAC mimetic (second mitochondria-derived activator of caspases; LCL161), an inhibitor (antagonist) of inhibitor of apoptosis proteins (IAPinh) with the sigma-2 ligand SW43, resulting in the new chemical entity S2/IAPinh. Drug potency was assessed via cell viability assays across several pancreatic and ovarian cancer cell lines in comparison with the individual components (S2 and IAPinh) as well as their equimolar mixtures (S2 + IAPinh) both in vitro and in preclinical models of pancreatic and ovarian cancer. Mechanistic studies of S2/IAPinh-mediated cell death were investigated in vitro and in vivo using syngeneic and xenograft mouse models of murine pancreatic and human ovarian cancer, respectively. S2/IAPinh demonstrated markedly improved pharmacological activity in cancer cell lines and primary organoid cultures when compared to the controls. In vivo testing demonstrated a marked reduction in tumor growth rates and increased survival rates when compared to the respective control groups. The predicted mechanism of action of S2/IAPinh was confirmed through assessment of apoptosis pathways and demonstrated strong target degradation (cellular inhibitor of apoptosis proteins-1 [cIAP-1]) and activation of caspases 3 and 8. Taken together, S2/IAPinh demonstrated efficacy in models of pancreatic and ovarian cancer, two challenging malignancies in need of novel treatment concepts. Our data support an in-depth investigation into utilizing S2/IAPinh for the treatment of cancer.

Selective induction of programmed cell death using synthetic biology tools

Regulated cell death (RCD) controls the removal of dispensable, infected or malignant cells, and is thus essential for development, homeostasis and immunity of multicellular organisms. Over the last years different forms of RCD have been described (among them apoptosis, necroptosis, pyroptosis and ferroptosis), and the cellular signaling pathways that control their induction and execution have been characterized at the molecular level. It has also become apparent that different forms of RCD differ in their capacity to elicit inflammation or an immune response, and that RCD pathways show a remarkable plasticity. Biochemical and genetic studies revealed that inhibition of a given pathway often results in the activation of back-up cell death mechanisms, highlighting close interconnectivity based on shared signaling components and the assembly of multivalent signaling platforms that can initiate different forms of RCD. Due to this interconnectivity and the pleiotropic effects of 'classical' cell death inducers, it is challenging to study RCD pathways in isolation. This has led to the development of tools based on synthetic biology that allow the targeted induction of RCD using chemogenetic or optogenetic methods. Here we discuss recent advances in the development of such toolset, highlighting their advantages and limitations, and their application for the study of RCD in cells and animals.

Molecular mechanisms underlying the BIRC6-mediated regulation of apoptosis and autophagy

Procaspase 9 is the initiator caspase for apoptosis, but how its levels and activities are maintained remains unclear. The gigantic Inhibitor-of-Apoptosis Protein BIRC6/BRUCE/Apollon inhibits both apoptosis and autophagy by promoting ubiquitylation of proapoptotic factors and the key autophagic protein LC3, respectively. Here we show that BIRC6 forms an anti-parallel U-shaped dimer with multiple previously unannotated domains, including a ubiquitin-like domain, and the proapoptotic factor Smac/DIABLO binds BIRC6 in the central cavity. Notably, Smac outcompetes the effector caspase 3 and the pro-apoptotic protease HtrA2, but not procaspase 9, for binding BIRC6 in cells. BIRC6 also binds LC3 through its LC3-interacting region, probably following dimer disruption of this BIRC6 region. Mutation at LC3 ubiquitylation site promotes autophagy and autophagic degradation of BIRC6. Moreover, induction of autophagy promotes autophagic degradation of BIRC6 and caspase 9, but not of other effector caspases. These results are important to understand how the balance between apoptosis and autophagy is regulated under pathophysiological conditions.

Functional characterization of Nosema bombycis (microsporidia) trehalase 3

Nosema bombycis, an obligate intracellular parasite, is a single-celled eukaryote known to infect various tissues of silkworms, leading to the manifestation of pebrine. Trehalase, a glycosidase responsible for catalyzing the hydrolysis of trehalose into two glucose molecules, assumes a crucial role in thermal stress tolerance, dehydration, desiccation stress, and asexual development. Despite its recognized importance in these processes, the specific role of trehalase in N. bombycis remains uncertain. This investigation focused on exploring the functions of trehalase 3 in N. bombycis (NbTre3). Immunofluorescence analysis of mature (dormant) spores indicated that NbTre3 primarily localizes to the spore membrane or spore wall, suggesting a potential involvement in spore germination. Reverse transcription-quantitative polymerase chain reaction results indicated that the transcriptional level of NbTre3 peaked at 6 h post N. bombycis infection, potentially contributing to energy storage for proliferation. Throughout the life cycle of N. bombycis within the host cell, NbTre3 was detected in sporoplasm during the proliferative stage rather than the sporulation stage. RNA interference experiments revealed a substantial decrease in the relative transcriptional level of NbTre3, accompanied by a certain reduction in the relative transcriptional level of Nb16S rRNA. These outcomes suggest that NbTre3 may play a role in the proliferation of N. bombycis. The application of the His pull-down technique identified 28 proteins interacting with NbTre3, predominantly originating from the host silkworm. This finding implies that NbTre3 may participate in the metabolism of the host cell, potentially utilizing the host cell's energy resources.

Cell death classification: A new insight based on molecular mechanisms

Cells tend to disintegrate themselves or are forced to undergo such destructive processes in critical circumstances. This complex cellular function necessitates various mechanisms and molecular pathways in order to be executed. The very nature of cell death is essentially important and vital for maintaining homeostasis, thus any type of disturbing occurrence might lead to different sorts of diseases and dysfunctions. Cell death has various modalities and yet, every now and then, a new type of this elegant procedure gets to be discovered. The diversity of cell death compels the need for a universal organizing system in order to facilitate further studies, therapeutic strategies and the invention of new methods of research. Considering all that, we attempted to review most of the known cell death mechanisms and sort them all into one arranging system that operates under a simple but subtle decision-making (If \ Else) order as a sorting algorithm, in which it decides to place and sort an input data (a type of cell death) into its proper set, then a subset and finally a group of cell death. By proposing this algorithm, the authors hope it may solve the problems regarding newer and/or undiscovered types of cell death and facilitate research and therapeutic applications of cell death.

Artemisia carvifolia Buch silver nanoparticles downregulate the Rap2A gene in liver cancer

Liver cancer is the second main reason of death globally. In the current study, Rap2A protein a member of Ras Gtpase was selected as a drug target for liver cancer which has been identified as an oncogene in different types of tumors. The present study aimed to evaluate Artemisia carvifolia Buch extract and its silver nanoparticles against liver cancer targeting the Rap2A gene. The synthesized silver nanoparticles showed an absorbance peak at 450 nm by a UV-Vis spectrophotometer. SEM revealed that polyhedral silver nanoparticles had a size ranging from 80 ± 6 nm. Furthermore, amines, aldehydes, ketones and alcohols of Artemisia carvifolia were found involved in the reduction and stabilization of nanoparticles by FTIR. Moreover, XRD and EDX confirmed the cubic crystalline nature and particle elemental composition, respectively. Furthermore, the cytotoxicity against HePG2 cancer cell lines was also found significant with an IC50 value of 2.57 µM for silver nanoparticles and 11.57 µM for plant extract. The gene expression and protein level of Rap2A were also decreased in plant extract and nanoparticle-treated cells compared to control groups. The apoptotic potential of extract and nanoparticles was also determined by evaluating the apoptotic pathway genes and protein including BAX, caspase 3, 8 and 9. Significantly elevated levels of expression of these genes by real-time qPCR along with increased protein levels by ELISA were found. This is the first-ever report describing the synthesis and efficacy of silver nanoparticles of Artemisia carvifolia Buch against liver cancer.

Birinapant selectively enhances immunotoxin-mediated killing of cancer cells conditional on the IAP protein levels within target cells

Immunotoxins (ITs) target cancer cells via antibody binding to surface antigens followed by internalization and toxin-mediated inhibition of protein synthesis. The fate of cells responding to IT treatment depends on the amount and stability of specific pro-apoptotic and pro-survival proteins. When treated with a pseudomonas exotoxin-based immunotoxin (HB21PE40), the triple-negative breast cancer (TNBC) cell line MDA-MB-468 displayed a notable resistance to toxin-mediated killing compared to the epidermoid carcinoma cell line, A431, despite succumbing to the same level of protein synthesis inhibition. In a combination screen of ~1912 clinically relevant and mechanistically annotated compounds, we identified several agents that greatly enhanced IT-mediated killing of MDA-MB-468 cells while exhibiting only a modest enhancement for A431 cells. Of interest, two Smac mimetics, birinapant and SM164, exhibited this kind of differential enhancement. To investigate the basis for this, we probed cells for the presence of inhibitor of apoptosis (IAP) proteins and monitored their stability after the addition of immunotoxin. We found that high levels of IAPs inhibited immunotoxin-mediated cell death. Further, TNFα levels were not relevant for the combination's efficacy. In tumor xenograft studies, combinations of immunotoxin and birinapant caused complete regressions in MDA-MB-468tumor-bearing mice but not in mice with A431 tumors. We propose that IAPs constitute a barrier to immunotoxin efficacy which can be overcome with combination treatments that include Smac mimetics.

The identification of BCL-XL and MCL-1 as key anti-apoptotic proteins in medulloblastoma that mediate distinct roles in chemotherapy resistance

Medulloblastoma is the most common malignant paediatric brain tumour, representing 20% of all paediatric intercranial tumours. Current aggressive treatment protocols and the use of radiation therapy in particular are associated with high levels of toxicity and significant adverse effects, and long-term sequelae can be severe. Therefore, improving chemotherapy efficacy could reduce the current reliance on radiation therapy. Here, we demonstrated that systems-level analysis of basal apoptosis protein expression and their signalling interactions can differentiate between medulloblastoma cell lines that undergo apoptosis in response to chemotherapy, and those that do not. Combining computational predictions with experimental BH3 profiling, we identified a therapeutically-exploitable dependence of medulloblastoma cells on BCL-XL, and experimentally validated that BCL-XL targeting, and not targeting of BCL-2 or MCL-1, can potentiate cisplatin-induced cytotoxicity in medulloblastoma cell lines with low sensitivity to cisplatin treatment. Finally, we identified MCL-1 as an anti-apoptotic mediator whose targeting is required for BCL-XL inhibitor-induced apoptosis. Collectively, our study identifies that BCL-XL and MCL-1 are the key anti-apoptotic proteins in medulloblastoma, which mediate distinct protective roles. While BCL-XL has a first-line role in protecting cells from apoptosis basally, MCL-1 represents a second line of defence that compensates for BCL-XL upon its inhibition. We provide rationale for the further evaluation of BCL-XL and MCL-1 inhibitors in the treatment of medulloblastoma, and together with current efforts to improve the cancer-specificity of BCL-2 family inhibitors, these novel treatment strategies have the potential to improve the future clinical management of medulloblastoma.

Contribution of mitochondria to postmortem muscle tenderization: a review

Postmortem meat tenderization is a process mediated by a series of biochemical reactions related to muscle cell death. Cell death is considered a sign that muscle has started to transform into meat. Mitochondria play a significant role in regulating and executing cell death, as they are an aggregation point for many cell death signals and are also the primary target organelle damaged by tissue anoxia. Mitochondrial damage is likely to have an expanded role in postmortem meat tenderization. This review presents current findings on mitochondrial damage induced by the accumulation of reactive oxygen species during postmortem anaerobic metabolism and on the impact of mitochondrial damage on proteolysis and discusses how this leads to improved tenderness during aging. The underlying mechanisms of mitochondrial regulation of postmortem muscle tenderization likely focus on the mitochondria's role in postmortem cell death and energy metabolism. The death process of postmortem skeletal muscle cells may exhibit multiple types, possibly involving transformation from autophagy to apoptosis and, ultimately, necroptosis or necrosis. Mitochondrial characteristics, especially membrane integrity and ATP-related compound levels, are closely related to the transformation of multiple types of dead postmortem muscle cells. Finally, a possible biochemical regulatory network in postmortem muscle tenderization is proposed.

A Review on Caspases: Key Regulators of Biological Activities and Apoptosis

Caspases are proteolytic enzymes that belong to the cysteine protease family and play a crucial role in homeostasis and programmed cell death. Caspases have been broadly classified by their known roles in apoptosis (caspase-3, caspase-6, caspase-7, caspase-8, and caspase-9 in mammals) and in inflammation (caspase-1, caspase-4, caspase-5, and caspase-12 in humans, and caspase-1, caspase-11, and caspase-12 in mice). Caspases involved in apoptosis have been subclassified by their mechanism of action as either initiator caspases (caspase-8 and caspase-9) or executioner caspases (caspase-3, caspase-6, and caspase-7). Caspases that participate in apoptosis are inhibited by proteins known as inhibitors of apoptosis (IAPs). In addition to apoptosis, caspases play a role in necroptosis, pyroptosis, and autophagy, which are non-apoptotic cell death processes. Dysregulation of caspases features prominently in many human diseases, including cancer, autoimmunity, and neurodegenerative disorders, and increasing evidence shows that altering caspase activity can confer therapeutic benefits. This review covers the different types of caspases, their functions, and their physiological and biological activities and roles in different organisms.

A Naturally Derived Watercress Flower-Based Phenethyl Isothiocyanate-Enriched Extract Induces the Activation of Intrinsic Apoptosis via Subcellular Ultrastructural and Ca2+ Efflux Alterations in an In Vitro Model of Human Malignant Melanoma

The aim of the current study was to (i) extract isolated fractions of watercress flowers enriched in polyphenols, phenethyl isothiocyanate and glucosinolates and (ii) characterize the anticancer mode of action of non-lethal, sub-lethal and lethal concentrations of the most potent extract fraction in primary (A375) and metastatic (COLO-679) melanoma cells as well as non-tumorigenic immortalized keratinocyte (HaCaT) cells. Cytotoxicity was assessed via the Alamar Blue assay, whereas ultrastructural alterations in mitochondria and the endoplasmic reticulum were determined via transmission electron microscopy. Mitochondrial membrane depolarization was determined using Mito-MP dye, whereas apoptosis was evaluated through the activation of caspases-3, -8 and -9. Among all extract fractions, the phenethyl isothiocyanate-enriched one (PhEF) possessed significant cytotoxicity against A375 and COLO-679 cells, while HaCaT cells remained relatively resistant at sub-lethal and lethal concentrations. Additionally, ultrastructural subcellular alterations associated with apoptosis were observed by means of increased mitochondrial area and perimeter, decreased cristae density and a shorter distance of the endoplasmic reticulum to the mitochondria, all taking place during "early" time points (2-4 h) of exposure. Moreover, PhEF induced mitochondrial membrane depolarization associated with "late" time points (24 h) of exposure, thereby leading to the activation of intrinsic apoptosis. Finally, the inhibition of cytosolic Ca2+ efflux reduced levels of caspases-9 and -3 activity, suggesting the involvement of Ca2+ efflux in modulating the activation of intrinsic apoptosis. To conclude, our data demonstrate an association of "early" ultrastructural alterations in mitochondria and the endoplasmic reticulum with the "late" induction of intrinsic apoptosis via the modulation of Ca2+ efflux.

Dual-targeting peptides@PMO, a mimetic to the pro-apoptotic protein Smac/DIABLO for selective activation of apoptosis in cancer cells

The refractoriness of tumor cells to apoptosis represents the main mechanism of resistance to chemotherapy. Smac/DIABLO mimetics proved to be effective in overcoming cancer-acquired resistance to apoptosis as a consequence of overexpression of the anti-apoptotic proteins XIAP, cIAP1, and cIAP2. In this work, we describe a dual-targeting peptide capable of selectively activating apoptosis in cancer cells. The complex consists of a fluorescent periodic mesoporous organosilica nanoparticle that carries the short sequences of Smac/DIABLO bound to the αvβ3-integrin ligand. The dual-targeting peptide @PMO shows significantly higher toxicity in αvβ3-positive HeLa cells with respect to αvβ3-negative Ht29 cells. @PMO exhibited synergistic effects in combination with oxaliplatin in a panel of αvβ3-positive cancer cells, while its toxicity is overcome by XIAP overexpression or integrin β3 silencing. The successful uptake of the molecule by αvβ3-positive cells makes @PMO promising for the re-sensitization to apoptosis of many cancer types.

Melatonin as a regulator of apoptosis in leukaemia: molecular mechanism and therapeutic perspectives

Leukaemia is a dangerous malignancy that causes thousands of deaths every year throughout the world. The rate of morbidity and mortality is significant despite many advancements in therapy strategies for affected individuals. Most antitumour medications used now in clinical oncology use apoptotic signalling pathways to induce cancer cell death. Accumulated data have shown a direct correlation between inducing apoptosis in cancer cells with higher tumour regression and survival. Until now, the efficacy of melatonin as a powerful antitumour agent has been firmly established. A change in melatonin concentrations has been reported in multiple tumours such as endometrial, hematopoietic, and breast cancers. Findings show that melatonin's anticancer properties, such as its prooxidation function and ability to promote apoptosis, indicate the possibility of utilizing this natural substance as a promising agent in innovative cancer therapy approaches. Melatonin stimulates cell apoptosis via the regulation of many apoptosis facilitators, including mitochondria, cytochrome c, Bcl-2, production of reactive oxygen species, and apoptosis receptors. This paper aimed to further assess the anticancer effects of melatonin through the apoptotic pathway, considering the role that cellular apoptosis plays in the pathogenesis of cancer. The effect of melatonin may mean that it is appropriate for use as an adjuvant, along with other therapeutic approaches such as radiotherapy and chemotherapy.

The Effect of Xevinapant Combined with Ionizing Radiation on HNSCC and Normal Tissue Cells and the Impact of Xevinapant on Its Targeted Proteins cIAP1 and XIAP

The poor prognosis of HNSCC is partly due to treatment resistance. The SMAC mimetic Xevinapant is a promising new approach to targeted cancer therapy. Xevinapant inhibits cIAP1/2 and XIAP, leading to apoptosis, necroptosis and inhibition of prosurvival signaling. Combining Xevinapant with IR could improve therapeutic potential. The effect of Xevinapant in combination with IR on HNSCC and healthy tissue cells was investigated. Cell growth, cell death, clonogenic survival and DNA double-strand breaks (DSBs) were studied, and intracellular cIAP1 and XIAP levels were evaluated. Xevinapant had cytostatic and cytotoxic, as well as radiosensitizing, effects on the malignant cells, while healthy tissue cells were less affected. Apoptotic and necrotic cell death was particularly affected, but the increase in residual DSBs and the reduced survival implied an additional effect of Xevinapant on DNA damage repair and other cell inactivation mechanisms. cIAP1 and XIAP levels varied for each cell line and were affected by Xevinapant and IR treatment. There was an association between higher IAP levels and increased cell death. Xevinapant appears to be a potent new drug for HNSCC therapy, especially in combination with IR. IAP levels could be an indicator for impaired DNA damage repair and increased susceptibility to cellular stress.

The role of apoptosis in the pathogenesis of osteoarthritis

PURPOSE

Apoptosis is an important physiological process, making a great difference to development and tissue homeostasis. Osteoarthritis (OA) is a chronic joint disease characterized by degeneration and destruction of articular cartilage and bone hyperplasia. This purpose of this study is to provide an updated review of the role of apoptosis in the pathogenesis of osteoarthritis.

METHODS

A comprehensive review of the literature on osteoarthritis and apoptosis was performed, which mainly focused on the regulatory factors and signaling pathways associated with chondrocyte apoptosis in osteoarthritis and other pathogenic mechanisms involved in chondrocyte apoptosis.

RESULTS

Inflammatory mediators such as reactive oxygen species (ROS), nitric oxide (NO), IL-1β, tumor necrosis factor-α (TNF-α), and Fas are closely related to chondrocyte apoptosis. NF-κB signaling pathway, Wnt signaling pathway, and Notch signaling pathway activate proteins and gene targets that promote or inhibit the progression of osteoarthritis disease, including chondrocyte apoptosis and ECM degradation. Long non-coding RNAs (LncRNAs) and microRNAs (microRNAs) have gradually replaced single and localized research methods and become the main research approaches. In addition, the relationship between cellular senescence, autophagy, and apoptosis was also briefly explained.

CONCLUSION

This review offers a better molecular delineation of apoptotic processes that may help in designing new therapeutic options for OA treatment.

Heterobifunctional Ligase Recruiters Enable pan-Degradation of Inhibitor of Apoptosis Proteins

Proteolysis targeting chimeras (PROTACs) represent a new pharmacological modality to inactivate disease-causing proteins. PROTACs operate via recruiting E3 ubiquitin ligases, which enable the transfer of ubiquitin tags onto their target proteins, leading to proteasomal degradation. However, several E3 ligases are validated pharmacological targets themselves, of which inhibitor of apoptosis (IAP) proteins are considered druggable in cancer. Here, we report three series of heterobifunctional PROTACs, which consist of an IAP antagonist linked to either von Hippel-Lindau- or cereblon-recruiting ligands. Hijacking E3 ligases against each other led to potent, rapid, and preferential depletion of cellular IAPs. In addition, these compounds caused complete X-chromosome-linked IAP knockdown, which was rarely observed for monovalent and homobivalent IAP antagonists. In cellular assays, hit degrader 9 outperformed antagonists and showed potent inhibition of cancer cell viability. The hetero-PROTACs disclosed herein are valuable tools to facilitate studies of the biological roles of IAPs and will stimulate further efforts toward E3-targeting therapies.

Apoptotic proteins with non-apoptotic activity: expression and function in cancer

Apoptosis is a process of programmed cell death in which a cell commits suicide while maintaining the integrity and architecture of the tissue as a whole. Apoptosis involves activation of one of two major pathways: the extrinsic pathway, where extracellular pro-apoptotic signals, transduced through plasma membrane death receptors, activate a caspase cascade leading to apoptosis. The second, the intrinsic apoptotic pathway, where damaged DNA, oxidative stress, or chemicals, induce the release of pro-apoptotic proteins from the mitochondria, leading to the activation of caspase-dependent and independent apoptosis. However, it has recently become apparent that proteins involved in apoptosis also exhibit non-cell death-related physiological functions that are related to the cell cycle, differentiation, metabolism, inflammation or immunity. Such non-conventional activities were predominantly reported in non-cancer cells although, recently, such a dual function for pro-apoptotic proteins has also been reported in cancers where they are overexpressed. Interestingly, some apoptotic proteins translocate to the nucleus in order to perform a non-apoptotic function. In this review, we summarize the unconventional roles of the apoptotic proteins from a functional perspective, while focusing on two mitochondrial proteins: VDAC1 and SMAC/Diablo. Despite having pro-apoptotic functions, these proteins are overexpressed in cancers and this apparent paradox and the associated pathophysiological implications will be discussed. We will also present possible mechanisms underlying the switch from apoptotic to non-apoptotic activities although a deeper investigation into the process awaits further study.

Modulatory role of BV6 and chloroquine on the regulation of apoptosis and autophagy in non-small cell lung cancer cells

AIMS

Non-small cell lung cancer (NSCLC) is one of the aggressive tumors mostly diagnosed in the advanced stage. Therapeutic failure and drug resistance pose a major problem in NSCLC treatment primarily due to alterations in autophagy and loss of apoptosis. Therefore, the present study aimed to investigate the importance of the second mitochondria-derived activator of caspase mimetic BV6 and autophagy inhibitor chloroquine (CQ) on the regulation of apoptosis and autophagy, respectively.

SUBJECTS AND METHODS

Study was conducted on NCI-H23 and NCI-H522 cell lines to evaluate the effect of BV6 and CQ on the transcription and translation level of LC3-II, caspase-3, and caspase-9 genes by quantitative real-time-polymerase chain reaction and western blotting techniques.

RESULTS

In NCI-H23 cell line, BV6 and CQ treatments showed increased mRNA and protein expression of caspase-3, and caspase-9 compared to its untreated counterpart. BV6 and CQ treatments also caused downregulation of LC3-II protein expression compared to its counterpart. In NCI-H522 cell line, BV6 treatment showed a significantly increased expression of caspase-3 and caspase-9 mRNA and protein expression levels whereas BV6 treatment downregulated the expression level of LC3-II protein. A similar pattern was also observed in CQ treatment when compared with the respective controls. Both BV6 and CQ modulated in vitro expression of caspases and LC3-II which have critical regulatory roles in apoptosis and autophagy, respectively.

CONCLUSIONS

Our findings suggest that BV6 and CQ could be promising candidates in NSCLC treatment and there is a need to explore them in vivo and in clinical applications.

HOXB3 drives WNT-activation associated progression in castration-resistant prostate cancer

Enabled resistance or innate insensitiveness to antiandrogen are lethal for castration-resistant prostate cancer (CRPC). Unfortunately, there seems to be little can be done to overcome the antiandrogen resistance because of the largely unknown mechanisms. In prospective cohort study, we found that HOXB3 protein level was an independent risk factor of PSA progression and death in patients with metastatic CRPC. In vivo, upregulated HOXB3 contributed to CRPC xenografts progression and abiraterone resistance. To uncover the mechanism of HOXB3 driving tumor progression, we performed RNA-sequencing in HOXB3 negative (HOXB3-) and HOXB3 high (HOXB3 + ) staining CRPC tumors and determined that HOXB3 activation was associated with the expression of WNT3A and enriched WNT pathway genes. Furthermore, extra WNT3A and APC deficiency led HOXB3 to be isolated from destruction-complex, translocated to nuclei, and then transcriptionally regulated multiple WNT pathway genes. What's more, we also observed that the suppression of HOXB3 could reduce cell proliferation in APC-downregulated CRPC cells and sensitize APC-deficient CRPC xenografts to abiraterone again. Together, our data indicated that HOXB3 served as a downstream transcription factor of WNT pathway and defined a subgroup of CRPC resistant to antiandrogen which would benefit from HOXB3-targeted therapy.

Structural basis for SMAC-mediated antagonism of caspase inhibition by the giant ubiquitin ligase BIRC6

Certain inhibitor of apoptosis (IAP) family members are sentinel proteins that prevent untimely cell death by inhibiting caspases. Antagonists, including second mitochondria-derived activator of caspases (SMAC), regulate IAPs and drive cell death. Baculoviral IAP repeat-containing protein 6 (BIRC6), a giant IAP with dual E2 and E3 ubiquitin ligase activity, regulates programmed cell death through unknown mechanisms. We show that BIRC6 directly restricts executioner caspase-3 and -7 and ubiquitinates caspase-3, -7, and -9, working exclusively with noncanonical E1, UBA6. Notably, we show that SMAC suppresses both mechanisms. Cryo-electron microscopy structures of BIRC6 alone and in complex with SMAC reveal that BIRC6 is an antiparallel dimer juxtaposing the substrate-binding module against the catalytic domain. Furthermore, we discover that SMAC multisite binding to BIRC6 results in a subnanomolar affinity interaction, enabling SMAC to competitively displace caspases, thus antagonizing BIRC6 anticaspase function.

Structures of BIRC6-client complexes provide a mechanism of SMAC-mediated release of caspases

Tight regulation of apoptosis is essential for metazoan development and prevents diseases such as cancer and neurodegeneration. Caspase activation is central to apoptosis, and inhibitor of apoptosis proteins (IAPs) are the principal actors that restrain caspase activity and are therefore attractive therapeutic targets. IAPs, in turn, are regulated by mitochondria-derived proapoptotic factors such as SMAC and HTRA2. Through a series of cryo-electron microscopy structures of full-length human baculoviral IAP repeat-containing protein 6 (BIRC6) bound to SMAC, caspases, and HTRA2, we provide a molecular understanding for BIRC6-mediated caspase inhibition and its release by SMAC. The architecture of BIRC6, together with near-irreversible binding of SMAC, elucidates how the IAP inhibitor SMAC can effectively control a processive ubiquitin ligase to respond to apoptotic stimuli.

Aberrant phase separation is a common killing strategy of positively charged peptides in biology and human disease

Positively charged repeat peptides are emerging as key players in neurodegenerative diseases. These peptides can perturb diverse cellular pathways but a unifying framework for how such promiscuous toxicity arises has remained elusive. We used mass-spectrometry-based proteomics to define the protein targets of these neurotoxic peptides and found that they all share similar sequence features that drive their aberrant condensation with these positively charged peptides. We trained a machine learning algorithm to detect such sequence features and unexpectedly discovered that this mode of toxicity is not limited to human repeat expansion disorders but has evolved countless times across the tree of life in the form of cationic antimicrobial and venom peptides. We demonstrate that an excess in positive charge is necessary and sufficient for this killer activity, which we name 'polycation poisoning'. These findings reveal an ancient and conserved mechanism and inform ways to leverage its design rules for new generations of bioactive peptides.

The synergistic effect of chimeras consisting of N-terminal smac and modified KLA peptides in inducing apoptosis in breast cancer cell lines

Drug resistance is one of the most important obstacles in effective cancer therapy triggered through various mechanisms. One of these mechanisms is caused by the upregulation of Inhibitor of Apoptosis Proteins (IAPs). IAPs, inhibit apoptosis through direct and/or indirect caspase inhibition, which themselves are antagonized by an endogenous protein called Second Mitochondrial-derived Activator of Caspases, Smac/Diablo, mediated by the presence of a tetrapeptide IAP binding motif at its N-terminus. Accordingly, Smac-based peptides are under intense investigation as anti-cancer drugs and have reached Phase 2 clinical trials, although, Smac based peptides or mimetics alone have not been effective as anti-cancer agents. On the other hand, KLA peptide has shown major toxicity against cancer cells through the induction of apoptosis. Consequently, we designed an anti-cancer chimera by fusing an octa-peptide from the N-terminus of mature Smac protein to a modified proapoptotic KLA peptide (KLAKLCKKLAKLCK) to be called Smac-KLA. This chimera, therefore, possesses both proapoptotic and anti-IAP activities. In addition, we dimerized this chimera via intermolecular disulfide bonds in order to enhance their cellular permeability. Both the Smac-KLA monomeric and dimeric peptides exhibited cytotoxic activity against both MCF-7 and MDA-MB231 breast cancer cell lines at low micromolar concentrations. Importantly, the dimerization of the chimeras enhanced their potency 2-4- fold due to higher cellular uptake.

Towards a templated reaction that translates RNA in cells into a proaptotic peptide-PNA conjugate

Nucleic acid-templated chemistry opens the intriguing prospect of triggering the synthesis of drugs only in diseased cells. Herein, we explore the feasibility of using RNA-templated chemical reactions for the activation of a known Smac peptidomimetic compound (SMC), which has proapoptotic activity. Two peptide nucleic acid (PNA) conjugates were used to enable conditional activation of a masked SMC by reduction of an azide either by Staudinger reduction or catalytic photoreduction using a ruthenium complex. The latter provided ~135 nM SMC-PNA on as little as 10 nM (0.01 eq.) template. For the evaluation of the templated azido-SMC reduction system in cellulo, a stable HEK 293 cell line was generated, which overexpressed a truncated, non-functional form of the XIAP mRNA target. We furthermore describe the development of electroporation protocols that enable a robust delivery of PNA conjugates into HEK 293 cells. The action of the reactive PNA conjugates was evaluated by viability and flow cytometric apoptosis assays. In addition, electroporated probes were re-isolated and analyzed by ultra-high performance liquid chromatography (UPLC). Unfortunately, the ruthenium-PNA conjugate proved phototoxic, and treatment of cells with PNA-linked reducing agent and the azido-masked SMC conjugate did not result in a greater viability loss than treatment with scrambled sequence controls. Intracellular product formation was not detectable. A control experiment in total cellular RNA isolate indicated that the templated reaction can in principle proceed in a complex system. The results of this first-of-its-kind study reveal the numerous hurdles that must be overcome if RNA molecules are to trigger the synthesis of pro-apoptotic drugs inside cells.

Structure optimization of new tumor-selective Passerini α-acyloxy carboxamides as Caspase-3/7 activators

Selective elimination of tumors has always been the mainstay of oncology research. The on-going research underlying the cellular apoptotic mechanisms reveal caspases activation, especially the key effector caspase-3, as a personalized tumor-selective therapeutic strategy. Our continued research protocol has exploited new optimized Passerini α-acyloxy carboxamides as efficient apoptotic inducers via caspase-3/7 dependent mechanism with highly selective anticancer profiles. The adopted design rationale relied on excluding structural alerts of previous leads, while merging various pharmacophoric motifs of natural and synthetic caspase activators via optimized one-pot Passerini reaction conditions. The prepared compounds resulting from Passerini reaction were screened for their cytotoxic activities against colorectal Caco-2 and liver HepG-2 cancer cells compared to normal fibroblasts utilizing MTT assay. Notably, all compounds exhibited promising low-range submicromolar IC₅₀ against the studied cancer cell lines, with outstanding tumor selectivity (SI values up to 266). Hence, they were superior to 5-fluorouracil. Notably, 7a, 7g, and 7j conferred the highest potencies against Caco-2 and HepG-2 cells and were selected for further mechanistic studies. Caspas-3/7 activation assay of the hit compounds and flow cytometric analysis of the treated apoptotic cancer cells demonstrated their significant caspase activation potential (up to 4.2 folds) and apoptotic induction capacities (up to 58.7%). Further assessment of Bcl2 expression was performed being a physiological caspase-3 substrate. Herein, the three studied Passerini adducts were able to downregulate Bcl2 in the treated Caco-2 cells. Importantly, the mechanistic studies results of the three hits echoed their preliminary MTT antiproliferative potencies data highlighting their caspase-3 dependent apoptotic induction. Finally, the in silico predicted physicochemical and pharmacokinetic profiles, as well as ligand efficiency metrics were drug-like.

The IAP antagonist birinapant enhances chimeric antigen receptor T cell therapy for glioblastoma by overcoming antigen heterogeneity

Antigen heterogeneity that results in tumor antigenic escape is one of the major obstacles to successful chimeric antigen receptor (CAR) T cell therapies in solid tumors including glioblastoma multiforme (GBM). To address this issue and improve the efficacy of CAR T cell therapy for GBM, we developed an approach that combines CAR T cells with inhibitor of apoptosis protein (IAP) antagonists, a new class of small molecules that mediate the degradation of IAPs, to treat GBM. Here, we demonstrated that the IAP antagonist birinapant could sensitize GBM cell lines and patient-derived primary GBM organoids to apoptosis induced by CAR T cell-derived cytokines, such as tumor necrosis factor. Therefore, birinapant could enhance CAR T cell-mediated bystander death of antigen-negative GBM cells, thus preventing tumor antigenic escape in antigen-heterogeneous tumor models in vitro and in vivo. In addition, birinapant could promote the activation of NF-κB signaling pathways in antigen-stimulated CAR T cells, and with a birinapant-resistant tumor model we showed that birinapant had no deleterious effect on CAR T cell functions in vitro and in vivo. Overall, we demonstrated the potential of combining the IAP antagonist birinapant with CAR T cells as a novel and feasible approach to overcoming tumor antigen heterogeneity and enhancing CAR T cell therapy for GBM.

Endoplasmic Reticulum Stress Signaling and Neuronal Cell Death

Besides protein processing, the endoplasmic reticulum (ER) has several other functions such as lipid synthesis, the transfer of molecules to other cellular compartments, and the regulation of Ca²⁺ homeostasis. Before leaving the organelle, proteins must be folded and post-translationally modified. Protein folding and revision require molecular chaperones and a favorable ER environment. When in stressful situations, ER luminal conditions or chaperone capacity are altered, and the cell activates signaling cascades to restore a favorable folding environment triggering the so-called unfolded protein response (UPR) that can lead to autophagy to preserve cell integrity. However, when the UPR is disrupted or insufficient, cell death occurs. This review examines the links between UPR signaling, cell-protective responses, and death following ER stress with a particular focus on those mechanisms that operate in neurons.

Study on complications of osteoporosis based on network pharmacology

Osteoporosis is a serious threat to human life. Guben Zenggu Granule is an empirical prescription for clinical treatment of osteoporosis. MC3T3-E1 cells are mouse osteogenic precursor cells with osteogenic differentiation, and are classic cells for studying bone metabolism and osteogenic mechanism, as well as mechanical stimulation sensitive cells. Therefore, it can be inferred that Guben Zenggu granule can repair MC3T3-E1 cells under continuous static pressure overload. This study aims to through the network of pharmacology and gene sequencing method, reveal thrift increase bone particles under the condition of continuous static pressure overload on osteogenesis mechanism of MC3T3-E1 cells. In the process of analysis, from a variety of 98 compounds was predicted in the database, a collection of 474 goals, a total of 29,164 difference between two groups of genes. Then, construction of composite targets between cells and predict targets and protein - protein interaction networks, and through the cluster analysis to further explore the relationship between the target. In addition, linkages between target proteins and cells were further identified using Gene Ontology (GO) and Pathways (KEGG Pathway). Finally, the repair effect of Guben Zenggu granule on MC3T3-E1 cells under continuous static pressure overload was verified through experiments, so as to accurately explain the pharmacodynamic mechanism of Traditional Chinese medicine.

Recent advances in therapeutic strategies for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer (BC) with a poor prognosis. Current treatment options are limited to surgery, adjuvant chemotherapy and radiotherapy; however, a proportion of patients have missed the surgical window at the time of diagnosis. TNBC is a highly heterogeneous cancer with specific mutations and aberrant activation of signaling pathways. Hence, targeted therapies, such as those targeting DNA repair pathways, androgen receptor signaling pathways, and kinases, represent promising treatment options against TNBC. In addition, immunotherapy has also been demonstrated to improve overall survival and response in TNBC. In this review, we summarize recent key advances in therapeutic strategies based on molecular subtypes in TNBC.

Proteomic analyses of mitochondrial damage in postmortem beef muscles

BACKGROUND

The objective of the study was to examine the expression profiles of mitochondrial proteins in at-death and 24 h postmortem (PM) using tandem mass tag (TMT) approach to characterize the mitochondria possible mechanisms that are affiliated with tenderization.

RESULTS

Results showed that the tender meat at 24 h PM emerged with more serious mitochondrial damage. Altogether 456 mitochondrial proteins were identified, including 442 down-regulated and 14 up-regulated proteins. These differentially-expressed proteins were primarily involved in the progress of PM energy metabolism, apoptosis, and the morphological alterations of mitochondrial. Among them, 47 subunits (such as NDUFA2, COX4I1, and ATP5PB) were annotated into the oxidative phosphorylation pathway. VDAC1, VDAC2, and VDAC3 involving in the damage of MPTP, and IMMT, CHCHD3, APOL and APOO modulating the morphology of mitochondria, and DIABLO and AIFM1 released from mitochondria affect caspase's activation. HSPD1 and HSPE1 involved in apoptosis, mitochondrial physiological and morphological alterations.

CONCLUSION

The earlier-mentioned proteins were validated as potential indicators of tenderness regulated by mitochondrial damage. These results highlighted that mitochondrial damage possibly participate in PM tenderization of beef muscles by energy metabolism and cell apoptosis status. © 2022 Society of Chemical Industry.

ILP-2: A New Bane and Therapeutic Target for Human Cancers

Inhibitor of apoptosis protein-related-like protein-2 (ILP-2), also known as BIRC-8, is a member of the inhibitor of apoptosis protein (IAPs) family, which mainly encodes the negative regulator of apoptosis. It is selectively overexpressed in a variety of human tumors and can help tumor cells evade apoptosis, promote tumor cell growth, increase tumor cell aggressiveness, and appears to be involved in tumor cell resistance to chemotherapeutic drugs. Several studies have shown that downregulation of ILP-2 expression increases apoptosis, inhibits metastasis, reduces cell growth potential, and sensitizes tumor cells to chemotherapeutic drugs. In addition, ILP-2 inhibits apoptosis in a unique manner; it does not directly inhibit the activity of caspases but induces apoptosis by cooperating with other apoptosis-related proteins. Here, we review the current understanding of the various roles of ILP-2 in the apoptotic cascade and explore the use of interfering ILP-2, and the combination of related anti-tumor agents, as a novel strategy for cancer therapy.

Targeting inhibitor of apoptosis proteins (IAPs) with IAP inhibitors sensitises malignant rhabdoid tumour cells to cisplatin

Malignant rhabdoid tumour (MRT) is a rare, aggressive paediatric malignancy most commonly diagnosed in those below the age of three. MRTs can arise in soft tissue but are more often associated with the central nervous system or kidney. Unfortunately, the prognosis upon diagnosis with MRT is poor. Given the resistance of MRT to current treatment protocols including cisplatin, and the vulnerability of this young patient population to aggressive therapies, there is a need for novel treatment options. Several members of the inhibitor of apoptosis protein (IAP) family including X‑linked inhibitor of apoptosis (XIAP), cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1/cIAP2), livin and survivin have been implicated in chemotherapy resistance in various malignancies. We have previously demonstrated expression of these IAP family members in a panel of MRT cell lines. In the present study, sensitivity of this same panel of MRT cell lines to small-molecule mediated inhibition of the IAPs via the survivin inhibitor YM155 and the XIAP/cIAP1/cIAP2 inhibitor BV6 was demonstrated. Additionally, both BV6 and the XIAP inhibitor embelin synergistically enhanced cisplatin mediated apoptotic cell death in MRT cell lines, with enhanced caspase-3 cleavage. Importantly, we have demonstrated, for the first time, expression of XIAP, its target caspase-3 and its endogenous inhibitor SMAC in rhabdoid tumour patient tissue. In conclusion, this study provides pre-clinical evidence that IAP inhibition may be a new therapeutic option in MRT.

Morphological Selectivity of a Protein Self-Assembly System with a Repertoire of Diverse Interaction Modes

Multiple metal chelating sites were incorporated onto the second mitochondria-derived activator of caspase (SMAC) building blocks. The combination of different binding sites generated a repertoire of diverse binding modes, among which two different microfilament types (small and large) with distinct patterns were selected under thermodynamic control. Furthermore, the two microfilaments exhibited a pronounced secondary assembly trend due to the potential noncovalent interactions on the protein surfaces. Coupled with stereoselectivity, they presented a strong self-recognition effect and underwent two distinct reassembly patterns. That is, the large filaments self-associated in pairs to form "interlocked chain" structures, while the small ones twisted to form protein helical bundles. This work represents one of the few studies of selective self-assembly of self-assembled protein assemblies. Such an idea may provide inspiration for constructing more sophisticated protein architectures in the future.

A Review of the Current Impact of Inhibitors of Apoptosis Proteins and Their Repression in Cancer

The Inhibitor of Apoptosis (IAP) family possesses the ability to inhibit programmed cell death through different mechanisms; additionally, some of its members have emerged as important regulators of the immune response. Both direct and indirect activity on caspases or the modulation of survival pathways, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), have been implicated in mediating its effects. As a result, abnormal expression of inhibitor apoptosis proteins (IAPs) can lead to dysregulated apoptosis promoting the development of different pathologies. In several cancer types IAPs are overexpressed, while their natural antagonist, the second mitochondrial-derived activator of caspases (Smac), appears to be downregulated, potentially contributing to the acquisition of resistance to traditional therapy. Recently developed Smac mimetics counteract IAP activity and show promise in the re-sensitization to apoptosis in cancer cells. Given the modest impact of Smac mimetics when used as a monotherapy, pairing of these compounds with other treatment modalities is increasingly being explored. Modulation of molecules such as tumor necrosis factor-α (TNF-α) present in the tumor microenvironment have been suggested to contribute to putative therapeutic efficacy of IAP inhibition, although published results do not show this consistently underlining the complex interaction between IAPs and cancer.