Fungal Secondary Metabolites as Inhibitors of the Ubiquitin-Proteasome System

Genome-wide transcriptome analysis of toxigenic Fusarium verticillioides in response to variation of temperature and water activity on maize kernels

Fusarium verticillioides is one of the important mycotoxigenic pathogens of maize since it causes severe yield losses and produces fumonisins (FBs) to threaten human and animal health. Previous studies showed that temperature and water activity (aw) are two pivotal environmental factors affecting F. verticillioides growth and FBs production during maize storage. However, the genome-wide transcriptome analysis of differentially expressed genes (DEGs) in F. verticillioides under the stress combinations of temperature and aw has not been studied in detail. In this study, DEGs of F. verticillioides and their related regulatory pathways were analyzed in response to the stress of temperature and aw combinations using RNA-Seq. The results showed that the optimal growth conditions for F. verticillioides were 0.98 aw and 25 °C, whereas the highest per-unit yield of the fumonisin B1 (FB1) was observed at 0.98 aw and 15 °C. The RNA-seq analysis showed that 9648 DEGs were affected by temperature regardless of aw levels, whereas only 218 DEGs were affected by aw regardless of temperature variations. Gene Ontology (GO) analysis revealed that a decrease in temperature at both aw levels led to a significant upregulation of genes associated with 24 biological processes, while three biological processes were downregulated. Furthermore, when aw was decreased at both temperatures, seven biological processes were significantly upregulated and four were downregulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the genes, whose expression was upregulated when the temperature decreased, were predominantly associated with the proteasome pathway, whereas the genes, whose expression was downregulated when the aw decreased, were mainly linked to amino acid metabolism. For the FB1, except for the FUM15 gene, the other 15 biosynthetic-related genes were highly expressed at 0.98 aw and 15 °C. In addition, the expression pattern analysis of other biosynthetic genes involved in secondary metabolite production and regulation of fumonisins production was conducted to explore how this fungus responds to the stress combinations of temperature and aw. Overall, this study primarily examines the impact of temperature and aw on the growth of F. verticillioides and its production of FB1 using transcriptome data. The findings presented here have the potential to contribute to the development of novel strategies for managing fungal diseases and offer valuable insights for preventing fumonisin contamination in food and feed storage.

Altered Expression of Two Small Secreted Proteins (ssp4 and ssp6) Affects the Degradation of a Natural Lignocellulosic Substrate by Pleurotus ostreatus

Pleurotus ostreatus is a white-rot fungus that can degrade lignin in a preferential manner using a variety of extracellular enzymes, including manganese and versatile peroxidases (encoded by the vp1-3 and mnp1-6 genes, respectively). This fungus also secretes a family of structurally related small secreted proteins (SSPs) encoded by the ssp1-6 genes. Using RNA sequencing (RNA-seq), we determined that ssp4 and ssp6 are the predominant members of this gene family that were expressed by P. ostreatus during the first three weeks of growth on wheat straw. Downregulation of ssp4 in a strain harboring an ssp RNAi construct (KDssp1) was then confirmed, which, along with an increase in ssp6 transcript levels, coincided with reduced lignin degradation and the downregulation of vp2 and mnp1. In contrast, we observed an increase in the expression of genes related to pectin and side-chain hemicellulose degradation, which was accompanied by an increase in extracellular pectin-degrading capacity. Genome-wide comparisons between the KDssp1 and the wild-type strains demonstrated that ssp silencing conferred accumulated changes in gene expression at the advanced cultivation stages in an adaptive rather than an inductive mode of transcriptional response. Based on co-expression networking, crucial gene modules were identified and linked to the ssp knockdown genotype at different cultivation times. Based on these data, as well as previous studies, we propose that P. ostreatus SSPs have potential roles in modulating the lignocellulolytic and pectinolytic systems, as well as a variety of fundamental biological processes related to fungal growth and development.

Functional Role of RING Ubiquitin E3 Ligase VdBre1 and VdHrd1 in the Pathogenicity and Penetration Structure Formation of Verticillium dahliae

Verticillium dahliae, a virulent soil-borne fungus, elicits Verticillium wilt in numerous dicotyledonous plants through intricate pathogenic mechanisms. Ubiquitination, an evolutionarily conserved post-translational modification, marks and labels proteins for degradation, thereby maintaining cellular homeostasis. Within the ubiquitination cascade, ubiquitin ligase E3 demonstrates a unique capability for target protein recognition, a function often implicated in phytopathogenic virulence. Our research indicates that two ubiquitin ligase E3s, VdBre1 and VdHrd1, are intrinsically associated with virulence. Our findings demonstrate that the deletion of these two genes significantly impairs the ability of V. dahliae to colonize the vascular bundles of plants and to form typical penetration pegs. Furthermore, transcriptomic analysis suggests that VdBre1 governs the lipid metabolism pathway, while VdHrd1 participates in endoplasmic-reticulum-related processes. Western blot analyses reveal a significant decrease in histone ubiquitination and histone H3K4 trimethylation levels in the ΔVdBre1 mutant. This research illuminates the function of ubiquitin ligase E3 in V. dahliae and offers fresh theoretical perspectives. Our research identifies two novel virulence-related genes and partially explicates their roles in virulence-associated structures and gene regulatory pathways. These findings augment our understanding of the molecular mechanisms inherent to V. dahliae.

FBXO28 promotes proliferation, invasion, and metastasis of pancreatic cancer cells through regulation of SMARCC2 ubiquitination

The E3 ligase F-box only protein 28 (FBXO28) belongs to the F-box family of proteins that play a critical role in tumor development. However, the potential function of FBXO28 in pancreatic cancer (PC) and its molecular mechanism remain unclear. In this study, we examined FBXO28 expression in PC and its biological role and explored the mechanism of FBXO28-mediated proliferation, invasion, and metastasis of PC cells. Compared with paracancerous tissues and human normal pancreatic ductal epithelial cells, FBXO28 was highly expressed in PC tissues and cell lines. High expression of FBXO28 was negatively correlated with the survival prognosis of patients with PC. Functional assays indicated that FBXO28 promoted PC cell proliferation, invasion, and metastasis in vitro and in vivo. Furthermore, immunoprecipitation-mass spectrometry was used to identify SMARCC2 as the target of FBXO28; upregulation of SMARCC2 can reverse the effect of overexpression of FBXO28 on promoting the proliferation, invasion, and metastasis of PC cells. Mechanistically, FBXO28 inhibited SMARCC2 expression in post-translation by increasing SMARCC2 ubiquitination and protein degradation. In conclusion, FBXO28 has a potential role in PC, possibly promoting PC progression through SMARCC2 ubiquitination. Thus, FBXO28 might be a potential treatment target in PC.

New trends in synthetic drugs and natural products targeting 20S proteasomes in cancers

Cancer is a global health challenge that remains to be a field of extensive research aiming to find new anticancer therapeutics. The 20S proteasome complex is one of the targets of anticancerdrugs, as it is correlated with several cancer types. Herein, we aim to discuss the 20S proteasome subunits and investigatethe currently studied proteasome inhibitors targeting the catalytically active proteasome subunits. In this review, we summarize the proteindegradation mechanism of the 20S proteasome complex and compareit with the 26S proteasome complex. Afterwards, the localization of the 20S proteasome is summarized as well as its use as a diagnosticandprognostic marker. The FDA-approved proteasome inhibitors (PIs) under clinical trials are summarized and their current limited use in solid tumors is also reviewed in addition to the expression of theβ5 subunit in differentcell lines. The review discusses in-silico analysis of the active subunit of the 20S proteasome complex. For development of new proteasome inhibitor drugs, the natural products inhibiting the 20S proteasome are summarized, as well as novel methodologies and challenges for the natural product discovery and current information about the biosynthetic gene clusters encoding them. We herein briefly summarize some resistancemechanismsto the proteasomeinhibitors. Additionally, we focus on the three main classes of proteasome inhibitors: 1] boronic acid, 2] beta-lactone and 3] epoxide inhibitor classes, as well as other PI classes, and their IC₅₀ values and their structure-activity relationship (SAR). Lastly,we summarize several future prospects of developing new proteasome inhibitors towards the treatment of tumors, especially solid tumors.

Ganoderic Acid A and Its Amide Derivatives as Potential Anti-Cancer Agents by Regulating the p53-MDM2 Pathway: Synthesis and Biological Evaluation

The mechanisms of action of natural products and the identification of their targets have long been a research hotspot. Ganoderic acid A (GAA) is the earliest and most abundant triterpenoids discovered in Ganoderma lucidum. The multi-therapeutic potential of GAA, in particular its anti-tumor activity, has been extensively studied. However, the unknown targets and associated pathways of GAA, together with its low activity, limit in-depth research compared to other small molecule anti-cancer drugs. In this study, GAA was modified at the carboxyl group to synthesize a series of amide compounds, and the in vitro anti-tumor activities of the derivatives were investigated. Finally, compound A2 was selected to study its mechanism of action because of its high activity in three different types of tumor cell lines and low toxicity to normal cells. The results showed that A2 could induce apoptosis by regulating the p53 signaling pathway and may be involved in inhibiting the interaction of MDM2 and p53 by binding to MDM2 (K_D = 1.68 µM). This study provides some inspiration for the research into the anti-tumor targets and mechanisms of GAA and its derivatives, as well as for the discovery of active candidates based on this series.

Integrated approach for studying bioactive compounds from Cladosporium spp. against estrogen receptor alpha as breast cancer drug target

Cladosporium spp. have been reported for their great diversity of secondary metabolites which represent as a prominent base material for verifying the biological activities. Several bioactive compounds which have antimicrobial, cytotoxic, quorum sensing inhibitory and phytotoxic activities have been isolated from Cladosporium species. Most of them are still needed to be explored for their anticancer properties. Therefore, the present study is focused on screening and identifying the bioactive compounds of Cladosporium spp. for their anticancer activity via the integrated approaches of Molecular Docking (MD), Molecular Dynamics Simulation (MDS) and Density Functional Theory (DFT) studies. A total of 123 bioactive compounds of Cladosporium spp. were explored for their binding affinity with the selected breast cancer drug target receptor such as estrogen receptor alpha (PDB:6CBZ). The Molecular Docking studies revealed that amongst the bioactive compounds screened, Altertoxin X and Cladosporol H showed a good binding affinity of - 10.5 kcal/mol and - 10.3 kcal/mol, respectively, with the estrogen receptor alpha when compared to the reference compound (17[Formula: see text]-Estradiol: - 10.2 kcal/mol). The MDS study indicated the stable binding patterns and conformation of the estrogen receptor alpha-Altertoxin X complex in a stimulating environment. In addition, in silico absorption, distribution, metabolism, excretion and toxicity (ADMET) study suggested that Altertoxin X has a good oral bioavailability with a high LD[Formula: see text] value of 2.375 mol/kg and did not cause any hepatotoxicity and skin sensitization. In summary, the integrated approaches revealed that Altertoxin X possesses a promising anticancer activity and could serve as a new therapeutic drug for breast cancer treatment.

Role of ABCA1 in Cardiovascular Disease

Cholesterol homeostasis plays a significant role in cardiovascular disease. Previous studies have indicated that ATP-binding cassette transporter A1 (ABCA1) is one of the most important proteins that maintains cholesterol homeostasis. ABCA1 mediates nascent high-density lipoprotein biogenesis. Upon binding with apolipoprotein A-I, ABCA1 facilitates the efflux of excess intracellular cholesterol and phospholipids and controls the rate-limiting step of reverse cholesterol transport. In addition, ABCA1 interacts with the apolipoprotein receptor and suppresses inflammation through a series of signaling pathways. Thus, ABCA1 may prevent cardiovascular disease by inhibiting inflammation and maintaining lipid homeostasis. Several studies have indicated that post-transcriptional modifications play a critical role in the regulation of ABCA1 transportation and plasma membrane localization, which affects its biological function. Meanwhile, carriers of the loss-of-function ABCA1 gene are often accompanied by decreased expression of ABCA1 and an increased risk of cardiovascular diseases. We summarized the ABCA1 transcription regulation mechanism, mutations, post-translational modifications, and their roles in the development of dyslipidemia, atherosclerosis, ischemia/reperfusion, myocardial infarction, and coronary heart disease.