Protein and Peptide Letters - Volume 30, Issue 10, 2023

Background: Brevinin2 HYba5 (Peptide 29) is a novel cationic peptide identified from an endemic frog, Hydrophylax bahuvistara. Staphylococcus aureus and Enterococcus faecalis are troublesome biofilm-forming pathogens associated with nosocomial and community-acquired infections and contribute to the severity of infections associated with implanted devices and chronic wounds. Co-existence of both pathogens in biofilm mode contributes to an increased antibiotic resistance, treatment failure and hence persistent disease burden. Identifying a novel and stable, less toxic compound targeting multispecies biofilm with a lower probability of acquiring resistance in comparison to antibiotics is highly warranted.Objective: Evaluate the activity of Brevinin2 HYba5 against S. aureus and E. faecalis mixed biofilm.Methods: The anti-biofilm activity of peptide 29 was tested by Crystal violet assay, Confocal laser scanning Microscopy (CLSM) and MTT Assay. Cytotoxicity of the peptide was tested in RBC and L929 fibroblast cell line. Biofilm inhibitory activity of the peptide was evaluated at different temperatures, pH, serum and plasma concentrations. The antibiofilm potential of the peptide was tested against polymicrobial biofilm by Fluorescent in situ hybridisation (FISH) and plate counting on HiCrome^TM UTI Agar media.Results: The peptide 29 could inhibit biofilm formation of S. aureus and E. faecalis individually as well as in polymicrobial biofilm at 75 μM concentration. The peptide maintained its antibiofilm potential at different temperatures, serum and plasma concentrations. Activity of the peptide was high at acidic and neutral pH but found to get reduced towards alkaline pH. The peptide is nonhemolytic and does not exhibit significant cytotoxicity against the L929 fibroblast cell line (92.80% cell viability).Conclusion: The biofilm inhibition property makes peptide 29 a promising candidate for the management of S. aureus and E. faecalis biofilm, especially in catheter-associated devices to prevent the initial colonization and thus can ease the burden of pathogenic biofilm-associated infections.

Membrane proteins are important components of the proteome and play key roles in many biological processes, such as signal transduction, material transport, cell recognition, etc. Membrane proteins are involved in several fields, and more and more researchers want to understand them. However, the structural properties of membrane proteins make their recombinant expression yield low. This adversely affects the study of the structure and function of membrane proteins. Therefore, it is crucial to have a comprehensive and up-to-date understanding of membrane protein recombinant expression. Based on the current stage of research on membrane proteins, the article describes the current challenges faced by membrane protein recombinant expression and the solutions that can be applied to lay the foundation for a better study of membrane proteins in the future.

Estrogen plays a key role in the development and progression of many malignant tumours, and the regulation of estrogen levels involves several metabolic pathways. Among these pathways, estrogen sulfotransferase (SULT1E1) is the enzyme with the most affinity for estrogen and is primarily responsible for catalysing the metabolic reaction of estrogen sulphation. Relevant studies have shown significant differences in the expression of SULT1E1 in different malignant tumours, suggesting that SULT1E1 plays a dual role in malignant tumours, both inhibiting the growth of malignant tumours and promoting their development. In addition, the expression level of SULT1E1 may be regulated by a variety of factors, which in turn affect the growth and therapeutic effects of malignant tumours. The aim of this paper is to review the mechanism of action of SULT1E1 in malignant tumours and the mechanisms that are regulated, in order to provide potential targets for the treatment of malignant tumour patients in the future and theoretical support for the realisation of more personalised and effective therapeutic regimens.

The antibacterial and antiviral functions of human defensin 5 lay the foundation for its role as a core host protective component. In addition, HD5 also has the function of inhibiting tumor proliferation and immune regulation. However, everything has two sides; cytotoxic and proinflammatory properties may exist, while HD5 performs physiological functions. Accordingly, the modification and engineering of HD5 are particularly important. Therefore, this review summarizes the role of HD5 in various aspects of host defense, as well as modification of HD5 to ameliorate the biological activity, with a view to promoting the clinical use of HD5.

Background: NK cells play an important role in immune response, immune surveillance, and metabolism regulation. Therefore, NK cells are involved in the occurrence and development of various diseases, such as infectious diseases, cancer, obesity, and diabetes. IL-25 is a special member of the IL-17 family with anti-inflammatory function. IL-25 can regulate inflammatory response and metabolism via various immune cells; however, the role and regulatory mechanism of IL-25 in NK cells are still unclear.Method: In this study, we investigate the role of IL-25 in NK-cell protein profile via 4D label-free mass spectrum and validate the differential proteins via PRM analysis. In addition, GO analysis, KEGG analysis, and other bioinformatic analysis methods are used to explore the enriched function and signal pathway of differentially expressed proteins.Result and Discussion: The GO and KEGG analyses suggest that IL-25 may affect the processes, such as metabolism, thermogenesis, and oxidative phosphorylation of NK cells. There are 7 down-regulated proteins (NCR1, GZMB, PRF1, KLRC1, NDUFA11, LAMTOR5, and IKBIP) and 1 up-regulated protein (PSMD7) in IL-25-treated NK cells versus the control group for PRM validation. Our results indicate that IL-25 may regulate metabolism and other biological processes via NK cells, which will be beneficial in revealing the role and regulatory mechanisms of IL-25 in NK cells in various diseases.Conclusion: Proteomics combined with bioinformatic analysis will help to mine more information hidden behind mass spectrometry data and lay the foundation for finding clinical biomarkers and mechanisms of diseases.

Background: It has been reported that activation of glutamate kainate receptor subunit 2 (GluK2) subunit-containing glutamate receptors and the following Fas ligand(FasL) up-regulation, caspase-3 activation, result in delayed apoptosis-like neuronal death in hippocampus CA1 subfield after cerebral ischemia and reperfusion. Nitric oxide-mediated S-nitrosylation might inhibit the procaspase activation, whereas denitrosylation might contribute to cleavage and activation of procaspases.Objectives: The study aimed to elucidate the molecular mechanisms underlying procaspase-3 denitrosylation and activation following kainic acid (KA)-induced excitotoxicity in rat hippocampus.Methods: S-nitrosylation of procaspase-3 was detected by biotin-switch method. Activation of procaspase-3 was shown as cleavage of procaspase-3 detected by immunoblotting. FasL expression was detected by immunoblotting. Cresyl violets and TdT-mediated dUTP Nick-End Labeling (TUNEL) staining were used to detect apoptosis-like neuronal death in rat hippocampal CA1 and CA3 subfields.Results: KA led to the activation of procaspase-3 in a dose- and time-dependent manner, and the activation was inhibited by KA receptor antagonist NS102. Procaspase-3 was denitrosylated at 3 h after kainic acid administration, and the denitrosylation was reversed by SNP and GSNO. FasL ASODNs inhibited the procaspase-3 denitrosylation and activation. Moreover, thioredoxin reductase (TrxR) inhibitor auranofin prevented the denitrosylation and activation of procaspase-3 in rat hippocampal CA1 and CA3 subfields. NS102, FasL AS-ODNs, and auranofin reversed the KAinduced apoptosis and cell death in hippocampal CA1 and CA3 subfields.Conclusions: KA led to denitrosylation and activation of procaspase-3 via FasL and TrxR. Inhibition of procaspase-3 denitrosylation by auranofin, SNP, and GSNO played protective effects against KA-induced apoptosis-like neuronal death in rat hippocampal CA1 and CA3 subfields. These investigations revealed that the procaspase-3 undergoes an initial denitrosylation process before becoming activated, providing valuable insights into the underlying mechanisms and possible treatment of excitotoxicity.

Background: The ferroptosis inhibitory gene solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) inhibit ferroptosis in carcinoma cells. However, whether SLC7A11 and GPX4 serve as an oncogene in renal cell carcinoma (RCC) remains unclear.Methods: Immunohistochemistry (IHC) assays were performed to assess the expression of SLC7A11 and GPX4 in human RCC tissues. Clinical-pathological analysis was performed to explore the correlation between SLC7A11 and GPX4 expression. Kaplan-Meier survival analysis was performed to characterise the associations between protein expression and patient progressionfree survival (PFS).Results: The upregulation of SLC7A11 and GPX4 was detected by IHC in RCC tissues compared with that in normal renal tissues. Meanwhile, the expression level of SLC7A11 and GPX4 was correlated with tumour diameter and distant metastasis (P<0.05). Kaplan-Meier survival analysis indicated that patients with high SLC7A11 and GPX4 expression levels exhibited worse PFS than those with low SLC7A11 and GPX4 expression levels (P<0.05).Conclusion: The upregulation of SLC7A11 and GPX4 expression was associated with poor prognosis in patients with RCC. SLC7A11 and GPX4 may serve as diagnostic and prognostic biomarkers for patients with RCC.

Background: Pulmonary inflammatory response (PIR) is one of the prognostic risk factors of lung adenocarcinoma (LUAD), with a high mortality rate.Objectives: This study aims to investigate prognostic microRNA (miRNA) to improve clinical prognosis prediction and postoperative inflammation treatment in LUAD patients.Methods: About 201 differentially expressed microRNAs (DE-miRNAs) in LUAD were mined by differential analysis. Univariate/multivariate Cox analyses established and validated prognostic risk miRNAs in TCGA-LUAD. KEGG and GO were used to link risk signatures and biological functions. After 48 hours of exposure to 50 ng/mL LPS, the miR-584-5p/RAB23 regulatory network was verified in qRT-PCR, Western Blotting, and the Luciferase Reporter Assay in A549 cells.Results: MiR-584-5p and miR-101-3p were validated as riskscore correlated with LUAD patients' 1-year survival (p < 0.001) and participate in multiple inflammation-related pathways. RAB23, a RAS oncogene, is involved in inflammatory MAPK signaling. Evidence suggests that miR-584-5p regulates inflammation in LUAD by targeting RAB23. A549 cells were transfected with the mimic and inhibitor of miR-584-5p, confirming the negative regulatory relationship between miR-584-5p and RAB23. In the A549 induced by LPS, either over-expression of miR-584-5p or knock-down of RAB23 expression decreased the expression of inflammatory factors and increased cell viability.Conclusion: Prognostic-related risk miR-584-5p can regulate the expression of RAB23 at both the mRNA and protein levels, thereby influencing the development of a PIR in LUAD. This will have significant implications for the clinical prognosis prediction and therapy decision-making of LUAD patients with PIR.