Protein and Peptide Letters - Online First

Prolyl 4-hydroxylase beta peptide (P4HB) is a novel diagnostic and prognostic marker associated with cancer progression and clinical outcomes, and it is upregulated in multiple types of cancer cells. However, the influence and potential mechanisms of P4HB on the migration, invasion, and epithelial-mesenchymal transition (EMT) of bladder cancer cells remain unclear. This study aims to clarify the role of P4HB in the migration, invasion, and EMT of bladder cancer cells and to explore its potential mechanism related to the Claudin-1/AMPK/TGF-β1 pathway.

The mRNA and protein expression levels of P4HB were examined in human ureteral epithelial cells (SV-HUC-1) and five bladder cancer cell lines (J82, T24, 5637, UM-UC-3, and RT4). Stable cell lines with P4HB overexpression and knockdown were constructed, and the effects of P4HB on migration, invasion, EMT, and the expression of EMT-related genes in bladder cancer cells were analyzed using wound healing assays, Transwell invasion assays, cellular morphology observations, real-time quantitative PCR, in-cell western blotting, western blotting, and enzyme-linked immunosorbent assays. Furthermore, Claudin-1 siRNA was transfected into P4HB-overexpressing cells to investigate its potential role in P4HB-induced invasion and EMT in bladder cancer cells.

P4HB mRNA and protein expressions were significantly upregulated in human bladder cancer cell lines compared to those in ureteral epithelial cells. Cell migration, invasion, and EMT were significantly promoted in P4HB-overexpressing stable bladder cancer cells and suppressed in P4HB-knockdown cells. Furthermore, interference with P4HB downregulated EMT-related Claudin-1 mRNA and protein expressions and regulated the expression of downstream genes and proteins of Claudin-1. Moreover, interference of Claudin-1 with its siRNA significantly reversed the invasion and EMT induced by P4HB-overexpression, however, the effect of Claudin-1 siRNA was revised by TGF-β1 agonist and AMPK inhibitor.

P4HB promoted migration, invasion, and EMT of bladder cancer cells by activating the Claudin-1/AMPK/TGF-β1-related pathway.

Aloperine (ALO) is a vital alkaloid present in the traditional Chinese herb Sophora alopecuroides, which has demonstrated effective anti-inflammatory activity. However, the effects and the mechanism of action of ALO on cisplatin (CDDP)-induced nephrotoxicity remain unclear.

This study aimed to investigate the effects of ALO on CDDP-induced nephrotoxicity and its potential mechanism of action in vitro.

Cell viability, lactate dehydrogenase cytotoxicity, apoptosis, activity of Caspase-Glo 3/7 and 1, in-cell western blotting, immunohistochemical staining, and enzyme-linked immunosorbent assay (ELISA) were performed to assess the influence of ALO on CDDP-treated kidney cells. Inhibitors of phosphatidylinositol 3-kinase (PI3K, LY294002), protein kinase B (Akt, AKT inhibitor VIII), and nuclear factor kappa B (NFκB, BAY 11-7082) were used to determine their potential mechanisms of action.

The results indicated that ALO significantly reversed the inhibition of cell viability, cytotoxicity, apoptosis, and the release of inflammatory factors induced by CDDP in kidney cells. ALO attenuated the PI3K/AKT/NFκB-mediated pathway activated by CDDP treatment and downregulated the CDDP-induced nucleotide-binding domain, leucine-rich-containing family, pyrin domain–containing-3 (NLRP3) inflammasome. Furthermore, the PI3K and AKT inhibitors diminished the effects of ALO on CDDP-treated kidney cells. Additionally, NFκB inhibitors reversed the effects of the PI3K and AKT inhibitors on ALO in CDDP-treated kidney cells.

These results suggest that ALO protects against CDDP-induced injury in kidney cells by modulating the PI3K/AKT/NFκB-mediated NLRP3 inflammasome.

The shepherin II peptide is characterized by a histidine/glycine-rich sequence. This study aimed to design, express recombinantly, and evaluate the antiviral activity of shepherin II against hepatitis A virus (HAV).

The shepherin II gene was reverse-translated, cloned into the pET-3a vector, and expressed in E. coli BL21 (DE3) pLysS cells induced with 2 mM IPTG. Purification was achieved via cation exchange chromatography, and intact mass analysis using mass spectrometry was carried out. Cytotoxicity on normal Vero cells and antiviral activity on HAV were evaluated.

The mass spectrometry confirmed a primary peptide fragment with a molecular weight of 3,421.30 Da (100% relative abundance). SDS-PAGE verified peptide expression. Cytotoxicity tests on Vero cells showed a CC50 of 219.26 ± 7.91 µg/ml. Antiviral assay revealed an EC50 of 113.92 ± 4.58 µg/ml against HAV, resulting in a selectivity index (SI) of 1.92. This SI indicates limited selectivity compared to the reference drug amantadine, which exhibited an EC50 of 5.67 ± 0.71 µg/ml and an SI of 53.41.

The recombinant expression of shepherin II was successfully achieved and confirmed by mass spectrometry and SDS-PAGE. The peptide showed measurable antiviral activity against HAV.

This study demonstrated the feasibility of recombinant shepherin II production and assessed its antiviral activity. However, the limited selectivity index of shepherin II remains a challenge that needs to be addressed through molecular modification or alternative delivery strategies to improve its clinical potential.

Peak-shouldering elution behavior was a common and unexpected result in bind-and-elute mode Cation Exchange Chromatography (CEX), which may be due to the pH transition during the elution step and the aggregation tendency of target proteins.

Improving the concentration of acid-base pairs in the wash buffers or elution buffers without changing pH or conductivity effectively resolved the peak-shouldering issue in CEX.

In the case of molecule A, the shoulder peak was eliminated in the CEX run by increasing the NaAc-HAc concentration from 50 mM to 100 mM in the elution buffer or from 50 mM to 75 mM in the wash buffer. Higher NaAc-HAc concentrations affect the pH transition in the early stages of the elution step, which may explain the elimination of the shoulder peak. A similar result was observed for molecule B, where increasing the Tris-HCl concentration in the elution buffer from 50 mM to 80 mM also removed the shoulder peak during elution.

The successful elimination of peak-shouldering behavior by increasing acid-base pair concentrations highlights the critical role of buffer capacity in modulating pH transitions during CEX. While this strategy offers a simple and effective solution, further investigation is needed to assess its applicability across diverse protein types and buffer systems.

These results demonstrate that increasing the concentration of acid-base pairs in the elution buffer or wash buffer of CEX using NaAc-HAc or Tris-HCl buffers is an effective strategy for eliminating the shoulder-peak.

The increasing resistance of fungal pathogens to conventional antifungal treatments has led to a global rise in fungal infections, affecting human health (Candida spp.) and agricultural productivity (Colletotrichum and Fusarium spp.). Antimicrobial peptides (AMPs), such as defensins, have gained attention for their potential in controlling these infections due to their broad-spectrum activity.

The aim of this study was to partially purify and characterize the antifungal activity of a defensin-enriched fraction (F3) from Capsicum chinense fruits. Specifically, we sought to evaluate its efficacy against pathogenic fungi and yeasts, and to assess the relative abundance of defensins in the fraction.

The F3 fraction was obtained using ion exchange and molecular exclusion chromatography. Reverse-phase chromatography (HPLC) was then employed for further purification. The antifungal activity of F3 was tested against Colletotrichum, Fusarium, and Candida species. Mass spectrometry was used to identify and characterize the defensin (CcDef3) within the fraction. The presence of the defensin relative to other components was inferred from electrophoretic profiles and peptide analysis.

The F3 fraction exhibited significant antifungal activity, with growth inhibition of Colletotrichum lindemuthianum of 51% and 60.9% at concentrations of 100 and 200 μg mL^-1, respectively. The fraction also inhibited the growth of several Candida species, notably C. nivariensis (93.8%) and C. bracarensis (79.6%) at 100 μg mL^-1. Cell viability analysis indicated a fungistatic effect. Fluorescence microscopy assays showed that F3 induced membrane permeabilization in C. parapsilosis and C. lindemuthianum, and increased ROS production in C. pelliculosa and F. solani. The defensin-rich H8 fraction, containing a 6.5 kDa protein (CcDef3), was identified as a major component via mass spectrometry.

The ongoing development of resistance in fungal strains, particularly Candida species, against traditional antibiotics and antifungals has turned into a significant medical concern and has increased the need for new treatment options.

These results suggest that the F3 fraction, particularly the defensin CcDef3, has potential as an antifungal agent for biotechnological and therapeutic applications. However, further studies are needed to quantify the contribution of CcDef3 relative to other components in the fraction and to fully isolate the defensin for in-depth analysis.