Characterization of the furin cleavage motif for HIV-1 trimeric envelope glycoprotein by intact LC-MS analysis

Colorimetric detection of furin based on enhanced catalytic activity of G-quadruplex/hemin DNAzyme

BACKGROUND

Rapid and sensitive colorimetric detection methods are crucial for diseases diagnosis, particularly those involving proteases like furin, which are implicated in various conditions, including cancer. Traditional detection methods for furin suffer from limitations in sensitivity and practicality for on-site detection, motivating the development of novel detection strategies. Therefore, developing a simple, enzyme-free, and rapid colorimetric analysis method with high sensitivity for furin detection is imperative.

RESULTS

Herein, we have proposed a colorimetric method in this work for the first time to detect furin, leveraging the assembly of G-quadruplex/hemin DNAzyme with enhanced catalytic activity. Specifically, a peptide-DNA conjugate (PDC) comprising a furin-recognition peptide and flanking DNA sequences for signal amplification is designed to facilitate the DNAzyme assembly. Upon furin treatment, PDC cleavage triggers a cyclic catalytic hairpin assembly reaction to form the complementary double-stranded structures by hairpin 1 (HP1) and hairpin 2 (HP2), bringing the G-quadruplex sequence in HP1 closer to hemin on HP2. Moreover, the resulting G-quadruplex/hemin DNAzymes exhibit robust peroxidase-like activity, enabling the catalysis of the colorimetric reaction of ABTS2- for furin detection. Our method demonstrates high sensitivity, rapid response, and compatibility with complex sample matrices, achieving a detection limit as low as 1.1 pM.

SIGNIFICANCE

The DNAzyme reported in this work exhibits robust catalytic activity, enabling high sensitivity and good efficiency for the detection. By eliminating the requirement for exogenous enzymes, our approach enables visual furin detection without expensive instrumentation and reagents, promising significant utility in biomedical and clinical diagnostic applications. Given the various design of peptide sequence and the programmability of DNA, it can be readily applied to analyzing other useful tumor biomarkers.

Structural insights into Furin enzyme inhibition to block SARS-CoV-2 spike protein cleavage: an in-silico approach

This study investigates the binding affinity and interactions of the Furin enzyme with two inhibitors, Naphthofluorescein and decanoyl-RVKR-chloromethylketone (CMK), using molecular docking and molecular dynamics (MD) simulations. Molecular docking results showed binding affinities of - 9.18 kcal/mol for CMK and - 5.39 kcal/mol for Naphthofluorescein. To further understand the stability and conformational changes of these complexes, MD simulations were performed. Despite CMK's favorable docking score, MD simulations revealed that its binding interactions at the Furin-active site were unstable, with significant changes observed during the simulation. In contrast, Naphthofluorescein maintained strong and stable interactions throughout the MD simulation, as confirmed by RMSD and RMSF analyses. The binding-free-energy analysis also supported the stability of Naphthofluorescein. These findings indicate that Naphthofluorescein exhibits greater stability and binding affinity as a Furin inhibitor compared to CMK. The results of this in-silico study suggest that Naphthofluorescein, along with CMK, holds the potential for repurposing as a treatment for COVID-19, subject to further validation through clinical studies.

Detection of Aberrant Glycosylation of Serum Haptoglobin for Gastric Cancer Diagnosis Using a Middle-Up-Down Glycoproteome Platform

Gastric cancer is a frequently occurring cancer and is the leading cause of cancer-related deaths. Recent studies have shown that aberrant glycosylation of serum haptoglobin is closely related to gastric cancer and has enormous potential for use in diagnosis. However, there is no platform with high reliability and high reproducibility to comprehensively analyze haptoglobin glycosylation covering microheterogeneity to macroheterogeneity for clinical applications. In this study, we developed a middle-up-down glycoproteome platform for fast and accurate monitoring of haptoglobin glycosylation. This platform utilizes an online purification of LC for sample desalting, and an in silico haptoglobin glycopeptide library constructed by combining peptides and N-glycans to readily identify glycopeptides. In addition, site-specific glycosylation with glycan heterogeneity can be obtained through only a single MS analysis. Haptoglobin glycosylation in clinical samples consisting of healthy controls (n = 47) and gastric cancer patients (n = 43) was extensively investigated using three groups of tryptic glycopeptides: GP1 (including Asn184), GP2 (including Asn207 and Asn211), and GP3 (including Asn241). A total of 23 individual glycopeptides were determined as potential biomarkers (p < 0.00001). In addition, to improve diagnostic efficacy, we derived representative group biomarkers with high AUC values (0.929 to 0.977) through logistic regression analysis for each GP group. It has been found that glycosylation of haptoglobin is highly associated with gastric cancer, especially the glycosite Asn241. Our assay not only allows to quickly and easily obtain information on glycosylation heterogeneity of a target glycoprotein but also makes it an efficient tool for biomarker discovery and clinical diagnosis.

Development of a RPLC-UV method for monitoring uncleaved HIV-1 envelope glycoprotein

One of the HIV-1 vaccine design efforts has focused on developing a recombinant HIV-1 trimeric envelope glycoprotein (Env) as an immunogen to induce broadly neutralizing antibodies. A native-like immunogen, the BG505.DS.SOSIP.664 gp140 (Env) construct has been well-characterized as a vaccine candidate. This vaccine candidate comprises of three identical gp120 and truncated gp41 subunits that form into a trimer of heterodimers. During production, recombinant Env is expressed as a gp140 precursor polypeptide in which a furin cleavable site is engineered to generate a heterodimer of gp120 and gp41 subunits. Each heterodimer is connected by an intermolecular disulfide bond, and three heterodimers form into a trimer. Furin cleavage is an important factor to mimic native-like HIV-1 Env conformations and is needed to help induce an immune response. Therefore, it is critical to monitor cleavage for ensuring functionality of the Env vaccine product. In this paper, a new RPLC-UV method coupled with reduction was developed to routinely determine the percentage of uncleaved gp140 relative to the cleaved gp120 and gp41 subunits. Baseline separation was achieved among the gp120, gp41 and uncleaved gp140 peaks, thus enabling relative quantification of uncleaved gp140. Overall, this RPLC-UV approach has been successfully applied to support Env vaccine candidate developments.

The Interplay of HIV and Autophagy in Early Infection

HIV/AIDS is still a global threat despite the notable efforts made by the scientific and health communities to understand viral infection, to design new drugs or to improve existing ones, as well as to develop advanced therapies and vaccine designs for functional cure and viral eradication. The identification and analysis of HIV-1 positive individuals that naturally control viral replication in the absence of antiretroviral treatment has provided clues about cellular processes that could interact with viral proteins and RNA and define subsequent viral replication and clinical progression. This is the case of autophagy, a degradative process that not only maintains cell homeostasis by recycling misfolded/old cellular elements to obtain nutrients, but is also relevant in the innate and adaptive immunity against viruses, such as HIV-1. Several studies suggest that early steps of HIV-1 infection, such as virus binding to CD4 or membrane fusion, allow the virus to modulate autophagy pathways preparing cells to be permissive for viral infection. Confirming this interplay, strategies based on autophagy modulation are able to inhibit early steps of HIV-1 infection. Moreover, autophagy dysregulation in late steps of the HIV-1 replication cycle may promote autophagic cell-death of CD4⁺ T cells or control of HIV-1 latency, likely contributing to disease progression and HIV persistence in infected individuals. In this scenario, understanding the molecular mechanisms underlying HIV/autophagy interplay may contribute to the development of new strategies to control HIV-1 replication. Therefore, the aim of this review is to summarize the knowledge of the interplay between autophagy and the early events of HIV-1 infection, and how autophagy modulation could impair or benefit HIV-1 infection and persistence, impacting viral pathogenesis, immune control of viral replication, and clinical progression of HIV-1 infected patients.

A pillar[5]arene-based fluorescent sensor for sensitive detection of L-Met through a dual-site collaborative mechanism

L-Methionine (L-Met) is one of the essential amino acids in human health, efficiently detect L-Met is a significant issue. Herein, a concept "dual-site collaborative recognition" had been successfully introduced into the design and achieved high selective and sensitive recognition of L-Met. In order to realize the "dual-site collaborative recognition", we rationally designed and synthesized an ester functionalized pillar[5]arene-based fluorescent sensor (SP5). And it shows blue Aggregation-induced emission (AIE) fluorescence. In the SP5, the pillar[5]arene group act as C-H···π interactions site, and ester group serve as multi hydrogen bonding acceptor. Interestingly, the SP5 exhibited high selectivity and sensitivity (2.84 × 10^-8 M) towards L-Met based on the collaboration of electron-rich cavernous pillar[5]arene group and ester group through C-H···π and H-bond interactions, respectively. This "dual-site collaborative recognition" mechanism has been investigated by ¹H NMR, ESI-MS and theoretical calculation including frontier orbital (HOMO and LUMO), electrostatic potential (ESP) and the noncovalent interaction (NCI). These theoretical calculations not only support the proposed host-guest recognition mechanism, but also provided visualized information on the "dual-site collaborative recognition" mode. Furthermore, the concept "dual-site collaborative recognition" is an effective strategy for easily detecting biological molecules.