Target Proteases Research Articles

An Introductory Guide to Protease Sensitive Linker Design Using Matrix Metalloproteinase 13 as an Example.

Proteases play a crucial role, not only in physiological, but also in pathological processes, such as cancer, inflammation, arthritis, Alzheimer's, and infections, to name but a few. Their ability to cleave peptides can be harnessed for a broad range of biotechnological purposes. To do this efficiently, it is essential to find an amino acid sequence that meets the necessary requirements, including interdependent factors like specificity, selectivity, cleavage kinetics, or synthetic accessibility. Cleavage sequences from natural substrates of the protease may not be optimal in terms of specificity and selectivity, which is why these frequently require arduous and sometimes unsuccessful optimization such as by iterative exchange of single amino acids. Hence, here we describe the systematic design of protease sensitive linkers (PSLs)─peptide sequences specifically cleaved by a target protease─guided by the mass spectrometry based determination of target protease specific cleavage sites from a proteome-based peptide library. It includes a procedure for identifying bespoke PSL sequences, their optimization, synthesis, and validation and introduces a program that can indicate potential cleavage sites by hundreds of enzymes in any arbitrary amino acid sequence. Thereby, we provide an introduction to PSL design, illustrated by the example of matrix metalloproteinase 13 (MMP13). This introduction can serve as a guide and help to greatly accelerate the development and use of protease-sensitive linkers in diverse applications.

Arabidopsis SBT5.2 and SBT1.7 subtilases mediate C-terminal cleavage of flg22 epitope from bacterial flagellin

Plants initiate specific defense responses by recognizing conserved epitope peptides within the flagellin proteins derived from bacteria. Proteolytic cleavage of epitope peptides from flagellin by plant apoplastic proteases is thought to be crucial for the perception of the epitope by the plant receptor. However, the identity of the plant proteases involved in this process remains unknown. Here, we establish an efficient identification system for the target proteases in Arabidopsis apoplastic fluid; the method employs native two-dimensional electrophoresis followed by an in-gel proteolytic assay using a fluorescence-quenching peptide substrate. We designed a substrate to specifically detect proteolytic activity at the C-terminus of the flg22 epitope in flagellin and identified two plant subtilases, SBT5.2 and SBT1.7, as specific proteases responsible for the C-terminal cleavage of flg22. In the apoplastic fluid of Arabidopsis mutant plants deficient in these two proteases, we observe a decrease in the C-terminal cleavage of the flg22 domain from flagellin, leading to a decrease in the efficiency of flg22 epitope liberation. Consequently, defensive reactive oxygen species (ROS) production is delayed in sbt5.2 sbt1.7 double-mutant leaf disks compared to wild type following flagellin exposure.

Dual Strategy to Design New Agents Targeting Schistosoma mansoni: Advancing Phenotypic and SmCB1 Inhibitors for Improved Efficacy.

In this study, we have identified and optimized two lead structures from an in-house screening, with promising results against the parasitic flatworm Schistosoma mansoni and its target protease S. mansoni cathepsin B1 (SmCB1). Our correlation analysis highlighted the significance of physicochemical properties for the compounds' in vitro activities, resulting in a dual approach to optimize the lead structures, regarding both phenotypic effects in S. mansoni newly transformed schistosomula (NTS), adult worms, and SmCB1 inhibition. The optimized compounds from both approaches ("phenotypic" vs "SmCB1" approach) demonstrated improved efficacy against S. mansoni NTS and adult worms, with 2h from the "SmCB1" approach emerging as the most potent compound. 2h displayed nanomolar inhibition of SmCB1 (Ki = 0.050 μM) while maintaining selectivity toward human off-target cathepsins. Additionally, the greatly improved efficacy of compound 2h toward S. mansoni adults (86% dead worms at 10 μM, 68% at 1 μM, 35% at 0.1 μM) demonstrates its potential as a new therapeutic agent for schistosomiasis, underlined by its improved permeability.

Covalent activity-based probes for imaging of serine proteases.

Serine proteases are one of the largest mechanistic classes of proteases. They regulate a plethora of biochemical pathways inside and outside the cell. Aberrant serine protease activity leads to a wide variety of human diseases. Reagents to visualize these activities can be used to gain insight into the biological roles of serine proteases. Moreover, they may find future use for the detection of serine proteases as biomarkers. In this review, we discuss small molecule tools to image serine protease activity. Specifically, we outline different covalent activity-based probes and their selectivity against various serine protease targets. We also describe their application in several imaging methods.

Glycoprotein non-metastatic melanoma protein B promotes tumor growth and is a biomarker for lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a rare, progressive cystic lung disease affecting almost exclusively female-sexed individuals. The cysts represent regions of lung destruction caused by smooth muscle tumors containing mutations in one of the two tuberous sclerosis (TSC) genes. mTORC1 inhibition slows but does not stop LAM advancement. Furthermore, monitoring disease progression is hindered by insufficient biomarkers. Therefore, new treatment options and biomarkers are needed. LAM cells express melanocytic markers, including glycoprotein non-metastatic melanoma protein B (GPNMB). The function of GPNMB in LAM is currently unknown; however, GPNMB's unique cell surface expression on tumor versus benign cells makes GPNMB a potential therapeutic target, and persistent release of its extracellular ectodomain suggests potential as a serum biomarker. Here, we establish that GPNMB expression is dependent on mTORC1 signaling, and that GPNMB regulates TSC2-null tumor cell invasion in vitro. Further, we demonstrate that GPNMB enhances TSC2-null xenograft tumor growth in vivo, and that ectodomain release is required for this xenograft growth. We also show that GPNMB's ectodomain is released from the cell surface of TSC2-null cells by proteases ADAM10 and 17, and we identify the protease target sequence on GPNMB. Finally, we demonstrate that GPNMB's ectodomain is present at higher levels in LAM patient serum compared to healthy controls and that ectodomain levels decrease with mTORC1 inhibition, making it a potential LAM biomarker.

Synthetic protein protease sensor platform.

Introduction: Protease activity can serve as a highly specific biomarker for application in health, biotech, and beyond. The aim of this study was to develop a protease cleavable synthetic protein platform to detect protease activity in a rapid cell-free setting. Methods: The protease sensor is modular, with orthogonal peptide tags at the N and C terminal ends, which can be uncoupled via a protease responsive module located in between. The sensor design allows for several different readouts of cleavage signal. A protein 'backbone' [Green fluorescent protein (GFP)] was designed in silico to have both a C-terminal Flag-tag and N-Terminal 6x histidine tag (HIS) for antibody detection. A protease cleavage site, which can be adapted for any known protease cleavage sequence, enables the uncoupling of the peptide tags. Three different proteases-Tobacco, Etch Virus (TEV), the main protease from coronavirus SARS-COV-2 (Mpro) and Matrix Metallopeptidase 9 (MMP9)-a cancer-selective human protease-were examined. A sandwich Enzyme-Linked Immunosorbent Assay (ELISA) was developed based on antibodies against the HIS and Flag tags. As an alternative readout, a C-terminal quencher peptide separable by protease cleavage from the GFP was also included. Purified proteins were deployed in cell-free cleavage assays with their respective protease. Western blots, fluorescence assays and immunoassay were performed on samples. Results: Following the design, build and validation of protein constructs, specific protease cleavage was initially demonstrated by Western blot. The novel ELISA proved to afford highly sensitive detection of protease activity in all cases. By way of alternative readout, activation of fluorescence signal upon protease cleavage was also demonstrated but did not match the sensitivity provided by the ELISA method. Discussion: This platform, comprising a protease-responsive synthetic protein device and accompanying readout, is suitable for future deployment in a rapid, low-cost, lateral flow setting. The modular protein device can readily accommodate any desired protease-response module (target protease cleavage site). This study validates the concept with three disparate proteases and applications-human infectious disease, cancer and agricultural crop infection.

Computational Approaches Molecular Docking and MD Simulation Establishes the Potential COVID-19 Main Protease Inhibitors from Natural Products

Aim: COVID-19 was classified as a pandemic by the World Health Organization (WHO) on March 11, 2020. No reliable cure, however, was found. To prevent viral replication, complementary therapy with antiviral and antimalarial medications were used. However, due to their synthetic origin, they have a lot of side effects. To overcome this bane natural origin drugs were repositioned. Background: As repositioned drugs do not undergo a pro-long process of pre-clinical trial, hence, they play an excellent role in the spillover of pathogens. The main protease (6LU7) enzyme found in severe acute respiratory syndrome coronavirus-2 (SAR-CoV-2) is essential for viral replication. Thus, it acts as a hotspot in drug discovery. Objective: A molecular docking computational approach was used to determine the ability of the binding contract between the selected 3D-models of COVID-19 protease target and proposed natural compounds pristimerin, amazoquinone, kendomycin, celastrol, 20-epi-isoguesterinol, phenanthrenequinone, taxodione, maytenoquinone, hippeastrine, ammothamnine, 28-hydroxy isoiguesterin, hemanthamine, alisol-B, stigmasterol, β-pinene,and β-sitosterol through Autodock v.1.5.6 software. Method: The present study is designed to perform in-silico studies using molecular docking (Autodock tool v.1.5.6), Discovery Studio 2017 R2 client, Patch dock, SWISS-ADME prediction, and molecular simulation (Desmond simulation package of Schrodinger) between 6LU7 and natural origin compounds. Result: The results of docking study performed between 6LU7 and compounds pristimerin, amazoquinone, kendomycin, celastrol, 20-epi-isoguesterinol, phenanthrenequinone, taxodione, maytenoquinone, hippeastrine, ammothamnine, 28-hydroxy isoiguesterin, hemanthamine, alisol-B, stigmasterol, β-pinene, and β-sitosterol, showed binding energy as -9.68, -7.34, -5.34, -4.63, -4.24, -4.13, -4.08, -3.85, -3.83, -3.7, -3.6, -3.57, -3.54, -3.39, -3.18, and -3.03 Kcal/mol, respectively. It can be shown that the Pristimerin-6LU7 protein complex was maintained throughout the simulation since the ligand RMSDs varied with a maximum value of 4.2Å during the first 10 ns, followed by more stable interactions for the remaining time of the simulation. Conclusion: The goal of the current work was to find inhibitors for both prophylactic and therapeutic usage in COVID-19 patients.

Molecular docking and molecular dynamic simulation-based phytoconstituents against SARS-CoV-2 with dual inhibition of the primary protease targets

A novel coronavirus has caused major health problems and is spreading globally. The main protease enzyme plays a significant role in the number of copies of ss-RNA produced during the proteolytic cleavage of polypeptides. This work aims to find possible dual inhibitors of the 3-Chymotrypsin-like proteases PDB-6W63 and 6LU7 which increase efficiency and faster inhibition activity. By using an in-silico technique, polyphenols are molecularly docked against these targets to inhibit protease enzymes. Some polyphenols, such as pelargonidin and naringin, have significant dual inhibition characteristics with remarkable binding affinities with active scaffolds of both proteins, which have important ADMET parameters. These organic molecules are strongly bonded with amino acids of protein via mostly hydrogen bonding. These polyphenols also have outstanding docking scores and MMGBSA energies. The validity of the docking score was evaluated using a molecular dynamics simulation that assessed the stability of the complex. With the aid of computer-aided drug design, we hypothesise that the dual inhibition of compounds pelargonidin and naringin could effectively and potentially oppose SARS-CoV-2.

Multiplexed detection of viral proteases through dual response peptide-assisted nanopore sensing

Owing to their central roles in viral replication, main protease (Mpro) and papain-like protease (PLpro) are promising biomarkers for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hence, the simultaneous sensing of Mpro and PLpro activities is a valuable approach for SARS-CoV-2 detection. Herein, we developed a dual response peptide probe for simultaneously monitoring the protease activities of Mpro and PLpro using a single aerolysin nanopore. The target proteases can specifically digest the probe at the corresponding cleavage sites, releasing the output peptide fragments composed of different amino acids. These fragments generated clearly distinguishable blocking currents in nanopore recording that can be assigned to each analyte, allowing accurate differentiation among multiple proteases. The approach enabled the sensitive detection of Mpro and PLpro activity without the need for any amplification or labeling. Furthermore, with excellent discrimination ability, the method can be applied to evaluate the activity of the two model proteases against a background of exhaled breath condensate. Importantly, since peptides with specific sequences serve as catalytic substrates of multiple enzymes, the proposed strategy would be applicable for accurate and multiplex quantification of different types of enzymes, which is critical for non-invasive early disease diagnosis.

Recent Advances on Targeting Proteases for Antiviral Development.

Viral proteases are an important target for drug development, since they can modulate vital pathways in viral replication, maturation, assembly and cell entry. With the (re)appearance of several new viruses responsible for causing diseases in humans, like the West Nile virus (WNV) and the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), understanding the mechanisms behind blocking viral protease's function is pivotal for the development of new antiviral drugs and therapeutical strategies. Apart from directly inhibiting the target protease, usually by targeting its active site, several new pathways have been explored to impair its activity, such as inducing protein aggregation, targeting allosteric sites or by inducing protein degradation by cellular proteasomes, which can be extremely valuable when considering the emerging drug-resistant strains. In this review, we aim to discuss the recent advances on a broad range of viral proteases inhibitors, therapies and molecular approaches for protein inactivation or degradation, giving an insight on different possible strategies against this important class of antiviral target.

Polymorphic Structure Determination of the Macrocyclic Drug Paritaprevir by MicroED.

Paritaprevir is an orally bioavailable, macrocyclic drug used for treating chronic Hepatitis C virus (HCV) infection. Its structures have been elusive to the public until recently when one of the crystal forms is solved by microcrystal electron diffraction (MicroED). In this work, the MicroED structures of two distinct polymorphic crystal forms of paritaprevir are reported from the same experiment. The different polymorphs show conformational changes in the macrocyclic core, as well as the cyclopropyl sulfonamide and methyl pyrazinamide substituents. Molecular docking shows that one of the conformations fits well into the active site pocket of the HCV non-structural 3/4A (NS3/4A) serine protease target, and can interact with the pocket and catalytic triad via hydrophobic interactions and hydrogen bonds. These results can provide further insight for optimization of the binding of acyl sulfonamide inhibitors to the HCV NS3/4A serine protease. In addition, this also demonstrates the opportunity to derive different polymorphs and distinct macrocycle conformations from the same experiments using MicroED.

Tick cysteine protease inhibitors suppress immune responses in mannan-induced psoriasis-like inflammation.

Protease inhibitors regulate various biological processes and prevent host tissue/organ damage. Specific inhibition/regulation of proteases is clinically valuable for treating several diseases. Psoriasis affects the skin in the limbs and scalp of the body, and the contribution of cysteine and serine proteases to the development of skin inflammation is well documented. Cysteine protease inhibitors from ticks have high specificity, selectivity, and affinity to their target proteases and are efficient immunomodulators. However, their potential therapeutic effect on psoriasis pathogenesis remains to be determined. Therefore, we tested four tick cystatins (Sialostatin L, Sialostatin L2, Iristatin, and Mialostatin) in the recently developed, innate immunity-dependent mannan-induced psoriasis model. We explored the effects of protease inhibitors on clinical symptoms and histological features. In addition, the number and percentage of immune cells (dendritic cells, neutrophils, macrophages, and γδT cells) by flow cytometry, immunofluorescence/immunohistochemistry and, the expression of pro-inflammatory cytokines (TNF-a, IL-6, IL-22, IL-23, and IL-17 family) by qPCR were analyzed using skin, spleen, and lymph node samples. Tick protease inhibitors have significantly decreased psoriasis symptoms and disease manifestations but had differential effects on inflammatory responses and immune cell populations, suggesting different modes of action of these inhibitors on psoriasis-like inflammation. Thus, our study demonstrates, for the first time, the usefulness of tick-derived protease inhibitors for treating skin inflammation in patients.

First person – Tanja Müller

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Tanja Müller is first author on ‘ The neuronal transcription factor MEIS2 is a calpain-2 protease target’, published in JCS. Tanja conducted the research described in this article while a PhD student in Prof. Dr Dorothea Schulte's lab at the Institute of Neurology (Edinger Institute), University Hospital Frankfurt, Germany. She is now a postdoc and co-lead of the Translational Neurooncology Junior Group in the lab of Dr Ann-Christin Hau at the Translational Neurooncology Group at the University Hospital Frankfurt, Germany. Her current research focuses on the identification of invasion-promoting genes in high-grade glial tumors.

Identification of Triazolopyrimidinyl Scaffold SARS-CoV-2 Papain-Like Protease (PLpro) Inhibitor.

The global impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its companion disease, COVID-19, has reminded us of the importance of basic coronaviral research. In this study, a comprehensive approach using molecular docking, in vitro assays, and molecular dynamics simulations was applied to identify potential inhibitors for SARS-CoV-2 papain-like protease (PLpro), a key and underexplored viral enzyme target. A focused protease inhibitor library was initially created and molecular docking was performed using CmDock software (v0.2.0), resulting in the selection of hit compounds for in vitro testing on the isolated enzyme. Among them, compound 372 exhibited promising inhibitory properties against PLpro, with an IC50 value of 82 ± 34 μM. The compound also displayed a new triazolopyrimidinyl scaffold not yet represented within protease inhibitors. Molecular dynamics simulations demonstrated the favorable binding properties of compound 372. Structural analysis highlighted its key interactions with PLpro, and we stress its potential for further optimization. Moreover, besides compound 372 as a candidate for PLpro inhibitor development, this study elaborates on the PLpro binding site dynamics and provides a valuable contribution for further efforts in pan-coronaviral PLpro inhibitor development.

Repurposing of eluxadoline as a SARS-CoV-2 main protease inhibitor: E-Pharmacophore based virtual screening, molecular docking, MM-GBSA calculations, and molecular dynamics simulations studies

This study presents a comprehensive computational approach aimed at repurposing an FDA-approved drug, retrieved from the DrugBank database, as a potential inhibitor of the SARS-CoV-2 main protease, a crucial target for antiviral drug development. Utilizing e-pharmacophore-based virtual screening, molecular docking, MM-GBSA calculations, and molecular dynamics simulations, the key interactions and binding affinities of Eluxadoline, the top-ranked drug, with the target protease were elucidated. The findings provide valuable insights into the molecular mechanisms underlying Eluxadoline’s inhibitory activity against the SARS-CoV-2 main protease, highlighting its potential for combating emerging viral threats. Further experimental validation is recommended to confirm and optimize Eluxadoline’s efficacy, paving the way for its potential clinical application in the ongoing battle against COVID-19. This study underscores the significance of repurposing existing drugs as a promising strategy for urgently needed therapeutics against global pandemics like COVID-19.

DNA encoded peptide library for SARS-CoV-2 3CL protease covalent inhibitor discovery and profiling.

Covalent protease inhibitors serve as valuable tools for modulating protease activity and are essential for investigating the functions of protease targets. These inhibitors typically consist of a recognition motif and a covalently reactive electrophile. Substrate peptides, featuring residues capable of fitting into the substrate pockets of proteases, undergo chemical modification at the carbonyl carbon of the P1 residue with an electrophile and have been widely applied in the development of covalent inhibitors. In this study, we utilized a DNA-encoded peptide library to replicate peptide binder sequences and introduced a vinyl sulfone warhead at the C-termini to construct the DNA-encoded peptide covalent inhibitor library (DEPCIL) for targeting cysteine proteases. Screening results toward 3CL protease demonstrated the efficacy of this library, not only in identifying protease inhibitors, but also in discovering amino acids that can conform to aligned protease pockets. The identified peptide sequences provide valuable insight into the amino acid preferences within substrate binding pockets, and our novel technology is indicative of the potential for similar strategies to discover covalent inhibitors and profile binding preferences of other proteases.

Comparative analysis of matrix metalloproteinases by zymography in patients with colorectal carcinoma.

Zymography is an electrophoretic method in which proteins are separated in a polyacrylamide gel in the presence of sodium dodecyl sulfate (SDS-PAGE). This method is used for the detection of enzymatic activity and molecular characterization of proteins. In contrast to the standard SDS-PAGE method, a substrate is incorporated into the gel during zymography, which is subsequently cleaved by target proteases. Many studies have focused on the development and progression of inflammatory diseases affecting the gastrointestinal tract, emphasizing the role of the largest group of proteases, matrix metalloproteinases (MMPs). The most used classification of this group of enzymes (by researchers in MMP biology) is based in part on the historical evaluation of the substrate specificity of MMPs and in part on the cellular localization of MMPs. MMPs are thus classified into the groups of collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs (MT-MMPs), and others. An important group of MMPs are gelatinases which are involved in the breakdown of collagen type IV and gelatin of extracellular matrix and participate in the regulation of various physiological or pathological processes such as morphogenesis, angiogenesis, tissue repair, cirrhosis, arthritis, and metastasis. The present study's objective was to determine the amount of active MMP-9 and MMP-2 forms in tissue samples using zymography. The patient group was according to histology findings divided into the benign tumor (control) group (8 patients), and the malignant tumor group (24 patients). The respondents in the malignant tumor group were further divided according to the standard TNM classification. The results of this study confirmed that MMP-2, unlike MMP-9, can be used as a prognostic biomarker of CRC, because only the expression of active MMP-2 confirmed statistically significant differences between individual stages of CRC. Moreover, MMP-2 seems to play a more important role in higher stages of CRC. Substantial disparities in the determination of active MMPs between the observed groups support the assumption for the integration of zymography into clinical diagnostics of CRC together with molecular and other studies.

Probing of the reactive center loop region of alpha-1-antitrypsin by mutagenesis predicts new type-2 dysfunctional variants.

Lung disease in alpha-1-antitrypsin deficiency (AATD) mainly results from insufficient control of the serine proteases neutrophil elastase (NE) and proteinase-3 due to reduced plasma levels of alpha-1-antitrypsin (AAT) variants. Mutations in the specificity-determining reactive center loop (RCL) of AAT would be predicted to minimally affect protein folding and secretion by hepatocytes but can impair anti-protease activity or alter the target protease. These properly secreted but dysfunctional 'type-2' variants would not be identified by common diagnostic protocols that are predicated on a reduction in circulating AAT. This has potential clinical relevance: in addition to the dysfunctional Pittsburgh and Iners variants reported previously, several uncharacterized RCL variants are present in genome variation databases. To prospectively evaluate the impact of RCL variations on secretion and anti-protease activity, here we performed a systematic screening of amino acid substitutions occurring at the AAT-NE interface. Twenty-three AAT variants that can result from single nucleotide polymorphisms in this region, including 11 present in sequence variation databases, were expressed in a mammalian cell model. All demonstrated unaltered protein folding and secretion. However, when their ability to form stable complexes with NE was evaluated by western blot, enzymatic assays, and a novel ELISA developed to quantify AAT-NE complexes, substrate-like and NE-binding deficient dysfunctional variants were identified. This emphasizes the ability of the RCL to accommodate inactivating substitutions without impacting the integrity of the native molecule and demonstrates that this class of molecule violates a generally accepted paradigm that equates circulating levels with functional protection of lung tissue.

Molecular dynamics, molecular docking, DFT, and ADMET investigations of the Co(II), Cu(II), and Zn(II) chelating on the antioxidant activity and SARS-CoV-2 main protease inhibition of quercetin

The natural flavonol quercetin (Q) is found in many vegetables, fruits, and beverages, and it is known as a strong antioxidant. Its metal ion chelation may increase its antioxidant activity. The present study aims to explore the Co(II), Cu(II), and Zn(II) chelating on the antioxidant effectiveness and severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) main protease (Mpro) inhibitory of quercetin using Density-functional theory (DFT), molecular docking, and molecular dynamics simulations (MD). DFT calculations at the B3LYP/LanL2DZ reveal that the high antioxidant activity of the metal-chelated quercetin complexes is mainly returned to their lower ionization potentials (IPs) compared with the one of the free quercetin. Molecular docking of quercetin and its Co(II), Cu(II), and Zn(II) chelates into the active binding sites of peroxiredoxin 5 and SARS-CoV-2 main protease (Mpro) were performed using Lamarckian Genetic Algorithm method. The docked quercetin and its metal chelates fit well into the binding site of the target proteins, and their binding affinity is strongly influenced by the type of the chelated metals Co(II), Cu(II), and Zn(II), and molar ratio metal: ligand, i.e. 1:2 and 2:1. Further, the binding stability of QZn2 and QCu2 in peroxiredoxin 5 and SARS-CoV-2 main protease targets is evaluated using MD simulation conducted for 100 ns simulations at natural room temperature conditions, and the obtained results showed that all chelates remain bound to the ligand binding groove of protein except for 1HD2_QZn2 complex. Finally, the adsorption, distribution, metabolism, excretion, and toxicity (ADMET) and drug-likeness properties of quercetin and cobalt(II)-quercetin (QCo2(II)) were investigated. Communicated by Ramaswamy H. Sarma

Collagen Anchoring Protein-Nucleic Acid Chimeric Probe for In Situ In Vivo Mapping of a Tumor-Specific Protease.

In situ analysis of biomarkers in the tumor microenvironment (TME) is important to reveal their potential roles in tumor progression and early diagnosis of tumors but remains a challenge. In this work, a bottom-up modular assembly strategy was proposed for a multifunctional protein-nucleic chimeric probe (PNCP) for in situ mapping of cancer-specific proteases. PNCP, containing a collagen anchoring module and a target proteolysis-responsive isothermal amplification sensor module, can be anchored in the collagen-rich TME and respond to the target protease in situ and generate amplified signals through rolling cycle amplification of tandem fluorescent RNAs. Taking matrix metalloproteinase 2 (MMP-2), a tumor-associated protease, as the model, the feasibility of PNCP was demonstrated for the in situ detection of MMP-2 activity in 3D tumor spheroids. Moreover, in situ in vivo mapping of MMP-2 activity was also achieved in a metastatic solid tumor model with high sensitivity, providing a useful tool for evaluating tumor metastasis and distinguishing highly aggressive forms of tumors.