3D Modeling of Tumor Necrosis Factor Receptor and Tumor Necrosis Factor-bound Receptor Systems

Computational Investigation of Selected Spike Protein Mutations in SARS-CoV-2: Delta, Omicron, and Some Circulating Subvariants

Among the multiple SARS-CoV-2 variants recently reported, the Delta variant has generated the most perilous and widespread effects. Another variant, Omicron, has been identified specifically for its high transmissibility. Omicron contains numerous spike (S) protein mutations and numbers much larger than those of its predecessor variants. In this report, the author has discussed some essential structural aspects and time-based structure changes of a selected set of spike protein mutations within the Delta and Omicron variants. The expected impact of multiple point mutations within the spike protein's receptor-binding domain (RBD) and S1 of these variants are examined. Additionally, the RBDs of the more recently emerged subvariants BA.4, BA.5, and BA.2.12.1 are discussed. Within the latter group, BA.5 represents the most prevalent form of SARS-CoV-2 globally until recently. This computational work also briefly explores the temporal mutation profile for the currently circulating variants of interest (VOIs), variants under monitoring (VUMs), and variants being monitored (VBMs) including XBB.1.5, BQ.1, BA.2.75, CH.1.1, XBB, XBF, EG.5 (or Eris), and BA.2.86 (or Pirola). It is expected that these structural data can facilitate the tasks of identifying drug targets and neutralizing antibodies for the evolving variants/subvariants of SARS-CoV-2.

How does the same ligand activate signaling of different receptors in TNFR superfamily: a computational study

TNFα is a highly pleiotropic cytokine inducing inflammatory signaling pathways. It is initially presented on plasma membrane of cells (mTNFα), and also exists in a soluble variant (sTNFα) after cleavage. The ligand is shared by two structurally similar receptors, TNFR1 and TNFR2. Interestingly, while sTNFα preferentially stimulates TNFR1, TNFR2 signaling can only be activated by mTNFα. How can two similar receptors respond to the same ligand in such a different way? We employed computational simulations in multiple scales to address this question. We found that both mTNFα and sTNFα can trigger the clustering of TNFR1. The size of clusters induced by sTNFα is constantly larger than the clusters induced by mTNFα. The systems of TNFR2, on the other hand, show very different behaviors. Only when the interactions between TNFR2 are very weak, mTNFα can trigger the receptors to form very large clusters. Given the same weak binding affinity, only small oligomers were obtained in the system of sTNFα. Considering that TNF-mediated signaling is modulated by the ligand-induced clustering of receptors on cell surface, our study provided the mechanistic foundation to the phenomenon that different isoforms of the ligand can lead to highly distinctive signaling patterns for its receptors.

Implications of SARS-CoV-2 spike protein interactions with Zn-bound form of ACE2: a computational structural study

The COVID-19 pandemic has generated a major interest in designing inhibitors to prevent SARS-CoV-2 binding on host cells to protect against infection. One promising approach to such research utilizes molecular dynamics simulation to identify potential inhibitors that can prevent the interaction between spike (S) protein on the virus and angiotensin converting enzyme 2 (ACE2) receptor on the host cells. In these studies, many groups have chosen to exclude the ACE2-bound zinc (Zn) ion, which is critical for its enzymatic activity. While the relatively distant location of Zn ion from the S protein binding site (S1 domain), combined with the difficulties in modeling this ion has motivated the decision of exclusion, Zn can potentially contribute to the structural stability of the entire protein, and thus, may have implications on S protein-ACE2 interaction. In this study, the authors model both the ACE2-S1 and ACE2-inhibitor (mAb) system to investigate if there are variations in structure and the readouts due to the presence of Zn ion. Although distant from the S1 or inhibitor binding region, inclusion/exclusion of Zn has statistically significant effects on the structural stability and binding free energy in these systems. In particular, the binding free energy of the ACE2-S1 and ACE2-inhibitor structures is - 3.26 and - 14.8 kcal/mol stronger, respectively, in the Zn-bound structure than in the Zn-free structures. This finding suggests that including Zn may be important in screening potentially inhibitors and may be particularly important in modeling monoclonal antibodies, which may be more sensitive to changes in antigen structure.

Marine-derived microbes and molecules for drug discovery

Increasing attention has been paid to marine-derived biomolecules as sources of therapeutics for autoimmune diseases. Nagasaki Prefecture has many islands and is surrounded by seas, straits, gulfs, bays, and coves, giving it the second longest coastline in Japan after Hokkaido. We have collected more than 20,000 marine microbes and have been preparing an original marine microbial extract library, which contains small and mid-size biomolecules that may penetrate cell membranes and interfere with the intracellular protein–protein interaction involved in the development of autoinflammatory diseases such as familial Mediterranean fever. In addition, we have been developing an indoor shark farming system to prepare shark nanobodies that could be developed as potential therapeutic agents for autoimmune diseases. Sharks produce heavy-chain antibodies, called immunoglobulin new antigen receptors (IgNARs), consisting of one variable domain (V_NAR) and five constant domains (C_NAR); of these, V_NAR can recognize a variety of foreign antigens. A V_NAR single domain fragment, called a nanobody, can be expressed in Escherichia coli and has the properties of an ideal therapeutic candidate for autoimmune diseases. Shark nanobodies contain complementarity-determining regions that are formed through the somatic rearrangement of variable, diversity, and joining segments, with the segment end trimming and the N- and P-additions, as found in the variable domains of mammalian antibodies. The affinity and diversity of shark nanobodies are thus expected to be comparable to those of mammalian antibodies. In addition, shark nanobodies are physically robust and can be prepared inexpensively; as such, they may lead to the development of highly specific, stable, effective, and inexpensive biotherapeutics in the future. In this review, we first summarize the history of the development of conventional small molecule drugs and monoclonal antibody therapeutics for autoimmune diseases, and then introduce our drug discovery system at Nagasaki University, including the preparation of an original marine microbial extract library and the development of shark nanobodies.

Comparative structural analyses of selected spike protein-RBD mutations in SARS-CoV-2 lineages

The severity of COVID-19 has been observed throughout the world as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) globally claimed more than 2 million lives and left a devastating impact worldwide. Recently several virulent mutant strains of this virus, such as the B.1.1.7, B.1.351, and P1 lineages, have emerged with initial predominance in UK, South Africa, and Brazil. Another extremely pathogenic B.1.617 lineage and its sub-lineages, first detected in India, are now affecting some countries at notably stronger spread-rates. The present paper computationally examines the time-based structures of B.1.1.7, B.1.351, and P1 lineages with selected spike protein mutations. The mutations in the more recently found B.1.617 lineage and its sub-lineages are explored, and the implications for multiple point mutations of the spike protein's receptor-binding domain (RBD) are described. The selected S1 mutations within the highly contagious B.1.617.2 sub-lineage, also known as the delta variant, are examined as well.

Structural and molecular analyses of functional epitopes and escape mutants in Japanese encephalitis virus envelope protein domain III

The Japanese encephalitis virus (JEV) is one of the vector borne causes of encephalitis found in southeastern Asia. This positive single-stranded RNA virus is a member of the Flaviviridae family, which notably includes dengue, tick-borne, West Nile, Zika as well as yellow fever, and transmits to humans by infected mosquitos. The main site of interactions for antibodies against this virus is the envelope protein domain III (ED3). The present report investigates the time-dependent structural and conformational changes of JEV ED3 functional epitopes and escape mutants by computer simulations. The results indicate the presence of significant structural differences between the functional epitopes and the escape mutants. Mutation-induced structural/conformational instabilities of this type can decrease the antibody neutralization activity. Among the different escape mutants studied here, Ser40Lys/Asp41Arg appear to be most unstable, while Ser40Glu/Asp41Leu exhibit the lowest structural variations. The highest level of escape mutation observed in Ser40Lys is linked to the relatively higher values of root mean square deviation/fluctuation found in the molecular dynamics simulation of this protein. Secondary-structure deviations and depletion of H bonding are other contributing factors to the protein’s increased instability. Overall, the proteins with residue 41 mutations are found to be structurally more ordered than those with residue 40 mutations. The detailed time-based structural assessment of the mutant epitopes described here may contribute to the development of novel vaccines and antiviral drugs necessary to defend against future outbreaks of JEV escape mutants.

Design, Synthesis, and In Silico Multitarget Pharmacological Simulations of Acid Bioisosteres with a Validated In Vivo Antihyperglycemic Effect

Substituted phenylacetic (1-3), phenylpropanoic (4-6), and benzylidenethiazolidine-2,4-dione (7-9) derivatives were designed according to a multitarget unified pharmacophore pattern that has shown robust antidiabetic activity. This bioactivity is due to the simultaneous polypharmacological stimulation of receptors PPARα, PPARγ, and GPR40 and the enzyme inhibition of aldose reductase (AR) and protein tyrosine phosphatase 1B (PTP-1B). The nine compounds share the same four pharmacophore elements: an acid moiety, an aromatic ring, a bulky hydrophobic group, and a flexible linker between the latter two elements. Addition and substitution reactions were performed to obtain molecules at moderated yields. In silico pharmacological consensus analysis (PHACA) was conducted to determine their possible modes of action, protein affinities, toxicological activities, and drug-like properties. The results were combined with in vivo assays to evaluate the ability of these compounds to decrease glucose levels in diabetic mice at a 100 mg/kg single dose. Compounds 6 (a phenylpropanoic acid derivative) and 9 (a benzylidenethiazolidine-2,4-dione derivative) ameliorated the hyperglycemic peak in a statically significant manner in a mouse model of type 2 diabetes. Finally, molecular dynamics simulations were executed on the top performing compounds to shed light on their mechanism of action. The simulations showed the flexible nature of the binding pocket of AR, and showed that both compounds remained bound during the simulation time, although not sharing the same binding mode. In conclusion, we designed nine acid bioisosteres with robust in vivo antihyperglycemic activity that were predicted to have favorable pharmacokinetic and toxicological profiles. Together, these findings provide evidence that supports the molecular design we employed, where the unified pharmacophores possess a strong antidiabetic action due to their multitarget activation.

A Rational Insight into the Effect of Dimethyl Sulfoxide on TNF-α Activity

Direct inhibition of tumor necrosis factor-alpha (TNF-α) action is considered a promising way to prevent or treat TNF-α-associated diseases. The trimeric form of TNF-α binds to its receptor (TNFR) and activates the downstream signaling pathway. The interaction of TNF-α with molecular-grade dimethyl sulfoxide (DMSO) in an equal volumetric ratio renders TNF-α inert, in this state, TNF-α fails to activate TNFR. Here, we aimed to examine the inhibition of TNF-α function by various concentrations of DMSO. Its higher concentration led to stronger attenuation of TNF-α-induced cytokine secretion by fibroblasts, and of their death. We found that this inhibition was mediated by a perturbation in the formation of the functional TNF-α trimer. Molecular dynamics simulations revealed a transient interaction between DMSO molecules and the central hydrophobic cavity of the TNF-α homodimer, indicating that a brief interaction of DMSO with the TNF-α homodimer may disrupt the formation of the functional homotrimer. We also found that the sensitizing effect of actinomycin D on TNF-α-induced cell death depends upon the timing of these treatments and on the cell type. This study will help to select an appropriate concentration of DMSO as a working solvent for the screening of water-insoluble TNF-α inhibitors.

Insight into the structures of Interleukin-18 systems

Structure-based molecular designs play a critical role in the context of next generation drug development. Besides their fundamental scientific aspects, the findings established in this approach have significant implications in the expansions of target-based therapies and vaccines. Interleukin-18 (IL-18), also known as interferon gamma (IFN-γ) inducing factor, is a pro-inflammatory cytokine. The IL-18 binds first to the IL-18α receptor and forms a lower affinity complex. Upon binding with IL-18β a hetero-trimeric complex with higher affinity is formed that initiates the signal transduction process. The present study, including structural and molecular dynamics simulations, takes a close look at the structural stabilities of IL-18 and IL-18 receptor-bound ligand structures as functions of time. The results help to identify the conformational changes of the ligand due to receptor binding, as well as the structural orders of the apo and holo IL-18 protein complexes.

Fetal Growth Trajectories and Their Association with Maternal, Cord Blood, and 5-year Child Adipokines

Background

The growth of the fetus is a complex process influenced by multiple factors. Studies have highlighted the important role of biochemical growth markers such as leptin and adiponectin on fetal growth.

Objective

To compare fetal growth trajectories with biochemical growth markers from maternal blood samples at 28 weeks' gestation, cord blood samples at birth, and in child blood samples at 5 years of age from mother-infant pairs who were part of the longitudinal ROLO study.

Methods

781 mother-infant pairs from the ROLO and ROLO Kids study were included. Ultrasound measurements and birth weight were used to develop fetal growth trajectory groups for estimated abdominal circumference and estimated weight. Blood serum levels of leptin, adiponectin, insulin, TNF-alpha, and IL-6 from maternal, cord, and 5-year child samples were recorded. ANOVA and chi-square tests were applied to test the associations between fetal growth trajectory membership and maternal and child biochemical growth indicators. The influence of child sex was also investigated.

Results

Male sex was associated with a faster weight trajectory compared to females (p=0.001). At 28 weeks' gestation, maternal leptin levels were significantly higher in mothers with a fetus on a slower estimated abdominal circumference trajectory compared to fast (25616 [IQR: 11656.0 to 35341.0] vs. 14753.8 [IQR: 8565.4 to 24308.1], p < 0.001) and maternal adiponectin levels were lower in fetuses on a slower estimated abdominal circumference trajectory compared to a fast trajectory (22.4 [IQR: 13.6 to 35.9] vs. 27.6 [IQR: 17.6 to 46.3], p=0.027). No associations were noted with inflammatory markers. No associations were identified between fetal growth trajectories and growth markers at 5 years of age.

Conclusions

This study shows that male sex is associated with an accelerated estimated weight trajectory. Furthermore, high leptin and low adiponectin in maternal serum in late gestation are associated with a slower fetal growth trajectory. No associations were identified with blood growth markers after pregnancy.

Structure and Function of an Inflammatory Cytokine, Interleukin-2, Analyzed Using the Bioinformatic Approach

The inflammatory cytokine, interleukin-2 (IL-2), is an important regulator of cellular functions. This relatively less studied member of the interleukin protein family is responsible for multiple immuno-modulatory and immuno-stimulatory tasks, like T cell activation, triggering of natural killer cells, inflammation, as well as proliferation and progression of autoimmune diseases and cancers. In this communication we report the temporally variant structural aspects of the IL-2 ligand and its receptor interfaces, based on the available crystal structures. The intended goal of this effort is to generate simulated results that could potentially aid the designs of novel structure based therapeutics.