Quinic Acid Alleviates Behavior Impairment by Reducing Neuroinflammation and MAPK Activation in LPS-Treated Mice.

Compared to other organs, the brain has limited antioxidant defenses. In particular, the hippocampus is the central region for learning and memory and is highly susceptible to oxidative stress. Glial cells are the most abundant cells in the brain, and sustained glial cell activation is critical to the neuroinflammation that aggravates neuropathology and neurotoxicity. Therefore, regulating glial cell activation is a promising neurotherapeutic treatment. Quinic acid and its derivatives possess anti-oxidant and anti-inflammatory properties. Although previous studies have evidenced quinic acid's benefit on the brain, in vivo and in vitro analyses of its anti-oxidant and anti-inflammatory properties in glial cells have yet to be established. This study investigated quinic acid's rescue effect in lipopolysaccharide (LPS)-induced behavior impairment. Orally administering quinic acid restored social impairment and LPS-induced spatial and fear memory. In addition, quinic acid inhibited proinflammatory mediator, oxidative stress marker, and mitogen-activated protein kinase (MAPK) activation in the LPS-injected hippocampus. Quinic acid inhibited nitrite release and extracellular signal-regulated kinase (ERK) phosphorylation in LPS-stimulated astrocytes. Collectively, quinic acid restored impaired neuroinflammation-induced behavior by regulating proinflammatory mediator and ERK activation in astrocytes, demonstrating its potential as a therapeutic agent for neuroinflammation-induced brain disease treatments.

Structure-Based Insight on the Mechanism of N-Glycosylation Inhibition by Tunicamycin.

N-glycosylation, a common post-translational modification, is widely acknowledged to have a significant effect on protein stability and folding. N-glycosylation is a complex process that occurs in the endoplasmic reticulum (ER) and requires the participation of multiple enzymes. GlcNAc-1-P-transferase (GPT) is essential for initiating N-glycosylation in the ER. Tunicamycin is a natural product that inhibits N-glycosylation and produces ER stress, and thus it is utilized in research. The molecular mechanism by which GPT triggers N-glycosylation is discussed in this review based on the GPT structure. Based on the structure of the GPT-tunicamycin complex, we also discuss how tunicamycin reduces GPT activity, which prevents N-glycosylation. This review will be highly useful for understanding the role of GPT in the N-glycosylation of proteins, as well as presents a potential for considering tunicamycin as an antibiotic treatment.

Industrializing AI/ML during the end-to-end drug discovery process.

Drug discovery aims to select proper targets and drug candidates to address unmet clinical needs. The end-to-end drug discovery process includes all stages of drug discovery from target identification to drug candidate selection. Recently, several artificial intelligence and machine learning (AI/ML)-based drug discovery companies have attempted to build data-driven platforms spanning the end-to-end drug discovery process. The ability to identify elusive targets essentially leads to the diversification of discovery pipelines, thereby increasing the ability to address unmet needs. Modern ML technologies are complementing traditional computer-aided drug discovery by accelerating candidate optimization in innovative ways. This review summarizes recent developments in AI/ML methods from target identification to molecule optimization, and concludes with an overview of current industrial trends in end-to-end AI/ML platforms.

Systematic analyses of the sequence conservation and ligand interaction patterns of purinergic P1 and P2Y receptors provide a structural basis for receptor selectivity.

Purinergic receptors are membrane proteins that regulate numerous cellular functions by catalyzing reactions involving purine nucleotides or nucleosides. Among the three receptor families, i.e., P1, P2X, and P2Y, the P1 and P2Y receptors share common structural features of class A GPCR. Comprehensive sequence and structural analysis revealed that the P1 and P2Y receptors belong to two distinct groups. They exhibit different ligand-binding site features that can distinguish between specific activators. These specific amino acid residues in the binding cavity may be involved in the selectivity and unique pharmacological behavior of each subtype. In this study, we conducted a structure-based analysis of purinergic P1 and P2Y receptors to identify their evolutionary signature and obtain structural insights into ligand recognition and selectivity. The structural features of the P1 and P2Y receptor classes were compared based on sequence conservation and ligand interaction patterns. Orthologous protein sequences were collected for the P1 and P2Y receptors, and sequence conservation was calculated based on Shannon entropy to identify highly conserved residues. To analyze the ligand interaction patterns, we performed docking studies on the P1 and P2Y receptors using known ligand information extracted from the ChEMBL database. We analyzed how the conserved residues are related to ligand-binding sites and how the key interacting residues differ between P1 and P2Y receptors, or between agonists and antagonists. We extracted new similarities and differences between the receptor subtypes, and the results can be used for designing new ligands by predicting hotspot residues that are important for functional selectivity.

Structural basis of Ca2+ uptake by mitochondrial calcium uniporter in mitochondria: a brief review.

Mitochondria are cellular organelles that perform various functions within cells. They are responsible for ATP production, cell-signal regulation, autophagy, and cell apoptosis. Because the mitochondrial proteins that perform these functions need Ca2+ ions for their activity, mitochondria have ion channels to selectively uptake Ca2+ ions from the cytoplasm. The ion channel known to play the most important role in the Ca2+ uptake in mitochondria is the mitochondrial calcium uniporter (MCU) holo-complex located in the inner mitochondrial membrane (IMM). This ion channel complex exists in the form of a complex consisting of the pore-forming protein through which the Ca2+ ions are transported into the mitochondrial matrix, and the auxiliary protein involved in regulating the activity of the Ca2+ uptake by the MCU holo-complex. Studies of this MCU holocomplex have long been conducted, but we didn't know in detail how mitochondria uptake Ca2+ ions through this ion channel complex or how the activity of this ion channel complex is regulated. Recently, the protein structure of the MCU holo-complex was identified, enabling the mechanism of Ca2+ uptake and its regulation by the MCU holo-complex to be confirmed. In this review, I will introduce the mechanism of action of the MCU holo-complex at the molecular level based on the Cryo-EM structure of the MCU holo-complex to help understand how mitochondria uptake the necessary Ca2+ ions through the MCU holo-complex and how these Ca2+ uptake mechanisms are regulated. [BMB Reports 2022; 55(11): 528-534].

Methotrexate recognition by the human reduced folate carrier SLC19A1.

Folates are essential nutrients with important roles as cofactors in one-carbon transfer reactions, being heavily utilized in the synthesis of nucleic acids and the metabolism of amino acids during cell division1,2. Mammals lack de novo folate synthesis pathways and thus rely on folate uptake from the extracellular milieu3. The human reduced folate carrier (hRFC, also known as SLC19A1) is the major importer of folates into the cell1,3, as well as chemotherapeutic agents such as methotrexate4-6. As an anion exchanger, RFC couples the import of folates and antifolates to anion export across the cell membrane and it is a major determinant in methotrexate (antifolate) sensitivity, as genetic variants and its depletion result in drug resistance4-8. Despite its importance, the molecular basis of substrate specificity by hRFC remains unclear. Here we present cryo-electron microscopy structures of hRFC in the apo state and captured in complex with methotrexate. Combined with molecular dynamics simulations and functional experiments, our study uncovers key determinants of hRFC transport selectivity among folates and antifolate drugs while shedding light on important features of anion recognition by hRFC.

Parasphingorhabdus cellanae sp. nov., isolated from the gut of a Korean limpet, Cellana toreuma.

A novel bacterium, designated strain JHSY0214T, was isolated from the gut of a Korean limpet, Cellana toreuma. Cells of strain JHSY0214T were Gram-stain-negative, strictly aerobic, yellow-pigmented, non-spore-forming, non-motile and showed a rod-coccus growth cycle. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain belonged to the genus Parasphingorhabdus, and was most closely related to Parasphingorhabdus litoris KCTC 12764T (98.71 %). Strain JHSY0214T had two fluoroquinolone-resistance genes and seven multidrug-resistance efflux pump genes, but did not have beta-lactamase genes and zinc resistance genes compared with P. litoris KCTC 12764T. Strain JHSY0214T grew optimally at 30 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. The predominant cellular fatty acids of strain JHSY0214T were summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c; 41.2 %), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c; 21 %) and C16 : 0 (18.9 %). The major isoprenoid quinone was ubiquinone-10. The major polar lipids were sphingoglycolipid and phosphatidylethanolamine. The genomic DNA G+C content was 52.8 mol%. Based on phylogenetic, genotypic and phenotypic data, strain JHSY0214T represents a novel species of the genus Parasphingorhabdus, for which the name Parasphingorhabdus cellanae is proposed. The type strain is JHSY0214T (=KCTC 82387T=DSM 112279T).

Arginine-mediated gut microbiome remodeling promotes host pulmonary immune defense against nontuberculous mycobacterial infection.

Nontuberculous mycobacterial pulmonary diseases (NTM-PDs) are emerging as global health threats with issues of antibiotic resistance. Accumulating evidence suggests that the gut-lung axis may provide novel candidates for host-directed therapeutics against various infectious diseases. However, little is known about the gut-lung axis in the context of host protective immunity to identify new therapeutics for NTM-PDs. This study was performed to identify gut microbes and metabolites capable of conferring pulmonary immunity to NTM-PDs. Using metabolomics analysis of sera from NTM-PD patients and mouse models, we showed that the levels of l-arginine were decreased in sera from NTM-PD patients and NTM-infected mice. Oral administration of l-arginine significantly enhanced pulmonary antimicrobial activities with the expansion of IFN-γ-producing effector T cells and a shift to microbicidal (M1) macrophages in the lungs of NTM-PD model mice. Mice that received fecal microbiota transplants from l-arginine-treated mice showed increased protective host defense in the lungs against NTM-PD, whereas l-arginine-induced pulmonary host defense was attenuated in mice treated with antibiotics. Using 16S rRNA sequencing, we further showed that l-arginine administration resulted in enrichment of the gut microbiota composition with Bifidobacterium species. Notably, oral treatment with either Bifidobacterium pseudolongum or inosine enhanced antimicrobial pulmonary immune defense against NTM infection, even with multidrug-resistant clinical NTM strains. Our findings indicate that l-arginine-induced gut microbiota remodeling with enrichment of B. pseudolongum boosts pulmonary immune defense against NTM infection by driving the protective gut-lung axis in vivo.

Description of Polaribacter batillariae sp. nov., Polaribacter cellanae sp. nov., and Polaribacter pectinis sp. nov., novel bacteria isolated from the gut of three types of South Korean shellfish.

Three aerobic, Gram-negative, and rod-shaped bacterial strains, designated strains G4M1T, SM13T, and L12M9T, were isolated from the gut of Batillaria multiformis, Cellana toreuma, and Patinopecten yessoensis collected from the Yellow Sea in South Korea. All the strains grew optimally at 25°C, in the presence of 2% (w/v) NaCl, and at pH 7. These three strains, which belonged to the genus Polaribacter in the family Flavobacteriaceae, shared < 98.8% in 16S rRNA gene sequence and < 86.68% in whole-genome sequence with each other. Compared with the type strains of Polaribacter, isolates showed the highest sequence similarity to P. haliotis KCTC 52418T (< 98.68%), followed by P. litorisediminis KCTC 52500T (< 98.13%). All the strains contained MK-6 as their predominant menaquinone and iso-C15:0 as their major fatty acid. Moreover, all the strains had phosphatidylethanolamine as their polar lipid component. In addition, strain G4M1T had two unidentified lipids and three unidentified aminolipids, strain SM13T had three unidentified lipids and three unidentified aminolipids, and strain L12M9T had three unidentified lipids and one unidentified aminolipid. The DNA G + C contents of strains G4M1T, SM13T, and L12M9T were 31.0, 30.4, and 29.7 mol%, respectively. Based on phenotypic, phylogenetic, chemotaxonomic, and genotypic findings, strains G4M1T (= KCTC 82388T = DSM 112372T), SM13T (= KCTC 82389T = DSM 112373T), and L12M9T (= KCTC 62751T = DSM 112374T) were classified into the genus Polaribacter as the type strains of novel species, for which the names Polaribacter batillariae sp. nov., Polaribacter cellanae sp. nov., and Polaribacter pectinis sp. nov., respectively, have been proposed.

Efficient learning of non-autoregressive graph variational autoencoders for molecular graph generation.

With the advancements in deep learning, deep generative models combined with graph neural networks have been successfully employed for data-driven molecular graph generation. Early methods based on the non-autoregressive approach have been effective in generating molecular graphs quickly and efficiently but have suffered from low performance. In this paper, we present an improved learning method involving a graph variational autoencoder for efficient molecular graph generation in a non-autoregressive manner. We introduce three additional learning objectives and incorporate them into the training of the model: approximate graph matching, reinforcement learning, and auxiliary property prediction. We demonstrate the effectiveness of the proposed method by evaluating it for molecular graph generation tasks using QM9 and ZINC datasets. The model generates molecular graphs with high chemical validity and diversity compared with existing non-autoregressive methods. It can also conditionally generate molecular graphs satisfying various target conditions.

Cryo-EM structure of a mitochondrial calcium uniporter.

Calcium transport plays an important role in regulating mitochondrial physiology and pathophysiology. The mitochondrial calcium uniporter (MCU) is a calcium-selective ion channel that is the primary mediator for calcium uptake into the mitochondrial matrix. Here, we present the cryo-electron microscopy structure of the full-length MCU from Neurospora crassa to an overall resolution of ~3.7 angstroms. Our structure reveals a tetrameric architecture, with the soluble and transmembrane domains adopting different symmetric arrangements within the channel. The conserved W-D-Φ-Φ-E-P-V-T-Y sequence motif of MCU pore forms a selectivity filter comprising two acidic rings separated by one helical turn along the central axis of the channel pore. The structure combined with mutagenesis gives insight into the basis of calcium recognition.

GlcNAc-1-P-transferase-tunicamycin complex structure reveals basis for inhibition of N-glycosylation.

N-linked glycosylation is a predominant post-translational modification of protein in eukaryotes, and its dysregulation is the etiology of several human disorders. The enzyme UDP-N-acetylglucosamine:dolichyl-phosphate N-acetylglucosaminephosphotransferase (GlcNAc-1-P-transferase or GPT) catalyzes the first and committed step of N-linked glycosylation in the endoplasmic reticulum membrane, and it is the target of the natural product tunicamycin. Tunicamycin has potent antibacterial activity, inhibiting the bacterial cell wall synthesis enzyme MraY, but its usefulness as an antibiotic is limited by off-target inhibition of human GPT. Our understanding of how tunicamycin inhibits N-linked glycosylation and efforts to selectively target MraY are hampered by a lack of structural information. Here we present crystal structures of human GPT in complex with tunicamycin. Structural and functional analyses reveal the difference between GPT and MraY in their mechanisms of inhibition by tunicamycin. We demonstrate that this difference could be exploited to design MraY-specific inhibitors as potential antibiotics.

Differential Inhibition of Nav1.7 and Neuropathic Pain by Hybridoma-Produced and Recombinant Monoclonal Antibodies that Target Nav1.7 : Differential activities of Nav1.7-targeting monoclonal antibodies.

The voltage-gated Na+ channel subtype Nav1.7 is important for pain and itch in rodents and humans. We previously showed that a Nav1.7-targeting monoclonal antibody (SVmab) reduces Na+ currents and pain and itch responses in mice. Here, we investigated whether recombinant SVmab (rSVmab) binds to and blocks Nav1.7 similar to SVmab. ELISA tests revealed that SVmab was capable of binding to Nav1.7-expressing HEK293 cells, mouse DRG neurons, human nerve tissue, and the voltage-sensor domain II of Nav1.7. In contrast, rSVmab showed no or weak binding to Nav1.7 in these tests. Patch-clamp recordings showed that SVmab, but not rSVmab, markedly inhibited Na+ currents in Nav1.7-expressing HEK293 cells. Notably, electrical field stimulation increased the blocking activity of SVmab and rSVmab in Nav1.7-expressing HEK293 cells. SVmab was more effective than rSVmab in inhibiting paclitaxel-induced mechanical allodynia. SVmab also bound to human DRG neurons and inhibited their Na+ currents. Finally, potential reasons for the differential efficacy of SVmab and rSVmab and future directions are discussed.

New structural insight of C-terminal region of Syntenin-1, enhancing the molecular dimerization and inhibitory function related on Syndecan-4 signaling.

The PDZ domain-containing scaffold protein, syntenin-1, binds to the transmembrane proteoglycan, syndecan-4, but the molecular mechanism/function of this interaction are unknown. Crystal structure analysis of syntenin-1/syndecan-4 cytoplasmic domains revealed that syntenin-1 forms a symmetrical pair of dimers anchored by a syndecan-4 dimer. The syndecan-4 cytoplasmic domain is a compact intertwined dimer with a symmetrical clamp shape and two antiparallel strands forming a cavity within the dimeric twist. The PDZ2 domain of syntenin-1 forms a direct antiparallel interaction with the syndecan-4 cytoplasmic domain, inhibiting the functions of syndecan-4 such as focal adhesion formation. Moreover, C-terminal region of syntenin-1 reveals an essential role for enhancing the molecular homodimerization. Mutation of key syntenin-1 residues involved in the syndecan-4 interaction or homodimer formation abolishes the inhibitory function of syntenin-1, as does deletion of the homodimerization-related syntenin-1 C-terminal domain. Syntenin-1, but not dimer-formation-incompetent mutants, rescued the syndecan-4-mediated inhibition of migration and pulmonary metastasis by B16F10 cells. Therefore, we conclude that syntenin-1 negatively regulates syndecan-4 function via oligomerization and/or syndecan-4 interaction, impacting cytoskeletal organization and cell migration.

GC1118, an Anti-EGFR Antibody with a Distinct Binding Epitope and Superior Inhibitory Activity against High-Affinity EGFR Ligands.

The EGFR-targeted monoclonal antibodies are a valid therapeutic strategy for patients with metastatic colorectal cancer (mCRC). However, only a small subset of mCRC patients has therapeutic benefits and there are high demands for EGFR therapeutics with a broader patient pool and more potent efficacy. In this study, we report GC1118 exhibiting a different character in terms of binding epitope, affinity, mode of action, and efficacy from other anti-EGFR antibodies. Structural analysis of the EGFR-GC1118 crystal complex revealed that GC1118 recognizes linear, discrete N-terminal epitopes of domain III of EGFR, critical for EGF binding but not overlapping with those of other EGFR-targeted antibodies. GC1118 exhibited superior inhibitory activity against high-affinity EGFR ligands in terms of EGFR binding, triggering EGFR signaling, and proliferation compared with cetuximab and panitumumab. EGFR signaling driven by low-affinity ligands, on the contrary, was well inhibited by all the antibodies tested. GC1118 demonstrated robust antitumor activity in tumor xenografts with elevated expression of high-affinity ligands in vivo, whereas cetuximab did not. Considering the significant role of high-affinity EGFR ligands in modulating tumor microenvironment and inducing resistance to various cancer therapeutics, our study suggests a potential therapeutic advantage of GC1118 in terms of efficacy and a range of benefited patient pool. Mol Cancer Ther; 15(2); 251-63. ©2015 AACR.

Studies of Grafted and Sulfonated Spiro Poly(isatin-ethersulfone) Membranes by Super Acid-Catalyzed Reaction.

Spiro poly(isatin-ethersulfone) polymers were prepared from isatin and bis-2,6-dimethylphenoxyphenylsulfone by super acid catalyzed polyhydroxyalkylation reactions. We designed and synthesized bis-2,6-dimethylphenoxyphenylsulfone, which is structured at the meta position steric hindrance by two methyl groups, because this structure minimized crosslinking reaction during super acid catalyzed polymerization. In addition, sulfonic acid groups were structured in both side chains and main chains to form better polymer chain morphology and improve proton conductivity. The sulfonation reactions were performed in two steps which are: in 3-bromo-1-propanesulfonic acid potassium salt and in con. sulfuric acid. The membrane morphology was studied by tapping mode atomic force microscope (AFM). The phase difference between the hydrophobic polymer main chain and hydrophilic sulfonated units of the polymer was shown to be the reasonable result of the well phase separated structure. The correlations of proton conductivity, ion exchange capacity (IEC) and single cell performance were clearly described with the membrane morphology.

Crystal structure of syndesmos and its interaction with Syndecan-4 proteoglycan.

Syndesmos, nucleoside diphosphate linked moiety X (nudix)-type motif 16-like 1 (Nudt16l1), is evolutionarily divergent from the Nudt16 family. Syndesmos, which is co-localized with syndecan-4 cytoplasmic domain (Syn4(cyto)) in focal contacts, interacts with various cell adhesion adaptor proteins to control cell signaling. We determined the X-ray crystal structure of syndesmos; it is composed of seven α-helices and seven ß-strands. Although syndesmos has a molecular topology similar to that of nudix hydrolase proteins, the structure of the nudix motif differs from that of X29. The dimeric interface of syndesmos is composed of α-helix 4, 7 and ß-strand 2, 7, which primarily form hydrophobic interactions. The binding interaction between syndesmos and syn4(cyto) was characterized as a low-affinity interaction (Kd = 62 µM) by surface plasmon resonance (SPR) and nuclear magnetic resonance (NMR). The NMR resonances of Lys (177, 178, 179), Gly182, and Ser183 in the C1 region and Lys193 and Lys194 in the V region of syndecan-4 are perturbed upon syndesmos binding. Our results provide structural insight into the molecular function of syndesmos in the regulation of cell signaling via binding to syndecan-4.

Computational design of binding proteins to EGFR domain II.

We developed a process to produce novel interactions between two previously unrelated proteins. This process selects protein scaffolds and designs protein interfaces that bind to a surface patch of interest on a target protein. Scaffolds with shapes complementary to the target surface patch were screened using an exhaustive computational search of the human proteome and optimized by directed evolution using phage display. This method was applied to successfully design scaffolds that bind to epidermal growth factor receptor (EGFR) domain II, the interface of EGFR dimerization, with high reactivity toward the target surface patch of EGFR domain II. One potential application of these tailor-made protein interactions is the development of therapeutic agents against specific protein targets.

The structures of the kinase domain and UBA domain of MPK38 suggest the activation mechanism for kinase activity.

Murine protein serine/threonine kinase 38 (MPK38) is the murine orthologue of human maternal embryonic leucine-zipper kinase (MELK), which belongs to the SNF1/AMPK family. MELK is considered to be a promising drug target for anticancer therapy because overexpression and hyperactivation of MELK is correlated with several human cancers. Activation of MPK38 requires the extended sequence (ExS) containing the ubiquitin-associated (UBA) linker and UBA domain and phosphorylation of the activation loop. However, the activation mechanism of MPK38 is unknown. This paper reports the crystal structure of MPK38 (T167E), which mimics a phosphorylated state of the activation loop, in complex with AMP-PNP. In the MPK38 structure, the UBA linker forces an inward movement of the αC helix. Phosphorylation of the activation loop then induces movement of the activation loop towards the C-lobe and results in interlobar cleft closure. These processes generate a fully active state of MPK38. This structure suggests that MPK38 has a similar molecular mechanism regulating activation as in other kinases of the SNF1/AMPK family.

Crystal structure of Fushi tarazu factor 1 ligand binding domain/Fushi tarazu peptide complex identifies new class of nuclear receptors.

The interaction between the orphan nuclear receptor FTZ-F1 (Fushi tarazu factor 1) and the segmentation gene protein FTZ is critical for specifying alternate parasegments in the Drosophila embryo. Here, we have determined the structure of the FTZ-F1 ligand-binding domain (LBD)·FTZ peptide complex using x-ray crystallography. Strikingly, the ligand-binding pocket of the FTZ-F1 LBD is completely occupied by helix 6 (H6) of the receptor, whereas the cofactor FTZ binds the co-activator cleft site of the FTZ-F1 LBD. Our findings suggest that H6 is essential for transcriptional activity of FTZ-F1; this is further supported by data from mutagenesis and activity assays. These data suggest that FTZ-F1 might belong to a novel class of ligand-independent nuclear receptors. Our findings are intriguing given that the highly homologous human steroidogenic factor-1 and liver receptor homolog-1 LBDs exhibit sizable ligand-binding pockets occupied by putative ligand molecules.