Cyclization of Peptides Enhances the Inhibitory Activity against Ganglioside-Induced Aß Fibril Formation.

Alzheimer's disease is a progressive neurodegenerative disease and is the most common cause of dementia. It has been reported that the assembly of amyloid ß-protein (Aß) on the cell membrane is induced by the interaction of the Aß monomer with gangliosides such as GM1. The ganglioside-bound Aß (GAß) complex acts as a seed to promote the toxic assembly of the Aß fibrils. In a previous study, we found that a GM1 cluster-binding peptide (GCBP) specifically recognizes Aß-sensitive ganglioside nanoclusters and inhibits the assembly of Aß on a GM1-containing lipid membrane. In this study, cysteine-substituted double mutants of GCBP were designed and cyclized by intramolecular disulfide bond formation. Affinity assays indicated that one of the cyclic peptides had a higher affinity to a GM1-containing membrane compared to that of GCBP. Furthermore, surface topography analysis indicated that this peptide recognizes GM1 nanoclusters on the lipid membrane. An evaluation of the inhibitory kinetics indicated that the cyclic peptide could inhibit the formation of Aß fibrils with an IC50 value of 1.2 fM, which is 10,000-fold higher than that of GCBP. The cyclic peptide was also shown to have a clearance effect on Aß fibrils deposited on the lipid membrane and suppressed the formation of toxic Aß assemblies. Our results indicate that the cyclic peptide that binds to the Aß-sensitive ganglioside nanocluster is a potential novel inhibitor of ganglioside-induced Aß assembly.

Effects of the Magnetic Orientation of M13 Bacteriophage on Phage Display Selection.

Although phage display selection using a library of M13 bacteriophage has become a powerful tool for finding peptides that bind to target materials on demand, a remaining concern of this method is the interference by the M13 main body, which is a huge filament >103  times larger than the displayed peptide, and therefore would nonspecifically adhere to the target or sterically inhibit the binding of the displayed peptide. Meanwhile, filamentous phages are known to be orientable by an external magnetic field. If M13 filaments are magnetically oriented during the library selection, their angular arrangement relative to the target surface would be changed, being expected to control the interference by the M13 main body. This study reports that the magnetic orientation of M13 filaments vertical to the target surface significantly affects the selection. When the target surface was affinitive to the M13 main body, this orientation notably suppressed the nonspecific adhesion. Furthermore, when the target surface was less affinitive to the M13 main body and intrinsically free from the nonspecific adhesion, this orientation drastically changed the population of M13 clones obtained through library selection. The method of using no chemicals but only a physical stimulus is simple, clean, and expected to expand the scope of phage display selection.

The sialyl-Tn antigen synthase genes regulates migration-proliferation dichotomy in prostate cancer cells under hypoxia.

A low-oxygen (hypoxia) tumor microenvironment can facilitate chemotherapy and radiation therapy resistance in tumors and is associated with a poor prognosis. Hypoxia also affects PCa (prostate cancer) phenotype transformation and causes therapeutic resistance. Although O-glycans are known to be involved in the malignancy of various cancers under hypoxia, the expression and function of O-glycans in PCa are not well understood. In this study, the saccharide primer method was employed to analyze O-glycan expression in PCa cells. Results showed that the expression of sTn antigens was increased in PCa cells under hypoxia. Furthermore, it was found that ST6GalNAc1, the sTn antigen synthase gene, was involved in the migration-proliferation dichotomy and drug resistance in PCa cells under hypoxia. The results of this study will contribute to the development of novel diagnostic markers and drug targets for PCa under hypoxia.

Endocytosis-Like Vesicle Fission Mediated by a Membrane-Expanding Molecular Machine Enables Virus Encapsulation for In Vivo Delivery.

Biological membranes are functionalized by membrane-associated protein machinery. Membrane-associated transport processes, such as endocytosis, represent a fundamental and universal function mediated by membrane-deforming protein machines, by which small biomolecules and even micrometer-size substances can be transported via encapsulation into membrane vesicles. Although synthetic molecules that induce dynamic membrane deformation have been reported, a molecular approach enabling membrane transport in which membrane deformation is coupled with substance binding and transport remains critically lacking. Here, we developed an amphiphilic molecular machine containing a photoresponsive diazocine core (AzoMEx) that localizes in a phospholipid membrane. Upon photoirradiation, AzoMEx expands the liposomal membrane to bias vesicles toward outside-in fission in the membrane deformation process. Cargo components, including micrometer-size M13 bacteriophages that interact with AzoMEx, are efficiently incorporated into the vesicles through the outside-in fission. Encapsulated M13 bacteriophages are transiently protected from the external environment and therefore retain biological activity during distribution throughout the body via the blood following administration. This research developed a molecular approach using synthetic molecular machinery for membrane functionalization to transport micrometer-size substances and objects via vesicle encapsulation. The molecular design demonstrated in this study to expand the membrane for deformation and binding to a cargo component can lead to the development of drug delivery materials and chemical tools for controlling cellular activities.

Dihydromaniwamycin E, a Heat-Shock Metabolite from Thermotolerant Streptomyces sp. JA74, Exhibiting Antiviral Activity against Influenza and SARS-CoV-2 Viruses.

Dihydromaniwamycin E (1), a new maniwamycin derivative featuring an azoxy moiety, has been isolated from the culture extract of thermotolerant Streptomyces sp. JA74 along with the known analogue maniwamycin E (2). Compound 1 is produced only by cultivation of strain JA74 at 45 °C, and this type of compound has been previously designated a "heat shock metabolite (HSM)" by our research group. Compound 2 is detected as a production-enhanced metabolite at high temperature. Structures of 1 and 2 are elucidated by NMR and MS spectroscopic analyses. The absolute structure of 1 is determined after the total synthesis of four stereoisomers. Though the absolute structure of 2 has been proposed to be the same as the structure of maniwamycin D, the NMR and the optical rotation value of 2 are in agreement with those of maniwamycin E. Therefore, this study proposes a structural revision of maniwamycins D and E. Compounds 1 and 2 show inhibitory activity against the influenza (H1N1) virus infection of MDCK cells, demonstrating IC50 values of 25.7 and 63.2 µM, respectively. Notably, 1 and 2 display antiviral activity against SARS-CoV-2, the causative agent of COVID-19, when used to infect 293TA and VeroE6T cells, with 1 and 2 showing IC50 values (for infection of 293TA cells) of 19.7 and 9.7 µM, respectively. The two compounds do not exhibit cytotoxicity in these cell lines at those IC50 concentrations.

Effective Cell Transfection in An Ultrasonically Levitated Droplet for Sustainable Technology.

The levitation methodology, which enables us to operate a contactless reaction without a container, is likely to be a revolutionary technology in the fields of chemistry and biology to reduce the plastic waste in life science laboratories. Here, the authors show that plasmid DNA can be effectively transfected into animal cells in a floating droplet of culture medium levitated using ultrasonic standing waves. The data indicate that there is no significant damage to the plasmid and cells during the levitating transfection time, and the transgene expression efficiency and cellular uptake in the droplet are significantly higher than those in the conventional tube, with and without shaking. These results suggest the consolidation of the endocytic uptake pathway into macropinocytosis, indicating that ultrasonic levitation induced a change in cell characteristics. This study suggests that transfection methodology using ultrasonic levitation has the potential to advance the current experimental procedures in the field of cell engineering, in addition to presenting a revolutionary containerless reactor for sustainable technology.

Functional analysis of GCNT3 for cell migration and EMT of castration-resistant prostate cancer cells.

Castration-resistant prostate cancer (CRPC) is a malignant tumor that is resistant to androgen deprivation therapy. Treatments for CRPC are limited, and no diagnostic markers are currently available. O-glycans are known to play an important role in cell proliferation, migration, invasion, and metastasis of cancer cells. However, the differences in the O-glycan expression profiles for normal prostate cancer (PCa) cells compared with CRPC cells have not yet been investigated. In this study, the saccharide primer method was employed to analyze the O-glycans expressed in CRPC cells. Expression levels of core 4-type O-glycans were significantly increased in CRPC cells. Furthermore, the expression level of N-Acetylglucosaminyltransferase 3 (GCNT3), a core 4-type O-glycan synthase gene, was increased in CRPC cells. The expression of core 4-type O-glycans and GCNT3 was presumed to be regulated by androgen deprivation. GCNT3 knockdown induced cell migration and epithelial-mesenchymal transition. These observations elucidate the mechanism of acquisition of castration resistance in PCa and offer new possibilities for the development of diagnostic markers and therapeutic targets in the treatment of PCa.

Ganglioside Nanocluster-Targeting Peptidyl Inhibitor Prevents Amyloid ß Fibril Formation on the Neuronal Membrane.

Neurotoxicity caused by peptide and protein aggregates is associated with the onset of neurodegenerative diseases. Accumulation of the amyloid ß protein (Aß) induced by neuronal ganglioside-enriched nanodomains (nanoclusters) in the presynaptic neuronal membrane, resulting in toxic oligomeric and fibrous forms, is implicated in the onset of Alzheimer's disease (AD). In the current study, we found that the ganglioside cluster-binding peptide (GCBP), a pentadecapeptide VWRLLAPPFSNRLLP that binds to ganglioside-enriched nanoclusters, inhibits the formation of Aß assemblies with an IC50 of 12 pM and also removes Aß fibrils deposited on the lipid membrane. Thus, in addition to inhibiting Aß assembly formation, GCBP effectively clears toxic Aß assemblies as well, thereby suppressing neuronal cellular damage and death induced by such assemblies. These results indicate that ganglioside cluster-binding molecules may act as novel Aß-targeting drugs with a unique mechanism of action that may be utilized to ameliorate AD.

Detection of Influenza Virus by Agglutination of Microparticles Immobilized a Mixed Glycan Receptor Produced from Cells.

The hemagglutination inhibition (HAI) assay is one of the detection methods for influenza virus (IFV) under global influenza surveillance, which uses freshly prepared animal red blood cells (RBCs). Here, we demonstrate that a mixed glycan-modified polystyrene microparticle, which can be chemically prepared in advance, can replace animal RBCs in the HAI assay. A mixture of azide-conjugated glycans containing sialyl- and sulfated-lactose moieties was produced from Madin-Darby canine kidney (MDCK) cells, which are used for IFV isolation, and then immobilized on the surface of a polystyrene microparticle using click chemistry. Human HA and IFV were detected with high sensitivity when using the mixed glycan-immobilized particle.

In vitro synthesis of mucin-type O-glycans using saccharide primers comprising GalNAc-Ser and GalNAc-Thr residues.

Mucin-type O-glycosylation of serine or threonine residue in proteins is known to be one of the major post-translational modifications. In this study, two novel alkyl glycosides, Nα-lauryl-O-(2-acetamido-2-deoxy-α-d-galactopyranosyl)-l-serineamide (GalNAc-Ser-C12) and Nα-lauryl-O-(2-acetamido-2-deoxy-α-d-galactopyranosyl)-l-threonineamide (GalNAc-Thr-C12) were synthesized as saccharide primers to prime mucin-type O-glycan biosynthesis in cells. Upon incubating human gastric cancer MKN45 cells with the saccharide primers, 22 glycosylated products were obtained, and their structures were analyzed using liquid chromatography-mass spectrometry and enzyme digestion. The amounts of glycosylated products were dependent on the amino acid residues in the saccharide primers. For example, in vitro synthesis of T antigen (Galß1-3GalNAc), fucosyl-T (Fucα1-2Galß1-3GalNAc), and sialyl-T (NeuAcα2-3Galß1-3GalNAc) preferred a serine residue, whereas sialyl-Tn (NeuAcα2-6GalNAc) preferred a threonine residue. Furthermore, the glycosylated products derived from GalNAc-Ser/Thr-C12 and Gal-GalNAc-Ser/Thr-C12 using cell-free synthesis showed the same amino acid selectivity as those in the cell experiments. These results indicate that glycosyltransferases involved in the biosynthesis of mucin-type O-glycans distinguish amino acid residues conjugated to GalNAc. The saccharide primers developed in this study might be useful for comparing mucin-type oligosaccharides in cells and constructing oligosaccharide libraries to study cell function.

De Novo Design of Star-Shaped Glycoligands with Synthetic Polymer Structures toward an Influenza Hemagglutinin Inhibitor.

Synthetic polymers with well-defined structures allow the development of nanomaterials with additional functions beyond biopolymers. Herein, we demonstrate de novo design of star-shaped glycoligands to interact with hemagglutinin (HA) using well-defined synthetic polymers with the aim of developing an effective inhibitor for the influenza virus. Prior to the synthesis, the length of the star polymer chains was predicted using the Gaussian model of synthetic polymers, and the degree of polymerization required to achieve multivalent binding to three carbohydrate recognition domains (CRDs) of HA was estimated. The star polymer with the predicted degree of polymerization was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, and 6'-sialyllactose was conjugated as the glycoepitope for HA. The designed glycoligand exhibited the strongest interaction with HA as a result of multivalent binding. This finding demonstrated that the biological function of the synthetic polymer could be controlled by precisely defining the polymer structures.

Motobamide, an Antitrypanosomal Cyclic Peptide from a Leptolyngbya sp. Marine Cyanobacterium.

Motobamide (1), a new cyclic peptide containing a C-prenylated cyclotryptophan residue, was isolated from a marine Leptolyngbya sp. cyanobacterium. Its planar structure was established by spectroscopic and MS/MS analyses. The absolute configuration was elucidated based on a combination of chemical degradations, chiral-phase HPLC analyses, spectroscopic analyses, and computational chemistry. Motobamide (1) moderately inhibited the growth of bloodstream forms of Trypanosoma brucei rhodesiense (IC50 2.3 µM). However, it exhibited a weaker cytotoxicity against normal human cells (IC50 55 µM).

Heterogeneous Ganglioside-Enriched Nanoclusters with Different Densities in Membrane Rafts Detected by a Peptidyl Molecular Probe.

The specific features of the lateral distribution of gangliosides play key roles in cell-cell communications and the onset of various diseases related to the plasma membrane. We herein demonstrated that an artificial peptide identified from a phage-displayed library is available as a molecular probe for specific ganglioside nanoclustering sites in caveolae/membrane rafts on the cell surface. Atomic force microscopy studies indicated that the peptide specifically binds to the highly enriched monosialoganglioside GM1 nanodomains of reconstituted lipid bilayers composed of GM1, sphingomyelin, cholesterol, and unsaturated phospholipids. The ganglioside-containing area recognized by the peptide on the surface of PC12 cells was part of the area recognized by the cholera toxin B subunit, which has high affinity for GM1. Furthermore, the peptide bound to the cell surface after a treatment with methyl-ß-cyclodextrin (MßCD), which disrupts membrane rafts by removing cholesterol. The present results indicate that there are heterogeneous ganglioside clusters with different ganglioside densities in caveolae/membrane rafts, and the peptidyl probe selectively recognizes the high-density ganglioside nanodomain that resists the MßCD treatment. This peptidyl probe will be useful for obtaining information on the lipid organization of the cell membrane and will help clarify the mechanisms by which the lateral distribution of gangliosides affects biological functions and the onset of diseases.

Avian Influenza Virus Detection by Optimized Peptide Termination on a Boron-Doped Diamond Electrode.

The development of a simple detection method with high sensitivity is essential for the diagnosis and surveillance of infectious diseases. Previously, we constructed a sensitive biosensor for the detection of pathological human influenza viruses using a boron-doped diamond electrode terminated with a sialyloligosaccharide receptor-mimic peptide that could bind to hemagglutinins involved in viral infection. Circulation of influenza induced by the avian virus in humans has become a major public health concern, and methods for the detection of avian viruses are urgently needed. Here, peptide density and dendrimer generation terminated on the electrode altered the efficiency of viral binding to the electrode surface, thus significantly enhancing charge-transfer resistance measured by electrochemical impedance spectroscopy. The peptide-terminated electrodes exhibited an excellent detection limit of less than one plaque-forming unit of seasonal H1N1 and H3N2 viruses. Furthermore, the improved electrode was detectable for avian viruses isolated from H5N3, H7N1, and H9N2, showing the potential for the detection of all subtypes of influenza A virus, including new subtypes. The peptide-based electrochemical architecture provided a promising approach to biosensors for ultrasensitive detection of pathogenic microorganisms.

Ikoamide, an Antimalarial Lipopeptide from an Okeania sp. Marine Cyanobacterium.

An antimalarial lipopeptide, ikoamide, was isolated from an Okeania sp. marine cyanobacterium. Its gross structure was established by spectroscopic analyses, and the absolute configuration was clarified based on a combination of chiral-phase HPLC analyses, spectroscopic analyses, and derivatization reactions. Ikoamide showed strong antimalarial activity with an IC50 value of 0.14 µM without cytotoxicity against human cancer cell lines at 10 µM.

Synthesis of Various Glycopolymers Bearing Sialyllactose and the Effect of Their Molecular Mobility on Interaction with the Influenza Virus.

Synthetic glyco-ligands are promising candidates for effective nanomedicines against pathogens. Glycopolymers bearing sialyl-oligosaccharides interact with hemagglutinin present on the surface of influenza viruses. In designing new glycopolymers that further enhance the interaction with viruses, both static and dynamic properties of the glycopolymers should be considered. In this report, we evaluated the correlation between dynamic properties of glycopolymers and their interaction with the influenza virus. Glycopolymers with pendant sialyllactoses and various linker structures were synthesized, and their molecular mobility was determined by proton spin-spin relaxation time measurements. The molecular mobility of the glycounits increased as the length of the linker structures increased. Interestingly, glycopolymers with the medium-length linker structure exhibited the strongest interaction with the influenza virus, suggesting that optimal molecular mobility is required for maximizing multivalent interactions with the target.

Topological Design of Star Glycopolymers for Controlling the Interaction with the Influenza Virus.

The precise design of synthetic polymer ligands using controlled polymerization techniques provides an advantage for the field of nanoscience. We report the topological design of glyco-ligands based on synthetic polymers for targeting hemagglutinin (HA, lectin on the influenza virus). To achieve precise arrangement of the glycounits toward the sugar-binding pockets of HA, triarm star glycopolymers were synthesized. The interaction of the star glycopolymers with HA was found to depend on the length of the polymer arms and was maximized when the hydrodynamic diameter of the star glycopolymer was comparable to the distance between the sugar-binding pockets of HA. Following the formula of multivalent interaction, the number of binding sites in the interaction of the glycopolymers with HA was estimated as 1.8-2.7. Considering one HA molecule has three sugar-binding pockets, these values were reasonable. The binding mode of synthetic glycopolymer-ligands toward lectins could be tuned using controlled radical polymerization techniques.

Hoshinoamides A and B, Acyclic Lipopeptides from the Marine Cyanobacterium Caldora penicillata.

Hoshinoamides A (1) and B (2), new acyclic lipopeptides, were isolated from the marine cyanobacterium Caldora penicillata. Their structures were elucidated by spectroscopic analyses and degradation reactions. Hoshinoamides A (1) and B (2) did not exhibit any cytotoxicity against HeLa cells at 10 µM, but inhibited the in vitro growth of the malarial parasite Plasmodium falciparum (IC50 = 0.52 and 1.0 µM, respectively).

Amyloid-ß fibrils assembled on ganglioside-enriched membranes contain both parallel ß-sheets and turns.

Some protein and peptide aggregates, such as those of amyloid-ß protein (Aß), are neurotoxic and have been implicated in several neurodegenerative diseases. Aß accumulates at nanoclusters enriched in neuronal lipids called gangliosides in the presynaptic neuronal membrane, and the resulting oligomeric and/or fibrous forms accelerate the development of Alzheimer's disease. Although the presence of Aß deposits at such nanoclusters is known, the mechanism of their assembly and the relationship between Aß secondary structure and topography are still unclear. Here, we first confirmed by atomic force microscopy that Aß40 fibrils can be obtained by incubating seed-free Aß40 monomers with a membrane composed of sphingomyelin, cholesterol, and the ganglioside GM1. Using Fourier transform infrared (FTIR) reflection-absorption spectroscopy, we then found that these lipid-associated fibrils contained parallel ß-sheets, whereas self-assembled Aß40 molecules formed antiparallel ß-sheets. We also found that the fibrils obtained at GM1-rich nanoclusters were generated from turn Aß40 Our findings indicate that Aß generally self-assembles into antiparallel ß-structures but can also form protofibrils with parallel ß-sheets by interacting with ganglioside-bound Aß. We concluded that by promoting the formation of parallel ß-sheets, highly ganglioside-enriched nanoclusters help accelerate the elongation of Aß fibrils. These results advance our understanding of ganglioside-induced Aß fibril formation in neuronal membranes and may help inform the development of additional therapies for Alzheimer's disease.

Izenamides A and B, Statine-Containing Depsipeptides, and an Analogue from a Marine Cyanobacterium.

Izenamides A, B, and C (1-3), new linear depsipeptides, were isolated from a taxonomically distinct marine cyanobacterium. Izenamides A and B contain a statine moiety [(3 S,4 S)-4-amino-3-hydroxy-6-methylheptanoic acid] and inhibited the activity of cathepsin D, an aspartic peptidase. Meanwhile, izenamides did not show growth-inhibitory activity against HeLa, HL60, or MCF-7 cells at up to 10 µM.