Poly L-arginine Research Articles

Poly-l-arginine promotes ferroptosis in asthmatic airway epithelial cells by modulating PBX1/GABARAPL1 axis.

Eosinophils play a featured role among inflammatory cells participating in the onset and development of asthma. Activated eosinophils release several cytotoxic granular proteins, such as major basic protein (MBP), posing a significant threat to airway epithelium. Ferroptosis, a novel form of cell death, is gaining recognition for its involvement in asthma pathogenesis, though the specific mechanisms remain largely unknown. Herein, we revealed that poly-l-arginine (PLA), an MBP mimic, induced ferroptosis in airway epithelium by downregulating γ-aminobutyric acid receptor-associated protein-like 1 (GABARAPL1). Reduced GABARAPL1 expression was further confirmed in ovalbumin (OVA)-induced asthma mice and PLA-treated human airway organoids (hAOs). Mechanistically, PLA activated mechanistic target of rapamycin complex 1 (mTORC1) signaling, inhibiting pre-B-cell leukemia transcription factor 1 (PBX1), which in turn leads to transcriptional downregulation of GABARAPL1. Furthermore, MBP extracted from eosinophils, similar to PLA, induced ferroptosis in airway epithelial cells, as well as modulating mTORC1/PBX1/GABARAPL1 pathway. Finally, Ferrostatin-1 treatment or GABARAPL1 overexpression alleviated ferroptosis and airway inflammation in asthmatic mice. Overall, our findings highlight the cell communication between eosinophils and airway epithelial cells. MBP modulates the mTORC1/PBX1/GABARAPL1 axis, thereby serving as a significant contributor to ferroptosis in airway epithelium and airway inflammation. This suggests that suppressing ferroptosis in airway epithelium or targeting eosinophils and MBP could lead to novel therapeutic strategies for asthma management.

Kinetics of Human Serum Albumin Adsorption on Polycation Functionalized Silica.

The adsorption kinetics of human serum albumin (HSA) on bare and poly-L-arginine (PARG)-modified silica substrates were investigated using reflectometry and atomic force microscopy (AFM). Measurements were carried out at various pHs, flow rates and albumin concentrations in the 10 and 150 mM NaCl solutions. The mass transfer rate constants and the maximum protein coverages were determined for the bare silica at pH 4.0 and theoretically interpreted in terms of the hybrid random sequential adsorption model. These results were used as reference data for the analysis of adsorption kinetics at larger pHs. It was shown that the adsorption on bare silica rapidly decreased with pH and became negligible at pH 7.4. The albumin adsorption on PARG-functionalized silica showed an opposite trend, i.e., it was negligible at pH 4 and attained maximum values at pH 7.4 and 150 mM NaCl, the conditions corresponding to the blood serum environment. These results were interpreted as the evidence of a significant role of electrostatic interactions in the albumin adsorption on the bare and PARG-modified silica. It was also argued that our results can serve as useful reference data enabling a proper interpretation of protein adsorption on substrates functionalized by polyelectrolytes.

Bulk Biopolyelectrolyte Complexes from Homopolypeptides: Solid "Salt Bridges".

Salt bridges, pairings between oppositely charged amino acids, are dispersed throughout proteins to assist folding and interactions. Biopolyelectrolyte complexes (BioPECs) were made between the homopolypeptides poly-l-arginine (PLR) and poly-l-lysine (PLK) with sodium triphosphate (STPP), as well as from polypeptide-only combinations. Viscoelastic measurements on these high salt bridge density materials showed many were solid, even glassy, in nature. Although the polypeptide-phosphate complexes had similar moduli at room temperature, the PLR-STPP complex displayed an unusual melting event above 70 °C not seen in PLK-STPP. This event was supported with differential scanning calorimetry. Infrared spectroscopy showed the PLK-STPP system contained β-sheets, while PLR-STPP did not. Stoichiometric, macroscopic BioPECs of PLR and PLK with poly-l-aspartic acid (PLD) and poly-l-glutamic acid (PLE) were made. PLR-PLD was found to undergo a melting event similar to that in PLR-STPP. ATR-FTIR studies showed that BioPECs made with PLD do not contain β-sheets, while those composed of PLE do. This work illustrates an expanded palette of unique properties from these biomaterials, such as strong viscoelastic differences between PECs containing PLE and PLD, even though they differ by only one carbon on the side chain.

Molecular mechanisms of pH-tunable stability and surface coverage of polypeptide films

Streaming potential and quartz crystal microbalance measurements, combined with all-atom molecular dynamics simulations, were used to study the pH dependency of the adsorption of two basic homopolypeptides, poly-L-lysine (PLL) and poly-L-arginine (PARG), on α-quartz surface. We report that the observed adsorption behavior rises from an interplay of i) the change in the number of possible peptide-surface ion pairs between the charged moieties and ii) repulsive electrostatic interactions between the polypeptide molecules. For low pH values, polypeptide adsorption was strongest and stable monolayers were formed. However, electrostatic repulsion between the polypeptides led to a relatively low maximum surface coverage. On the other hand, higher pH led to more weakly bound, but significantly denser, peptide films with limited stability. Simulations indicate that electrostatic interactions are the main driving force for adsorption, while hydrogen bonding and non-specific interactions also contribute. Additionally, the important role of the counterions of the negatively charged quartz surface that form a positively charged ion adlayer is highlighted. Ion release of the condensed sodium ions at the charged surface occurs via displacement by polypeptide adsorption. The mechanisms revealed by this work provide systematic guidelines to engineering active surfaces of charged peptides with controlled surface coverage and reversible binding.

Increasing Angiogenesis Factors in Hypoxic Diabetic Wound Conditions by siRNA Delivery: Additive Effect of LbL-Gold Nanocarriers and Desloratadine-Induced Lysosomal Escape.

Impaired wound healing in people with diabetes has multifactorial causes, with insufficient neovascularization being one of the most important. Hypoxia-inducible factor-1 (HIF-1) plays a central role in the hypoxia-induced response by activating angiogenesis factors. As its activity is under precise regulatory control of prolyl-hydroxylase domain 2 (PHD-2), downregulation of PHD-2 by small interfering RNA (siRNA) could stabilize HIF-1α and, therefore, upregulate the expression of pro-angiogenic factors as well. Intracellular delivery of siRNA can be achieved with nanocarriers that must fulfill several requirements, including high stability, low toxicity, and high transfection efficiency. Here, we designed and compared the performance of layer-by-layer self-assembled siRNA-loaded gold nanoparticles with two different outer layers—Chitosan (AuNP@CS) and Poly L-arginine (AuNP@PLA). Although both formulations have exactly the same core, we find that a PLA outer layer improves the endosomal escape of siRNA, and therefore, transfection efficiency, after endocytic uptake in NIH-3T3 cells. Furthermore, we found that endosomal escape of AuNP@PLA could be improved further when cells were additionally treated with desloratadine, thus outperforming commercial reagents such as Lipofectamine® and jetPRIME®. AuNP@PLA in combination with desloratadine was proven to induce PHD-2 silencing in fibroblasts, allowing upregulation of pro-angiogenic pathways. This finding in an in vitro context constitutes a first step towards improving diabetic wound healing with siRNA therapy.

Poly-L-arginine promotes asthma angiogenesis through induction of FGFBP1 in airway epithelial cells via activation of the mTORC1-STAT3 pathway

Angiogenesis is a key characteristic of asthma airway remodeling. By releasing cationic granule proteins, such as major basic protein (MBP), activated eosinophils play a prominent role in asthma, but the underlying mechanisms are still not fully understood. In this study, we demonstrated that fibroblast growth factor-binding protein 1 (FGFBP1) was dramatically upregulated in airway epithelial cell lines treated by poly-L-arginine (PLA), a mimic of MBP. Elevated FGFBP1 expression was also detected in asthma clinical samples, as well as in ovalbumin (OVA)-induced chronic asthma mouse models. PLA enhanced FGFBP1 expression through activation of the mechanistic target of rapamycin complex 1-signal transducer and activator of transcription 3 (mTORC1-STAT3) signaling pathway. STAT3 transactivated FGFBP1 by directly binding to the promoter of the FGFBP1 gene. Furthermore, we identified that FGFBP1 secreted by PLA-treated airway epithelial cells served as a proangiogenesis factor. Lastly, we found the mTORC1-STAT3-FGFBP1 signaling pathway was activated in an OVA-induced chronic asthma model with airway remodeling features. Rapamycin treatment alleviated respiratory symptoms and reduced angiogenesis in asthmatic mice. Therefore, activation of the mTORC1-STAT3-FGFBP1 pathway in the airway epithelium contributes to the progress of angiogenesis and should be targeted for the treatment of asthma.

Luminescent switch of polysaccharide-peptide-quantum dot nanostructures for targeted-intracellular imaging of glioblastoma cells

Abstract Glioblastoma multiforme (or GBM) remains one of the deadliest types of brain cancers. Nanomedicine can offer new strategies for fighting against GBM by combining the earliest possible diagnosis with multiple options of therapy. Hence, in this work, cysteine (Cys) and Poly-L-Arginine (PA) moieties were grafted to carboxymethyl cellulose (CMC) to produce biofunctional hybridized macromolecules (CMC_Cys and CMC_PA). These polymer-peptide conjugates were used simultaneously as surface capping ligands and biofunctional modifiers for the synthesis of ternary Ag-In-S (AIS) quantum dots (AIS QDs) via a green chemical process in aqueous medium and room temperature. These core-shell supramolecular nanostructures (AIS@CMC, AIS@CMC_Cys, and AIS@CMC_PA) were tested as fluorescent nanoprobes (“OFF-ON”) for targeted bioimaging and in vitro intracellular tracking of glioblastoma cells (GBM, U-87 MG). The nanosystems were characterized for physicochemical, structural, and morphological properties by NMR, UV–Vis, PL, FTIR, TEM/EDX/SAED, zeta potential, and DLS. Cytocompatibility was evaluated by mitochondrial activity assay, and confocal laser scanning microscopy was performed for investigating the kinetics of cellular uptake. The grafting caused a noticeable reduction of surface charges, associated with a drastic photoluminescence quenching (i.e., “OFF-state”) of AIS@CMC_Cys and AIS@CMC_PA compared to unmodified AIS@CMC. This effect was smartly applied for bioimaging GBM cells and for monitoring the internalization process by intracellular tracking, which underwent strong “de-quenching” at very early incubation times (~5 min). Thus, these novel hybrid nanocolloids produced via eco-friendly scalable aqueous process show potential as responsive fluorescent bioprobes for bioimaging and tracking intracellular pathways and mechanisms as a powerful weapon for fighting against brain cancer cells.

Selective Regulation of Neurons, Glial Cells, and Neural Stem/Precursor Cells by Poly(allylguanidine)-Coated Surfaces.

Poly(allylguanidine) (PAG) was synthesized and characterized as a polycationic coating material for culturing neurons, glial cells, and neural stem/precursor cells (NSPCs) to apply PAG for neural tissue engineering. For comparison, poly-d-lysine (PDL), the golden benchmark of the neuron cell culture system, was also used in this study. When PAG was subjected to a mixed culture of neurons and glial cells, cell adhesion and neurite extension of neuronal cells were clearly observed but only few glial cells could be found alongside the neurons. Compared to PDL, the significantly lower density of the glial fibrillary acidic protein-positive cells implied that PAG suppressed the glial cell development. Likewise, PAG was demonstrated to dominate the differentiation of NSPCs principally into neurons. To investigate whether the different effects of PAG and PDL on neuron and glial cell behaviors resulted from the difference of guanidinium cations and ammonium cations, poly-l-arginine (PLA) was included and compared in this study. Similar to PDL, PLA supported high neuron and glial cell viability simultaneously. Consequently, glial cell growth and viability restrained on PAG was not only affected by the side-chain guanidino groups but also by the backbone structure property. The absence of the peptide structure in the backbone of PAG and the conformation of coated PAG on tissue culture polystyrene possibly determined the polycationic biomaterial to limit the growth of glial cells.

Poly-l-arginine modifications alter the organization and secretion of collagen in SKH1-E mice.

Functionalized biomaterials interface with tissue upon implantation. There is a growing need to understand how materials properties influence this interaction so that efficient tissue engineering systems can be developed. In this study, we characterize collagen organization in response to functionalized glass beads implanted in SKH1-E mice. Poly-l-arginine (PLR) was modified with arginine derivatives to create a functionalized surface and was coated on glass beads. Tissue sections were removed 28 days post-implantation and were imaged using second harmonic generation (SHG) microscopy. These chemical modifications were able to alter the collagen distribution from highly aligned to disordered (17 ± 6 to 78 ± 1° full width at half-maximum (FWHM)) and the collagen III/I ratio (0.02 to 0.42). Principal component analysis (PCA) comparing the physical properties of the modifiers (e.g. hydrophobicity, molar volume, freely rotating bonds, polarizability) with the SHG analytically derived parameters (e.g. collagen III/I ratio, collagen orientation) was performed. Chemical properties of the PLR-like modifications including lipophilicity, along with the number of freely rotating bonds and the polarizability had significant effects on the collagen surrounding the implant, both in terms of collagen orientation as well as the production of collagen III. These findings demonstrate the possibility of tuning the foreign body response, in terms of collagen deposition and organization, to positively influence the acceptance of implanted biomaterials.

Biodegradable Alginate Polyelectrolyte Capsules As Plausible Biocompatible Delivery Carriers.

Polyelectrolyte capsules made of different biodegradable and nonbiodegradable polymers can be designed as systems for effective encapsulation and delivery of compounds. The objective of this work was to synthesize biocompatible and biodegradable capsules (<1 μm) by the layer-by-layer (LbL) approach using alginate (ALGI) and poly-l-arginine (PARG) polyelectrolytes with a pH-sensitive outer layer of EUDRAGIT L 100 (EuL) polymer. Those capsules were loaded with curcumin as a model therapeutic drug, which possesses antioxidant, anti-inflammatory, and anticancer activity. Encapsulation of drugs inside capsules protects its therapeutic activity and increases its bioavailability. We report the capsule stability, loading efficiency, drug release, as well as capsule degradation studies as a function of pH. Furthermore, in vitro biocompatibility studies of capsules including cell viability and uptake studies were performed using HeLa cells. The here synthesized capsules exhibited good reproducibility, spherical shape, and high monodispersibility. The capsules showed good loading efficiency and drug release profile dependent upon pH environment. The in vitro studies indicate that the capsules exhibited acceptable biocompatibility and are highly internalized by cells. Our study thus suggests that alginate LbL capsules could be used as an efficient drug carrier with effective encapsulation and successful in vitro release of cargo in the cell.

Interactions of Casein and Polypeptides in Multilayer Films Studied by FTIR and Molecular Dynamics.

Multilayer films containing α- and β-casein and polypeptides, poly-L-lysine (PLL), and poly-L-arginine (PLArg) were formed by the layer-by-layer technique and Fourier Transform InfraRed spectroscopy with Attenuated Total Reflection (FTIR-ATR) and FTIR/Grazing Angle analyzed their infrared spectra. We investigated the changes of conformations of casein and polypeptides in the complexes formed during the build-up of the films. To elucidate the differences in the mechanism of complex formation leading to various growths of (PLL/casein)n and (PLArg/casein)n films, we performed the molecular dynamics simulations of the systems consisting of short PLL and PLArg chains and the representative peptide chains—casein fragments, which consists of several aminoacid sequences. The results of the simulation indicated the preferential formation of hydrogen bonds of poly-L-arginine with phosphoserine and glutamic acid residues of caseins. FTIR spectra confirmed those, which revealed greater conformational changes during the formation of casein complex with poly-L-arginine than with poly-L-lysine resulting from stronger interactions, which was also reflected in the bigger growth of (PLArg/casein)n films with the number of deposited layers.

Transcriptomic Sequencing of Airway Epithelial Cell NCI-H292 Induced by Synthetic Cationic Polypeptides.

Eosinophil asthma is characterized by the infiltration of eosinophils to the bronchial epithelium. The toxic cationic protein released by eosinophils, mainly major basic protein (MBP), is one of the most important causative factors of epithelium damage. Poly-L-Arginine (PLA) is a kind of synthetic cationic polypeptides, which is widely used to mimic the effects of MBP on epithelial cells in vitro. However, little is known about the changes of differentially expressed genes (DEGs) and transcriptome profiles in cationic protein stimulated epithelial cells. In this study, we compared the expression of DEGs and transcriptome profiles between PLA-treated airway epithelial cells NCI-H292 and control. The results showed that there were a total of 230 DEGs, of which 86 were upregulated and 144 were downregulated. These DEGs were further analyzed using gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The results showed that the upregulated DEGs were involved in cholesterol synthesis, protein binding, and composition of cellular membranes, mainly enriched in metabolic and biosynthesis pathways. While downregulated DEGs were implicated in cell adhesion, extracellular matrix (ECM) composition and cytoskeleton and were enriched in ECM pathway. In conclusion, our research provided the mechanism of the cationic polypeptides acting on the airway epithelial cells on the basis of transcriptomic profile, and this could be regarded as important indications in unveiling the pathologic role of natural cationic proteins in the damage to epithelial cells of asthmatics.

Poly-L-Arginine Induces Apoptosis of NCI-H292 Cells via ERK1/2 Signaling Pathway.

Cationic protein is a cytotoxic protein secreted by eosinophils and takes part in the damage of airway epithelium in asthma. Poly-L-arginine (PLA), a synthetic cationic protein, is widely used to mimic the biological function of the natural cationic protein in vitro. Previous studies demonstrated the damage of the airway epithelial cells by cationic protein, but the molecular mechanism is unclear. The purpose of this study aimed at exploring whether PLA could induce apoptosis of human airway epithelial cells (NCI-H292) and the underlying mechanism. Methods. The morphology of apoptotic cells was observed by transmission electron microscopy. The rate of apoptosis was analyzed by flow cytometry (FCM). The expressions of the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), Bcl-2/Bax, and cleaved caspase-3 were assessed by western blot. Results. PLA can induce apoptosis in NCI-H292 cells in a concentration-dependent manner. Moreover, the phosphorylation of the ERK1/2 and the unbalance of Bcl2/Bax, as well as the activation of caspase-3, were involved in the PLA-induced apoptosis. Conclusions. PLA can induce the apoptosis in NCI-H292 cells, and this process at least involved the ERK1/2 and mitochondrial pathway. The results could have some indications in revealing the apoptotic damage of the airway epithelial cells. Besides, inhibition of cationic protein-induced apoptotic death in airway epithelial cells could be considered as a potential target of anti-injury or antiremodeling in asthmatics.

Multifunctional core-shell nanoplatforms (gold@graphene oxide) with mediated NIR thermal therapy to promote miRNA delivery

Recent insights into the nanomedicine have revealed that nanoplatforms enhance the efficacy of carrier in therapeutic applications. Here, multifunctional nanoplatforms were utilized in miRNA-101 delivery and NIR thermal therapy to induce apoptosis in breast cancer cells. Au nanorods (NRs) or nanospheres (NSs) covered with graphene oxide (GO) were prepared and functionalized with polyethylene glycol as a stabilizer and poly-L-arginine (P-L-Arg) as a targeting agent. In nanoplatforms, coupling Au@GO prepared stable structures with higher NIR reactivity. P-L-Arg substantially enhanced the cellular uptake and gene retardation of stuffs coated by them. However, rod-shape nanoplatforms indicated better performance in cellular uptake and gene transfection than spherical ones. NIR thermal therapy was implemented to improve gene release and in synergy with miRNA-101 activated the apoptotic pathway and decreased the viability of breast cancer cell (<20%). Briefly, presented delivery systems are potentially efficient in distinguishing cancer cells, miRNA internalization and controlling apoptosis of cancer cells.

Interfacial electrostatics of poly(vinylamine hydrochloride), poly(diallyldimethylammonium chloride), poly-l-lysine, and poly-l-arginine interacting with lipid bilayers.

Charge densities of cationic polymers adsorbed to lipid bilayers are estimated from second harmonic generation (SHG) spectroscopy and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The systems surveyed included poly(vinylamine hydrochloride) (PVAm), poly(diallyldimethylammonium chloride) (PDADMAC), poly-l-lysine (PLL), and poly-l-arginine (PLR), as well as polyalcohol controls. Upon accounting for the number of positive charges associated with each polyelectrolyte, the binding constants and apparent free energies of adsorption as estimated from SHG data are comparable despite differences in molecular masses and molecular structure, with ΔGads values of -61 ± 2, -58 ± 2, -57 ± 1, -52 ± 2, -52 ± 1 kJ mol-1 for PDADMAC400, PDADMAC100, PVAm, PLL, and PLR, respectively. Moreover, we find charge densities for polymer adlayers of approximately 0.3 C m-2 for poly(diallyldimethylammonium chloride) while those of poly(vinylamine) hydrochloride, poly-l-lysine, and poly-l-arginine are approximately 0.2 C m-2. Time-dependent studies indicate that polycation adsorption to supported lipid bilayers is only partially reversible for most of the polymers explored. Poly(diallyldimethylammonium chloride) does not demonstrate reversible binding even over long timescales (>8 hours).

SiRNA delivery using polyelectrolyte-gold nanoassemblies in neuronal cells for BACE1 gene silencing

Small interfering RNA (siRNA) mediated RNA interference is a versatile therapeutic tool for many intractable genetic disorders. Various nanoassemblies specifically designed to deliver the siRNAs could be utilized for efficient siRNA delivery which is one of the major concern for the success of this therapeutic. Thus, in the present study, polyelectrolyte-gold nanoassemblies (PE-Gold NAs) were selected for siRNA delivery of an in vitro verified siRNA. Three different polyelectrolytes (polyethyleneimine, citraconic anhydride modified poly (allylamine) hydrochloride and poly l-arginine) were used to formulate the PE-Gold NAs using the layer-by-layer technique. Successful physico-chemical characterizations of these PE-Gold NAs were performed using UV-Visible, FTIR, 1H-NMR spectroscopies, XRD, TEM, DLS and Zeta potential measurements. In vitro studies for the cytotoxicity, the uptake of these nanoassemblies and the gene silencing were carried out using these PE-Gold NAs in N2a and NB4 1A3 (murine neuronal) cell lines. The three selected PE-Gold NAs showed significant BACE1 (β-site APP cleaving enzyme 1) gene silencing (50–60%). This work demonstrates the potential of PE-Gold NAs to deliver siRNA targeting BACE1 in neuronal cells. Finally, it was concluded that different polyelectrolytes used in the PE-Gold NAs achieve different gene silencing due to the variation in their delivery efficiencies.

Self‐Propelled Soft Protein Microtubes with a Pt Nanoparticle Interior Surface

Human serum albumin (HSA) microtubes with an interior surface composed of Pt nanoparticles (PtNPs) are self-propelled in aqueous H2 O2 medium. They can capture cyanine dye and Escherichia coli (E. coli) efficiently. Microtubes were prepared by wet templating synthesis by using a track-etched polycarbonate (PC) membrane with alternate filtrations of aqueous HSA, poly-l-arginine (PLA), and citrate-PtNPs. Subsequent dissolution of the PC template yielded uniform hollow cylinders made of (PLA/HSA)8 PLA/PtNP stacking layers (1.16±0.02 μm outer diameter, ca. 23 μm length). In aqueous H2 O2 media, the soft protein microtubes are self-propelled by jetting O2 bubbles from the open-end terminus. The effects of H2 O2 and surfactant concentrations on the velocity were investigated. The swimming microtube captured cyanine dye in the HSA component of the wall. Addition of an intermediate γ-Fe3 O4 layer allowed manipulation of the direction of movement of the tubule by using a magnetic field. Because the exterior surface is positively charged, the bubble-propelled microtubes adsorbed E. coli with high efficiency. The removal ratio of E. coli by a single treatment reached 99 %.

From amino acids polymers, antimicrobial peptides, and histones, to their possible role in the pathogenesis of septic shock: a historical perspective.

This paper describes the evolution of our understanding of the biological role played by synthetic and natural antimicrobial cationic peptides and by the highly basic nuclear histones as modulators of infection, postinfectious sequelae, trauma, and coagulation phenomena. The authors discuss the effects of the synthetic polymers of basic poly α amino acids, poly l-lysine, and poly l-arginine on blood coagulation, fibrinolysis, bacterial killing, and blood vessels; the properties of natural and synthetic antimicrobial cationic peptides as potential replacements or adjuncts to antibiotics; polycations as opsonizing agents promoting endocytosis/phagocytosis; polycations and muramidases as activators of autolytic wall enzymes in bacteria, causing bacteriolysis and tissue damage; and polycations and nuclear histones as potential virulence factors and as markers of sepsis, septic shock, disseminated intravasclar coagulopathy, acute lung injury, pancreatitis, trauma, and other additional clinical disorders

Effect of poly-L-arginine in inhibiting scrapie prion protein of cultured cells.

Biological effect of poly-L-arginine (PLR), the linear homopolymer comprised of L-arginine, was investigated to determine the activity of suppressing prions. PLR decreased the level of scrapie prion protein (PrPSc) in cultured cells permanently infected with prions in a concentration-dependent manner. The PrPSc inhibition efficacy of PLR was greater than that of another prion-suppressant poly-L-lysine (PLK) in a molecular mass-dependent fashion. The effective concentration of PLR to inhibit prions was achieved safely below the cytotoxic concentrations, and overall cytotoxicity of PLR was similar to that of PLK. PLR did not alter the cellular prion protein (PrPC) level and was unable to change the states of preformed recombinant PrP aggregates and PrPSc from prion-infected cells. These data eliminate the possibility that the action mechanism of PLR is through removal of PrPC and pre-existing PrPSc. However, PLR formed complexes with plasminogen that stimulates prion propagation via conversion of PrPC to the misfolded isoform, PrPSc. The plasminogen-PLR complex demonstrated the greater positive surface charge values than the similar complex with PLK, raising the possibility that PLR interferes with the role of cofactor for PrPSc generation better than PLK.

Glycoprotein Nanotube Traps Influenza Virus

We report the synthesis, structure, and influenza A virus trapping capability of protein nanotubes with an internal wall of fetuin glycoprotein. The nanotubes were fabricated via the alternating layer-by-layer assembly of human serum albumin (HSA), poly-l-arginine (PLA), and fetuin into a track-etched polycarbonate (PC) membrane (pore size, 800 nm), followed by dissolution of the PC template. In an aqueous medium, the (PLA/HSA)5PLA/fetuin nanotubes captured influenza A virus PR8 (H1N1) efficiently, as revealed by ELISA measurements.