A novel sphingomyelin/cholesterol domain-specific probe reveals the dynamics of the membrane domains during virus release and in Niemann-Pick type C

We identified a novel, nontoxic mushroom protein that specifically binds to a complex of sphingomyelin (SM), a major sphingolipid in mammalian cells, and cholesterol (Chol). The purified protein, termed nakanori, labeled cell surface domains in an SM- and Chol-dependent manner and decorated specific lipid domains that colocalized with inner leaflet small GTPase H-Ras, but not K-Ras. The use of nakanori as a lipid-domain-specific probe revealed altered distribution and dynamics of SM/Chol on the cell surface of Niemann-Pick type C fibroblasts, possibly explaining some of the disease phenotype. In addition, that nakanori treatment of epithelial cells after influenza virus infection potently inhibited virus release demonstrates the therapeutic value of targeting specific lipid domains for anti-viral treatment.-Makino, A., Abe, M., Ishitsuka, R., Murate, M., Kishimoto, T., Sakai, S., Hullin-Matsuda, F., Shimada, Y., Inaba, T., Miyatake, H., Tanaka, H., Kurahashi, A., Pack, C.-G., Kasai, R. S., Kubo, S., Schieber, N. L., Dohmae, N., Tochio, N., Hagiwara, K., Sasaki, Y., Aida, Y., Fujimori, F., Kigawa, T., Nishibori, K., Parton, R. G., Kusumi, A., Sako, Y., Anderluh, G., Yamashita, M., Kobayashi, T., Greimel, P., Kobayashi, T. A novel sphingomyelin/cholesterol domain-specific probe reveals the dynamics of the membrane domains during virus release and in Niemann-Pick type C.

High Density of Aligned Nanowire Treated with Polydopamine for Efficient Gene Silencing by siRNA According to Cell Membrane Perturbation

High aspect ratio nanomaterials, such as vertically aligned silicon nanowire (SiNW) substrates, are three-dimensional topological features for cell manipulations. A high density of SiNWs significantly affects not only cell adhesion and proliferation but also the delivery of biomolecules to cells. Here, we used polydopamine (PD) that simply formed a thin coating on various material surfaces by the action of dopamine as a bioinspired approach. The PD coating not only enhanced cell adhesion, spreading, and growth but also anchored more siRNA by adsorption and provided more surface concentration for substrate-mediated delivery. By comparing plain and SiNW surfaces with the same amount of loaded siRNA, we quantitatively found that PD coating efficiently anchored siRNA on the surface, which knocked down the expression of a specific gene by RNA interference. It was also found that the interaction of SiNWs with the cell membrane perturbed the lateral diffusion of lipids in the membrane by fluorescence recovery after photobleaching. The perturbation was considered to induce the effective delivery of siRNA into cells and allow the cells to carry out their biological functions. These results suggest promising applications of PD-coated, high-density SiNWs as simple, fast, and versatile platforms for transmembrane delivery of biomolecules.

Molecular Mechanism of HIV-1 Vpr for Binding to Importin-α

Viral protein R (Vpr) is an accessory gene product of human immunodeficiency virus type 1 (HIV-1) that plays multiple important roles associated with viral replication. Structural studies using NMR have revealed that Vpr consists of three α-helices and contains flexible N- and C-termini. However, the molecular mechanisms associated with Vpr function have not been elucidated. To investigate Vpr multifunctionality, we performed an X-ray crystallographic study of Vpr complexes containing importin-α, a known Vpr binding partner present in host cells. Elucidation of the crystal structure revealed that the flexible C-terminus changes its conformation to a twisted β-turn via an induced-fit mechanism, enabling binding to a minor nuclear localization signal (NLS) site of importin-α. The Vpr C-terminus can also bind with major NLS sites of importin-α in an extended conformation in different ways. These results, which represent the first reported crystallographic analysis of Vpr, demonstrate the multifunctional aspects that enable Vpr interaction with a variety of cellular proteins.

Synthesis of a Vpr-Binding Derivative for Use as a Novel HIV-1 Inhibitor

The emergence of multidrug-resistant viruses compromises the efficacy of anti-human immunodeficiency virus type 1 (HIV-1) therapy and limits treatment options. Therefore, new targets that can be used to develop novel antiviral agents need to be identified. We previously identified a potential parent compound, hematoxylin, which suppresses the nuclear import of HIV-1 via the Vpr-importin α interaction and inhibits HIV-1 replication in a Vpr-dependent manner by blocking nuclear import of the pre-integration complex. However, it was unstable. Here, we synthesized a stable derivative of hematoxylin that bound specifically and stably to Vpr and inhibited HIV-1 replication in macrophages. Furthermore, like hematoxylin, the derivative inhibited nuclear import of Vpr in an in vitro nuclear import assay, but had no effect on Vpr-induced G2/M phase cell cycle arrest or caspase activity. Interestingly, this derivative bound strongly to amino acid residues 54–74 within the C-terminal α-helical domain (αH3) of Vpr. These residues are highly conserved among different HIV strains, indicating that this region is a potential target for drug-resistant HIV-1 infection. Thus, we succeeded in developing a stable hematoxylin derivative that bound directly to Vpr, suggesting that specific inhibitors of the interaction between cells and viral accessory proteins may provide a new strategy for the treatment of HIV-1 infection.

Low-Molecular-Weight Polyethyleneimine Grafted Polythiophene for Efficient siRNA Delivery

Owing to its hydrophilicity, negative charge, small size, and labile degradation by endogenous nucleases, small interfering RNA (siRNA) delivery must be achieved by a carrier system. In this study, cationic copolymers composed of low-molecular-weight polyethylenimine and polythiophenes were synthesized and evaluated as novel self-tracking siRNA delivery vectors. The concept underlying the design of these copolymers is that hydrophobicity and rigidity of polythiophenes should enhance the transport of siRNA across the cell membrane and endosomal membrane. A gel retardation assay showed that the nanosized complexes formed between the copolymers and siRNA were stable even at a molar ratio of 1 : 2. The high cellular uptake (>80%) and localization of the copolymer vectors inside the cells were easily analyzed by tracking the fluorescence of polythiophene using fluorescent microscopy and cytometry. An in vitro luciferase knockdown (KD) assay in A549-luc cells demonstrated that the siRNA complexes with more hydrophobic copolymers achieved a higher KD efficiency of 52.8% without notable cytotoxicity, indicating protein-specific KD activity rather than solely the cytotoxicity of the materials. Our polythiophene copolymers should serve as novel, efficient, low cell toxicity, and label-free siRNA delivery systems.

Superior cell penetration by a rigid and anisotropic synthetic protein

Molecules with structural anisotropy and rigidity, such as asbestos, demonstrate high cell-penetrating activity but also high toxicity. Here we synthesize a biodegradable, rigid, and fibrous artificial protein, CCPC 140, as a potential vehicle for cellular delivery. CCPC 140 penetrated 100% of cells tested in vitro, even at a concentration of 3.1 nM-superior to previously reported cell-penetrating peptides. The effects of cell-strain-dependency and aspect ratio on the cell-penetrating activity of CCPC 140 were also investigated.

Amphiphilic gold nanoparticles displaying flexible bifurcated ligands as a carrier for siRNA delivery into the cell cytosol

The nanoparticle-based delivery of siRNA with a noncationic outermost surface at a low particle concentration is greatly desired. We newly synthesized a bifurcated ligand (BL) possessing hydrophobic and hydrophilic arms as a surface ligand for gold nanoparticles (AuNPs) to allow siRNA delivery. The concept underlying the design of this ligand is that amphiphilic property should allow AuNPs to permeate the cell cytosol thorough the endosomal membrane. BLs and quaternary cationic ligands were codisplayed on 40 nm AuNPs, which were subsequently coated with siRNA via electrostatic interaction. The number of siRNAs immobilized on a single nanoparticle was 26, and the conjugate showed a negative zeta potential due to siRNAs on the outermost surface of the AuNPs. Apparent gene silencing of luciferase expression in HeLa cells was achieved at an AuNP concentration as low as 60 pM. Almost no gene silencing was observed for AuNPs not displaying BLs. To reveal the effect of the BL, we compared the number of AuNPs internalized into HeLa cells and the localization in the cytosol between AuNPs displaying and those not displaying BLs. These analyses indicated that the role of BLs is not only the simple promotion of cellular uptake but also involves the enhancement of AuNPs permeation into the cytosol from the endosomes, leading to effective gene silencing.

Enhanced cellular uptake of amphiphilic gold nanoparticles with ester functionality

Gold nanoparticles (AuNPs) coated with ester-headed or ether-headed PEG ligands were synthesized.

Importin α3/Qip1 is involved in multiplication of mutant influenza virus with alanine mutation at amino acid 9 independently of nuclear transport function

The nucleoprotein (NP) of influenza A virus is transported into the nucleus via the classical importin α/β pathway, and proceeds via nuclear localization signals (NLSs) recognized by importin α molecules. Although NP binds to importin α isoforms Rch1, Qip1 and NPI-1, the role of each individual isoform during the nuclear transport of NP and replication of the influenza virus remains unknown. In this study, we examined the contribution of importin α isoforms for nuclear localization of NP and viral growth using a panel of NP mutants containing serial alanine replacements within an unconventional NLS of NP. Alanine mutation at amino acid 8 (R8A) caused a significant reduction in the nuclear localization and binding to the three importin isoforms. The R8A NP mutant virus did not generate by reverse-genetics approach. This indicates that position 8 is the main site that mediates nuclear localization via interactions with Rch1, Qip1 and NPI-1, and subsequent viral production. This was confirmed by the finding that the conservation of amino acid 8 in human- and avian-origin influenza virus NP was necessary for virus propagation. By contrast, another mutant, S9A NP, which localized in the nucleus, caused a reduction in viral growth and vRNA transcription, suggesting that the unconventional NLS within NP may be associated with nuclear transport, vRNA transcription and viral replication through independent pathways. Interestingly, the N-terminal 110-amino acid region, which contained the unconventional NLS with S9A mutation, mainly bound to Qip1. Furthermore, activities of vRNA transcription and replication of S9A NP mutants were decreased by silencing Qip1 in without changing nuclear localization, indicating that Qip1 involves in multiplication of S9A mutant virus independently of nuclear transport function. Collectively, our results demonstrate the unconventional NLS within NP might have the additional ability to regulate the viral replication that is independent of nuclear localization activity via interactions with Qip1.

An evaluation study of EGFR mutation tests utilized for non-small-cell lung cancer in the diagnostic setting

BACKGROUND

Epidermal growth factor receptor (EGFR) mutation is predictive for the efficacy of EGFR tyrosine kinase inhibitors in advanced non-small-cell lung cancer (NSCLC) treatment. We evaluated the performance, sensitivity, and concordance between five EGFR tests.

MATERIALS AND METHODS

DNA admixtures (n = 34; 1%-50% mutant plasmid DNA) and samples from NSCLC patients [116 formalin-fixed paraffin-embedded (FFPE) tissue, 29 matched bronchofiberscopic brushing (BB) cytology, and 20 additional pleural effusion (PE) cytology samples] were analyzed. EGFR mutation tests were PCR-Invader, peptide nucleic acid-locked nucleic acid PCR clamp, direct sequencing, Cycleave, and Scorpion Amplification Refractory Mutation System (ARMS). Analysis success, mutation status, and concordance rates were assessed.

RESULTS

All tests except direct sequencing detected four mutation types at ≥1% mutant DNA. Analysis success rates were 91.4%-100% (FFPE) and 100% (BB and PE cytology), respectively. Inter-assay concordance rates of successfully analyzed samples were 94.3%-100% (FFPE; kappa coefficients: 0.88-1.00), 93.1%-100% (BB cytology; 0.86-1.00), and 85.0%-100% (PE cytology; 0.70-1.00), and 93.1%-96.6% (0.86-0.93) between BB cytology and matched FFPE.

CONCLUSIONS

All EGFR assays carried out comparably in the analysis of FFPE and cytology samples. Cytology-derived DNA is a viable alternative to FFPE samples for analyzing EGFR mutations.