Embodying a stable alpha-helical protein structure through efficient chemical ligation via thioether formation

Lipid envelope-type nanoparticle incorporating a multifunctional peptide for systemic siRNA delivery to the pulmonary endothelium

A system that permits the delivery of cargoes to the lung endothelium would be extraordinarily useful in terms of curing a wide variety of lung-related diseases. This study describes the development of a multifunctional envelope-type nanodevice (MEND) that targets the lung endothelium, delivers its encapsulated siRNA to the cytoplasm, and eradicates lung metastasis. The key to the success can be attributed to the presence of a surface-modified GALA peptide that has dual functions: targeting the sialic acid-terminated sugar chains on the pulmonary endothelium and subsequently delivering the encapsulated cargoes to the cytosol via endosomal membrane fusion, analogous to the influenza virus. The active targeting of MENDs without the formation of large aggregates was verified by intravital real-time confocal laser scanning microscopy in living lung tissue. The GALA-modified MEND is a promising carrier that opens a new generation of therapeutic approaches for satisfying unmet medical needs in curing lung diseases.

Comparison between a multifunctional envelope-type nano device and lipoplex for delivery to the liver

The utility of using a multifunctional envelope-type nano device (MEND) for delivering a gene to the liver was examined. Lipotrust, a commercially available transfection reagent whose lipid composition is DC6- 14 :DOPE: cholesterol=4 : 3 : 3, was used as a reference. When Lipotrust was administrated intravenously, luciferase activity of the lung was 25 times higher than that of the liver. The luciferase activity of the lung was greatly reduced when a MEND was administered, even though the lipid composition of the lipid envelope was the same in both devices. Furthermore, the luciferase activity of the liver was 5 times higher than that for lipotrust, suggesting that the encapsulation of plasmid DNA (pDNA) in liposomes is more advantageous for delivering pDNA to the liver than complex formation. The isolation of parenchymal cells (PCs) and non-parenchymal cells (NPCs) showed that the MEND system is capable of expressing the luciferase protein more preferentially in NPCs than the lipoplex system. In addition, when the surface was modified with a pH-sensitive fusogenic peptide (GALA) used as a device for endosomal escape, overall liver luciferase activity was greatly enhanced. This suggests that endosomal escape is a limiting step for the MEND system. In the case of the GALA-modified MEND, the luciferase activity of PCs and NPCs was 18 times and 11 times higher than MEND system, while the transfection efficiency of NPCs was significantly higher compared to that of PCs. Collectively, these data show that a GALA-modified MEND prepared with DC6-14 :DOPE: cholesterol represents a promising device for NPCtargeting gene delivery in vivo.

Ornithine and tryptophan analogs as efficient polycations for short interference RNA delivery to tumor cells

The delivery of nucleic acids to cancer cells represents a potentially useful strategy. Previously, we developed a multifunctional envelope-type nano device (MEND) for the efficient delivery of plasmid DNA. In addition, we successfully delivered short interference RNA (siRNA) into cytoplasm using a MEND which contains siRNA particles that were produced using stearyl octaarginine (STR-R8). In the present study, to achieve further gene silencing activity compared with STR-R8, various additional polycations were screened. We used protamine and 10 different polypeptides containing random sequence of basic amino acids. The ability of these polycations to form nano particles with siRNA were evaluated by measuring the size and zeta-potential of produced nano particles, and as a consequence, 6 of the polycations were selected for further evaluation. We then prepared MENDs containing the particles. The lipid composition of the MEND consisted of dioleoylphosphatidyl ethanolamine (DOPE)/phosphatidic acid (PA) (7/2). For cellular uptake and endosomal escape, the MEND was modified with PPD (polyethylene glycol (PEG)-peptide-DOPE), STR-R8 and GALA, pH-sensitive fusogenic peptide. The resulting MEND had a diameter of 120-170 nm and a zeta-potential of 15-25 mV. The MEND was transfected into HeLa cells stably expressing luciferase and the silencing activity of the polycations was compared. Most of the polycations failed to knockdown luciferase activity. However, the polypeptide containing ornithine and tryptophan (Orn/Trp) induced a higher knockdown than STR-R8. In addition, Orn/Trp induced a silencing effect at lower doses than STR-R8, as evidenced by dose-response data. In conclusion, the findings suggest that Orn/Trp is a superior polycation to STR-R8 for siRNA delivery.

Cytosolic targeting of macromolecules using a pH-dependent fusogenic peptide in combination with cationic liposomes

pH-Sensitive peptides and polymers have been employed as additives to enhance the cytosolic delivery of drugs and genes by facilitating their endosomal escape. However, little attention has been paid to the intracellular fate of these peptides and polymers. In this study, we explored the possibility of utilizing GALA, a pH-sensitive fusogenic peptide, as a cytosol-targeting vehicle. In combination with cationic liposomes, Lipofectamine 2000 (LF2000), the feasibility of this approach for the cytosolic targeting of proteins and nanoparticles was exemplified through the delivery of avidin (68 kDa) and streptavidin-coated quantum dots (15-20 nm) in serum-containing medium. The use of cationic liposomes is critical to enhance the cell-surface adhesion of the GALA conjugates and eventual endosomal uptake. Circular dichroism studies suggest that the GALA can be liberated from cationic liposomes at a reducing pH to form a helical structure and this may eventually lead to disruption of the endosomal membrane to achieve an efficient leakage of the GALA conjugates into the cytosol.

Optical imaging of mouse articular cartilage using the glycosaminoglycans binding property of fluorescent-labeled octaarginine

OBJECTIVE

The aim of the current study was to examine the cartilage-specific binding property of polyarginine peptides (R4, 8, 12, and 16) and specifically to test octaarginine peptides for the optical imaging of articular cartilage in experimentally induced arthritis in mice.

METHODS

Four rhodamine-labeled polyarginine peptides each with a different-length arginine chain (R4, 8, 12, or 16) were injected into the knee joints of C57BL/6J mice (n=20). The joints were excised 1h later and the fluorescent signal intensity in cartilage cryosections was compared for the four peptides. To examine the substrate of R8 in cartilage, femoral condyles obtained from another set of mice were treated with chondroitinase ABC (Ch'ase ABC), keratanase or heparitinase then immersed in R8-rhodamine. Fluorescent signals were examined by fluorescent microscopy. Next, R8-rhodamine was injected into the right knee joints of three control and three collagen antibody-induced arthritis (CAIA) mice, and fluorescent intensity in normal and degenerative cartilage was semi-quantitatively analysed on the histological sections using image software. Finally, femoral condyles from normal mice (n=2) and CAIA mice (n=2) were immersed in R8-rhodamine and calcein, then imaged using optical projection tomography (OPT).

RESULTS

Fluorescent signals were specifically detected in the cartilage pericellular matrix from the surface to the tide mark but were completely absent in the calcified layer or bone marrow. The number of arginine residues significantly influenced peptide accumulation in articular cartilage, with R8 accumulating the most. The fluorescent signal in the femoral condylar cartilage diminished when it was treated with Ch'ase ABC. R8 accumulation was significantly decreased in the degenerative cartilage of CAIA mice, and this was demonstrated both histologically and in three-dimensional (3D)-reconstruction image by OPT.

CONCLUSION

R8 may be a useful new experimental probe for optical imaging of normal and arthritic articular cartilage.

Mitochondrial delivery of mastoparan with transferrin liposomes equipped with a pH-sensitive fusogenic peptide for selective cancer therapy

Mastoparan (MP), a potent facilitator of mitochondrial permeability transition (PT), could be used as an antitumor agent, if it were encapsulated in a tumor selective delivery system. We recently developed transferrin-modified liposomes (Tf-L) with a pH-sensitive fusogenic peptide (GALA), which delivers an encapsulated fluorescent marker into cytosol efficiently. In this study, we encapsulated MP into Tf-L with GALA for the selective delivery to mitochondria of tumor cells. The MP showed potent PT activity at concentrations above 25 microM in a homogenate of K 562 cells as well as in isolated mitochondria in the presence of phosphate. Tf-L equipped with cholesteryl GALA can release encapsulated sulforhodamine B, while Tf-L failed, as evidenced by confocal laser scanning microscopy. The MP, which was delivered with Tf-L with GALA, released cytochrome c (cyt c) from mitochondria to the cytosol, while free MP released cyt c not only to the cytosol but also extracellulary. These results demonstrate the utility of MP in Tf-L with GALA for cancer therapy.

Total synthesis of artificial zinc-finger proteins: Problems and perspectives

The total synthesis of a peptide segment corresponding to the DNA-binding segment of Sp1 (positions 532-623) using a native chemical ligation approach is described. The folding of the synthetic segment in the presence of Zn(II) gave a zinc-coordinated protein. The dissociation constant (K(D)) for the DNA binding of the resulting protein, determined by a gel mobility shift assay, was 130 nM, almost nine times higher than that of the genetically prepared protein. However, methylation interference assay showed an identical sequence specificity of both proteins in DNA recognition. The chemical ligation method to connect the respective zinc-finger units was also accomplished. Successive ligation between a cysteine-containing peptide segment and a chloroacetylated peptide segment gave an artificial three-finger protein, which corresponds to the above DNA-binding segment of Sp1. However, this protein failed to bind DNA, even at 1.25 mM. Assessment of their folding structure based on the absorption spectra of their Co(II) complexes showed that the linker design to connect the respective finger units is critical for the proper folding of the proteins as well as the occurrence of the DNA-binding function.

Possible existence of common internalization mechanisms among arginine-rich peptides

Basic peptides such as human immunodeficiency virus type 1 (HIV-1) Tat-(48-60) and Drosophila Antennapedia-(43-58) have been reported to have a membrane permeability and a carrier function for intracellular protein delivery. We have shown that not only Tat-(48-60) but many arginine-rich peptides, including HIV-1 Rev-(34-50) and octaarginine (Arg(8)), efficiently translocated through the cell membranes and worked as protein carriers (Futaki, S., Suzuki, T., Ohashi, W., Yagami, T., Tanaka, S., Ueda, K., and Sugiura, Y. (2001) J. Biol. Chem. 276, 5836-5840). Quantification and time course analyses of the cellular uptake of the above peptides by mouse macrophage RAW264.7, human cervical carcinoma HeLa, and simian kidney COS-7 cells revealed that Rev-(34-50) and Arg(8) had a comparable translocation efficiency to Tat-(48-60). Internalization of Tat-(48-60) and Rev-(34-50) was saturable and inhibited by the excess addition of the other peptide. Typical endocytosis and metabolic inhibitors had little effect on the internalization. The uptake of these peptides was significantly inhibited in the presence of heparan sulfate or chondroitin sulfates A, B, and C. Treatment of the cells with the anti-heparan sulfate antibody or heparinase III also lowered the translocation of these peptides. These results strongly suggest that the arginine-rich basic peptides share a certain part of the internalization pathway.

Surface grafting onto template-assembled synthetic protein scaffolds in molecular recognition

Creating functional biological molecules de novo requires a detailed understanding of the intimate relationship between primary sequence, folding mechanism, and packing topology, and remains up to now a most challenging goal in protein design and mimicry. As a consequence, the use of well-defined robust macromolecules as scaffolds for the introduction of function by grafting surface residues has become a major objective in protein engineering and de novo design. In this article, the concept of scaffolds is demonstrated on some selected examples, illustrating that novel types of functional molecules can be generated. Reengineered proteins and, most notably, de novo designed peptide scaffolds exhibiting molecular function, are ideal tools for structure-function studies and as leads in drug design.

A ‘cassette’ RNase

RNase S is a unique protein comprising the non-covalent association of two components, the S-peptide and the S-protein. An RNA-recognition segment derived from the human immunodeficiency virus (HIV)-1 Rev protein was conjugated with the S-peptide to form a complex with the S-protein. The resulting RNase S bearing the RNA-recognition segment preferentially hydrolyzed a single position of the RNA stem-loop derived from the specific binding site for the Rev protein.

Arginine-rich peptides. An abundant source of membrane-permeable peptides having potential as carriers for intracellular protein delivery

A basic peptide derived from human immunodeficiency virus (HIV)-1 Tat protein (positions 48-60) has been reported to have the ability to translocate through the cell membranes and accumulate in the nucleus, the characteristics of which are utilized for the delivery of exogenous proteins into cells. Based on the fluorescence microscopic observations of mouse macrophage RAW264.7 cells, we found that various arginine-rich peptides have a translocation activity very similar to Tat-(48-60). These included such peptides as the d-amino acid- and arginine-substituted Tat-(48-60), the RNA-binding peptides derived from virus proteins, such as HIV-1 Rev, and flock house virus coat proteins, and the DNA binding segments of leucine zipper proteins, such as cancer-related proteins c-Fos and c-Jun, and the yeast transcription factor GCN4. These segments have no specific primary and secondary structures in common except that they have several arginine residues in the sequences. Moreover, these peptides were able to be internalized even at 4 degrees C. These results strongly suggested the possible existence of a common internalization mechanism ubiquitous to arginine-rich peptides, which is not explained by a typical endocytosis. Using (Arg)(n) (n = 4-16) peptides, we also demonstrated that there would be an optimal number of arginine residues (n approximately 8) for the efficient translocation.

Protein design: on the threshold of functional properties

The ultimate goal in protein de novo design is the creation of novel macromolecules with tailor-made receptor, sensory, and catalytic functions. Despite considerable progress in understanding basic rules of secondary structure formation and protein stability, the well-known protein folding problem is still far from being solved and, in general, only a limited number of designed proteins are folded uniquely. In this article the state-of-the-art in protein design is demonstrated on some selected examples, indicating that the construction of protein-like macromolecules mimicking some essential features of natural proteins seems to be within reach. Thus, protein design and mimicry has become an interdisciplinary challenge with most intriguing perspectives.

Peptide ion channels: design and creation of function

To create ion channel function by synthetic peptides is a challenge in the de novo design of artificial membrane proteins. Amphiphilic alpha-helical motifs of approximately 20 amino acid residues to span lipid bilayers are most often used for the creation of peptide ion channels. Template molecules to tether helical peptides have been employed to obtain more organized pore structures. Approaches to form molecular assembly of peptides in the membranes by hydrogen bonding have been also investigated. We have developed approaches to assemble helices with individual amino acid sequences to construct artificial helical proteins. Using one of these approaches, four helices corresponding to the voltage sensor segments (S4 in repeat I-IV) of the sodium channel were assembled on a peptide template to give a protein having ion channel activity with rectification.

Chemical ligation to obtain proteins comprising helices with individual amino acid sequences

Development of the strategies for assembling multiple kinds of peptide segments would give new possibilities for the de novo design of functional proteins. We will introduce our approach for the selective assembly of helical peptide segments on a peptide template to give four-helix-bundle proteins comprising individual helices.