Protein transduction: unrestricted delivery into all cells?

Computational Insights into Membrane Disruption by Cell-Penetrating Peptides

Cell-penetrating peptides (CPPs) can translocate into cells without inducing cytotoxicity. The internalization process implies several steps at different time scales ranging from microseconds to minutes. We combine adaptive Steered Molecular Dynamics (aSMD) with conventional Molecular Dynamics (cMD) to observe nonequilibrium and equilibrium states to study the early mechanisms of peptide-bilayer interaction leading to CPPs internalization. We define three membrane compositions representing bilayer sections, neutral lipids (i.e., upper leaflet), neutral lipids with cholesterol (i.e., hydrophobic core), and neutral/negatively charged lipids with cholesterol (i.e., lower leaflet) to study the energy barriers and disruption mechanisms of Arg9, MAP, and TP2, representing cationic, amphiphilic, and hydrophobic CPPs, respectively. Cholesterol and negatively charged lipids increase the energetic barriers for the peptide-bilayer crossing. TP2 interacts with the bilayer by hydrophobic insertion, while Arg9 disrupts the bilayer by forming transient or stable pores. MAP has shown both behaviors. Collectively, these findings underscore the significance of innovative computational approaches in studying membrane-disruptive peptides and, more specifically, in harnessing their potential for cell penetration.

Current developments and prospects of the antibiotic delivery systems

Antibiotics have remained the cornerstone for the treatment of bacterial infections ever since their discovery in the twentieth century. The uproar over antibiotic resistance among bacteria arising from genome plasticity and biofilm development has rendered current antibiotic therapies ineffective, urging the development of innovative therapeutic approaches. The development of antibiotic resistance among bacteria has further heightened the clinical failure of antibiotic therapy, which is often linked to its low bioavailability, side effects, and poor penetration and accumulation at the site of infection. In this review, we highlight the potential use of siderophores, antibodies, cell-penetrating peptides, antimicrobial peptides, bacteriophages, and nanoparticles to smuggle antibiotics across impermeable biological membranes to achieve therapeutically relevant concentrations of antibiotics and combat antimicrobial resistance (AMR). We will discuss the general mechanisms via which each delivery system functions and how it can be tailored to deliver antibiotics against the paradigm of mechanisms underlying antibiotic resistance.

Cyclized proteins with tags as permeable and stable cargos for delivery into cells and liposomes

Despite the therapeutic potential of recombinant proteins, their cell permeabilities and stabilities remain significant challenges. Here we demonstrate that cyclized recombinant proteins can be used as universal cargos for permeable and stable delivery into cells and polydiacetylene liposomes. Utilizing a split intein-mediated process, cyclized model fluorescent proteins containing short tetraarginine (R4) and hexahistidine (H6) tags were generated without compromising their native protein functions. Strikingly, as compared to linear R4/H6-tagged proteins, the cyclized counterparts have substantially increased permeabilities in both cancer cells and synthetic liposomes, as well as higher resistances to enzymatic degradation in cancer cells. These properties are likely a consequence of structural constraints imposed on the proteins in the presence of short functional peptides. Additionally, photodynamic therapy by cyclized photoprotein-loaded liposomes in cancer cells was significantly improved in comparison to that by their non-cyclized counterparts. These findings suggest that our strategy will be universally applicable to intercellular delivery of proteins and therapeutics.

Orbivirus NS4 Proteins Play Multiple Roles to Dampen Cellular Responses

Non-structural protein 4 (NS4) of insect-borne and tick-borne orbiviruses is encoded by genome segment 9, from a secondary open reading frame. Though a protein dispensable for bluetongue virus (BTV) replication, it has been shown to counter the interferon response in cells infected with BTV or African horse sickness virus. We further explored the functional role(s) of NS4 proteins of BTV and the tick-borne Great Island virus (GIV). We show that NS4 of BTV or GIV helps an E3L deletion mutant of vaccinia virus to replicate efficiently in interferon-treated cells, further confirming the role of NS4 as an interferon antagonist. Our results indicate that ectopically expressed NS4 of BTV localised with caspase 3 within the nucleus and was found in a protein complex with active caspase 3 in a pull-down assay. Previous studies have shown that pro-apoptotic caspases (including caspase 3) suppress type I interferon response by cleaving mediators involved in interferon signalling. Our data suggest that orbivirus NS4 plays a role in modulating the apoptotic process and/or regulating the interferon response in mammalian cells, thus acting as a virulence factor in pathogenesis.

Fluorescent Guanidinium-Azacarbazole for Oxoanion Binding in Water

Oxoanions such as carboxylates, phosphates, and sulfates play important roles in both chemistry and biology and are abundant on the cell surface. We report on the synthesis and properties of a rationally designed guanidinium-containing oxoanion binder, 1-guanidino-8-amino-2,7-diazacarbazole (GADAC). GADAC binds to a carboxylate, phosphate, and sulfate in pure water with affinities of 3.6 × 104, 1.1 × 103, and 4.2 × 103 M-1, respectively. Like 2-azacarbazole, which is a natural product that enables scorpions to fluoresce, GADAC is fluorescent in water (λabs = 356 nm, λem = 403 nm, ε = 13,400 M-1 cm-1). The quantum yield of GADAC is pH-sensitive, increasing from Φ = 0.12 at pH 7.4 to Φ = 0.53 at pH 4.0 as a result of the protonation of the aminopyridine moiety. The uptake of GADAC into live human melanoma cells is detectable in the DAPI channel at low micromolar concentrations. Its properties make GADAC a promising candidate for applications in oxoanion binding and fluorescence labeling in biological (e.g., the delivery of cargo into cells) and other contexts.

Antiviral Peptide-Based Conjugates: State of the Art and Future Perspectives

Infectious diseases caused by microbial pathogens (bacteria, virus, fungi, parasites) claim millions of deaths per year worldwide and have become a serious challenge to global human health in our century. Viral infections are particularly notable in this regard, not only because humankind is facing some of the deadliest viral pandemics in recent history, but also because the arsenal of drugs to combat the high levels of mutation, and hence the antigenic variability of (mostly RNA) viruses, is disturbingly scarce. Therefore, the search for new antivirals able to successfully fight infection with minimal or no adverse effects on the host is a pressing task. Traditionally, antiviral therapies have relied on relatively small-sized drugs acting as proteases, polymerases, integrase inhibitors, etc. In recent decades, novel approaches involving targeted delivery such as that achieved by peptide-drug conjugates (PDCs) have gained attention as alternative (pro)drugs for tackling viral diseases. Antiviral PDC therapeutics typically involve one or more small drug molecules conjugated to a cell-penetrating peptide (CPP) carrier either directly or through a linker. Such integration of two bioactive elements into a single molecular entity is primarily aimed at achieving improved bioavailability in conditions where conventional drugs are challenged, but may also turn up novel unexpected functionalities and applications. Advances in peptide medicinal chemistry have eased the way to antiviral PDCs, but challenges remain on the way to therapeutic success. In this paper, we review current antiviral CPP-drug conjugates (antiviral PDCs), with emphasis on the types of CPP and antiviral cargo. We integrate the conjugate and the chemical approaches most often applied to combine both entities. Additionally, we comment on various obstacles faced in the design of antiviral PDCs and on the future outlooks for this class of antiviral therapeutics.

B-cell Lymphoma 6 Inhibitors: Current Advances and Prospects of Drug Development for Diffuse Large B-cell Lymphomas

B-cell lymphoma 6 (BCL6) is a transcriptional repressor that regulates the differentiation of B lymphocytes and mediates the formation of germinal centers (GCs) by recruiting corepressors through the BTB domain of BCL6. Physiological processes regulated by BCL6 involve cell activation, differentiation, DNA damage, and apoptosis. BCL6 is highly expressed when the gene is mutated, leading to the malignant proliferation of cells and drives tumorigenesis. BCL6 overexpression is closely correlated with tumorigenesis in diffuse large B-cell lymphoma (DLBCL) and other lymphomas, and BCL6 inhibitors can effectively inhibit some lymphomas and overcome resistance. Therefore, targeting BCL6 might be a promising therapeutic strategy for treating lymphomas. Herein, we comprehensively review the latest development of BCL6 inhibitors in diffuse large B-cell lymphoma and discuss the overview of the pharmacophores of BCL6 inhibitors and their efficacies in vitro and in vivo. Additionally, the current advances in BCL6 degraders are provided.

Strategies for Improving Peptide Stability and Delivery

Peptides play an important role in many fields, including immunology, medical diagnostics, and drug discovery, due to their high specificity and positive safety profile. However, for their delivery as active pharmaceutical ingredients, delivery vectors, or diagnostic imaging molecules, they suffer from two serious shortcomings: their poor metabolic stability and short half-life. Major research efforts are being invested to tackle those drawbacks, where structural modifications and novel delivery tactics have been developed to boost their ability to reach their targets as fully functional species. The benefit of selected technologies for enhancing the resistance of peptides against enzymatic degradation pathways and maximizing their therapeutic impact are also reviewed. Special note of cell-penetrating peptides as delivery vectors, as well as stapled modified peptides, which have demonstrated superior stability from their parent peptides, are reported.

Enhanced efficiency of generating human-induced pluripotent stem cells using Lin28-30Kc19 fusion protein

Induced pluripotent stem cells (iPSCs) have intrinsic properties, such as self-renewal ability and pluripotency, which are also shown in embryonic stem cells (ESCs). The challenge of improving the iPSC generation efficiency has been an important issue and there have been many attempts to develop iPSC generation methods. In this research, we added Lin28, known as one of the reprogramming factors, in the form of a soluble recombinant protein from E. coli to improve the efficiency of human iPSC (hiPSC) generation, in respect of alkaline phosphatase (AP)-positive colonies. To deliver Lin28 inside the cells, we generated a soluble Lin28-30Kc19 fusion protein, with 30Kc19 at the C-terminal domain of Lin28. 30Kc19, a silkworm hemolymph-derived protein, was fused due to its cell-penetrating and protein-stabilizing properties. The Lin28-30Kc19 was treated to human dermal fibroblasts (HDFs), in combination with four defined reprogramming factors (Oct4, Sox2, c-Myc, and Klf4). After 14 days of cell culture, we confirmed the generated hiPSCs through AP staining. According to the results, the addition of Lin28-30Kc19 increased the number and size of generated AP-positive hiPSC colonies. Through this research, we anticipate that this recombinant protein would be a valuable material for increasing the efficiency of hiPSC generation and for enhancing the possibility as a substitute of the conventional method.

Canavanine versus arginine: Prospects for cell-penetrating peptides

Octanol-water partitioning experiments in the presence of carboxylate-, phosphate-, and sulfate-containing anionic lipids revealed that Ac-Cav-NH2 (where Cav refers to δ-oxa-arginine) partitions less into octanol than does Ac-Arg-NH2, suggesting that a cell-penetrating peptide based on canavanine would be relatively ineffective.

Structural analysis of TrkA mutations in patients with congenital insensitivity to pain reveals PLCγ as an analgesic drug target

Chronic pain is a major health issue, and the search for new analgesics has become increasingly important because of the addictive properties and unwanted side effects of opioids. To explore potentially new drug targets, we investigated mutations in the NTRK1 gene found in individuals with congenital insensitivity to pain with anhidrosis (CIPA). NTRK1 encodes tropomyosin receptor kinase A (TrkA), the receptor for nerve growth factor (NGF) and that contributes to nociception. Molecular modeling and biochemical analysis identified mutations that decreased the interaction between TrkA and one of its substrates and signaling effectors, phospholipase Cγ (PLCγ). We developed a cell-permeable phosphopeptide derived from TrkA (TAT-pQYP) that bound the Src homology domain 2 (SH2) of PLCγ. In HEK-293T cells, TAT-pQYP inhibited the binding of heterologously expressed TrkA to PLCγ and decreased NGF-induced, TrkA-mediated PLCγ activation and signaling. In mice, intraplantar administration of TAT-pQYP decreased mechanical sensitivity in an inflammatory pain model, suggesting that targeting this interaction may be analgesic. The findings demonstrate a strategy to identify new targets for pain relief by analyzing the signaling pathways that are perturbed in CIPA.

HIV-1 Establishes a Sanctuary Site in the Testis by Permeating the BTB Through Changes in Cytoskeletal Organization

Studies suggest that HIV-1 invades the testis through initial permeation of the blood-testis barrier (BTB). The selectivity of the BTB to antiretroviral drugs makes this site a sanctuary for the virus. Little is known about how HIV-1 crosses the BTB and invades the testis. Herein, we used 2 approaches to examine the underlying mechanism(s) by which HIV-1 permeates the BTB and gains entry into the seminiferous epithelium. First, we examined if recombinant Tat protein was capable of perturbing the BTB and making the barrier leaky, using the primary rat Sertoli cell in vitro model that mimics the BTB in vivo. Second, we used HIV-1-infected Sup-T1 cells to investigate the activity of HIV-1 infection on cocultured Sertoli cells. Using both approaches, we found that the Sertoli cell tight junction permeability barrier was considerably perturbed and that HIV-1 effectively permeates the BTB by inducing actin-, microtubule-, vimentin-, and septin-based cytoskeletal changes in Sertoli cells. These studies suggest that HIV-1 directly perturbs BTB function, potentially through the activity of the Tat protein.

Improving the Cellular Uptake of Biomimetic Magnetic Nanoparticles

Magnetococcus marinus magnetosome-associated protein MamC, expressed as recombinant, has been proven to mediate the formation of novel biomimetic magnetic nanoparticles (BMNPs) that are successful drug nanocarriers for targeted chemotherapy and hyperthermia agents. These BMNPs present several advantages over inorganic magnetic nanoparticles, such as larger sizes that allow the former to have larger magnetic moment per particle, and an isoelectric point at acidic pH values, which allows both the stable functionalization of BMNPs at physiological pH value and the molecule release at acidic (tumor) environments, simply based on electrostatic interactions. However, difficulties for BMNPs cell internalization still hold back the efficiency of these nanoparticles as drug nanocarriers and hyperthermia agents. In the present study we explore the enhanced BMNPs internalization following upon their encapsulation by poly (lactic-co-glycolic) acid (PLGA), a Food and Drug Administration (FDA) approved molecule. Internalization is further optimized by the functionalization of the nanoformulation with the cell-penetrating TAT peptide (TATp). Our results evidence that cells treated with the nanoformulation [TAT-PLGA(BMNPs)] show up to 80% more iron internalized (after 72 h) compared to that of cells treated with BMNPs (40%), without any significant decrease in cell viability. This nanoformulation showing optimal internalization is further characterized. In particular, the present manuscript demonstrates that neither its magnetic properties nor its performance as a hyperthermia agent are significantly altered due to the encapsulation. In vitro experiments demonstrate that, following upon the application of an alternating magnetic field on U87MG cells treated with BMNPs and TAT-PLGA(BMNPs), the cytotoxic effect of BMNPs was not affected by the TAT-PLGA enveloping. Based on that, difficulties shown in previous studies related to poor cell uptake of BMNPs can be overcome by the novel nanoassembly described here.

Targeting transcriptional coregulator OCA-B/Pou2af1 blocks activated autoreactive T cells in the pancreas and type 1 diabetes

The transcriptional coregulator OCA-B promotes expression of T cell target genes in cases of repeated antigen exposure, a necessary feature of autoimmunity. We hypothesized that T cell-specific OCA-B deletion and pharmacologic OCA-B inhibition would protect mice from autoimmune diabetes. We developed an Ocab conditional allele and backcrossed it onto a diabetes-prone NOD/ShiLtJ strain background. T cell-specific OCA-B loss protected mice from spontaneous disease. Protection was associated with large reductions in islet CD8+ T cell receptor specificities associated with diabetes pathogenesis. CD4+ clones associated with diabetes were present but associated with anergic phenotypes. The protective effect of OCA-B loss was recapitulated using autoantigen-specific NY8.3 mice but diminished in monoclonal models specific to artificial or neoantigens. Rationally designed membrane-penetrating OCA-B peptide inhibitors normalized glucose levels and reduced T cell infiltration and proinflammatory cytokine expression in newly diabetic NOD mice. Together, the results indicate that OCA-B is a potent autoimmune regulator and a promising target for pharmacologic inhibition.

Polyphenol-Based Nanoparticles for Intracellular Protein Delivery via Competing Supramolecular Interactions

Intracellular delivery of proteins is a promising strategy for regulating cellular behavior and therefore has attracted interest for biomedical applications. Despite the emergence of various nanoparticle-based intracellular delivery approaches, it remains challenging to engineer a versatile delivery system capable of responding to various physiological triggers without the need for complex chemical synthesis of the delivery system. Herein, we develop a template-mediated supramolecular assembly strategy to synthesize protein-polyphenol nanoparticles (NPs) capable of endosomal escape and subsequent protein release in the cytosol. These NPs are stable in serum and undergo surface charge reversal from negative to positive in acidic environments, leading to spontaneous endosomal escape. In the cytosol, endogenous small peptides and amino acids with relatively high charge densities, such as glutathione, trigger NP disassembly through competitive supramolecular interactions, thereby releasing functional bioactive proteins, as validated using cytochrome C and β-galactosidase. The versatility of the present strategy in terms of nanoparticle size, protein type, and functional protein delivery makes this a promising platform for potential application in the field of protein therapeutics.

Silencing of HIF-1α/CD73 axis by siRNA-loaded TAT-chitosan-spion nanoparticles robustly blocks cancer cell progression

Induction of Hypoxia Inducible Factor (HIF) as a direct consequence of oxygen deficiency in tumor tissues is a potent stimulus of CD73 (ecto-5'-nucleotidase) expression. Hypoxic environment and CD73 overexpression are associated with altered metabolism, elevated cancer cell proliferation, and tumor vascularization. Herein, a delivery system was developed for silencing CD73 and HIF-1α gene using siRNA-loaded Superparamagnetic iron oxide (SPION) nanocarriers for cancer treatment. SPIONs were encapsulated with thiolated chitosan (TC) and trimethyl chitosan (TMC) for improving their stabilization and functionalization. The nanoparticles (NPs) were about 133 nm in size, spherical, and non-toxic, and the addition of TAT peptide (derived from HIV-1 TAT protein) to TMC-TC-SPIONs significantly increased their cellular uptake by cancer cells. The produced NPs could efficiently accumulate in the tumor site, indicating their stability and targeting ability in reaching the tumor region. TAT-conjugated TMC-TC-SPIONs containing siRNAs could significantly reduce the HIF-1α and CD73 expression levels in cancer cells. Following transfection, cancer cells showed a significant reduction in migration and proliferation. Moreover, siRNA-loaded NPs could effectively reduce tumor growth and angiogenesis, as investigated by the chick chorioallantoic membrane (CAM) assay. This study suggested that TAT-TMC-TC-SPIONs can be potential nanocarrier for gene transfection in cancer therapy. Moreover, the co-silencing of CD73 and HIF-1α can be assumed as a novel anti-cancer treatment strategy with high tumor suppression potential.

Role of Divalent Cations in HIV-1 Replication and Pathogenicity

Divalent cations are essential for life and are fundamentally important coordinators of cellular metabolism, cell growth, host-pathogen interactions, and cell death. Specifically, for human immunodeficiency virus type-1 (HIV-1), divalent cations are required for interactions between viral and host factors that govern HIV-1 replication and pathogenicity. Homeostatic regulation of divalent cations' levels and actions appear to change as HIV-1 infection progresses and as changes occur between HIV-1 and the host. In people living with HIV-1, dietary supplementation with divalent cations may increase HIV-1 replication, whereas cation chelation may suppress HIV-1 replication and decrease disease progression. Here, we review literature on the roles of zinc (Zn2+), iron (Fe2+), manganese (Mn2+), magnesium (Mg2+), selenium (Se2+), and copper (Cu2+) in HIV-1 replication and pathogenicity, as well as evidence that divalent cation levels and actions may be targeted therapeutically in people living with HIV-1.

New Peptide-Based Pharmacophore Activates 20S Proteasome

The proteasome is a pivotal element of controlled proteolysis, responsible for the catabolic arm of proteostasis. By inducing apoptosis, small molecule inhibitors of proteasome peptidolytic activities are successfully utilized in treatment of blood cancers. However, the clinical potential of proteasome activation remains relatively unexplored. In this work, we introduce short TAT peptides derived from HIV-1 Tat protein and modified with synthetic turn-stabilizing residues as proteasome agonists. Molecular docking and biochemical studies point to the α1/α2 pocket of the core proteasome α ring as the binding site of TAT peptides. We postulate that the TATs' pharmacophore consists of an N-terminal basic pocket-docking "activation anchor" connected via a β turn inducer to a C-terminal "specificity clamp" that binds on the proteasome α surface. By allosteric effects-including destabilization of the proteasomal gate-the compounds substantially augment activity of the core proteasome in vitro. Significantly, this activation is preserved in the lysates of cultured cells treated with the compounds. We propose that the proteasome-stimulating TAT pharmacophore provides an attractive lead for future clinical use.

Peptides derived from the C-terminal domain of HIV-1 Viral Protein R in lipid bilayers: Structure, membrane positioning and gene delivery

Viral protein R (Vpr) is a small accessory protein of 96 amino acids that is present in Human and simian immunodeficiency viruses. Among the very different properties that Vpr possesses we can find cell penetrating capabilities. Based on this and on its capacity to interact with nucleic acids we previously investigated the DNA transfection properties of Vpr and subfragments thereof. We found that fragments of the C-terminal helical domain of Vpr are able to deliver efficiently plasmid DNA into different cell lines. As the amphipathic helix may play a role in the interactions with membranes, we investigated whether insertion of a proline residue in the α-helix modifies the transfection properties of Vpr. Unexpectedly, we found that the resulting Vpr55-82 Pro70 peptide was even more efficient than wild type Vpr55-82 in the gene delivery assays. Using circular dichroism, light scattering and solid-state NMR techniques, we characterized the secondary structure and interactions of Vpr and several mutants with model membranes. A model is proposed where the proline shifts the dissociation equilibrium of the peptide-cargo complex and thereby its endosomal release.

Single enzyme nanoparticle, an effective tool for enzyme replacement therapy

The term "single enzyme nanoparticle" (SEN) refers to a chemically or biologically engineered single enzyme molecule. SENs are distinguished from conventional protein nanoparticles in that they can maintain their individual structure and enzymatic activity following modification. Furthermore, SENs exhibit enhanced properties as biopharmaceuticals, such as reduced antigenicity, and increased stability and targetability, which are attributed to the introduction of specific moieties, such as poly(ethylene glycol), carbohydrates, and antibodies. Enzyme replacement therapy (ERT) is a crucial therapeutic option for controlling enzyme-deficiency-related disorders. However, the unfavorable properties of enzymes, including immunogenicity, lack of targetability, and instability, can undermine the clinical significance of ERT. As shown in the cases of Adagen®, Revcovi®, Palynziq®, and Strensiq®, SEN can be an effective technology for overcoming these obstacles. Based on these four licensed products, we expect that additional SENs will be introduced for ERT in the near future. In this article, we review the concepts and features of SENs, as well as their preparation methods. Additionally, we summarize different types of enzyme deficiency disorders and the corresponding therapeutic enzymes. Finally, we focus on the current status of SENs in ERT by reviewing FDA-approved products.

Optimization of formulation for enhanced intranasal delivery of insulin with translationally controlled tumor protein-derived protein transduction domain

Intranasal delivery of insulin is an alternative approach to treat diabetes, as it enables higher patient compliance than conventional therapy with subcutaneously injected insulin. However, the use of intranasal delivery of insulin is limited for insulin’s hydrophilicity and vulnerability to enzymatic degradation. This limitation makes optimization of formulation intranasal insulin for commercial purpose indispensable. This study evaluated bioavailability (BA) of various formulations of insulin intranasally delivered with protein transduction domain (PTD) derived from translationally controlled tumor protein. The therapeutic efficacy of newly formulated intranasal insulin + PTD was compared in vivo studies with normal and alloxan-induced diabetic rats, to those of free insulin and subcutaneously injected insulin. BA of insulin in two new formulations was, respectively, 60.71% and 45.81% of subcutaneously injected insulin, while the BA of free insulin was only 3.34%. Histological analysis of tissues, lactate dehydrogenase activity in nasal fluid, and biochemical analysis of sera revealed no detectable topical or systemic toxicity in rats and mice. Furthermore, stability analysis of newly formulated insulin + PTD to determine the optimal conditions for storage revealed that when stored at 4 °C, the delivery capacity of insulin was maintained up to 7 d. These results suggest that the new formulations of intranasal insulin are suitable for use in diabetes therapy and are easier to administer.

α-Helical cell-penetrating peptide-mediated nasal delivery of resveratrol for inhibition of epithelial-to-mesenchymal transition

In the present study, we examined the potential of cell-penetrating peptide (CPP)-based intranasal drug delivery for the treatment of localized nasal diseases. Many charged or non-hydrophobic drugs have difficulty penetrating into the nasal epithelium due to intrinsic membrane impermeability and rapid mucociliary clearance in the nasal cavity. To treat chronic rhinosinusitis with nasal polyps (CRSwNP), one of the most common localized nasal diseases, we conjugated resveratrol (RSV) to an amphiphilic α-helical leucine (L)- and lysine (K)-rich CPP (LK) and intranasally delivered it to the interior of nasal epithelial cells for inhibiting epithelial-to-mesenchymal transition (EMT) caused by hypoxia-inducible factor 1α. The RSV-LK conjugate could penetrate into the nasal epithelium and efficiently inhibit EMT, nasal polyp formation, epithelial disruption, and related inflammation in an eosinophilic CRSwNP mouse model, at 10-fold lower doses and with 3-fold less frequent administration than free RSV. Due to the rapid penetration into the nasal epithelium and the therapeutic effect of the RSV-LK conjugate at much lower doses than free RSV, this CPP-based delivery system, with the ability to overcome the tight nasal epithelial barrier, may provide a new strategy for the treatment of localized nasal diseases without the systemic side effects of cargo drugs.

DNA/Lysozyme-binding affinity study of novel peptides from TAT (47-57) and BRCA1 (782-786) in vitro by spectroscopic analysis

SISLL-TAT and TAT-SISLL were synthesized by modifying the N- or C-termini of cell-penetrating peptides as transacting activator of transcription TAT (47-57) by attaching BRCA1 (782-786) (SISLL). The novel peptides were synthesized through Fmoc solid-phase synthesis procedures and characterized by LCQ Fleet MS, ¹H NMR and ¹³C NMR. SISLL-TAT and TAT-SISLL displayed forceful antibacterial activities against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Salmonella typhimurium with low hemolysis. SISLL-TAT showed better antibacterial activity than TAT-SISLL, with the minimum inhibitory concentration (MIC) values of 10-33 μg·mL^-1. The results of the DNA-binding activities showed that both SISLL-TAT and TAT-SISLL could interact with DNA via the minor groove mode, and the binding constants were 4.97 × 10⁵ L·mol^-1 and 4.42 × 10⁵ L·mol^-1 at 310 K, respectively. Circular dichroism analysis showed slight transformation of the lysozyme secondary structure caused by SISLL-TAT and TAT-SISLL. We also found that the novel peptides SISLL-TAT and TAT-SISLL targeted bacterial DNA resulting in cell death. This explains the antibacterial mechanism of SISLL-TAT and TAT-SISLL, and is a solid theoretical basis for further designing novel and highly effective antibiotics for clinical application.

Immunogenicity and Efficacy of a Novel Multi-Antigenic Peptide Vaccine Based on Cross-Reactivity between Feline and Human Immunodeficiency Viruses

For the development of an effective HIV-1 vaccine, evolutionarily conserved epitopes between feline and human immunodeficiency viruses (FIV and HIV-1) were determined by analyzing overlapping peptides from retroviral genomes that induced both anti-FIV/HIV T cell-immunity in the peripheral blood mononuclear cells from the FIV-vaccinated cats and the HIV-infected humans. The conserved T-cell epitopes on p24 and reverse transcriptase were selected based on their robust FIV/HIV-specific CD8⁺ cytotoxic T lymphocyte (CTL), CD4⁺ CTL, and polyfunctional T-cell activities. Four such evolutionarily conserved epitopes were formulated into four multiple antigen peptides (MAPs), mixed with an adjuvant, to be tested as FIV vaccine in cats. The immunogenicity and protective efficacy were evaluated against a pathogenic FIV. More MAP/peptide-specific CD4⁺ than CD8⁺ T-cell responses were initially observed. By post-third vaccination, half of the MAP/peptide-specific CD8⁺ T-cell responses were higher or equivalent to those of CD4⁺ T-cell responses. Upon challenge, 15/19 (78.9%) vaccinated cats were protected, whereas 6/16 (37.5%) control cats remained uninfected, resulting in a protection rate of 66.3% preventable fraction (p = 0.0180). Thus, the selection method used to identify the protective FIV peptides should be useful in identifying protective HIV-1 peptides needed for a highly protective HIV-1 vaccine in humans.

Human immunodeficiency virus Tat-TIP30 interaction promotes metastasis by enhancing the nuclear translocation of Snail in lung cancer cell lines

Lung cancer patients with human immunodeficiency virus (HIV) have a poorer prognosis than do patients without HIV infection. HIV1 Tat is a secreted viral protein that penetrates the plasma membrane and interacts with a number of proteins in non‐HIV‐infected cells. The loss of function of Tat‐interacting protein 30 (TIP30) has been linked to metastasis in non‐small cell lung cancer (NSCLC). However, it is unknown how the interaction of HIV1 Tat with TIP30 regulates the metastasis of NSCLC cells. In this study, the overexpression of TIP30 decreased tumor growth factor‐β‐induced epithelial‐to‐mesenchymal transition (EMT) and invasion of NSCLC cells, whereas the knockdown of TIP30 promoted EMT, invasion and stemness. Exposure to recombinant HIV1 Tat proteins promoted EMT and invasion. A mechanistic study showed that the interaction of HIV1 Tat with TIP30 blocked the binding of TIP30 to importin‐β, which is required for the nuclear translocation of Snail. Indeed, the loss of TIP30 promoted the nuclear translocation of Snail. In vivo studies demonstrated that the overexpression of TIP30 inhibited the metastasis of NSCLC cells. In contrast, the coexpression of HIV1 Tat and TIP30 diminished the inhibitory effect of TIP30 on metastasis. Immunohistochemistry confirmed that TIP30 overexpression reduced the nuclear localization of Snail, whereas the coexpression of HIV1 Tat and TIP30 increased nuclear Snail in metastatic tumors. In conclusion, the binding of HIV1 Tat to TIP30 enhanced EMT and metastasis by regulating the nuclear translocation of Snail. Targeting Tat‐interacting proteins may be a potential therapeutic strategy to prevent metastasis in NSCLC patients with HIV infection.

Cell-penetrating artificial mitochondria-targeting peptide-conjugated metallothionein 1A alleviates mitochondrial damage in Parkinson's disease models

An excess of reactive oxygen species (ROS) relative to the antioxidant capacity causes oxidative stress, which plays a role in the development of Parkinson’s disease (PD). Because mitochondria are both sites of ROS generation and targets of ROS damage, the delivery of antioxidants to mitochondria might prevent or alleviate PD. To transduce the antioxidant protein human metallothionein 1A (hMT1A) into mitochondria, we computationally designed a cell-penetrating artificial mitochondria-targeting peptide (CAMP). The recombinant CAMP-conjugated hMT1A fusion protein (CAMP-hMT1A) successfully localized to the mitochondria. Treating a cell culture model of PD with CAMP-hMT1A restored tyrosine hydroxylase expression and mitochondrial activity and reduced ROS production. Furthermore, injection of CAMP-hMT1A into the brain of a mouse model of PD rescued movement impairment and dopaminergic neuronal degeneration. CAMP-hMT1A delivery into mitochondria might be therapeutic against PD by alleviating mitochondrial damage, and we predict that CAMP could be used to deliver other cargo proteins to the mitochondria.

A peptide targeting mitochondria can help deliver an antioxidant protein to mitigate the effects of Parkinson’s disease in cellular and mouse models. Youngmi Pak from Kyung Hee University, Seoul, South Korea, and co-workers engineered bacteria to express the human version of an antioxidant protein called metallothionein 1A fused to a short peptide sequence so that it localizes to mitochondria, the cellular power plants. Once inside the mitochondria, the peptide is removed, leaving the mature antioxidant protein to mop up damaging free radicals, a common problem seen in the cells of patients with Parkinson’s disease, and restore mitochondria to a healthier state. The protein improved mitochondrial function in both a human cell line and in the neurons of mice with a Parkinson’s-like disease, suggesting it might also help patients with this devastating neurological condition.

Global Perspective of Novel Therapeutic Strategies for the Management of NeuroAIDS

Among Human immunodeficiency virus (HIV) infected individuals, around two-thirds of patients present with neuroAIDS, where HIV-associated neurocognitive disorders (HAND), and HIV-associated dementia (HAD) are the most prevailing neurological complications. The neuropathology of neuroAIDS can be characterized by the presence of HIV infected macrophages and microglia in the brain, with the formation of multinucleated giant cells. Global predominant subtypes of HIV-1 clade B and C infections influence the differential effect of immune and neuronal dysfunctions, leading to clade-specific clinical variation in neuroAIDS patient cohorts. Highly active antiretroviral therapy (HAART) enhances the survival rate among AIDS patients, but due to the inability to cross the Blood-Brain-Barrier (BBB), incidence of neuroAIDS during disease progression may be envisaged. The complex structure of blood-brain-barrier, and poor pharmacokinetic profile coupled with weak bio-distribution of antiretroviral drugs, are the principle barriers for the treatment of neuroAIDS. In the combined antiretroviral therapy (cART) era, the frequency of HAD has decreased; however the incidence of asymptomatic neurocognitive impairment (ANI) and minor neurocognitive disorder (MND) remains consistent. Therefore, several effective novel nanotechnology based therapeutic approaches have been developed to improve the availability of antiretroviral drugs in the brain for the management of neuroAIDS.

Cell penetrating peptide modulation of membrane biomechanics by Molecular dynamics

The efficacy of a pharmaceutical treatment is often countered by the inadequate membrane permeability, that prevents drugs from reaching their specific intracellular targets. Cell penetrating peptides (CPPs) are able to route across cells' membrane various types of cargo, including drugs and nanoparticles. However, CPPs internalization mechanisms are not yet fully understood and depend on a wide variety of aspects. In this contest, the entry of a CPP into the lipid bilayer might induce molecular conformational changes, including marked variations on membrane's mechanical properties. Understanding how the CPP does influence the mechanical properties of cells membrane is crucial to design, engineer and improve new and existing penetrating peptides. Here, all atom Molecular Dynamics (MD) simulations were used to investigate the interaction between different types of CPPs embedded in a lipid bilayer of dioleoyl phosphatidylcholine (DOPC). In a greater detail, we systematically highlighted how CPP properties are responsible for modulating the membrane bending modulus. Our findings highlighted the CPP hydropathy strongly correlated with penetration of water molecules in the lipid bilayer, thus supporting the hypothesis that the amount of water each CPP can route inside the membrane is modulated by the hydrophobic and hydrophilic character of the peptide. Water penetration promoted by CPPs leads to a local decrease of the lipid order, which emerges macroscopically as a reduction of the membrane bending modulus.

Tat is a multifunctional viral protein that modulates cellular gene expression and functions

The human immunodeficiency virus type I (HIV-1) has developed several strategies to condition the host environment to promote viral replication and spread. Viral proteins have evolved to perform multiple functions, aiding in the replication of the viral genome and modulating the cellular response to the infection. Tat is a small, versatile, viral protein that controls transcription of the HIV genome, regulates cellular gene expression and generates a permissive environment for viral replication by altering the immune response and facilitating viral spread to multiple tissues. Studies carried out utilizing biochemical, cellular, and genomic approaches show that the expression and activity of hundreds of genes and multiple molecular networks are modulated by Tat via multiple mechanisms.

Smart Cell-Penetrating Peptide-Based Techniques for Intracellular Delivery of Therapeutic Macromolecules

Many therapeutic macromolecules must enter cells to take their action. However, their treatment outcomes are often hampered by their poor transportation into target cells. Therefore, efficient intracellular delivery of these macromolecules is critical for improving their therapeutic efficacy. Cell-penetrating peptide (CPP)-based approaches are one of the most efficient methods for intracellular delivery of macromolecular therapeutics. Nevertheless, poor specificity is a significant concern for systemic administrated CPP-based delivery systems. This chapter will review recent advances in CPP-mediated macromolecule delivery with a focus on various smart strategies which not only enhance the intracellular delivery but also improve the targeting specificity.

A cell-penetrating whole molecule antibody targeting intracellular HBx suppresses hepatitis B virus via TRIM21-dependent pathway

Rationale: Monoclonal antibodies (mAbs) mostly targeting extracellular or cell surface molecules have been widely used in the treatment of various diseases. However, mAbs cannot pass through the cell membrane as efficiently as small compounds, thus limiting their use against intracellular targets. Methods to shuttle antibodies into living cells may largely expand research and application in areas based on mAbs. Hepatitis B virus X protein (HBx) is an important intracellular multi-functional viral protein in the life cycle of hepatitis B virus (HBV). HBx plays essential roles in virus infection and replication and is strongly associated with HBV-related carcinogenesis.

Methods: In this study, we developed a cell-penetrating whole molecule antibody targeting HBx (9D11-Tat) by the fusion of a cell penetrating peptide (CPP) on the C-terminus of the heavy chain of a potent mAb specific to HBx (9D11). The anti-HBV effect and mechanism of 9D11-Tat were investigated in cell and mouse models mimicking chronic HBV infection.

Results: Our results demonstrated that the recombinant 9D11-Tat antibody could efficiently internalize into living cells and significantly suppress viral transcription, replication, and protein production both in vitro and in vivo. Further analyses suggested the internalized 9D11-Tat antibody could greatly reduce intracellular HBx via Fc binding receptor TRIM21-mediated protein degradation. This process simultaneously stimulated the activations of NF-κB, AP-1, and IFN-β, which promoted an antiviral state of the host cell.

Conclusion: In summary, our study offers a new approach to target intracellular pathogenesis-related protein by engineered cell-penetrating mAb expanding their potential for therapeutic applications. Moreover, the 9D11-Tat antibody may provide a novel therapeutic agent against human chronic HBV infection.

High efficiency and long-term intracellular activity of an enzymatic nanofactory based on metal-organic frameworks

Enhancing or restoring enzymatic function in cells is highly desirable in applications ranging from ex vivo cellular manipulations to enzyme replacement therapies in humans. However, because enzymes degrade in biological milieus, achieving long-term enzymatic activities can be challenging. Herein we report on the in cellulo properties of nanofactories that consist of antioxidative enzymes encapsulated in metal-organic frameworks (MOFs). We demonstrate that, while free enzymes display weak activities for only a short duration, these efficient nanofactories protect human cells from toxic reactive oxygen species for up to a week. Remarkably, these results are obtained in spite of the nanofactories being localized in lysosomes, acidic organelles that contain a variety of proteases. The long-term persistence of the nanofactories is attributed to the chemical stability of MOF in low pH environment and to the protease resistance provided by the protective cage formed by the MOF around the encapsulated enzymes.

A mini-review of TAT-MyoD fused proteins: state of the art and problems to solve

The transcriptional activator TAT is a small peptide essential for viral replication and possesses the property of entering the cells from the extracellular milieu, acting as a membrane shuttle. In order to safely differentiate cells an innovative methodology, based on the fusion of transcription factors and the TAT sequence, is discussed in this short review. In several studies, it has been demonstrated that TAT protein can be observed in the cell nucleus after few hours from the inoculation although its way of action is not fully understood. However, further studies will be necessary to develop this methodology for clinical purposes.

Unlocking Endosomal Entrapment with Supercharged Arginine-Rich Peptides

Endosomal entrapment is a common bottleneck in various macromolecular delivery approaches. Recently, the polycationic peptide dfTAT was identified as a reagent that induces the efficient leakage of late endosomes and, thereby, enhances the penetration of macromolecules into the cytosol of live human cells. To gain further insights into the features that lead to this activity, the role of peptide sequence was investigated. We establish that the leakage activity of dfTAT can be recapitulated by polyarginine analogs but not by polylysine counterparts. Efficiencies of peptide endocytic uptake increase linearly with the number of arginine residues present. In contrast, peptide cytosolic penetration displays a threshold behavior, indicating that a minimum number of arginines is required to induce endosomal escape. Increasing arginine content above this threshold further augments delivery efficiencies. Yet, it also leads to increasing the toxicity of the delivery agents. Together, these data reveal a relatively narrow arginine-content window for the design of optimally active endosomolytic agents.

Toxin bioportides: exploring toxin biological activity and multifunctionality

Toxins have been shown to have many biological functions and to constitute a rich source of drugs and biotechnological tools. We focus on toxins that not only have a specific activity, but also contain residues responsible for transmembrane penetration, which can be considered bioportides-a class of cell-penetrating peptides that are also intrinsically bioactive. Bioportides are potential tools in pharmacology and biotechnology as they help deliver substances and nanoparticles to intracellular targets. Bioportides characterized so far are peptides derived from human proteins, such as cytochrome c (CYCS), calcitonin receptor (camptide), and endothelial nitric oxide synthase (nosangiotide). However, toxins are usually disregarded as potential bioportides. In this review, we discuss the inclusion of some toxins and molecules derived thereof as a new class of bioportides based on structure activity relationship, minimization, and biological activity studies. The comparative analysis of the amino acid residue composition of toxin-derived bioportides and their short molecular variants is an innovative analytical strategy which allows us to understand natural toxin multifunctionality in vivo and plan novel pharmacological and biotechnological products. Furthermore, we discuss how many bioportide toxins have a rigid structure with amphiphilic properties important for both cell penetration and bioactivity.

Foldamers in Medicinal Chemistry

Bio-inspired synthetic backbones leading to foldamers can provide effective biopolymer mimics with new and improved properties in a physiological environment, and in turn could serve as useful tools to study biology and lead to practical applications in the areas of diagnostics or therapeutics. Remarkable progress has been accomplished over the past 20 years with the discovery of many potent bioactive foldamers originating from diverse backbones and targeting a whole spectrum of bio(macro)molecules such as membranes, protein surfaces, and nucleic acids. These current achievements, future opportunities, and key challenges that remain are discussed in this article.

Delivery of Soluble Heme Oxygenase 1 Cell-Penetrating Peptide into Liver Cells in in vitro and ex vivo Models of Cold Ischemia

BACKGROUND/PURPOSE

Liver transplantation is the treatment of choice in patients with end-stage liver disease. During liver transplantation, ischemia-reperfusion injury (IRI) occurs, which is an inevitable consequence of the transplantation process. To reduce the extent of cellular injury, one of the proteins that have been extensively investigated is heme oxygenase 1 (HO-1), which plays an important role in protecting the organs against IRI. The aim of this study was to introduce an active and functional HO-1 protein conjugated to a cell-penetrating peptide (CPP) in vitro and ex vivo into liver cells in hypothermic and anoxic conditions and to assert its cytoprotective effects.

METHODS

We generated an enzymatically active soluble (s)HO-1-CPP recombinant protein. The ability of the sHO-1-CPP protein to penetrate McA-RH7777, Clone 9, and Hep G2 cells, primary hepatocytes, and Kupffer and human umbilical vein endothelial cells in vitro, as well as its ability to penetrate a whole liver ex vivo under hypothermic and anoxic conditions, was assessed. An in vitro hypoxia-reoxygenation (HR) model was used to determine the cytoprotective effect of the sHO-1-CPP protein.

RESULTS

We showed that our recombinant protein sHO-1-CPP can cross cell membranes into rodent and human liver cells in vitro, and the results were further validated ex vivo, where rodent livers were perfused with an organ preservation solution supplemented with sHO-1-CPP under anoxic and hypothermic conditions. Immunohistochemistry revealed an intracellular localization of sHO-1-CPP in zones 1-3 of the perfused livers. The CPP did not exert any significant toxicity on the cells. Treating cells with sHO-1-CPP showed significant cytoprotection in the in vitro HR model.

CONCLUSIONS

Our findings show that the recombinant protein sHO-1-CPP can be successfully delivered to cells of a whole organ in an ex vivo hypothermic and anoxic perfusion model and that it provides cytoprotection to hepatocytes in an in vitro HR model. These results hold great potential for future repair and protection of donor organs. Future experiments are planned to confirm these data in in vivo models of IRI.

Targeting MCM2 function as a novel strategy for the treatment of highly malignant breast tumors

Highly malignant tumors express high levels of the minichromosome maintenance 2 (MCM2) protein, which is associated with advanced tumor grade, advanced stage, and poor prognosis. In a previous study, we showed that Friend leukemia virus (FLV) envelope protein gp70 bound MCM2, impaired its nuclear translocation, and enhanced DNA-damage-induced apoptosis in FLV-infected hematopoietic cells when the cells expressed high levels of MCM2. Here, we show that MCM2 is highly expressed in clinical samples of invasive carcinoma of the breast, especially triple-negative breast cancer (TNBC), and in cancer stem cell (CSC) marker-positive breast cancer cells. To generate a cancer therapy model using gp70, we introduced the gp70 protein into the cytoplasm of murine breast cancer cells that express high levels of MCM2 by conjugating the protein transduction domain (PTD) of Hph-1 to gp70 (Hph- 1-gp70). Hph-1-gp70 was successfully transduced into the cytoplasm of breast cancer cells. The transduced protein enhanced the DNA damage-induced apoptosis of cancer cells in vitro and in vivo. Therefore, an MCM2-targeted strategy using Hph-1-gp70 treatment to induce DNA damage might be a successful therapy for highly malignant breast cancers such as TNBC and for the eradication of CSC-like cells from breast cancer tissue.

RGDS- and TAT-Conjugated Upconversion of NaYF4:Yb(3+)/Er(3+)&SiO2 Nanoparticles: In Vitro Human Epithelioid Cervix Carcinoma Cellular Uptake, Imaging, and Targeting

Starting NaYF4:Yb(3+)/Er(3+) nanoparticles with size tuned from 24 to 33 nm were prepared by high-temperature coprecipitation of lanthanide chlorides in high-boiling organic solvents. To enhance colloidal stability in aqueous medium, an aminosilica shell was introduced on the surface by hydrolysis and condensation of tetramethyl orthosilicate and (3-aminopropyl)trimethoxysilane using a reverse microemulsion technique; to form alkyne groups, reaction with 4-pentynoic acid followed. Finally, the cell adhesive and cell penetrating azidopentanoyl-GGGRGDSGGGY-NH2 (RGDS) and azidopentanoyl-GGGRKKRRQRRR-NH2 (TAT) peptides were conjugated to the upconversion particles via Cu(I)-catalyzed alkyne-azide cycloaddition. The concentrations of the peptides bound to the nanoparticle surfaces and amount of adsorbed residual Cu(I) catalyst were determined using an (125)I-radiolabeled RGDS peptide and a (64)Cu(I)-doped catalyst, respectively. Targeting and uptake of the RGDS- and TAT-conjugated NaYF4:Yb(3+)/Er(3+)&SiO2 nanoparticles by human cervix carcinoma HeLa cells were monitored by confocal microscopy. RGDS-conjugated nanoparticle probes were mainly localized on the cell plasma membrane due to specific binding of the peptide to the corresponding integrins. In contrast, the TAT-conjugated nanoparticles were able to cross the cell membrane and accumulate in the cell cytoplasm. Thus, this new peptide bioconjugation approach supported both extra- and intracellular nanoparticle uptake, enabling targeting and imaging of the specific tumor phenotypes.