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The 12 kDa FK506-binding protein (FK506BP12), an immunosuppressor, modulates T cell activation via calcineurin inhibition. In this study, we investigated the ability of PEP-1-FK506BP12, consisting of FK506BP12 fused to the protein transduction domain PEP-1 peptide, to suppress catabolic responses in primary human chondrocytes and in a mouse carrageenan-induced paw arthritis model. Western blotting and immunofluorescence analysis showed that PEP-1-FK506BP12 efficiently penetrated chondrocytes and cartilage explants. In interleukin-1β (IL-1β)-treated chondrocytes, PEP-1-FK506BP12 significantly suppressed the expression of catabolic enzymes, including matrix metalloproteinases (MMPs)-1, -3, and -13 in addition to cyclooxygenase-2, at both the mRNA and protein levels, whereas FK506BP12 alone did not. In addition, PEP-1-FK506BP12 decreased IL-1β-induced phosphorylation of the mitogen-activated protein kinase (MAPK) complex (p38, JNK, and ERK) and the inhibitor kappa B alpha. In the mouse model of carrageenan-induced paw arthritis, PEP-1-FK506BP12 suppressed both carrageenan-induced MMP-13 production and paw inflammation. PEP-1-FK506BP12 may have therapeutic potential in the alleviation of OA progression. [BMB Reports 2015; 48(7): 407-412]

Oxidative stress-induced reactive oxygen species (ROS) are responsible for various neuronal diseases. Antioxidant 1 (Atox1) regulates copper homoeostasis and promotes cellular antioxidant defence against toxins generated by ROS. The roles of Atox1 protein in ischaemia, however, remain unclear. In this study, we generated a protein transduction domain fused Tat-Atox1 and examined the roles of Tat-Atox1 in oxidative stress-induced hippocampal HT-22 cell death and an ischaemic injury animal model. Tat-Atox1 effectively transduced into HT-22 cells and it protected cells against the effects of hydrogen peroxide (H2O2)-induced toxicity including increasing of ROS levels and DNA fragmentation. At the same time, Tat-Atox1 regulated cellular survival signalling such as p53, Bad/Bcl-2, Akt and mitogen-activate protein kinases (MAPKs). In the animal ischaemia model, transduced Tat-Atox1 protected against neuronal cell death in the hippocampal CA1 region. In addition, Tat-Atox1 significantly decreased the activation of astrocytes and microglia as well as lipid peroxidation in the CA1 region after ischaemic insult. Taken together, these results indicate that transduced Tat-Atox1 protects against oxidative stress-induced HT-22 cell death and against neuronal damage in animal ischaemia model. Therefore, we suggest that Tat-Atox1 has potential as a therapeutic agent for the treatment of oxidative stress-induced ischaemic damage.

CyclinD1/CDK4 and cyclinD3/CDK4 complexes are key regulators of the cell progression and therefore constitute promising targets for the design of anticancer agents. In the present study, the key peptide motifs were selected from these two complexes. Chimeric peptides with these peptides conjugated to the protein transduction domain 4 (PTD4) were designed and synthesized. The chimeric peptides, PTD4-D1, PTD4-D3, PTD4-K4 exhibited significant anti-proliferation effects on cancer cell lines. These peptides could compete with the cyclinD/CDK4 complex and induce the G1/S phase arrest and apoptosis of cancer cells. In the tumor challenge experiment, these peptides showed potent antitumor effects with no significant side effects. Our results suggested that these peptides could be served as novel leading compounds with potent antitumor activity.

Protein transduction domains (PTDs) have been successfully employed to deliver therapeutic cargos both in vitro and in vivo because of their cellular penetrating ability. We previously reported that a 10-amino acid peptide (MIIYRDLISH) derived from the NH 2 -terminus of human translationally controlled tumor protein (TCTP) functions as a PTD. TCTP–PTD is quite different from other well-known PTDs in its hydrophobic composition and structural character, and the sequence requirements for transduction remain unknown. To identify the role of each residue, we compared the cellular uptake of various deletion mutants and Ala substituents of TCTP–PTD. The results showed that the amino terminal residues and the hydrophobic nature of the peptide, with a minimal length of nine residues, were necessary for transduction. Based on the elucidated sequence requirements, we designed and evaluated variants to improve the efficiency and solubility through sequential modification of TCTP–PTD. During the optimization process, we also delineated the contribution of residues and the advantageous composition of sequences for cellular uptake.

Here we report and validate a new method, suitable broadly, for use in differentiated cells and tissues, for the direct visualization of actin polymerization under physiological conditions. We have designed and tested different versions of fluorescently labeled actin, reversibly attached to the protein transduction tag TAT, and have introduced this novel reagent into intact differentiated vascular smooth muscle cells (dVSMCs). A thiol-reactive version of the TAT peptide was synthesized by adding the amino acids glycine and cysteine to its NH2-terminus and forming a thionitrobenzoate adduct: viz. TAT-Cys-S-STNB. This peptide reacts readily with G-actin, and the complex is rapidly taken up by freshly enzymatically isolated dVSMC, as indicated by the fluorescence of a FITC tag on the TAT peptide. By comparing different versions of the construct, we determined that the optimal construct for biological applications is a nonfluorescently labeled TAT peptide conjugated to rhodamine-labeled actin. When TAT-Cys-S-STNB-tagged rhodamine actin (TSSAR) was added to live, freshly enzymatically isolated cells, we observed punctae of incorporated actin at the cortex of the cell. The punctae are indistinguishable from those we have previously reported to occur in the same cell type when rhodamine G-actin is added to permeabilized cells. Thus this new method allows the delivery of labeled G-actin into intact cells without disrupting the native state and will allow its further use to study the effect of physiological intracellular Ca2+concentration transients and signal transduction on actin dynamics in intact cells.

The protein transduction domain of HIV-1 TAT, TAT(48-60), is an efficient cell-penetrating peptide (CPP) that diffuses across the lipid membranes of cells despite eight cationic Arg and Lys residues. To understand its mechanism of membrane translocation against the free energy barrier, we have conducted solid-state NMR experiments to determine the site-specific conformation, dynamics, and lipid interaction of the TAT peptide in anionic lipid bilayers. We found that TAT(48-60) is a highly dynamic and nearly random-coil peptide in the lipid bilayer, and inserts into the membrane-water interface near the glycerol backbone region. Arg-phosphate salt bridge interaction was revealed by short guanidinium-phosphate distances and restricted dynamics of the guanidinium. Together with the observation of strong peptide-water cross peaks in 1H spin diffusion spectra, these results indicate that TAT binding to the membrane-water interface is stabilized not only by electrostatic attraction to the anionic lipids, but also by intermolecular hydrogen bonding with the lipid phosphates and water, which may take the role of intramolecular hydrogen bonds in canonical secondary structures. The random-coil structure of TAT and another CPP, penetratin, suggests that the lack of amphipathic structure is essential for rapid translocation of these Arg-rich CPPs across the lipid membrane without causing permanent damages to the membrane integrity.

Glutathione transferases are a family of enzymes that are traditionally known to contribute to the phase II class of detoxification reactions. However, a novel property of the Schistosoma japonicum glutathione transferase (Sj.GST26) involves its translocation from the external medium into a variety of different cell types. Here we explore the efficiency and mechanism of cell entry for this class of protein. Using flow cytometry and confocal microscopy, we have examined the internalisation of Sj.GST26 into live cells under a variety of conditions designed to shed light on the mode of cellular uptake. Our results show that Sj.GST26 can effectively enter cells through an energy-dependent event involving endocytosis. More specifically, Sj.GST26 was found to colocalise with transferrin within the cell indicating that the endocytosis process involves clathrin-coated pits. A comprehensive study into the cellular internalisation of proteins from other classes within the GST structural superfamily has also been conducted. These experiments suggest that the ‘GST-fold’ structural motif influences cellular uptake, which presents a novel glimpse into an unknown aspect of GST function.

Background Gene transfer with some vectors may be useful for treatment of cerebral vasospasm after subarachnoid haemorrhage (SAH) [2, 3, 6, 10, 12, 13, 19]. However, this method has some safety problems [18]. Previous studies have shown that direct delivery of therapeutic proteins by using protein transduction domain (PTD) may reduce these problems [14, 15]. Here, we examined the transduction efficiency of eleven consecutive arginines (11R), which is one of the most effective PTD [8, 9], into the rat cerebral arteries by using 11R-enhanced-green fluorescent protein (11R-EGFP).

Suicide gene therapy is a promising approach for the treatment of cancer. Current protocols, however, suffer from low efficiency. We tried to alleviate this problem by developing a transgene that will spread from the initially transduced cell to the surrounding cells (transmission). We used herpes simplex virus (HSV) VP22 as a signal for cellular uptake of HSV-1 thymidine kinase (TK). By co-culturing naive cells with cells producing a TK-VP22 fusion protein, we detected intercellular trafficking of this protein. We used a variety of techniques, including two-color flow cytometry and cytotoxicity assays to detect the presence of TK in the non-producing cells. We confirmed intercellular migration of VP22. We did not detect any intercellular trafficking of the TK-VP22 fusion protein, by various fixation methods or flow cytometry. In ganciclovir sensitivity assays, we found no difference between the efficiency of TK (IC50=3.15 +/- 0.76 mu g/ml) and TK-VP22 (IC50=2.27 +/- 0.59 mu g/ml). Using a cell-free enzyme activity assay we showed that fusion of TK to VP22 did not change the enzyme activity. In conclusion, we described novel and robust methods to detect intercellular trafficking. From our data we concluded that protein transmission of TK by VP22 for gene therapy is not likely to be successful. In addition, we described a useful and quantifiable assay to measure the enzymatic activity of TK and TK fusion proteins, and described some common properties of VP22 fusion proteins that may explain the different results that have been obtained by others.

The delivery and expression of exogenous genes in plant cells have been of particular interest for plant research and biotechnology. Here, we present results demonstrating a simple DNA transfection system in plants. Short arginine-rich intracellular delivery peptide, a protein transduction domain, was capable of delivering plasmid DNA into living plant cells non-covalently. This peptide-mediated DNA delivery conferred several advantages, such as nuclear targeting, non-toxic effect, and ease of preparation without protoplast formulation. Thus, this novel technology shall provide a powerful tool to investigate gene function in vivo, and lay the foundation for the production of transgenic plants in future.

The direct intracellular delivery of proteins has, until recently, been difficult to achieve, due primarily to the bioavailability barrier of the plasma membrane. During the past 15 years, a variety of peptides called protein transduction domains (PTDs) or cell penetrating peptides (CPPs), have been characterized for their ability to translocate into live cells. The most commonly studied are homeodomain transcription factors such as Antennapedia, the herpes simplex virus (HSV) type 1 protein VP22, and the human immunodeficiency virus (HIV-1) transactivator TAT protein. Recently, polyarginine exhibits even greater efficiency in terms of delivery of several peptides and proteins. Numerous examples of biologically active full-length proteins and peptides have been delivered to cells and tissues, both in vitro and in vivo. These studies offer new avenues for treatment of several diseases. The main mechanism of protein transduction is an electrostatic interaction with the plasma membrane, penetration into cells by macropinocytosis, and a release to cytoplasm and nuclei by retrograde transport. Moreover, the intercellular transfer of endogenous transcription factors, such as TAT and homeoproteins, seems to point to an original and important mode of signal transduction. The protein transduction systems have opened up several possibilities, not only for the development of new peptide/protein drugs but also for consideration of their physiological and developmental implications.

Caspases play a major role in the infarction process that follows occlusion of cerebral arteries and are important targets for stroke therapy. We have generated three fusion proteins that link various domains of the X chromosome-linked inhibitor of apoptosis (XIAP), a potent caspase inhibitor, to the protein transduction domain (PTD) of HIV-1/Tat, and have tested their efficacy after distal occlusion of the middle cerebral artery (dMCAO) in mice. PTD–XIAP failed to accumulate in brain structures after intravenous (iv) delivery, but properly transduced cortical cells when applied topically. Shorter constructs efficiently targeted the lesion after iv delivery. All proteins retained their caspase inhibitory activity and significantly reduced infarct volumes. PTD–XIAP reversed long-term impairments in the water maze test. Sequential activation of transcription factors was observed, suggesting that the effects of XIAP are mediated by both direct inhibition of apoptotic mechanisms and secondary regulation of transcription factors involved in neuronal survival.

Cell-penetrating peptides have been shown to translocate across eukaryotic cell membranes through a temperature-insensitive and energy-independent mechanism that does not involve membrane receptors or transporters. Although cell-penetrating peptides have been successfully used to mediate the intracellular delivery of a wide variety of molecules of pharmacological interest both in vitro and in vivo, the mechanisms by which cellular uptake occurs remain unclear. In the face of recent reports demonstrating that uptake of cell-penetrating peptides occurs through previously described endocytic pathways, or is a consequence of fixation artifacts, we conducted a critical re-evaluation of the mechanism responsible for the cellular uptake of the S413-PV karyophilic cell-penetrating peptide. We report that the S413-PV peptide is able to accumulate inside live cells very efficiently through a rapid, dose-dependent and non-toxic process, providing clear evidence that the cellular uptake of this peptide cannot be attributed to fixation artifacts. Comparative analysis of peptide uptake into mutant cells lacking heparan sulphate proteoglycans demonstrates that their presence at the cell surface facilitates the cellular uptake of the S413-PV peptide, particularly at low peptide concentrations. Most importantly, our results clearly demonstrate that, in addition to endocytosis, which is only evident at low peptide concentrations, the efficient cellular uptake of the S413-PV cell-penetrating peptide occurs mainly through an alternative, non-endocytic mechanism, most likely involving direct penetration across cell membranes.

The protein transduction system has been employed for delivery of bioactive proteins into cells via an endocytotic mechanism. However, trapping of endocytosed proteins in the endosome may significantly attenuate biological actions in cells. The present investigation demonstrated that endosomal release of transduced protein could be artificially accelerated by exposure to fluorescent light. Exposure to light at 480 nm stimulated endosomal release of transduced FITC-11 arginine-protein transduction domain (11R-PTD), TAT-PTD and Antennapedia-PTD. Moreover, FITC-11R-p53 protein was released from endosomes following stimulation with light. These data suggest that photo-acceleration is a more efficient strategy in terms of the protein transduction system.

International audience; New therapeutic agents able to block HIV-1 replication are eagerly sought after to increase the possibilities of treatment of resistant viral strains. In this report, we describe a rational strategy to identify small peptide sequences owning the dual property of penetrating within lymphocytes and of binding to a protein target. Such sequences were identified for two important HIV-1 regulatory proteins, Tat and Rev. Their association to a stabilizing domain consisting of human small ubiquitin-related modifier-1 (SUMO-1) allowed the generation of small proteins named SUMO-1 heptapeptide protein transduction domain for binding Tat (SHPT) and SUMO-1 heptapeptide protein transduction domain for binding Rev (SHPR), which are stable and efficiently penetrate within primary lymphocytes. Analysis of the antiviral activity of these proteins showed that one SHPR is active in both primary lymphocytes and macrophages, whereas one SHPT is active only in the latter cells. These proteins may represent prototypes of new therapeutic agents targeting the crucial functions exerted by both viral regulatory factors.

The recent discoveries of serious artifacts associated with the use of cell fixation in studies of the cellular uptake of cell-penetrating peptides (CPPs) have prompted a reevaluation of the current understanding of peptide-mediated cellular delivery. Following a report on the differential cellular uptake of a number of penetratin analogs in unfixed cells, we here investigate their membrane translocation abilities in large and giant unilamellar vesicles (LUVs and GUVs, respectively). Surprisingly, in contrast to the behavior in living cells, all peptides readily entered the giant vesicles (>1 μm) as proved by confocal microscopy, while none of them could cross the membranes of LUVs (100 nm). For determination of the location of the peptides in the LUVs, a new concept was introduced, based on sensitive resonance energy transfer (RET) measurements of the enhanced fluorescence of acceptor fluorophores present solely in the inner leaflet. An easily adopted method to prepare such asymmetrically labeled liposomes is described. The membrane insertion depths of the tryptophan moieties of the peptides were determined by use of brominated lipids and found to be very similar for all of the peptides studied. We also demonstrate that infrared spectroscopy on the lipid carbonyl stretch vibration peak is a convenient technique to determine phospholipid concentration.

We have reported previously that HIV-TAT-dominant negative (dn) Ras inhibits eosinophil adhesion to ICAM-1 after activation by IL-5 and eotaxin. In this study, we evaluated the role of Ras in Ag-induced airway inflammation and hyperresponsiveness by i.p. administration into mice of dnRas, which was fused to an HIV-TAT protein transduction domain (TAT-dnRas). Uptake of TAT-dnRas (t1/2 = 12 h) was demonstrated in leukocytes after i.p. administration. OVA-sensitization significantly increased eosinophil and lymphocyte numbers in bronchoalveolar lavage fluid 24 h after final challenge. Treatment of animals with 3–10 mg/kg TAT-dnRas blocked the migration of eosinophils from 464 ± 91 × 103/ml to 288 ± 79 × 103/ml with 3 mg/kg of TAT-dnRas (p < 0.05), and further decreased to 116 ± 63 × 103/ml after 10 mg/kg TAT-dnRas (p < 0.01). Histological examination demonstrated that inflammatory cell infiltration (largely eosinophils and mononuclear cells) and mucin production around the airways caused by OVA were blocked by TAT-dnRas. OVA challenge also caused airway hyperresponsiveness to methacholine, which was dose dependently blocked by treatment with TAT-dnRas. TAT-dnRas also blocked Ag-induced IL-4 and IL-5, but not IFN-γ, production in lung tissue. Intranasal administration of IL-5 caused eosinophil migration into the airway lumen, which was attenuated by pretreatment with TAT-dnRas. By contrast, TAT-green fluorescent protein or dnRas lacking the TAT protein transduction domain did not block airway inflammation, cytokine production, or airway hyperresponsiveness. We conclude that Ras mediates Th2 cytokine production, airway inflammation, and airway hyperresponsiveness in immune-sensitized mice.

Glial-cell-line-derived neurotrophic factor (GDNF) acts as a potent survival factor for many neuronal populations, including retinal ganglion cells (RGC), indicating a potential therapeutic role of GDNF for neurological disorders. To enhance the tissue distribution and applicability of the neurotrophin, we linked it to a protein transduction domain derived from the HIV TAT protein and tested it in a well-established model for traumatic injury in the CNS: After optic nerve axotomy, the number of surviving RGCs was significantly increased in mice injected with TAT-GDNF on days 0, 3, 7, and 10 after surgery compared with GDNF- or PBS-injected animals. Moreover, TAT-GDNF reduced the number of activated caspase-3- positive cells. These results show that the neuroprotective effect of substances like neurotrophins may be enhanced by linking them to a domain that has been shown to mediate efficient transduction across biological membranes. In the recent years, a large number of peptides with neuroprotective or anti-apoptotic features has been characterized. It was suggested that application of neuroprotective proteins might be a favorable approach to treat neurodegenerative diseases. However, delivery of such proteins into tissues and across the blood-brain or bloodretina barrier is limited by the size of the respective proteins. The protein transduction domain derived from the human immunodeficiency virus-1 TAT protein is able to deliver biologically active proteins across these barriers in vivo [1, 2]. Glial-cell-line-derived neurotrophic factor (GDNF), a member of the transforming growth factor-ß superfamily, is a potent neurotrophic factor that promotes the survival and morphological differentiation of dopaminergic neurons [3–5], motor neurons [6, 7] and retinal ganglion cells (RGC) [8, 9]. The protective effects of externally applied GDNF have been well established in different models of neurodegenerative diseases [10–13]. The retinotectal projection is a well-defined experimental system, which enables to study molecular mechanisms of de- and regeneration of injured neurons of the central nervous system in vivo. In adult mammals, transection of the optic nerve (ON) triggers a highly coordinated response of injury-associated gene expression in lesioned RGC somata, which results in the activation of apoptotic cascades and finally leads to cell death [for TAT Enhanced GDNF Therapy after RGC Axotomy Neurodegenerative Dis 2004;1:44–49 45 review, see ref. 14–18]. Transection of the ON has also been successfully used to study the efficacy of various neuroprotective agents [17, 19]. In this study, the distribution of the TAT-mediated GDNF transduction was examined in different tissues after intravitreal administration of TAT-GDNF protein. In the second part of this study, the neuroprotective effects of TAT-GDNF fusion protein on the survival of axotomized RGC was evaluated and compared with GDNF- and PBS-treated animals after intravitreal administration of the respective factors. peerReviewed

About 25 years ago the observation that neuropeptides serve as signalling molecules in the nervous system generated great expectations for drug industry. In this article the progress made since then in exploiting neuropeptide systems pharmacologically in psychiatry is highlighted.

Background: Membrane-permeable macromolecular (MPM) probes are designed to deliver functional proteins to disease sites and into cells by using protein transduction domain (PTD). To visualize intracellular

Delivery of small interfering RNA (siRNA) targeted to specific cell types is a significant challenge for the development of RNA interference-based therapeutics. Recently, PTD-DRBD, a double-stranded RNA binding domain (DRBD) fused to the TAT protein transduction domain (PTD), was shown to be effective at delivering siRNA in a non-cell type-specific manner. Here, we evaluated the potential of DRBD as a general protein platform for targeted small interfering RNA (siRNA) delivery. We found that a single DRBD was insufficient to stably complex siRNA when fused to targeting peptides other than PTD, which facilitated nonspecific nucleic acid binding. In contrast to PTD-DRBD, fusion proteins containing two DRBDs (2× DRBD) yielded specific and stable siRNA binding. These proteins could mediate the cellular uptake of siRNA in vitro, though compared with PTD-DRBD gene silencing was attenuated by endosomal entrapment. Our findings suggest that unlike a single DRBD, 2× DRBD inhibits siRNA escape into the cytoplasm and/or induces an internalization pathway distinct from that of PTD-DRBD. Collectively, these data indicate that while 2× DRBD retains siRNA-binding activity when fused to different cell surface-interacting peptides, the utility of 2× DRBD for cell-specific RNA interference is limited without further protein engineering to enhance the bioavailability of the delivered siRNAs.Molecular Therapy - Nucleic Acids (2012) 1, e53; doi:10.1038/mtna.2012.43; published online 13 November 2012.

Dual functionalization of gold nanorods (GNRs) with two kinds of surface ligands has been achieved. Phosphorylcholine (PC) could impart the GNRs with both biostability in the physiological environment and targetability towards cancer cells uniquely. On the other hand, the protein transduction domain of human immunodeficiency virus type 1 Tat peptide could induce the GNRs to be quickly internalized through cell membranes. The inductively coupled plasma mass spectroscopy (ICP-MS), TEM and UV-Vis assays all demonstrated that such dual-ligand GNRs exhibited both fast and selective cancer cell uptake advantages, which were utilized for more efficient cancer cell ablation under near-infrared (NIR) irradiation. This mode of the multivalent scaffold offers an optimized choice for future cell-based therapies.

A human Cu,Zn-superoxide dismutase was fused with a transcriptional transactivator protein transduction domain of HIV-1 to produce a novel anti-aging ingredient for cosmeceuticals, transcriptional transactivator superoxide dismutase (Tat-SOD). Stability tests and evaluation of the transduction efficacy and enzymatic activity suggest Tat-SOD is an effective active ingredient for anti-aging treatment.