Stem Cell Bioengineering with Bioportides: Inhibition of Planarian Head Regeneration with Peptide Mimetics of Eyes Absent Proteins.

Djeya1 (RKLAFRYRRIKELYNSYR) is a very effective cell penetrating peptide (CPP) that mimics the α5 helix of the highly conserved Eya domain (ED) of eyes absent (Eya) proteins. The objective of this study was to bioengineer analogues of Djeya1 that, following effective translocation into planarian tissues, would reduce the ability of neoblasts (totipotent stem cells) and their progeny to regenerate the anterior pole in decapitated S. mediterranea. As a strategy to increase the propensity for helix formation, molecular bioengineering of Djeya1 was achieved by the mono-substitution of the helicogenic aminoisobutyric acid (Aib) at three species-variable sites: 10, 13, and 16. CD analyses indicated that Djeya1 is highly helical, and that Aib-substitution had subtle influences upon the secondary structures of bioengineered analogues. Aib-substituted Djeya1 analogues are highly efficient CPPs, devoid of influence upon cell viability or proliferation. All three peptides increase the migration of PC-3 cells, a prostate cancer line that expresses high concentrations of Eya. Two peptides, [Aib13]Djeya1 and [Aib16]Djeya1, are bioportides which delay planarian head regeneration. As neoblasts are the only cell population capable of division in planaria, these data indicate that bioportide technologies could be utilised to directly manipulate other stem cells in situ, thus negating any requirement for genetic manipulation.

Modulation of serine/threonine-protein phosphatase 1 (PP1) complexes: A promising approach in cancer treatment.

Cancer is the second leading cause of death worldwide. Despite the availability of numerous therapeutic options, tumor heterogeneity and chemoresistance have limited the success of these treatments, and the development of effective anticancer therapies remains a major focus in oncology research. The serine/threonine-protein phosphatase 1 (PP1) and its complexes have been recognized as potential drug targets. Research on the modulation of PP1 complexes is currently at an early stage, but has immense potential. Chemically diverse compounds have been developed to disrupt or stabilize different PP1 complexes in various cancer types, with the objective of inhibiting disease progression. Beneficial results obtained in vitro now require further pre-clinical and clinical validation. In conclusion, the modulation of PP1 complexes seems to be a promising, albeit challenging, therapeutic strategy for cancer.

Chronic exercise training attenuates prostate cancer-induced molecular remodelling in the testis.

PURPOSE: Prostate cancer is a major cause of cancer-related death in males worldwide and, in addition to impairing prostate function, also causes testicular adaptations. In this study, we aim to investigate the preventive effect of exercise training on PCa-induced testicular dysfunction. METHODS: As a model, we used fifty Wistar Unilever male rats, randomly divided in four experimental groups. Prostate cancer was chemically and hormonally induced in two groups of animals (PCa groups). One control group and one PCa group was submitted to moderate intensity treadmill exercise training. Fifty weeks after the start of the training the animals were sacrificed and sperm, prostate, testis and serum were collected and analyzed. Sperm concentration and morphology, and testosterone serum levels were determined. In addition, histological analyses of the testes were performed, and testis proteomes and metabolomes were characterized. RESULTS: We found that prostate cancer negatively affected testicular function, manifested as an arrest of spermatogenesis. Oxidative stress-induced DNA damage, arising from reduced testis blood flow, may also contribute to apoptosis of germ cells and consequential spermatogenic impairment. Decreased utilization of the glycolytic pathway, increased metabolism of ketone bodies and the accumulation of branched chain amino acids were also evident in the PCa animals. Conversely, we found that the treadmill training regimen activated DNA repair mechanisms and counteracted several metabolic alterations caused by PCa without impact on oxidative stress. CONCLUSIONS: These findings confirm a negative impact of prostate cancer on testis function and suggest a beneficial role for exercise training in the prevention of prostate cancer-induced testis dysfunction.

The disruption of protein-protein interactions as a therapeutic strategy for prostate cancer.

Prostate cancer (PCa) is one of the most common male-specific cancers worldwide, with high morbidity and mortality rates associated with advanced disease stages. The current treatment options of PCa are prostatectomy, hormonal therapy, chemotherapy or radiotherapy, the selection of which is usually dependent upon the stage of the disease. The development of PCa to a castration-resistant phenotype (CRPC) is associated with a more severe prognosis requiring the development of a new and effective therapy. Protein-protein interactions (PPIs) have been recognised as an emerging drug modality and targeting PPIs is a promising therapeutic approach for several diseases, including cancer. The efficacy of several compounds in which target PPIs and consequently impair disease progression were validated in phase I/II clinical trials for different types of cancer. In PCa, various small molecules and peptides proved successful in inhibiting important PPIs, mainly associated with the androgen receptor (AR), Bcl-2 family proteins, and kinases/phosphatases, thus impairing the growth of PCa cells in vitro. Moreover, a majority of these compounds require further validation in vivo and, preferably, in clinical trials. In addition, several other PPIs associated with PCa progression have been identified and now require experimental validation as potential therapeutic loci. In conclusion, we consider the disruption of PPIs to be a promising though challenging therapeutic strategy for PCa. Agents which modulate PPIs might be employed as a monotherapy or as an adjunct to classical chemotherapeutics to overcome drug resistance and improve efficacy. The discovery of new PPIs with important roles in disease progression, and of novel optimized strategies to target them are major challenges for the scientific and pharmacological communities.

The cationic tetradecapeptide mastoparan as a privileged structure for drug discovery: Enhanced antimicrobial properties of mitoparan analogues modified at position-14.

Mastoparan (MP) peptides, distributed in insect venoms, induce a local inflammatory response post envenomation. Most endogenous MPs share common structural elements within a tetradecapeptide sequence that adopts an amphipathic helix whilst traversing biological membranes and when bound to an intracellular protein target. Rational modifications to increase cationic charge density and amphipathic helicity engineered mitoparan (MitP), a mitochondriotoxic bioportide and potent secretagogue. Following intracellular translocation, MitP is accreted by mitochondria thus indicating additional utility as an antimicrobial agent. Hence, the objectives of this study were to compare the antimicrobial activities of a structurally diverse set of cationic cell penetrating peptides, including both MP and MitP sequences, and to chemically engineer analogues of MitP for potential therapeutic applications. Herein, we confirm that, like MP, MitP is a privileged structure for the development of antimicrobial peptides active against both prokaryotic and eukaryotic pathogens. Collectively, MitP and target-selective chimeric analogues are broad spectrum antibiotics, with the Gram-negative A. baumannii demonstrating particular susceptibility. Modifications of MitP by amino acid substitution at position-14 produced peptides, Δ14MitP analogues, with unique pharmacodynamic properties. One example, [Ser14]MitP, lacks both cytotoxicity against human cell lines and mast cell secretory activity yet retains selective activity against the encapsulated yeast C. neoformans.

Modulation of mitochondrial activity in HaCaT keratinocytes by the cell penetrating peptide Z-Gly-RGD(DPhe)-mitoparan.

OBJECTIVE: Biologically active cell penetrating peptides (CPPs) are an emerging class of therapeutic agent. The wasp venom peptide mastoparan is an established CPP that modulates mitochondrial activity and triggers caspase-dependent apoptosis in cancer cells, as does the mastoparan analogue mitoparan (mitP). Mitochondrial depolarisation and activation of the caspase cascade also underpins the action of dithranol, a topical agent for treatment of psoriasis. The effects of a potent mitP analogue on mitochondrial activity were therefore examined to assess its potential as a novel approach for targeting mitochondria for the treatment of psoriasis. RESULTS: In HaCaT keratinocytes treated with the mitP analogue Z-Gly-RGD(DPhe)-mitP for 24 h, a dose-dependent loss of mitochondrial activity was observed using the methyl-thiazolyl-tetrazolium (MTT) assay. At 10 µmol L-1, MTT activity was less than 30% that observed in untreated cells. Staining with the cationic dye JC-1 suggested that Z-Gly-RGD(DPhe)-mitP also dissipated the mitochondrial membrane potential, with a threefold increase in mitochondrial depolarisation levels. However, caspase activity appeared to be reduced by 24 h exposure to Z-Gly-RGD(DPhe)-mitP treatment. Furthermore, Z-Gly-RGD(DPhe)-mitP treatment had little effect on overall cell viability. Our findings suggest Z-Gly-RGD(DPhe)-mitP promotes the loss of mitochondrial activity but does not appear to evoke apoptosis in HaCaT keratinocytes.

Insights into the molecular mechanisms of action of bioportides: a strategy to target protein-protein interactions.

Cell-penetrating peptides (CPPs) are reliable vehicles for the target-selective intracellular delivery of therapeutic agents. The identification and application of numerous intrinsically bioactive CPPs, now designated as bioportides, is further endorsement of the tremendous clinical potential of CPP technologies. The refinement of proteomimetic bioportides, particularly sequences that mimic cationic α-helical domains involved in protein-protein interactions (PPIs), provides tremendous opportunities to modulate this emergent drug modality in a clinical setting. Thus, a number of CPP-based constructs are currently undergoing clinical trials as human therapeutics, with a particular focus upon anti-cancer agents. A well-characterised array of synthetic modifications, compatible with modern solid-phase synthesis, can be utilised to improve the biophysical and pharmacological properties of bioportides and so achieve cell-and tissue-selective targeting in vivo. Moreover, considering the recent successful development of stapled α-helical peptides as anti-cancer agents, we hypothesise that similar structural modifications are applicable to the design of bioportides that more effectively modulate the many interactomes known to underlie human diseases. Thus, we propose that stapled-helical bioportides could satisfy all of the clinical requirements for metabolically stable, intrinsically cell-permeable agents capable of regulating discrete PPIs by a dominant negative mode of action with minimal toxicity.

Protein Mimicry and the Design of Bioactive Cell-Penetrating Peptides.

The multi-domain architecture of many human proteins provides a structural basis for the physical maintenance of interactomes, or networks of protein-protein interactions (PPIs), that are so obviously crucial to cellular functions. Moreover, the structural and electrostatic complementarity provided by PPI interfaces, predominantly located on protein surfaces, is a fundamental component of signal transduction events that are known to be compromised in human diseases including many cancers.The pharmacokinetic advantages provided by cell-penetrating peptides (CPPs) are entirely compatible with the development of intrinsically permeable agents capable of modulating intracellular PPIs. Thus, the term bioportide is a useful descriptor of numerous bioactive CPPs that are distinct from the more usual inert CPP vectors. Herein we illustrate a generic strategy, predominantly centered upon the identification of cationic peptides derived from helical protein domains, which offers a reliable platform to identify bioportides capable of modulating intracellular signal transduction events. In addition, we describe robust methodologies to determine the precise intracellular distribution of fluorescent bioportides and present assays routinely employed to screen for the detrimental pharmacodynamic properties often exhibited by both CPPs and bioportides; namely adverse cytotoxicity and the receptor-independent stimulation of mast cell secretion.

Cell-penetrating peptides, targeting the regulation of store-operated channels, slow decay of the progesterone-induced [Ca2+]i signal in human sperm.

Previous work has provided evidence for involvement of store-operated channels (SOCs) in [Ca(2+)]i signalling of human sperm, including a contribution to the transient [Ca(2+)]i elevation that occurs upon activation of CatSper, a sperm-specific cation channel localized to the flagellum, by progesterone. To further investigate the potential involvement of SOCs in the generation of [Ca(2+)]i signals in human sperm, we have used cell-penetrating peptides containing the important basic sequence KIKKK, part of the STIM-Orai activating region/CRAC activating domain (SOAR/CAD) of the regulatory protein stromal interaction molecule 1. SOAR/CAD plays a key role in controlling the opening of SOCs, which occurs upon mobilization of stored Ca(2+). Resting [Ca(2+)]i temporarily decreased upon application of KIKKK peptide (3-4 min), but scrambled KIKKK peptide had a similar effect, indicating that this action was not sequence-specific. However, in cells pretreated with KIKKK, the transient [Ca(2+)]i elevation induced by stimulation with progesterone decayed significantly more slowly than in parallel controls and in cells pretreated with scrambled KIKKK peptide. Examination of single-cell responses showed that this effect was due, at least in part, to an increase in the proportion of cells in which the initial transient was maintained for an extended period, lasting up to 10 min in a subpopulation of cells. We hypothesize that SOCs contribute to the progesterone-induced [Ca(2+)]i transient, and that interference with the regulatory mechanisms of SOC delays their closure, causing a prolongation of the [Ca(2+)]i transient.

Can RNAi-mediated hsp90α knockdown in combination with 17-AAG be a therapy for glioma?

Heat shock protein 90 promotes tumor progression and survival and has emerged as a vital therapeutic target. Previously we reported that the combinatorial treatment of 17AAG/sihsp90α significantly downregulated Hsp90α mRNA and protein levels in Glioblastoma Multiforme (GBM). Here we investigated the ability of cell penetrating peptide (Tat48-60 CPP)-mediated siRNA-induced hsp90α knockdown as a single agent and in combination with 17-allylamino-17-demethoxygeldanamycin (17-AAG) to induce tumor growth inhibition in GBM and whether it possessed therapeutic implications. GBM and non-tumorigenic cells exposed to siRNA and/or 17-AAG were subsequently assessed by qRT-PCR, immunofluorescence, FACS analysis, quantitative Akt, LDH leakage and cell viability assays. PAGE was performed for serum stability assessment. A combination of siRNA/17-AAG treatment significantly induced Hsp90α gene and protein knockdown by 95% and 98%, respectively, concomitant to 84% Akt kinase activity attenuation, induced cell cycle arrest and tumor-specific cytotoxicity by 88%. Efficient complex formation between CPP and siRNA exhibited improved serum stability of the siRNA with minimal intrinsic toxicity in vitro. The preliminary in vivo results showed that combination therapy induced hsp90α knockdown and attenuated Akt kinase activity in intracranial glioblastoma mouse models. The results imply that RNAi-mediated hsp90α knockdown increases 17-AAG treatment efficacy in GBM. In addition, the cytotoxic response observed was the consequence of downregulation of hsp90α gene expression, reduced Akt kinase activity and S-G2/M cell cycle arrest. These results are novel and highlight the ability of Tat to efficiently deliver siRNA in GBM and suggest that the dual inhibition of Hsp90 has therapeutic potentials.

Bioportides: bioactive cell-penetrating peptides that modulate cellular dynamics.

The study and exploitation of cell-penetrating peptides (CPPs) now extends into a third exciting decade. Pharmacokinetic modulators, including the more common sequences Tat, penetratin and transportan-10, markedly enhance the intracellular delivery of small drugs, peptides, oligonucleotides and proteins. We introduced the term bioportide to distinguish cell penetrant peptides with intrinsic bioactivities from more typically inert CPP vectors. Our first examples included rhegnylogically organised bioportides, monomeric peptides presenting pharmacophores for both cellular internalization and bioactivity discontinuously distributed within the primary sequence. However, it is conceptually expedient to employ the same terminology to encompass sychnologic bioportides that comprise an inert CPP vector conjugated to an otherwise impermeable bioactive peptide. In such cases the CPP provides an obvious address function whilst the bioactive cargo, often a protein mimetic sequence, is the message. Additional targeting sequences, usually added as chimeric extensions, can also be accommodated within the design of CPPs and bioportides to enable cell- and tissue-selective targeting. Thus, the identification and exploitation of bioportides provides further scope to employ CPPs as research tools, diagnostics and therapeutics spanning a range of pathologies.

Peptide-based glioma-targeted drug delivery vector gHoPe2.

Gliomas are therapeutically challenging cancers with poor patient prognosis. New drug delivery strategies are needed to achieve a more efficient chemotherapy-based approach against brain tumors. The current paper demonstrates development of a tumor-targeted delivery vector that is based on a cell-penetrating peptide pVEC and a novel glioma-targeting peptide sequence gHo. The unique tumor-homing peptide gHo was identified using in vitro phage display technology. The novel delivery vector, which we designated as gHoPe2, was constructed by a covalent conjugation of pVEC, gHo, and a cargo; the latter could be either a labeling moiety (such as a fluorescent marker) or a cytostatic entity. Using a fluorescent marker, we demonstrate efficient uptake of the vector in glioma cells and selective labeling of glioma xenograft tumors in a mouse model. This is the first time that we know where in vitro phage display has yielded an efficient, in vivo working vector. We also demonstrate antitumor efficacy of the delivery vector gHoPe2 using a well-characterized chemotherapeutic drug doxorubicin. Vectorized doxorubicin proved to be more efficient than the free drug in a mouse glioma xenograft model after systemic administration of the drugs. In conclusion, we have characterized a novel glioma-homing peptide gHo, demonstrated development of a new and potential glioma-targeted drug delivery vector gHoPe2, and demonstrated the general feasibility of the current approach for constructing cell-penetrating peptide-based targeted delivery systems.

Bioportide: an emergent concept of bioactive cell-penetrating peptides.

Cell-penetrating peptides (CPPs) have proven utility for the highly efficient intracellular delivery of bioactive cargoes that include peptides, proteins, and oligonucleotides. The many strategies developed to utilize CPPs solely as pharmacokinetic modifiers necessarily requires them to be relatively inert. Moreover, it is feasible to combine one or multiple CPPs with bioactive cargoes either by direct chemical conjugation or, more rarely, as non-covalent complexes. In terms of the message-address hypothesis, this combination of cargo (message) linked to a CPP (address) as a tandem construct conforms to the sychnological organization. More recently, we have introduced the term bioportide to describe monomeric CPPs that are intrinsically bioactive. Herein, we describe the design and biochemical properties of two rhegnylogically organized monometic CPPs that collectively modulate a variety of biological and pathophysiological phenomena. Thus, camptide, a cell-penetrant sequence located within the first intracellular loop of a human calcitonin receptor, regulates cAMP-dependent processes to modulate insulin secretion and viral infectivity. Nosangiotide, a bioportide derived from endothelial nitric oxide synthase, potently inhibits many aspects of the endothelial cell morphology and movement and displays potent anti-angiogenic activity in vivo. We conclude that, due to their capacity to translocate and target intracellular signaling events, bioportides represent an innovative generic class of bioactive agents.

Enantiomer-specific bioactivities of peptidomimetic analogues of mastoparan and mitoparan: characterization of inverso mastoparan as a highly efficient cell penetrating peptide.

Retro-inverso transformation has commonly been employed as a strategy both for the synthesis of proteolytically stable peptide analogues and for the detailed investigation of structure activity relationships. Herein, we adopted a similar strategy to probe the structure activity relationships of two biologically active tetradecapeptides. Analogues of the α-helical mastoparan, and the highly potent apoptogenic analogue mitoparan, were synthesized using d-amino acids assembled in both endogenous (inverso) and reverse (retro-inverso) orientations. For a more comprehensive comparison, our studies also included the retro l-enantiomer of both peptides. Contrary to expectation, comparative investigations of cytotoxicity, mast cell degranulation, and cellular penetration demonstrated that, while retro-inverso transformation abrogated the associated biological activities of these helical peptides, inverso homologues retained their bioactivities. Moreover, inverso mastoparan demonstrated the highest translocation efficacy of all analogues with much improved uptake kinetics compared to other cell penetrating peptides (CPPs) including the commonly employed inert vectors penetratin and tat. Data presented herein thus propound the utility of inverso mastoparan as a highly efficient peptide vector. Furthermore, correlation analysis of plasma membrane translocation and intracellular uptake efficacy further supports a two-compartment model of CPP import whereby the intracellular accumulation of polycationic peptides is dependent upon both the efficiency of transport into the cell and their subsequent accretion at distinct subcellular loci.

Applications of cell-penetrating peptides as signal transduction modulators for the selective induction of apoptosis.

The discovery of cell-penetrating peptides (CPP) has provided the scientific community with relatively small and increasingly cost-effective molecular agents that readily cross the normally impermeable cell membrane. Thus, as either inert delivery vectors or biologically active agents, CPP can be used to selectively modulate intracellular signal transduction events. Indeed, the survival of many cancer cells is associated with alterations in the function of key intracellular signalling proteins. Accordingly, CPP constructs have been developed to access intracellular target loci in both normal and transformed cells. Thus, CPP are a novel, generic class of signal transduction modulator which can be utilized to specifically induce apoptosis in tumour cells as a potential therapeutic option. However, and particularly at higher concentrations, CPP can induce non-specific membrane perturbations, thus leading to cell death by necrotic mechanisms. This chapter, therefore, focuses on methodologies for the assessment of apoptotic events, including in situ TUNEL analysis, activation of caspase-3, and the MTT assay, whilst also discussing dual Annexin V and propidium iodide staining, an assay used for the quantification of cell populations undergoing apoptosis and/or necrosis.

Characterization of bioactive cell penetrating peptides from human cytochrome c: protein mimicry and the development of a novel apoptogenic agent.

Cell penetrating peptides (CPPs) with intrinsic biological activities offer a novel strategy for the modulation of intracellular events. QSAR analysis identified CPPs within human cytochrome c. Two such sequences, Cyt c(77-101) and Cyt c(86-101), induced tumor cell apoptosis, thus mimicking the role of Cyt c as a key regulator of programmed cell death. Quantitative analyses confirmed that Cyt c(77-101) is an extremely efficient CPP. Thus, Cyt c(77-101) was selected for modification to incorporate target-specific peptidyl motifs. Chimeric N-terminal extension with a target mimetic of FG nucleoporins significantly enhanced the apoptogenic potency of Cyt c(77-101) to a concentration readily achievable in vivo. Moreover, this construct, Nup153-Cyt c, facilitates the dramatic redistribution of nuclear pore complex proteins and thus propounds the nuclear pore complex as a novel target for the therapeutic induction of apoptosis.

Transport molecules using reverse sequence HIV-Tat polypeptides: not just any old Tat? (WO200808225).

BACKGROUND: Many polycationic cell penetrating peptides (CPPs), alternatively named protein transduction domains, have been used for the efficient intracellular delivery of biologically active agents. Patent WO2008/082885 relates to the properties and proposed biomedical applications of a CPP and putative-related sequences that represent the reverse sequence of a nonapeptide basic domain of the HIV-transactivator protein (Tat) (RRRQRRKKR). OBJECTIVE: This evaluation critically assesses the reported utility of such transport molecules and the numerous potential embodiments of the invention, in comparison with other recent developments in the field. We also review recent biomedical applications of Tat-derived peptide transporters. METHODS: The scope of this review includes both Tat-derived peptide transporters and other sequence-related CPPs that are polycationic in nature. RESULTS/CONCLUSION: The patent application indicates that reverse sequence HIV-Tat polypeptides can increase the transdermal delivery of an iodinated mixture of botulinum toxin, albumin and accessory proteins (Neuronox), Medy-Tox, Inc., Seoul, South Korea) as a non-covalent complex. Moreover, the invention also contemplates all variants of the reverse-sequence polypeptide and claims a variety of potential biomedical applications using the reverse sequence peptide as a delivery vector. Unfortunately, in the absence of both rigorous comparative data and toxicological analyses, it is uncertain if these transport molecules offer any advantages compared with many existing and rigorously characterised CPP vector systems.

Protein kinase A-dependent step(s) in hepatitis C virus entry and infectivity.

Viruses exploit signaling pathways to their advantage during multiple stages of their life cycle. We demonstrate a role for protein kinase A (PKA) in the hepatitis C virus (HCV) life cycle. The inhibition of PKA with H89, cyclic AMP (cAMP) antagonists, or the protein kinase inhibitor peptide reduced HCV entry into Huh-7.5 hepatoma cells. Bioluminescence resonance energy transfer methodology allowed us to investigate the PKA isoform specificity of the cAMP antagonists in Huh-7.5 cells, suggesting a role for PKA type II in HCV internalization. Since viral entry is dependent on the host cell expression of CD81, scavenger receptor BI, and claudin-1 (CLDN1), we studied the role of PKA in regulating viral receptor localization by confocal imaging and fluorescence resonance energy transfer (FRET) analysis. Inhibiting PKA activity in Huh-7.5 cells induced a reorganization of CLDN1 from the plasma membrane to an intracellular vesicular location(s) and disrupted FRET between CLDN1 and CD81, demonstrating the importance of CLDN1 expression at the plasma membrane for viral receptor activity. Inhibiting PKA activity in Huh-7.5 cells reduced the infectivity of extracellular virus without modulating the level of cell-free HCV RNA, suggesting that particle secretion was not affected but that specific infectivity was reduced. Viral particles released from H89-treated cells displayed the same range of buoyant densities as did those from control cells, suggesting that viral protein association with lipoproteins is not regulated by PKA. HCV infection of Huh-7.5 cells increased cAMP levels and phosphorylated PKA substrates, supporting a model where infection activates PKA in a cAMP-dependent manner to promote virus release and transmission.

Mitoparan and target-selective chimeric analogues: membrane translocation and intracellular redistribution induces mitochondrial apoptosis.

Mastoparan, and structurally-related amphipathic peptides, may induce cell death by augmentation of necrotic and/or apoptotic pathways. To more precisely delineate cytotoxic mechanisms, we determined that [Lys(5,8)Aib(10)]mastoparan (mitoparan) specifically induces apoptosis of U373MG and ECV304 cells, as demonstrated by endonuclease and caspase-3 activation and phosphatidylserine translocation. Live cell imaging confirmed that, following translocation of the plasma membrane, mitoparan specifically co-localizes with mitochondria. Complementary studies indicated that mitoparan induces swelling and permeabilization of isolated mitochondria, through cooperation with a protein of the permeability transition pore complex VDAC, leading to the release of the apoptogenic factor, cytochrome c. N-terminal acylation of mitoparan facilitated the synthesis of chimeric peptides that incorporated target-specific address motifs including an integrin-specific RGD sequence and a Fas ligand mimetic. Significantly, these sychnologically-organised peptides demonstrated further enhanced cytotoxic potencies. We conclude that the cell penetrant, mitochondriotoxic and apoptogenic properties of mitoparan, and its chimeric analogues, offer new insights to the study and therapeutic induction of apoptosis.

A sychnological cell penetrating peptide mimic of p21(WAF1/CIP1) is pro-apoptogenic.

Targeting chemotherapeutic agents directly to sites of DNA replication and repair within cancerous cells is problematic. This study attempts to address the issue of nuclear delivery of biologically active peptides with the potential to disrupt cancer cell growth. Herein, the protein transduction domain of the HIV-1 transactivator of transcription, Tat (Tat(48-60)), is used to deliver a cytotoxic peptide mimic of the cyclin-dependent kinase inhibitor, p21(WAF1/CIP1) into the nucleus. This construct, which we designate as Tat(48-60)-P10, contains the PCNA interacting protein (PIP) box. We demonstrate the utility of Tat(48-60) for peptide delivery to the nucleus and show that Tat(48-60)-P10 induces apoptosis specific to the inclusion of the wild type PIP box containing sequence. Colocalization of Tat(48-60)-P10 with nuclear PCNA was observed by immunofluorescence analysis, supporting the hypothesis that cytotoxicity is potentially related to disruption of nuclear PCNA function. The U251 and U373 glioma cell lines exhibited particular sensitivity to the construct.