Nanoghosts: Mesenchymal Stem cells derived nanoparticles as a unique approach for cartilage regeneration

Osteoarthritis (OA) is a chronic degenerative disease, which affects the joints and is characterized by inflammation, cartilage loss and bone changes. Nowadays, there are no treatments for OA, and current therapies are focused on relieving the symptoms. As a new therapy approach, micro and nanoparticles have been extensively explored and among all the studied particles, the use of cell-membrane-based particles is expanding. Another promising approach studied to treat OA, is the use of mesenchymal stem cells (MSCs) which play an important role modulating inflammation. We developed a novel kind of MSCs' cytoplasmic-membrane-based nanoparticles, termed nano-ghosts (NGs). Retaining MSCs' surface properties and lacking cells' internal machinery allow the NGs to have immunomodulatory capacity and to be immune-evasive while not susceptible to host-induced changes. In this study, we demonstrate NGs' ability to target cartilage tissues, in vitro and in vivo, while modulating the inflammatory process. In vivo studies demonstrated NGs ability to act as an immunomodulatory drug slowing down cartilage degeneration process. Our proof-of-concept experiments show that NGs system is a versatile nano-carrier system, capable of therapeutics loading, with targeting capabilities towards healthy and inflamed cartilage cells. Our results, along with previously published data, clearly reveal the NGs system as a promising nano-carrier platform and as a potential immunomodulatory drug for several inflammation-related diseases.

Co-delivery of immunomodulators in biodegradable nanoparticles improves therapeutic efficacy of cancer vaccines

To improve the efficacy of cancer vaccines we aimed to modulate the suppressive tumor microenvironment. In this study, the potential of intratumoral immune modulation with poly (I:C), Resiquimod (R848) and CCL20 (MIP3α) was explored. Biodegradable polymeric nanoparticles were used as delivery vehicles for slow and sustained release of these drugs in the tumor area and were combined with specific immunotherapy based on therapeutic peptide vaccination in two aggressive murine carcinoma and lymphoma tumor models. Whereas nanoparticle delivery of poly (I:C) or R848 improved therapeutic efficacy, the combination with MIP3α remarkably potentiated the cancer vaccine antitumor effects. The long-term survival increased to 75-100% and the progression free survival nearly doubled on mice with established large carcinoma tumors. The potent adjuvant effects were associated with lymphoid and myeloid population alterations in the tumor and tumor-draining lymph node. In addition to a significant influx of macrophages into the tumor, the phenotype of the suppressor tumor-associated macrophages shifted towards an acute inflammatory phenotype in the tumor-draining lymph node. Overall, these data show that therapeutic cancer vaccines can be potentiated by the combined nanoparticle mediated co-delivery of poly (I:C), R848 and MIP3α, which indicates that a more favorable milieu for cancer fighting immune cells is created for T cells induced by therapeutic cancer vaccines.

pH-responsive poly(lactide-co-glycolide) nanoparticles containing near-infrared dye for visualization and hyaluronic acid for treatment of osteoarthritis

This study focuses on intra-articular (IA) drug delivery system for the treatment of knee osteoarthritis (OA). In osteoarthritic condition the synovial fluid presents pockets with lower pH environment. To take advantage of these pH differences, poly(lactic-co-glycolic acid (PLGA) nanoparticles (NPs) and pH- responsive PLGA NPs encapsulated with ammonium bicarbonate (NH₄HCO₃) were generated. The nanoparticles were loaded with hyaluronic acid (HA) as a possible model drug for OA and with near-infrared dye (NIR) that was used to visualize the NPs with molecular imaging techniques. These NPs were characterized by dynamic light scattering, transmission electron microscopy and compared in in vitro, in vivo and ex vivo experiments in the treatment of OA. The results indicate that the NPs were sufficiently small, displayed a uniform size distribution and were non-toxic both in vitro and in vivo. Both NPs treatment seem to induced a reduction in OA progression, with pH- responsive NPs showing the more pronounced effect. This is probably because the pockets of low pH environment in the synovial fluid trigger a burst release of the pH-responsive NPs. This result is corroborated by in vitro experiments since the pH- responsive NPs showed an extracellular burst release behavior and higher chondrocyte vitality than non-responsive NPs. This study demonstrates that PLGA NPs containing HA and NH₄HCO₃ are candidates for the treatment of knee OA.

The Potential of Nano-Vehicle Mediated Therapy in Vasculitis and Multiple Sclerosis

The induction of immune tolerance towards self-antigens presents as a viable future strategy in the treatment of auto-immune diseases, including vasculitis and multiple sclerosis (MS). As specific targets are currently lacking for vasculitis due to incomplete understanding of the pathologies underlying this disease, current treatment options are based on modalities that induce general immune suppression. However, many immune suppressants used in the clinic are known to display wide biodistribution and are thus often accompanied by several adverse effects. Nano-vehicles (NVs) possess the ability to overcome such limitations by enabling more specific delivery of their content through modifications with targeting moieties. In this review, we describe the latest insights in the pathology of vasculitis that may function as potential targets for NV carrier systems, allowing more specific delivery of currently used immune suppressants. In addition, we describe the existing strategies to induce artificial immune tolerance and explore the feasibility of inducing regulatory T cell (Treg) mediated tolerance for MS, possibly mediated by NVs.

Sodium influx at the outer surface of frog skin : Evaluation of different extracellular markers

The unidirectional sodium influx across the outside surface of the frog skin epithelium was measured. The method was identical to the one described by Biber and Curran [4] except that mannitol instead of inulin was used as the indicator for the amount of tracer containing test solution remaining on the surface of the skin after blotting. The space of distribution for(3)H-mannitol is about twice as large as the corresponding space for inulin after 32-sec exposure to the tracer. At a sodium concentration of 6.7MM the sodium influx determined with inulin as marker for the test solution is 0.146 μEquiv hr(-1)cm(-2) larger than the influx measured in the same preparation with mannitol. This difference increases in proportion to the sodium concentration and can be ascribed to diffusion of sodium into a space which is accessible to mannitol but not to inulin during a 30-sec interval. Hence, nearly two-thirds of the previously described linear component of the sodium influx proceeds, as was suspected previously, into a compartment which is not directly connected to net sodium transport across the skin. The nature of the remaining one-third of this linear compartment is not clear but previous experiments suggest that it is also not involved in net sodium transport.

A large-scale (19)F MRI-based cell migration assay to optimize cell therapy

Adoptive transfer of cells for therapeutic purposes requires efficient and precise delivery to the target organ whilst preserving cell function. Therefore, therapeutically applied cells need to migrate and integrate within their target tissues after delivery, e.g. dendritic cells (DCs) need to migrate to lymph nodes to elicit an antigen-specific immune response. Previous studies have shown that inappropriate cell delivery can hinder DC migration and result in insufficient immune induction. As migration can be extremely difficult to study quantitatively in vivo, we propose an in vitro assay that reproduces key in vivo conditions to optimize cell delivery and migration in vivo. Using DC migration along a chemokine gradient, we describe here a novel (19)F MR-based, large-scale, quantitative assay to measure cell migration in a three-dimensional collagen scaffold. Unlike conventional migration assays, this set-up is amenable to both large and small cell numbers, as well as opaque tissue samples and the inclusion of chemokines or other factors. We labeled primary human DCs with a (19)F label suitable for clinical use; (0.5-15) × 10(6) cells in the scaffolds were imaged sequentially, and migration was assessed using two independent methods. We found no migration with larger numbers of cells, but up to 3% with less than one million cells. Hence, we show that the cell density in cell bolus injections has a decisive impact on migration, and this may explain the limited migration observed using large cell numbers in the clinic.

Conophysin-R, a Conus radiatus venom peptide belonging to the neurophysin family

A novel Conus peptide, conophysin-R, was purified from the venom of Conus radiatus. The distinctive disulfide framework and sequence indicates that it is a member of the neurophysin peptide family. The complete sequence of the peptide is HPTKPCMYCSFGQCVGPHICCGPTGCEMGTAEANMCSEEDEDPIPCQVFGSDCALNNPDNIHGHCVADGICCVDDTCTTHLGCLThis is the first time a neurophysin-like peptide has been found in any venom. In addition, conophysin-R is the first neurophysin family member isolated and biochemically characterized from an invertebrate source.

Identification of single amino acid residues essential for the binding of lipopolysaccharide (LPS) to LPS binding protein (LBP) residues 86-99 by using an Ala-scanning library

Lipopolysaccharide binding protein (LBP) is a 60 kDa acute phase glycoprotein capable of binding to LPS of Gram-negative bacteria and facilitating its interaction with cellular receptors. This process is thought to be of great importance in systemic inflammatory reactions such as septic shock. A peptide corresponding to residues 86-99 of human LBP (LBP86-99) has been reported to bind specifically with high affinity the lipid A moiety of LPS and to inhibit the interaction of LPS with LBP. We identified essential amino acids in LBP86-99 for binding to LPS by using a peptide library corresponding to the Ala-scanning of human LBP residues 86-99. Amino acids Trp91 and Lys92 were indispensable for peptide-LPS interaction and inhibition of LBP-LPS binding. In addition, several alanine-substituted synthetic LBP-derived peptides inhibited LPS-LBP interaction. Substitution of amino acids Arg94, Lys95 and Phe98 by Ala increased the inhibitory effect. The mutant Lys95 was the most active in blocking LPS binding to LBP. These findings emphasize the importance of single amino acids in the LPS binding capacity of small peptides and may contribute to the development of new drugs for use in the treatment of Gram-negative bacterial sepsis.

Venomous cone snails: molecular phylogeny and the generation of toxin diversity

In order to investigate the generation of conotoxin diversity, delta-conotoxin sequences from nine Conus species were analyzed in the context of their phylogeny. Using a standard molecular marker, mitochondrial 16S RNA, we determined that the delta-conotoxins were derived from three distinct species clades based on the phylogenetic reconstruction of a large set (>80) of Conus species and other toxoglossate molluscs. Four different mechanisms appear to have contributed to the diversity of the delta-conotoxins analyzed: (1) Speciation: Delta-conotoxins in different species diverge from each other (the prepro regions of orthologous genes somewhat more slowly than the reference rRNA rate, the mature toxin regions significantly faster). (2) Duplication: Intraspecific delta-conotoxin divergence is initiated by gene duplication events, some of which may have predated the species itself. (3) Recombination: A novel delta-conotoxin may arise through recombination of two parental delta-contoxin genes. (4) 'Focal hypermutation': This sudden, almost saltatory change in sequence is always restricted to the mature toxin region. The first three have been recognized previously as mechanisms important for the evolution of gene families in other phylogenetic systems; the last is a remarkable, mechanistically unexplained and specialized feature of Conus peptide diversification.

Study of different coupling agents in the conjugation of a V3-based synthetic MAP to carrier proteins

The conjugation of synthetic peptides to carrier proteins is a widely used method for immunological studies. Different coupling agents have been described to form the conjugate with carrier proteins. In this paper, we demonstrate that the antibody response toward V3-based synthetic MAPs derived from HIV-1, JY1 isolate, conjugated to two different carrier proteins using either m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS) or beta-maleimidopropionic acid N-hydroxysuccinimide ester (MPS), or succinic anhydride (SA) show different behaviors. An excellent anti-JY1 response without a strong response to the coupling agent is observed in the case of succinic anhydride spacer. In contrast, MBS produces total abrogation of the antibody response with a high response toward the coupling agent.

Contryphans from Conus textile venom ducts

Contryphans are unusual Conus peptides which contain a distinctive post-translational modification, D-tryptophan or D-leucine. cDNA clones encoding new contryphans from the mollusc-hunting cone snail Conus textile were identified and the inferred mature peptides were synthesized: contryphan-Tx (Gly-Cys-Hyp-D-Trp-Gln-Pro-Tyr-Cys-NH(2)), Leu-contryphan-Tx (Cys-Val-D-Leu-Tyr-Pro-Trp-Cys-NH(2)) and contryphan R/Tx which is identical to contryphan-R [Jimenez et al., 1996. Contryphan is a D-tryptophan containing Conus peptide. J. Biol. Chem. 281, 28002-28005]. Leu-contryphan-Tx exhibits a single peak, but contryphan-Tx shows two peaks under reverse-phase high-performance liquid chromatography conditions. Ultraviolet resonance Raman spectroscopy demonstrates a difference in the D-tryptophan dihedral angle for the two contryphan-Tx equilibrium conformers. Both the sequences and in vivo effects of all contryphans isolated suggest that there are two major branches of the contryphan family.

Isolation and characterization of a novel conus peptide with apparent antinociceptive activity

Cone snails are tropical marine mollusks that envenomate prey with a complex mixture of neuropharmacologically active compounds. We report the discovery and biochemical characterization of a structurally unique peptide isolated from the venom of Conus marmoreus. The new peptide, mr10a, potently increased withdrawal latency in a hot plate assay (a test of analgesia) at intrathecal doses that do not produce motor impairment as measured by rotarod test. The sequence of mr10a is NGVCCGYKLCHOC, where O is 4-trans-hydroxyproline. This sequence is highly divergent from all other known conotoxins. Analysis of a cDNA clone encoding the toxin, however, indicates that it is a member of the recently described T-superfamily. Total chemical synthesis of the three possible disulfide arrangements of mr10a was achieved, and elution studies indicate that the native form has a disulfide connectivity of Cys1-Cys4 and Cys2-Cys3. This disulfide linkage is unprecedented among conotoxins and defines a new family of Conus peptides.

Immunogenicity comparison of a multi-antigenic peptide bearing V3 sequences of the human immunodeficiency virus type 1 with TAB9 protein in mice

The multiple antigenic peptide system (MAP) has been proposed as a novel and valuable approach for eliciting antibodies for peptides and developing synthetic vaccines. Multi-epitope polypeptides (MEP) have also been developed as an alternative to the recombinant approach for vaccines. The V3 loop from the HIV type 1 (HIV-1) external glycoprotein (gp120) contains the principal neutralization domain (PND). Antibodies against this region neutralize HIV-1 in vitro and in vivo. In this work, a novel presentation of di-epitope MAP was synthesized. A monomeric MAP carrying two identical JY1 V3 sequences as B-cell epitopes and the 830-843 region of tetanus toxoid as a T-helper cell epitope was synthesized. This basic structure was covalently linked to produce a four-JY1-branched homodimer (JY1-MAP4). Additionally, six different monomeric MAPs, bearing four copies of V3 from isolates LR150, JY1, RF, MN, BRVA and IIIB, were synthesized. These monomers were conveniently linked among themselves to produce homodimeric and heterodimeric MAPs of eight V3 branches (V3-MAP8). JY1-MAP8 elicited higher antibody titers in Balb/c mice than JY1-MAP4. The immunogenicity of two different, hexavalent V3-MAP8 mixtures and the MEP TAB9, which tandems the same six V3 sequences in a single molecule, were compared. The antibody response against the mixtures of the heterodimeric MAP showed a wider recognition pattern of the V3 region, while the homodimeric cocktail showed an intermediate pattern. Antibodies elicited by TAB9 recognized only the JY1, LR150 peptides. These results emphasize the influence of V3 epitope presentation upon the characteristics of the antibody response generated.

Agelasine F from a Philippine Agelas sp. sponge exhibits in vitro antituberculosis activity

Marine sponge samples were collected in Baler, Aurora, Philippines, and extracts were tested for in vitro antituberculosis activity. An orange Agelas sp. sponge yielded the known compound, agelasine F, which inhibited some drug resistant strains of Mycobacterium tuberculosis in vitro at concentrations as low as 3.13 micrograms/ml. Activity against M. tuberculosis residing within macrophages required concentrations of 13-22 micrograms/ml which was below the IC50 for Vero cells (34 micrograms/ml).

The spasmodic peptide defines a new conotoxin superfamily

We purified and characterized a peptide from the venom of Conus textile that makes normal mice assume the phenotype of a well-known mutant, the spasmodic mouse. This "spasmodic" peptide has 27 amino acids, including two gamma-carboxyglutamate (Gla) residues. A cDNA clone encoding the precursor for the peptide was identified; a gamma-carboxylation recognition signal sequence (gamma-CRS) is present in the -1 --> -20 region of the peptide precursor. Both the gamma-CRS and the position of the Gla residues in the mature toxin are notably different from other Gla-containing conopeptides. The spasmodic peptide has a novel disulfide framework and distinct signal sequence which together define a new P-superfamily of conopeptides. A cDNA encoding another member of the P-superfamily was identified from a different species, Conus gloriamaris.

In vitro and in vivo characterization of conantokin-R, a selective NMDA receptor antagonist isolated from the venom of the fish-hunting snail Conus radiatus

The purification, characterization, and synthesis of conantokin-R (Con-R), an N-methyl-D-aspartate (NMDA) receptor peptide antagonist from the venom of Conus radiatus, are described. With the use of well defined animal seizure models, Con-R was found to possess an anticonvulsant profile superior to that of ifenprodil and dizocilpine (MK-801). With voltage-clamp recording of Xenopus oocytes expressing heteromeric NMDA receptors from cloned NR1 and NR2 subunit RNAs, Con-R exhibited the following order of preference for NR2 subunits: NR2B approximately NR2A > NR2C >> NR2D. Con-R was without effect on oocytes expressing the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subunit GluR1 or the kainate receptor subunit GluR6. In mouse cortical neurons voltage-clamped at -60 mV, Con-R application produced a slowly developing block of inward currents evoked by 10 microM NMDA and 1 microM glycine (IC(50) = 350 nM). At 3 microM, Con-R did not affect gamma-aminobutyric acid- or kainate-evoked currents. Con-R prevented sound-induced tonic extension seizures in the Frings audiogenic seizure-susceptible mice at i.c.v. doses below toxic levels. It was also effective at nontoxic doses in CF#1 mice against tonic extension seizures induced by threshold (15 mA) and maximal (50 mA) stimulation, and it partially blocked clonic seizures induced by s.c. pentylenetetrazol. In contrast, MK-801 and ifenprodil were effective only at doses approaching (audiogenic seizures) or exceeding (electrical and pentylenetetrazol seizures) those required to produce significant behavioral impairment. These results indicate that the subtype selectivity and other properties of Con-R afford a distinct advantage over the noncompetitive NMDA antagonists MK-801 and ifenprodil. Con-R is a useful new pharmacological agent for differentiation between the anticonvulsant and toxic effects of NMDA antagonists.

Effects of Conus peptides on the behavior of mice

When different cone snail peptides are injected into the CNS of vertebrates, they elicit diverse behaviors primarily because of their selectivity for specific receptor or ion channel subtypes. The subcellular context of the highly localized targets (i.e. the presence of other cellular elements that are functionally linked to the targets of conopeptides) is another determinant of the elicited behavior. Recent studies have advanced our understanding of the mechanisms by which four conopeptides produce different behaviors in mice.

The T-superfamily of conotoxins

We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a conserved arrangement of cysteine residues (- -CC- -CC-). T-superfamily peptides were found expressed in venom ducts of all major feeding types of Conus; the results suggest that the T-superfamily will be a large and diverse group of peptides, widely distributed in the 500 different Conus species. These peptides are likely to be functionally diverse; although the peptides are small (11-17 amino acids), their sequences are strikingly divergent, with different peptides of the superfamily exhibiting varying extents of post-translational modification. Of the three peptides tested for in vivo biological activity, only one was active on mice but all three had effects on fish. The peptides that have been extensively characterized are as follows: p5a, GCCPKQMRCCTL*; tx5a, gammaCCgammaDGW(+)CCT( section sign)AAO; and au5a, FCCPFIRYCCW (where gamma = gamma-carboxyglutamate, W(+) = bromotryptophan, O = hydroxyproline, T( section sign) = glycosylated threonine, and * = COOH-terminal amidation). We also demonstrate that the precursor of tx5a contains a functional gamma-carboxylation recognition signal in the -1 to -20 propeptide region, consistent with the presence of gamma-carboxyglutamate residues in this peptide.

A novel D-leucine-containing Conus peptide: diverse conformational dynamics in the contryphan family

A Conus peptide family (the contryphans) is noteworthy because of the presence of a post-translationally modified D-amino acid in all members of the family. A new contryphan peptide, Leu-contryphan-P, was isolated from the venom of Conus purpurascens; the sequence of this peptide is: Gly-Cys-Val-D-Leu-Leu-Pro-Trp-Cys-OH. This is the first known occurrence of D-leucine in a Conus peptide. The discovery of Leu-contryphan-P suggests that there may be branches of the contryphan peptide family that diverge much more in sequence than previously anticipated. Several natural contryphans provide dramatic examples of interconversion between multiple conformational states in small constrained peptides. The contryphans that have 4-trans-hydroxyproline and D-tryptophan in positions 3 and 4, respectively, exhibit two peaks under reverse-phase HPLC conditions, indicating interconversion between two discrete conformations. However, [L-Trp4]contryphan-Sm (with L-Trp substituted for D-Trp) exhibits a single, broad peak that elutes later than the natural peptide, suggesting that D-Trp stabilizes a conformation in which hydrophobic residues are buried. Leucontryphan-P which has valine and D-leucine instead of 4-trans-hydroxyproline and D-tryptophan shows only a single peak that elutes much later than the other contryphans.

Mapping of the antigenic regions of streptokinase in humans after streptokinase therapy

Streptokinase (SK) is efficaciously used as a thrombolytic drug for the treatment of myocardial infarction. Being a bacterial protein, SK is immunogenic in humans. Therefore, resulting from SK therapy, patients become immunized and anti-SK antibody (Ab) titers rise post-treatment. High Ab titers might provoke severe immune reactions during SK therapy and neutralize SK activity, preventing effective thrombolysis. Spot synthesis combined with peptide library techniques is a useful tool for studying protein-peptide interactions on continuous cellulose membranes. Here, we report on the mapping of antigenic regions of SK using a spot-synthesized peptide library and human total sera from patients receiving SK therapy. All tested samples have high anti-SK Ab titers and most of them show significant SK neutralizing capacity. Individual variations in peptide recognition were detected. However, patients treated with SK tend, in general, to show a common regional binding pattern, including residues 1-20, 130-149, 170-189, and 390-399. This is the first study reporting the probing of a cellulose-bound set of peptides with total human sera.

Contulakin-G, an O-glycosylated invertebrate neurotensin

We have purified contulakin-G, a 16-amino acid O-linked glycopeptide (pGlu-Ser-Glu-Glu-Gly-Gly-Ser-Asn-Ala-Thr-Lys-Lys-Pro-Tyr-Ile-Leu-OH, pGlu is pyroglutamate) from Conus geographus venom. The major glycosylated form of contulakin-G was found to incorporate the disaccharide beta-D-Galp-(1-->3)-alpha-D-GalpNAc-(1-->) attached to Thr10. The C-terminal sequence of contulakin-G shows a high degree of similarity to the neurotensin family of peptides. Synthetic peptide replicates of Gal(beta-->3) GalNAc(alpha-->)Thr10 contulakin-G and its nonglycosylated analog were prepared using an Fmoc (9-fluorenylmethoxycarbonyl) protected solid phase synthesis strategy. The synthetic glycosylated con- tulakin-G, when administered intracerebroventricular into mice, was found to result in motor control-associated dysfunction observed for the native peptide. Contulakín-G was found to be active at 10-fold lower doses than the nonglycosylated Thr10 contulakin-G analog. The binding affinities of contulakin-G and the nonglycosylated Thr10 contulakin-G for a number of neurotensin receptor types including the human neurotensin type 1 receptor (hNTR1), the rat neurotensin type 1 and type 2 receptors, and the mouse neurotensin type 3 receptor were determined. The binding affinity of the nonglycosylated Thr10 contulakin-G was approximately an order of magnitude lower than that of neurotensin1-13 for all the receptor types tested. In contrast, the glycosylated form of contulakin-G exhibited significantly weaker binding affinity for all of the receptors tested. However, both contulakin-G and nonglycosylated Thr10 contulakin-G were found to be potent agonists of rat neurotensin receptor type 1. Based on these results, we conclude that O-linked glycosylation appears to be a highly unusual strategy for increasing the efficacy of toxins directed against neurotransmitter receptors.

An O-glycosylated neuroexcitatory conus peptide

We purified and characterized a novel peptide from the venom of the fish-hunting cone snail Conus striatus that inhibits voltage-gated K+ channels. The peptide, kappaA-conotoxin SIVA, causes characteristic spastic paralytic symptoms when injected into fish, and in frog nerve-muscle preparations exposed to the toxin, repetitive action potentials are seen in response to a single stimulus applied to the motor nerve. Other electrophysiological tests on diverse preparations provide evidence that is consistent with the peptide blocking K+ channels. The peptide has three disulfide bonds; the locations of Cys residues indicate that the spastic peptide may be the first and defining member of a new family of Conus peptides, the kappaA-conotoxins, which are structurally related to, but pharmacologically distinct from, the alphaA-conotoxins. This 30 AA tricyclic toxin has several characteristics not previously observed in Conus peptides. In addition to the distinctive biological and physiological activity, a novel biochemical feature is the unusually long linear N-terminal tail (11 residues) which contains one O-glycosylated serine at position 7. This is the first evidence for O-glycosylation as a posttranslational modification in a biologically active Conus peptide.

mu-Conotoxin PIIIA, a new peptide for discriminating among tetrodotoxin-sensitive Na channel subtypes

We report the characterization of a new sodium channel blocker, mu-conotoxin PIIIA(mu-PIIIA). The peptide has been synthesized chemically and its disulfide bridging pattern determined. The structure of the new peptide is: [sequence: see text] where Z = pyroglutamate and O = 4-trans-hydroxyproline. We demonstrate that Arginine-14 (Arg14) is a key residue; substitution by alanine significantly decreases affinity and results in a toxin unable to block channel conductance completely. Thus, like all toxins that block at Site I, mu-PIIIA has a critical guanidinium group. This peptide is of exceptional interest because, unlike the previously characterized mu-conotoxin GIIIA (mu-GIIIA), it irreversibly blocks amphibian muscle Na channels, providing a useful tool for synaptic electrophysiology. Furthermore, the discovery of mu-PIIIA permits the resolution of tetrodotoxin-sensitive sodium channels into three categories: (1) sensitive to mu-PIIIA and mu-conotoxin GIIIA, (2) sensitive to mu-PIIIA but not to mu-GIIIA, and (3) resistant to mu-PIIIA and mu-GIIIA (examples in each category are skeletal muscle, rat brain Type II, and many mammalian CNS subtypes, respectively). Thus, mu-conotoxin PIIIA provides a key for further discriminating pharmacologically among different sodium channel subtypes.

The contryphans, a D-tryptophan-containing family of Conus peptides: interconversion between conformers

We previously characterized contryphan-R, a D-tryptophan-containing octapeptide from the venom of Conus radiatus. In this study, we present evidence that the contryphan family of peptides is widely distributed in venoms of the fish-hunting cone snails. We purified, synthesized and characterized contryphan-Sm from Conus stercusmuscarum venom, and obtained molecular evidence for the existence of a third peptide, contryphan-P from Conus purpurascens venom ducts. The sequences of these three contryphans showed identity in seven of eight amino acids and a conserved pattern of post-translational modification. We also demonstrate that contryphan-Sm equilibrates between two distinct conformational states.

A novel post-translational modification involving bromination of tryptophan. Identification of the residue, L-6-bromotryptophan, in peptides from Conus imperialis and Conus radiatus venom

We report a novel post-translational modification involving halogenation of tryptophan in peptides recovered from the venom of carnivorous marine cone snails (Conus). The residue, L-6-bromotryptophan, was identified in the sequence of a heptapeptide, isolated from Conus imperialis, a worm-hunting cone. This peptide does not elicit gross behavioral symptoms when injected centrally or peripherally in mice. L-6-Bromotryptophan was also identified in a 33-amino acid peptide from Conus radiatus; this peptide has been shown to induce a sleep-like state in mice of all ages and is referred to as bromosleeper peptide. The sequences of the two peptides and were determined using a combination of mass spectrometry, amino acid, and chemical sequence analyses, where Pca = pyroglutamic acid, Hyp = hydroxyproline, Gla = gamma-carboxyglutamate, and Trp* = L-6-bromotryptophan. The precise structure and stereochemistry of the modified residue were determined as L-6-bromotryptophan by synthesis, co-elution, and enzymatic hydrolysis experiments. To our knowledge this is the first documentation of tryptophan residues in peptides/proteins being modified in a eukaryotic system and the first report of halogenation of tryptophan in vivo.

Bromocontryphan: post-translational bromination of tryptophan

We demonstrate that post-translational bromination of a tryptophan residue occurs in the biologically active octapeptide bromocontryphan, purified and characterized from Conus radiatus venom. Clones encoding bromocontryphan were identified from a cDNA library made from C. radiatus venom ducts. The mRNA sequence obtained predicts a prepropeptide which has the mature peptide sequence at the C-terminal end, with the L-6-bromotryptophan residue encoded by UGG, the Trp codon. These data provide the first direct evidence for post-translational bromination of a polypeptide which is translated through the normal cellular machinery. In addition to bromination, the peptide, which induces a "stiff tail" syndrome in mice, has several other modifications as shown by the sequence [Formula: See Text] in which Hyp = hydroxyproline. Asterisks indicate post-translational modifications (left to right): proteolytic cleavage at the N-terminus; hydroxylation of Pro3; epimerization of Trp4; bromination of Trp7, and C-terminal amidation. Bromocontryphan appears to have the highest density of post-translational modifications known among gene-encoded polypeptides. The overall result is a molecule which closely resembles marine natural products produced through specialized biosynthetic pathways comprising many enzyme-catalyzed steps.

Contryphan is a D-tryptophan-containing Conus peptide

In this report, we document for the first time the occurrence of D-tryptophan in a normally translated polypeptide, contryphan. The peptide, isolated from the venom of the fish-hunting marine snail Conus radiatus, produces the "stiff-tail" syndrome in mice. Characterization of the octapeptide gave the following sequence, Gly-Cys-Hyp-D-Trp-Glu-Pro-Trp-Cys-NH2 where Hyp = 4-trans-hydroxyproline. The presence of D-tryptophan in position 4 of contryphan was confirmed by chemical synthesis. The post-translational epimerization in all other D-amino acid-containing small peptides characterized previously from vertebrates and molluscan systems is in position 2.

A new family of Conus peptides targeted to the nicotinic acetylcholine receptor

In this work, a new family of Conus peptides, the alpha A-conotoxins, which target the nicotinic acetylcholine receptor, is defined. The first members of this family have been characterized from the eastern Pacific species, Conus purpurascens (the purple cone); three peptides that cause paralysis in fish were purified and characterized from milked venom. The sequence and disulfide bonding pattern of one of these, alpha A-conotoxin PIVA, is as follows: [formula: see text] where O represents trans-4-hydroxyproline. The two other peptides purified from C. purpurascens venom are the under-hydroxylated derivatives, [Pro13]alpha A-conotoxin PIVA and [Pro7,13]alpha A-conotoxin PIVA. The peptides have been chemically synthesized in a biologically active form. Both electrophysiological experiments and competition binding with alpha-bungarotoxin demonstrate that alpha A-PIVA acts as an antagonist of the nicotinic acetylcholine receptor at the postsynaptic membrane.

Delta-conotoxin GmVIA, a novel peptide from the venom of Conus gloriamaris

A novel peptide toxin, delta-conotoxin GmVIA, was purified from the venom of Conus gloriamaris, a mollusc-hunting snail. It consists of 29 amino acids, including six Cys residues: [sequence: see text] The pattern of disulfide connectivity (4-19, 12-24, and 18-29) is the same as for the omega-conotoxins, which are Ca2+ channel ligands. However, the peptide does not compete with omega-conotoxin for binding to membrane preparations from frog, rat, and chick brain. Instead, initial electrophysiological results suggest that the peptide induces action potential broadening in molluscan neurons by slowing down Na+ current inactivation. Synthetic delta-conotoxin GmVIA was prepared by solid-phase methods and appeared identical in all respects to the natural material. The chromatographic behavior of native and reduced delta-conotoxins is quite remarkable, suggesting that the disulfides form a core which forces hydrophobic residues to point out toward the solvent.

A new Conus peptide ligand for mammalian presynaptic Ca2+ channels

Voltage-sensitive Ca2+ channels that control neurotransmitter release are blocked by omega-conotoxin (omega-CgTx) GVIA from the marine snail Conus geographus, the most widely used inhibitor of neurotransmitter release. However, many mammalian synapses are omega-CgTx-GVIA insensitive. We describe a new Conus peptide, omega-CgTx-MVIIC, that is an effective inhibitor of omega-CgTx-GVIA-resistant synaptic transmission. Ca2+ channel targets that are inhibited by omega-CgTx-MVIIC but not by omega-CgTx-GVIA include those mediating depolarization-induced 45Ca2+ uptake in rat synaptosome preparations, "P" currents in cerebellar Purkinje cells, and a subset of omega-CgTx-GVIA-resistant currents in CA1 hippocampal pyramidal cells. The characterization of omega-CgTx-MVIIC by a combination of molecular genetics and chemical synthesis defines a general approach for obtaining ligands with novel receptor subtype specificity from Conus.

Conus Peptides: Phylogenetic Range of Biological Activity

The major function of the venoms of the predatory marine snails belonging to the genus Conus is to paralyze prey. Thus, the venom of each Conus species acts on receptors and ion channels of the prey; previous studies suggested much less activity on homologous receptor targets in more distant taxa. In this article, we address the question of whether some peptide components of Conus venoms ("conopeptides") have "cross-phylum" biological activity. We examined the venom of Conus textile, a mollusk-hunting Conus, using a mammalian biological activity assay. We purified a 23 amino acid "convulsant peptide" with potent activity in the mammalian CNS, even though it comes from the venom of a snail-hunting Conus species. A survey of Conus textile venom fractions indicates that, in addition to the convulsant peptide, many other components of this venom will exhibit "cross-phylum" biological activity. Conopeptides with broad-range phylogenetic specificity should be useful tools for studying the evolution of receptors and ion channels, and of nervous systems.

alpha-Conotoxins, small peptide probes of nicotinic acetylcholine receptors

alpha-Conotoxins, a family of small peptides from the venoms of the Conus marine moluscs, are selective, snake alpha-neurotoxin-competitive antagonists of the nicotinic acetylcholine receptor. A new alpha-conotoxin, SIA, has been purified, sequenced, and synthesized. Cross-linking with bivalent reagents and photoaffinity labeling of the acetylcholine receptor with alpha-conotoxin yield covalent adducts. Surprisingly, cross-linking to other subunits is considerably more efficient than to the alpha subunit. The relative efficiency of photoactivatable cross-linking to different subunits of the receptor is a function of placement of the photoactivatable group on the toxin. Since the structures of alpha-conotoxins can be solved by 2D NMR [see Pardi et al. (1989) Biochemistry 28, 5494-5508; Kobayashi et al. (1989) Biochemistry 28, 4853-4860], this family of toxins should provide a set of new ligands for probing the acetylcholine receptor with considerable precision.

Conantokin-G: a novel peptide antagonist to the N-methyl-D-aspartic acid (NMDA) receptor

Conantokin-G is a 17 amino acid peptide isolated from the venom of the fish-eating snail Conus geographus which produces hyperactivity when injected into the brains of adult mice. We show that this peptide is a selective N-methyl-D-aspartate (NMDA) antagonist based on its ability to block NMDA-induced elevation of cGMP in rat cerebellar slices in vitro (IC50 = 171 nM), but not kainic acid-induced elevations. This inhibition could not be overcome by increasing the NMDA concentration, indicating non-competitive inhibition. Conantokin-G displayed no affinity for binding sites for thienylcyclohexylpiperidine, various glutamate subclasses or those for several other neurotransmitters/neuromodulators. This peptide, however, enhanced [3H]glycine binding to rat forebrain membranes but not to spinal cord membranes. The activity profile of the peptide in various assays indicates that it is a novel type of non-competitive NMDA antagonist.

Diversity of Conus neuropeptides

Conus venoms contain a remarkable diversity of pharmacologically active small peptides. Their targets are ion channels and receptors in the neuromuscular system. The venom of Conus geographus contains high-affinity peptides that act on voltage-sensitive calcium channels, sodium channels, N-methyl-D-aspartate (NMDA) receptors, acetylcholine receptors, and vasopressin receptors; many more peptides with still uncharacterized receptor targets are present in this venom. It now seems that the Conus species (approximately 500 in number) will each use a distinctive assortment of peptides and that the pharmacological diversity in Conus venoms may be ultimately comparable to that of plant alkaloids or secondary metabolites of microorganisms. The cone snails may generate this diverse spectrum of venom peptides by a "fold-lock-cut" synthetic pathway. These peptides are specific enough to discriminate effectively between closely related receptor subtypes and can be used for structure-function correlations.

Conantokin-T. A gamma-carboxyglutamate containing peptide with N-methyl-d-aspartate antagonist activity

Conantokin-T, a 21-amino acid peptide which induces sleep-like symptoms in young mice was purified from the venom of the fish-hunting cone snail, Conus tulipa. The amino acid sequence of the peptide was determined and verified by chemical synthesis. The peptide has 4 residues of the modified amino acid, gamma-carboxyglutamate (Gla). The sequence of the peptide is: Gly-Glu-Gla-Gla-Tyr-Gln-Lys-Met-Leu-Gla-Asn-Leu-Arg-Gla-Ala-Glu-Val-Lys- Lys-Asn-Ala-NH2. Conantokin-T inhibits N-methyl-D-aspartate (NMDA) receptor-mediated calcium influx in central nervous system neurons. This observation suggests that like conantokin-G (a homologous Conus peptide with recently identified NMDA antagonist activity) conantokin-T has NMDA antagonist activity. A sequence comparison of conantokins-T and -G identifies the 4 Gla residues and the N-terminal dipeptide sequence as potential key elements for the biological activity of this peptide.

Constant and hypervariable regions in conotoxin propeptides

Conotoxins are small cysteine rich peptides found in the venom of the predatory cone snails (Conus) which have prove to be useful high affinity ligands for various receptors and ion channels. The first cloning data for conotoxins, reported here, were obtained for the King-Kong peptide, a 27 amino acid conotoxin found in the venom of the cloth-of-gold cone, Conus textile. Analysis of cDNA clones of the King-Kong peptide revealed a family of related toxin transcripts. Three different propeptide cDNA sequences were obtained; only one of these encoded sequence for the King-Kong peptide. The other cDNA sequences encoded two different peptides (KK-1 and KK-2). When the predicted propeptide sequences are compared, well defined conserved and hypervariable regions can be identified. The hypervariable regions comprise four regions between Cys residues in the final peptide toxins; the remainder of the propeptide sequences, i.e. the excised N-terminal regions and the disulfide bonded Cys residues, are highly conserved. We suggest that the conserved regions may direct the formation of a specific disulfide configuration in the King-Kong family of conotoxins.

mu-conotoxin GIIIA, a peptide ligand for muscle sodium channels: chemical synthesis, radiolabeling, and receptor characterization

The peptide conotoxin GIIIA from Conus geographus L. venom, which specifically blocks sodium channels in muscle, has been synthesized by a solid-phase method. The three disulfide bridges were formed by air oxidation. After HPLC purification, the synthetic product was shown to be identical with the native conotoxin GIIIA from Conus geographus. A high specific activity, 125I derivative of mu-conotoxin was prepared and used for binding assays to the Na channel from Electrophorus electric organ. Specific binding could be abolished by competition with tetrodotoxin. The radiolabeled toxin was specifically cross-linked to the Na channel. These studies demonstrate that mu-conotoxin GIIIA can be used to define the guanidinium toxin binding site and will be a useful ligand for understanding functionally important differences between Na channel subtypes.

A molluscivorous Conus toxin: conserved frameworks in conotoxins

We purified and characterized a 27 amino acid toxin from a snail-hunting Conus venom, Conus textile. This toxin causes convulsive-like activity in snails and causes subordinate lobsters to assume an exaggerated dominant posture. The sequence of this peptide is Trp-Cys-Lys-Gln-Ser-Gly-Glu-Met-Cys-Asn-Leu-Leu-Asp-Gln-Asn-Cys-Cys-Asp- Gly-Tyr-Cys-Ile-Val-Leu-Val-Cys-Thr. The sequence was confirmed by determining the nucleotide sequence of a cDNA clone coding for the peptide. The conservation of Cys residues compared to the omega-conotoxins from piscivorous Conus venom suggests that toxins from different cone venoms may use only a few "Cys-motifs" as conserved structural backbones for targeting to a variety of receptors in different animals.

Phylogenetic specificity of cholinergic ligands: alpha-conotoxin SI

The alpha-conotoxins are small peptide neurotoxins from the venom of fish-hunting cone snails which block nicotinic acetylcholine receptors (nAChRs). We describe the purification, characterization, and chemical synthesis of a new alpha-conotoxin from Conus striatus, alpha-conotoxin SI. In contrast to other AChR ligands, alpha-SI discriminates between different vertebrate nAChRs. The sequence of alpha-conotoxin SI is Ile-Cys-Cys-Asn-Pro5-Ala-Cys-Gly-Pro-Lys10-Tyr-Ser-Cys-NH2. This sequence was confirmed by chemical synthesis. A des-Ile-alpha-SI derivative was also synthesized and is biologically active. Although alpha-conotoxin SI is highly homologous to previously described alpha-conotoxins, it has one noteworthy sequence feature which may account for its novel biological specificity. In all other alpha-conotoxins, there is a positively charged amino acid at residue 9; in alpha-conotoxin SI, this is replaced by proline. The discovery that different alpha-conotoxins can vary by orders of magnitude in their apparent affinity for different vertebrate receptors demonstrates that alpha-conotoxins will be useful probes for investigating phylogenetic differences between vertebrate nAChRs.

Total synthesis and further characterization of the gamma-carboxyglutamate-containing "sleeper" peptide from Conus geographus venom

The total synthesis of the Gla-containing "sleeper" peptide (Gly-Glu-Gla-Gla-Leu-Gln-Gla-Asn-Gln-Gla-Leu-Ile-Arg-Gla-Lys-Ser-Asn-NH2 ) from Conus geographus is described. A new strategy for the synthesis of acid-sensitive peptide amides was developed, which allowed complete deprotection and cleavage of the L-gamma-carboxyglutamate-containing peptide from the 2,4-dimethoxybenzhydrylamine resin. Synthetic sleeper peptide, after preparative high-performance liquid chromatography (HPLC) purification, was shown to be identical with the native peptide by all criteria (coelution experiments of HPLC, sequence analysis, and biological activity). In addition, a developmental switch in the behavioral symptoms induced by the peptide after intracerebral administration in mice was documented. At low doses of the peptide (4-30 pmol/g), a sleeplike state was induced in mice under 2 weeks old; in contrast, older mice became markedly hyperactive. It is proposed that, in the presence of Ca2+, the sleeper peptide assumes an alpha-helical configuration in which all the gamma-carboxyglutamate residues are located on the same side of the alpha-helix.

Invertebrate vasopressin/oxytocin homologs. Characterization of peptides from Conus geographus and Conus straitus venoms

The vasopressin-oxytocin family of peptides is of very ancient lineage, found in organisms as diverse as hydra and man. Although these peptides have been intensively studied in vertebrates, the presumably more extensive invertebrate series was defined primarily by immunological methods. In this report, we describe the purification and structures of two peptides of the vasopressin-oxytocin family from molluscs ("Conopressins"), which were found in the venom of fish-hunting marine snails of the genus Conus. The biological activity observed when the two snail peptides are injected intracerebrally into mice is very similar to that elicited by the vertebrate neurohypophyseal hormones and presumably reflects their actions upon a common receptor in the brain. The sequences of the purified peptides reveal unique features not found in the vertebrate peptide series, most notably an additional positive charge. These are the first members of the invertebrate series of the vasopressin-oxytocin family to be characterized biochemically. The sequences of these peptides are: from Conus geographus venom, Lys-conopressin-G, Cys-Phe-Ile-Arg-Asn-Cys-Pro-Lys-Gly-NH2; and from Conus striatus venom, Arg-conopressin-S, Cys-Ile-Ile-Arg-Asn-Cys-Pro-Arg-Gly-NH2.

Transmitter release from presynaptic terminals of electric organ: inhibition by the calcium channel antagonist omega Conus toxin

Cholinergic synaptosomes from electroplax of the ray Ommata discopyge release both ATP and ACh when depolarized with high K+ concentration in the presence of Ca2+. Others have shown that the ATP and ACh are released in the molar ratio found in isolated synaptic vesicles. Thus, it is assumed that the release of ATP reflects exocytosis of synaptic vesicles, and that transmitter release can be indirectly monitored by assaying ATP release. We present further evidence for this assumption and examine the effects of presynaptic neurotoxins on this ATP release. As expected for transmitter release, we find that depolarization-evoked ATP release is supported by Sr2+ and Ba2+ and is inhibited by the Ca channel antagonists Co2+ and Mn2+. Likewise, the presynaptic toxins omega-CmTX and omega-CgTX, omega peptides from the venom of the marine snails Conus magus and Conus geographus, respectively, inhibit 80% of the depolarization-evoked ATP release. Half-maximal inhibition of ATP release occurs with approximately 0.5 microM of either toxin. The toxins' effects are reversible, and when toxin is washed away, the time dependence of recovery of release is approximately first order and half complete within 40 min with omega-CmTX and 15 min with omega-CgTX. The Ca2+ ionophore A23187 induces Ca2+-dependent ATP release from resting synaptosomes. As would be expected of a Ca channel antagonist, omega-CmTX does not affect this ionophore-induced release. Leptinotarsin-d (LPTd), a putative Ca channel agonist from the Colorado potato beetle, evokes Ca2+-dependent ATP release from resting synaptosomes. omega-CmTX does not block LPTd-evoked release of ATP, which suggests that omega-CmTX and LPTd act at different sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Omega-conotoxin: direct and persistent blockade of specific types of calcium channels in neurons but not muscle

Blockade of Ca2+ channels by omega-conotoxin GVIA, a 27 amino acid peptide from the venom of the marine snail Conus geographus, was investigated with patch-clamp recordings of whole-cell and unitary currents in a variety of cell types. In dorsal root ganglion neurons, the toxin produces persistent block of L- and N-type Ca2+ channels but only transiently inhibits T-type channels. Its actions appear to be neuron-specific, since it blocks high-threshold Ca2+ channels in sensory, sympathetic, and hippocampal neurons of vertebrates but not in cardiac, skeletal, or smooth muscle cells. Block occurs through direct interaction of the toxin with an external site closely associated with the Ca2+ channel, without apparent involvement of a second messenger or dependence on channel gating. The tissue and channel-type specificity and the directness and slow reversibility of the block are features that favor use of omega-conotoxin as a tool for purifying particular neuronal Ca2+ channels and defining their physiological function.

Neuronal calcium channel antagonists. Discrimination between calcium channel subtypes using omega-conotoxin from Conus magus venom

The omega-conotoxins from the venom of fish-hunting cone snails are probably the most useful of presently available ligands for neuronal Ca channels from vertebrates. Two of these peptide toxins, omega-conotoxins MVIIA and MVIIB from the venom of Conus magus, were purified. The amino acid sequences show significant differences from omega-conotoxins from Conus geographus. Total synthesis of omega-conotoxin MVIIA was achieved, and biologically active radiolabeled toxin was produced by iodination. Although omega-conotoxins from C. geographus (GVIA) and C. magus (MVIIA) appear to compete for the same sites in mammalian brain, in amphibian brain the high-affinity binding of omega-conotoxin MVIIA has narrower specificity. In this system, it is demonstrated that a combination of two omega-conotoxins can be used for biochemically defining receptor subtypes and suggested that these correspond to subtypes of neuronal Ca2+ channels.