RESUMEN
Voltage-gated sodium (NaV) channels are transmembrane proteins that play a critical role in electrical signaling in the nervous system and other excitable tissues. µ-Conotoxins are peptide toxins from the venoms of marine cone snails (genus Conus) that block NaV channels with nanomolar potency. Most species of the subgenera Textilia and Afonsoconus are difficult to acquire; therefore, their venoms have yet to be comprehensively interrogated for µ-conotoxins. The goal of this study was to find new µ-conotoxins from species of the subgenera Textilia and Afonsoconus and investigate their selectivity at human NaV channels. Using RNA-seq of the venom gland of Conus (Textilia) bullatus, we identified 12 µ-conotoxin (or µ-conotoxin-like) sequences. Based on these sequences we designed primers which we used to identify additional µ-conotoxin sequences from DNA extracted from historical specimens of species from Textilia and Afonsoconus. We synthesized six of these µ-conotoxins and tested their activity on human NaV1.1-NaV1.8. Five of the six synthetic peptides were potent blockers of human NaV channels. Of these, two peptides (BuIIIB and BuIIIE) were potent blockers of hNaV1.3. Three of the peptides (BuIIIB, BuIIIE and AdIIIA) had submicromolar activity at hNaV1.7. This study serves as an example of the identification of new peptide toxins from historical DNA and provides new insights into structure-activity relationships of µ-conotoxins with activity at hNaV1.3 and hNaV1.7.
Asunto(s)
Conotoxinas , Caracol Conus , Toxinas Biológicas , Humanos , Animales , Conotoxinas/farmacología , Proteínas de la Membrana , Canales de Sodio/genéticaRESUMEN
Background Following neonatal resuscitation program (NRP) training, decay in clinical skills can occur. Simulation-based deliberate practice (SBDP) has been shown to maintain NRP skills to a variable extent. Our study objectives were (a) to determine whether a single 30 min simulation-based intervention that incorporates SBDP and mastery learning (ML) can effectively restore skills and prevent skill decay and (b) to compare different timing options. Methods Following NRP certification, pediatric residents were randomly assigned to receive a video-recorded baseline assessment plus SBDP-ML refresher education at between 6 and 9 months (early) or between 9 and 12 months (late). One year following initial certification, participants had repeat skill retention videotaped evaluations. Participants were scored by blinded NRP instructors using validated criteria scoring tools and assigned a global performance rating score (GRS). Results Twenty-seven participants were included. Residents in both early and late groups showed significant skill decay 7 and 10 months after initial NRP. SBDP-ML booster sessions significantly improved participants' immediate NRP performance scores (p<0.001), which persisted for 2 months, but were again lower 4 months later. Conclusions NRP skills may be boosted to mastery levels after a short SBDP-ML intervention and do not appear to significantly decline after 2 months. Brief booster training could potentially serve as a useful supplement to traditional NRP training for pediatric residents.
Asunto(s)
Competencia Clínica/estadística & datos numéricos , Pediatría/educación , Resucitación/educación , Entrenamiento Simulado/métodos , Femenino , Humanos , Internado y Residencia , MasculinoRESUMEN
Cone snail toxins are well known blockers of voltage-gated sodium channels, a property that is of broad interest in biology and therapeutically in treating neuropathic pain and neurological disorders. Although most conotoxin channel blockers function by direct binding to a channel and disrupting its normal ion movement, conotoxin µO§-GVIIJ channel blocking is unique, using both favorable binding interactions with the channel and a direct tether via an intermolecular disulfide bond. Disulfide exchange is possible because conotoxin µO§-GVIIJ contains anS-cysteinylated Cys-24 residue that is capable of exchanging with a free cysteine thiol on the channel surface. Here, we present the solution structure of an analog of µO§-GVIIJ (GVIIJ[C24S]) and the results of structure-activity studies with synthetic µO§-GVIIJ variants. GVIIJ[C24S] adopts an inhibitor cystine knot structure, with two antiparallel ß-strands stabilized by three disulfide bridges. The loop region linking the ß-strands (loop 4) presents residue 24 in a configuration where it could bind to the proposed free cysteine of the channel (Cys-910, rat NaV1.2 numbering; at site 8). The structure-activity study shows that three residues (Lys-12, Arg-14, and Tyr-16) located in loop 2 and spatially close to residue 24 were also important for functional activity. We propose that the interaction of µO§-GVIIJ with the channel depends on not only disulfide tethering via Cys-24 to a free cysteine at site 8 on the channel but also the participation of key residues of µO§-GVIIJ on a distinct surface of the peptide.
Asunto(s)
Conotoxinas/química , Disulfuros/química , Proteínas Musculares/química , Canal de Sodio Activado por Voltaje NAV1.2/química , Bloqueadores de los Canales de Sodio/química , Canales de Sodio/química , Secuencia de Aminoácidos , Animales , Sitios de Unión , Conotoxinas/síntesis química , Cristalografía por Rayos X , Expresión Génica , Modelos Moleculares , Datos de Secuencia Molecular , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Mutación , Canal de Sodio Activado por Voltaje NAV1.2/genética , Canal de Sodio Activado por Voltaje NAV1.2/metabolismo , Unión Proteica , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Ratas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Caracoles/química , Bloqueadores de los Canales de Sodio/síntesis química , Canales de Sodio/genética , Canales de Sodio/metabolismo , Técnicas de Síntesis en Fase Sólida , Relación Estructura-ActividadRESUMEN
A cone snail venom peptide, µO§-conotoxin GVIIJ from Conus geographus, has a unique posttranslational modification, S-cysteinylated cysteine, which makes possible formation of a covalent tether of peptide to its target Na channels at a distinct ligand-binding site. µO§-conotoxin GVIIJ is a 35-aa peptide, with 7 cysteine residues; six of the cysteines form 3 disulfide cross-links, and one (Cys24) is S-cysteinylated. Due to limited availability of native GVIIJ, we primarily used a synthetic analog whose Cys24 was S-glutathionylated (abbreviated GVIIJSSG). The peptide-channel complex is stabilized by a disulfide tether between Cys24 of the peptide and Cys910 of rat (r) NaV1.2. A mutant channel of rNaV1.2 lacking a cysteine near the pore loop of domain II (C910L), was >10(3)-fold less sensitive to GVIIJSSG than was wild-type rNaV1.2. In contrast, although rNaV1.5 was >10(4)-fold less sensitive to GVIIJSSG than NaV1.2, an rNaV1.5 mutant with a cysteine in the homologous location, rNaV1.5[L869C], was >10(3)-fold more sensitive than wild-type rNaV1.5. The susceptibility of rNaV1.2 to GVIIJSSG was significantly altered by treating the channels with thiol-oxidizing or disulfide-reducing agents. Furthermore, coexpression of rNaVß2 or rNaVß4, but not that of rNaVß1 or rNaVß3, protected rNaV1.1 to -1.7 (excluding NaV1.5) against block by GVIIJSSG. Thus, GVIIJ-related peptides may serve as probes for both the redox state of extracellular cysteines and for assessing which NaVß- and NaVα-subunits are present in native neurons.
Asunto(s)
Conotoxinas/toxicidad , Disulfuros/metabolismo , Canal de Sodio Activado por Voltaje NAV1.2/metabolismo , Neuronas/metabolismo , Bloqueadores del Canal de Sodio Activado por Voltaje/toxicidad , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Cromatografía Líquida de Alta Presión , Conotoxinas/genética , Conotoxinas/metabolismo , Cisteína/metabolismo , Cartilla de ADN/genética , ADN Complementario/genética , Datos de Secuencia Molecular , Oocitos/metabolismo , Técnicas de Placa-Clamp , Ratas , Análisis de Secuencia de ADN , Espectrometría de Masas en Tándem , Bloqueadores del Canal de Sodio Activado por Voltaje/metabolismoRESUMEN
Conantokins are short peptides derived from the venoms of marine cone snails that act as antagonists of the N-methyl-D-aspartate (NMDA) receptor family of excitatory glutamate receptors. These peptides contain γ-carboxyglutamic acid residues typically spaced at i,i+4 and/or i,i+7 intervals, which by chelating divalent cations induce and stabilize helical conformation of the peptide. Introduction of a dicarba bridge (or a staple) can covalently stabilize peptide helicity and improve its pharmacological properties. To test the hypothesis that stapling can effectively replace γ-carboxyglutamic acid residues in stabilizing the helical conformation of conantokins, we designed, synthesized, and characterized several stapled analogs of conantokin G (conG), with varying connectivities in terms of staple length and location along the face of the α-helix. NMR studies confirmed that the ring-closing metathesis reaction yielded a single product with the Z configuration of the olefinic bond. Based on circular dichroism and molecular modeling, the stapled analogs exhibited significantly enhanced helicity compared with the native peptide in a metal-free environment. Stapling i,i+4 was benign with respect to effects on in vitro and in vivo pharmacological properties. One analog, namely conG[11-15,S(i,i+4)S(8)], blocked NR2B-containing NMDA receptors with IC(50) = 0.7 µm and provided significant protection in the 6-Hz psychomotor model of pharmacoresistant epilepsy in mice. Remarkably, unlike native conG, conG[11-15,S(i,i+4)S(8)] produced no behavioral motor toxicity. Our results extend the applications of peptide stapling to helical peptides with extracellular targets and provide a means for engineering conantokins with improved pharmacological properties.
Asunto(s)
Ácido 1-Carboxiglutámico/química , Conotoxinas , Epilepsia/tratamiento farmacológico , Antagonistas de Aminoácidos Excitadores , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Ácido 1-Carboxiglutámico/farmacología , Animales , Conotoxinas/química , Conotoxinas/farmacología , Epilepsia/metabolismo , Antagonistas de Aminoácidos Excitadores/química , Antagonistas de Aminoácidos Excitadores/farmacología , Masculino , Ratones , Resonancia Magnética Nuclear Biomolecular , Estructura Secundaria de Proteína , Receptores de N-Metil-D-Aspartato/metabolismoRESUMEN
Hydrocarbon stapling is an effective strategy to stabilize the helical conformation of bioactive peptides. Here we describe application of stapling to anticonvulsant neuropeptides, galanin (GAL) and neuropeptide Y (NPY), that are implicated in modulating seizures in the brain. Dicarba bridges were rationally introduced into minimized analogs of GAL and NPY resulting in increased α-helical content, in vitro metabolic stability and n-octanol/water partitioning coefficient (logD). The stapled analogs retained agonist activities towards their respective receptors and suppressed seizures in a mouse model of epilepsy.
Asunto(s)
Anticonvulsivantes/química , Anticonvulsivantes/uso terapéutico , Epilepsia/tratamiento farmacológico , Galanina/análogos & derivados , Galanina/uso terapéutico , Neuropéptido Y/análogos & derivados , Neuropéptido Y/uso terapéutico , Secuencia de Aminoácidos , Animales , Anticonvulsivantes/metabolismo , Ciclización , Estabilidad de Medicamentos , Galanina/metabolismo , Masculino , Ratones , Datos de Secuencia Molecular , Neuropéptido Y/metabolismo , Estabilidad Proteica , Estructura Secundaria de Proteína , RatasRESUMEN
In the preparation of synthetic conotoxins containing multiple disulfide bonds, oxidative folding can produce numerous permutations of disulfide bond connectivities. Establishing the native disulfide connectivities thus presents a significant challenge when the venom-derived peptide is not available, as is increasingly the case when conotoxins are identified from cDNA sequences. Here, we investigate the disulfide connectivity of µ-conotoxin KIIIA, which was predicted originally to have a [C1-C9,C2-C15,C4-C16] disulfide pattern based on homology with closely related µ-conotoxins. The two major isomers of synthetic µ-KIIIA formed during oxidative folding were purified and their disulfide connectivities mapped by direct mass spectrometric collision-induced dissociation fragmentation of the disulfide-bonded polypeptides. Our results show that the major oxidative folding product adopts a [C1-C15,C2-C9,C4-C16] disulfide connectivity, while the minor product adopts a [C1-C16,C2-C9,C4-C15] connectivity. Both of these peptides were potent blockers of Na(V)1.2 (K(d) values of 5 and 230 nM, respectively). The solution structure for µ-KIIIA based on nuclear magnetic resonance data was recalculated with the [C1-C15,C2-C9,C4-C16] disulfide pattern; its structure was very similar to the µ-KIIIA structure calculated with the incorrect [C1-C9,C2-C15,C4-C16] disulfide pattern, with an α-helix spanning residues 7-12. In addition, the major folding isomers of µ-KIIIB, an N-terminally extended isoform of µ-KIIIA identified from its cDNA sequence, were isolated. These folding products had the same disulfide connectivities as µ-KIIIA, and both blocked Na(V)1.2 (K(d) values of 470 and 26 nM, respectively). Our results establish that the preferred disulfide pattern of synthetic µ-KIIIA and µ-KIIIB folded in vitro is 1-5/2-4/3-6 but that other disulfide isomers are also potent sodium channel blockers. These findings raise questions about the disulfide pattern(s) of µ-KIIIA in the venom of Conus kinoshitai; indeed, the presence of multiple disulfide isomers in the venom could provide a means of further expanding the snail's repertoire of active peptides.
Asunto(s)
Conotoxinas/farmacología , Disulfuros/química , Activación del Canal Iónico , Isomerismo , Canales de Sodio/efectos de los fármacos , Cromatografía Líquida de Alta Presión , Clonación Molecular , Conotoxinas/química , Conotoxinas/genética , Espectrometría de Masas , Resonancia Magnética Nuclear Biomolecular , Oxidación-ReducciónRESUMEN
The neuropeptides galanin (GAL), neuropeptide Y (NPY) or neurotensin (NT) exhibit anticonvulsant activities mediated by their respective receptors in the brain. To transform these peptides into potential neurotherapeutics, their systemic bioavailability and metabolic stability must be improved. Our recent studies with GAL analogs suggested that an introduction of lipoamino acids in the context of oligo-Lys residues (lipidization-cationization motif) significantly increases their penetration into the brain, yielding potent antiepileptic compounds. Here, we describe an extension of this strategy to NPY and NT. Rationally designed analogs of NPY and NT containing the lipidization-cationization motif were chemically synthesized and their physicochemical and pharmacological properties were characterized. The analogs NPY-BBB2 and NT-BBB1 exhibited increased serum stability, possessed log D > 1.1, retained high affinities toward their native receptors and produced potent antiseizure activities in animal models of epilepsy following intraperitoneal administration. Our results suggest that the combination of lipidization and cationization may be an effective strategy for improving systemic bioavailability and metabolic stability of various neuroactive peptides.
Asunto(s)
Anticonvulsivantes/farmacología , Neuropéptido Y/análogos & derivados , Neurotensina/análogos & derivados , Animales , Anticonvulsivantes/síntesis química , Barrera Hematoencefálica/efectos de los fármacos , Cationes/química , Epilepsia/tratamiento farmacológico , Lípidos/química , Neuropéptido Y/síntesis química , Neuropéptido Y/farmacología , Neurotensina/síntesis química , Neurotensina/farmacología , Ratas , Receptores de Neuropéptido Y/metabolismo , Receptores de Neurotensina/metabolismoRESUMEN
Described herein is a general approach to identify novel compounds using the biodiversity of a megadiverse group of animals; specifically, the phylogenetic lineage of the venomous gastropods that belong to the genus Conus ("cone snails"). Cone snail biodiversity was exploited to identify three new mu-conotoxins, BuIIIA, BuIIIB and BuIIIC, encoded by the fish-hunting species Conus bullatus. BuIIIA, BuIIIB and BuIIIC are strikingly divergent in their amino acid composition compared to previous mu-conotoxins known to target the voltage-gated Na channel skeletal muscle subtype Na(v)1.4. Our preliminary results indicate that BuIIIB and BuIIIC are potent inhibitors of Na(v)1.4 (average block approximately 96%, at a 1muM concentration of peptide), displaying a very slow off-rate not seen in previously characterized mu-conotoxins that block Na(v)1.4. In addition, the three new C. bullatus mu-conopeptides help to define a new branch of the M-superfamily of conotoxins, namely M-5. The exogene strategy used to discover these Na channel-inhibiting peptides was based on both understanding the phylogeny of Conus, as well as the molecular genetics of venom mu-conotoxin peptides previously shown to generally target voltage-gated Na channels. The discovery of BuIIIA, BuIIIB and BuIIIC Na channel blockers expands the diversity of ligands useful in determining the structure-activity relationship of voltage-gated sodium channels.
Asunto(s)
Biodiversidad , Conotoxinas/química , Caracol Conus/genética , Caracol Conus/fisiología , Bloqueadores de los Canales de Sodio/química , N-Acetiltransferasa de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Conotoxinas/genética , Conotoxinas/metabolismo , ADN Complementario , Venenos de Moluscos/química , Oocitos , Filogenia , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/metabolismo , XenopusRESUMEN
Disulfide-rich neurotoxins from venomous animals continue to provide compounds with therapeutic potential. Minimizing neurotoxins often results in removal of disulfide bridges or critical amino acids. To address this drug-design challenge, we explored the concept of disulfide-rich scaffolds consisting of isostere polymers and peptidic pharmacophores. Flexible spacers, such as amino-3-oxapentanoic or 6-aminohexanoic acids, were used to replace conformationally constrained parts of a three-disulfide-bridged conotoxin, SIIIA. The peptide-polymer hybrids, polytides, were designed based on cladistic identification of nonconserved loci in related peptides. After oxidative folding, the polytides appeared to be better inhibitors of sodium currents in dorsal root ganglia and sciatic nerves in mice. Moreover, the polytides appeared to be significantly more potent and longer-lasting analgesics in the inflammatory pain model in mice, when compared to SIIIA. The resulting polytides provide a promising strategy for transforming disulfide-rich peptides into therapeutics.
Asunto(s)
Analgésicos no Narcóticos/síntesis química , Conotoxinas/síntesis química , Diseño de Fármacos , Péptidos/síntesis química , Secuencia de Aminoácidos , Analgésicos no Narcóticos/química , Analgésicos no Narcóticos/farmacología , Animales , Conotoxinas/química , Conotoxinas/farmacología , Ganglios Espinales/efectos de los fármacos , Ganglios Espinales/metabolismo , Ratones , Ratones Endogámicos , Datos de Secuencia Molecular , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Dolor/tratamiento farmacológico , Dimensión del Dolor , Péptidos/química , Péptidos/farmacología , Nervio Ciático/efectos de los fármacos , Nervio Ciático/metabolismo , Bloqueadores de los Canales de Sodio/síntesis química , Bloqueadores de los Canales de Sodio/química , Bloqueadores de los Canales de Sodio/farmacologíaRESUMEN
INTRODUCTION: "Transitions to residency" programs are designed to maximize quality and safety of patient care, as medical students become residents. However, best instructional or readiness assessment practices are not yet established. We sought to study the impact of a screen-based interactive curriculum designed to prepare interns to address common clinical coverage issues (WISE OnCall) on the clinical skills demonstrated in simulation and hypothesize that performance would improve after completing the module. METHODS: Senior medical students were recruited to participate in this single group prestudy/poststudy. Students responded to a call from a standardized nurse (SN) and assessed a standardized patient (SP) with low urine output, interacted with a 45-minute WISE OnCall module on the assessment and management of oliguria, and then evaluated a different SP with low urine output of a different underlying cause. Standardized patients assessed clinical skills with a 37-item, behaviorally anchored checklist measuring clinical skills (intraclass correlation coefficient [ICC], 0.55-0.81). Standardized nurses rated care quality and safety and collaboration and interprofessional communication using a 33-item literature-based, anchored checklist (ICC, 0.47-0.52). Standardized patient and SN ratings of the same student performance were correlated (r, 0.37-0.62; P < 0.01). Physicians assessed clinical reasoning quality based on the students' patient encounter note (ICC, 0.55-0.68), ratings that did not correlate with SP and SN ratings. We compared pre-post clinical skills performance and clinical reasoning. Fifty-two medical students (31%) completed this institutional review board -approved study. RESULTS: Performance as measured by the SPs, SNs, and the postencounter note all showed improvement with mostly moderate to large effect sizes (range of Cohen's d, 0.30-1.88; P < 0.05) after completion of the online module. Unexpectedly, professionalism as rated by the SP was poorer after the module (Cohen's d, -0.93; P = 0.000). DISCUSSION: A brief computer-based educational intervention significantly improved graduating medical students' clinical skills needed to be ready for residency.
Asunto(s)
Competencia Clínica , Instrucción por Computador/métodos , Educación de Pregrado en Medicina/métodos , Toma de Decisiones Clínicas , Comunicación , Conducta Cooperativa , Curriculum , Humanos , Relaciones Interprofesionales , Oliguria/diagnóstico , Oliguria/terapia , Relaciones Médico-Paciente , Calidad de la Atención de SaludRESUMEN
We tested two alternative oxidation strategies to produce conotoxins alpha-GI and micro-PIIIA. The peptides were either reversibly immobilized on a solid support and then oxidized, or the immobilized disulfide reagent (CLEAR-OX(trade mark)) was used to oxidize the peptides. Both strategies appeared more efficient at higher peptide concentrations, consistent with pseudo-dilution effects.
Asunto(s)
Conotoxinas/química , Pliegue de Proteína , Secuencia de Aminoácidos , Disulfuros/química , Datos de Secuencia Molecular , Oxidación-ReducciónRESUMEN
Conotoxins are short, disulfide-rich peptide neurotoxins produced in the venom of predatory marine cone snails. It is generally accepted that an estimated 100,000 unique conotoxins fall into only a handful of structural groups, based on their disulfide bridging frameworks. This unique molecular diversity poses a protein folding problem of relationships between hypervariability of amino acid sequences and mechanism(s) of oxidative folding. In this study, we present a comparative analysis of the folding properties of four conotoxins sharing an identical pattern of cysteine residues forming three disulfide bridges, but otherwise differing significantly in their primary amino acid sequence. Oxidative folding properties of M-superfamily conotoxins GIIIA, PIIIA, SmIIIA and RIIIK varied with respect to kinetics and thermodynamics. Based on rates for establishing the steady-state distribution of the folding species, two distinct folding mechanisms could be distinguished: first, rapid-collapse folding characterized by very fast, but low-yield accumulation of the correctly folded form; and second, slow-rearrangement folding resulting in higher accumulation of the properly folded form via the reshuffling of disulfide bonds within folding intermediates. Effects of changing the folding conditions indicated that the rapid-collapse and the slow-rearrangement mechanisms were mainly determined by either repulsive electrostatic or productive noncovalent interactions, respectively. The differences in folding kinetics for these two mechanisms were minimized in the presence of protein disulfide isomerase. Taken together, folding properties of conotoxins from the M-superfamily presented in this work and from the O-superfamily published previously suggest that conotoxin sequence diversity is also reflected in their folding properties, and that sequence information rather than a cysteine pattern determines the in vitro folding mechanisms of conotoxins.
Asunto(s)
Conotoxinas/metabolismo , Cistina/metabolismo , Moluscos/metabolismo , Animales , Conotoxinas/genética , Cistina/genética , Moluscos/genética , Oxidación-Reducción , Pliegue de ProteínaRESUMEN
µ-Conotoxins block voltage-gated sodium channels (VGSCs) and compete with tetrodotoxin for binding to the sodium conductance pore. Early efforts identified µ-conotoxins that preferentially blocked the skeletal muscle subtype (NaV1.4). However, the last decade witnessed a significant increase in the number of µ-conotoxins and the range of VGSC subtypes inhibited (NaV1.2, NaV1.3 or NaV1.7). Twenty µ-conotoxin sequences have been identified to date and structure-activity relationship studies of several of these identified key residues responsible for interactions with VGSC subtypes. Efforts to engineer-in subtype specificity are driven by in vivo analgesic and neuromuscular blocking activities. This review summarizes structural and pharmacological studies of µ-conotoxins, which show promise for development of selective blockers of NaV1.2, and perhaps also NaV1.1,1.3 or 1.7.
Asunto(s)
Analgésicos/química , Conotoxinas/química , Bloqueadores de los Canales de Sodio/química , Canales de Sodio Activados por Voltaje/química , Analgésicos/metabolismo , Analgésicos/uso terapéutico , Animales , Conotoxinas/metabolismo , Conotoxinas/uso terapéutico , Caracol Conus/metabolismo , Dolor/tratamiento farmacológico , Dolor/patología , Isoformas de Proteínas/antagonistas & inhibidores , Isoformas de Proteínas/metabolismo , Estructura Terciaria de Proteína , Bloqueadores de los Canales de Sodio/metabolismo , Bloqueadores de los Canales de Sodio/uso terapéutico , Relación Estructura-Actividad , Canales de Sodio Activados por Voltaje/metabolismoRESUMEN
Inhibitors of the α-subunit of the voltage-gated sodium channel subtype 1.3 (NaV 1.3) are of interest as pharmacological tools for the study of neuropathic pain associated with spinal cord injury and have potential therapeutic applications. The recently described µ-conotoxin BuIIIB (µ-BuIIIB) from Conus bullatus was shown to block NaV 1.3 with submicromolar potency (Kd = 0.2 µm), making it one of the most potent peptidic inhibitors of this subtype described to date. However, oxidative folding of µ-BuIIIB results in numerous folding isoforms, making it difficult to obtain sufficient quantities of the active form of the peptide for detailed structure-activity studies. In the present study, we report the synthesis and characterization of µ-BuIIIB analogs incorporating a disulfide-deficient, diselenide-containing scaffold designed to simplify synthesis and facilitate structure-activity studies directed at identifying amino acid residues involved in NaV 1.3 blockade. Our results indicate that, similar to other µ-conotoxins, the C-terminal residues (Trp16, Arg18 and His20) are most crucial for NaV 1 blockade. At the N-terminus, replacement of Glu3 by Ala resulted in an analog with an increased potency for NaV 1.3 (Kd = 0.07 µm), implicating this position as a potential site for modification for increased potency and/or selectivity. Further examination of this position showed that increased negative charge, through γ-carboxyglutamate replacement, decreased potency (Kd = 0.33 µm), whereas replacement with positively-charged 2,4-diamonobutyric acid increased potency (Kd = 0.036 µm). These results provide a foundation for the design and synthesis of µ-BuIIIB-based analogs with increased potency against NaV 1.3.
Asunto(s)
Analgésicos/síntesis química , Conotoxinas/síntesis química , Canal de Sodio Activado por Voltaje NAV1.3/metabolismo , Selenocisteína/química , Bloqueadores del Canal de Sodio Activado por Voltaje/síntesis química , Secuencia de Aminoácidos , Sustitución de Aminoácidos , Analgésicos/química , Analgésicos/farmacología , Animales , Células Cultivadas , Conotoxinas/química , Conotoxinas/farmacología , Cistina/química , Espectroscopía de Resonancia Magnética , Potenciales de la Membrana , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , Relación Estructura-Actividad , Bloqueadores del Canal de Sodio Activado por Voltaje/química , Bloqueadores del Canal de Sodio Activado por Voltaje/farmacología , Xenopus laevisRESUMEN
The acute treatment of kidney stones (urolithiasis) addresses pain management and focuses on the effects of the morbidity associated with an obstructed renal system. Minimal fluid intake, resulting in decreased urine production and a high concentration of stone-forming salts, is a leading factor in renal calculi development. Radio-opaque calcareous stones account for 70% to 75% of renal calculi. Microscopic hematuria in the presence of acute flank pain is suggestive of renal colic, but the absence of red blood cells does not exclude urolithiasis. Furthermore, many inflammatory and infectious conditions cause hematuria, demonstrating the low specificity of urinalysis testing. The diagnostic modality of choice is a noncontrast computed tomography (CT); ultrasonography s preferred in pregnant patients and children. Combining opioids with non-steroidal anti-inflammatory drugs (NSAIDs) is the optimal evidence-based regimen to treat severe symptoms. Rapid intravenous (IV) hydration has not shown a benefit. Potentially life-threatening diagnoses including abdominal aortic aneurysm, ovarian torsion, and appendicitis may mimic renal colic and must be ruled out.
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Servicio de Urgencia en Hospital/organización & administración , Tratamiento de Urgencia , Cálculos Renales/diagnóstico , Cálculos Renales/tratamiento farmacológico , Algoritmos , Antiinflamatorios no Esteroideos/uso terapéutico , Diagnóstico Diferencial , Diagnóstico por Imagen , Femenino , Humanos , Masculino , Manejo del Dolor , Embarazo , Complicaciones del Embarazo/diagnóstico , Complicaciones del Embarazo/tratamiento farmacológico , Factores de Riesgo , Gestión de RiesgosRESUMEN
Anticonvulsant neuropeptides play an important role in controlling neuronal excitability that leads to pain or seizures. Based on overlapping inhibitory mechanisms, many anticonvulsant compounds have been found to exhibit both analgesic and antiepileptic activities. An analgesic neuropeptide W (NPW) targets recently deorphanized G-protein coupled receptors. Here, we tested the hypothesis that the analgesic activity of NPW may lead to the discovery of its antiepileptic properties. Indeed, direct administration of NPW into the brain potently reduced seizures in mice. To confirm this discovery, we rationally designed, synthesized, and characterized NPW analogues that exhibited anticonvulsant activities following systemic administration. Our results suggest that the combination of neuropeptide repositioning and engineering NPW analogues that penetrate the blood-brain barrier could provide new drug leads, not only for the treatment of epilepsy and pain but also for studying effects of this peptide on regulating feeding and energy metabolism coupled to leptin levels in the brain.
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Analgésicos/uso terapéutico , Encéfalo/efectos de los fármacos , Neuropéptidos/uso terapéutico , Ingeniería de Proteínas/métodos , Convulsiones/tratamiento farmacológico , Secuencia de Aminoácidos , Analgésicos/química , Animales , Anticonvulsivantes/química , Anticonvulsivantes/farmacología , Anticonvulsivantes/uso terapéutico , Encéfalo/fisiología , Humanos , Datos de Secuencia Molecular , Neuropéptidos/farmacología , Convulsiones/fisiopatologíaRESUMEN
Galanin modulates seizures in the brain through two galanin receptor subtypes, GalR1 and GalR2. To generate systemically active galanin receptor ligands that discriminate between GalR1 and GalR2, the GalR1-preferring analogue Gal-B2 (or NAX 5055) was rationally redesigned to yield GalR2-preferring analogues. Systematic truncations of the N-terminal backbone led to [N-Me,des-Sar]Gal-B2, containing N-methyltryptophan. This analogue exhibited 18-fold preference in binding toward GalR2, maintained agonist activity, and exhibited potent anticonvulsant activity in mice following intraperitoneal administration.
Asunto(s)
Anticonvulsivantes/síntesis química , Galanina/análogos & derivados , Galanina/síntesis química , Oligopéptidos/síntesis química , Receptor de Galanina Tipo 1/metabolismo , Receptor de Galanina Tipo 2/metabolismo , Secuencia de Aminoácidos , Animales , Anticonvulsivantes/química , Anticonvulsivantes/farmacología , Calcio/metabolismo , Galanina/química , Galanina/farmacología , Humanos , Técnicas In Vitro , Ligandos , Ratones , Datos de Secuencia Molecular , Oligopéptidos/química , Oligopéptidos/farmacología , Ensayo de Unión Radioligante , Ratas , Receptor de Galanina Tipo 1/agonistas , Receptor de Galanina Tipo 2/agonistas , Relación Estructura-ActividadRESUMEN
Introduction of lipoamino acid (LAA), Lys-palmitoyl, and cationization into a series of galanin analogues yielded systemically active anticonvulsant compounds. To study the relationship between the LAA structure and anticonvulsant activity, orthogonally protected LAAs were synthesized in which the Lys side chain was coupled to fatty acids varying in length from C(8) to C(18) or was coupled to a monodispersed polyethylene glycol, PEG(4). Galanin receptor affinity, serum stability, lipophilicity (log D), and activity in the 6 Hz mouse model of epilepsy of each of the newly synthesized analogues were determined following systemic administration. The presence of various LAAs or Lys(MPEG(4)) did not affect the receptor binding properties of the modified peptides, but their anticonvulsant activities varied substantially and were generally correlated with their lipophilicity. Our results suggest that varying the length or polarity of the LAA residue adjacent to positively charged amino acid residues may effectively modulate the antiepileptic activity of the galanin analogues.
Asunto(s)
Anticonvulsivantes/síntesis química , Ácidos Grasos/síntesis química , Galanina/análogos & derivados , Galanina/síntesis química , Lisina/análogos & derivados , Lisina/síntesis química , Secuencia de Aminoácidos , Animales , Anticonvulsivantes/química , Anticonvulsivantes/farmacología , Unión Competitiva , Química Física , Dicroismo Circular , Epilepsia/tratamiento farmacológico , Ácidos Grasos/química , Ácidos Grasos/farmacología , Galanina/química , Galanina/farmacología , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Técnicas In Vitro , Lisina/química , Lisina/farmacología , Ratones , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , Ratas , Receptor de Galanina Tipo 1/metabolismo , Receptor de Galanina Tipo 2/metabolismo , Relación Estructura-ActividadRESUMEN
The endogenous neuropeptide galanin and its associated receptors galanin receptor 1 and galanin receptor 2 are highly localized in brain limbic structures and play an important role in the control of seizures in animal epilepsy models. As such, galanin receptors provide an attractive target for the development of novel anticonvulsant drugs. Our efforts to engineer galanin analogs that can penetrate the blood-brain-barrier and suppress seizures, yielded NAX 5055 (Gal-B2), a systemically-active analog that maintains low nanomolar affinity for galanin receptors and displays a potent anticonvulsant activity. In this report, we show that NAX 5055 is active in three models of epilepsy: 1) the Frings audiogenic seizure-susceptible mouse, 2) the mouse corneal kindling model of partial epilepsy, and 3) the 6 Hz model of pharmacoresistant epilepsy. NAX 5055 was not active in the traditional maximal electroshock and subcutaneous pentylenetetrazol seizure models. Unlike most antiepileptic drugs, NAX 5055 showed high potency in the 6 Hz model of epilepsy across all three different stimulation currents; i.e., 22, 32 and 44 mA, suggesting a potential use in the treatment of pharmacoresistant epilepsy. Furthermore, NAX 5055 was found to be biologically active after intravenous, intraperitoneal, and subcutaneous administration, and efficacy was associated with a linear pharmacokinetic profile. The results of the present investigation suggest that NAX 5055 is a first-in-class neurotherapeutic for the treatment of epilepsy in patients refractory to currently approved antiepileptic drugs.