RESUMO
Incorporation of noncanonical amino acids (ncAAs) can endow proteins with novel functionalities, such as crosslinking or fluorescence. In ion channels, the function of these variants can be studied with great precision using standard electrophysiology, but this approach is typically labor intensive and low throughput. Here, we establish a high-throughput protocol to conduct functional and pharmacological investigations of ncAA-containing human acid-sensing ion channel 1a (hASIC1a) variants in transiently transfected mammalian cells. We introduce 3 different photocrosslinking ncAAs into 103 positions and assess the function of the resulting 309 variants with automated patch clamp (APC). We demonstrate that the approach is efficient and versatile, as it is amenable to assessing even complex pharmacological modulation by peptides. The data show that the acidic pocket is a major determinant for current decay, and live-cell crosslinking provides insight into the hASIC1a-psalmotoxin 1 (PcTx1) interaction. Further, we provide evidence that the protocol can be applied to other ion channels, such as P2X2 and GluA2 receptors. We therefore anticipate the approach to enable future APC-based studies of ncAA-containing ion channels in mammalian cells.
Assuntos
Canais Iônicos Sensíveis a Ácido/química , Canais Iônicos Sensíveis a Ácido/farmacologia , Aminoácidos/química , Canais Iônicos Sensíveis a Ácido/genética , Células HEK293 , Humanos , Peptídeos/química , Venenos de Aranha/química , TransfecçãoRESUMO
AIMS: Dermatology treatments require adherence for safe and effective use. Real-world healthcare databases can reveal drug utilization patterns and uncover inappropriate or unexpected use. This study aimed to analyse dermatology drug utilization patterns using epidemiological and inequality measures, leveraging Danish nationwide registries. It also assessed the feasibility of this method for detecting aberrant drug use. METHODS: We formed a 2019 cohort of all patients treated for skin conditions through Danish healthcare registries. We calculated prevalence, incidence rates and treatment duration for dermatological drugs. Inequality in drug utilization was assessed using Lorenz curves, Gini coefficients and other measures. RESULTS: The study encompassed 1 021 255 patients using 94 dermatology drugs. Most usage aligned with 'expected clinical use', but we detected inequality, with some drugs having high Gini coefficients and disproportionate consumption by the top percentile of users. Notable findings included potential inappropriate antibiotic use, excessive topical corticosteroid use and unexpected drug use duration. CONCLUSIONS: In Denmark, dermatology drugs are used primarily as anticipated, with minimal unexpected patterns. Specific follow-up is required to draw conclusions about inappropriate use. This approach demonstrates broad applicability for screening aberrant drug utilization.
Assuntos
Fármacos Dermatológicos , Sistema de Registros , Humanos , Dinamarca/epidemiologia , Feminino , Masculino , Pessoa de Meia-Idade , Adulto , Fármacos Dermatológicos/uso terapêutico , Idoso , Dermatopatias/tratamento farmacológico , Dermatopatias/epidemiologia , Dermatopatias/diagnóstico , Uso de Medicamentos/estatística & dados numéricos , Prescrição Inadequada/estatística & dados numéricos , Padrões de Prática Médica/estatística & dados numéricos , Adulto Jovem , Adolescente , Idoso de 80 Anos ou maisRESUMO
BACKGROUND: Inappropriate use of medicines may have critical consequences from individual, public health, and economic perspectives. Discovering wrongful medicine use may require intentional surveillance or screening. OBJECTIVES: The objectives of this study were to: (i) apply and evaluate the waiting time distribution (WTD) method as a screening tool for identifying aberrant drug use and (ii) evaluate the nationwide use of Dermatology drugs in Denmark for signals of aberrant drug use. METHOD: Dermatology drug use data from the Danish nationwide healthcare registries from 2018 to 2020 were used to produce WTDs that were analyzed for drug use patterns. The method provides estimates of the prevalence and incidence and enables estimation of mean treatment duration, drug relapse, and unexpected drug prescribing. RESULTS: The study included 2 027 889 individual drug users and analyzed 6 141 449 prescriptions. The analysis included approximately 100 dermatology drugs and drug categories and produced 56 WTD drug curves. The WTD patterns and epidemiological estimates confirmed that most drugs are used as intended and revealed few unexpected patterns for further investigation. Three unexpected findings were identified concerning (i) short-term use that would entail suboptimal clinical efficiency for minoxidil, (ii) sub-optimal use of topical tacrolimus, and (iii) potential undesirable increase in short-course doxycycline treatments. CONCLUSION: In Denmark, dermatology drugs are predominantly used as expected, with few unexpected use patterns identified. Targeted specific follow-up on the identified signals is necessary for conclusions about inappropriate use. The findings suggest that the WTD method is applicable for screening for aberrant drug use.
Assuntos
Dermatologia , Humanos , Listas de Espera , Prescrições de Medicamentos , Uso de Medicamentos , Dinamarca/epidemiologia , Padrões de Prática MédicaRESUMO
BACKGROUND: Recently, in an open pilot study, we found up to two years, a potential pain-relieving effect of intra-articular gold micro-particles using the patient's synovial fluid for patients with knee osteoarthritis (KOA). During the study the excluded group of patients, due to multisite pain, co-morbidities, and other exclusion criteria., received intra-articular gold micro-particles using hyaluronic acid,. We aimed to identify if pre-treatment characteristics influence the global outcome two years after intra-articular treatment for painful KOA with gold microparticles using hyaluronic acid. METHODS: Using hyaluronic acid as the carrier, 136 patients with KOA received intraarticular injections with 20 mg gold microparticles (72.000 particles, 20-40 µm in diameter). In the analysis, we included the Global Rating of Change Scale, Pain Detect Questionnaire (PDQ), Body Mass Index (BMI), and Kellgren & Lawrence score at the inclusion, Western Ontario, and McMaster Universities Osteoarthritis Index (WOMAC) sub-scores for pain, stiffness, and function at inclusion and two years. RESULTS: On the Global Rating Change Scale, 69.1% of patients reported a positive effect, 28.7% no effect, and 2.2% worse. PDQ and the three WOMAC subscores all improved at two years of follow-up. PDQ ≥ 13 (P = 0.028), BMI (P = 0.022) and Kellgren & Lawrence grade 4 (P = 0.028) at inclusion reduced the effect with a minor odds ratio compared to the baseline effect of treatment (P = 0.025). WOMAC subscores at inclusion did not influence the outcome (P > 0.5). CONCLUSIONS: Severe osteoarthritis, obesity, and neuropathic pain, reduced the effect of intra-articular gold microparticles for knee OA. TRIAL REGISTRATION: The study followed the principles of the Declaration of Helsinki and was approved by the local ethics committee of the North Denmark Region by 27/07/2016 (N-20,160,045). The regional data protection agency approved the project by 06/07/2016 (2008-58-0028, ID 2016 - 116) and registered in ClinicalTrial.Gov by 04/01/2018 (NCT03389906).
Assuntos
Neuralgia , Osteoartrite do Joelho , Humanos , Ácido Hialurônico , Injeções Intra-Articulares , Osteoartrite do Joelho/terapia , Projetos Piloto , Resultado do TratamentoRESUMO
The Na+,K+-ATPase generates electrochemical gradients of Na+ and K+ across the plasma membrane via a functional cycle that includes various phosphoenzyme intermediates. However, the structure and function of these intermediates and how metal fluorides mimick them require further investigation. Here, we describe a 4.0 Å resolution crystal structure and functional properties of the pig kidney Na+,K+-ATPase stabilized by the inhibitor beryllium fluoride (denoted E2-BeFx). E2-BeFx is expected to mimic properties of the E2P phosphoenzyme, yet with unknown characteristics of ion and ligand binding. The structure resembles the E2P form obtained by phosphorylation from inorganic phosphate (Pi) and stabilized by cardiotonic steroids, including a low-affinity Mg2+ site near ion binding site II. Our anomalous Fourier analysis of the crystals soaked in Rb+ (a K+ congener) followed by a low-resolution rigid-body refinement (6.9-7.5 Å) revealed preocclusion transitions leading to activation of the dephosphorylation reaction. We show that the Mg2+ location indicates a site of initial K+ recognition and acceptance upon binding to the outward-open E2P state after Na+ release. Furthermore, using binding and activity studies, we find that the BeFx-inhibited enzyme is also able to bind ADP/ATP and Na+. These results relate the E2-BeFx complex to a transient K+- and ADP-sensitive E∗P intermediate of the functional cycle of the Na+,K+-ATPase, prior to E2P.
Assuntos
Berílio , Glicosídeos Cardíacos , Fluoretos , Rim , ATPase Trocadora de Sódio-Potássio , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Berílio/química , Glicosídeos Cardíacos/química , Fluoretos/química , Rim/enzimologia , Cinética , Fosfatos/metabolismo , Fosforilação , Domínios Proteicos , ATPase Trocadora de Sódio-Potássio/antagonistas & inibidores , ATPase Trocadora de Sódio-Potássio/química , SuínosRESUMO
The sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) performs active reuptake of cytoplasmic Ca2+ and is a major regulator of cardiac muscle contractility. Dysfunction or dysregulation of SERCA2a is associated with heart failure, while restoring its function is considered as a therapeutic strategy to restore cardiac performance. However, its structure has not yet been determined. Based on native, active protein purified from pig ventricular muscle, we present the first crystal structures of SERCA2a, determined in the CPA-stabilized E2-AlF4- form (3.3 Å) and the Ca2+-occluded [Ca2]E1-AMPPCP form (4.0 Å). The structures are similar to the skeletal muscle isoform SERCA1a pointing to a conserved mechanism. We seek to explain the kinetic differences between SERCA1a and SERCA2a. We find that several isoform-specific residues are acceptor sites for post-translational modifications. In addition, molecular dynamics simulations predict that isoform-specific residues support distinct intramolecular interactions in SERCA2a and SERCA1a. Our experimental observations further indicate that isoform-specific intramolecular interactions are functionally relevant, and may explain the kinetic differences between SERCA2a and SERCA1a.
Assuntos
Coração/fisiologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/química , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Sequência de Aminoácidos , Animais , Modelos Moleculares , Simulação de Dinâmica Molecular , Conformação Proteica , Processamento de Proteína Pós-Traducional , Homologia de Sequência , SuínosRESUMO
AIM: To investigate changes in the pattern of drugs used to treat type 2 diabetes in Denmark from 2005 to 2021. MATERIALS AND METHODS: A nationwide, population-based drug utilization study based on medical databases covering the Danish population was conducted. We assessed incident and prevalent use patterns among all 441 205 individuals initiating at least one non-insulin, glucose-lowering drug. RESULTS: The rate of new users of non-insulin, glucose-lowering drugs increased from 2005, peaked in 2011, decreased to stable levels during 2013 to 2019, then increased dramatically during 2020-2021. The prevalence of use increased from 2.1% (in 2005) to 5.0% (in 2021) of the entire adult population. In 2021, metformin comprised 39% of all glucose-lowering drug consumption, followed by insulin (17%), sodium-glucose co-transporter-2 inhibitors (SGLT-2is) (17%), glucagon-like peptide-1 receptor agonists (GLP-1RAs) (16%) and dipeptidyl peptidase-4 inhibitors (7.5%). Overall, 56% of users were on monotherapy, 28% used dual therapy, while 13% and 2.8% used three and four drug classes, respectively. Both the intensity and diversity of therapies increased substantially over time, with 15 different treatment regimens each covering more than 1% of users in 2021. General practitioners prescribed 88% of all glucose-lowering drugs. Marked shifts towards GLP-1RA initiation by general practitioners and SGLT-2i initiation by specialists were observed, and changing user profiles suggested increasing use for non-diabetes indications. CONCLUSIONS: The rate of new users of non-insulin, glucose-lowering drugs has increased in recent years and the prevalence of glucose-lowering drug use increases steadily. Glucose-lowering drugs are mainly prescribed by general practitioners, and the intensity, diversity and indications of glucose-lowering treatment are increasing.
Assuntos
Diabetes Mellitus Tipo 2 , Inibidores da Dipeptidil Peptidase IV , Inibidores do Transportador 2 de Sódio-Glicose , Adulto , Humanos , Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Glucose/uso terapêutico , Receptor do Peptídeo Semelhante ao Glucagon 1/agonistas , Inibidores do Transportador 2 de Sódio-Glicose/uso terapêutico , Inibidores da Dipeptidil Peptidase IV/uso terapêutico , Insulina/uso terapêutico , Insulina Regular Humana/uso terapêutico , DinamarcaRESUMO
Phosphorylation-type (P-type) ATPases are ubiquitous primary transporters that pump cations across cell membranes through the formation and breakdown of a phosphoenzyme intermediate. Structural investigations suggest that the transport mechanism is defined by conformational changes in the cytoplasmic domains of the protein that are allosterically coupled to transmembrane helices so as to expose ion binding sites to alternate sides of the membrane. Here, we have used single-molecule fluorescence resonance energy transfer to directly observe conformational changes associated with the functional transitions in the Listeria monocytogenes Ca2+-ATPase (LMCA1), an orthologue of eukaryotic Ca2+-ATPases. We identify key intermediates with no known crystal structures and show that Ca2+ efflux by LMCA1 is rate-limited by phosphoenzyme formation. The transport process involves reversible steps and an irreversible step that follows release of ADP and extracellular release of Ca2+.
Assuntos
Trifosfato de Adenosina/metabolismo , ATPases Transportadoras de Cálcio/química , ATPases Transportadoras de Cálcio/metabolismo , Transferência Ressonante de Energia de Fluorescência , Listeria monocytogenes/enzimologia , Imagem Individual de Molécula , Difosfato de Adenosina/metabolismo , Sítios de Ligação , Cálcio/metabolismo , Cinética , Modelos Moleculares , Fosforilação , Conformação ProteicaRESUMO
Acid-sensing ion channels (ASICs) are proton-gated cation channels that contribute to neurotransmission, as well as initiation of pain and neuronal death following ischemic stroke. As such, there is a great interest in understanding the in vivo regulation of ASICs, especially by endogenous neuropeptides that potently modulate ASICs. The most potent endogenous ASIC modulator known to date is the opioid neuropeptide big dynorphin (BigDyn). BigDyn is up-regulated in chronic pain and increases ASIC-mediated neuronal death during acidosis. Understanding the mechanism and site of action of BigDyn on ASICs could thus enable the rational design of compounds potentially useful in the treatment of pain and ischemic stroke. To this end, we employ a combination of electrophysiology, voltage-clamp fluorometry, synthetic BigDyn analogs, and noncanonical amino acid-mediated photocrosslinking. We demonstrate that BigDyn binding results in an ASIC1a closed resting conformation that is distinct from open and desensitized states induced by protons. Using alanine-substituted BigDyn analogs, we find that the BigDyn modulation of ASIC1a is primarily mediated through electrostatic interactions of basic amino acids in the BigDyn N terminus. Furthermore, neutralizing acidic amino acids in the ASIC1a extracellular domain reduces BigDyn effects, suggesting a binding site at the acidic pocket. This is confirmed by photocrosslinking using the noncanonical amino acid azidophenylalanine. Overall, our data define the mechanism of how BigDyn modulates ASIC1a, identify the acidic pocket as the binding site for BigDyn, and thus highlight this cavity as an important site for the development of ASIC-targeting therapeutics.
Assuntos
Canais Iônicos Sensíveis a Ácido/metabolismo , Dinorfinas/metabolismo , Canais Iônicos Sensíveis a Ácido/genética , Animais , Animais Geneticamente Modificados , Sítios de Ligação , Células HEK293 , Humanos , Concentração de Íons de Hidrogênio , Neurônios/metabolismo , Neuropeptídeos/metabolismo , Neuropeptídeos/fisiologia , Oócitos/metabolismo , Prótons , Xenopus laevisRESUMO
The objective of the study was to compare the use of attention deficit hyperactivity disorder (ADHD) medication among children and adolescents in Scandinavia 2010-2020. Using aggregated prescription data for individuals aged 5-19 years, we calculated annual prevalence proportions of ADHD medication (users/1000 inhabitants) for each country, overall and stratified by age and sex. Overall, use of ADHD medication increased during 2010-2020 in all countries. The increase was pronounced in Sweden reaching 35 users/1000 inhabitants in 2020 (119% increase), whereas it reached 22/1000 in Denmark and Norway (equivalent to a 38% and 16% increase, respectively). Methylphenidate was the most frequently used drug and Sweden had the highest use reaching 25/1000 in 2020 compared to 16/1000 and 18/1000 in Denmark and Norway, respectively. Lisdexamfetamine use increased steadily and was also highest in Sweden (13/1000 in 2020). In 2020, atomoxetine use was higher in Sweden (4.6/1000) and Denmark (4.5/1000) compared to Norway (2.2/1000). From 2015, use of guanfacine increased in Sweden reaching 4.4/1000 in 2020 but remained low in Denmark (0.4/1000) and Norway (0.7/1000). Use of dexamphetamine was low (ranging from 0.47 to 0.75/1000 in 2020) in the three countries. ADHD medication use was highest in Sweden across all age groups. In all countries, the prevalence was higher in males compared to females. In conclusion, use of ADHD medication among children and adolescents in Scandinavia is increasing. The prevalence of use is higher in Sweden for all drug groups compared to Norway and Denmark.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade , Estimulantes do Sistema Nervoso Central , Metilfenidato , Masculino , Feminino , Criança , Humanos , Adolescente , Transtorno do Deficit de Atenção com Hiperatividade/tratamento farmacológico , Transtorno do Deficit de Atenção com Hiperatividade/epidemiologia , Estimulantes do Sistema Nervoso Central/uso terapêutico , Metilfenidato/uso terapêutico , Cloridrato de Atomoxetina/uso terapêutico , Países Escandinavos e Nórdicos/epidemiologiaRESUMO
BACKGROUND: Long-term oral corticosteroid (OCS) treatment for severe asthma is known to cause significant adverse effects, but knowledge on effects of lower exposures in general asthma populations is limited. We aimed to explore this in a nationwide Danish asthma population. METHODS: Users of asthma medication aged 18-45â years were identified in the Danish nationwide registers during 1999-2018 and followed prospectively in an open-cohort design. Incident OCS users were matched 1:4 to nonusers by propensity scores with replacement. Associations between OCS use and incident comorbidities were examined by Cox regression. Mortality rates, causes of death and rates of unscheduled hospital visits were assessed. RESULTS: OCS users (n=30 352) had, compared with nonusers (n=121 408), an increased risk of all outcomes with evident dose-response relationships starting at cumulative doses of ≤500â mg (prednisolone-equivalent). Hazard ratios ranged from 1.24 (95% CI 1.18-1.30) for fractures to 8.53 (95% CI 3.97-18.33) for adrenal insufficiency. Depression/anxiety had the highest incidence rate difference at 4.3 (95% CI 3.6-5.0) per 1000 person-years. Asthma-specific mortality rates were generally low at 0.15 (95% CI 0.11-0.20) and 0.04 (95% CI 0.02-0.06) per 1000â person-years for OCS users and nonusers, respectively. Mortality rates and unscheduled hospital visits increased with increasing OCS exposure. CONCLUSION: The study findings should be interpreted with their observational nature in mind. However, we found that even at low cumulative exposure, OCS use in asthma management was associated with increased risk of comorbidities, mortality and unscheduled hospital visits. Effective strategies for optimising asthma control and reducing OCS use are pivotal in asthma management.
Assuntos
Antiasmáticos , Asma , Administração Oral , Corticosteroides , Antiasmáticos/efeitos adversos , Asma/epidemiologia , Humanos , Incidência , PrednisolonaRESUMO
AIMS: The Danish authorities implemented a differential rollout of the COVID-19 vaccines where individuals at high risk of COVID-19 were prioritized. We describe the temporal uptake and characteristics of COVID-19 vaccine recipients in Denmark. METHODS: Using nationwide healthcare registries, we identified all Danish residents ⩾5 years of age who received at least one dose of a COVID-19 vaccine from 27 December 2020-29 January 2022. We charted the daily number of newly vaccinated individuals and the cumulative vaccine coverage over time, stratified by vaccine type, age groups and vaccination priority groups, and described characteristics of vaccine recipients during two-month-intervals and in vaccination priority groups. RESULTS: By 29 January 2022, 88%, 86% and 64% of Danish residents ⩾5 years (n=5,562,008) had received a first, second and third dose, respectively, of a COVID-19 vaccine, most commonly the BNT162b2 vaccine (84%). Uptake ranged from 48% in 5-11-year-olds to 98% in 65-74-year-olds. Individuals vaccinated before June 2021 were older (median age 61-70 years vs 10-35 years in later periods) and had more comorbidities such as hypertension (22-28% vs 0.77-2.8% in later periods), chronic lung disease (9.4-15% vs 3.7-4.6% in later periods) and diabetes (9.3-12% vs 0.91-2.4% in later periods). CONCLUSIONS: We document substantial changes over time in, for example, age, sex and medical history of COVID-19 vaccine recipients. Though these results are related to the differential vaccine rollout in Denmark, similar findings are probable in other countries and should be considered when designing and interpreting studies on the effectiveness and safety of COVID-19 vaccines.
Assuntos
Vacinas contra COVID-19 , COVID-19 , Idoso , Vacina BNT162 , COVID-19/epidemiologia , COVID-19/prevenção & controle , Dinamarca/epidemiologia , Humanos , Pessoa de Meia-Idade , VacinaçãoRESUMO
Wastewater treatment plants (WWTP) have extensive energy processes that undermine their economic and environmental performance. In this context, the integration of wastewater treatment with other biochemical processes such as co-digestion of sludge with organic wastes, and production of value-added products at their downstream processes will shift conventional WWTPs into biorefinery platforms with better sustainability performance. The sustainability of such a biorefinery platform has been investigated herein using an economic and life cycle assessment approach. This WWTP-based biorefinery treats wastewater from Copenhagen municipality, co-digests the source-sorted organic fraction of municipal solid waste and sludge, and upgrades biogas into biomethane using a hydrogen-assisted upgrading method. Apart from bioenergy, this biorefinery also produces microbial protein (MP) using recovered nutrients from WWTP's reject water. The net environmental savings achieved in two damage categories, i.e., -1.07 × 10-2 species.yr/FU in ecosystem quality and -1.68 × 106 USD/FU in resource scarcity damage categories along with high potential windows for the further environmental profile improvements make this biorefinery platform so encouraging. Despite being promising in terms of environmental performance, the high capital expenditure and low gross profit have undermined the economic performance of the proposed biorefinery. Technological improvements, process optimization, and encouraging incentives/subsidies are still needed to make this platform economically feasible.
Assuntos
Ecossistema , Purificação da Água , Biocombustíveis/análise , Esgotos , Resíduos Sólidos/análiseRESUMO
DNA-encoded small molecule libraries (DELs) have facilitated the discovery of novel modulators of many different therapeutic protein targets. We report the first successful screening of a multimillion membered DEL inside a living cell. We demonstrate a novel method using oocytes from the South African clawed frog Xenopus laevis. The large size of the oocytes of 1 µL, or 100 000 times bigger than a normal somatic cell, permits simple injection of DELs, thus resolving the fundamental problem of delivering DELs across cell membranes for in vivo screening. The target protein was expressed in the oocytes fused to a prey protein, to allow specific DNA labeling and hereby discriminate between DEL members binding to the target protein and the endogenous cell proteins. The 194 million member DEL was screened against three pharmaceutically relevant protein targets, p38α, ACSS2, and DOCK5. For all three targets multiple chemical clusters were identified. For p38α, validated hits with single digit nanomolar potencies were obtained. This work demonstrates a powerful new approach to DEL screening, which eliminates the need for highly purified active target protein and which performs the screening under physiological relevant conditions and thus is poised to increase the DEL amenable target space and reduce the attrition rates.
Assuntos
DNA/metabolismo , Bibliotecas de Moléculas Pequenas/metabolismo , Xenopus laevis/metabolismo , Acetato-CoA Ligase/química , Acetato-CoA Ligase/genética , Acetato-CoA Ligase/metabolismo , Animais , Humanos , Proteína Quinase 14 Ativada por Mitógeno/química , Proteína Quinase 14 Ativada por Mitógeno/genética , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Oócitos/metabolismo , Bibliotecas de Moléculas Pequenas/química , Xenopus laevis/crescimento & desenvolvimentoRESUMO
Using fragment based and structure based drug discovery strategies a series of novel Sortilin inhibitors has been identified. The inhibitors are based on the N-substituted 1,2,3-triazol-4-one/ol heterocyclic template. X-ray crystallography shows that the 1,2,3-triazol-4-one/ol acts as a carboxylic acid isostere, making a bi-dentate interaction with an arginine residue of Sortilin, an interaction which has not been previously characterised for this heterocycle.
Assuntos
Proteínas Adaptadoras de Transporte Vesicular/antagonistas & inibidores , Triazóis/química , Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Sítios de Ligação , Cristalografia por Raios X , Desenho de Fármacos , Humanos , Concentração Inibidora 50 , Simulação de Dinâmica Molecular , Estrutura Terciária de Proteína , Relação Estrutura-Atividade , Triazóis/metabolismoRESUMO
The serotonin transporter (SERT) terminates serotonergic neurotransmission by performing reuptake of released serotonin, and SERT is the primary target for antidepressants. SERT mediates the reuptake of serotonin through an alternating access mechanism, implying that a central substrate site is connected to both sides of the membrane by permeation pathways, of which only one is accessible at a time. The coordinated conformational changes in SERT associated with substrate translocation are not fully understood. Here, we have identified a Leu to Glu mutation at position 406 (L406E) in the extracellular loop 4 (EL4) of human SERT, which induced a remarkable gain-of-potency (up to >40-fold) for a range of SERT inhibitors. The effects were highly specific for L406E relative to six other mutations in the same position, including the closely related L406D mutation, showing that the effects induced by L406E are not simply charge-related effects. Leu(406) is located >10 Å from the central inhibitor binding site indicating that the mutation affects inhibitor binding in an indirect manner. We found that L406E decreased accessibility to a residue in the cytoplasmic pathway. The shift in equilibrium to favor a more outward-facing conformation of SERT can explain the reduced turnover rate and increased association rate of inhibitor binding we found for L406E. Together, our findings show that EL4 allosterically can modulate inhibitor binding within the central binding site, and substantiates that EL4 has an important role in controlling the conformational equilibrium of human SERT.
Assuntos
Proteínas da Membrana Plasmática de Transporte de Serotonina/química , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Sequência de Aminoácidos , Animais , Sítios de Ligação , Células COS , Chlorocebus aethiops , Células HEK293 , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Mutação Puntual , Ligação Proteica , Conformação Proteica , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Inibidores Seletivos de Recaptação de Serotonina/farmacologiaRESUMO
Approximately 30% of the ATP generated in the living cell is utilized by P-type ATPase primary active transporters to generate and maintain electrochemical gradients across biological membranes. P-type ATPases undergo large conformational changes during their functional cycle to couple ATP hydrolysis in the cytoplasmic domains to ion transport across the membrane. The Ca(2+)-ATPase from Listeria monocytogenes, LMCA1, was found to be a suitable model of P-type ATPases and was engineered to facilitate single-molecule FRET studies of transport-related structural changes. Mutational analyses of the endogenous cysteine residues in LMCA1 were performed to reduce background labeling without compromising activity. Pairs of cysteines were introduced into the optimized low-reactivity background, and labeled with maleimide derivatives of Cy3 and Cy5 resulting in site-specifically double-labeled protein with moderate activity. Ensemble and confocal single-molecule FRET studies revealed changes in FRET distribution related to structural changes during the transport cycle, consistent with those observed by X-ray crystallography for the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA). Notably, the cytosolic headpiece of LMCA1 was found to be distinctly more compact in the E1 state than in the E2 state. Thus, the established experimental system should allow future real-time FRET studies of the structural dynamics of LMCA1 as a representative P-type ATPase.
Assuntos
ATPases Transportadoras de Cálcio/genética , ATPases Transportadoras de Cálcio/metabolismo , Transferência Ressonante de Energia de Fluorescência , Listeria monocytogenes/enzimologia , Engenharia de Proteínas , ATPases Transportadoras de Cálcio/química , Maleimidas/química , Modelos Moleculares , Mutagênese Sítio-Dirigida , Mutação , Conformação ProteicaRESUMO
The serotonin transporter (SERT) regulates neurotransmission by the biogenic monoamine neurotransmitter serotonin (5-HT, 5-hydroxytryptamine) in the central nervous system, and drugs inhibiting SERT are widely used for the treatment of a variety of central nervous system diseases. The conformational dynamics of SERT transport function and inhibition is currently poorly understood. We used voltage-clamp fluorometry to study conformational changes in human SERT (hSERT) during 5-HT transport and inhibitor binding. Cys residues were introduced at 12 positions in hSERT to enable covalent attachment of a rhodamine-based fluorophore. Transport-associated changes in fluorescence from fluorophore-labeled hSERT expressed in Xenopus oocytes could be robustly detected at four positions in hSERT: endogenous Cys109 in the top of transmembrane domain (TM) 1b, Cys substituted for Thr323 in the top of TM6, Ala419 in the interface between TM8 and extracellular loop (EL) 4, and Leu481 in EL5. The reporter positions were used for time-resolved measurement of conformational changes during 5-HT transport and binding of cocaine and the selective serotonin reuptake inhibitors fluoxetine and escitalopram. At all reporter positions, fluorescence changes observed upon substrate application were distinctly different from those observed upon inhibitor application, with respect to relative amplitude or direction. Furthermore, escitalopram, fluoxetine, and cocaine induced a very similar pattern of fluorescent changes overall, which included movements within or around TM1b, EL4, and EL5. Taken together, our data lead us to suggest that competitive inhibitors stabilize hSERT in a state that is different from the apo outward-open conformation as well as inward-facing conformations.