The serotonin 5-HT
receptor is a pentameric ligand-gated ion channel (pLGIC). It belongs to a large family of receptors that function as allosteric signal transducers across the plasma membrane
; ...upon binding of neurotransmitter molecules to extracellular sites, the receptors undergo complex conformational transitions that result in transient opening of a pore permeable to ions. 5-HT
receptors are therapeutic targets for emesis and nausea, irritable bowel syndrome and depression
. In spite of several reported pLGIC structures
, no clear unifying view has emerged on the conformational transitions involved in channel gating. Here we report four cryo-electron microscopy structures of the full-length mouse 5-HT
receptor in complex with the anti-emetic drug tropisetron, with serotonin, and with serotonin and a positive allosteric modulator, at resolutions ranging from 3.2 Å to 4.5 Å. The tropisetron-bound structure resembles those obtained with an inhibitory nanobody
or without ligand
. The other structures include an 'open' state and two ligand-bound states. We present computational insights into the dynamics of the structures, their pore hydration and free-energy profiles, and characterize movements at the gate level and cation accessibility in the pore. Together, these data deepen our understanding of the gating mechanism of pLGICs and capture ligand binding in unprecedented detail.
Abstract The blood-sucking reduviid bug Triatoma infestans , one of the most important vector of American human trypanosomiasis (Chagas disease) is infected by the Triatoma virus (TrV). TrV has been ...classified as a member of the Cripavirus genus (type cricket paralysis virus) in the Dicistroviridae family. This work presents the three-dimensional cryo-electron microscopy (cryo-EM) reconstruction of the TrV capsid at about 25 Å resolution and its use as a template for phasing the available crystallographic data by the molecular replacement method. The main structural differences between the cryo-EM reconstruction of TrV and other two viruses, one from the same family, the cricket paralysis virus (CrPV) and the human rhinovirus 16 from the Picornaviridae family are presented and discussed.
Cyanine-loaded lipid nanoparticles for improved Texier, Isabelle; Goutayer, Mathieu; Da Silva, Anabela ...
Journal of Biomedical Optics,
8 September 2009, Letnik:
14, Številka:
5
Journal Article
Recenzirano
Fluorescence is a very promising radioactive-free technique for functional imaging in small animals and, in the future, in humans. However, most commercial near-infrared dyes display poor optical ...properties, such as low fluorescence quantum yields and short fluorescence lifetimes. In this paper, we explore whether the encapsulation of infrared cyanine dyes within the core of lipid nanoparticles (LNPs) could improve their optical properties. Lipophilic dialkylcarbocyanines DiD and DiR are loaded very efficiently in
-diam lipid droplets stabilized in water by surfactants. No significant fluorescence autoquenching is observed up to 53 dyes per particle. Encapsulated in LNP, which are stable for more than one year at room temperature in HBS buffer (HEPES 0.02 M, EDTA 0.01 M, pH 5.5), DiD and DiR display far improved fluorescence quantum yields
(respectively, 0.38 and 0.25) and longer fluorescence lifetimes
(respectively, 1.8 and
) in comparison to their hydrophilic counterparts Cy5 (
,
) and Cy7 (
,
). Moreover, dye-loaded LNPs are able to accumulate passively in various subcutaneous tumors in mice, thanks to the enhanced permeability and retention effect. These new fluorescent nanoparticles therefore appear as very promising labels for
fluorescence imaging.
The value of an electron microscope equipped with a field emission gun (FEG) was first revealed in materials science applications. More recently, the FEG has played a crucial role in breaking the 10Å ...barrier in single-particle reconstructions of frozen hydrated biological molecules. The standard high-resolution performance tests for electron microscopes are made close to focus, at several hundreds of Å underfocus at a magnification of
500
000×
or more. While this is appropriate for materials science specimens, it is not suitable for observing frozen hydrated biological specimens with which the optimum underfocus is of the order of 1 micron or so and the magnification is limited by radiation damage to roughly 30
000 to
60
000×
. Thus, in order to access the performance of a cryo-electron microscope for high-resolution 3D electron microscopy of biological molecules, additional tests are necessary. We present here resolution tests of a 200-kV FEG using frozen hydrated virus suspensions. The extent and amplitude of the contrast transfer function are used as a test of the performance. We propose that small spherical viruses close to 300
Å in diameter, such as the picornaviruses or phages, make good specimens for testing the performance of an electron microscope in cryo-mode.
Rotaviruses are large, complex icosahedral particles consisting of three concentric capsid layers. When the innermost capsid protein VP2 is expressed in the baculovirus-insect cell system it ...assembles as core-like particles. The amino terminus region of VP2 is dispensable for assembly of virus-like particles (VLP). Coexpression of VP2 and VP6 produces double layered VLP. We hypothesized that the amino end of VP2 could be extended without altering the auto assembly properties of VP2. Using the green fluorescent protein (GFP) or the DsRed protein as model inserts we have shown that the chimeric protein GFP (or DsRed)-VP2 auto assembles perfectly well and forms fluorescent VLP (GFP-VLP2/6 or DsRed-VLP2/6) when coexpressed with VP6. The presence of GFP inside the core does not prevent the assembly of the outer capsid layer proteins VP7 and VP4 to give VLP2/6/7/4. Cryo-electron microscopy of purified GFP-VLP2/6 showed that GFP molecules are located at the 5-fold vertices of the core. It is possible to visualize a single fluorescent VLP in living cells by confocal fluorescent microscopy. In vitro VLP2/6 did not enter into permissive cells or in dendritic cells. In contrast, fluorescent VLP2/6/7/4 entered the cells and then the fluorescence signal disappear rapidly. Presented data indicate that fluorescent VLP are interesting tools to follow in real time the entry process of rotavirus and that chimeric VLP could be envisaged as “nanoboxes” carrying macromolecules to living cells.
Rotaviruses are large, complex icosahedral particles consisting of three concentric capsid layers. When the innermost capsid protein VP2 is expressed in the baculovirus-insect cell system it ...assembles as core-like particles. The amino terminus region of VP2 is dispensable for assembly of virus-like particles (VLP). Coexpression of VP2 and VP6 produces double layered VLP. We hypothesized that the amino end of VP2 could be extended without altering the auto assembly properties of VP2. Using the green fluorescent protein (GFP) or the DsRed protein as model inserts we have shown that the chimeric protein GFP (or DsRed)-VP2 auto assembles perfectly well and forms fluorescent VLP (GFP-VLP2/6 or DsRed-VLP2/6) when coexpressed with VP6. The presence of GFP inside the core does not prevent the assembly of the outer capsid layer proteins VP7 and VP4 to give VLP2/6/7/4. Cryo-electron microscopy of purified GFP-VLP2/6 showed that GFP molecules are located at the 5-fold vertices of the core. It is possible to visualize a single fluorescent VLP in living cells by confocal fluorescent microscopy. In vitro VLP2/6 did not enter into permissive cells or in dendritic cells. In contrast, fluorescent VLP2/6/7/4 entered the cells and then the fluorescence signal disappear rapidly. Presented data indicate that fluorescent VLP are interesting tools to follow in real time the entry process of rotavirus and that chimeric VLP could be envisaged as “nanoboxes” carrying macromolecules to living cells.
Rotaviruses are large, complex icosahedral particles consisting of three concentric capsid layers. When the innermost capsid protein VP2 is expressed in the baculovirus-insect cell system it ...assembles as core-like particles. The amino terminus region of VP2 is dispensable for assembly of virus-like particles (VLP). Coexpression of VP2 and VP6 produces double layered VLP. We hypothesized that the amino end of VP2 could be extended without altering the auto assembly properties of VP2. Using the green fluorescent protein (GFP) or the DsRed protein as model inserts we have shown that the chimeric protein GFP (or DsRed)-VP2 auto assembles perfectly well and forms fluorescent VLP (GFP-VLP2/6 or DsRed-VLP2/6) when coexpressed with VP6. The presence of GFP inside the core does not prevent the assembly of the outer capsid layer proteins VP7 and VP4 to give VLP2/6/7/4. Cryo-electron microscopy of purified GFP-VLP2/6 showed that GFP molecules are located at the 5-fold vertices of the core. It is possible to visualize a single fluorescent VLP in living cells by confocal fluorescent microscopy. In vitro VLP2/6 did not enter into permissive cells or in dendritic cells. In contrast, fluorescent VLP2/6/7/4 entered the cells and then the fluorescence signal disappear rapidly. Presented data indicate that fluorescent VLP are interesting tools to follow in real time the entry process of rotavirus and that chimeric VLP could be envisaged as “nanoboxes” carrying macromolecules to living cells.
Summary Background Based on preclinical data for the antitumour effect of zoledronate in osteosarcoma, we assessed whether zoledronate combined with chemotherapy and surgery improved event-free ...survival in children and adults with osteosarcoma. Methods In this randomised, multicentre, open-label, phase 3 trial (OS2006), patients aged between 5 years and 50 years with newly diagnosed high-grade osteosarcoma were randomly assigned to receive standard chemotherapy with or without ten zoledronate intravenous infusions (four preoperative and six postoperative). Adults older than 25 years received 4 mg zoledronate per infusion, patients aged 18–25 years received 0·05 mg/kg for the first two infusions and 4 mg for the remaining eight infusions, and younger patients received 0·05 mg/kg per infusion. Chemotherapy comprised high-dose methotrexate based chemotherapy in patients younger than 18 years, and doxorubicin, ifosfamide, and cisplatin in adults older than 25 years; patients aged 18–25 years were treated with either regime at the discretion of the treating centre. Balanced randomisation between the two groups was done centrally with online randomisation software, based on a minimisation algorithm taking into account centre, age, combined with chemotherapy regimen, and risk group (resectable primary and no metastasis vs other). Patients and investigators were not masked to treatment assignment, but the endpoint adjudication committee members who reviewed suspected early progressions were masked to group allocation. The primary endpoint was event-free survival, estimated from the randomisation to the time of first failure (local or distant relapse, progression, death) or to the last follow-up visit for the patients in first complete remission, analysed on a modified intention-to-treat population, which excluded patients found not to have a malignant tumour after central review. Three interim analyses were planned. This trial is registered with ClinicalTrials.gov , number NCT00470223. Findings Between April 23, 2007, and March 11, 2014, 318 patients, median age 15·5 years (range 5·8–50·9), were enrolled from 40 French centres; of whom 158 were assigned to the control group (chemotherapy alone) and 160 to the zoledronate group, including 55 (17%) patients with definite metastases. The trial was stopped for futility after the second interim analysis. With a median follow-up of 3·9 years (IQR 2·7–5·1), 125 events occurred (55 in the control group and 70 in the with zoledronate group). Event-free survival at 3 years for all 315 randomly assigned patients was 60·3% (95% CI 64·5–65·9); 3-year event-free survival was 63·4% (55·2–70·9) for the control group and 57·1% (48·8–65·0) for the zoledronate group. The risk of failure was not reduced and was even marginally higher in the zoledronate group than in the control group (hazard ratio HR 1·36 95% CI 0·95–1·96; p=0·094). No major increase in severe toxic effects of grade 3 or higher associated with zoledronate, barring expected hypocalcaemia (45 29% of 153 participants in the zoledronate group vs ten 6% of 155 participants in the control group; p<0·0001) and hypophosphataemia (61 40% of 151 in the zoledronate group vs 26 17% of 156 in the control group; p<0·0001). No significant difference in orthopaedic complications was noted between the two groups (27 in the control group and 29 in the zoledronate group). Two treatment-related deaths were reported (one from cardiomyopathy in the control group and one from multiorgan failure in the zoledronate group before the first zoledronate infusion). Interpretation From the results observed in this study, we do not recommend zoledronate in osteosarcoma patients. Further biological studies are required to understand the discordance between the results of OS2006 trial and preclinical data. Funding French National Cancer Institute (INCa), Novartis, Chugai, Ligue Nationale contre le Cancer, Fédération Enfants et Santé, Société Française des Cancers et Leucémies de l'Enfant.
SummaryBackgroundDesmoid tumours are locally aggressive tumours associated with substantial morbidity. No systemic treatments are approved for this disease, with methotrexate–vinblastine the only ...chemotherapy regimen assessed in a clinical trial setting to date. VEGF overexpression is a common feature in aggressive desmoid tumours. Pazopanib is an oral antiangiogenic agent targeting VEGF receptors 1, 2, and 3, platelet-derived growth factor receptor-like protein (PDGFR) α and β, and c-KIT tyrosine kinases. We aimed to assess antitumour activity and safety of targeted therapy or combination chemotherapy in progressive desmoid tumours. MethodsDESMOPAZ was a non-comparative, randomised, open-label, phase 2 trial conducted at 12 centres from the French Sarcoma Group. We enrolled adults (≥18 years) with progressive desmoid tumours, normal organ function and centrally documented progressive disease according to Response Evaluation Criteria in Solid Tumors version 1.1 based on two imaging assessments obtained within less than a 6-month interval. Participants were randomly assigned (2:1) to oral pazopanib 800 mg per day for up to 1 year or to an intravenous regimen combining vinblastine (5 mg/m 2 per dose) and methotrexate (30 mg/m 2 per dose), administered weekly for 6 months and then every other week for 6 months. Randomisation was stratified according to inclusion centre and tumour location. The primary endpoint was the proportion of patients who had not progressed at 6 months in the first 43 patients who had received one complete or two incomplete cycles of pazopanib. This endpoint was also assessed as a prespecified exploratory endpoint in all patients who had received one complete or two incomplete cycles of methotrexate–vinblastane. Safety analyses were done for all patients who received at least one dose of allocated treatment. This trial was registered with ClinicalTrials.gov, number NCT01876082. FindingsFrom Dec 4, 2012, to Aug 18, 2017, 72 patients were enrolled and randomly assigned (n=48 in the pazopanib group; n=24 in the methotrexate–vinblastine group). Median follow-up was 23·4 months (IQR 17·1–25·5). 46 patients in the pazopanib group and 20 patients in the methotrexate–vinblastine group were assessable for activity. In the first 43 patients assessable for the primary endpoint in the pazopanib group, the proportion of patients who had not progressed at 6 months was 83·7% (95% CI 69·3–93·2). The proportion of patients treated with methotrexate–vinblastine who had not progressed at 6 months was 45·0% (95% CI 23·1–68·5). The most common grade 3 or 4 adverse events in the pazopanib group were hypertension (n=10, 21%) and diarrhoea (n=7, 15%) and in the methotrexate–vinblastine group were neutropenia (n=10, 45%) and liver transaminitis (n=4, 18%). 11 patients (23%) had at least one serious adverse event related to study treatment in the pazopanib group, as did and six patients (27%) in the methotrexate–vinblastine group. InterpretationPazopanib has clinical activity in patients with progressive desmoid tumours and could be a valid treatment option in this rare and disabling disease. FundingGlaxoSmithKline and Novartis.
PDF
