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Protein degradation by human 20S proteasomes elucidates the interplay between peptide hydrolysis and splicing. Nat Commun 2024; 15:1147. [PMID: 38326304 PMCID: PMC10850103 DOI: 10.1038/s41467-024-45339-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 01/17/2024] [Indexed: 02/09/2024] Open
Abstract
If and how proteasomes catalyze not only peptide hydrolysis but also peptide splicing is an open question that has divided the scientific community. The debate has so far been based on immunopeptidomics, in vitro digestions of synthetic polypeptides as well as ex vivo and in vivo experiments, which could only indirectly describe proteasome-catalyzed peptide splicing of full-length proteins. Here we develop a workflow-and cognate software - to analyze proteasome-generated non-spliced and spliced peptides produced from entire proteins and apply it to in vitro digestions of 15 proteins, including well-known intrinsically disordered proteins such as human tau and α-Synuclein. The results confirm that 20S proteasomes produce a sizeable variety of cis-spliced peptides, whereas trans-spliced peptides are a minority. Both peptide hydrolysis and splicing produce peptides with well-defined characteristics, which hint toward an intricate regulation of both catalytic activities. At protein level, both non-spliced and spliced peptides are not randomly localized within protein sequences, but rather concentrated in hotspots of peptide products, in part driven by protein sequence motifs and proteasomal preferences. At sequence level, the different peptide sequence preference of peptide hydrolysis and peptide splicing suggests a competition between the two catalytic activities of 20S proteasomes during protein degradation.
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Multiple redox switches of the SARS-CoV-2 main protease in vitro provide opportunities for drug design. Nat Commun 2024; 15:411. [PMID: 38195625 PMCID: PMC10776599 DOI: 10.1038/s41467-023-44621-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Accepted: 12/21/2023] [Indexed: 01/11/2024] Open
Abstract
Besides vaccines, the development of antiviral drugs targeting SARS-CoV-2 is critical for preventing future COVID outbreaks. The SARS-CoV-2 main protease (Mpro), a cysteine protease with essential functions in viral replication, has been validated as an effective drug target. Here, we show that Mpro is subject to redox regulation in vitro and reversibly switches between the enzymatically active dimer and the functionally dormant monomer through redox modifications of cysteine residues. These include a disulfide-dithiol switch between the catalytic cysteine C145 and cysteine C117, and generation of an allosteric cysteine-lysine-cysteine SONOS bridge that is required for structural stability under oxidative stress conditions, such as those exerted by the innate immune system. We identify homo- and heterobifunctional reagents that mimic the redox switching and inhibit Mpro activity. The discovered redox switches are conserved in main proteases from other coronaviruses, e.g. MERS-CoV and SARS-CoV, indicating their potential as common druggable sites.
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Reconstruction of a fatty acid synthesis cycle from acyl carrier protein and cofactor structural snapshots. Cell 2023; 186:5054-5067.e16. [PMID: 37949058 DOI: 10.1016/j.cell.2023.10.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 07/21/2023] [Accepted: 10/05/2023] [Indexed: 11/12/2023]
Abstract
Fatty acids (FAs) play a central metabolic role in living cells as constituents of membranes, cellular energy reserves, and second messenger precursors. A 2.6 MDa FA synthase (FAS), where the enzymatic reactions and structures are known, is responsible for FA biosynthesis in yeast. Essential in the yeast FAS catalytic cycle is the acyl carrier protein (ACP) that actively shuttles substrates, biosynthetic intermediates, and products from one active site to another. We resolve the S. cerevisiae FAS structure at 1.9 Å, elucidating cofactors and water networks involved in their recognition. Structural snapshots of ACP domains bound to various enzymatic domains allow the reconstruction of a full yeast FA biosynthesis cycle. The structural information suggests that each FAS functional unit could accommodate exogenous proteins to incorporate various enzymatic activities, and we show proof-of-concept experiments where ectopic proteins are used to modulate FAS product profiles.
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Epileptogenic Tubers Are Associated with Increased Kurtosis of Susceptibility Values: A Combined Quantitative Susceptibility Mapping and Stereoelectroencephalography Pilot Study. AJNR Am J Neuroradiol 2023; 44:974-982. [PMID: 37474265 PMCID: PMC10411828 DOI: 10.3174/ajnr.a7929] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Accepted: 06/07/2023] [Indexed: 07/22/2023]
Abstract
BACKGROUND AND PURPOSE Prior studies have found an association between calcification and the epileptogenicity of tubers in tuberous sclerosis complex. Quantitative susceptibility mapping is a novel tool sensitive to magnetic susceptibility alterations due to tissue calcification. We assessed the utility of quantitative susceptibility mapping in identifying putative epileptogenic tubers in tuberous sclerosis complex using stereoelectroencephalography data as ground truth. MATERIALS AND METHODS We studied patients with tuberous sclerosis complex undergoing stereoelectroencephalography at a single center who had multiecho gradient-echo sequences available. Quantitative susceptibility mapping and R2* values were extracted for all tubers on the basis of manually drawn 3D ROIs using T1- and T2-FLAIR sequences. Characteristics of quantitative susceptibility mapping and R2* distributions from implanted tubers were compared using binary logistic generalized estimating equation models designed to identify ictal (involved in seizure onset) and interictal (persistent interictal epileptiform activity) tubers. These models were then applied to the unimplanted tubers to identify potential ictal and interictal tubers that were not sampled by stereoelectroencephalography. RESULTS A total of 146 tubers were identified in 10 patients, 76 of which were sampled using stereoelectroencephalography. Increased kurtosis of the tuber quantitative susceptibility mapping values was associated with epileptogenicity (P = .04 for the ictal group and P = .005 for the interictal group) by the generalized estimating equation model. Both groups had poor sensitivity (35.0% and 44.1%, respectively) but high specificity (94.6% and 78.6%, respectively). CONCLUSIONS Our finding of increased kurtosis of quantitative susceptibility mapping values (heavy-tailed distribution) was highly specific, suggesting that it may be a useful biomarker to identify putative epileptogenic tubers in tuberous sclerosis complex. This finding motivates the investigation of underlying tuber mineralization and other properties driving kurtosis changes in quantitative susceptibility mapping values.
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EIGER2 hybrid-photon-counting X-ray detectors for advanced synchrotron diffraction experiments. JOURNAL OF SYNCHROTRON RADIATION 2023; 30:S160057752300454X. [PMID: 37343017 DOI: 10.1107/s160057752300454x] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 05/23/2023] [Indexed: 06/23/2023]
Abstract
The ability to utilize a hybrid-photon-counting detector to its full potential can significantly influence data quality, data collection speed, as well as development of elaborate data acquisition schemes. This paper facilitates the optimal use of EIGER2 detectors by providing theory and practical advice on (i) the relation between detector design, technical specifications and operating modes, (ii) the use of corrections and calibrations, and (iii) new acquisition features: a double-gating mode, 8-bit readout mode for increasing temporal resolution, and lines region-of-interest readout mode for frame rates up to 98 kHz. Examples of the implementation and application of EIGER2 at several synchrotron sources (ESRF, PETRA III/DESY, ELETTRA, AS/ANSTO) are presented: high accuracy of high-throughput data in serial crystallography using hard X-rays; suppressing higher harmonics of undulator radiation, improving peak shapes, increasing data collection speed in powder X-ray diffraction; faster ptychography scans; and cleaner and faster pump-and-probe experiments.
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Prospects and Limitations of High-Resolution Single-Particle Cryo-Electron Microscopy. Annu Rev Biophys 2023; 52:391-411. [PMID: 37159297 DOI: 10.1146/annurev-biophys-111622-091300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Single particle cryo-electron microscopy (cryo-EM) has matured into a robust method for the determination of biological macromolecule structures in the past decade, complementing X-ray crystallography and nuclear magnetic resonance. Constant methodological improvements in both cryo-EM hardware and image processing software continue to contribute to an exponential growth in the number of structures solved annually. In this review, we provide a historical view of the many steps that were required to make cryo-EM a successful method for the determination of high-resolution protein complex structures. We further discuss aspects of cryo-EM methodology that are the greatest pitfalls challenging successful structure determination to date. Lastly, we highlight and propose potential future developments that would improve the method even further in the near future.
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Comparison of suspected and confirmed internal EVD-related infections: a prospective multi-centre U.K. observational study. Open Forum Infect Dis 2022; 9:ofac480. [PMID: 36267249 PMCID: PMC9578167 DOI: 10.1093/ofid/ofac480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022] Open
Abstract
Background Diagnosis of internal external ventricular drain (EVD)-related infections (iERI) is an area of diagnostic difficulty. Empiric treatment is often initiated on clinical suspicion. There is limited guidance around antimicrobial management of confirmed versus suspected iERI. Methods Data on patients requiring EVD insertion were collected from 21 neurosurgical units in the United Kingdom from 2014 to 2015. Confirmed iERI was defined as clinical suspicion of infection with positive cerebrospinal fluid (CSF) culture and/or Gram stain. Cerebrospinal fluid, blood, and clinical parameters and antimicrobial management were compared between the 2 groups. Mortality and Modified Rankin Scores were compared at 30 days post-EVD insertion. Results Internal EVD-related infection was suspected after 46 of 495 EVD insertions (9.3%), more common after an emergency insertion. Twenty-six of 46 were confirmed iERIs, mostly due to Staphylococci (16 of 26). When confirmed and suspected infections were compared, there were no differences in CSF white cell counts or glucose concentrations, nor peripheral blood white cell counts or C-reactive protein concentrations. The incidence of fever, meningism, and seizures was also similar, although altered consciousness was more common in people with confirmed iERI. Broad-spectrum antimicrobial usage was prevalent in both groups with no difference in median duration of therapy (10 days [interquartile range {IQR}, 7–24.5] for confirmed cases and 9.5 days [IQR, 5.75–14] for suspected, P = 0.3). Despite comparable baseline characteristics, suspected iERI was associated with lower mortality and better neurological outcomes. Conclusions Suspected iERI could represent sterile inflammation or lower bacterial load leading to false-negative cultures. There is a need for improved microbiology diagnostics and biomarkers of bacterial infection to permit accurate discrimination and improve antimicrobial stewardship.
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Atomic resolution structure determination of larger macromolecular complexes by cryo-EM and X-ray crystallography. ACTA CRYSTALLOGRAPHICA SECTION A FOUNDATIONS AND ADVANCES 2022. [DOI: 10.1107/s2053273322096632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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Enabling high-energy large-unit-cell ultra-high-resolution X-ray crystallography on the P14 at PETRAIII beamline. ACTA CRYSTALLOGRAPHICA SECTION A FOUNDATIONS AND ADVANCES 2022. [DOI: 10.1107/s2053273322096097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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10
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Enabling high-energy large-unit-cell ultra-high-resolution X-ray crystallography on beamline P14@PETRAIII. Acta Crystallogr A Found Adv 2022. [DOI: 10.1107/s2053273322098746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Guidance for Use and dosing of Selinexor in Multiple Myeloma in 2021: Consensus From International Myeloma Foundation Expert Roundtable. CLINICAL LYMPHOMA, MYELOMA & LEUKEMIA 2022; 22:e526-e531. [PMID: 35361554 DOI: 10.1016/j.clml.2022.01.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 10/19/2022]
Abstract
Selinexor is a first in class selective inhibitor of nuclear export (SINE), blocks exportin 1 (XPO1), a protein transporter, that among other actions, shuttles cargo proteins such as tumor suppressor proteins (TSPs), the glucocorticoid receptor (GR), and oncoprotein messenger RNAs (mRNAs) across the nuclear membrane to cytoplasm. By blocking XPO1, selinexor facilitates nuclear preservation and activation of TSPs, and prevents mRNA translation of the oncoproteins leading to induction of apoptosis. The therapeutic value of selinexor in combination with dexamethasone has been successfully demonstrated in treating relapsed and/or refractory myeloma (RRMM), leading to the Food and Drug Administration (FDA) approval of selinexor in combination with dexamethasone in 2019 for the treatment of adult patients with RRMM who received at least 4 prior therapies and whose disease is refractory to at least 2 proteasome inhibitors, at least 2 immunomodulatory agents, and an anti-CD38 monoclonal antibody (mAb) - a pentarefractory myeloma. More recently, selinexor in combination with bortezomib and dexamethasone was approved by the FDA in December 2020, based on the BOSTON study among RRMM patients who had received at least one prior line of therapy. With more available safety and efficacy data supporting the increased interval between dosing of selinexor (and lesser cumulative weekly dosing) and schedule, contrary to the originally approved dose of 160 mg per week, the supportive care guidelines needed to be revisited. The current manuscript summarizes the supportive care solutions with weekly dosing of selinexor and identifies the ideal potential patient for selinexor treatment.
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Conformational rearrangements upon start codon recognition in human 48S translation initiation complex. Nucleic Acids Res 2022; 50:5282-5298. [PMID: 35489072 PMCID: PMC9122606 DOI: 10.1093/nar/gkac283] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/08/2022] [Accepted: 04/20/2022] [Indexed: 01/10/2023] Open
Abstract
Selection of the translation start codon is a key step during protein synthesis in human cells. We obtained cryo-EM structures of human 48S initiation complexes and characterized the intermediates of codon recognition by kinetic methods using eIF1A as a reporter. Both approaches capture two distinct ribosome populations formed on an mRNA with a cognate AUG codon in the presence of eIF1, eIF1A, eIF2–GTP–Met-tRNAiMet and eIF3. The ‘open’ 40S subunit conformation differs from the human 48S scanning complex and represents an intermediate preceding the codon recognition step. The ‘closed’ form is similar to reported structures of complexes from yeast and mammals formed upon codon recognition, except for the orientation of eIF1A, which is unique in our structure. Kinetic experiments show how various initiation factors mediate the population distribution of open and closed conformations until 60S subunit docking. Our results provide insights into the timing and structure of human translation initiation intermediates and suggest the differences in the mechanisms of start codon selection between mammals and yeast.
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Ground-state destabilization by electrostatic repulsion is not a driving force in orotidine-5′-monophosphate decarboxylase catalysis. Nat Catal 2022. [DOI: 10.1038/s41929-022-00771-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Fatty acid (FA) biosynthesis plays a central role in the metabolism of living cells as building blocks of biological membranes, energy reserves of the cell, and precursors to second messenger molecules. In keeping with its central metabolic role, FA biosynthesis impacts several cellular functions and its misfunction is linked to disease, such as cancer, obesity, and non-alcoholic fatty liver disease. Cellular FA biosynthesis is conducted by fatty acid synthases (FAS). All FAS enzymes catalyze similar biosynthetic reactions, but the functional architectures adopted by these cellular catalysts can differ substantially. This variability in FAS structure amongst various organisms and the essential role played by FA biosynthetic pathways makes this metabolic route a valuable target for the development of antibiotics. Beyond cellular FA biosynthesis, the quest for renewable energy sources has piqued interest in FA biosynthetic pathway engineering to generate biofuels and fatty acid derived chemicals. For these applications, based on FA biosynthetic pathways, to succeed, detailed metabolic, functional and structural insights into FAS are required, along with an intimate knowledge into the regulation of FAS. In this review, we summarize our present knowledge about the functional, structural, and regulatory aspects of FAS.
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Chromatography-Free Purification Strategies for Large Biological Macromolecular Complexes Involving Fractionated PEG Precipitation and Density Gradients. Life (Basel) 2021; 11:1289. [PMID: 34947821 PMCID: PMC8707722 DOI: 10.3390/life11121289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 11/10/2021] [Accepted: 11/22/2021] [Indexed: 12/25/2022] Open
Abstract
A complex interplay between several biological macromolecules maintains cellular homeostasis. Generally, the demanding chemical reactions which sustain life are not performed by individual macromolecules, but rather by several proteins that together form a macromolecular complex. Understanding the functional interactions amongst subunits of these macromolecular machines is fundamental to elucidate mechanisms by which they maintain homeostasis. As the faithful function of macromolecular complexes is essential for cell survival, their mis-function leads to the development of human diseases. Furthermore, detailed mechanistic interrogation of the function of macromolecular machines can be exploited to develop and optimize biotechnological processes. The purification of intact macromolecular complexes is an essential prerequisite for this; however, chromatographic purification schemes can induce the dissociation of subunits or the disintegration of the whole complex. Here, we discuss the development and application of chromatography-free purification strategies based on fractionated PEG precipitation and orthogonal density gradient centrifugation that overcomes existing limitations of established chromatographic purification protocols. The presented case studies illustrate the capabilities of these procedures for the purification of macromolecular complexes.
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TALQUETAMAB, A G PROTEIN-COUPLED RECEPTOR FAMILY C GROUP 5 MEMBER D (GPRC5D) CD3 BISPECIFIC ANTIBODY FOR RELAPSED/REFRACTORY MULTIPLE MYELOMA (RRMM): UPDATED PHASE 1 STUDY RESULTS. Hematol Transfus Cell Ther 2021. [DOI: 10.1016/j.htct.2021.10.365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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X-ray screening identifies active site and allosteric inhibitors of SARS-CoV-2 main protease. Science 2021; 372:642-646. [PMID: 33811162 PMCID: PMC8224385 DOI: 10.1126/science.abf7945] [Citation(s) in RCA: 203] [Impact Index Per Article: 67.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/29/2021] [Indexed: 12/17/2022]
Abstract
The coronavirus disease (COVID-19) caused by SARS-CoV-2 is creating tremendous human suffering. To date, no effective drug is available to directly treat the disease. In a search for a drug against COVID-19, we have performed a high-throughput x-ray crystallographic screen of two repurposing drug libraries against the SARS-CoV-2 main protease (Mpro), which is essential for viral replication. In contrast to commonly applied x-ray fragment screening experiments with molecules of low complexity, our screen tested already-approved drugs and drugs in clinical trials. From the three-dimensional protein structures, we identified 37 compounds that bind to Mpro In subsequent cell-based viral reduction assays, one peptidomimetic and six nonpeptidic compounds showed antiviral activity at nontoxic concentrations. We identified two allosteric binding sites representing attractive targets for drug development against SARS-CoV-2.
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77 The Development of Core Outcome Sets and Common Data Elements in Clinical Neurosciences: A Scoping Review. Br J Surg 2021. [DOI: 10.1093/bjs/znab134.113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Introduction
The use of core outcome sets (COS) and common data elements (CDEs) minimises research wastage by increasing the cross-comparison and meta-analysis of study findings. Our study sought to identify the clinical neuroscience subspecialties that have developed COS and CDEs, the countries of origin of authors, and the process through which COS and CDEs were developed.
Method
A search between 2000-2020 of the top 40 Impact Factor neurosurgical and neurological journals was conducted. A scoping review was performed in accordance with the PRISMA-ScR Checklist.
Results
Our search returned 169 papers, of which 35 were eligible for inclusion. The USA published the majority of papers (20/35). The papers mostly related to neurosurgery (30/35), with the most common neurosurgical sub-specialty being traumatic brain injury (14/35). There is an increasing publication trend over time, with 12 papers published in 2019. Five papers were systematic reviews conducting with the intention of COS/CDE development. 27 papers reported CDE development and 2 papers reported COS development. The COS development papers utilised international consensus meetings and adhered to international development statements.
Conclusions
COS and CDEs are increasingly being developed within clinical neurosciences. There is a need for greater international collaboration with regards to COS and CDEs development.
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133 Neurosurgery Education in The Medical School Curriculum: A Scoping Review. Br J Surg 2021. [DOI: 10.1093/bjs/znab134.117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
Introduction
Worldwide, there is no specific medical school curriculum in neurosurgery despite a high burden of neurosurgical disease that is often assessed, investigated and managed by generalists. This scoping review was carried out to map available evidence pertaining to the provision of neurosurgery education in the medical school curriculum across the world.
Method
This review was conducted in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis extension for Scoping Reviews.
Results
Ten studies were included. Six were from the United Kingdom, two from the United States, and one each from Canada and Ireland. Two studies evaluated perceptions of both medical students and practicing clinicians, five studies evaluated the perceptions of medical students and three studies reported perceptions of clinicians only. Three main themes were identified. Neurosurgery was perceived as an important part of the general medical student curriculum. Exposure to neurosurgery teaching was varied but when received, deemed useful and students were keen to receive more. Interest in a neurosurgical career amongst medical students was high.
Conclusions
There is a lack of a specialty-specific medical school curriculum and variability of medical students’ exposure to neurosurgery teaching exists. Our findings highlight the need to systematically assess specialty-specific teaching and determine adequacy.
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The copper(II)-binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography. Acta Crystallogr D Struct Biol 2020; 76:1222-1232. [PMID: 33263328 PMCID: PMC7709198 DOI: 10.1107/s2059798320013741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 10/13/2020] [Indexed: 12/04/2022] Open
Abstract
The growth of diffraction-quality crystals and experimental phasing remain two of the main bottlenecks in protein crystallography. Here, the high-affinity copper(II)-binding tripeptide GHK was fused to the N-terminus of a GFP variant and an MBP-FG peptide fusion. The GHK tag promoted crystallization, with various residues (His, Asp, His/Pro) from symmetry molecules completing the copper(II) square-pyramidal coordination sphere. Rapid structure determination by copper SAD phasing could be achieved, even at a very low Bijvoet ratio or after significant radiation damage. When collecting highly redundant data at a wavelength close to the copper absorption edge, residual S-atom positions could also be located in log-likelihood-gradient maps and used to improve the phases. The GHK copper SAD method provides a convenient way of both crystallizing and phasing macromolecular structures, and will complement the current trend towards native sulfur SAD and MR-SAD phasing.
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EFFICACY AND SAFETY OF CARFILZOMIB, DEXAMETHASONE, DARATUMUMAB TWICE-WEEKLY AT 56 MG/M2 AND ONCE-WEEKLY AT 70 MG/M2 IN RELAPSED OR REFRACTORY MULTIPLE MYELOMA: CROSS-STUDY COMPARISON OF CANDOR AND MMY1001. Hematol Transfus Cell Ther 2020. [DOI: 10.1016/j.htct.2020.10.431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Proteasomal degradation of the intrinsically disordered protein tau at single-residue resolution. SCIENCE ADVANCES 2020; 6:eaba3916. [PMID: 32832664 PMCID: PMC7439447 DOI: 10.1126/sciadv.aba3916] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 06/05/2020] [Indexed: 05/28/2023]
Abstract
Intrinsically disordered proteins (IDPs) can be degraded in a ubiquitin-independent process by the 20S proteasome. Decline in 20S activity characterizes neurodegenerative diseases. Here, we examine 20S degradation of IDP tau, a protein that aggregates into insoluble deposits in Alzheimer's disease. We show that cleavage of tau by the 20S proteasome is most efficient within the aggregation-prone repeat region of tau and generates both short, aggregation-deficient peptides and two long fragments containing residues 1 to 251 and 1 to 218. Phosphorylation of tau by the non-proline-directed Ca2+/calmodulin-dependent protein kinase II inhibits degradation by the 20S proteasome. Phosphorylation of tau by GSK3β, a major proline-directed tau kinase, modulates tau degradation kinetics in a residue-specific manner. The study provides detailed insights into the degradation products of tau generated by the 20S proteasome, the residue specificity of degradation, single-residue degradation kinetics, and their regulation by posttranslational modification.
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Structural and Functional Analyses of the Human PDH Complex Suggest a "Division-of-Labor" Mechanism by Local E1 and E3 Clusters. Structure 2019; 27:1124-1136.e4. [PMID: 31130485 DOI: 10.1016/j.str.2019.04.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 01/17/2019] [Accepted: 04/11/2019] [Indexed: 11/27/2022]
Abstract
The pseudo-atomic structural model of human pyruvate dehydrogenase complex (PDHc) core composed of full-length E2 and E3BP components, calculated from our cryoelectron microscopy-derived density maps at 6-Å resolution, is similar to those of prokaryotic E2 structures. The spatial organization of human PDHc components as evidenced by negative-staining electron microscopy and native mass spectrometry is not homogeneous, and entails the unanticipated formation of local clusters of E1:E2 and E3BP:E3 complexes. Such uneven, clustered organization translates into specific duties for E1-E2 clusters (oxidative decarboxylation and acetyl transfer) and E3BP-E3 clusters (regeneration of reduced lipoamide) corresponding to half-reactions of the PDHc catalytic cycle. The addition of substrate coenzyme A modulates the conformational landscape of PDHc, in particular of the lipoyl domains, extending the postulated multiple random coupling mechanism. The conformational and associated chemical landscapes of PDHc are thus not determined entirely stochastically, but are restrained and channeled through an asymmetric architecture and further modulated by substrate binding.
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Abstract
OBJECTIVES Papilloedema is a clinical manifestation of chronically raised intracranial pressure (ICP), often seen in idiopathic intracranial hypertension (IIH). However, the extent of intracranial hypertension required to produce papilloedema is not known. We compare ICP values in IIH patients who developed papilloedema and those who did not. We aim to identify a pathological ICP threshold predictive of the development of papilloedema in IIH patients. MATERIALS AND METHODS Single-centre cohort of IIH patients (2006-2016) who underwent 24-hour ICP monitoring (ICPM) and ophthalmology assessments, prior to intervention. Papilloedema was graded according to the Frisén scale. An unpaired t-test compared 24-hour ICPM between papilloedema and no-papilloedema groups. Fisher's exact test was used to determine predictive value of ICP. RESULTS Thirty-six patients with IIH (35 F: 1M), mean age 32.5 ± 9.49 years (mean ± SD) were included. Patients with papilloedema had a mean median 24-hour ICP of 10.4 ± 5.32 mm Hg (n = 25), significantly higher than the group without papilloedema 6.31 ± 3.30 mm Hg (n = 11) (P < .05). The papilloedema group were exposed to higher pressures (10 mm Hg) for 30 minutes or more. Using 24-hour median ICP of 10 mm Hg as a minimum cut-off predictive value gives a specificity = 91%, sensitivity = 48%, PPV = 92% and NPV = 44% of detecting papilloedema. CONCLUSIONS A 24-hour ICP of 10 mmHg or more is a good predictor for papilloedema and reflects a pathological threshold. The range varied widely suggesting papilloedema can occur at even lower pressures. These results are consistent with emerging evidence suggest that pathologically "high" 24 hours ICP is lower than previously quoted.
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The Ribosome Cooperates with the Assembly Chaperone pICln to Initiate Formation of snRNPs. Cell Rep 2018; 16:3103-3112. [PMID: 27653676 DOI: 10.1016/j.celrep.2016.08.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 07/11/2016] [Accepted: 08/15/2016] [Indexed: 01/05/2023] Open
Abstract
The formation of macromolecular complexes within the crowded environment of cells often requires aid from assembly chaperones. PRMT5 and SMN complexes mediate this task for the assembly of the common core of pre-mRNA processing small nuclear ribonucleoprotein particles (snRNPs). Core formation is initiated by the PRMT5-complex subunit pICln, which pre-arranges the core proteins into spatial positions occupied in the assembled snRNP. The SMN complex then accepts these pICln-bound proteins and unites them with small nuclear RNA (snRNA). Here, we have analyzed how newly synthesized snRNP proteins are channeled into the assembly pathway to evade mis-assembly. We show that they initially remain bound to the ribosome near the polypeptide exit tunnel and dissociate upon association with pICln. Coincident with its release activity, pICln ensures the formation of cognate heterooligomers and their chaperoned guidance into the assembly pathway. Our study identifies the ribosomal quality control hub as a site where chaperone-mediated assembly of macromolecular complexes can be initiated.
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Split dosing of daratumumab (D) in a phase 1b study of D plus carfilzomib (K)-based regimens in patients (pts) with multiple myeloma (MM). Ann Oncol 2017. [DOI: 10.1093/annonc/mdx373.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Integrative network analysis identifies novel drivers of pathogenesis and progression in newly diagnosed multiple myeloma. Leukemia 2017. [DOI: 10.1038/leu.2017.197] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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DARATUMUMAB, LENALIDOMIDE, AND DEXAMETHASONE (DRD) VS LENALIDOMIDE AND DEXAMETHASONE (RD) IN RELAPSED OR REFRACTORY MULTIPLE MYELOMA (RRMM): EFFICACY AND SAFETY UPDATE (POLLUX). Hematol Oncol 2017. [DOI: 10.1002/hon.2439_153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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P419Day-case pacemaker implantation: feasible, acceptable, safe - An eight-year uk single-centre experience. Europace 2017. [DOI: 10.1093/ehjci/eux141.143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Long-range allosteric regulation of the human 26S proteasome by 20S proteasome-targeting cancer drugs. Nat Commun 2017; 8:15578. [PMID: 28541292 PMCID: PMC5458511 DOI: 10.1038/ncomms15578] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 04/07/2017] [Indexed: 01/03/2023] Open
Abstract
The proteasome holoenzyme is the major non-lysosomal protease; its proteolytic activity is essential for cellular homeostasis. Thus, it is an attractive target for the development of chemotherapeutics. While the structural basis of core particle (CP) inhibitors is largely understood, their structural impact on the proteasome holoenzyme remains entirely elusive. Here, we determined the structure of the 26S proteasome with and without the inhibitor Oprozomib. Drug binding modifies the energy landscape of conformational motion in the proteasome regulatory particle (RP). Structurally, the energy barrier created by Oprozomib triggers a long-range allosteric regulation, resulting in the stabilization of a non-productive state. Thereby, the chemical drug-binding signal is converted, propagated and amplified into structural changes over a distance of more than 150 Å from the proteolytic site to the ubiquitin receptor Rpn10. The direct visualization of changes in conformational dynamics upon drug binding allows new ways to screen and develop future allosteric proteasome inhibitors.
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POSTERS (2)96CONTINUOUS VERSUS INTERMITTENT MONITORING FOR DETECTION OF SUBCLINICAL ATRIAL FIBRILLATION IN HIGH-RISK PATIENTS97HIGH DAY-TO-DAY INTRA-INDIVIDUAL REPRODUCIBILITY OF THE HEART RATE RESPONSE TO EXERCISE IN THE UK BIOBANK DATA98USE OF NOVEL GLOBAL ULTRASOUND IMAGING AND CONTINUEOUS DIPOLE DENSITY MAPPING TO GUIDE ABLATION IN MACRO-REENTRANT TACHYCARDIAS99ANTICOAGULATION AND THE RISK OF COMPLICATIONS IN PATIENTS UNDERGOING VT AND PVC ABLATION100NON-SUSTAINED VENTRICULAR TACHYCARDIA FREQUENTLY PRECEDES CARDIAC ARREST IN PATIENTS WITH BRUGADA SYNDROME101USING HIGH PRECISION HAEMODYNAMIC MEASUREMENTS TO ASSESS DIFFERENCES IN AV OPTIMUM BETWEEN DIFFERENT LEFT VENTRICULAR LEAD POSITIONS IN BIVENTRICULAR PACING102CAN WE PREDICT MEDIUM TERM MORTALITY FROM TRANSVENOUS LEAD EXTRACTION PRE-OPERATIVELY?103PREVENTION OF UNECESSARY ADMISSIONS IN ATRIAL FIBRILLATION104EPICARDIAL CATHETER ABLATION FOR VENTRICULAR TACHYCARDIA ON UNINTERRUPTED WARFARIN: A SAFE APPROACH?105HOW WELL DOES THE NATIONAL INSTITUTE OF CLINICAL EXCELLENCE (NICE) GUIDENCE ON TRANSIENT LOSS OF CONSCIOUSNESS (T-LoC) WORK IN A REAL WORLD? AN AUDIT OF THE SECOND STAGE SPECIALIST CARDIOVASCULAT ASSESSMENT AND DIAGNOSIS106DETECTION OF ATRIAL FIBRILLATION IN COMMUNITY LOCATIONS USING NOVEL TECHNOLOGY'S AS A METHOD OF STROKE PREVENTION IN THE OVER 65'S ASYMPTOMATIC POPULATION - SHOULD IT BECOME STANDARD PRACTISE?107HIGH-DOSE ISOPRENALINE INFUSION AS A METHOD OF INDUCTION OF ATRIAL FIBRILLATION: A MULTI-CENTRE, PLACEBO CONTROLLED CLINICAL TRIAL IN PATIENTS WITH VARYING ARRHYTHMIC RISK108PACEMAKER COMPLICATIONS IN A DISTRICT GENERAL HOSPITAL109CARDIAC RESYNCHRONISATION THERAPY: A TRADE-OFF BETWEEN LEFT VENTRICULAR VOLTAGE OUTPUT AND EJECTION FRACTION?110RAPID DETERIORATION IN LEFT VENTRICULAR FUNCTION AND ACUTE HEART FAILURE AFTER DUAL CHAMBER PACEMAKER INSERTION WITH RESOLUTION FOLLOWING BIVENTRICULAR PACING111LOCALLY PERSONALISED ATRIAL ELECTROPHYSIOLOGY MODELS FROM PENTARAY CATHETER MEASUREMENTS112EVALUATION OF SUBCUTANEOUS ICD VERSUS TRANSVENOUS ICD- A PROPENSITY MATCHED COST-EFFICACY ANALYSIS OF COMPLICATIONS & OUTCOMES113LOCALISING DRIVERS USING ORGANISATIONAL INDEX IN CONTACT MAPPING OF HUMAN PERSISTENT ATRIAL FIBRILLATION114RISK FACTORS FOR SUDDEN CARDIAC DEATH IN PAEDIATRIC HYPERTROPHIC CARDIOMYOPATHY: A SYSTEMATIC REVIEW AND META-ANALYSIS115EFFECT OF CATHETER STABILITY AND CONTACT FORCE ON VISITAG DENSITY DURING PULMONARY VEIN ISOLATION116HEPATIC CAPSULE ENHANCEMENT IS COMMONLY SEEN DURING MR-GUIDED ABLATION OF ATRIAL FLUTTER: A MECHANISTIC INSIGHT INTO PROCEDURAL PAIN117DOES HIGHER CONTACT FORCE IMPAIR LESION FORMATION AT THE CAVOTRICUSPID ISTHMUS? INSIGHTS FROM MR-GUIDED ABLATION OF ATRIAL FLUTTER118CLINICAL CHARACTERISATION OF A MALIGNANT SCN5A MUTATION IN CHILDHOOD119RADIOFREQUENCY ASSOCIATED VENTRICULAR FIBRILLATION120CONTRACTILE RESERVE EXPRESSED AS SYSTOLIC VELOCITY DOES NOT PREDICT RESPONSE TO CRT121DAY-CASE DEVICES - A RETROSPECTIVE STUDY USING PATIENT CODING DATA122PATIENTS UNDERGOING SVT ABLATION HAVE A HIGH INCIDENCE OF SECONDARY ARRHYTHMIA ON FOLLOW UP: IMPLICATIONS FOR PRE-PROCEDURE COUNSELLING123PROGNOSTIC ROLE OF HAEMOGLOBINN AND RED BLOOD CELL DITRIBUTION WIDTH IN PATIENTS WITH HEART FAILURE UNDERGOING CARDIAC RESYNCHRONIZATION THERAPY124REMOTE MONITORING AND FOLLOW UP DEVICES125A 20-YEAR, SINGLE-CENTRE EXPERIENCE OF IMPLANTABLE CARDIOVERTER DEFIBRILLATORS (ICD) IN CHILDREN: TIME TO CONSIDER THE SUBCUTANEOUS ICD?126EXPERIENCE OF MAGNETIC REASONANCE IMAGING (MEI) IN PATIENTS WITH MRI CONDITIONAL DEVICES127THE SINUS BRADYCARDIA SEEN IN ATHLETES IS NOT CAUSED BY ENHANCED VAGAL TONE BUT INSTEAD REFLECTS INTRINSIC CHANGES IN THE SINUS NODE REVEALED BY
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(F) BLOCKADE128SUCCESSFUL DAY-CASE PACEMAKER IMPLANTATION - AN EIGHT YEAR SINGLE-CENTRE EXPERIENCE129LEFT VENTRICULAR INDEX MASS ASSOCIATED WITH ESC HYPERTROPHIC CARDIOMYOPATHY RISK SCORE IN PATIENTS WITH ICDs: A TERTIARY CENTRE HCM REGISTRY130A DGH EXPERIENCE OF DAY-CASE CARDIAC PACEMAKER IMPLANTATION131IS PRE-PROCEDURAL FASTING A NECESSITY FOR SAFE PACEMAKER IMPLANTATION? Europace 2016. [DOI: 10.1093/europace/euw274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Molecular architecture of the Saccharomyces cerevisiae activated spliceosome. Science 2016; 353:1399-1405. [PMID: 27562955 DOI: 10.1126/science.aag1906] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/18/2016] [Indexed: 12/30/2022]
Abstract
The activated spliceosome (Bact) is in a catalytically inactive state and is remodeled into a catalytically active machine by the RNA helicase Prp2, but the mechanism is unclear. Here, we describe a 3D electron cryomicroscopy structure of the Saccharomyces cerevisiae Bact complex at 5.8-angstrom resolution. Our model reveals that in Bact, the catalytic U2/U6 RNA-Prp8 ribonucleoprotein core is already established, and the 5' splice site (ss) is oriented for step 1 catalysis but occluded by protein. The first-step nucleophile-the branchsite adenosine-is sequestered within the Hsh155 HEAT domain and is held 50 angstroms away from the 5'ss. Our structure suggests that Prp2 adenosine triphosphatase-mediated remodeling leads to conformational changes in Hsh155's HEAT domain that liberate the first-step reactants for catalysis.
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The inhibition mechanism of human 20Sproteasomes enables next-generation inhibitor design. Science 2016; 353:594-8. [DOI: 10.1126/science.aaf8993] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Accepted: 07/14/2016] [Indexed: 01/02/2023]
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Sample preparation of biological macromolecular assemblies for the determination of high-resolution structures by cryo-electron microscopy. Microscopy (Oxf) 2015; 65:23-34. [PMID: 26671943 DOI: 10.1093/jmicro/dfv367] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 11/05/2015] [Indexed: 01/04/2023] Open
Abstract
Single particle cryo-EM has recently developed into a powerful tool to determine the 3D structure of macromolecular complexes at near-atomic resolution, which allows structural biologists to build atomic models of proteins. All technical aspects of cryo-EM technology have been considerably improved over the last two decades, including electron microscopic hardware, image processing software and the ever growing speed of computers. This leads to a more widespread use of the technique, and it can be anticipated that further automation of electron microscopes and image processing tools will soon fully shift the focus away from the technological aspects, onto biological questions that can be answered. In single particle cryo-EM, no crystals of a macromolecule are required. In contrast to X-ray crystallography, this significantly facilitates structure determination by cryo-EM. Nevertheless, a relatively high level of biochemical control is still essential to obtain high-resolution structures by cryo-EM, and it can be anticipated that the success of the cryo-EM technology goes hand in hand with further developments of sample purification and preparation techniques. This will allow routine high-resolution structure determination of the many macromolecular complexes of the cell that until now represent evasive targets for X-ray crystallographers. Here we discuss the various biochemical tools that are currently available and the existing sample purification and preparation techniques for cryo-EM grid preparation that are needed to obtain high-resolution images for structure determination.
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35
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ProteoPlex: stability optimization of macromolecular complexes by sparse-matrix screening of chemical space. Nat Methods 2015; 12:859-65. [PMID: 26237227 DOI: 10.1038/nmeth.3493] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 06/17/2015] [Indexed: 01/04/2023]
Abstract
Molecular machines or macromolecular complexes are supramolecular assemblies of biomolecules with a variety of functions. Structure determination of these complexes in a purified state is often tedious owing to their compositional complexity and the associated relative structural instability. To improve the stability of macromolecular complexes in vitro, we present a generic method that optimizes the stability, homogeneity and solubility of macromolecular complexes by sparse-matrix screening of their thermal unfolding behavior in the presence of various buffers and small molecules. The method includes the automated analysis of thermal unfolding curves based on a biophysical unfolding model for complexes. We found that under stabilizing conditions, even large multicomponent complexes reveal an almost ideal two-state unfolding behavior. We envisage an improved biochemical understanding of purified macromolecules as well as a substantial boost in successful macromolecular complex structure determination by both X-ray crystallography and cryo-electron microscopy.
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Reconstitution of the human U snRNP assembly machinery reveals stepwise Sm protein organization. EMBO J 2015; 34:1925-41. [PMID: 26069323 DOI: 10.15252/embj.201490350] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 05/12/2015] [Indexed: 11/09/2022] Open
Abstract
The assembly of spliceosomal U snRNPs depends on the coordinated action of PRMT5 and SMN complexes in vivo. These trans-acting factors enable the faithful delivery of seven Sm proteins onto snRNA and the formation of the common core of snRNPs. To gain mechanistic insight into their mode of action, we reconstituted the assembly machinery from recombinant sources. We uncover a stepwise and ordered formation of distinct Sm protein complexes on the PRMT5 complex, which is facilitated by the assembly chaperone pICln. Upon completion, the formed pICln-Sm units are displaced by new pICln-Sm protein substrates and transferred onto the SMN complex. The latter acts as a Brownian machine that couples spontaneous conformational changes driven by thermal energy to prevent mis-assembly and to ensure the transfer of Sm proteins to cognate RNA. Investigation of mutant SMN complexes provided insight into the contribution of individual proteins to these activities. The biochemical reconstitution presented here provides a basis for a detailed molecular dissection of the U snRNP assembly reaction.
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The catalytically inactive tyrosine phosphatase HD-PTP/PTPN23 is a novel regulator of SMN complex localization. Mol Biol Cell 2014; 26:161-71. [PMID: 25392300 PMCID: PMC4294665 DOI: 10.1091/mbc.e14-06-1151] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
This first systematic and comprehensive screen of human phosphatases for a regulatory role in the survival motor neuron (SMN) complex identifies the catalytically inactive, non–receptor-type tyrosine phosphatase PTPN23/HD-PTP as a novel SMN complex regulator. PTPN23 maintains a highly phosphorylated state of SMN, which is important for its function in snRNP assembly. The survival motor neuron (SMN) complex fulfils essential functions in the assembly of snRNPs, which are key components in the splicing of pre-mRNAs. Little is known about the regulation of SMN complex activity by posttranslational modification despite its complicated phosphorylation pattern. Several phosphatases had been implicated in the regulation of SMN, including the nuclear phosphatases PPM1G and PP1γ. Here we systematically screened all human phosphatase gene products for a regulatory role in the SMN complex. We used the accumulation of SMN in Cajal bodies of intact proliferating cells, which actively assemble snRNPs, as a readout for unperturbed SMN complex function. Knockdown of 29 protein phosphatases interfered with SMN accumulation in Cajal bodies, suggesting impaired SMN complex function, among those the catalytically inactive, non–receptor-type tyrosine phosphatase PTPN23/HD-PTP. Knockdown of PTPN23 also led to changes in the phosphorylation pattern of SMN without affecting the assembly of the SMN complex. We further show interaction between SMN and PTPN23 and document that PTPN23, like SMN, shuttles between nucleus and cytoplasm. Our data provide the first comprehensive screen for SMN complex regulators and establish a novel regulatory function of PTPN23 in maintaining a highly phosphorylated state of SMN, which is important for its proper function in snRNP assembly.
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Phosphoregulation of the human SMN complex. Eur J Cell Biol 2014; 93:106-17. [PMID: 24602413 DOI: 10.1016/j.ejcb.2014.01.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 01/22/2014] [Accepted: 01/22/2014] [Indexed: 10/25/2022] Open
Abstract
The survival motor neuron (SMN) complex is a macromolecular machine comprising 9 core proteins: SMN, Gemins2-8 and unrip in vertebrates. It performs tasks in RNA metabolism including the cytoplasmic assembly of spliceosomal small nuclear ribonucleoprotein particles (snRNPs). The SMN complex also localizes to the nucleus, where it accumulates in Cajal Bodies (CB) and may function in transcription and/or pre-mRNA splicing. The SMN complex is subject to extensive phosphorylation. Detailed understanding of SMN complex regulation necessitates a comprehensive analysis of these post-translational modifications. Here, we report on the first comprehensive phosphoproteome analysis of the intact human SMN complex, which identify 48 serine/threonine phosphosites in the complex. We find that 7 out of 9 SMN components of the intact complex are phosphoproteins and confidently place 29 phosphorylation sites, 12 of them in SMN itself. By the generation of multi non-phosphorylatable or phosphomimetic variants of SMN, respectively, we address to which extent phosphorylation regulates SMN complex function and localization. Both phosphomimetic and non-phosphorylatable variants assemble into intact SMN complexes and can compensate the loss of endogenous SMN in snRNP assembly at least to some extent. However, they partially or completely fail to target to nuclear Cajal bodies. Moreover, using a mutant of SMN, which cannot be phosphorylated on previously reported tyrosine residues, we provide first evidence that this PTM regulates SMN localization and nuclear accumulation. Our data suggest complex regulatory cues mediated by phosphorylation of serine/threonine and tyrosine residues, which control the subcellular localization of the SMN complex and its accumulation in nuclear CB.
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Atrial fibrillation detection algorithms alone are inadequate for identifying atrial arrhythmia by implantable loop recorder after ischaemic stroke. Eur Heart J 2013. [DOI: 10.1093/eurheartj/eht309.p4068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Complication of pellagra in anorexia nervosa. Assoc Med J 2013. [DOI: 10.1136/bmj.f2842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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082 DAY CASE PACEMAKER IMPLANTATION FEASIBLE ACCEPTABLE AND SAFE. BRITISH HEART JOURNAL 2013. [DOI: 10.1136/heartjnl-2013-304019.82] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Structural basis of assembly chaperone- mediated snRNP formation. Mol Cell 2013; 49:692-703. [PMID: 23333303 DOI: 10.1016/j.molcel.2012.12.009] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 11/06/2012] [Accepted: 12/13/2012] [Indexed: 11/19/2022]
Abstract
Small nuclear ribonucleoproteins (snRNPs) represent key constituents of major and minor spliceosomes. snRNPs contain a common core, composed of seven Sm proteins bound to snRNA, which forms in a step-wise and factor-mediated reaction. The assembly chaperone pICln initially mediates the formation of an otherwise unstable pentameric Sm protein unit. This so-called 6S complex docks subsequently onto the SMN complex, which removes pICln and enables the transfer of pre-assembled Sm proteins onto snRNA. X-ray crystallography and electron microscopy was used to investigate the structural basis of snRNP assembly. The 6S complex structure identifies pICln as an Sm protein mimic, which enables the topological organization of the Sm pentamer in a closed ring. A second structure of 6S bound to the SMN complex components SMN and Gemin2 uncovers a plausible mechanism of pICln elimination and Sm protein activation for snRNA binding. Our studies reveal how assembly factors facilitate formation of RNA-protein complexes in vivo.
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Pituitary Tumor Surgery in the Elderly: Perioperative Complications and Long-Term Outcome. Skull Base Surg 2012. [DOI: 10.1055/s-0032-1314047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Biogenesis of spliceosomal small nuclear ribonucleoproteins. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:718-31. [PMID: 21823231 DOI: 10.1002/wrna.87] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Virtually, all eukaryotic mRNAs are synthesized as precursor molecules that need to be extensively processed in order to serve as a blueprint for proteins. The three most prevalent processing steps are the capping reaction at the 5'-end, the removal of intervening sequences by splicing, and the formation of poly (A)-tails at the 3'-end of the message by polyadenylation. A large number of proteins and small nuclear ribonucleoprotein complexes (snRNPs) interact with the mRNA and enable the different maturation steps. This chapter focuses on the biogenesis of snRNPs, the major components of the pre-mRNA splicing machinery (spliceosome). A large body of evidence has revealed an intricate and segmented pathway for the formation of snRNPs that involves nucleo-cytoplasmic transport events and elaborates assembly strategies. We summarize the knowledge about the different steps with an emphasis on trans-acting factors of snRNP maturation of higher eukaryotes. WIREs RNA 2011 2 718-731 DOI: 10.1002/wrna.87 For further resources related to this article, please visit the WIREs website.
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Cellular strategies for the assembly of molecular machines. Trends Biochem Sci 2010; 35:676-83. [PMID: 20727772 DOI: 10.1016/j.tibs.2010.07.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 07/20/2010] [Accepted: 07/21/2010] [Indexed: 01/13/2023]
Abstract
Molecular machines are supramolecular assemblies of biomolecules (proteins, RNA and/or DNA) that facilitate a diversity of biological tasks in the cells of all organisms. How these complex structures are built within the crowded cellular environment is, therefore, a central question in the biological sciences. Recent studies on spliceosomal uridine-rich small nuclear ribonucleoproteins (snRNPs) have unveiled cellular assembly strategies for RNA-protein complexes. snRNPs form in vivo by the coordinated action of an elaborate assembly line consisting of assembly chaperones, scaffolding proteins and catalysts. These newly discovered strategies exhibit similarities to those employed by protein complexes such as ribulose-1,5-bisphosphate-carboxylase (Rubisco) and allow the elucidation of general rules for how molecular machines are formed in vivo.
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Abstract
Mammalian cleavage factor I (CF I(m)) is composed of two polypeptides of 25 kDa and either a 59 or 68 kDa subunit (CF I(m)25, CF I(m)59, CF I(m)68). It is part of the cleavage and polyadenylation complex responsible for processing the 3' ends of messenger RNA precursors. To investigate post-translational modifications in factors of the 3' processing complex, we systematically searched for enzymes that modify arginines by the addition of methyl groups. Protein arginine methyltransferases (PRMTs) are such enzymes that transfer methyl groups from S-adenosyl methionine to arginine residues within polypeptide chains resulting in mono- or dimethylated arginines. We found that CF I(m)68 and the nuclear poly(A) binding protein 1 (PABPN1) were methylated by HeLa cell extracts in vitro. By fractionation of these extracts followed by mass spectral analysis, we could demonstrate that the catalytic subunit PRMT5, together with its cofactor WD45, could symmetrically dimethylate CF I(m)68, whereas pICln, the third polypeptide of the complex, was stimulatory. As sites of methylation in CF I(m)68 we could exclusively identify arginines in a GGRGRGRF or "GAR" motif that is conserved in vertebrates. Further in vitro assays revealed a second methyltransferase, PRMT1, which modifies CF I(m)68 by asymmetric dimethylation of the GAR motif and also weakly methylates the C-termini of both CF I(m)59 and CF I(m)68. The results suggest that native-as compared with recombinant-protein substrates may contain additional determinants for methylation by specific PRMTs. A possible involvement of CF I(m) methylation in the context of RNA export is discussed.
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A crystallization screen based on alternative polymeric precipitants. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:685-97. [PMID: 20516621 DOI: 10.1107/s0907444910009005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2009] [Accepted: 03/09/2010] [Indexed: 11/10/2022]
Abstract
Most commercially available crystallization screens are sparse-matrix screens with a predominance of inorganic salts and polyethylene glycols (PEGs) as precipitants. It was noted that commercially available screens are largely unsatisfactory for the purpose of the crystallization of multimeric protein and protein-nucleic acid complexes. This was reasoned to be a consequence of the redundancy in screening crystallization parameter space by the predominance of PEG as a precipitant in standard screens and it was suggested that this limitation could be overcome by introducing a variety of other organic polymers. Here, a set of 288 crystallization conditions was devised based on alternative polymeric precipitants and tested against a set of 20 different proteins/complexes; finally, a screen comprising the 96 most promising conditions designed to complement PEG- and salt-based commercial screens was proposed.
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LSm1-7 complexes bind to specific sites in viral RNA genomes and regulate their translation and replication. RNA (NEW YORK, N.Y.) 2010; 16:817-27. [PMID: 20181739 PMCID: PMC2844628 DOI: 10.1261/rna.1712910] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Accepted: 01/07/2010] [Indexed: 05/18/2023]
Abstract
LSm1-7 complexes promote cellular mRNA degradation, in addition to translation and replication of positive-strand RNA viruses such as the Brome mosaic virus (BMV). Yet, how LSm1-7 complexes act on their targets remains elusive. Here, we report that reconstituted recombinant LSm1-7 complexes directly bind to two distinct RNA-target sequences in the BMV genome, a tRNA-like structure at the 3'-untranslated region and two internal A-rich single-stranded regions. Importantly, in vivo analysis shows that these sequences regulate the translation and replication of the BMV genome. Furthermore, both RNA-target sequences resemble those found for Hfq, the LSm counterpart in bacteria, suggesting conservation through evolution. Our results provide the first evidence that LSm1-7 complexes interact directly with viral RNA genomes and open new perspectives in the understanding of LSm1-7 functions.
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Feasibility of CD34-Positive Stem Cell Mobilization by Administration of AMD3100 Six Hours Prior to Leukapheresis. Biol Blood Marrow Transplant 2009. [DOI: 10.1016/j.bbmt.2008.12.129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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