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Netters S, Dekker N, van de Wetering K, Hasker A, Paasman D, de Groot JW, Vissers KCP. Pandemic ICU triage challenge and medical ethics. BMJ Support Palliat Care 2021; 11:133-137. [PMID: 33541855 PMCID: PMC7868132 DOI: 10.1136/bmjspcare-2020-002793] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/24/2020] [Accepted: 12/31/2020] [Indexed: 12/12/2022]
Abstract
The COVID-19 pandemic has made unprecedented global demands on healthcare in general and especially the intensive care unit (ICU). the virus is spreading out of control. To this day, there is no clear, published directive for doctors regarding the allocation of ICU beds in times of scarcity. This means that many doctors do not feel supported by their government and are afraid of the medicolegal consequences of the choices they have to make. Consequently, there has been no transparent discussion among professionals and the public. The thought of being at the mercy of absolute arbitrariness leads to fear among the population, especially the vulnerable groups.
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Affiliation(s)
- Sabine Netters
- Oncology Centre and Internal Medicine Department, Isala, Zwolle, The Netherlands
| | - Nick Dekker
- Oncology Centre and Internal Medicine Department, Isala, Zwolle, The Netherlands
| | | | - Annie Hasker
- Pastoral Care Department, Isala, Zwolle, The Netherlands
| | - Dian Paasman
- Internal Medicine Department, Isala, Zwolle, The Netherlands
| | - Jan Willem de Groot
- Oncology Centre and Internal Medicine Department, Isala, Zwolle, The Netherlands
| | - Kris C P Vissers
- Anaesthesiology Department, Radboud University Medical Center, Nijmegen, The Netherlands
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2
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Marques ARA, Mirzaian M, Akiyama H, Wisse P, Ferraz MJ, Gaspar P, Ghauharali-van der Vlugt K, Meijer R, Giraldo P, Alfonso P, Irún P, Dahl M, Karlsson S, Pavlova EV, Cox TM, Scheij S, Verhoek M, Ottenhoff R, van Roomen CPAA, Pannu NS, van Eijk M, Dekker N, Boot RG, Overkleeft HS, Blommaart E, Hirabayashi Y, Aerts JM. Glucosylated cholesterol in mammalian cells and tissues: formation and degradation by multiple cellular β-glucosidases. J Lipid Res 2016; 57:451-63. [PMID: 26724485 PMCID: PMC4766994 DOI: 10.1194/jlr.m064923] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Indexed: 12/20/2022] Open
Abstract
The membrane lipid glucosylceramide (GlcCer) is continuously formed and degraded. Cells express two GlcCer-degrading β-glucosidases, glucocerebrosidase (GBA) and GBA2, located in and outside the lysosome, respectively. Here we demonstrate that through transglucosylation both GBA and GBA2 are able to catalyze in vitro the transfer of glucosyl-moieties from GlcCer to cholesterol, and vice versa. Furthermore, the natural occurrence of 1-O-cholesteryl-β-D-glucopyranoside (GlcChol) in mouse tissues and human plasma is demonstrated using LC-MS/MS and 13C6-labeled GlcChol as internal standard. In cells, the inhibition of GBA increases GlcChol, whereas inhibition of GBA2 decreases glucosylated sterol. Similarly, in GBA2-deficient mice, GlcChol is reduced. Depletion of GlcCer by inhibition of GlcCer synthase decreases GlcChol in cells and likewise in plasma of inhibitor-treated Gaucher disease patients. In tissues of mice with Niemann-Pick type C disease, a condition characterized by intralysosomal accumulation of cholesterol, marked elevations in GlcChol occur as well. When lysosomal accumulation of cholesterol is induced in cultured cells, GlcChol is formed via lysosomal GBA. This illustrates that reversible transglucosylation reactions are highly dependent on local availability of suitable acceptors. In conclusion, mammalian tissues contain GlcChol formed by transglucosylation through β-glucosidases using GlcCer as donor. Our findings reveal a novel metabolic function for GlcCer.
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Affiliation(s)
- André R A Marques
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | - Mina Mirzaian
- Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
| | | | - Patrick Wisse
- Bio-organic Synthesis, Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Maria J Ferraz
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | - Paulo Gaspar
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Rianne Meijer
- Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Pilar Giraldo
- Centro de Investigación Biomédica en Red de Enfermedades Raras, Unidad de Investigación Traslacional, Zaragoza, Spain
| | - Pilar Alfonso
- Centro de Investigación Biomédica en Red de Enfermedades Raras, Unidad de Investigación Traslacional, Zaragoza, Spain
| | - Pilar Irún
- Centro de Investigación Biomédica en Red de Enfermedades Raras, Unidad de Investigación Traslacional, Zaragoza, Spain
| | - Maria Dahl
- Department of Molecular Medicine and Gene Therapy, Lund University, Lund, Sweden
| | - Stefan Karlsson
- Department of Molecular Medicine and Gene Therapy, Lund University, Lund, Sweden
| | - Elena V Pavlova
- Addenbrooke's Hospital, Department of Medicine, University of Cambridge, Cambridge, UK
| | - Timothy M Cox
- Addenbrooke's Hospital, Department of Medicine, University of Cambridge, Cambridge, UK
| | - Saskia Scheij
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | - Marri Verhoek
- Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Roelof Ottenhoff
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Navraj S Pannu
- Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Marco van Eijk
- Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Nick Dekker
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | - Rolf G Boot
- Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Herman S Overkleeft
- Bio-organic Synthesis, Leiden Institute of Chemistry, Leiden, The Netherlands
| | - Edward Blommaart
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Johannes M Aerts
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands Departments of Medical Biochemistry Leiden Institute of Chemistry, Leiden, The Netherlands
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3
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Moraitou M, Dermentzaki G, Dimitriou E, Monopolis I, Dekker N, Aerts H, Stefanis L, Michelakakis H. α-Synuclein dimerization in erythrocytes of Gaucher disease patients: correlation with lipid abnormalities and oxidative stress. Neurosci Lett 2015; 613:1-5. [PMID: 26708635 DOI: 10.1016/j.neulet.2015.12.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/12/2015] [Accepted: 12/09/2015] [Indexed: 11/18/2022]
Abstract
Several observations suggest that disturbed homeostasis of α-Synuclein (α-Syn) may provide a link between Gaucher disease (GD) and Parkinson's disease (PD). We recently reported increased dimerization of α-Syn in the red blood cell (RBC) membrane of patients with GD. Several studies indicate a crucial relationship between lipids, oxidative stress and α-Syn status. Here we investigated the relationship between the observed increased dimerization of α-Syn in the cell membranes of RBCs, cells devoid of lysosomes and lacking lysosomal enzyme synthesis, and the lipid abnormalities and oxidative stress already described in GD. Correlation studies showed that in GD the α-Syn dimer/monomer ratio is positively correlated with the levels of glucosylceramide (GlcCer) and the glucosylceramide/ceramide (GlcCer/Cer) ratio and negatively with the levels of malonyldialdehyde (MDA) and plasmalogens. In conclusion, we have shown that the increased tendency of α-Syn to form dimers in the RBC membrane of patients with GD, is correlated with both the level of lipids, including GlcCer, the primary lipid abnormality in GD, and the increased oxidative stress observed in this disorder. The study of other tissues, and in particular brain, will be important in order to elucidate the significance of these findings regarding the link between GD and PD.
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Affiliation(s)
- Marina Moraitou
- Department of Enzymology and Cellular Function, Institute of Child Health, Athens, Greece
| | - Georgia Dermentzaki
- Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Evangelia Dimitriou
- Department of Enzymology and Cellular Function, Institute of Child Health, Athens, Greece
| | - Ioannis Monopolis
- Department of Enzymology and Cellular Function, Institute of Child Health, Athens, Greece
| | - Nick Dekker
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | - Hans Aerts
- Department of Medical Biochemistry, Academic Medical Center, Amsterdam, The Netherlands
| | - Leonidas Stefanis
- Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece; Second Department of Neurology, National and Kapodistrian University of Athens Medical School, Athens, Greece
| | - Helen Michelakakis
- Department of Enzymology and Cellular Function, Institute of Child Health, Athens, Greece.
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Kramer G, Woolerton Y, van Straalen JP, Vissers JPC, Dekker N, Langridge JI, Beynon RJ, Speijer D, Sturk A, Aerts JMFG. Accuracy and Reproducibility in Quantification of Plasma Protein Concentrations by Mass Spectrometry without the Use of Isotopic Standards. PLoS One 2015; 10:e0140097. [PMID: 26474480 PMCID: PMC4608811 DOI: 10.1371/journal.pone.0140097] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/22/2015] [Indexed: 12/28/2022] Open
Abstract
Background Quantitative proteomic analysis with mass spectrometry holds great promise for simultaneously quantifying proteins in various biosamples, such as human plasma. Thus far, studies addressing the reproducible measurement of endogenous protein concentrations in human plasma have focussed on targeted analyses employing isotopically labelled standards. Non-targeted proteomics, on the other hand, has been less employed to this end, even though it has been instrumental in discovery proteomics, generating large datasets in multiple fields of research. Results Using a non-targeted mass spectrometric assay (LCMSE), we quantified abundant plasma proteins (43 mg/mL—40 ug/mL range) in human blood plasma specimens from 30 healthy volunteers and one blood serum sample (ProteomeXchange: PXD000347). Quantitative results were obtained by label-free mass spectrometry using a single internal standard to estimate protein concentrations. This approach resulted in quantitative results for 59 proteins (cut off ≥11 samples quantified) of which 41 proteins were quantified in all 31 samples and 23 of these with an inter-assay variability of ≤ 20%. Results for 7 apolipoproteins were compared with those obtained using isotope-labelled standards, while 12 proteins were compared to routine immunoassays. Comparison of quantitative data obtained by LCMSE and immunoassays showed good to excellent correlations in relative protein abundance (r = 0.72–0.96) and comparable median concentrations for 8 out of 12 proteins tested. Plasma concentrations of 56 proteins determined by LCMSE were of similar accuracy as those reported by targeted studies and 7 apolipoproteins quantified by isotope-labelled standards, when compared to reference concentrations from literature. Conclusions This study shows that LCMSE offers good quantification of relative abundance as well as reasonable estimations of concentrations of abundant plasma proteins.
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Affiliation(s)
- Gertjan Kramer
- Department of Medical Biochemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
- * E-mail:
| | - Yvonne Woolerton
- Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Jan P. van Straalen
- Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
| | | | - Nick Dekker
- Department of Medical Biochemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
| | | | - Robert J. Beynon
- Centre for Proteome Research, Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Dave Speijer
- Department of Medical Biochemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
| | - Auguste Sturk
- Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
| | - Johannes M. F. G. Aerts
- Department of Medical Biochemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands
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5
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Dekker N, Hermens RP, de Wilt JH, van Zelst-Stams WA, Hoogerbrugge N. Improving recognition and referral of patients with an increased familial risk of colorectal cancer: results from a randomized controlled trial. Colorectal Dis 2015; 17:499-510. [PMID: 25524559 DOI: 10.1111/codi.12880] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 11/30/2014] [Indexed: 02/08/2023]
Abstract
AIM Only 12-49% of colorectal cancer (CRC) patients and their first-degree relatives with an increased familial CRC risk are referred for cancer prevention measures (surveillance colonoscopies or genetic counselling). The study was performed to evaluate the effectiveness and feasibility of a novel strategy to improve the uptake of genetic counselling for high risk individuals and surveillance colonoscopy for moderate risk groups. METHOD Eighteen hospitals participated in a clustered randomized controlled trial. Patients in nine hospitals received usual care (group A). Nine other hospitals received the novel strategy (group B) including access to a website for patients and clinicians, patient-targeted brochures and clinician-targeted education and pocket referral cards. Data before and after dissemination of the strategy were collected from questionnaires and medical records. RESULTS Data were complete for 358 (44%) of 820 CRC patients and 50 (36%) of 137 clinicians before dissemination of the strategy and 392/862 patients (45%) and 47/137 clinicians (34%) after. Referral for cancer prevention measures was assessed at a median of 8 (2-12) months after CRC diagnosis in groups A and B before the dissemination of the strategy and in group A after. In group B referral was assessed at a median of 9 (4-11) months after the dissemination of the strategy. Uptake of genetic counselling by high risk patients was equal in groups A and B, being 33% before and 15% after (P = 0.003). Uptake of surveillance colonoscopy by moderate risk relatives did not change significantly (group A, 36% before vs 41% after; group B, 33% before vs 19% after). In group B 94/140 patients (67%) and 25/72 clinicians (35%) visited the website and 34/140 (24%) patients read the brochure. Patients valued clinicians' information as most useful, followed by the patient brochure. Clinicians preferred pocket cards and education. CONCLUSION Our strategy did not improve referral for cancer prevention measures. Although the newly offered strategy elements were appreciated, patients preferred clinicians' advice regarding referral for cancer prevention measures. It may be useful to aim future interventions at healthcare professionals rather than patients to improve the prevention of familial cancer.
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Affiliation(s)
- N Dekker
- Scientific Institute for Quality of Healthcare, Radboud University Medical Centre, Nijmegen, The Netherlands.,Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - R P Hermens
- Scientific Institute for Quality of Healthcare, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - J H de Wilt
- Department of Surgery, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - W A van Zelst-Stams
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - N Hoogerbrugge
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands.,Department of Medical Oncology, Radboud University Medical Centre, Nijmegen, The Netherlands
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6
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Dekker N, Van Leeuwen F, Van 't Veer M, Janus C, Krol A, Van der Maazen R, Van Imhoff G, Zijlstra J, Ong F, Borger J, Roesink J, Poortmans P, Kersten M, Vos-Westerman J, Lybeert M, Schimmel E, Rutten E, Schippers M, Kusumanto Y, Smit W, Muller K, Van Kampen E, Raemaekers J, Aleman B. OC-0268: A Dutch nationwide survivorship care programme for (non-) Hodgkin lymphoma survivors. Radiother Oncol 2015. [DOI: 10.1016/s0167-8140(15)40266-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Mirzaian M, Wisse P, Ferraz MJ, Gold H, Donker-Koopman WE, Verhoek M, Overkleeft HS, Boot RG, Kramer G, Dekker N, Aerts JM. Mass spectrometric quantification of glucosylsphingosine in plasma and urine of type 1 Gaucher patients using an isotope standard. Blood Cells Mol Dis 2015; 54:307-14. [DOI: 10.1016/j.bcmd.2015.01.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 01/08/2015] [Accepted: 01/11/2015] [Indexed: 11/15/2022]
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8
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Pavlova EV, Archer J, Wang S, Dekker N, Aerts JM, Karlsson S, Cox TM. Inhibition of UDP-glucosylceramide synthase in mice prevents Gaucher disease-associated B-cell malignancy. J Pathol 2015; 235:113-24. [PMID: 25256118 DOI: 10.1002/path.4452] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 09/01/2014] [Accepted: 09/19/2014] [Indexed: 02/02/2023]
Abstract
Clonal B-cell proliferation is a frequent manifestation of Gaucher disease - a sphingolipidosis associated with a high risk of multiple myeloma and non-Hodgkin lymphoma. Gaucher disease is caused by genetic deficiency of acid β-glucosidase, the natural substrates of which (β-d-glucosylceramide and β-d-glucosylsphingosine) accumulate, principally in macrophages. Mice with inducible deficiency of β-glucosidase [Gba(tm1Karl/tm1Karl)Tg(MX1-cre)1Cgn/0] serve as an authentic model of human Gaucher disease; we have recently reported clonal B-cell proliferation accompanied by monoclonal serum paraproteins and cognate tumours in these animals. To explore the relationship between B-cell malignancy and the biochemical defect, we treated Gaucher mice with eliglustat tartrate (GENZ 112638), a potent and selective inhibitor of the first committed step in glycosphingolipid biosynthesis. Twenty-two Gaucher mice received 300 mg/kg of GENZ 112638 daily for 3-10 months from 6 weeks of age. Plasma concentrations of β-d-glucosylceramide and the unacylated glycosphingolipid, β-d-glucosylsphingosine, declined. After administration of GENZ 112638 to Gaucher mice for 3-10 months, serum paraproteins were not detected and there was a striking reduction in the malignant lymphoproliferation: neither lymphomas nor plasmacytomas were found in animals that had received the investigational agent. In contrast, 14 out of 60 Gaucher mice without GENZ 112638 treatment developed these tumours; monoclonal paraproteins were detected in plasma from 18 of the 44 age-matched mice with Gaucher disease that had not received GENZ 112638. Long-term inhibition of glycosphingolipid biosynthesis suppresses the development of spontaneous B-cell lymphoma and myeloma in Gaucher mice.
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Affiliation(s)
- Elena V Pavlova
- Department of Medicine, University of Cambridge, Cambridge, UK
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9
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Moraitou M, Dimitriou E, Dekker N, Monopolis I, Aerts J, Michelakakis H. Gaucher disease: Plasmalogen levels in relation to primary lipid abnormalities and oxidative stress. Blood Cells Mol Dis 2014; 53:30-3. [DOI: 10.1016/j.bcmd.2014.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 01/13/2014] [Accepted: 01/18/2014] [Indexed: 10/25/2022]
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10
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Dekker N, Hermens RPMG, Mensenkamp AR, van Zelst-Stams WAG, Hoogerbrugge N. Easy-to-use online referral test detects most patients with a high familial risk of colorectal cancer. Colorectal Dis 2014; 16:O26-34. [PMID: 24034789 DOI: 10.1111/codi.12407] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Accepted: 06/10/2013] [Indexed: 02/08/2023]
Abstract
AIM Currently only 12-30% of individuals with a high risk of Lynch syndrome, the most common hereditary colorectal cancer (CRC) syndrome, are referred for genetic counselling. We assessed the sensitivity, usability and user experiences of a new online referral test aimed at improving referral of high-risk individuals for genetic counselling. METHOD Sensitivity was assessed by entering pedigree data from high-risk individuals (i.e. Lynch syndrome mutation carriers) into the referral test to determine whether genetic counselling was recommended. For usability, we assessed nonmedical staff members' ability to determine referral, according to guidelines, in seven fictive clinical cases using the referral test after minimal training. Real-life users answered questions about their experience with the referral test. RESULT Sensitivity of the referral test was 91% for mutation carriers with CRC (n = 164) and 73% for all affected and nonaffected mutation carriers (n = 420). Nonmedical staff members (n = 20) determined referral according to guidelines in 84% of cases using the referral test. Ten per cent (256/2470) of real-life users provided feedback about experiences; of those, 71% reported that the referral test increased reassurance, certainty about their familial risk and/or certainty about referral. CONCLUSION The referral test has a high sensitivity in detecting individuals with a high risk of Lynch syndrome and is suitable for use in clinical practice. Widespread use of the referral test should improve cancer prevention in high-risk patients and their relatives.
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Affiliation(s)
- N Dekker
- Scientific Institute for Quality of Healthcare, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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11
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Pavlova E, Wang S, Archer J, Dekker N, Aerts J, Karlsson S, Cox T. B cell lymphoma and myeloma in murine Gaucher's disease.
J Pathol
2013; 231: 88–97. J Pathol 2013. [DOI: 10.1002/path.4264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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12
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Pavlova EV, Wang SZ, Archer J, Dekker N, Aerts JMFG, Karlsson S, Cox TM. B cell lymphoma and myeloma in murine Gaucher's disease. J Pathol 2013; 231:88-97. [PMID: 23775597 DOI: 10.1002/path.4227] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 05/20/2013] [Accepted: 06/01/2013] [Indexed: 11/08/2022]
Abstract
Multiple myeloma and B cell lymphoma are leading causes of death in Gaucher's disease but the nature of the stimulus driving the often noted clonal expansion of immunoglobulin-secreting B cells and cognate lymphoid malignancy is unknown. We investigated the long-term development of B cell malignancies in an authentic model of non-neuronopathic Gaucher's disease in mice: selective deficiency of β-glucocerebrosidase in haematopoietic cells [Gba(tm1Karl/tm1Karl)Tg(Mx1-cre)1Cgn/0, with excision of exons 9-11 of the murine GBA1 gene, is induced by poly[I:C]. Mice with Gaucher's disease showed visceral storage of β-glucosylceramide and greatly elevated plasma β-glucosylsphingosine [median 57.9 (range 19.8-159) nm; n = 39] compared with control mice from the same strain [median 0.56 (range 0.04-1.38) nm; n = 29] (p < 0.0001). Sporadic fatal B cell lymphomas developed in 11 of 21 GD mice (6-24 months) but only two of eight control animals developed tumours by age 24 months. Unexpectedly, most mice with overt lymphoma had absent or few Gaucher cells but local inflammatory macrophages were present. Eleven of 39 of Gaucher mice developed monoclonal gammopathy, but in the control group only one animal of 25 had clonal immunoglobulin abnormalities. Seven of 10 of the B cell lymphomas were found to secrete a monoclonal paraprotein and the lymphomas stained intensely for pan-B cell markers; reactive T lymphocytes were also present in tumour tissue. In the Gaucher mouse strain, it was notable that, as in patients with this disease, CD138(+) plasma cells frequently surrounded splenic macrophages engorged with glycosphingolipid. Our strain of mice, with inducible deficiency of β-glucocerebrosidase in haematopoietic cells and a high frequency of sporadic lethal B cell malignancies, faithfully recapitulates human Gaucher's disease: it serves as a tractable model to investigate the putative role of bioactive sphingolipids in the control of B cell proliferation and the pathogenesis of myelomatosis-the most prevalent human cancer associated with this disorder.
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Affiliation(s)
- E V Pavlova
- Department of Medicine, University of Cambridge, Addenbrooke’s Hospital, Cambridge, UK.
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13
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Backmark AE, Olivier N, Snijder A, Gordon E, Dekker N, Ferguson AD. Fluorescent probe for high-throughput screening of membrane protein expression. Protein Sci 2013; 22:1124-32. [PMID: 23776061 DOI: 10.1002/pro.2297] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 06/02/2013] [Accepted: 06/06/2013] [Indexed: 12/20/2022]
Abstract
Screening of protein variants requires specific detection methods to assay protein levels and stability in crude mixtures. Many strategies apply fluorescence-detection size-exclusion chromatography (FSEC) using green fluorescent protein (GFP) fusion proteins to qualitatively monitor expression, stability, and monodispersity. However, GFP fusion proteins have several important disadvantages; including false-positives, protein aggregation after proteolytic removal of GFP, and reductions in protein yields without the GFP fusion. Here we describe a FSEC screening strategy based on a fluorescent multivalent NTA probe that interacts with polyhistidine-tags on target proteins. This method overcomes the limitations of GFP fusion proteins, and can be used to rank protein production based on qualitative and quantitative parameters. Domain boundaries of the human G-protein coupled adenosine A2a receptor were readily identified from crude detergent-extracts of a library of construct variants transiently produced in suspension-adapted HEK293-6E cells. Well expressing clones of MraY, an important bacterial infection target, could be identified from a library of 24 orthologs. This probe provides a highly sensitive tool to detect target proteins to expression levels down to 0.02 mg/L in crude lysate, and requires minimal amounts of cell culture.
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Affiliation(s)
- A E Backmark
- Discovery Sciences, Reagents and Assay Development, AstraZeneca Pharmaceuticals, Mölndal, Sweden
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14
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Dekker N, Hermens RPMG, Nagengast FM, van Zelst-Stams WAG, Hoogerbrugge N. Familial colorectal cancer risk assessment needs improvement for more effective cancer prevention in relatives. Colorectal Dis 2013; 15:e175-85; discussion p.e185. [PMID: 23451840 DOI: 10.1111/codi.12117] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 09/29/2012] [Indexed: 12/15/2022]
Abstract
AIM Twelve to thirty % of colorectal cancer (CRC) patients and relatives with an increased familial risk of CRC are referred for preventive measures. New guidelines recommend genetic counselling for high-risk families and surveillance colonoscopy for moderate-risk families. Assessment of familial risk of CRC and referral rates for these preventive measures were determined 1 year after the introduction of new guidelines. METHOD Assessment of familial risk of CRC and referral for preventive measures were measured in clinical practice among 358 patients with CRC in 18 hospitals using medical records and questionnaires. Additionally, a knowledge survey was performed among 312 clinicians. RESULTS Sixty-seven % of patients with an increased familial risk (n = 65/97) were referred for preventive measures, as were 23% (61/261) of low-risk patients. The uptake of genetic counselling in high-risk families was 33% (12/36). The uptake of surveillance colonoscopy in moderate-risk families was 34% (21/61). In the knowledge survey clinicians correctly determined familial risk in 55% and preventive measures in 65% of cases. CONCLUSION Currently 67% of individuals with an increased familial risk of CRC were referred for preventive measures. Only one-third were referred in accordance with guidelines.
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Affiliation(s)
- N Dekker
- Scientific Institute for Quality of Healthcare, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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15
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Gold H, Mirzaian M, Dekker N, Joao Ferraz M, Lugtenburg J, Codée JDC, van der Marel GA, Overkleeft HS, Linthorst GE, Groener JEM, Aerts JM, Poorthuis BJHM. Quantification of globotriaosylsphingosine in plasma and urine of fabry patients by stable isotope ultraperformance liquid chromatography-tandem mass spectrometry. Clin Chem 2012; 59:547-56. [PMID: 23237761 DOI: 10.1373/clinchem.2012.192138] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Biochemical markers that accurately reflect the severity and progression of disease in patients with Fabry disease and their response to treatment are urgently needed. Globotriaosylsphingosine, also called lysoglobotriaosylceramide (lysoGb3), is a promising candidate biomarker. METHODS We synthesized lysoGb3 and isotope-labeled [5,6,7,8,9] (13)C5-lysoGb3 (internal standard). After addition of the internal standard to 25 μL plasma or 400 μL urine from patients with Fabry disease and healthy controls, samples were extracted with organic solvents and the lysoGb3 concentration was quantified by UPLC-ESI-MS/MS (ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry). Calibration curves were constructed with control plasma and urine supplemented with lysoGb3. In addition to lysoGb3, lyso-ene-Gb3 was quantified. Quantification was achieved by multiple reaction monitoring of the transitions m/z 786.4 > 282.3 [M+H](+) for lysoGb3, m/z 791.4 > 287.3 [M+H](+) for [5,6,7,8,9] (13)C5-lysoGb3, and 784.4 > 280.3 [M+H](+) for lyso-ene-Gb3. RESULTS The mean (SD) plasma lysoGb3 concentration from 10 classically affected Fabry hemizygotes was 94.4 (25.8) pmol/mL (range 52.7-136.8 pmol/mL), from 10 classically affected Fabry heterozygotes 9.6 (5.8) pmol/mL (range 4.1-23.5 pmol/mL), and from 20 healthy controls 0.4 (0.1) pmol/mL (range 0.3-0.5 pmol/mL). Lyso-ene-Gb3 concentrations were 10%-25% of total lysoGb3. The urine concentration of lysoGb3 was 40-480 times lower than in corresponding plasma samples. Lyso-ene-Gb3 concentrations in urine were comparable or even higher than the corresponding lysoGb3 concentrations. CONCLUSIONS This assay for the quantification of lysoGb3 and lyso-ene-Gb3 in human plasma and urine samples will be an important tool in the diagnosis of Fabry disease and for monitoring the effect of enzyme replacement therapy in patients with Fabry disease.
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Affiliation(s)
- Henrik Gold
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
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16
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Dekker N, Meijer J, Koeter M, van den Brink W, van Beveren N, Kahn RS, Linszen DH, van Os J, Wiersma D, Bruggeman R, Cahn W, de Haan L, Krabbendam L, Myin-Germeys I. Age at onset of non-affective psychosis in relation to cannabis use, other drug use and gender. Psychol Med 2012; 42:1903-1911. [PMID: 22452790 DOI: 10.1017/s0033291712000062] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Cannabis use is associated with an earlier age at onset of psychotic illness. The aim of the present study was to examine whether this association is confounded by gender or other substance use in a large cohort of patients with a non-affective psychotic disorder. METHOD In 785 patients with a non-affective psychotic disorder, regression analysis was used to investigate the independent effects of gender, cannabis use and other drug use on age at onset of first psychosis. RESULTS Age at onset was 1.8 years earlier in cannabis users compared to non-users, controlling for gender and other possible confounders. Use of other drugs did not have an additional effect on age at onset when cannabis use was taken into account. In 63.5% of cannabis-using patients, age at most intense cannabis use preceded the age at onset of first psychosis. In males, the mean age at onset was 1.3 years lower than in females, controlling for cannabis use and other confounders. CONCLUSIONS Cannabis use and gender are independently associated with an earlier onset of psychotic illness. Our findings also suggest that cannabis use may precipitate psychosis. More research is needed to clarify the neurobiological factors that make people vulnerable to this precipitating effect of cannabis.
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Affiliation(s)
- N Dekker
- Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
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17
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Smeerdijk M, Keet R, Dekker N, van Raaij B, Krikke M, Koeter M, de Haan L, Barrowclough C, Schippers G, Linszen D. Motivational interviewing and interaction skills training for parents to change cannabis use in young adults with recent-onset schizophrenia: a randomized controlled trial. Psychol Med 2012; 42:1627-1636. [PMID: 22152121 DOI: 10.1017/s0033291711002832] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Cannabis use by people with schizophrenia has been found to be associated with family distress and poor clinical outcomes. Interventions to reduce drug use in this patient group have had limited efficacy. This study evaluated the effectiveness of a novel intervention for parents of young adults with recent-onset schizophrenia consisting of family-based motivational interviewing and interaction skills (Family Motivational Intervention, FMI) in comparison with routine family support (RFS). METHOD In a trial with 75 patients who used cannabis and received treatment for recent-onset schizophrenia, 97 parents were randomly assigned to either FMI (n=53) or RFS (n=44). Assessments were conducted at baseline and 3 months after completion of the family intervention by an investigator who remained blind throughout the study about the assignment of the parents. RESULTS At follow-up, patients' frequency and quantity of cannabis use was significantly more reduced in FMI than in RFS (p<0.05 and p<0.04 respectively). Patients' craving for cannabis was also significantly reduced in FMI whereas there was a small increase in RFS (p=0.01). There was no difference between FMI and RFS with regard to patients' other substance use and general level of functioning. Both groups showed significant improvements in parental distress and sense of burden. CONCLUSIONS Training parents in motivational interviewing and interaction skills is feasible and effective in reducing cannabis use among young adults with recent-onset schizophrenia. However, FMI was not more effective than RFS in increasing patients' general level of functioning and in reducing parents' stress and sense of burden.
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Affiliation(s)
- M Smeerdijk
- Department of Psychiatry, Academic Medical Centre, Amsterdam, The Netherlands.
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18
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Meijer JH, Dekker N, Koeter MW, Quee PJ, van Beveren NJM, Meijer CJ. Cannabis and cognitive performance in psychosis: a cross-sectional study in patients with non-affective psychotic illness and their unaffected siblings. Psychol Med 2012; 42:705-716. [PMID: 21899795 DOI: 10.1017/s0033291711001656] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The relationship between cannabis use and cognitive functioning in patients with psychosis has yielded contradictory findings. In individuals at genetic high risk for psychosis, information is sparse. The aim of this study was to assess the association between recency and frequency of cannabis use and cognitive functioning in patients with psychosis and their unaffected siblings. METHOD We conducted a cross-sectional study in 956 patients with non-affective psychosis, 953 unaffected siblings, and 554 control subjects. Participants completed a cognitive test battery including assessments of verbal learning, set shifting, sustained attention, processing speed, working memory, acquired knowledge, reasoning and problem solving and social cognition. Cannabis use was assessed by urinalysis and by the Composite International Diagnostic Interview. Using random-effect regression models the main effects of cannabis (recency and frequency) and the interaction with status (patient, sibling, control) on cognitive functioning were assessed. RESULTS Current cannabis use was associated with poorer performance on immediate verbal learning, processing speed and working memory (Cohen's d -0.20 to -0.33, p<0.005). Lifetime cannabis use was associated with better performance on acquired knowledge, facial affect recognition and face identity recognition (Cohen's d+0.17 to +0.33, p<0.005). There was no significant interaction between cannabis and status on cognitive functioning. CONCLUSIONS Lifetime cannabis-using individuals might constitute a subgroup with a higher cognitive potential. The residual effects of cannabis may impair short-term memory and processing speed.
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Affiliation(s)
- J H Meijer
- Department of Psychiatry, Academic Medical Center, Amsterdam, The Netherlands
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19
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Aerts JMFG, Kallemeijn WW, Wegdam W, Joao Ferraz M, van Breemen MJ, Dekker N, Kramer G, Poorthuis BJ, Groener JEM, Cox-Brinkman J, Rombach SM, Hollak CEM, Linthorst GE, Witte MD, Gold H, van der Marel GA, Overkleeft HS, Boot RG. Biomarkers in the diagnosis of lysosomal storage disorders: proteins, lipids, and inhibodies. J Inherit Metab Dis 2011; 34:605-19. [PMID: 21445610 PMCID: PMC3109260 DOI: 10.1007/s10545-011-9308-6] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 01/21/2011] [Accepted: 02/17/2011] [Indexed: 12/23/2022]
Abstract
A biomarker is an analyte indicating the presence of a biological process linked to the clinical manifestations and outcome of a particular disease. In the case of lysosomal storage disorders (LSDs), primary and secondary accumulating metabolites or proteins specifically secreted by storage cells are good candidates for biomarkers. Clinical applications of biomarkers are found in improved diagnosis, monitoring disease progression, and assessing therapeutic correction. These are illustrated by reviewing the discovery and use of biomarkers for Gaucher disease and Fabry disease. In addition, recently developed chemical tools allowing specific visualization of enzymatically active lysosomal glucocerebrosidase are described. Such probes, coined inhibodies, offer entirely new possibilities for more sophisticated molecular diagnosis, enzyme replacement therapy monitoring, and fundamental research.
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Affiliation(s)
- Johannes M F G Aerts
- Sphinx-Amsterdam Lysosome Center, Departments of Medical Biochemistry and Internal Medicine, Academic Medical Centre, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.
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20
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Dekker N, van Rossum LGM, Van Vugt-van Pinxteren M, van Stiphout SHC, Hermens RPMG, van Zelst-Stams WAG, van Oijen MGH, Laheij RJF, Jansen JBMJ, Hoogerbrugge N. Adding familial risk assessment to faecal occult blood test can increase the effectiveness of population-based colorectal cancer screening. Eur J Cancer 2011; 47:1571-7. [PMID: 21367600 DOI: 10.1016/j.ejca.2011.01.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 01/27/2011] [Accepted: 01/31/2011] [Indexed: 12/11/2022]
Abstract
BACKGROUND The Dutch Health Council recently recommended the introduction of a colorectal cancer (CRC) screening programme by faecal occult blood testing (FOBT) for individuals aged 55-75 at population risk of CRC. Individuals at an increased familial CRC risk (≥ 2 times population risk) should be identified at a younger age, so they and their relatives can receive earlier, more intensive surveillance instead of FOBT. AIMS To determine the percentage of participants with a positive FOBT in a CRC screening programme with an increased familial CRC risk. METHODS In a population-based study, 10,569 individuals aged 50-75 received an FOBT. Individuals with a positive FOBT were invited for colonoscopy and familial risk assessment. Participants with an average familial CRC risk were compared to those with an increased risk. Increased familial CRC risk was defined as a cumulative lifetime risk of CRC of at least 10%. RESULTS Of 6001 participants, 430 had a positive FOBT, of whom 324 (63% males; mean age 63 years) completed colonoscopy and familial risk assessment. CRC (n=22) and/or advanced adenomas (n=122) were found in 133 participants. Familial CRC risk was increased in 6% of participants with a positive FOBT. No significant differences were found between participants with an average versus an increased familial CRC risk. CONCLUSION Six percent of participants with a positive FOBT had an increased familial CRC risk. Identifying at-risk participants enables them and their relatives to undergo regular colonoscopies. Adding familial risk assessment to FOBT screening may thus prevent a substantial number of CRCs.
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Affiliation(s)
- N Dekker
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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21
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van Breemen MJ, Rombach SM, Dekker N, Poorthuis BJ, Linthorst GE, Zwinderman AH, Breunig F, Wanner C, Aerts JM, Hollak CE. Reduction of elevated plasma globotriaosylsphingosine in patients with classic Fabry disease following enzyme replacement therapy. Biochim Biophys Acta Mol Basis Dis 2011; 1812:70-6. [DOI: 10.1016/j.bbadis.2010.09.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 09/09/2010] [Accepted: 09/13/2010] [Indexed: 11/29/2022]
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22
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Aerts JM, Boot RG, van Eijk M, Groener J, Bijl N, Lombardo E, Bietrix FM, Dekker N, Groen AK, Ottenhoff R, van Roomen C, Aten J, Serlie M, Langeveld M, Wennekes T, Overkleeft HS. Glycosphingolipids and insulin resistance. Adv Exp Med Biol 2011; 721:99-119. [PMID: 21910085 DOI: 10.1007/978-1-4614-0650-1_7] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glycosphingolipids are structural membrane components, residing largely in the plasma membrane with their sugar-moieties exposed at the cell's surface. In recent times a crucial role for glycosphingolipids in insulin resistance has been proposed. A chronic state of insulin resistance is a rapidly increasing disease condition in Western and developing countries. It is considered to be the major underlying cause of the metabolic syndrome, a combination of metabolic abnormalities that increases the risk for an individual to develop Type 2 diabetes, obesity, cardiovascular disease, polycystic ovary syndrome and nonalcoholic fatty liver disease. As discussed in this chapter, the evidence for a direct regulatory interaction of glycosphingolipids with insulin signaling is still largely indirect. However, the recent finding in animal models that pharmacological reduction of glycosphingolipid biosynthesis ameliorates insulin resistance and prevents some manifestations of metabolic syndrome, supports the view that somehow glycosphingolipids act as critical regulators, Importantly, since reductions in glycosphingolipid biosynthesis have been found to be well tolerated, such approaches may have a therapeutic potential.
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Affiliation(s)
- Johannes M Aerts
- Department of Medical Biochemistry, University of Amsterdam, The Netherlands.
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23
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Dekker N, Smeerdijk AM, Wiers RW, Duits JH, van Gelder G, Houben K, Schippers G, Linszen DH, de Haan L. Implicit and explicit affective associations towards cannabis use in patients with recent-onset schizophrenia and healthy controls. Psychol Med 2010; 40:1325-1336. [PMID: 19917142 DOI: 10.1017/s0033291709991814] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Cannabis use is common in patients with recent-onset schizophrenia and this is associated with poor disease outcome. More insight in the cognitive-motivational processes related to cannabis use in schizophrenia may inform treatment strategies. The present study is the first known to compare implicit and explicit cannabis associations in individuals with and without psychotic disorder. METHOD Participants consisted of 70 patients with recent-onset psychotic disorder and 61 healthy controls with various levels of cannabis use. Three Single-Category Implicit Association Tests (SC-IAT) were used to assess 'relaxed', 'active' and 'negative' implicit associations towards cannabis use. Explicit expectancies of cannabis use were assessed with a questionnaire using the same words as the SC-IAT. RESULTS There were no differences in implicit associations between patients and controls; however, patients scored significantly higher on explicit negative affect expectancies than controls. Both groups demonstrated strong negative implicit associations towards cannabis use. Explicit relaxed expectancies were the strongest predictors of cannabis use and craving. There was a trend for implicit active associations to predict craving. CONCLUSIONS The findings indicate that patients suffering from schizophrenia have associations towards cannabis similar to controls, but they have stronger negative explicit cannabis associations. The strong negative implicit associations towards cannabis could imply that users of cannabis engage in a behaviour they do not implicitly like. Explicit relaxing expectancies of cannabis might be an important mediator in the continuation of cannabis use in patients and controls.
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Affiliation(s)
- N Dekker
- Department of Psychiatry, Academic Medical Centre, Amsterdam, The Netherlands
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24
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Dekker N, Linszen DH, De Haan L. Reasons for cannabis use and effects of cannabis use as reported by patients with psychotic disorders. Psychopathology 2009; 42:350-60. [PMID: 19752588 DOI: 10.1159/000236906] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Accepted: 02/13/2009] [Indexed: 11/19/2022]
Abstract
BACKGROUND Cannabis is one of the most commonly used substances in patients with a psychotic disorder and is associated with a higher risk of psychotic relapses. Identifying reasons for cannabis use and subjective effects in patients with psychotic disorders can provide insight into the functions of cannabis use, and this may lead to targeted interventions. METHODS A literature search of the PubMed and PsycINFO databases for articles published from 1985 till 2008 was carried out to review studies that examined self-reported reasons for cannabis use and self-reported effects of cannabis use in patients with psychotic disorders. RESULTS Only a few studies were found that specifically assessed reasons for and effects of cannabis use. Despite the heterogeneity in the study samples and methodology, patients commonly reported that their reasons for cannabis use were enhancement of positive affect, relief of dysphoria and social enhancement. Fewer patients reported reasons related to relief of psychotic symptoms or relief of side effects of medication. Frequently reported positive effects of cannabis were positive changes in affect and relaxation. A large proportion of patients reported that cannabis negatively affected positive symptoms. CONCLUSIONS Patients suffering from psychotic disorder report using cannabis mainly for affect regulation and socialization, despite the awareness that cannabis has a negative effect on positive symptoms. In spite of the heterogeneity of the studies, the results turned out to be broadly comparable and support the external validity of this review to a broad range of cannabis-using patients with psychotic disorder.
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Affiliation(s)
- N Dekker
- Department of Psychiatry, Academic Medical Centre, Amsterdam, The Netherlands.
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25
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Dekker N, van Rijssel J, Distel B, Hochstenbach F. Role of the alpha-glucanase Agn2p in ascus-wall endolysis following sporulation in fission yeast. Yeast 2007; 24:279-88. [PMID: 17315266 DOI: 10.1002/yea.1464] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
During sporulation in the ascomyceteous fungus Schizosaccharomyces pombe, diploid cells undergo differentiation into asci containing four haploid ascospores, which are highly resistant to environmental stresses. Although the morphogenetic processes involved in ascospore formation have been studied extensively, little is known about the molecular mechanism that ensures the release of mature ascospores from the ascus, allowing their dispersal into the environment. Recently, we identified Agn2p as the paralogue of the characterized endo-(1,3)-alpha-glucanase Agn1p, and observed that asci deleted for agn2 are defective in ascospore dispersal. Here, we focus on the cellular and biochemical functions of Agn2p. By placing agn2 under the control of an inducible promoter, we show that expression of agn2 is required for the efficient release of ascospores from their asci. Furthermore, we characterize the enzyme activity of purified recombinant Agn2p and show that Agn2p, like Agn1p, is an endo-(1,3)-alpha-glucanase that produces predominantly (1,3)-alpha-glucan pentasaccharides. Finally, we demonstrate that exogenous addition of purified Agn2p liberated the ascospores from asci deleted for agn2. We propose that Agn2p participates in the endolysis of the ascus wall by hydrolysing its (1,3)-alpha-glucan, thereby assisting in the release of ascospores.
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Affiliation(s)
- Nick Dekker
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands
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26
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Vos A, Dekker N, Distel B, Leunissen JAM, Hochstenbach F. Role of the Synthase Domain of Ags1p in Cell Wall α-Glucan Biosynthesis in Fission Yeast. J Biol Chem 2007; 282:18969-79. [PMID: 17472966 DOI: 10.1074/jbc.m605147200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cell wall is important for maintenance of the structural integrity and morphology of fungal cells. Besides beta-glucan and chitin, alpha-glucan is a major polysaccharide in the cell wall of many fungi. In the fission yeast Schizosaccharomyces pombe, cell wall alpha-glucan is an essential component, consisting mainly of (1,3)-alpha-glucan with approximately 10% (1,4)-linked alpha-glucose residues. The multidomain protein Ags1p is required for alpha-glucan biosynthesis and is conserved among cell wall alpha-glucan-containing fungi. One of its domains shares amino acid sequence motifs with (1,4)-alpha-glucan synthases such as bacterial glycogen synthases and plant starch synthases. Whether Ags1p is involved in the synthesis of the (1,4)-alpha-glucan constituent of cell wall alpha-glucan had remained unclear. Here, we show that overexpression of Ags1p in S. pombe cells results in accumulation of (1,4)-alpha-glucan. To determine whether the synthase domain of Ags1p is responsible for this activity, we overexpressed Ags1p-E1526A, which carries a mutation in a putative catalytic residue of the synthase domain, but observed no accumulation of (1,4)-alpha-glucan. Compared with wild-type Ags1p, this mutant Ags1p showed a markedly reduced ability to complement the cell lysis phenotype of the temperature-sensitive ags1-1 mutant. Therefore, we conclude that, in S. pombe, the production of (1,4)-alpha-glucan by the synthase domain of Ags1p is important for the biosynthesis of cell wall alpha-glucan.
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Affiliation(s)
- Alina Vos
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands
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27
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Grün CH, Dekker N, Nieuwland AA, Klis FM, Kamerling JP, Vliegenthart JFG, Hochstenbach F. Mechanism of action of theendo-(1 → 3)-α-glucanase MutAp from the mycoparasitic fungusTrichoderma harzianum. FEBS Lett 2006; 580:3780-6. [PMID: 16780840 DOI: 10.1016/j.febslet.2006.05.062] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Revised: 05/25/2006] [Accepted: 05/30/2006] [Indexed: 11/26/2022]
Abstract
(1-->3)-alpha-glucanases catalyze the hydrolysis of fungal cell wall (1-->3)-alpha-glucan, and function during cell division of yeasts containing this cell wall component or act in mycoparasitic processes. Here, we characterize the mechanism of action of the (1-->3)-alpha-glucanase MutAp from the mycoparasitic fungus Trichoderma harzianum. We observed that MutAp releases predominantly beta-glucose upon hydrolysis of crystalline (1-->3)-alpha-glucan, indicating inversion of the anomeric configuration. After having identified (1-->3)-alpha-glucan tetrasaccharide as the minimal substrate for MutAp, we showed that reduced (1-->3)-alpha-glucan pentasaccharide is cleaved into a trisaccharide and a reduced disaccharide, demonstrating that MutAp displays endo-hydrolytic activity. We propose a model for the catalytic mechanism of MutAp, whereby the enzyme breaks an intrachain glycosidic linkage of (1-->3)-alpha-glucan, and then continues its hydrolysis towards the non-reducing end by releasing beta-glucose residues in a processive manner.
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Affiliation(s)
- Christian H Grün
- Bijvoet Center, Department of Bio-Organic Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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28
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Dekker N, de Haan A, Hochstenbach F. Transcription regulation of the alpha-glucanase gene agn1 by cell separation transcription factor Ace2p in fission yeast. FEBS Lett 2006; 580:3099-106. [PMID: 16678171 DOI: 10.1016/j.febslet.2006.04.061] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 04/07/2006] [Accepted: 04/19/2006] [Indexed: 10/24/2022]
Abstract
During the final stage of the cell division cycle in the fission yeast Schizosaccharomyces pombe, transcription factor Ace2p activates expression of genes involved in the separation of newly formed daughter cells, such as agn1+, which encodes the alpha-glucanase Agn1p. The agn1 promoter contains three copies of the nucleotide sequence motif CCAGCC, whose presence seems to correlate with Ace2p-mediated transcription activation. Here, we describe a simple plate-based assay utilizing as a reporter the secreted glucoamylase of Arxula adeninivorans to investigate the function of this motif. We show that not all three repeats, but only the two most proximal to the transcription start point, act as an upstream activating sequence (UAS). Finally, we demonstrate that this UAS is essential for agn1 promoter activity in vivo.
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Affiliation(s)
- Nick Dekker
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands
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Dekker N, Speijer D, Grün CH, van den Berg M, de Haan A, Hochstenbach F. Role of the alpha-glucanase Agn1p in fission-yeast cell separation. Mol Biol Cell 2004; 15:3903-14. [PMID: 15194814 PMCID: PMC491845 DOI: 10.1091/mbc.e04-04-0319] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Revised: 05/28/2004] [Accepted: 06/01/2004] [Indexed: 11/11/2022] Open
Abstract
Cell division in the fission yeast Schizosaccharomyces pombe yields two equal-sized daughter cells. Medial fission is achieved by deposition of a primary septum flanked by two secondary septa within the dividing cell. During the final step of cell division, cell separation, the primary septum is hydrolyzed by an endo-(1,3)-beta-glucanase, Eng1p. We reasoned that the cell wall material surrounding the septum, referred to here as the septum edging, also must be hydrolyzed before full separation of the daughter cells can occur. Because the septum edging contains (1,3)-alpha-glucan, we investigated the cellular functions of the putative (1,3)-alpha-glucanases Agn1p and Agn2p. Whereas agn2 deletion results in a defect in endolysis of the ascus wall, deletion of agn1 leads to clumped cells that remained attached to each other by septum-edging material. Purified Agn1p hydrolyzes (1,3)-alpha-glucan predominantly into pentasaccharides, indicating an endo-catalytic mode of hydrolysis. Furthermore, we show that the transcription factors Sep1p and Ace2p regulate both eng1 and agn1 expression in a cell cycle-dependent manner. We propose that Agn1p acts in concert with Eng1p to achieve efficient cell separation, thereby exposing the secondary septa as the new ends of the daughter cells.
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Affiliation(s)
- Nick Dekker
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands
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Drogari-Apiranthitou M, Kuijper EJ, Dekker N, Dankert J. Complement activation and formation of the membrane attack complex on serogroup B Neisseria meningitidis in the presence or absence of serum bactericidal activity. Infect Immun 2002; 70:3752-8. [PMID: 12065518 PMCID: PMC128098 DOI: 10.1128/iai.70.7.3752-3758.2002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Encapsulated meningococci are complement sensitive only in the presence of bactericidal antibodies by yet-unexplored mechanisms. The objective of this study was to investigate the involvement of major bacterial surface constituents on complement activation and membrane attack complex (MAC) formation on serogroup B meningococci in the presence or absence of antibody-dependent serum bactericidal activity (SBA). The strains used were the encapsulated H44/76, five of its variants differing in capsulation and expression of the class 1 porin (PorA), and its lipopolysaccharide (LPS)-deficient isogenic mutant (LPS(-)) pLAK33. Two normal sera, one with high SBA (SBA(+)) and one with no bactericidal activity (SBA(-)) against H44/76 as well as an a-gamma-globulinemic serum were used for sensibilization of the bacteria. C3b and iC3b deposition on H44/76, its unencapsulated variant v24, and pLAK33 was similar in SBA(+) and SBA(-) serum, and no difference was present between the strains. MAC deposition on H44/76 was higher in SBA(+) serum than in SBA(-) serum and the a-gamma-globulinemic serum. The amounts of C3b on H44/76, v24, and pLAK33 in the a-gamma-globulinemic serum were also not different, indicating immunoglobulin G (IgG)- and LPS-independent complement activation. H44/76 PorA(+) and its PorA(-) variant and the v24 PorA(+) and its PorA(-) variant incubated in SBA(-) serum induced comparable amounts of MAC, despite their different serum sensitivities. Complement formation on the surface of the bacteria occurred almost exclusively via the classical pathway, but the considerable amounts of Bb measured in the serum indicated alternative pathway activation in the fluid phase. We conclude that complement deposition on meningococci is, for the most part, independent of classical pathway IgG and is not influenced by the presence of PorA or LPS on the meningococcal surface. Addition of an anti-PorA chimeric antibody to the nonbactericidal normal serum, while promoting a dose-related bacterial lysis, did not influence the amounts of C3b, iC3b, and MAC formed on the bacterial surface. These findings support the hypothesis that proper MAC insertion rather than the quantity of MAC formed on the bacterial surface is of importance for efficient lysis of meningococci.
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Affiliation(s)
- M Drogari-Apiranthitou
- Department of Medical Microbiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
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31
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Tannaes T, Dekker N, Bukholm G, Bijlsma JJ, Appelmelk BJ. Phase variation in the Helicobacter pylori phospholipase A gene and its role in acid adaptation. Infect Immun 2001; 69:7334-40. [PMID: 11705905 PMCID: PMC98819 DOI: 10.1128/iai.69.12.7334-7340.2001] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Previously, we have shown that Helicobacter pylori can spontaneously and reversibly change its membrane lipid composition, producing variants with low or high content of lysophospholipids. The "lyso" variant contains a high percentage of lysophospholipids, adheres better to epithelial cells, and releases more proteins such as urease and VacA, compared to the "normal" variant, which has a low content of lysophospholipids. Prolonged growth of the normal variant at pH 3.5, but not under neutral conditions, leads to enrichment of lyso variant colonies, suggesting that the colony switch is relevant to acid adaptation. In this study we show that the change in membrane lipid composition is due to phase variation in the pldA gene. A change in the (C) tract length of this gene results in reversible frameshifts, translation of a full-length or truncated pldA, and the production of active or inactive outer membrane phospholipase A (OMPLA). The role of OMPLA in determining the colony morphology was confirmed by the construction of an OMPLA-negative mutant. Furthermore, variants with an active OMPLA were able to survive acidic conditions better than variants with the inactive form. This explains why the lyso variant is selected at low pH. Our studies demonstrate that phase variation in the pldA gene, resulting in an active form of OMPLA, is important for survival under acidic conditions. We also demonstrated the active OMPLA genotype in fresh isolates of H. pylori from patients referred to gastroscopy for dyspepsia.
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Affiliation(s)
- T Tannaes
- Institute of Medical Microbiology, University of Oslo, Oslo, Norway.
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32
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Snijder HJ, Van Eerde JH, Kingma RL, Kalk KH, Dekker N, Egmond MR, Dijkstra BW. Structural investigations of the active-site mutant Asn156Ala of outer membrane phospholipase A: function of the Asn-His interaction in the catalytic triad. Protein Sci 2001; 10:1962-9. [PMID: 11567087 PMCID: PMC2374211 DOI: 10.1110/ps.17701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Outer membrane phospholipase A (OMPLA) from Escherichia coli is an integral-membrane enzyme with a unique His-Ser-Asn catalytic triad. In serine proteases and serine esterases usually an Asp occurs in the catalytic triad; its role has been the subject of much debate. Here the role of the uncharged asparagine in the active site of OMPLA is investigated by structural characterization of the Asn156Ala mutant. Asparagine 156 is not involved in maintaining the overall active-site configuration and does not contribute significantly to the thermal stability of OMPLA. The active-site histidine retains an active conformation in the mutant notwithstanding the loss of the hydrogen bond to the asparagine side chain. Instead, stabilization of the correct tautomeric form of the histidine can account for the observed decrease in activity of the Asn156Ala mutant.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, 9747 AG Groningen, The Netherlands
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Hirschberg HJ, Simons JW, Dekker N, Egmond MR. Cloning, expression, purification and characterization of patatin, a novel phospholipase A. Eur J Biochem 2001; 268:5037-44. [PMID: 11589694 DOI: 10.1046/j.0014-2956.2001.02411.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Patatin is the major protein constituent of potato tubers and displays broad esterase activity. The native enzyme actually belongs to a highly homologous multigene family of vacuolar glycoproteins. From these, the patB2 patatin gene was selected and cloned into pUC19 without its signal sequence but with an N-terminal histidine-tag. This patatin was overexpressed under the control of the lac promotor in Escherichia coli strain DH5alpha. The protein was recovered as inclusion bodies, folded into its native state by solubilization in urea and purified to homogeneity. Starting with one gram of inclusion bodies, 19 mg of pure and active recombinant patatin was isolated, with even higher specific activity than the glycosylated wild-type patatin purified from potato tubers. The purified enzyme showed esterolytic activity with p-nitrophenylesters dissolved in Triton X-100 micelles. The activity of patatin on p-nitrophenylesters with different carbon chain lengths showed an optimum for p-nitrophenylesters with 10 carbon atoms. Besides general esterolytic activity, the pure enzyme was found to display high phospholipase A activity in particular with the substrates 1,2-dioctanoyl-sn-glycero-3-phosphocholine (diC(8)PCho) (127 U.mg(-1)) and 1,2-dinonanoyl-sn-glycero-3-phosphocholine (diC(9)PCho) (109 U.mg(-1)). Recently, the structure of human cytosolic PLA(2) (cPLA(2)) was solved, showing a novel Ser-Asp active site dyad [1]. Based on a partial sequence alignment of patatin with human cPLA(2), we propose that patatin contains a similar active site dyad. To verify this assumption, conserved Ser, Asp and His residues in the family of patatins have been modified in patatin B2. Identification of active site residues was based on the observation of correctly folded but inactive variants. This led to the assignment of Ser54 and Asp192 as the active site serine and aspartate residues in patatin B2, respectively.
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Affiliation(s)
- H J Hirschberg
- Department of Enzymology and Protein Engineering, CBLE, Utrecht University, Padualaan 8, De Uithof, 3584 CH Utrecht, the Netherlands
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Kramer RA, Vandeputte-Rutten L, de Roon GJ, Gros P, Dekker N, Egmond MR. Identification of essential acidic residues of outer membrane protease OmpT supports a novel active site. FEBS Lett 2001; 505:426-30. [PMID: 11576541 DOI: 10.1016/s0014-5793(01)02863-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Escherichia coli outer membrane protease OmpT has previously been classified as a serine protease with Ser(99) and His(212) as active site residues. The recently solved X-ray structure of the enzyme was inconsistent with this classification, and the involvement of a nucleophilic water molecule was proposed. Here, we substituted all conserved aspartate and glutamate residues by alanines and measured the residual enzymatic activities of the variants. Our results support the involvement of a nucleophilic water molecule that is activated by the Asp(210)/His(212) catalytic dyad. Activity is also strongly dependent on Asp(83) and Asp(85). Both may function in binding of the water molecule and/or oxyanion stabilization. The proposed mechanism implies a novel proteolytic catalytic site.
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Affiliation(s)
- R A Kramer
- Department of Enzymology and Protein Engineering, Institute of Biomembranes, Utrecht University, The Netherlands
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Snijder HJ, Kingma RL, Kalk KH, Dekker N, Egmond MR, Dijkstra BW. Structural investigations of calcium binding and its role in activity and activation of outer membrane phospholipase A from Escherichia coli. J Mol Biol 2001; 309:477-89. [PMID: 11371166 DOI: 10.1006/jmbi.2001.4675] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme that catalyses the hydrolysis of phospholipids. Enzymatic activity is regulated by reversible dimerisation and calcium-binding. We have investigated the role of calcium by X-ray crystallography. In monomeric OMPLA, one calcium ion binds between two external loops (L3L4 site) at 10 A from the active site. After dimerisation, a new calcium-binding site (catalytic site) is formed at the dimer interface in the active site of each molecule at 6 A from the L3L4 calcium site. The close spacing and the difference in calcium affinity of both sites suggests that the L3L4 site may function as a storage site for a calcium ion, which relocates to the catalytic site upon dimerisation. A sequence alignment demonstrates conservation of the catalytic calcium site but evolutionary variation of the L3L4 site. The residues in the dimer interface are conserved as well, suggesting that all outer membrane phospholipases require dimerisation and calcium in the catalytic site for activity. For this family of phospholipases, we have characterised a consensus sequence motif (YTQ-X(n)-G-X(2)-H-X-SNG) that contains conserved residues involved in dimerisation and catalysis.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, Nijenborgh 4 9747 AG, Groningen, The Netherlands.
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Bouma B, Westerman J, Dekker N, Gros P, Wirtz KW. Activation of phosphatidylinositol transfer protein alpha and beta isoforms from inclusion bodies. Biochim Biophys Acta 2001; 1546:216-25. [PMID: 11257524 DOI: 10.1016/s0167-4838(01)00142-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Fully active phosphatidylinositol transfer protein (PI-TP) isoforms alpha and beta have been obtained from Escherichia coli inclusion bodies. Folding and activation of PI-TPalpha was achieved in the presence of DiC7:0-phosphatidylcholine-Triton X-114 (PtdCho-TX114) mixed micelles. Replacement of DiC7:0-PtdCho with the natural ligands of PI-TPalpha, i.e. long-chain PtdCho and phosphatidylinositol, did not stimulate activation. Efficient activation of PI-TPalpha required a low temperature (4 degrees C), the presence of dithiothreitol, and was achieved at a relatively high protein concentration (i.e. up to 500 microg ml(-1)). The inclusion bodies yielded 10 mg homogeneous PI-TPalpha per liter of E. coli culture. Conditions for full activation of PI-TPbeta were similar to those for PI-TPalpha except that long-chain PtdCho-TX114 mixed micelles and a very low protein concentration (i.e. 10 microg ml(-1)) were required. In contrast to PI-TPalpha, PI-TPbeta lost its lipid transfer activity within a few days. This inactivation could be prevented by addition of beta-alanine. In summary, despite 94% sequence similarity, PI-TPalpha and PI-TPbeta display a striking difference both in their preference for the PtdCho acyl chain length required for activation, and in their conformational stability after folding.
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Affiliation(s)
- B Bouma
- Department of Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands.
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Dekker N, Cox RC, Kramer RA, Egmond MR. Substrate specificity of the integral membrane protease OmpT determined by spatially addressed peptide libraries. Biochemistry 2001; 40:1694-701. [PMID: 11327829 DOI: 10.1021/bi0014195] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Escherichia coli outer membrane protease T (OmpT) is an endopeptidase that specifically cleaves between two consecutive basic residues. In this study we have investigated the substrate specificity of OmpT using spatially addressed SPOT peptide libraries. The peptide acetyl-Dap(dnp)-Ala-Arg/Arg-Ala-Lys(Abz)-Gly was synthesized directly onto cellulose membrane. The peptide contained the aminobenzoyl (Abz) fluorophore, which was internally quenched by the dinitrophenyl (dnp) moiety. Treatment of the SPOT membrane with the small, water-soluble protease trypsin resulted in highly fluorescent peptide SPOTs. However, no peptide cleavage was observed after incubation with detergent-solubilized OmpT, a macromolecular complex with an estimated molecular mass of 180 kDa. This problem could be solved by the introduction of a long, polar polyoxyethylene glycol linker between the membrane support and the peptide. Peptide libraries for the P(2), P(1), P(1)', and P(2)' positions in the substrate were screened with OmpT, and peptides of positive SPOTs were resynthesized and subjected to kinetic measurements in solution. The best substrate Abz-Ala-Lys-Lys-Ala-Dap(dnp)-Gly had a turnover number k(cat) of 40 s(-)(1), which is 12-fold higher than the starting substrate. Peptides containing an acidic residue at P(2) or P(2)' were not substrates for OmpT, suggesting that long-range electrostatic interactions are important for the formation of the enzyme-substrate complex. OmpT was highly selective toward L-amino acids at P(1) but was less so at P(1)' where a peptide with D-Arg at P(1)' was a competitive inhibitor (K(i) of 19 microM). An affinity chromatography resin based on these findings was developed, which allowed for the one-step purification of OmpT from a bacterial lysate. The implications of the determined consensus substrate sequence (Arg/Lys)/(Arg/Lys)-Ala for the proposed biological function of OmpT in defense against antimicrobial peptides are discussed.
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Affiliation(s)
- N Dekker
- Department of Enzymology and Protein Engineering, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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Snijder HJ, van Eerde JH, Kingma RL, Ubarretxena I, Kalk KH, Verheij HM, Egmond MR, Dekker N, Dijkstra BW. Structure and Regulation of Outer Membrane Phospholipase A. Acta Crystallogr A 2000. [DOI: 10.1107/s0108767300022431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Kingma RL, Fragiathaki M, Snijder HJ, Dijkstra BW, Verheij HM, Dekker N, Egmond MR. Unusual catalytic triad of Escherichia coli outer membrane phospholipase A. Biochemistry 2000; 39:10017-22. [PMID: 10955989 DOI: 10.1021/bi000786d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Escherichia coli outer membrane phospholipase A (OMPLA) is an integral membrane enzyme. OMPLA is active as a homodimer and requires calcium as a cofactor. The crystal structures of the monomeric and the inhibited dimeric enzymes were recently determined [Snijder, H. J., et al. (1999) Nature 401, 717-721] and revealed that OMPLA monomers are folded into a 12-stranded antiparallel beta-barrel. The active site consists of previously identified essential residues Ser144 and His142 in an arrangement resembling the corresponding residues of a serine hydrolase catalytic triad. However, instead of an Asp or Glu that normally is present in the triad of serine hydrolases, a neutral asparagine (Asn156) was found in OMPLA. In this paper, the importance of the catalytic Asn156 is addressed by site-directed mutagenesis studies. All variants were purified at a 30 mg scale, and were shown to be properly folded using SDS-PAGE and circular dichroism spectroscopy. Using chemical cross-linking, it was shown that all variants were not affected in their calcium-dependent dimerization properties. The Asn156Asp variant exhibited a 2-fold lower activity than wild-type OMPLA at neutral pH. Interestingly, the activity of the variant is 1 order of magnitude higher than that of the wild type at pH >10. Modest residual activities (5 and 2.5%, respectively) were obtained for the Asn156Ala and Asn156Gln mutants, showing that the active site of OMPLA is more tolerant toward replacements of this third residue of the catalytic triad than other serine hydrolases, and that the serine and histidine residues are minimally required for catalysis. In the X-ray structure of dimeric OMPLA, the cofactor calcium is coordinating the putative oxyanion via two water molecules. We propose that this may lessen the importance for the asparagine in the catalytic triad of OMPLA.
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Affiliation(s)
- R L Kingma
- Department of Enzymology and Protein Engineering, Center for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, The Netherlands
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Jansen C, Wiese A, Reubsaet L, Dekker N, de Cock H, Seydel U, Tommassen J. Biochemical and biophysical characterization of in vitro folded outer membrane porin PorA of Neisseria meningitidis. Biochim Biophys Acta 2000; 1464:284-98. [PMID: 10727615 DOI: 10.1016/s0005-2736(00)00155-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Two subtypes of the outer membrane porin PorA of Neisseria meningitidis, P1.6 and P1.7,16, were folded in vitro after overexpression in, and isolation from Escherichia coli. The PorA porins could be folded efficiently by quick dilution in an appropriate buffer containing the detergent n-dodecyl-N, N-dimethyl-1-ammonio-3-propanesulphonate. Although the two PorA porins are highly homologous, they required different acidities for optimal folding, that is, a pH above the pI was needed for efficient folding. Furthermore, whereas trimers of PorA P1.7,16 were almost completely stable in 2% sodium dodecyl sulphate (SDS), those of P1.6 dissociated in the presence of SDS. The higher electrophoretic mobility of the in vitro folded porins could be explained by the stable association of the RmpM protein to the porins in vivo. This association of RmpM contributes to the stability of the porins. The P1.6 pores were moderately cation-selective and displayed a single-channel conductance of 2.8 nS in 1 M KCl. The PorA P1.6 pores, but not the PorA P1.7,16 pores, showed an unusual non-linear dependence of the single-channel conductance on the salt concentration of the subphase. We hypothesize that a cluster of three negatively charged residues in L5 of P1.6 is responsible for the higher conductance at low salt concentrations.
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Affiliation(s)
- C Jansen
- Department of Molecular Microbiology and Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, Netherlands
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41
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Abstract
Escherichia coli outer membrane protease OmpT has been characterised as a serine protease based on its inhibitor profile, but serine protease consensus sequences are absent. By site-directed mutagenesis we substituted all conserved serines and histidines. Substitution of His(101) and His(212) by Ala, Asn or Gln resulted in variant enzymes with 0.01 and 9-20% residual enzymatic activity towards a fluorogenic pentapeptide substrate, respectively. The mutations S140A and S201A did not decrease activity, while variants S40A and S99A yielded 0.5 and 0.2% residual activities, respectively. When measured with a dipeptide substrate the variant S40A demonstrated full activity, whereas variant S99A displayed at least 500-fold reduced activity. We conclude that Ser(99) and His(212) are essential active site residues. We propose that OmpT is a novel serine protease with Ser(99) as the active site nucleophile and His(212) as general base.
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Affiliation(s)
- R A Kramer
- Department of Enzymology, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
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Kramer RA, Zandwijken D, Egmond MR, Dekker N. In vitro folding, purification and characterization of Escherichia coli outer membrane protease ompT. Eur J Biochem 2000; 267:885-93. [PMID: 10651827 DOI: 10.1046/j.1432-1327.2000.01073.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OmpT is a protease present in the outer membrane of Escherichia coli. The enzyme was overexpressed without its signal sequence in E. coli using a T7 system, resulting in the accumulation of OmpT as inclusion bodies. After solubilization of the inclusion bodies in urea, the protein could be folded in vitro by dilution in the presence of detergent n-dodecyl-N, N-dimethyl-1-ammonio-3-propanesulphonate. The addition of lipopolysaccharide to the protein was essential to obtain active enzyme. The correctly folded protein was purified to homogeneity by ion exchange chromatography with a 57% overall yield. Autoproteolysis between Lys217-Arg218 was a major problem during purification, but degradation could be abolished by introducing the mutations G216K and K217G. A novel fluorimetric assay using the internally quenched substrate Abz-Ala-Arg-Arg-Ala-Tyr(NO2)-NH2 (where Abz is o-aminobenzoyl and Tyr(NO2) is 3-nitrotyrosine) enabled the determination of the kinetic parameters. The wild-type enzyme has an affinity Km of 0.4 microM for the substrate and a turnover number kcat of 40 s-1. The Km and kcat for the double variant were 1.1 microM and 1.6 s-1, respectively. The pH profiles of the wild type and variant were identical, showing optimal activity at pH 6.5 and pKa values of 5.6 and 7.5, respectively. Circular dichroism spectra of both enzymes indicated a high content of beta-strand conformation, and on that basis a beta-barrel topology model is proposed.
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Affiliation(s)
- R A Kramer
- Department of Enzymology and Protein Engineering, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, The Netherlands
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Abstract
Outer-membrane phospholipase A (OMPLA) is one of the few enzymes present in the outer membrane of Gram-negative bacteria. The enzymatic activity of OMPLA is strictly regulated to prevent uncontrolled breakdown of the surrounding phospholipids. The activity of OMPLA can be induced by membrane perturbation and concurs with dimerization of the enzyme. The recently elucidated crystal structures of the inactive, monomeric and an inhibited dimeric form of the enzyme provide detailed structural insight into the functional properties of the enzyme. OMPLA is a serine hydrolase with a unique Asn-156-His-142-Ser-144 catalytic triad. Only in the dimeric state, complete substrate binding pockets and functional oxyanion holes are formed. A model is proposed for the activation of OMPLA in which membrane perturbation causes the formation of non-bilayer structures, resulting in the presentation of phospholipids to the active site of OMPLA and leading to the formation of the active dimeric species. Possible roles for OMPLA in maintaining the cell envelope integrity and in pathogenicity are discussed.
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Affiliation(s)
- N Dekker
- Department of Enzymology and Protein Engineering, Center for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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Snijder HJ, Ubarretxena-Belandia I, Blaauw M, Kalk KH, Verheij HM, Egmond MR, Dekker N, Dijkstra BW. Structural evidence for dimerization-regulated activation of an integral membrane phospholipase. Nature 1999; 401:717-21. [PMID: 10537112 DOI: 10.1038/44890] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Dimerization is a biological regulatory mechanism employed by both soluble and membrane proteins. However, there are few structural data on the factors that govern dimerization of membrane proteins. Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme which participates in secretion of colicins in Escherichia coli. In Campilobacter and Helicobacter pylori strains, OMPLA is implied in virulence. Its activity is regulated by reversible dimerization. Here we report X-ray structures of monomeric and dimeric OMPLA from E. coli. Dimer interactions occur almost exclusively in the apolar membrane-embedded parts, with two hydrogen bonds within the hydrophobic membrane area being key interactions. Dimerization results in functional oxyanion holes and substrate-binding pockets, which are absent in monomeric OMPLA. These results provide a detailed view of activation by dimerization of a membrane protein.
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Affiliation(s)
- H J Snijder
- Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, The Netherlands
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Ubarretxena-Belandia I, Hozeman L, van der Brink-van der Laan E, Pap EH, Egmond MR, Verheij HM, Dekker N. Outer membrane phospholipase A is dimeric in phospholipid bilayers: a cross-linking and fluorescence resonance energy transfer study. Biochemistry 1999; 38:7398-405. [PMID: 10353852 DOI: 10.1021/bi983077x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the cell, the activity of outer membrane phospholipase A (OMPLA) is strictly regulated to prevent uncontrolled breakdown of the membrane lipids. Previously, it has been shown that the enzymatic activity is modulated by reversible dimerization. The current studies were carried out to define the oligomeric state of OMPLA in a membrane and to investigate the activation process. Three single-cysteine variant proteins H26C, H234C, and S144C were produced and purified to homogeneity. Using maleimido-based homo-bifunctional cross-linking reagents, H26C could be efficiently cross-linked as assessed by SDS-PAGE, whereas S144C and H234C could not be cross-linked. These data suggest that residue 26 is located close to the dimer symmetry axis. H26C was specifically labeled with 5-({[(2-iodoacetyl)amino]ethyl}amino)naphthalene-1-sulfonic acid and N,N'-dimethyl-N-(iodoacetyl)-N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)ethylenediamine as the fluorescent energy donor and acceptor, respectively, and dimerization was investigated using fluorescence resonance energy transfer (FRET). Quenching of the donor in the presence of the acceptor demonstrated the dimeric nature of OMPLA, in agreement with cross-linking data. The observed FRET effect was dependent on the cofactor calcium, and the presence of substrate, indicating the specificity of the dimerization process. The labeled protein was reconstituted in phospholipid vesicles. In bilayers, OMPLA exhibited low activity and was dimeric as assessed by FRET. Addition of detergent resulted in a 70-fold increase in activity, while the protein remained dimeric. The results are discussed in terms of the activation of dimeric OMPLA due to changes in the physical state of the bilayer which occur upon perturbation of the membrane integrity.
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Affiliation(s)
- I Ubarretxena-Belandia
- Department of Enzymology and Protein Engineering, Center for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, The Netherlands
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Abstract
Bacteriocin release protein is known to activate outer membrane phospholipase A (OMPLA), which results in the release of colicin from Escherichia coli. In vivo chemical cross-linking experiments revealed that the activation coincides with dimerization of OMPLA. Permeabilization of the cell envelope and dimerization were characterized by a lag time of 2 h.
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Affiliation(s)
- N Dekker
- Department of Enzymology and Protein Engineering, Center for Biomembranes and Lipid Enzymology, Utrecht University, 3584 CH Utrecht, The Netherlands.
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Ubarretxena-Belandia I, Cox RC, Dijkman R, Egmond MR, Verheij HM, Dekker N. Half-of-the-sites reactivity of outer-membrane phospholipase A against an active-site-directed inhibitor. Eur J Biochem 1999; 260:794-800. [PMID: 10103009 DOI: 10.1046/j.1432-1327.1999.00221.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The reaction of a novel active-site-directed phospholipase A1 inhibitor with the outer-membrane phospholipase A (OMPLA) was investigated. The inhibitor 1-p-nitrophenyl-octylphosphonate-2-tridecylcarbamoyl-3-et hanesulfonyl -amino-3-deoxy-sn-glycerol irreversibly inactivated OMPLA. The inhibition reaction did not require the cofactor calcium or an unprotonated active-site His142. The inhibition of the enzyme solubilized in hexadecylphosphocholine micelles was characterized by a rapid (t1/2 = 20 min) and complete loss of enzymatic activity, concurrent with the covalent modification of 50% of the active-site serines, as judged from the amount of p-nitrophenolate (PNP) released. Modification of the remaining 50% occurred at a much lower rate, indicative of half-of-the-sites reactivity against the inhibitor of this dimeric enzyme. Inhibition of monomeric OMPLA solubilized in hexadecyl-N,N-dimethyl-1-ammonio-3-propanesulfonate resulted in an equimolar monophasic release of PNP, concurrent with the loss of enzymatic activity (t1/2 = 14 min). The half-of-the-sites reactivity is discussed in view of the dimeric nature of this enzyme.
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Abstract
The enzymatic activity of the outer membrane phospholipase A (OMPLA), an integral membrane protein of Escherichia coli, is regulated by dimerization for which the cofactor Ca2+ is required. In this study, the interaction of Ca2+ with OMPLA was characterized, with an emphasis on the role of the cofactor in the activation process and dimerization. Kinetic experiments were done in which the enzyme was solubilized in mixed micelles of substrate and different detergents. It appeared that the affinity of OMPLA for Ca2+ was high (12 microM) if alkylphosphocholines were used as detergent, moderate (62 microM) if sulfobetaines were used, and very low (24 mM) if alkylpolyoxyethylene glycols were used. These results show that there is a strong modulation of the calcium binding properties of OMPLA by the lipid environment. In the presence of hexadecylphosphocholine micelles, the affinity of OMPLA for Ca2+ was determined by three direct binding techniques. Using gel filtration, it appeared that OMPLA has one high-affinity site (Kd approximately 36 microM) and a second site with moderate affinity (Kd approximately 358 microM). Sulfonylated-OMPLA, in which the active site serine had been covalently modified with hexadecanesulfonylfluoride, was used as a mimic for the acyl-enzyme intermediate. In gel filtration experiments, this sulfonylated-OMPLA displayed binding of two Ca2+ per enzyme monomer both with similar high affinity (Kd approximately 48 microM), indicative of a strong synergistic effect of active site occupation and the affinity of the second Ca2+ binding site. Isothermal titration calorimetric measurements confirmed only the presence of a high-affinity Ca2+ binding site, whereas in fluorescence experiments only the binding of the second Ca2+ could be observed. Chemical cross-linking was applied to investigate which of the two Ca2+ sites is involved in dimerization. OMPLA was monomeric in the absence of Ca2+, whereas already at low Ca2+ concentrations the enzyme was converted to its dimeric form. Therefore, we suggest that the first Ca2+ plays a role in the stabilization of the dimeric state of the enzyme. The role of the second Ca2+ and the observed synergy between active site occupancy and Ca2+ affinity are discussed.
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Affiliation(s)
- I Ubarretxena-Belandia
- Department of Enzymology and Protein Engineering, Center for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, The Netherlands
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Brok RG, Boots AP, Dekker N, Verheij HM, Tommassen J. Sequence comparison of outer membrane phospholipases A: implications for structure and for the catalytic mechanism. Res Microbiol 1998; 149:703-10. [PMID: 9921577 DOI: 10.1016/s0923-2508(99)80017-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In this study, the nucleotide sequence of the Enterobacter agglomerans pldA gene encoding outer membrane phospholipase A (OMPLA; EC 3.1.1.32) was determined. Five other OMPLA amino acid sequences have previously been described, and screening of data bases of whole genome sequencing projects revealed the presence of proteins with homology to OMPLA in Helicobacter pylori, Campylobacter jejuni, Yersinia pestis, Neisseria menigitidis and Neisseria gonorrhoeae. Comparison of these eleven OMPLA amino acid sequences revealed that 30 amino acid residues are completely conserved. Implications of the sequence comparison for the catalytic mechanism of OMPLA are discussed. The presence of proteins homologous to OMPLA even in non-enterobacterial Gram-negative bacteria indicates an important physiological role of this enzyme.
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Affiliation(s)
- R G Brok
- Department of Molecular Cell Biology, Utrecht University, The Netherlands
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Boekema EJ, Stuart M, Koning RI, Keegstra W, Brisson A, Verheij HM, Dekker N. A 7.4-A projection structure of outer membrane phospholipase A from Escherichia coli by electron crystallography. J Struct Biol 1998; 123:67-71. [PMID: 9774546 DOI: 10.1006/jsbi.1998.4013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Outer membrane phospholipase A (OMPLA) is one of the few enzymes present in the outer membrane of Escherichia coli. Two-dimensional crystals of OMPLA were grown by reconstitution of purified protein into lipid bilayers via detergent dialysis and were studied by electron crystallography. A 7.4-A projection map reveals OMPLA molecules exhibiting an oval-shaped domain of 30 x 20 A resembling the beta-barrel structure characteristic of porins, which is associated with a 25-A elongated domain of lower density.
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Affiliation(s)
- E J Boekema
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, Groningen, NL-9747 AG, The Netherlands
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