22 results on '"Van Hoof D"'
Search Results
2. Plangebied Akkersplein te Heerenveen Gemeente Heerenveen Archeologisch vooronderzoek: een bureauen inventariserend veldonderzoek
- Author
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drs. B.I. van Hoof & D. van den Berg and RAAP Archeologisch Adviesbureau
- Subjects
Archaeology ,booronderzoek ,archeologie - Published
- 2013
3. Plangebied Akkersplein te Heerenveen : gemeente Heerenveen : archeologisch vooronderzoek: een bureau- en inventariserend veldonderzoek
- Author
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Hoof, B.I. van, Berg, D. van den, [auteurs: B.I. van Hoof & D. van den Berg], and Weesp : RAAP Archeologisch Adviesbureau
- Subjects
Archaeology ,Heerenveen ,archeologie - Abstract
Met lit. opg
- Published
- 2011
4. Plangebied compressorstation Scheemda, gemeente Scheemda : archeologisch vooronderzoek: een inventariserend veldonderzoek
- Author
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Hoof, B.I. van, Berg, D. van den, Zwet, E.J.M. van der, Perger, T.M., B.I. van Hoof, D. van den Berg, E.J.M. van der Zwet, T.M. Perger., and RAAP Archeologisch Adviesbureau
- Subjects
prospectie ,Archaeology ,archeologie - Abstract
Lit.opg.
- Published
- 2008
5. FosfoProteómica cuantitativa en células madre embrionarias humanas
- Author
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Muñoz, J., Pinkse, M.W., Van Hoof, D., Mohammed, S., Mummery, C.L., Heck, Albert, and Krijgsveld, J.
- Subjects
Sistemas biológicos ,Biotecnología ,Proteómica - Published
- 2008
6. Plangebied De Finne 2 te Ysbrechtum, gemeente Sneek : archeologisch vooronderzoek: een bureau- en inventariserend veldonderzoek
- Author
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Hoof, B.I. van, Berg, D. van den, [auteurs: B.I. van Hoof & D. van den Berg], RAAP Archeologisch Adviesbureau, and Weesp : RAAP Archeologisch Adviesbureau
- Subjects
prospectie ,Archaeology ,Ysbrechtum ,archeologie - Abstract
Met lit. opg
- Published
- 2008
7. Konkelswei 25 Oosterbierum : Gemeente Franekeradiel : archeologisch vooronderzoek: een bureau- en inventariserend veldonderzoek
- Author
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Hoof, B.I. van, Berg, D. van den, B.I. van Hoof & D. van den Berg, Amsterdam : RAAP Archeologisch Adviesbureau, and RAAP Archeologisch Adviesbureau
- Subjects
prospectie ,Archaeology ,Oosterbierum ,archeologie - Abstract
Met lit. opg
- Published
- 2007
8. An experimental correction for arginine-to-proline conversion artifacts in SILAC-based quantitative proteomics
- Author
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van Hoof, D., Pinkse, M.W.H., Ward-van Oostwaard, D., Mummery, C.L., Heck, A.J.R., Krijgsveld, J., Biomoleculaire Massaspectrometrie, Massaspectrometrie, Dep Scheikunde, and Dep Farmaceutische wetenschappen
- Subjects
Farmacie(FARM) - Published
- 2007
9. Embryonic stem cell proteomics
- Author
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van Hoof, D., Mummery, C.L., Heck, A.J.R., Krijgsveld, J., Biomoleculaire Massaspectrometrie, Massaspectrometrie, and Dep Scheikunde
- Subjects
Farmacie/Biofarmaceutische wetenschappen (FARM) ,Other medical specialities ,Geneeskunde (GENK) ,Farmacie(FARM) ,Geneeskunde(GENK) ,General [Econometric and Statistical Methods] ,Algemeen onderzoek - Published
- 2006
10. Proteomic Analysis of Stem Cell Differentiation and Early Development
- Author
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van Hoof, D., primary, Krijgsveld, J., additional, and Mummery, C., additional
- Published
- 2012
- Full Text
- View/download PDF
11. Phosphorylation of NEUROG3 Links Endocrine Differentiation to the Cell Cycle in Pancreatic Progenitors.
- Author
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Krentz NAJ, van Hoof D, Li Z, Watanabe A, Tang M, Nian C, German MS, and Lynn FC
- Subjects
- Animals, Basic Helix-Loop-Helix Transcription Factors genetics, Endocrine Cells metabolism, Gene Expression Regulation, Developmental physiology, Humans, Islets of Langerhans cytology, Mice, Nerve Tissue Proteins genetics, Phosphorylation physiology, Stem Cells metabolism, Basic Helix-Loop-Helix Transcription Factors metabolism, Cell Cycle physiology, Cell Differentiation physiology, Nerve Tissue Proteins metabolism, Pancreas cytology, Pancreas metabolism, Stem Cells cytology
- Abstract
During pancreatic development, proliferating pancreatic progenitors activate the proendocrine transcription factor neurogenin 3 (NEUROG3), exit the cell cycle, and differentiate into islet cells. The mechanisms that direct robust NEUROG3 expression within a subset of progenitor cells control the size of the endocrine population. Here we demonstrate that NEUROG3 is phosphorylated within the nucleus on serine 183, which catalyzes its hyperphosphorylation and proteosomal degradation. During progression through the progenitor cell cycle, NEUROG3 phosphorylation is driven by the actions of cyclin-dependent kinases 2 and 4/6 at G
1 /S cell-cycle checkpoint. Using models of mouse and human pancreas development, we show that lengthening of the G1 phase of the pancreatic progenitor cell cycle is essential for proper induction of NEUROG3 and initiation of endocrine cell differentiation. In sum, these studies demonstrate that progenitor cell-cycle G1 lengthening, through its actions on stabilization of NEUROG3, is an essential variable in normal endocrine cell genesis., (Copyright © 2017 Elsevier Inc. All rights reserved.)- Published
- 2017
- Full Text
- View/download PDF
12. PEGylated IL-10 Activates Kupffer Cells to Control Hypercholesterolemia.
- Author
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Chan IH, Van Hoof D, Abramova M, Bilardello M, Mar E, Jorgensen B, McCauley S, Bal H, Oft M, Van Vlasselaer P, and Mumm JB
- Subjects
- Adolescent, Adult, Aged, Aged, 80 and over, Animals, Cholesterol immunology, Female, Humans, Hypercholesterolemia blood, Hypercholesterolemia immunology, Immunologic Factors chemistry, Immunologic Factors pharmacology, Interleukin-10 chemistry, Interleukin-10 pharmacology, Kupffer Cells immunology, Male, Mice, Inbred C57BL, Middle Aged, Polyethylene Glycols chemistry, Polyethylene Glycols pharmacology, Polyethylene Glycols therapeutic use, Recombinant Proteins chemistry, Recombinant Proteins pharmacology, Recombinant Proteins therapeutic use, Young Adult, Cholesterol blood, Hypercholesterolemia drug therapy, Immunologic Factors therapeutic use, Interleukin-10 therapeutic use, Kupffer Cells drug effects, Phagocytosis drug effects
- Abstract
Interleukin-10 (IL-10) is a multifunctional cytokine that exerts potent context specific immunostimulatory and immunosuppressive effects. We have investigated the mechanism by which PEGylated rIL-10 regulates plasma cholesterol in mice and humans. In agreement with previous work on rIL-10, we report that PEGylated rIL-10 harnesses the myeloid immune system to control total plasma cholesterol levels. We have discovered that PEG-rMuIL-10's dramatic lowering of plasma cholesterol is dependent on phagocytotic cells. In particular, PEG-rHuIL-10 enhances cholesterol uptake by Kupffer cells. In addition, removal of phagocytotic cells dramatically increases plasma cholesterol levels, suggesting for the first time that immunological cells are implicitly involved in regulating total cholesterol levels. These data suggest that treatment with PEG-rIL-10 potentiates endogenous cholesterol regulating cell populations not currently targeted by standard of care therapeutics. Furthermore, we show that IL-10's increase of Kupffer cell cholesterol phagocytosis is concomitant with decreases in liver cholesterol and triglycerides. This leads to the reversal of early periportal liver fibrosis and facilitates the restoration of liver health. These data recommend PEG-rIL-10 for evaluation in the treatment of fatty liver disease and preventing its progression to non-alcoholic steatohepatitis. In direct confirmation of our in vivo findings in the treatment of hypercholesterolemic mice with PEG-rMuIL-10, we report that treatment of hypercholesterolemic cancer patients with PEG-rHuIL-10 lowers total plasma cholesterol by up to 50%. Taken together these data suggest that PEG-rIL-10's cholesterol regulating biology is consistent between mice and humans.
- Published
- 2016
- Full Text
- View/download PDF
13. Differentiation of human embryonic stem cells into pancreatic endoderm in patterned size-controlled clusters.
- Author
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Van Hoof D, Mendelsohn AD, Seerke R, Desai TA, and German MS
- Subjects
- Cell Size, Embryonic Stem Cells metabolism, Endoderm metabolism, Gene Expression, Homeodomain Proteins genetics, Homeodomain Proteins metabolism, Humans, Insulin-Secreting Cells cytology, Insulin-Secreting Cells metabolism, Pancreas growth & development, Pancreas metabolism, Trans-Activators genetics, Trans-Activators metabolism, Cell Culture Techniques methods, Cell Differentiation, Embryonic Stem Cells cytology, Endoderm cytology, Pancreas cytology
- Abstract
Pancreatic β-cells function optimally when clustered in islet-like structures. However, nutrient and oxygen deprivation limits the viability of cells at the core of excessively large clusters. Hence, production of functional β-cells from human embryonic stem cells (hESCs) for patients with diabetes would benefit from the growth and differentiation of these cells in size-controlled aggregates. In this study, we controlled cluster size by seeding hESCs onto glass cover slips patterned by the covalent microcontact-printing of laminin in circular patches of 120 μm in diameter. These were used as substrates to grow and differentiate hESCs first into SOX17-positive/SOX7-negative definitive endoderm, after which many clusters released and formed uniformly sized three-dimensional clusters. Both released clusters and those that remained attached differentiated into HNF1β-positive primitive gut tube-like cells with high efficiency. Further differentiation yielded pancreatic endoderm-like cells that co-expressed PDX1 and NKX6.1. Controlling aggregate size allows efficient production of uniformly-clustered pancreatic endocrine precursors for in vivo engraftment or further in vitro maturation., (Copyright © 2011 Elsevier B.V. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
14. Derivation of insulin-producing cells from human embryonic stem cells.
- Author
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Van Hoof D, D'Amour KA, and German MS
- Subjects
- Cell Differentiation, Diabetes Mellitus etiology, Diabetes Mellitus therapy, Endoderm cytology, Humans, Insulin genetics, Insulin metabolism, Transcription Factors metabolism, Embryonic Stem Cells cytology, Insulin-Secreting Cells cytology
- Abstract
The potential of pluripotent human cells, such as human embryonic stem cells (hESCs) and induced pluripotent stem (iPS) cells, to differentiate into any adult cell type makes them ideally suited for the generation of various somatic cells and tissues in vitro. This remarkable differentiation capacity permits analyzing aspects of human embryonic development in the laboratory, as well as generating specialized adult human cells for screening drugs, and for replacing tissues damaged by injury or degenerative diseases, such as diabetes. Understanding and controlling the fundamental processes that drive the differentiation of specialized cells are the keys to the eventual application of this technology to patients. In this review, we discuss the different protocols developed that are aimed at deriving beta-cells from hESCs. Despite many differences, successful strategies share a general adherence to the normal differentiation pathway through definitive endoderm. Mimicking normal pancreagenesis offers the best strategy for producing glucose-responsive insulin-producing cells in vitro for people with diabetes.
- Published
- 2009
- Full Text
- View/download PDF
15. Phosphorylation dynamics during early differentiation of human embryonic stem cells.
- Author
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Van Hoof D, Muñoz J, Braam SR, Pinkse MW, Linding R, Heck AJ, Mummery CL, and Krijgsveld J
- Subjects
- Bone Morphogenetic Proteins pharmacology, CDC2 Protein Kinase metabolism, Cell Differentiation drug effects, Cell Differentiation physiology, Cyclin-Dependent Kinase 2 metabolism, Embryonic Stem Cells drug effects, HeLa Cells, Humans, Phosphoproteins drug effects, Phosphorylation drug effects, Phosphorylation physiology, Pluripotent Stem Cells drug effects, Proteome drug effects, SOXB1 Transcription Factors antagonists & inhibitors, SOXB1 Transcription Factors metabolism, Signal Transduction drug effects, Signal Transduction physiology, Embryonic Stem Cells metabolism, Phosphoproteins metabolism, Pluripotent Stem Cells metabolism, Proteome metabolism
- Abstract
Pluripotent stem cells self-renew indefinitely and possess characteristic protein-protein networks that remodel during differentiation. How this occurs is poorly understood. Using quantitative mass spectrometry, we analyzed the (phospho)proteome of human embryonic stem cells (hESCs) during differentiation induced by bone morphogenetic protein (BMP) and removal of hESC growth factors. Of 5222 proteins identified, 1399 were phosphorylated on 3067 residues. Approximately 50% of these phosphosites were regulated within 1 hr of differentiation induction, revealing a complex interplay of phosphorylation networks spanning different signaling pathways and kinase activities. Among the phosphorylated proteins was the pluripotency-associated protein SOX2, which was SUMOylated as a result of phosphorylation. Using the data to predict kinase-substrate relationships, we reconstructed the hESC kinome; CDK1/2 emerged as central in controlling self-renewal and lineage specification. The findings provide new insights into how hESCs exit the pluripotent state and present the hESC (phospho)proteome resource as a complement to existing pluripotency network databases.
- Published
- 2009
- Full Text
- View/download PDF
16. Feeder-free monolayer cultures of human embryonic stem cells express an epithelial plasma membrane protein profile.
- Author
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Van Hoof D, Braam SR, Dormeyer W, Ward-van Oostwaard D, Heck AJ, Krijgsveld J, and Mummery CL
- Subjects
- Antigens, Differentiation metabolism, Cell Adhesion, Cell Differentiation, Cells, Cultured, Coculture Techniques methods, Collagen metabolism, Drug Combinations, Embryonic Stem Cells metabolism, Epithelial Cells metabolism, Humans, Laminin metabolism, Mass Spectrometry, Microscopy, Fluorescence, Proteoglycans metabolism, Cell Membrane metabolism, Embryonic Stem Cells cytology, Epithelial Cells cytology, Membrane Proteins metabolism
- Abstract
Human embryonic stem cells (hESCs) are often cocultured on mitotically inactive fibroblast feeder cells to maintain their undifferentiated state. Under these growth conditions, hESCs form multilayered colonies of morphologically heterogeneous cells surrounded by flattened mesenchymal cells. In contrast, hESCs grown in feeder cell-conditioned medium on Matrigel instead tend to grow as monolayers with uniform morphology. Using mass spectrometry and immunofluorescence microscopy, we showed that hESCs under these conditions primarily express proteins belonging to epithelium-related cell-cell adhesion complexes, including adherens junctions, tight junctions, desmosomes, and gap junctions. This indicates that monolayers of hESCs cultured under feeder-free conditions retain a homogeneous epithelial phenotype similar to that of the upper central cell layer of colonies maintained on feeder cells. Notably, feeder-free hESCs also coexpressed vimentin, which is usually associated with mesenchyme, suggesting that these cells may have undergone epithelium-to-mesenchyme transitions, indicating differentiation. However, if grown on a "soft" substrate (Hydrogel), intracellular vimentin levels were substantially reduced. Moreover, when hESCs were transferred back to feeder cells, expression of vimentin was again absent from the epithelial cell population. These results imply that on tissue culture substrates, vimentin expression is most likely a stress-induced response, unrelated to differentiation. Disclosure of potential conflicts of interest is found at the end of this article.
- Published
- 2008
- Full Text
- View/download PDF
17. Proteomics and human embryonic stem cells.
- Author
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Van Hoof D, Heck AJ, Krijgsveld J, and Mummery CL
- Subjects
- Humans, Mass Spectrometry, Proteins analysis, Embryonic Stem Cells, Proteomics methods
- Abstract
The derivation of human embryonic stem cells (hESCs) brought cell therapy-based regenerative medicine significantly closer to clinical application. However, expansion of undifferentiated cells and their directed differentiation in vitro have proven difficult to control. This is mainly because of a lack of knowledge of the intracellular signaling events that direct these complex processes. Additionally, extracellular factors, either secreted by feeder cells that support self-renewal and maintain pluripotency or present in serum supplementing proprietary culture media, that influence hESC behavior are largely unknown. Xeno-free media that effectively support long-term hESC self-renewal and differentiation to specific types of specialized cells are only slowly becoming available. Microarray-based transcriptome analyses have produced valuable gene expression profiles of hESCs and indicated changes in transcription that occur during differentiation. However, proteins are the actual effectors of these events and changes in their levels do not always match changes in their corresponding mRNA. Furthermore, information on posttranslational modifications that influence the activity of pivotal proteins is still largely missing. Over the years, mass spectrometry has experienced major breakthroughs in high-throughput identification of proteins and posttranslational modifications in cells under different conditions. Mass spectrometry-based proteomic techniques are being applied with increasing frequency to analyze hESCs, as well as media conditioned by feeder cells, and have generated proteome profiles that not only support, but also complement, existing microarray data. In this review, the various proteomic studies on hESCs and feeder cells are discussed. In a meta-analysis, comparison of published data sets distinguished 32 intracellular proteins and 16 plasma membrane proteins that are present in multiple hESC lines but not in differentiated cells, which were therefore likely to include proteins important for hESCs. In addition, 13 and 24 proteins, respectively, were commonly found in different feeder cell lines of mouse and human origin, some of which may be extracellular signaling molecules that play a key role in the undifferentiated propagation of hESCs. These findings underscore the power of mass spectrometry-based techniques to identify novel proteins associated with hESCs by studying these cells in an unbiased, discovery-oriented manner on a proteome-wide scale.
- Published
- 2008
- Full Text
- View/download PDF
18. Concise review: trends in stem cell proteomics.
- Author
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Baharvand H, Fathi A, van Hoof D, and Salekdeh GH
- Subjects
- Bodily Secretions chemistry, Bodily Secretions metabolism, Cells, Cultured, Electrophoresis, Gel, Two-Dimensional, Gene Expression Profiling, Humans, Mass Spectrometry, Membrane Proteins analysis, Models, Biological, Protein Array Analysis, Protein Processing, Post-Translational, Proteome metabolism, Transplants, Proteome analysis, Proteomics trends, Stem Cells metabolism
- Abstract
Gene expression analyses of stem cells (SCs) will help to uncover or further define signaling pathways and molecular mechanisms involved in the maintenance of self-renewal, pluripotency, and/or multipotency. In recent years, proteomic approaches have produced a wealth of data identifying proteins and mechanisms involved in SC proliferation and differentiation. Although many proteomics techniques have been developed and improved in peptide and protein separation, as well as mass spectrometry, several important issues, including sample heterogeneity, post-translational modifications, protein-protein interaction, and high-throughput quantification of hydrophobic and low-abundance proteins, still remain to be addressed and require further technical optimization. This review summarizes the methodologies used and the information gathered with proteome analyses of SCs, and it discusses biological and technical challenges for proteomic study of SCs. Disclosure of potential conflicts of interest is found at the end of this article.
- Published
- 2007
- Full Text
- View/download PDF
19. A quest for human and mouse embryonic stem cell-specific proteins.
- Author
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Van Hoof D, Passier R, Ward-Van Oostwaard D, Pinkse MW, Heck AJ, Mummery CL, and Krijgsveld J
- Subjects
- Animals, Biomarkers, Blotting, Western, Cell Differentiation, Cell Line, Cells, Cultured, Flow Cytometry, Humans, Mice, Microscopy, Fluorescence, Models, Biological, Embryo, Mammalian cytology, Proteomics, Stem Cells metabolism
- Abstract
Embryonic stem cells (ESCs) are of immense interest as they can proliferate indefinitely in vitro and give rise to any adult cell type, serving as a potentially unlimited source for tissue replacement in regenerative medicine. Extensive analyses of numerous human and mouse ESC lines have shown generic similarities and differences at both the transcriptional and functional level. However, comprehensive proteome analyses are missing or are restricted to mouse ESCs. Here we have used an extensive proteomic approach to search for ESC-specific proteins by analyzing the differential protein expression profiles of human and mouse ESCs and their differentiated derivatives. The data sets comprise 1,775 non-redundant proteins identified in human ESCs, 1,532 in differentiated human ESCs, 1,871 in mouse ESCs, and 1,552 in differentiated mouse ESCs with a false positive rate of <0.2%. Comparison of the data sets distinguished 191 proteins exclusively identified in both human and mouse ESCs but not in their differentiated derivatives. Besides well known ESC benchmarks, this subset included many uncharacterized proteins, some of which may be novel ESC-specific markers. To complement the mass spectrometric approach, differential expression of a selection of these proteins was confirmed by Western blotting, immunofluorescence confocal microscopy, and fluorescence-activated cell sorting. Additionally two other independently isolated and cultured human ESC lines as well as their differentiated derivatives were monitored for differential expression of selected proteins. Some of these proteins were identified exclusively in ESCs of all three human lines and may thus serve as generic ESC markers. Our wide scale proteomic approach enabled us to screen thousands of proteins rapidly and select putative ESC-associated proteins for further analysis. Validation by three independent conventional protein analysis techniques shows that our methodology is robust, provides an excellent tool to characterize ESCs at the protein level, and may disclose novel ESC-specific benchmarks.
- Published
- 2006
- Full Text
- View/download PDF
20. Intracellular fate of LDL receptor family members depends on the cooperation between their ligand-binding and EGF domains.
- Author
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Van Hoof D, Rodenburg KW, and Van der Horst DJ
- Subjects
- Animals, Asparagine chemistry, Blotting, Western, CHO Cells, Cell Membrane metabolism, Cricetinae, DNA, Complementary metabolism, Endocytosis, ErbB Receptors metabolism, Histidine chemistry, Hydrogen-Ion Concentration, Ligands, Lipoproteins chemistry, Locusta migratoria, Microscopy, Fluorescence, Models, Chemical, Models, Molecular, Mutation, Phenotype, Protein Structure, Tertiary, Receptors, LDL genetics, Receptors, LDL metabolism, Receptors, Lipoprotein chemistry, Time Factors, Transfection, Transferrin chemistry, Receptors, LDL chemistry
- Abstract
The insect low-density lipoprotein (LDL) receptor (LDLR) homologue LpR mediates endocytosis of an insect lipoprotein (lipophorin) that is structurally related to LDL. Despite these similarities, lipophorin and LDL follow distinct intracellular routes upon endocytosis by their receptors. Whereas LDL is degraded in lysosomes, lipophorin is recycled in a transferrin-like manner. We constructed several hybrid receptors composed of Locusta migratoria LpR and human LDLR regions to identify the domains implicated in LpR-mediated ligand recycling. Additionally, the triadic His562 residue of LDLR, which is putatively involved in ligand uncoupling, was mutated to Asn, corresponding to Asn643 in LpR, to analyse the role of the His triad in receptor functioning. The familial hypercholesterolaemia (FH) class 5 mutants LDLR(H562Y) and LDLR(H190Y) were also analysed in vitro. Fluorescence microscopic investigation and quantification suggest that LpR-mediated ligand recycling involves cooperation between the ligand-binding domain and epidermal growth factor (EGF) domain of LpR, whereas its cytosolic tail does not harbour motifs that affect this process. LDLR residue His562 appears to be essential for LDLR recycling after ligand endocytosis but not for constitutive receptor recycling. Like LDLR(H562N), LDLR(H562Y) did not recycle bound ligand; moreover, the intracellular distribution of both mutant receptors after ligand incubation coincides with that of a lysosomal marker. The LDLR mutant characterization in vitro suggests that LDLR FH class 5 mutations might be divided into two subclasses.
- Published
- 2005
- Full Text
- View/download PDF
21. Lipophorin receptor-mediated lipoprotein endocytosis in insect fat body cells.
- Author
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Van Hoof D, Rodenburg KW, and van der Horst DJ
- Subjects
- Animals, Carrier Proteins metabolism, Female, Fluorescent Antibody Technique, Humans, Larva metabolism, Ligands, Lipoproteins, HDL metabolism, Male, Molecular Chaperones metabolism, Endocytosis, Fat Body cytology, Fat Body metabolism, Grasshoppers metabolism, Lipoproteins metabolism, Receptors, Cytoplasmic and Nuclear metabolism
- Abstract
High-density lipophorin (HDLp) in the circulation of insects is able to selectively deliver lipids to target tissues in a nonendocytic manner. In Locusta migratoria, a member of the LDL receptor family has been identified and shown to mediate endocytosis of HDLp in mammalian cells transfected with the cDNA of this receptor. This insect lipophorin receptor (iLR) is temporally expressed in fat body tissue of young adult as well as larval locusts, as shown by Western blot analysis. Fluorescence microscopy revealed that fat body cells internalize fluorescently labeled HDLp and human receptor-associated protein only when iLR is expressed. Expression of iLR is down-regulated on Day 4 after an ecdysis. Consequently, HDLp is no longer internalized. By starving adult locusts immediately after ecdysis, we were able to prolong iLR expression. In addition, expression of the receptor was induced by starving adults after down-regulation of iLR. These results suggest that iLR mediates endocytosis of HDLp in fat body cells, and that expression of iLR is regulated by the demand of fat body tissue for lipids.
- Published
- 2003
- Full Text
- View/download PDF
22. Insect lipoprotein follows a transferrin-like recycling pathway that is mediated by the insect LDL receptor homologue.
- Author
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Van Hoof D, Rodenburg KW, and Van der Horst DJ
- Subjects
- Animals, CHO Cells, Cell Compartmentation physiology, Cricetinae, Endosomes metabolism, Fluorescent Antibody Technique, Humans, Ionophores pharmacology, LDL-Receptor Related Protein-Associated Protein metabolism, Monensin pharmacology, Organelles metabolism, Protein Transport physiology, Transferrin metabolism, Transport Vesicles metabolism, Carrier Proteins metabolism, Endocytosis physiology, Insecta metabolism, Lipoproteins metabolism, Lipoproteins, LDL metabolism, Mammals metabolism, Receptors, Cytoplasmic and Nuclear metabolism, Receptors, LDL metabolism
- Abstract
The lipoprotein of insects, high-density lipophorin (HDLp), is homologous to that of mammalian low-density lipoprotein (LDL) with respect to its apolipoprotein structure. Moreover, an endocytic receptor for HDLp has been identified (insect lipophorin receptor, iLR) that is homologus to the LDL receptor. We transfected LDL-receptor-expressing CHO cells with iLR cDNA to study the endocytic uptake and intracellular pathways of LDL and HDLp simultaneously. Our studies provide evidence that these mammalian and insect lipoproteins follow distinct intracellular routes after receptor-mediated endocytosis. Multicolour imaging and immunofluorescence was used to visualize the intracellular trafficking of fluorescently labeled ligands in these cells. Upon internalization, which can be completely inhibited by human receptor-associated protein (RAP), mammalian and insect lipoproteins share endocytic vesicles. Subsequently, however, HDLp evacuates the LDL-containing endosomes. In contrast to LDL, which is completely degraded in lysosomes after dissociating from its receptor, both HDLp and iLR converge in a nonlysosomal juxtanuclear compartment. Colocalization studies with transferrin identified this organelle as the endocytic recycling compartment via which iron-depleted transferrin exits the cell. Fluorescently labeled RAP is also transported to this recycling organelle upon receptor-mediated endocytosis by iLR. Internalized HDLp eventually exits the cell via the recycling compartment, a process that can be blocked by monensin, and is re-secreted with a t(1/2) of approximately 13 minutes. From these observations, we conclude that HDLp is the first non-exchangeable apolipoprotein-containing lipoprotein that follows a transferrin-like recycling pathway despite the similarities between mammalian and insect lipoproteins and their receptors.
- Published
- 2002
- Full Text
- View/download PDF
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