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Affiliation(s)
- John E Kratz
- California Digital Library , 415 20th Street, 4th Floor Oakland, CA 94612-2901, USA
| | - Carly Strasser
- Gordon and Betty Moore Foundation , 1661 Page Mill Road, Palo Alto, CA 94304, USA
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Schurek EM, Völker LA, Tax J, Lamkemeyer T, Rinschen MM, Ungrue D, Kratz JE, Sirianant L, Kunzelmann K, Chalfie M, Schermer B, Benzing T, Höhne M. A disease-causing mutation illuminates the protein membrane topology of the kidney-expressed prohibitin homology (PHB) domain protein podocin. J Biol Chem 2014; 289:11262-11271. [PMID: 24596097 DOI: 10.1074/jbc.m113.521773] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mutations in the NPHS2 gene are a major cause of steroid-resistant nephrotic syndrome, a severe human kidney disorder. The NPHS2 gene product podocin is a key component of the slit diaphragm cell junction at the kidney filtration barrier and part of a multiprotein-lipid supercomplex. A similar complex with the podocin ortholog MEC-2 is required for touch sensation in Caenorhabditis elegans. Although podocin and MEC-2 are membrane-associated proteins with a predicted hairpin-like structure and amino and carboxyl termini facing the cytoplasm, this membrane topology has not been convincingly confirmed. One particular mutation that causes kidney disease in humans (podocin(P118L)) has also been identified in C. elegans in genetic screens for touch insensitivity (MEC-2(P134S)). Here we show that both mutant proteins, in contrast to the wild-type variants, are N-glycosylated because of the fact that the mutant C termini project extracellularly. Podocin(P118L) and MEC-2(P134S) did not fractionate in detergent-resistant membrane domains. Moreover, mutant podocin failed to activate the ion channel TRPC6, which is part of the multiprotein-lipid supercomplex, indicative of the fact that cholesterol recruitment to the ion channels, an intrinsic function of both proteins, requires C termini facing the cytoplasmic leaflet of the plasma membrane. Taken together, this study demonstrates that the carboxyl terminus of podocin/MEC-2 has to be placed at the inner leaflet of the plasma membrane to mediate cholesterol binding and contribute to ion channel activity, a prerequisite for mechanosensation and the integrity of the kidney filtration barrier.
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Affiliation(s)
- Eva-Maria Schurek
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Linus A Völker
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Judit Tax
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Tobias Lamkemeyer
- Cologne Excellence Cluster on Cellular Stress Responses in Ageing-associated Diseases, University of Cologne, 50931 Cologne, Germany
| | - Markus M Rinschen
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Denise Ungrue
- Cologne Excellence Cluster on Cellular Stress Responses in Ageing-associated Diseases, University of Cologne, 50931 Cologne, Germany
| | - John E Kratz
- Department of Biological Sciences, Columbia University, New York, New York 10027-6902, and
| | - Lalida Sirianant
- Department of Physiology, University of Regensburg, 93053 Regensburg, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, 93053 Regensburg, Germany
| | - Martin Chalfie
- Department of Biological Sciences, Columbia University, New York, New York 10027-6902, and
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany,; Cologne Excellence Cluster on Cellular Stress Responses in Ageing-associated Diseases, University of Cologne, 50931 Cologne, Germany,; Systems Biology of Ageing Cologne, University of Cologne, 50931 Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany,; Cologne Excellence Cluster on Cellular Stress Responses in Ageing-associated Diseases, University of Cologne, 50931 Cologne, Germany,; Systems Biology of Ageing Cologne, University of Cologne, 50931 Cologne, Germany,.
| | - Martin Höhne
- Systems Biology of Ageing Cologne, University of Cologne, 50931 Cologne, Germany,; Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
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Eberhart CG, Kratz JE, Schuster A, Goldthwaite P, Cohen KJ, Perlman EJ, Burger PC. Comparative genomic hybridization detects an increased number of chromosomal alterations in large cell/anaplastic medulloblastomas. Brain Pathol 2006; 12:36-44. [PMID: 11770900 PMCID: PMC8095918 DOI: 10.1111/j.1750-3639.2002.tb00420.x] [Citation(s) in RCA: 87] [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] [Indexed: 01/01/2023] Open
Abstract
We correlate chromosomal changes in medulloblastomas with histologic subtype, reporting the analysis of 33 medulloblastoma specimens by comparative genomic hybridization, and a subset by fluorescence in situ hybridization. Of the 33 tumors, 5 were desmoplastic/nodular, 10 were histologically classic, and 18 were large cell/anaplastic. Chromosomal gains and losses were more common in anaplastic medulloblastomas than in non-anaplastic ones. We identified 4 medulloblastomas with c-myc amplification and 5 medulloblastomas with N-myc amplification; all 9 were of the large cell/anaplastic subtype. Additional regions with high level gains included 2q14-22, 3p23, 5p14-pter, 8q24, 9p22-23, 10p12-pter, 12q24, 12p11-12, 17p11-12, and Xp11. The majority of these high level gains occurred in anaplastic cases. We also found loss of chromosome 17p in 7 large cell/anaplastic cases but no nonanaplastic medulloblastomas. Finally, we detected a significantly increased overall number of chromosomal alterations in large cell/anaplastic medulloblastomas (6.8/case) compared to non-anaplastic ones (3.3/case). These findings support an association between myc oncogene amplification, 17p loss, and large cell/anaplastic histology.
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Affiliation(s)
- Charles G Eberhart
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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Kratz JE, Stearns D, Huso DL, Slunt HH, Price DL, Borchelt DR, Eberhart CG. Expression of stabilized beta-catenin in differentiated neurons of transgenic mice does not result in tumor formation. BMC Cancer 2002; 2:33. [PMID: 12460454 PMCID: PMC139989 DOI: 10.1186/1471-2407-2-33] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2002] [Accepted: 12/02/2002] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Medulloblastomas, embryonal tumors arising in the cerebellum, commonly contain mutations that activate Wnt signaling. To determine whether increased Wnt signaling in the adult CNS is sufficient to induce tumor formation, we created transgenic mice expressing either wild-type or activated beta-catenin in the brain. METHODS Wild-type and mutant human beta-catenin transgenes were expressed under the control of a murine PrP promoter fragment that drives high level postnatal expression in the CNS. Mutant beta-catenin was stabilized by a serine to phenylalanine alteration in codon 37. RESULTS Expression of the mutant transgene resulted in an approximately two-fold increase in beta-catenin protein levels in the cortex and cerebellum of adult animals. Immunohistochemical analysis revealed nuclear beta-catenin in hippocampal, cortical and cerebellar neurons of transgenic animals but not in non-transgenic controls. Tail kinking was observed in some transgenic animals, but no CNS malformations or tumors were detected. CONCLUSIONS No tumors or morphologic alterations were detected in the brains of transgenic mice expressing stabilized beta-catenin, suggesting that postnatal Wnt signaling in differentiated neurons may not be sufficient to induce CNS tumorigenesis.
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Affiliation(s)
- John E Kratz
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Duncan Stearns
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David L Huso
- Department of Comparative Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hilda H Slunt
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Donald L Price
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David R Borchelt
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Charles G Eberhart
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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