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Zhao W, Fan J, Kulic I, Koh C, Clark A, Meuller J, Engkvist O, Barichievy S, Raynoschek C, Hicks R, Maresca M, Wang Q, Brown DG, Lok A, Parro C, Robert J, Chou HY, Zuhl AM, Wood MW, Brandon NJ, Wellington CL. Axl receptor tyrosine kinase is a regulator of apolipoprotein E. Mol Brain 2020; 13:66. [PMID: 32366277 PMCID: PMC7197143 DOI: 10.1186/s13041-020-00609-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [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: 12/26/2019] [Accepted: 04/24/2020] [Indexed: 12/13/2022] Open
Abstract
Alzheimer's disease (AD), the leading cause of dementia, is a chronic neurodegenerative disease. Apolipoprotein E (apoE), which carries lipids in the brain in the form of lipoproteins, plays an undisputed role in AD pathophysiology. A high-throughput phenotypic screen was conducted using a CCF-STTG1 human astrocytoma cell line to identify small molecules that could upregulate apoE secretion. AZ7235, a previously discovered Axl kinase inhibitor, was identified to have robust apoE activity in brain microglia, astrocytes and pericytes. AZ7235 also increased expression of ATP-binding cassette protein A1 (ABCA1), which is involved in the lipidation and secretion of apoE. Moreover, AZ7235 did not exhibit Liver-X-Receptor (LXR) activity and stimulated apoE and ABCA1 expression in the absence of LXR. Target validation studies using AXL-/- CCF-STTG1 cells showed that Axl is required to mediate AZ7235 upregulation of apoE and ABCA1. Intriguingly, apoE expression and secretion was significantly attenuated in AXL-deficient CCF-STTG1 cells and reconstitution of Axl or kinase-dead Axl significantly restored apoE baseline levels, demonstrating that Axl also plays a role in maintaining apoE homeostasis in astrocytes independent of its kinase activity. Lastly, these effects may require human apoE regulatory sequences, as AZ7235 exhibited little stimulatory activity toward apoE and ABCA1 in primary murine glia derived from neonatal human APOE3 targeted-replacement mice. Collectively, we identified a small molecule that exhibits robust apoE and ABCA1 activity independent of the LXR pathway in human cells and elucidated a novel relationship between Axl and apoE homeostasis in human astrocytes.
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Affiliation(s)
- Wenchen Zhao
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Jianjia Fan
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Iva Kulic
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Cheryl Koh
- Mechanistic Biology & Profiling, Discovery Sciences, R&D, AstraZeneca, Boston, USA
| | - Amanda Clark
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Johan Meuller
- Mechanistic Biology & Profiling, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Ola Engkvist
- Hit Discovery, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | | | - Carina Raynoschek
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Ryan Hicks
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Marcello Maresca
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Qi Wang
- Neuroscience, BioPharmaceuticals R&D, AstraZeneca, Boston, USA
| | - Dean G Brown
- Hit Discovery, Discovery Sciences, R&D, AstraZeneca, Boston, USA
| | - Alvin Lok
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Cameron Parro
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Jerome Robert
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Hsien-Ya Chou
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada
| | - Andrea M Zuhl
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Boston, USA
| | - Michael W Wood
- Neuroscience, BioPharmaceuticals R&D, AstraZeneca, Boston, USA
| | | | - Cheryl L Wellington
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada.
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Fan J, Zhao RQ, Parro C, Zhao W, Chou HY, Robert J, Deeb TZ, Raynoschek C, Barichievy S, Engkvist O, Maresca M, Hicks R, Meuller J, Moss SJ, Brandon NJ, Wood MW, Kulic I, Wellington CL. Small molecule inducers of ABCA1 and apoE that act through indirect activation of the LXR pathway. J Lipid Res 2018; 59:830-842. [PMID: 29563219 DOI: 10.1194/jlr.m081851] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [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: 11/09/2017] [Revised: 02/13/2018] [Indexed: 01/01/2023] Open
Abstract
apoE is the primary lipid carrier within the CNS and the strongest genetic risk factor for late onset Alzheimer's disease (AD). apoE is primarily lipidated via ABCA1, and both are under transcriptional regulation by the nuclear liver X receptor (LXR). Considerable evidence from genetic (using ABCA1 overexpression) and pharmacological (using synthetic LXR agonists) studies in AD mouse models suggests that increased levels of lipidated apoE can improve cognitive performance and, in some strains, can reduce amyloid burden. However, direct synthetic LXR ligands have hepatotoxic side effects that limit their clinical use. Here, we describe a set of small molecules, previously annotated as antagonists of the purinergic receptor, P2X7, which enhance ABCA1 expression and activity as well as apoE secretion, and are not direct LXR ligands. Furthermore, P2X7 is not required for these molecules to induce ABCA1 upregulation and apoE secretion, demonstrating that the ABCA1 and apoE effects are mechanistically independent of P2X7 inhibition. Hence, we have identified novel dual activity compounds that upregulate ABCA1 across multiple CNS cell types, including human astrocytes, pericytes, and microglia, through an indirect LXR mechanism and that also independently inhibit P2X7 receptor activity.
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Affiliation(s)
- Jianjia Fan
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rui Qi Zhao
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Cameron Parro
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Wenchen Zhao
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hsien-Ya Chou
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jerome Robert
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tarek Z Deeb
- Tufts-AstraZeneca Laboratory for Basic and Translational Neuroscience, Boston, MA
| | - Carina Raynoschek
- Discovery Sciences, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Samantha Barichievy
- Discovery Sciences, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Ola Engkvist
- Discovery Sciences, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Marcello Maresca
- Discovery Sciences, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Ryan Hicks
- Discovery Sciences, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Johan Meuller
- Discovery Sciences, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Stephen J Moss
- Tufts-AstraZeneca Laboratory for Basic and Translational Neuroscience, Boston, MA.,Department of Neuroscience, Tufts University School of Medicine, Boston, MA and Department of Neuroscience, Physiology, and Pharmacology, University College London, London, United Kingdom
| | - Nicholas J Brandon
- Neuroscience, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Boston, MA
| | - Michael W Wood
- Neuroscience, Innovative Medicines and Early Development (IMED) Biotech Unit, AstraZeneca, Boston, MA
| | - Iva Kulic
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
| | - Cheryl L Wellington
- Department of Pathology and Laboratory Medicine, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada
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Ahmad S, Dahllund L, Eriksson AB, Hellgren D, Karlsson U, Lund PE, Meijer IA, Meury L, Mills T, Moody A, Morinville A, Morten J, O'donnell D, Raynoschek C, Salter H, Rouleau GA, Krupp JJ. A stop codon mutation in SCN9A causes lack of pain sensation. Hum Mol Genet 2007; 16:2114-21. [PMID: 17597096 DOI: 10.1093/hmg/ddm160] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [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: 11/14/2022] Open
Abstract
The general lack of pain experience is a rare occurrence in humans, and the molecular causes for this phenotype are not well understood. Here we have studied a Canadian family from Newfoundland with members who exhibit a congenital inability to experience pain. We have mapped the locus to a 13.7 Mb region on chromosome 2q (2q24.3-2q31.1). Screening of candidate genes in this region identified a protein-truncating mutation in SCN9A, which encodes for the voltage-gated sodium channel Na(v)1.7. The mutation is a C-A transversion at nucleotide 984 transforming the codon for tyrosine 328 to a stop codon. The predicted product lacks all pore-forming regions of Na(v)1.7. Indeed, expression of this altered gene in a cell line did not produce functional responses, nor did it cause compensatory effects on endogenous voltage-gated sodium currents when expressed in ND7/23 cells. Because a homozygous knockout of Na(v)1.7 in mice has been shown to be lethal, we explored why a deficiency of Na(v)1.7 is non-lethal in humans. Expression studies in monkey, human, mouse and rat tissue indicated species-differences in the Na(v)1.7 expression profile. Whereas in rodents the channel was strongly expressed in hypothalamic nuclei, only weak mRNA levels were detected in this area in primates. Furthermore, primate pituitary and adrenal glands were devoid of signal, whereas these two glands were mRNA-positive in rodents. This species difference may explain the non-lethality of the observed mutation in humans. Our data further establish Na(v)1.7 as a critical element of peripheral nociception in humans.
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Affiliation(s)
- Sultan Ahmad
- Department of Molecular Sciences, AstraZeneca R&D Montréal, Ville-St-Laurent, Quebec, Canada
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Trupp M, Raynoschek C, Belluardo N, Ibáñez CF. Multiple GPI-anchored receptors control GDNF-dependent and independent activation of the c-Ret receptor tyrosine kinase. Mol Cell Neurosci 1998; 11:47-63. [PMID: 9608533 DOI: 10.1006/mcne.1998.0667] [Citation(s) in RCA: 144] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glial cell line-derived neurotrophic factor (GDNF) mediates neuronal survival through a receptor complex composed of the c-Retproto-oncogene and GFR alpha-1, a member of a family of GPI-anchored receptors. The extent of cross-talk between GDNF and GFR alpha receptors and its possible significance for c-Ret activation is presently unclear. Using chemical crosslinking we demonstrate here a specific interaction between GDNF and GFR alpha-2 expressed in COS cells, albeit of a lower affinity than the one between GDNF and GFR alpha-1. In addition, GFR alpha-2 mediated crosslinking of GDNF of c-Ret as well as ligand-dependent stimulation of c-Ret tyrosine phosphorylation. We also describe the isolation of a novel, more divergent member of the GFR alpha family, GFR alpha-3, which did not bind GDNF directly, but was able to mediate crosslinking of GDNF to c-Ret when both receptors were coexpressed in COS cells. Thus, all three GFR alpha receptors mediate GDNF binding to c-Ret with efficiencies GFR alpha-1 > GFR alpha-2 > GFR alpha-3. c-Ret showed high levels of constitutive tyrosine autophosphorylation upon overexpression in COS cells, which was inhibited in a dose-dependent manner by coexpression with any of the GFR alpha receptors, suggesting that GFR alpha s may also provide a gain control mechanism to increase the signal-to-noise ratio of the response to ligand. GFR alpha-2 showed a dynamic pattern of expression in rat brain, distinct from that of GFR alpha-1, characterized by high expression in cortex, basal forebrain, and specific layers of the olfactory bulb, and low or no expression in substantia nigra, cerebellum, and motor nuclei. GFR alpha-2, but not GFR alpha-3 mRNA expression was highly induced in several nuclei after stimulation with kainic acid. In contrast to GFR alpha-1 and GFR alpha-2, GFR alpha-3 expression in postnatal and adult brain was highly restricted. Developmentally regulated expression of GFR alpha-3 was, however, detected in several peripheral organs and ganglia. Together, these results indicate complementary roles for GFR alpha receptors in the regulation of c-Ret activity and the maintenance of distinct neuronal circuits in the central and peripheral nervous systems.
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Affiliation(s)
- M Trupp
- Department of Neuroscience, Karolinska Institute, Stockholm, Sweden
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5
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Wang P, Raynoschek C, Svensson K, Ljunggren HG. Binding of H-2Kb-specific peptides to TAP and major histocompatibility complex class I in microsomes from wild-type, TAP1, and beta2-microglobulin mutant mice. J Biol Chem 1996; 271:24830-5. [PMID: 8798757 DOI: 10.1074/jbc.271.40.24830] [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: 02/02/2023] Open
Abstract
Major histocompatibility complex (MHC) class I molecules are trimolecular complexes consisting of a heavy chain (HC), beta2-microglobulin (beta2m), and a short peptide. Assembly of MHC class I molecules is thought to take place early during biosynthesis. Deficiency in either beta2m or the transporter associated with antigen processing (TAP) results in accumulation of class I molecules in the endoplasmic reticulum (ER). In this study, we have assessed peptide binding to TAP and MHC class I in purified microsomes derived from wild-type, TAP1(-/-), beta2m-/-, and TAP1/beta2m-/- mice using a cross-linkable H-2Kb-binding peptide. This enabled us to study the influence of an intact TAP complex and beta2m on peptide binding to MHC class I and to analyze the stepwise interaction of peptide with TAP and MHC class I molecules. Peptide bound both immature and mature (terminally glycosylated) class I molecules in intact as well as permeabilized microsomes from wild-type mice. Efficient peptide binding to immature class I molecules was also detected in permeabilized microsomes from TAP1(-/-) mice. In contrast, no peptide binding to beta2m-free HC was detected in permeabilized microsomes from beta2m-/- and TAP1/beta2m-/- mice. However, the addition of exogenous beta2m allowed peptide binding to class I in permeabilized beta2m-/- and TAP1/beta2m-/- microsomes. These results demonstrate that a preformed class I HC middle dotbeta2m heterodimer is necessary for efficient peptide binding under physiological conditions. The observed peptide binding to class I in permeabilized TAP1(-/-) microsomes further suggests that TAP1 is not required for peptide binding to class I in the ER. Finally, kinetic studies allowed the demonstration of a stepwise binding of peptide to TAP, subsequent translocation across the ER membrane, a step that required ATP hydrolysis, and binding of peptide to preformed class I HC.beta2m heterodimers.
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Affiliation(s)
- P Wang
- Ludwig Institute for Cancer Research, Stockholm Branch, Box 240, S-171 77 Stockholm, Sweden
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Ryseck RP, Raynoschek C, Macdonald-Bravo H, Dorfman K, Mattéi MG, Bravo R. Identification of an immediate early gene, pghs-B, whose protein product has prostaglandin synthase/cyclooxygenase activity. Cell Growth Differ 1992; 3:443-50. [PMID: 1419907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We have characterized a growth factor-inducible gene, pghs-B, isolated by differential screening of a lambda complementary DNA library from RNA of serum-stimulated NIH 3T3 cells which encodes a 604-amino acid protein presenting high similarity with prostaglandin G/H synthase (PGHS). Induction of both pghs-B mRNA and protein is rapid and remains at high levels for several hours. The increase in pghs-B mRNA is mainly due to transcriptional activation of the gene. PGHS-B has been expressed in the baculovirus system and has been demonstrated to be involved in prostaglandin synthesis and to be inhibited by indomethacin, demonstrating that PGHS-B is indeed an enzyme related to PGHS. The pghs-B gene maps to the [1G-1H2] region of the murine genome.
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Affiliation(s)
- R P Ryseck
- Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000
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Kovary K, Rizzo CA, Ryseck RP, Noguchi T, Raynoschek C, Pelosin JM, Bravo R. Constitutive expression of FosB and its short form, FosB/SF, induces malignant cell transformation in rat-1A cells. New Biol 1991; 3:870-9. [PMID: 1931831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have established Rat-1A cell lines constitutively expressing c-Fos and the two products of the fosB gene, FosB and its short form, FosB/SF. The expressed proteins in the different stable transfectants have been characterized by immunofluorescence and immunoprecipitation analysis. Our results demonstrate that constitutive expression of FosB, like the constitutive expression of c-Fos and, to a lesser extent, FosB/SF, results in cells that grow to increased saturation densities and have the ability to grow in an anchorage-independent manner. Most important is the finding that expression of these proteins augments the tumorigenic potential of Rat-1A cells. These results show that both forms of FosB have a stimulatory effect on cell proliferation.
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Affiliation(s)
- K Kovary
- Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543-4000
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Schroeder C, Raynoschek C, Fuhrmann U, Damm K, Vennström B, Beug H. The v-erb A oncogene causes repression of erythrocyte-specific genes and an immature, aberrant differentiation phenotype in normal erythroid progenitors. Oncogene 1990; 5:1445-53. [PMID: 1979159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have compared the effects of the v-erb A oncogene on proliferation and differentiation of normal erythroid progenitors with those of tyrosine kinase oncogenes, e.g. v-sea. For this, a v-erb A retrovirus containing the neomycin resistance gene as a selectable marker or, alternatively, a v-erb A-ts v-sea retrovirus were used to infect normal bone marrow cells. V-erb A induced the outgrowth of immature, erythropoietin(EPO)-dependent erythroid cells from infected bone marrow which ceased to proliferate and disintegrated after 9 to 18 divisions. In contrast, ts-v-sea erythroblasts grew for the expected 25 to 40 population doublings in the absence of EPO. Transcription of the erythrocyte genes carbonic anhydrase II and erythrocyte anion transporter was significantly inhibited in v-erb A infected erythroblasts, indicating that v-erb A alone was sufficient for the repression of the erythrocyte-specific genes observed in AEV-transformed leukemic cells. A detailed analysis of the differentiation phenotype induced by v-erb A in erythroblasts (in the presence or absence of a temperature-inactivated ts sea oncogene) indicates that v-erb A-erythroblasts express a partially mature, aberrant phenotype characterized by the coexpression of mature and immature differentiation antigens. This phenotype clearly differs from that induced by tyrosine kinase oncogenes in erythroid cells.
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Affiliation(s)
- C Schroeder
- Institute of Molecular Pathology, Vienna, Austria
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Forrest D, Muñoz A, Raynoschek C, Vennström B, Beug H. Requirement for the C-terminal domain of the v-erbA oncogene protein for biological function and transcriptional repression. Oncogene 1990; 5:309-16. [PMID: 1969136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In contrast to the normal thyroid hormone receptor, the v-erbA product fails to bind hormone due to mutations in the C-terminal ligand binding domain and thus appears to represent a hormone-independent, oncogenic transcription factor. Therefore, we asked whether or not the C-terminal domain of v-erbA is required for its biological activity and putative transcriptional control functions by analysing mutants with altered C-termini. A v-erbA protein truncated in the C-terminal domain lacked detectable biological activity in transformed erythroblasts and its transcriptional repression function with respect to the band 3 gene was abolished. The protein displayed a nuclear location and could still bind to DNA, indicating that the N-terminal region retained DNA-binding activity but was insufficient to produce characteristic v-erbA changes in erythroblasts. Another biologically defective v-erbA variant with a small frameshift towards the extreme C-terminus also failed to repress band 3, indicating a requirement for a specific C-terminal structure in repression. However, this mutant retained partial biological activity, stimulating erythroblasts to grow at a higher rate than cells containing a completely inactive, deleted v-erbA gene. The results demonstrate that the mutated hormone-binding domain, in addition to the DNA-binding region, is critical for v-erbA biological and transcriptional control functions.
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Affiliation(s)
- D Forrest
- Department of Molecular Biology, Karolinska Institute, Stockholm, Sweden
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