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Gomez-Soler M, Gehring MP, Lechtenberg BC, Zapata-Mercado E, Ruelos A, Matsumoto MW, Hristova K, Pasquale EB. Ligands with different dimeric configurations potently activate the EphA2 receptor and reveal its potential for biased signaling. iScience 2022; 25:103870. [PMID: 35243233 PMCID: PMC8858996 DOI: 10.1016/j.isci.2022.103870] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 12/13/2021] [Accepted: 02/01/2022] [Indexed: 12/03/2022] Open
Abstract
The EphA2 receptor tyrosine kinase activates signaling pathways with different, and sometimes opposite, effects in cancer and other pathologies. Thus, highly specific and potent biased ligands that differentially control EphA2 signaling responses could be therapeutically valuable. Here, we use EphA2-specific monomeric peptides to engineer dimeric ligands with three different geometric configurations to combine a potential ability to differentially modulate EphA2 signaling responses with the high potency and prolonged receptor residence time characteristic of dimeric ligands. The different dimeric peptides readily induce EphA2 clustering, autophosphorylation and signaling, the best with sub-nanomolar potency. Yet, there are differences in two EphA2 signaling responses induced by peptides with different configurations, which exhibit distinct potency and efficacy. The peptides bias signaling when compared with the ephrinA1-Fc ligand and do so via different mechanisms. These findings provide insights into Eph receptor signaling, and proof-of-principle that different Eph signaling responses can be distinctly modulated.
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Affiliation(s)
- Maricel Gomez-Soler
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Marina P. Gehring
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Bernhard C. Lechtenberg
- Ubiquitin Signalling Division, The Walter and Eliza Hall Institute of Medical Research, Parkville Victoria 3052, Australia and Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Elmer Zapata-Mercado
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Alyssa Ruelos
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Mike W. Matsumoto
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Elena B. Pasquale
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
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2
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Protein-Protein Interaction Inhibitors Targeting the Eph-Ephrin System with a Focus on Amino Acid Conjugates of Bile Acids. Pharmaceuticals (Basel) 2022; 15:ph15020137. [PMID: 35215250 PMCID: PMC8880657 DOI: 10.3390/ph15020137] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 02/05/2023] Open
Abstract
The role of the Eph-ephrin system in the etiology of pathological conditions has been consolidated throughout the years. In this context, approaches directed against this signaling system, intended to modulate its activity, can be strategic therapeutic opportunities. Currently, the most promising class of compounds able to interfere with the Eph receptor-ephrin protein interaction is composed of synthetic derivatives of bile acids. In the present review, we summarize the progresses achieved, in terms of chemical expansions and structure-activity relationships, both in the steroidal core and the terminal carboxylic acid group, along with the pharmacological characterization for the most promising Eph-ephrin antagonists in in vivo settings.
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N'Tumba-Byn T, Yamada M, Seandel M. Loss of tyrosine kinase receptor Ephb2 impairs proliferation and stem cell activity of spermatogonia in culture†. Biol Reprod 2021; 102:950-962. [PMID: 31836902 DOI: 10.1093/biolre/ioz222] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/30/2019] [Accepted: 12/11/2019] [Indexed: 12/17/2022] Open
Abstract
Germline stem and progenitor cells can be extracted from the adult mouse testis and maintained long-term in vitro. Yet, the optimal culture conditions for preserving stem cell activity are unknown. Recently, multiple members of the Eph receptor family were detected in murine spermatogonia, but their roles remain obscure. One such gene, Ephb2, is crucial for maintenance of somatic stem cells and was previously found enriched at the level of mRNA in murine spermatogonia. We detected Ephb2 mRNA and protein in primary adult spermatogonial cultures and hypothesized that Ephb2 plays a role in maintenance of stem cells in vitro. We employed CRISPR-Cas9 targeting and generated stable mutant SSC lines with complete loss of Ephb2. The characteristics of Ephb2-KO cells were interrogated using phenotypic and functional assays. Ephb2-KO SSCs exhibited reduced proliferation compared to wild-type cells, while apoptosis was unaffected. Therefore, we examined whether Ephb2 loss correlates with activity of canonical pathways involved in stem cell self-renewal and proliferation. Ephb2-KO cells had reduced ERK MAPK signaling. Using a lentiviral transgene, Ephb2 expression was rescued in Ephb2-KO cells, which partially restored signaling and proliferation. Transplantation analysis revealed that Ephb2-KO SSCs cultures formed significantly fewer colonies than WT, indicating a role for Ephb2 in preserving stem cell activity of cultured cells. Transcriptome analysis of wild-type and Ephb2-KO SSCs identified Dppa4 and Bnc1 as differentially expressed, Ephb2-dependent genes that are potentially involved in stem cell function. These data uncover for the first time a crucial role for Ephb2 signaling in cultured SSCs.
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Affiliation(s)
- Thierry N'Tumba-Byn
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States of America
| | - Makiko Yamada
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States of America
| | - Marco Seandel
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States of America
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Towner RA, Gulej R, Zalles M, Saunders D, Smith N, Lerner M, Morton KA, Richardson A. Rapamycin restores brain vasculature, metabolism, and blood-brain barrier in an inflammaging model. GeroScience 2021; 43:563-578. [PMID: 33846885 PMCID: PMC8110648 DOI: 10.1007/s11357-021-00363-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 04/06/2021] [Indexed: 02/08/2023] Open
Abstract
Rapamycin (RAPA) is found to have neuro-protective properties in various neuroinflammatory pathologies, including brain aging. With magnetic resonance imaging (MRI) techniques, we investigated the effect of RAPA in a lipopolysaccharide (LPS)-induced inflammaging model in rat brains. Rats were exposed to saline (control), or LPS alone or LPS combined with RAPA treatment (via food over 6 weeks). Arterial spin labeling (ASL) perfusion imaging was used to measure relative cerebral blood flow (rCBF). MR spectroscopy (MRS) was used to measure brain metabolite levels. Contrast-enhanced MRI (CE-MRI) was used to assess blood-brain barrier (BBB) permeability. Immunohistochemistry (IHC) was used to confirm neuroinflammation. RAPA restored NF-κB and HIF-1α to normal levels. RAPA was able to significantly restore rCBF in the cerebral cortex post-LPS exposure (p < 0.05), but not in the hippocampus. In the hippocampus, RAPA was able to restore total creatine (Cr) acutely, and N-acetyl aspartate (NAA) at 6 weeks, post-LPS. Myo-inositol (Myo-Ins) levels were found to decrease with RAPA treatment acutely post-LPS. RAPA was also able to significantly restore the BBB acutely post-LPS in both the cortex and hippocampus (p < 0.05 for both). RAPA was found to increase the percent change in BOLD signal in the cortex at 3 weeks, and in the hippocampus at 6 weeks post-LPS, compared to LPS alone. RAPA treatment also restored the neuronal and macro-vascular marker, EphB2, back to normal levels. These results indicate that RAPA may play an important therapeutic role in inhibiting neuroinflammation by normalizing brain vascularity, BBB, and some brain metabolites, and has a high translational capability.
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Affiliation(s)
- Rheal A Towner
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK, 73104, USA.
- Neuroscience Program, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- Oklahoma Nathan Shock Center for Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
| | - Rafal Gulej
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK, 73104, USA
| | - Michelle Zalles
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK, 73104, USA
- Neuroscience Program, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Debra Saunders
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK, 73104, USA
| | - Nataliya Smith
- Advanced Magnetic Resonance Center, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK, 73104, USA
| | - Megan Lerner
- Department of Surgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Kathryn A Morton
- Department of Radiology and Imaging Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Arlan Richardson
- Oklahoma Nathan Shock Center for Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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5
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Li P, Chen W, Wang Y, Fu X, Wen K, Qian J, Huang C, Fu Z. Effects of ephrinB2 gene siRNA on the biological behavior of human colorectal cancer cells. Oncol Rep 2014; 33:758-66. [PMID: 25434750 DOI: 10.3892/or.2014.3633] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 10/09/2014] [Indexed: 11/05/2022] Open
Abstract
Colorectal cancer (CRC) is a common gastrointestinal malignancy worldwide and is a lethal and aggressive malignancy with a dismal prognosis. EphrinB2 is a membrane-bound ligand and has an intracellular domain that also possesses an intrinsic signaling capacity called 'reverse signaling'. In the present study, CRC cell lines were screened for high expression of ephrinB2. Small interfering RNA (siRNA) knockdown of ephrinB2 was performed in human SW480 CRC cells. The levels of expression of ephrinB2, VEGF, CD105 and matrix metalloproteinase 9 (MMP9) protein were measured by western blotting, and messenger RNA (mRNA) levels were measured using real-time PCR. Apoptosis and cell cycle distribution were determined using flow cytometry. Cell proliferation was measured by a methyl thiazole tetrazolium (MTT) test and a scratch healing experiment was used to measure the extent of cell migration. A Transwell assay was used to detect the extent of cell invasion. The results showed that RNA interference (RNAi) of ephrinB2 effectively silenced the ephrinB2 gene at both the mRNA and protein levels in SW480 cells and inhibited the proliferation, invasion, migration and angiogenesis and induced apoptosis in SW480 cells. These effects may be attributed to VEGF and MMP9 regulation.
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Affiliation(s)
- Peiwu Li
- Department of General Surgery, First Affiliated Hospital, Chongqing Medical University, Chongqing 400010, P.R. China
| | - Wangsheng Chen
- Department of General Surgery, First Affiliated Hospital, Chongqing Medical University, Chongqing 400010, P.R. China
| | - Yingzhen Wang
- Department of Emergency, Lanzhou University Second Hospital, Lanzhou 730000, P.R. China
| | - Xu Fu
- Department of Emergency, Lanzhou University Second Hospital, Lanzhou 730000, P.R. China
| | - Kunming Wen
- Department of General Surgery, First Affiliated Hospital, Chongqing Medical University, Chongqing 400010, P.R. China
| | - Jiang Qian
- Department of General Surgery, First Affiliated Hospital, Chongqing Medical University, Chongqing 400010, P.R. China
| | - Chun Huang
- Department of General Surgery, First Affiliated Hospital, Chongqing Medical University, Chongqing 400010, P.R. China
| | - Zhongxue Fu
- Department of General Surgery, First Affiliated Hospital, Chongqing Medical University, Chongqing 400010, P.R. China
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Lisabeth EM, Falivelli G, Pasquale EB. Eph receptor signaling and ephrins. Cold Spring Harb Perspect Biol 2013; 5:5/9/a009159. [PMID: 24003208 DOI: 10.1101/cshperspect.a009159] [Citation(s) in RCA: 281] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Eph receptors are the largest of the RTK families. Like other RTKs, they transduce signals from the cell exterior to the interior through ligand-induced activation of their kinase domain. However, the Eph receptors also have distinctive features. Instead of binding soluble ligands, they generally mediate contact-dependent cell-cell communication by interacting with surface-associated ligands-the ephrins-on neighboring cells. Eph receptor-ephrin complexes emanate bidirectional signals that affect both receptor- and ephrin-expressing cells. Intriguingly, ephrins can also attenuate signaling by Eph receptors coexpressed in the same cell. Additionally, Eph receptors can modulate cell behavior independently of ephrin binding and kinase activity. The Eph/ephrin system regulates many developmental processes and adult tissue homeostasis. Its abnormal function has been implicated in various diseases, including cancer. Thus, Eph receptors represent promising therapeutic targets. However, more research is needed to better understand the many aspects of their complex biology that remain mysterious.
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Affiliation(s)
- Erika M Lisabeth
- Cancer Center, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, USA
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Tandon M, Vemula SV, Mittal SK. Emerging strategies for EphA2 receptor targeting for cancer therapeutics. Expert Opin Ther Targets 2011; 15:31-51. [PMID: 21142802 DOI: 10.1517/14728222.2011.538682] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
IMPORTANCE OF THE FIELD High mortality rates with cancers warrant further development of earlier diagnostics and better treatment strategies. Membrane-bound erythropoietin-producing hepatocellular receptor tyrosine kinase class A2 (EphA2) is overexpressed in breast, prostate, urinary bladder, skin, lung, ovary and brain cancers. AREAS COVERED IN THIS REVIEW EphA2 overexpression in cancers, its signaling mechanisms and strategies to target its deregulation. WHAT THE READER WILL GAIN High EphA2 expression in cancer cells is correlated with a poor prognosis associated with recurrence due to enhanced metastasis. Interaction of the EphA2 receptor with its ligand (e.g., ephrinA1) triggers events that are deregulated and implicated in carcinogenesis. EphrinA1-independent oncogenic activity and ephrinA1-dependent tumor suppressor roles for EphA2 are described. Molecular interactions of EphA2 with signaling proteins are associated with the modulation of cytoskeleton dynamics, cell adhesion, proliferation, differentiation and metastasis. The deregulated signaling by EphA2 and its involvement in oncogenesis provide multiple avenues for the rational design of intervention approaches. TAKE HOME MESSAGE EphA2 has been tested as a drug target using multiple approaches such as agonist antibodies, RNA interference, immunotherapy, virus vector-mediated gene transfer, small-molecule inhibitors and nanoparticles. With over a decade of research, encouraging results with targeting of EphA2 expression in various pre-clinical cancer models necessitate further studies.
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Affiliation(s)
- Manish Tandon
- Purdue University, Department of Comparative Pathobiology, Bindley Bioscience Center, West Lafayette, IN 47907, USA
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8
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Muñoz JJ, Cejalvo T, Alonso-Colmenar LM, Alfaro D, Garcia-Ceca J, Zapata A. Eph/Ephrin-mediated interactions in the thymus. Neuroimmunomodulation 2011; 18:271-80. [PMID: 21952679 DOI: 10.1159/000329490] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
In the present study, we review available information on the relevance of Eph and ephrins in numerous processes occurring in the thymus that regulate not only T cell differentiation but also thymic epithelial cell (TEC) development and organization. Eph/ephrins are a large family of receptors and ligands involved in organogenesis and homeostasis of adult tissues. They are extensively expressed in the thymus and seem to be involved in the colonization of lymphoid progenitor cells and their migration throughout the thymic parenchyma necessary to provide an adequate topological location of developing thymocytes in the epithelial network that ensures their correct differentiation. In addition, EphB2 and EphB3 play a cell-autonomous role in regulating the transitions of double-negative to double-positive cells and of double-positive to single-positive thymocytes and the lack of these molecules or their ligands ephrin B1 and ephrin B2 induces profound alterations of the TEC maturation and in the arrangement of epithelial network. We emphasize that these results are largely reflecting the role played by this family of molecules in controlling thymocyte-TEC interactions within the thymus.
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Affiliation(s)
- Juan Jose Muñoz
- Cytometry and Fluorescence Microscopy Center, Faculty of Biology, Complutense University, Madrid, Spain
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Yu G, Gao Y, Ni C, Chen Y, Pan J, Wang X, Ding Z, Wang J. Reduced expression of EphB2 is significantly associated with nodal metastasis in Chinese patients with gastric cancer. J Cancer Res Clin Oncol 2010; 137:73-80. [PMID: 20238226 DOI: 10.1007/s00432-010-0861-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 02/22/2010] [Indexed: 12/20/2022]
Abstract
AIMS EphB2 is a member of the Eph receptor tyrosine kinase family that has been involved in the regulation of cytoskeleton organization and cell migration in various cell types. Its role and regulation in carcinogenesis is controversial, especially in gastric cancer. We detected EphB2 expression and determined its clinical significance and explored its underlying molecular mechanism in gastric cancers. METHODS Tissue microarray blocks containing primary gastric cancer, lymph node metastases, and adjacent normal mucosa specimens obtained from 337 Chinese patients were constructed. Expression of EphB2 in these specimens was analyzed using immunohistochemistry. Mutation analysis at the A9 tract in exon 17 and loss of heterozygosity analysis at the EphB2 gene locus were carried out in 13 sporadic EphB2-negative gastric cancers. RESULTS Complete loss of EphB2 expression was observed in 177 (52.5%) of the 337 primary tumor and 41 (82%) of the 50 nodal metastases. Loss of EphB2 expression was significantly associated with advanced T stage, nodal metastasis, advanced disease stage, and poor histological differentiation. Loss of EphB2 expression correlated significantly with poor survival rates in both univariate and multivariate analysis. No frameshift mutation, but a higher frequency of allelic loss, was found in EphB2-negative primary and metastatic tumor samples. CONCLUSIONS Frequent deletion and decreased expression of EphB2 protein suggested it as a negative biomarker for gastric carcinogenesis and a potential predictor of the outcome of patients with gastric cancer.
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Affiliation(s)
- Guanzhen Yu
- Department of Medical Oncology, Changzheng Hospital, Hetian Road 64, Shanghai 200070, People's Republic of China
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10
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Abstract
The Eph receptor tyrosine kinases and their ephrin ligands have intriguing expression patterns in cancer cells and tumour blood vessels, which suggest important roles for their bidirectional signals in many aspects of cancer development and progression. Eph gene mutations probably also contribute to cancer pathogenesis. Eph receptors and ephrins have been shown to affect the growth, migration and invasion of cancer cells in culture as well as tumour growth, invasiveness, angiogenesis and metastasis in vivo. However, Eph signalling activities in cancer seem to be complex, and are characterized by puzzling dichotomies. Nevertheless, the Eph receptors are promising new therapeutic targets in cancer.
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Affiliation(s)
- Elena B Pasquale
- Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.
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11
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Taddei ML, Parri M, Angelucci A, Onnis B, Bianchini F, Giannoni E, Raugei G, Calorini L, Rucci N, Teti A, Bologna M, Chiarugi P. Kinase-dependent and -independent roles of EphA2 in the regulation of prostate cancer invasion and metastasis. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 174:1492-503. [PMID: 19264906 DOI: 10.2353/ajpath.2009.080473] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ligand-activated Eph tyrosine kinases regulate cellular repulsion, morphology, adhesion, and motility. EphA2 kinase is frequently up-regulated in several different types of cancers, including prostate, breast, colon, and lung carcinomas, as well as in melanoma. The existing data do not clarify whether EphA2 receptor phosphorylation or its simple overexpression, which likely leads to Eph kinase-independent responses, plays a role in the progression of malignant prostate cancer. In this study, we address the role of EphA2 tyrosine phosphorylation in prostate carcinoma cell adhesion, motility, invasion, and formation of metastases. Tumor cells expressing kinase-deficient EphA2 mutants, as well as an EphA2 variant lacking the cytoplasmic domain, are defective in ephrinA1-mediated cell rounding, retraction fiber formation, de-adhesion from the extracellular matrix, RhoA and Rac1 GTPase regulation, three-dimensional matrix invasion, and in vivo metastasis, suggesting a key role for EphA2 kinase activity. Nevertheless, EphA2 regulation of cell motility and invasion, as well as the formation of bone and visceral tumor colonies, reveals a component of both EphA2 kinase-dependent and -independent features. These results uncover a differential requirement for EphA2 kinase activity in the regulation of prostate carcinoma metastasis outcome, suggesting that although the kinase activity of EphA2 is required for the regulation of cell adhesion and cytoskeletal rearrangement, some distinct kinase-dependent and -independent pathways likely cooperate to drive cancer cell migration, invasion, and metastasis outcome.
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Affiliation(s)
- Maria Letizia Taddei
- Department of Biochemical Sciences, University of Florence, viale Morgagni 50, 50134 Florence, Italy
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Abstract
Ephrins-A5 are expressed in the cortical target layer of thalamic afferents at the time when these axons form terminal arbors. Previous in-vitro studies provided evidence that ephrin-A5 supports the branching of thalamic axons, but there is no direct in-vivo evidence for such a growth-promoting effect. Here we examined thalamocortical projections in ephrins-A5 deficient mice. Our results demonstrate that the laminar specificity of thalamic afferents in ephrin-A5 mutants remains preserved, but axonal arbor formation is greatly reduced. Thus, ephrin-A5 specifically regulates branch formation of thalamic axons, but does not affect target layer selection. Ephrin-A5-mutant mice are, therefore, a unique model to study the effects of reduced thalamic innervation on the assembly of cortical circuits and sensory processing.
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Song JH, Kim CJ, Cho YG, Kwak HJ, Nam SW, Yoo NJ, Lee JY, Park WS. Genetic and epigenetic analysis of the EPHB2 gene in gastric cancers. APMIS 2007; 115:164-8. [PMID: 17295683 DOI: 10.1111/j.1600-0463.2007.apm_543.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
EPHB2 is a member of the Eph receptor tyrosine kinase family and a direct transcriptional target of beta-catenin/TCF. EPHB2 plays an important role in maintaining the correct positioning of the proliferative compartment in the crypt-villous axis. A loss of EPHB2 expression has been observed in human tumors, particularly in colonic adenomas and carcinomas. A search was made for mutations at the A9 tract in exon 17, an allelic loss at the EPHB2 gene locus, and promoter hypermethylation of the EPHB2 gene in 81 sporadic gastric cancers in order to determine if genetic or epigenetic alterations of the EPHB2 gene are involved in the development and/or progression of gastric cancer. Unexpectedly, no frameshift mutation was found and there was a low frequency (20.8%) of allelic loss. In addition, promoter hypermethylation was detected in only one gastric cancer tissue sample. Therefore, genetic or epigenetic alterations of the EPHB2 gene might be an uncommon event in the development or progression of gastric cancers.
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Affiliation(s)
- Jae Hwi Song
- Department of Pathology, College of Medicine, The Catholic University of Korea, Seoul, Korea
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14
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Abstract
Apolipoprotein E (APOE) is a cholesterol transport protein and an isoform-specific major risk factor for neurodegenerative diseases. The lipoprotein receptors that bind APOE have recently been recognized as pivotal components of the neuronal signalling machinery. The interaction between APOE receptors and one of their ligands, reelin, allows them to function directly as signal transduction receptors at the plasma membrane to control not only neuronal positioning during brain development, but also synaptic plasticity in the adult brain. Here, we review the molecular mechanisms through which APOE, cholesterol, reelin and APOE receptors control synaptic functions that are essential for cognition, learning, memory, behaviour and neuronal survival.
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Affiliation(s)
- Joachim Herz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texus 75390, USA.
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15
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Willson CA, Foster RD, Onifer SM, Whittemore SR, Miranda JD. EphB3 receptor and ligand expression in the adult rat brain. J Mol Histol 2006; 37:369-80. [PMID: 17103029 DOI: 10.1007/s10735-006-9067-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Accepted: 10/10/2006] [Indexed: 10/23/2022]
Abstract
Eph receptors and ligands are two families of proteins that control axonal guidance during development. Their expression was originally thought to be developmentally regulated but recent work has shown that several EphA receptors are expressed postnatally. The EphB3 receptors are expressed during embryonic development in multiple regions of the central nervous system but their potential expression and functional role in the adult brain is unknown. We used in situ hybridization, immunohistochemistry, and receptor affinity probe in situ staining to investigate EphB3 receptors mRNA, protein, and ligand (ephrin-B) expression, respectively, in the adult rat brain. Our results indicate that EphB3 receptor mRNA and protein are constitutively expressed in discrete regions of the adult rat brain including the cerebellum, raphe pallidus, hippocampus, entorhinal cortex, and both motor and sensory cortices. The spatial profile of EphB3 receptors was co-localized to regions of the brain that had a high level of EphB3 receptor binding ligands. Its expression pattern suggests that EphB3 may play a role in the maintenance of mature neuronal connections or re-arrangement of synaptic connections during late stages of development.
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Affiliation(s)
- Christopher A Willson
- Kentucky Spinal Cord Injury Research Center, School of Medicine, University of Louisville, Louisville, KY, USA
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Fang WB, Brantley-Sieders DM, Parker MA, Reith AD, Chen J. A kinase-dependent role for EphA2 receptor in promoting tumor growth and metastasis. Oncogene 2005; 24:7859-68. [PMID: 16103880 DOI: 10.1038/sj.onc.1208937] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Receptor tyrosine kinases of the Eph family are upregulated in several different types of cancer. One family member in particular, the EphA2 receptor, has been linked to breast, prostate, lung and colon cancer, as well as melanoma. However, mechanisms by which EphA2 contributes to tumor progression are far from clear. In certain tumor cell lines, EphA2 receptor is underphosphorylated, raising the question of whether ligand-induced receptor phosphorylation and its kinase activity play a role in oncogenesis. To test directly the role of EphA2 receptor phosphorylation/kinase activity in tumor progression, we generated EphA2 receptor variants that were either lacking the cytoplasmic domain or carrying a point mutation that inhibits its kinase activity. Expression of these EphA2 mutants in breast cancer cells resulted in decreased tumor volume and increased tumor apoptosis in primary tumors. In addition, the numbers of lung metastases were significantly reduced in both experimental and spontaneous metastasis models. Reduced tumor volume and metastasis are not due to defects in tumor angiogenesis, as there is no significant difference in tumor vessel density between wild-type tumors and tumors expressing EphA2-signaling-defective mutants. In contrast, tumor cells expressing the EphA2 mutants are defective in RhoA GTPase activation and cell migration. Taken together, these results suggest that receptor phosphorylation and kinase activity of the EphA2 receptor, at least in part, contribute to tumor malignancy.
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Affiliation(s)
- Wei Bin Fang
- Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-2363, USA
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Guo DL, Zhang J, Yuen ST, Tsui WY, Chan ASY, Ho C, Ji J, Leung SY, Chen X. Reduced expression of EphB2 that parallels invasion and metastasis in colorectal tumours. Carcinogenesis 2005; 27:454-64. [PMID: 16272170 DOI: 10.1093/carcin/bgi259] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
EphB2, a receptor tyrosine kinase regulated by the beta-catenin/Tcf4 complex, is expressed in the proliferative compartment of mouse intestine and regulates bidirectional migration of intestinal precursor cells in the crypt-villus axis through repulsive interaction with Ephrin-B ligands. Recently, it has been shown that reduction of EphB activity accelerates colon tumour progression in the Apc(Min/+) mice. In this study, we examined the expression of EphB2 in normal colon, adenomas, primary colorectal cancers (CRCs), lymph node metastases and liver metastases using immunohistochemistry on tissue microarrays. In addition, EphB2 was overexpressed in SW480 colon cancer cells to study its effect in vitro. We found that EphB2 was expressed in 100% of normal colon crypt base cells, 78% of adenomas, 55.4% of primary CRCs, 37.8% of lymph node metastases and 32.9% of liver metastases (all differences were statistically significant at P < 0.001 compared with primary CRCs). Patients with CRCs that lose EphB2 expression had more advanced tumour stage (P = 0.005), poor differentiation (P < 0.001), poor overall survival (P = 0.005) and disease-free survival (P = 0.001), with the latter being independent of tumour stage. In vitro studies showed that overexpression of EphB2 inhibited colon cancer cell growth in colony formation assay and activation of EphB2 receptor inhibited colon cancer cell adhesion and migration. Our data demonstrated a progressive loss of EphB2 expression in each critical step of colon carcinogenesis, including the onset of invasion, dedifferentiation and metastasis which are paralleled by adverse patient outcome. EphB2 may achieve its tumour suppressor function through regulation of cell survival, adhesion and migration.
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Affiliation(s)
- Dong Li Guo
- Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong
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18
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Abstract
Eph receptor tyrosine kinases mould the behaviour of many cell types by binding membrane-anchored ligands, ephrins, at sites of cell-cell contact. Eph signals affect both of the contacting cells and can produce diverse biological responses. New models explain how quantitative variations in the densities and signalling abilities of Eph receptors and ephrins could account for the different effects that are elicited on axon guidance, cell adhesion and cell migration during development, homeostasis and disease.
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Affiliation(s)
- Elena B Pasquale
- The Burnham Institute, 10901 N. Torrey Pines Road, La Jolla, California 92037, USA.
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Altick AL, Dravis C, Bowdler T, Henkemeyer M, Mastick GS. EphB receptor tyrosine kinases control morphological development of the ventral midbrain. Mech Dev 2005; 122:501-12. [PMID: 15804564 DOI: 10.1016/j.mod.2004.11.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Revised: 11/18/2004] [Accepted: 11/21/2004] [Indexed: 11/21/2022]
Abstract
EphB receptor tyrosine kinases and ephrin-B ligands regulate several types of cell-cell interactions during brain development, generally by modulating the cytoskeleton. EphB/ephrinB genes are expressed in the developing neural tube of early mouse embryos with distinct overlapping expression in the ventral midbrain. To test EphB function in midbrain development, mouse embryos compound homozygous for mutations in the EphB2 and EphB3 receptor genes were examined for early brain phenotypes. These mutants displayed a morphological defect in the ventral midbrain, specifically an expanded ventral midline evident by embryonic day E9.5-10.5, which formed an abnormal protrusion into the cephalic flexure. The affected area was comprised of cells that normally express EphB2 and ephrin-B3. A truncated EphB2 receptor caused a more severe phenotype than a null mutation, implying a dominant negative effect through interference with EphB forward (intracellular) signaling. In mutant embryos, the overall number, size, and identity of the ventral midbrain cells were unaltered. Therefore, the defect in ventral midline morphology in the EphB2;EphB3 compound mutant embryos appears to be caused by cellular changes that thin the tissue, forcing a protrusion of the ventral midline into the cephalic space. Our data suggests a role for EphB signaling in morphological organization of specific regions of the developing neural tube.
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Affiliation(s)
- Amy L Altick
- Biochemistry Graduate Program, Department of Biology, University of Nevada, Mail stop 200, Reno, NV 89557, USA
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20
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Aasheim HC, Patzke S, Hjorthaug HS, Finne EF. Characterization of a novel Eph receptor tyrosine kinase, EphA10, expressed in testis. Biochim Biophys Acta Gen Subj 2005; 1723:1-7. [PMID: 15777695 DOI: 10.1016/j.bbagen.2005.01.011] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2004] [Revised: 01/12/2005] [Accepted: 01/18/2005] [Indexed: 11/28/2022]
Abstract
In mammals, 14 members of the Eph receptor tyrosine kinase family have been described so far. Here we present a not yet described member of this family denoted EphA10. We report the identification of three putative EphA10 isoforms: one soluble and two transmembrane isoforms. One of the latter isoforms lacked the sterile alpha motif commonly found in Eph receptors. The gene encoding EphA10 is located on chromosome 1p34 and expression studies show that EphA10 mRNA is mainly expressed in testis. Binding studies to ephrin ligands suggests that this receptor belongs to the EphA subclass of Eph receptors binding mainly to ephrin-A ligands.
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21
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Miao H, Strebhardt K, Pasquale EB, Shen TL, Guan JL, Wang B. Inhibition of integrin-mediated cell adhesion but not directional cell migration requires catalytic activity of EphB3 receptor tyrosine kinase. Role of Rho family small GTPases. J Biol Chem 2004; 280:923-32. [PMID: 15536074 DOI: 10.1074/jbc.m411383200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genetic studies have shown that Eph receptor tyrosine kinases have both kinase-dependent and kinase-independent functions through incompletely understood mechanisms. We report here that ephrin-B1 stimulation of endogenous EphB kinases in LS174T colorectal epithelial cells inhibited integrin-mediated adhesion and HGF/SF-induced directional cell migration. Using 293 cells stably transfected with wild type (WT)- or kinase-deficient (KD-EphB3), we found that inhibition of integrin-mediated cell adhesion and induction of cell rounding was kinase-dependent. Unexpectedly, in two independent assays, both KD- and WT-EphB3 significantly inhibited directional cell migration. Upon ephrin-B1 stimulation, the activities of Rac1 and Cdc42 were reduced in both WT- and KD-EphB3-expressing cells that were induced to migrate. Pharmacological evidence demonstrates that a relative increase in RhoA signaling as a result of decreased Rac1/Cdc42 activities contributes to the inhibitory effects. Furthermore, EphB3-mediated inhibitory effect on cell adhesion but not migration was abolished by the integrin activating antibodies, suggesting that the inhibition of cell migration is not because of down-regulation of integrin function. These results uncover a differential requirement for EphB3 catalytic activity in the regulation of cell adhesion and migration, and suggest that while catalytic activity of EphB3 is required for inhibition of integrin-mediated cell adhesion, a distinct signaling pathway to Rho GTPases shared by WT- and KD-EphB3 receptor mediates inhibition of directional cell migration.
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Affiliation(s)
- Hui Miao
- Rammelkamp Center for Research, MetroHealth Campus, and Department of Pharmacology and Ireland Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44109, USA
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22
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Willson CA, Miranda JD, Foster RD, Onifer SM, Whittemore SR. Transection of the adult rat spinal cord upregulates EphB3 receptor and ligand expression. Cell Transplant 2004; 12:279-90. [PMID: 12797382 DOI: 10.3727/000000003108746830] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Eph receptors and ligands represent two families of proteins that control axonal guidance during development. Recent work has shown that several Eph receptors are expressed postnatally. Because the Eph molecules represent a class of axon guidance molecules that are mainly inhibitory to axonal growth, we investigated whether EphB3 expression was upregulated in both spinal cord and four supraspinal nuclei (locus coeruleus, vestibular, raphe pallidus, and red) 1 week after a complete spinal cord thoracic transection. Injured rats had a significant increase in EphB3 mRNA and protein expression in the spinal cord. The increased EphB3 expression was colocalized with GFAP staining and indicated that astrocytes play a role in EphB3 expression after spinal cord injury. No change in EphB3 expression was seen in supraspinal brain nuclei, which further demonstrated that changes in expression were due to changes in the local microenvironment at the injury site. The expression of EphB3 was colocalized to regions of the CNS that had a high level of EphB3 binding ligands. These data indicate upregulation of EphB3 expression after injury may also contribute to an environment in the spinal cord that is inhibitory to axonal regeneration.
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Affiliation(s)
- Christopher A Willson
- Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY 40202, USA
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23
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Brors D, Bodmer D, Pak K, Aletsee C, Schäfers M, Dazert S, Ryan AF. EphA4 provides repulsive signals to developing cochlear ganglion neurites mediated through ephrin-B2 and -B3. J Comp Neurol 2003; 462:90-100. [PMID: 12761826 DOI: 10.1002/cne.10707] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ephrins and Eph receptors make up two large families of bi-directional signaling molecules that are known to play a role in the development of the nervous system. Recently, expression of EphA4 in the developing cochlea was shown, with strong expression in cells lining the osseous spiral lamina (OSL) through which afferent dendrites must pass to reach the organ of Corti (OC). It was also demonstrated that ephrin-B2 and -B3, both of which are known to interact with EphA4, are expressed by spiral ganglion (SG) neurons. To investigate the functional role of EphA4 in the development of inner ear neurons, neonatal rat SG explants were cultured for 72 hours on uniformly coated surfaces or near stripes of EphA4/IgG-Fc-chimera. Control explants were cultured on or near IgG-Fc and EphA1/IgG-Fc-chimera. To assess the roles of ephrin-B2 and -B3 in EphA4 signaling, SG explants were cultured with or without anti-ephrin-B2 and/or -B3 blocking antibodies. Growth patterns of SG neurites at the border of EphA4 receptor stripes showed repulsion, characterized by turning, stopping and/or reversal. In the case of IgG-Fc and EphA1, the neurites grew straight onto the stripes. Treatment with either anti-ephrin-B2 or -B3 blocking antibodies significantly reduced the repulsive effect of an EphA4 stripe. Moreover, when both antibodies were used together, neurites crossed onto EphA4 stripes with no evidence of repulsion. The results suggest that EphA4 provides repulsive signals to SG neurites in the developing cochlea, and that ephrin-B2 and -B3 together mediate this response.
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Affiliation(s)
- Dominik Brors
- Department of Surgery, Division Otolaryngology and Neurosciences, University of California, San Diego School of Medicine and Veterans Administration Medical Center, La Jolla 92093, USA
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24
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Prevost N, Woulfe D, Tognolini M, Brass LF. Contact-dependent signaling during the late events of platelet activation. J Thromb Haemost 2003; 1:1613-27. [PMID: 12871298 DOI: 10.1046/j.1538-7836.2003.00327.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Signaling events downstream from collagen receptors and G protein-coupled receptors are responsible for the initiation and extension of platelet plug formation. This creates the platelet plug and hopefully results in the cessation of bleeding. It is not, however, all that is required for hemostasis, and growing evidence is emerging that the perpetuation of a stable hemostatic plug requires additional intracellular signaling. At least part of this process is made possible by the persistent close contacts between platelets that can only occur after the onset of aggregation. This review discusses several examples of such signaling mechanisms that help to perpetuate the platelet plug in a contact-dependent manner, including outside-in signaling through integrins, signaling though Eph kinases and ephrins, and the role of CD40L.
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Affiliation(s)
- N Prevost
- Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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25
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Sharfe N, Freywald A, Toro A, Roifman CM. Ephrin-A1 induces c-Cbl phosphorylation and EphA receptor down-regulation in T cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:6024-32. [PMID: 12794130 DOI: 10.4049/jimmunol.170.12.6024] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Eph receptor tyrosine kinases are expressed by T lineage cells, and stimulation with their ligands, the ephrins, has recently been shown to modulate T cell behavior. We show that ephrin-A1 stimulation of Jurkat T cells induces tyrosine phosphorylation of EphA3 receptors and cytoplasmic proteins, including the c-cbl proto-oncogene. Cbl phosphorylation was also observed in peripheral blood T cells. In contrast, stimulation of Jurkat cells with the EphB receptor ligand ephrin-B1 does not cause Cbl phosphorylation. EphA activation also induced Cbl association with Crk-L and Crk-II adapters, but not the related Grb2 protein. Induction of Cbl phosphorylation upon EphA activation appeared to be dependent upon Src family kinase activity, as Cbl phosphorylation was selectively abrogated by the Src family inhibitor 4-amino-5(4-chlorophenyl-7-(tert-butyl)pyrazolo[3,4-d]pyrimidine, while EphA phosphorylation was unimpaired. Ephrin-A1 stimulation of Jurkat cells was also found to cause down-regulation of endogenous EphA3 receptors from the cell surface and their degradation. In accordance with the role of Cbl as a negative regulator of receptor tyrosine kinases, overexpression of wild-type Cbl, but not its 70-Z mutant, was found to down-regulate EphA receptor expression. Receptor down-regulation could also be inhibited by blockage of Src family kinase activity. Our findings show that EphA receptors can actively signal in T cells, and that Cbl performs multiple roles in this signaling pathway, functioning to transduce signals from the receptors as well as regulating activated EphA receptor expression.
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Affiliation(s)
- Nigel Sharfe
- Immunology and Allergy, Department of Pediatrics, Research Institute, Hospital for Sick Children, and University of Toronto, Toronto, Canada
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26
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Kao HW, Chen HC, Wu CW, Lin WC. Tyrosine-kinase expression profiles in human gastric cancer cell lines and their modulations with retinoic acids. Br J Cancer 2003; 88:1058-64. [PMID: 12671705 PMCID: PMC2376380 DOI: 10.1038/sj.bjc.6600821] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2002] [Revised: 12/16/2002] [Accepted: 12/20/2002] [Indexed: 11/28/2022] Open
Abstract
Many protein tyrosine kinases are key regulators involved in cellular growth, differentiation, development, apoptosis and signal transduction pathways. Obtaining a comprehensive tyrosine-kinase expression profile in tumour cells is essential to learning more about their oncogenic potentials and responses to various chemotherapeutic reagents - such as retinoic acid, which has been shown to suppress the growth of gastric cancer cells and modulate gene expression. Expression of tyrosine kinases in retionic acid-treated cancer cells was investigated by reverse trancriptase-polymerase chain reaction (RT-PCR) and a novel restriction analysis of gene expression (RAGE) display technique. We first established comprehensive tyrosine-kinase profiles in different human gastric cancer cell lines. In cells treated with 9-cis-retinoic acid or all-trans-retinoic acid, we found that two PTKs (Eph and Hek5) appeared to be upregulated. In the present study, we demonstrate an efficient and simple RAGE approach for examining tyrosine kinases' expression in tumour cells and their alterations following drug treatments.
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Affiliation(s)
- H-W Kao
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC
| | - H-C Chen
- Taigen Biotechnology, 7F, No. 138 Shin Ming Road, Taipei 114, ROC
| | - C-W Wu
- Department of Surgery, Taipei-Veterans General Hospital, National Yang-Ming University, Taipei 112, Taiwan, ROC
| | - W-C Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC
- Institute of Biotechnology in Medicine, National Yang-Ming University, Taipei 112, Taiwan, ROC
- Graduate Institute of Basic Medical Sciences, Chang Gung University, Tao-Yuan 333, Taiwan, ROC
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27
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Walker-Daniels J, Hess AR, Hendrix MJC, Kinch MS. Differential regulation of EphA2 in normal and malignant cells. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 162:1037-42. [PMID: 12651595 PMCID: PMC1851246 DOI: 10.1016/s0002-9440(10)63899-0] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jennifer Walker-Daniels
- Department of Basic Medical Sciences, Purdue University Cancer Center, West Lafayette, Indiana, USA
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28
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Abstract
Eph receptor tyrosine kinases and their ligands, the ephrins, are known to play an important role in regulating cell migration and targeting in neuronal and endothelial cells. Recently, it has been shown that lymphoid cells also express Eph receptors, raising the possibility that Eph receptors may similarly regulate lymphocyte migration. Chemotaxis in response to soluble chemokine factors is an essential facet of T cell biology. We demonstrate here that T cell chemotaxis in response to both the stromal cell-derived factor (SDF)-1alpha and macrophage inflammatory protein 3beta chemokines is modulated by costimulation with ephrins. Both ephrin-A and ephrin-B ligands were found to modify the chemotactic responses of a T cell line and primary T cells. Ephrin-A1, in particular, strongly inhibited chemotaxis. In accordance with the tyrosine kinase activity of EphA receptors, ephrin-A1 stimulation induced rapid intracellular tyrosine phosphorylation in T cells. Although strongly inhibiting chemotaxis, ephrin-A1 costimulus did not affect many of the signaling events downstream of the SDF-1alpha receptor CXCR4, including calcium flux and activation of MAPK. Rather, ephrin-A1 altered the balance of small G protein activity in T cells. Ephrin-A1 stimulation prevented SDF-1alpha-induced activation of cdc42, while simultaneously inducing rho activation. Ultimately, ephrin-A1 was found to inhibit chemokine-induced actin polymerization, thereby blocking migration. Ubiquitous ephrin expression in vivo creates enormous potential for T cells to encounter these ligands, suggesting that Eph receptors and ephrins may be important regulators of T cell migration.
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Affiliation(s)
- Nigel Sharfe
- Division of Immunology and Allergy, Department of Pediatrics, Infection, Immunity, Injury and Repair Program, Research Institute, The Hospital for Sick Children and the University of Toronto, Toronto, Canada
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29
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Steinle JJ, Meininger CJ, Forough R, Wu G, Wu MH, Granger HJ. Eph B4 receptor signaling mediates endothelial cell migration and proliferation via the phosphatidylinositol 3-kinase pathway. J Biol Chem 2002; 277:43830-5. [PMID: 12235151 DOI: 10.1074/jbc.m207221200] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The goals of this study were 2-fold: 1) to determine whether stimulation of Eph B4 receptors promotes microvascular endothelial cell migration and/or proliferation, and 2) to elucidate signaling pathways involved in these responses. The human endothelial cells used possessed abundant Eph B4 receptors with no endogenous ephrin B2 expression. Stimulation of these receptors with ephrin B2/Fc chimera resulted in dose- and time-dependent phosphorylation of Akt. These responses were inhibited by LY294002 and ML-9, blockers of phosphatidylinositol 3-kinase (PI3K) and Akt, respectively. Eph B4 receptor activation increased proliferation by 38%, which was prevented by prior blockade with LY294002, ML-9, and inhibitors of protein kinase G (KT5823) and MEK (PD98059). Nitrite levels increased over 170% after Eph B4 stimulation, indicating increased nitric oxide production. Signaling of endothelial cell proliferation appears to be mediated by a PI3K/Akt/endothelial nitric-oxide synthase/protein kinase G/mitogen-activated protein kinase cascade. Stimulation with ephrin B2 also increased migration by 63% versus controls. This effect was inhibited by blockade with PP2 (Src inhibitor), LY294002 or ML-9 but was unaffected by the PKG and MEK blockers. Eph B4 receptor stimulation increased activation of both matrix metalloproteinase-2 and -9. The results from these studies indicate that Eph B4 stimulates migration and proliferation and may play a role in angiogenesis.
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Affiliation(s)
- Jena J Steinle
- Cardiovascular Research Institute and Department of Medical Physiology, College of Medicine, the Texas A & M University System Health Science Center, Temple 76504, USA.
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30
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Freywald A, Sharfe N, Roifman CM. The kinase-null EphB6 receptor undergoes transphosphorylation in a complex with EphB1. J Biol Chem 2002; 277:3823-8. [PMID: 11713248 DOI: 10.1074/jbc.m108011200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Uniquely for the Eph family of receptor tyrosine kinases, the EphB6 receptor is catalytically inactive due to the alteration of several critical residues in its kinase domain. This has cast doubt upon its ability to participate in cytoplasmic signaling events. We show here that despite its lack of kinase activity, EphB6 undergoes inducible tyrosine phosphorylation upon stimulation with the Eph-B receptor subfamily ligand ephrin-B1. We also demonstrate, for the first time, evidence of cross-talk between Eph receptors. Overexpression of a catalytically active member of the Eph-B subfamily, EphB1, resulted in increased EphB6 phosphorylation. EphB1-induced EphB6 phosphorylation was ligand-dependent and required the functional catalytic activity of EphB1. EphB1 not only transphosphorylated EphB6, but together they also formed a stable hetero-complex. In addition, we identify the proto-oncogene c-Cbl as an EphB6-binding protein. Although EphB6-Cbl association appeared to be constitutive, Cbl required a functional phosphotyrosine binding domain in order to bind the receptor, whereas its RING finger motif ubiquitin-transfer domain was not necessary. Our findings demonstrate that EphB6 is an actively signaling receptor that undergoes transphosphorylation upon ligand binding and that can initiate specific cytoplasmic signaling events.
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Affiliation(s)
- Andrew Freywald
- Immunology and Allergy, Department of Paediatrics, Infection, Immunity, Injury and Repair Program, Research Institute, The Hospital for Sick Children and the University of Toronto, Toronto M5G 1X8, Canada
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31
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Bearer CF. L1 cell adhesion molecule signal cascades: targets for ethanol developmental neurotoxicity. Neurotoxicology 2001; 22:625-33. [PMID: 11770884 DOI: 10.1016/s0161-813x(01)00034-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A major mechanism guiding neural development is through cell-cell and cell-matrix adhesions and signaling mediated by cell adhesion molecules (CAMs). The majority of CAMs have been grouped into three families: the cadherins, the integrins and the members of the immunoglobulin superfamily including L1. While the elucidation of new receptors and matrix components has become a frequent occurrence, the elucidation of the mechanisms by which they operate, and the function of those mechanisms in complex developmental events remains rudimentary. Members of all three families participate in differential adhesion, signal transduction and physical/mechanical effects. Each of these modes of action is a potential target for developmental neurotoxicants. In this brief review, the role of L1 in normal and abnormal neurodevelopment will be summarized. L1 is a cell surface transmembrane glycoprotein with a single copy gene on the X chromosome. There are two alternatively spliced exons, with the RSLE containing form found only on axons and growth cones of post-mitotic neurons. L1 mediates the following functions: adhesion, neurite extension, neuronal migration, and axon fasciculation. L1 is critical for normal neural development; humans with genetic defects in L1, termed corpus callosum hypoplasia, mental retardation, adducted thumbs, spasticity and hydrocephalus (CRASH) syndrome, and mice lacking expression of L1 have extensive neuropathologic and aberrant behaviors. The observation that patients with fetal alcohol syndrome share similar features to patients with CRASH has lead to the investigation of the effects of ethanol on L1. Physiologic concentrations of ethanol have been shown to inhibit L1 mediated neurite outgrowth in cerebellar granule neurons. Such inhibition may result from decreased expression, altered cell surface distribution, impaired signal transduction, or impaired interaction with the cytoskeleton. These data indicate that L1 and its associated signaling pathways are potentially targets for developmental neurotoxicants.
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Affiliation(s)
- C F Bearer
- Department of Pediatrics and Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA.
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32
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Bearer CF. Mechanisms of brain injury: L1 cell adhesion molecule as a target for ethanol-induced prenatal brain injury. Semin Pediatr Neurol 2001; 8:100-7. [PMID: 11464956 DOI: 10.1053/spen.2001.25227] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The magnitude of the problem of neurodevelopmental disorders is enormous. Frequently, the mechanism of injury is unknown. In this article, the function of one cell adhesion molecule, L1, will be reviewed. L1 is critical for proper central nervous system development. Similarities between patients with fetal alcohol syndrome and with L1 mutations suggest that the mechanism of developmental neurotoxicity of ethanol is partly due to effects on L1 cell adhesion molecule.
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Affiliation(s)
- C F Bearer
- Case Western Reserve University, Cleveland, OH, USA
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33
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Abstract
The proteoglycans are multifunctional macromolecules composed of a core polypeptide and a variable number of glycosaminoglycan chains. The structural diversity and complexities of proteoglycan expression in the developing and adult Nervous System underlies the variety of biological functions that these molecules fulfill. Thus, in the Nervous System, proteoglycans regulate the structural organisation of the extracellular matrix, modulate growth factor activities and cellular adhesive and motility events, such as cell migration and axon outgrowth. This review summarises the evidences indicating that proteoglycans have an important role as modulators of neurite outgrowth and neuronal polarity. Special emphasis will be placed on those studies that have shown that proteoglycans of certain subtypes inhibit neurite extension either during the development and/or the regeneration of the vertebrate Central Nervous System.
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Affiliation(s)
- P Bovolenta
- Departamento de Neurobiología del Desarrollo, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Dr. Arce 37, 28002, Madrid, Spain.
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34
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Mellitzer G, Xu Q, Wilkinson DG. Control of cell behaviour by signalling through Eph receptors and ephrins. Curr Opin Neurobiol 2000; 10:400-8. [PMID: 10851175 DOI: 10.1016/s0959-4388(00)00095-7] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Eph receptor tyrosine kinases and ephrins mediate contact-dependent cell interactions that regulate the repulsion and adhesion mechanisms involved in the guidance and assembly of cells. Recent work has revealed a role of overlapping Eph receptor and ephrin expression in modulating neuronal growth cone repulsion, and has shown that bidirectional activation restricts intermingling and communication between cell populations. In addition, progress has been made in understanding how Eph receptors and ephrins control cell adhesion.
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Affiliation(s)
- G Mellitzer
- Division of Developmental Neurobiology, National Institute for Medical Research, Mill Hill, NW7 1AA, UK
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35
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Wilson MT, Kisaalita WS, Keith CH. Glutamate-induced changes in the pattern of hippocampal dendrite outgrowth: a role for calcium-dependent pathways and the microtubule cytoskeleton. JOURNAL OF NEUROBIOLOGY 2000; 43:159-72. [PMID: 10770845 DOI: 10.1002/(sici)1097-4695(200005)43:2<159::aid-neu6>3.0.co;2-n] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Glutamate regulation of a variety of aspects of dendrite development may be involved in neuronal plasticity and neuropathology. In this study, we examine the calcium-dependent pathways and alterations in the microtubule (MT) cytoskeleton that may mediate glutamate-induced changes in the pattern of dendrite outgrowth. We used Fura-2 AM and inhibitors of the calcium-dependent proteins, calmodulin and calpain, to identify the role of specific calcium-dependent pathways in glutamate-regulated dendrite outgrowth. Additionally, we used a quantitative fluorescence technique to correlate changes in MT levels with glutamate-induced changes in dendrite outgrowth. We show that the intracellular calcium concentration ([Ca(2+)](i)) changes in a biphasic manner over a 12-h period in the presence of glutamate. A transient increase in [Ca(2+)](i) over the first hour of glutamate exposure correlated with a calmodulin-associated increase in the rate of dendrite outgrowth, whereas a sustained increase in [Ca(2+)](i) was correlated with calpain-associated dendrite retraction. Quantitative fluorescence measurements showed no net change in the level of MTs during calmodulin-associated increases in dendrite outgrowth, but showed a significant decline in the level of MTs during calpain-associated dendrite retraction. These findings provide insights into the intracellular mechanisms involved in activity-dependent regulation of dendrite morphology during development and after pathology.
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Affiliation(s)
- M T Wilson
- BD Transduction Laboratories, Lexington, Kentucky 40503, USA
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36
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Wilkinson DG. Eph receptors and ephrins: regulators of guidance and assembly. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 196:177-244. [PMID: 10730216 DOI: 10.1016/s0074-7696(00)96005-4] [Citation(s) in RCA: 162] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent advances have started to elucidate the developmental functions and biochemistry of Eph receptor tyrosine kinases and their membrane-bound ligands, ephrins. Interactions between these molecules are promiscuous, but they largely fall into two groups: EphA receptors bind to GPI-anchored ephrin-A ligands, while EphB receptors bind to ephrin-B proteins that have a transmembrane and cytoplasmic domain. Remarkably, ephrin-B proteins transduce signals, such that bidirectional signaling can occur upon interaction with Eph receptor. In many tissues, specific Eph receptors and ephrins have complementary domains, whereas other family members may overlap in their expression. An important role of Eph receptors and ephrins is to mediate cell-contact-dependent repulsion. Complementary and overlapping gradients of expression underlie establishment of a topographic map of neuronal projections in the retinotectal system. Eph receptors and ephrins also act at boundaries to channel neuronal growth cones along specific pathways, restrict the migration of neural crest cells, and via bidirectional signaling prevent intermingling between hindbrain segments. Intriguingly, Eph receptors and ephrins can also trigger an adhesive response of endothelial cells and are required for the remodeling of blood vessels. Biochemical studies suggest that the extent of multimerization of Eph receptors modulates the cellular response and that the actin cytoskeleton is one major target of the intracellular pathways activated by Eph receptors. Eph receptors and ephrins have thus emerged as key regulators of the repulsion and adhesion of cells that underlie the establishment, maintenance, and remodeling of patterns of cellular organization.
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Affiliation(s)
- D G Wilkinson
- Division of Developmental Neurobiology, National Institute for Medical Research, London, United Kingdom
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37
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Zisch AH, Pazzagli C, Freeman AL, Schneller M, Hadman M, Smith JW, Ruoslahti E, Pasquale EB. Replacing two conserved tyrosines of the EphB2 receptor with glutamic acid prevents binding of SH2 domains without abrogating kinase activity and biological responses. Oncogene 2000; 19:177-87. [PMID: 10644995 DOI: 10.1038/sj.onc.1203304] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Eph receptor tyrosine kinases play key roles in pattern formation during embryonic development, but little is known about the mechanisms by which they elicit specific biological responses in cells. Here, we investigate the role of tyrosines 605 and 611 in the juxtamembrane region of EphB2, because they are conserved Eph receptor autophosphorylation sites and demonstrated binding sites for the SH2 domains of multiple signaling proteins. Mutation of tyrosines 605 and 611 to phenylalanine impaired EphB2 kinase activity, complicating analysis of their function as SH2 domain binding sites and their contribution to EphB2-mediated signaling. In contrast, mutation to the negatively charged glutamic acid disrupted SH2 domain binding without reducing EphB2 kinase activity. By using a panel of EphB2 mutants, we found that kinase activity is required for the changes in cell-matrix and cell - cell adhesion, cytoskeletal organization, and activation of mitogen-activated protein (MAP) kinases elicited by EphB2 in transiently transfected cells. Instead, the two juxtamembrane SH2 domain binding sites were dispensable for these effects. These results suggest that phosphorylation of tyrosines 605 and 611 is critical for EphB2-mediated cellular responses because it regulates EphB2 kinase activity.
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Affiliation(s)
- A H Zisch
- The Burnham Institute, 10901 N. Torrey Pines Road, La Jolla, California, CA 92037, USA
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38
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Chong LD, Park EK, Latimer E, Friesel R, Daar IO. Fibroblast growth factor receptor-mediated rescue of x-ephrin B1-induced cell dissociation in Xenopus embryos. Mol Cell Biol 2000; 20:724-34. [PMID: 10611251 PMCID: PMC85187 DOI: 10.1128/mcb.20.2.724-734.2000] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/1999] [Accepted: 10/14/1999] [Indexed: 11/20/2022] Open
Abstract
The Eph family of receptor tyrosine kinases and their membrane-bound ligands, the ephrins, have been implicated in regulating cell adhesion and migration during development by mediating cell-to-cell signaling events. Genetic evidence suggests that ephrins may transduce signals and become tyrosine phosphorylated during embryogenesis. However, the induction and functional significance of ephrin phosphorylation is not yet clear. Here, we report that when we used ectopically expressed proteins, we found that an activated fibroblast growth factor (FGF) receptor associated with and induced the phosphorylation of ephrin B1 on tyrosine. Moreover, this phosphorylation reduced the ability of overexpressed ephrin B1 to reduce cell adhesion. In addition, we identified a region in the cytoplasmic tail of ephrin B1 that is critical for interaction with the FGF receptor; we also report FGF-induced phosphorylation of ephrins in a neural tissue. This is the first demonstration of communication between the FGF receptor family and the Eph ligand family and implicates cross talk between these two cell surface molecules in regulating cell adhesion.
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Affiliation(s)
- L D Chong
- Basic Research Laboratory, National Cancer Institute, Frederick, Maryland 21702, USA
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39
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Helbling PM, Saulnier DM, Robinson V, Christiansen JH, Wilkinson DG, Brändli AW. Comparative analysis of embryonic gene expression defines potential interaction sites for Xenopus EphB4 receptors with ephrin-B ligands. Dev Dyn 1999; 216:361-73. [PMID: 10633856 DOI: 10.1002/(sici)1097-0177(199912)216:4/5<361::aid-dvdy5>3.0.co;2-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Eph family of receptor tyrosine kinases and their ligands, the ephrins, act as signaling molecules regulating the migratory behavior of neurons and neural crest cells, and are implicated in tissue patterning, blood vessel formation, and tumorigenesis. On the basis of structural similarities and overlapping binding specificities, Eph receptors as well as their ligands can be divided into A and B subfamilies with orthologues found in all vertebrates. We describe here the isolation of cDNAs encoding Xenopus EphB4 receptors and show that embryonic expression is prominently associated with the developing vasculature, newly forming somites, the visceral arches, and non-neuronal tissues of the embryonic head. In a screen to identify potential ligands for EphB4 in Xenopus embryos, we isolated cDNAs for the Xenopus ephrin-B2 and -B3, which demonstrates that the Xenopus genome harbors genes encoding orthologues to all three currently known mammalian ephrin-B genes. We next performed in situ hybridizations to identify tissues and organs where EphB4 receptors may encounter ephrin-B ligands during embryonic development. Our analysis revealed distinct, but overlapping patterns of ephrin-B gene expression. Interestingly, each ephrin-B ligand displayed expression domains either adjacent to or within EphB4-expressing tissues. These findings indicate that EphB4 receptors may interact in vivo with multiple B-class ephrins. The expression patterns also suggest that EphB4 receptors and their ligands may be involved in visceral arch formation, somitogenesis, and blood vessel development.
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Affiliation(s)
- P M Helbling
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, Zürich, Switzerland
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40
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Rogers JH, Ciossek T, Menzel P, Pasquale EB. Eph receptors and ephrins demarcate cerebellar lobules before and during their formation. Mech Dev 1999; 87:119-28. [PMID: 10495276 DOI: 10.1016/s0925-4773(99)00154-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The formation of the ten cerebellar lobules is an unsolved problem in brain development. We report a screen for the four subfamilies of Eph receptors and their ligands (ephrins) in developing mouse cerebellum, using soluble receptor-immunoglobulin and ligand-immunoglobulin fusion proteins, and antibodies against EphA and ephrin-B proteins. Our results identify Eph receptors and ephrins as the first molecules known to demarcate individual lobules during development. Staining for ephrin-A ligands is in lobule VIII as it forms, across the whole width of the cerebellum. Staining for three EphA receptors approximately coincides with presumptive lobules VI and/or VII before and just after birth, whereas a fourth EphA receptor (EphA4, which binds ligands of both subfamilies) has more widespread expression. Staining for EphB receptors is in lobules VII, VIII, and IX. Staining for ephrin-B ligands is much weaker, becomes detectable only after birth, and does not appear to be lobule-specific. Staining for all subfamilies spreads to at least some adjacent lobules as maturation proceeds. The lobule-specific patterns appear before the lobules form, and initially extend across the width of the cerebellum, in spite of the lesser conservation of the lateral extensions of the lobules. These expression patterns define previously unknown developmental units and suggest that Eph family proteins may contribute to cerebellar morphogenesis.
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Affiliation(s)
- J H Rogers
- Department of Physiology, University of Cambridge, Downing St., Cambridge, UK.
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41
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Abstract
The striatum integrates limbic and neocortical inputs to regulate sensorimotor and psychomotor behaviors. This function is dependent on the segregation of striatal projection neurons into anatomical and functional components, such as the striosome and matrix compartments. In the present study the association of ephrin-A cell surface ligands and EphA receptor tyrosine kinases (RTKs) with the organization of these compartments was determined in postnatal rats. Ephrin-A1 and ephrin-A4 selectively bind to EphA receptors on neurons restricted to the matrix compartment. Binding is absent from the striosomes, which were identified by mu-opioid receptor immunostaining. In contrast, ephrin-A2, ephrin-A3, and ephrin-A5 exhibit a different mosaic binding pattern that appears to define a subset of matrix neurons. In situ hybridization for EphA RTKs reveals that the two different ligand binding patterns strictly match the mRNA expression patterns of EphA4 and EphA7. Ligand-receptor binding assays indicate that ephrin-A1 and ephrin-A4 selectively bind EphA4 but not EphA7 in the lysates of striatal tissue. Conversely, ephrin-A2, ephrin-A3, and ephrin-A5 bind EphA7 but not EphA4. These observations implicate selective interactions between ephrin-A molecules and EphA RTKs as potential mechanisms for regulating the compartmental organization of the striatum.
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42
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Abstract
Growth cones, the hand-like structures at the tip of growing neurites, possess remarkable abilities to detect directional cues. On their way to their targets they traverse a dense jungle of many different cells, expressing a variety of different molecular guidance cues. Proper reading and integration of these cues is essential for precise wiring of different parts of the peripheral and central nervous systems. Guidance cues have been classified according to the response they elicit as either attractive or repulsive. Recent work, however, suggests that this might not represent an absolute distinction and that the internal state of the growth cone can dictate whether it detects a cue as repulsive or attractive. This article reviews some new experimental approaches to understanding growth cone signal transduction mechanisms induced by extracellular guidance cues.
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Affiliation(s)
- B K Mueller
- Max-Planck-Institute for Developmental Biology I, Tuebingen, Germany.
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43
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Ledig MM, McKinnell IW, Mrsic-Flogel T, Wang J, Alvares C, Mason I, Bixby JL, Mueller BK, Stoker AW. Expression of receptor tyrosine phosphatases during development of the retinotectal projection of the chick. JOURNAL OF NEUROBIOLOGY 1999; 39:81-96. [PMID: 10213455 DOI: 10.1002/(sici)1097-4695(199904)39:1<81::aid-neu7>3.0.co;2-k] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Receptor tyrosine kinases and receptor protein tyrosine phosphatases (RPTPs) appear to coordinate many aspects of neural development, including axon growth and guidance. Here, we focus on the possible roles of RPTPs in the developing avian retinotectal system. Using both in situ hybridization analysis and immunohistochemistry, we show for the first time that five RPTP genes--CRYPalpha, CRYP-2, PTPmu, PTPgamma, and PTPalpha--have different but overlapping expression patterns throughout the retina and the tectum. PTPalpha is restricted to Muller glia cells and radial glia of the tectum, indicating a possible function in controlling neuronal migration. PTPgamma expression is restricted to amacrine neurons. CRYPalpha and CRYP-2 mRNAs in contrast are expressed throughout the retinal ganglion cell layer from where axons grow out to their tectal targets. PTPmu is expressed in a subset of these ganglion cells. CRYPalpha, CRYP-2, and PTPmu proteins are also localized in growth cones of retinal ganglion cell axons and are present in defined laminae of the tectum. Thus, the spatial and temporal expression of three distinct RPTP subtypes--CRYPalpha, CRYP-2, and PTPmu--are consistent with the possibility of their involvement in axon growth and guidance of the retinotectal projection.
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Affiliation(s)
- M M Ledig
- Max-Planck-Institut für Entwicklungsbiologie Abt. I, Tübingen, Germany
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44
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Gao PP, Yue Y, Cerretti DP, Dreyfus C, Zhou R. Ephrin-dependent growth and pruning of hippocampal axons. Proc Natl Acad Sci U S A 1999; 96:4073-7. [PMID: 10097165 PMCID: PMC22422 DOI: 10.1073/pnas.96.7.4073] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Neuronal connections are arranged topographically such that the spatial organization of neurons is preserved by their termini in the targets. During the development of topographic projections, axons initially explore areas much wider than the final targets, and mistargeted axons are pruned later. The molecules regulating these processes are not known. We report here that the ligands of the Eph family tyrosine kinase receptors may regulate both the initial outgrowth and the subsequent pruning of axons. In the presence of ephrins, the outgrowth and branching of the receptor-positive hippocampal axons are enhanced. However, these axons are induced later to degenerate. These observations suggest that the ephrins and their receptors may regulate topographic map formation by stimulating axonal arborization and by pruning mistargeted axons.
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Affiliation(s)
- P P Gao
- Laboratory for Cancer Research, Department of Chemical Biology, College of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA
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45
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Helbling PM, Tran CT, Brändli AW. Requirement for EphA receptor signaling in the segregation of Xenopus third and fourth arch neural crest cells. Mech Dev 1998; 78:63-79. [PMID: 9858686 DOI: 10.1016/s0925-4773(98)00148-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We describe here the isolation of a full-length cDNA encoding a Xenopus orthologue of the mammalian EphA2 receptor tyrosine kinase and investigate its role in cranial neural crest migration. We show that the primary sites of Xenopus EphA2 expression are rhombomere 4 of the developing hindbrain, migratory cranial neural crest cells and mesoderm of the visceral arches. To interfere with EphA2 and related receptors during cranial neural crest migration, we took a dominant negative approach. Overexpression of kinase-deficient EphA2 receptor variants led to abnormal migration of cranial neural crest cells. Neural crest cells of the third arch were found to mismigrate posteriorly, resulting in the failure of third and fourth arch neural crest to separate into distinct streams. These defects could be rescued by expression of full-length EphA2 receptors. A comparison of the expression domains of EphA2-binding proteins mapped by receptor affinity probe (RAP) in situ staining with those for EphA2 receptors revealed co-expression of ligands and receptors in the visceral arch mesenchyme. Taken together, these results suggest that EphA receptors may mediate attractive or adhesive signals during migration of cranial neural crest cells.
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Affiliation(s)
- P M Helbling
- Institute of Cell Biology, Swiss Federal Institute of Technology, ETH-Hönggerberg, CH-8093, Zürich, Switzerland
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