Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Molecular gradients have been postulated to control the topographic mapping of retinal axons in their central targets. Based initially on their expression patterns, and more recently on functional studies, members of the EphA subfamily of receptor tyrosine kinases and their ephrin-A ligands have been implicated in the guidance of retinal axons along the anterior-posterior axis of the chick optic tectum. The report that a receptor of the EphB subfamily, EphB2/Cek5/Nuk/Sek3, is expressed in a high ventral to low dorsal gradient in the developing chick retina and is present on ganglion cell axons suggests that it may be involved in the mapping of retinal axons along the corresponding dorsal-ventral axis of the tectum. To address this issue, we have determined the expression and distribution of ephrin-B1/LERK-2/Cek5-L and ephrin-B2/LERK-5/Htk-L/ELF-2, ligands for EphB2, in the developing chick retinotectal system using riboprobes, immunocytochemistry, and receptor affinity probes. Both ephrin-B1 and ephrin-B2 transcripts are expressed in a high dorsal to low ventral gradient in the developing retina, complementary to the distribution of EphB2. Ephrin-B1 and ephrin-B2 proteins are predominantly found in the developing plexiform layers, suggesting a role in the development of intraretinal connections. Neither protein is detected on ganglion cell axons. In tectum, ephrin-B1 transcripts are expressed in a high dorsal to low ventral gradient in the neuroepithelium and the protein is present along the processes of radial glia and is concentrated at their endfeet in the stratum opticum, at the time retinal axons are growing through it. This distribution of ephrin-B1 suggests that it influences retinal axon mapping along the dorsal-ventral tectal axis and may also be involved in intratectal development. In contrast, ephrin-B2 transcripts and protein are localized to the deeper retinorecipient laminae in the tectum at the time retinal axons begin to arborize in them, suggesting that this ligand may influence the laminar patterning of retinal axon terminations.
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PMID:Graded and lamina-specific distributions of ligands of EphB receptor tyrosine kinases in the developing retinotectal system. 935 68

Eph family receptor tyrosine kinases (including EphA3, EphB4) direct pathfinding of neurons within migratory fields of cells expressing gradients of their membrane-bound ligands. Others (EphB1 and EphA2) direct vascular network assembly, affecting endothelial migration, capillary morphogenesis, and angiogenesis. To explore how ephrins could provide positional labels for cell targeting, we tested whether endogenous endothelial and P19 cell EphB1 (ELK) and EphB2 (Nuk) receptors discriminate between different oligomeric forms of an ephrin-B1/Fc fusion ligand. Receptor tyrosine phosphorylation was stimulated by both dimeric and clustered multimeric ephrin-B1, yet only ephrin-B1 multimers (tetramers) promoted endothelial capillary-like assembly, cell attachment, and the recruitment of low-molecular-weight phosphotyrosine phosphatase (LMW-PTP) to receptor complexes. Cell-cell contact among cells expressing both EphB1 and ephrin-B1 was required for EphB1 activation and recruitment of LMW-PTP to EphB1 complexes. The EphB1-binding site for LMW-PTP was mapped and shown to be required for tetrameric ephrin-B1 to recruit LMW-PTP and to promote attachment. Thus, distinct EphB1-signaling complexes are assembled and different cellular attachment responses are determined by a receptor switch mechanism responsive to distinct ephrin-B1 oligomers.
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PMID:Eph receptors discriminate specific ligand oligomers to determine alternative signaling complexes, attachment, and assembly responses. 949 2

The EPH family is the largest subfamily of receptor protein tyrosine kinases, consisting of the EPHA and EPHB subgroups. Ephrin-B1, ephrin-B2, and ephrin-B3 are ligands of the EPHB subgroup and are encoded by the EFNB1, EFNB2, and EFNB3 genes, respectively. We have shown previously that EPHB2 transcripts are expressed in six small cell lung carcinoma (SCLC) cell lines. In this study, we examined the expression of EPHB1, EPHB2, EPHB3, EPHB4, and EPHB6 in 4 SCLC tumor specimens and 14 cell lines including 3 cell lines derived from these tumor specimens. To investigate whether potential autocrine loops of EPHB receptors and ephrin-B ligands exist in SCLC, the expression of EFNB1, EFNB2, and EFNB3 was also examined. Our data show that transcripts encoding multiple members of the EPHB subgroup and the ephrin-B subgroup are coexpressed in SCLC cell lines and tumors. These results suggest that the EPHB subgroup receptor kinases may modulate the biological behavior of SCLC through autocrine and/or juxtacrine activation by ephrin-B ligands that are expressed in the same or neighboring cells.
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PMID:Coexpression of transcripts encoding EPHB receptor protein tyrosine kinases and their ephrin-B ligands in human small cell lung carcinoma. 1003 97

The Eph receptors are the largest known family of receptor protein tyrosine kinases, which play important roles with their ligands called ephrin in the neural development, angiogenesis, and vascular network assembly. It was previously shown that ephrin-A2, -A3 and -A5 bind to, and activate the EphA8 receptor tyrosine kinase, respectively. In this study, we have examined if there are other additional ephrin ligands interacting with the EphA8 receptor tyrosine kinase expressed in NIH3T3 fibroblasts. For this purpose, we have constructed chimeric ephrin-A1, -A4, -B1, -B2 or -B3 ligands consisting of the Fc portion of human IgG fused to their carboxyl-terminus. Both ephrin-A1 and ephrin-A4 chimeric ligands efficiently bound to the EphA8 receptor expressed in NIH3T3 fibroblasts, whereas the transmembrane ligands including ephrin-B1, -B2 and -B3 did not. Additionally we have demonstrated that both the EphA8-TrkB chimeric receptor and the EphA8 receptor expressed in NIH3T3 fibroblasts are efficiently tyrosine-phosphorylated upon stimulating with epthin-A1 or -A4 but none of transmembrane ephrin-B proteins. These results strongly indicate that the EphA8 receptor functions exclusively as an glycosyl phosphatidylinositol (GPI)-linked ephrin ligand-dependent receptor protein tyrosine kinase.
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PMID:Characterization of ephrin-A1 and ephrin-A4 as ligands for the EphA8 receptor protein tyrosine kinase. 1051 10

Upregulation of the p53 tumor suppressor protein by infection with a recombinant p53 adenovirus resulted in extensive apoptosis in ECV-304 cells and the eventual death of almost all the cells. To establish a system to elucidate the molecular mechanisms involved in p53-mediated apoptosis of these cells, we established a variant of ECV-304 that is resistant to p53-induced apoptosis by repeated infections with a recombinant p53 adenovirus. We have designated this variant as the DECV cell line (Differentiated ECV-304). DECV cells expressed similar amounts of nuclear-localized p53 as ECV-304 cells when infected with recombinant p53 adenovirus, but in contrast to ECV-304 cells, greater than 95% of DECV cells survived and remained viable after 24 hours of infection. In further contrast to ECV-304 cells, DECV cells grew less efficiently in soft agar and exhibited contact inhibition in growth assays. Moreover, DECV cells formed unusual lattice or cyst-like structures in culture and formed lumenal structures indicative of epithelial differentiation in three-dimensional collagen matrices, while parental ECV-304 cells showed minimal evidence of these cellular behaviors. A comparative molecular analysis of gene expression in DECV and ECV-304 cells was conducted by cDNA microarray technology. Protocadherin-1 was found to be expressed in DECV cells but not in ECV-304 cells, while the Id-3 gene was observed expressed in ECV-304 cells but not in DECV cells. Moreover, upregulated expression of p53 in ECV-304 cells induced the EPHB2 (Ephrin) receptor tyrosine kinase and the ephrin-B1 ligand mRNAs compared to DECV cells treated in the same manner. These data demonstrate that a new variant of the ECV-304 cell line, which is resistant to p53-mediated apoptosis, exhibits differential gene expression as well as distinct cell behaviors as compared to the parental ECV-304 cell line. DECV cells should prove to be a useful tool in future studies to elucidate mechanisms of p53-mediated apoptosis and differentiation.
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PMID:Biological and molecular characterization of an ECV-304-derived cell line resistant to p53-mediated apoptosis. 1122 49

Nucleus magnocellularis (NM) in the avian auditory brainstem receives auditory input from nerve the VIIIth and projects bilaterally to nucleus laminaris (NL). This projection preserves binaural segregation in that ipsilateral NM projects to dorsal dendrites of NL and contralateral NM projects to ventral dendrites of NL. We have begun to examine the molecular signals that influence segregation of inputs onto discrete regions of NL cells. We previously showed that the Eph receptor, EphA4, is expressed selectively in the dorsal NL neuropil from embryonic day (E) 9 to E11, when NM axons grow into the NL neuropil. This asymmetric distribution suggests that EphA4 acts as a guidance molecule during binaural segregation. We report here on the developmental changes in the expression of two other Eph receptors, EphB2 and EphB5, and two ligands, ephrin-B1 and ephrin-B2, in the chick auditory brainstem. These proteins are expressed in the auditory nuclei during the maturation of the NM-NL projection. EphB2, EphB5, and ephrin-B1 are expressed in dorsal and ventral NL neuropil and at the midline of the brainstem at E10-E12. At this age, ephrin-B2, a ligand for EphB receptors and for EphA4, is expressed in NL cell bodies and NM-NL axons. The expression of these proteins diminishs in the posthatch ages examined. These results suggest that several members of the Eph family are involved in maturation of the nuclei and their projections. Moreover, ephrin-B2 in growing axons may interact with the asymmetrically expressed EphA4 during the establishment of binaural segregation.
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PMID:Expression of EphB receptors and EphrinB ligands in the developing chick auditory brainstem. 1220 9

The cochleovestibular ganglion of the chick differentiates at early embryonic stages as VIIIth nerve axons enter the brainstem. The tonotopic organization of the auditory portion of the VIIIth nerve can be discerned at the time axons initially reach their brainstem targets. The mechanisms underlying this early organization are not known. Eph receptor tyrosine kinases and their ligands, the ephrins, have a demonstrated role in guiding axons to topographically appropriate locations in other areas of the nervous system. In order to begin to test whether Eph proteins have a similar role in the auditory system, we investigated the tonotopic expression of several Eph receptors and ephrins in the VIIIth nerve during embryonic ages corresponding to the initial innervation of the auditory brainstem. Expression patterns of EphA4, EphB2, EphB5, ephrin-A2, and ephrin-B1 were evaluated immunohistochemically at embryonic days 4 through 10. Protein expression was observed in the cochlear ganglion and VIIIth nerve axons at these ages. EphB5, ephrin-A2, and ephrin-B1 were expressed throughout the nerve. EphA4 and EphB2 had complementary expression patterns within the nerve, with EphA4 expression higher in the dorsolateral part of the nerve and EphB2 expression higher in the ventromedial part of the nerve. These regions may correspond to auditory and vestibular components, respectively. Moreover, EphA4 expression was higher toward the low-frequency region of both the centrally and peripherally projecting branches of cochlear ganglion cells. Regional variation of Eph protein expression may influence the target selection and topography of developing VIIIth nerve projections.
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PMID:Differential expression of Eph receptors and ephrins in the cochlear ganglion and eighth cranial nerve of the chick embryo. 1566 77

The interaction of the Eph family of receptor protein tyrosine kinase and its ligand ephrin family induces bidirectional signaling via the cell-cell contacts. Although most previous studies have focused on the function of Eph-ephrin pathways in the neural system and endothelial cells, this process also occurs in epithelial and cancer cells, of which the biological involvement is poorly understood. We show that ephrin-B1 creates an in vivo complex with adjacent claudin1 or claudin4 via the extracellular domains of these proteins. The cytoplasmic domain of ephrin-B1 was phosphorylated on tyrosine residues upon the formation of cell-cell contacts, possibly recognizing an intercellular adhesion of claudins. Phosphorylation of ephrin-B1 induced by claudins was abolished by the treatment with 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, an inhibitor of the Src family kinases. Moreover, overexpression of ephrin-B1 triggered consequent change in the level of cell-cell adhesion depending on its phosphorylation. These results suggest that ephrin-B1 mediated the cell-cell adhesion of epithelial and cancer cells via a novel Eph receptor-independent mechanism.
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PMID:Phosphorylation of ephrin-B1 via the interaction with claudin following cell-cell contact formation. 1621 Oct 11

The mammalian skull vault is constructed principally from five bones: the paired frontals and parietals, and the unpaired interparietal. These bones abut at sutures, where most growth of the skull vault takes place. Sutural growth involves maintenance of a population of proliferating osteoprogenitor cells which differentiate into bone matrix-secreting osteoblasts. Sustained function of the sutures as growth centres is essential for continuous expansion of the skull vault to accommodate the growing brain. Craniosynostosis, the premature fusion of the cranial sutures, occurs in 1 in 2500 children and often presents challenging clinical problems. Until a dozen years ago, little was known about the causes of craniosynostosis but the discovery of mutations in the MSX2, FGFR1, FGFR2, FGFR3, TWIST1 and EFNB1 genes in both syndromic and non-syndromic cases has led to considerable insights into the aetiology, classification and developmental pathology of these disorders. Investigations of the biological roles of these genes in cranial development and growth have been carried out in normal and mutant mice, elucidating their individual and interdependent roles in normal sutures and in sutures undergoing synostosis. Mouse studies have also revealed a significant correspondence between the neural crest-mesoderm boundary in the early embryonic head and the position of cranial sutures, suggesting roles for tissue interaction in suture formation, including initiation of the signalling system that characterizes the functionally active suture.
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PMID:Growth of the normal skull vault and its alteration in craniosynostosis: insights from human genetics and experimental studies. 1631 97

EFNA1, EFNA2, EFNA3, EFNA4, EFNA5, EFNB1, EFNB2 and EFNB3 are EFN family ligands for EPH family receptors. EFN/EPH signaling pathway networks with the WNT signaling pathway during embryogenesis, tissue regeneration, and carcinogenesis. Comparative genomics analyses on EFNB1, EFNB2 and EFNB3 were performed by using bioinformatics and human intelligence (humint). EFNB1 mRNA was expressed in human embryonic stem (ES) cells, neural tissues, diffuse type gastric cancer, pancreatic cancer, colon cancer, brain tumors and esophageal cancer, EFNB2 mRNA in human ES cells, neural tissues and colon cancer, EFNB3 mRNA in human ES cells, neural tissues, brain tumors, pancreatic cancer and colon cancer. Because triple TCF/LEF-binding sites were identified within the 5'-promoter region of human EFNB3 gene, comparative genomics analyses on EFNB3 orthologs were further performed. Chimpanzee EFNB3 gene, consisting of five exons, was identified within AC164921.3 genome sequence. AY421228.1 was not a correct coding sequence for chimpanzee EFNB3. Chimpanzee EFNB3 gene was found to encode a 340-amino-acid protein showing 99.4% and 96.6% total-amino-acid identity with human EFNB3 and mouse Efnb3, respectively. Three TCF/LEF-binding sites within human EFNB3 promoter were conserved in chimpanzee EFNB3 promoter, and the second TCF/LEF-binding site in rodent Efnb3 promoters. CpG hypermethylation of EFNB3 promoter with 63.2% GC content as well as deletion of EFNB3 gene closely linked to TP53 tumor suppressor gene at human chromosome 17p13.1 should be investigated to elucidate the mechanism of infrequent EFNB3 upregulation in human colorectal cancer. EFNB3, identified as potential transcriptional target of WNT/beta-catenin signaling pathway, is a pharmacogenomics target in the fields of regenerative medicine and oncology.
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PMID:Comparative integromics on Ephrin family. 1659 16


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