Receptor, EphB4
Receptor, EphB2
Receptor, EphB1
Ephrin-B2
Ephrin-B1
Receptor, EphB3
Receptor, EphB6
Receptors, Eph Family
Receptor, EphB5
Ephrin-B3
Ephrins
Coexpression of transcripts encoding EPHB receptor protein tyrosine kinases and their ephrin-B ligands in human small cell lung carcinoma. (1/154)
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. (+info)Solution structure of a conserved C-terminal domain of p73 with structural homology to the SAM domain. (2/154)
p73 and p63 are two recently cloned genes with homology to the tumor suppressor p53, whose protein product is a key transcriptional regulator of genes involved in cell cycle arrest and apoptosis. While all three proteins share conserved transcriptional activation, DNA-binding and oligomerization domains, p73 and p63 have an additional conserved C-terminal region. We have determined the three-dimensional solution structure of this conserved C-terminal domain of human p73. The structure reveals a small five-helix bundle with striking similarity to the SAM (sterile alpha motif) domains of two ephrin receptor tyrosine kinases. The SAM domain is a putative protein-protein interaction domain found in a variety of cytoplasmic signaling proteins and has been shown to form both homo- and hetero-oligomers. However, the SAM-like C-terminal domains of p73 and p63 are monomeric and do not interact with one another, suggesting that this domain may interact with additional, as yet uncharacterized proteins in a signaling and/or regulatory role. (+info)Symmetrical mutant phenotypes of the receptor EphB4 and its specific transmembrane ligand ephrin-B2 in cardiovascular development. (3/154)
Ephrin-B2 is a transmembrane ligand that is specifically expressed on arteries but not veins and that is essential for cardiovascular development. However, ephrin-B2 is also expressed in nonvascular tissues and interacts with multiple EphB class receptors expressed in both endothelial and nonendothelial cell types. Thus, the identity of the relevant receptor for ephrin-B2 and the site(s) where these molecules interact to control angiogenesis were not clear. Here we show that EphB4, a specific receptor for ephrin-B2, is exclusively expressed by vascular endothelial cells in embryos and is preferentially expressed on veins. A targeted mutation in EphB4 essentially phenocopies the mutation in ephrin-B2. These data indicate that ephrin-B2-EphB4 interactions are intrinsically required in vascular endothelial cells and are consistent with the idea that they mediate bidirectional signaling essential for angiogenesis. (+info)alphaPIX nucleotide exchange factor is activated by interaction with phosphatidylinositol 3-kinase. (4/154)
p21-activated kinase (PAK) is a common effector protein of the small GTPases Cdc42 and Rac, leading to the activation of downstream mitogen activated protein kinases. PAK also mediates polarized cytoskeletal changes induced by these GTPases. The recently identified PAK-interacting exchange factor (PIX) acts as a guanine nucleotide exchange factor on Rac, and colocalizes with PAK in a focal complex, but little is known about the associated signaling cascades, including upstream activators of PIX. In this study, we show that one of the isoforms of PIX, alphaPIX, is activated by signaling cascades from the platelet-derived growth factor (PDGF) receptor and EphB2 receptor, and from integrin-induced signaling through phosphatidylinositol 3-kinase (PI3-kinase). alphaPIX is activated by forming a complex with these receptors either via association with PAK and Nck, or direct association with the p85 regulatory subunit of PI3-kinase. Synthetic phosphoinositide and membrane targeted PI3-kinase augmented the alphaPIX activity in vivo. In Xenopus, aggregates of mesodermal cells derived from embryos microinjected with alphaPIX significantly increased the peripheral spreading on fibronectin substrate in response to PDGF through PI3-kinase. These results indicate that alphaPIX is activated by PI3-kinase, and is involved in the receptor mediated signaling leading to the activation of the kinase activity of PAK, and the migration of mesodermal cells on extracellular matrix. (+info)A novel signaling intermediate, SHEP1, directly couples Eph receptors to R-Ras and Rap1A. (5/154)
The Eph family of receptor tyrosine kinases has been implicated in many developmental patterning processes, including cell segregation, cell migration, and axon guidance. The cellular components involved in the signaling pathways of the Eph receptors, however, are incompletely characterized. Using a yeast two-hybrid screen, we have identified a novel signaling intermediate, SHEP1 (SH2 domain-containing Eph receptor-binding protein 1), which is expressed in the embryonic and adult brain. SHEP1 contains an Src homology 2 domain that binds to a conserved tyrosine-phosphorylated motif in the juxtamembrane region of the EphB2 receptor and may itself be a target of EphB2 kinase activity, since it becomes heavily tyrosine-phosphorylated in cells expressing activated EphB2. SHEP1 also contains a domain similar to Ras guanine nucleotide exchange factor domains and binds to the GTPases R-Ras and Rap1A, but not Ha-Ras or RalA. Thus, SHEP1 directly links activated, tyrosine-phosphorylated Eph receptors to small Ras superfamily GTPases. (+info)Solution structure of the receptor tyrosine kinase EphB2 SAM domain and identification of two distinct homotypic interaction sites. (6/154)
The sterile alpha motif (SAM) is a protein interaction domain of around 70 amino acids present predominantly in the N- and C-termini of more than 60 diverse proteins that participate in signal transduction and transcriptional repression. SAM domains have been shown to homo- and hetero-oligomerize and to mediate specific protein-protein interactions. A highly conserved subclass of SAM domains is present at the intracellular C-terminus of more than 40 Eph receptor tyrosine kinases that are involved in the control of axonal pathfinding upon ephrin-induced oligomerization and activation in the event of cell-cell contacts. These SAM domains appear to participate in downstream signaling events via interactions with cytosolic proteins. We determined the solution structure of the EphB2 receptor SAM domain and studied its association behavior. The structure consists of five helices forming a compact structure without binding pockets or exposed conserved aromatic residues. Concentration-dependent chemical shift changes of NMR signals reveal two distinct well-separated areas on the domains' surface sensitive to the formation of homotypic oligomers in solution. These findings are supported by analytical ultracentrifugation studies. The conserved Tyr932, which was reported to be essential for the interaction with SH2 domains after phosphorylation, is buried in the hydrophobic core of the structure. The weak capability of the isolated EphB2 receptor SAM domain to form oligomers is supposed to be relevant in vivo when the driving force of ligand binding induces receptor oligomerization. A formation of SAM tetramers is thought to provide an appropriate contact area for the binding of a low-molecular-weight phosphotyrosine phosphatase and to initiate further downstream responses. (+info)An Eph receptor regulates integrin activity through R-Ras. (7/154)
The ability of integrins to mediate cell attachment to extracellular matrices and to blood proteins is regulated from inside the cell. Increased ligand-binding activity of integrins is critical for platelet aggregation upon blood clotting and for leukocyte extravasation to inflamed tissues. Decreased adhesion is thought to promote tumor cell invasion. R-Ras, a small intracellular GTPase, regulates the binding of integrins to their ligands outside the cell. Here we show that the Eph receptor tyrosine kinase, EphB2, can control integrin activity through R-Ras. Cells in which EphB2 is activated become poorly adherent to substrates coated with integrin ligands, and a tyrosine residue in the R-Ras effector domain is phosphorylated. The R-Ras phosphorylation and loss of cell adhesion are causally related, because forced expression of an R-Ras variant resistant to phosphorylation at the critical site made cells unresponsive to the anti-adhesive effect of EphB2. This is an unusual regulatory pathway among the small GTPases. Reduced adhesiveness induced through the Eph/R-Ras pathway may explain the repulsive effect of the Eph receptors in axonal pathfinding and may facilitate tumor cell invasion and angiogenesis. (+info)Replacing two conserved tyrosines of the EphB2 receptor with glutamic acid prevents binding of SH2 domains without abrogating kinase activity and biological responses. (8/154)
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. (+info)EphB4 is a type of receptor tyrosine kinase (RTK) that belongs to the Eph receptor family. These receptors are involved in cell-cell communication during development and tissue homeostasis. Specifically, EphB4 is a membrane-bound protein that interacts with its ligand, ephrin-B2, which is also a transmembrane protein, to mediate bidirectional signaling between neighboring cells.
The binding of ephrin-B2 to EphB4 triggers a variety of intracellular signaling events that regulate various cellular processes, including cell migration, adhesion, and repulsion. In the context of the cardiovascular system, EphB4 plays important roles in vascular development, angiogenesis, and arterial-venous specification.
Mutations or dysregulation of EphB4 have been implicated in various pathological conditions, such as cancer, atherosclerosis, and neurological disorders. Therefore, understanding the function and regulation of EphB4 has important implications for the development of novel therapeutic strategies for these diseases.
EphB2 is a type of receptor tyrosine kinase (RTK) that belongs to the Eph family of receptors. These receptors are involved in bidirectional communication between cells and are important in the development and function of the nervous system. Specifically, EphB2 receptors are expressed on the surface of certain types of neurons and bind to ephrin-B ligands on nearby cells. This binding triggers a cascade of intracellular signaling events that can regulate various cellular processes, including cell migration, adhesion, and axon guidance.
EphB2 receptors have also been implicated in the pathology of several diseases, including cancer. For example, abnormal activation of EphB2 has been linked to tumor growth, progression, and metastasis in certain types of cancer. Therefore, EphB2 is an important target for the development of new therapies for cancer and other diseases.
EphB1 is a type of receptor tyrosine kinase (RTK) that belongs to the Eph family of receptors. It is a single-pass transmembrane protein that contains an extracellular domain with a binding site for its ligand, ephrin-Bs, and an intracellular domain with tyrosine kinase activity.
EphB1 receptors are primarily expressed in the nervous system, where they play important roles in various developmental processes, including axon guidance, neuronal migration, and synaptic plasticity. They also have been implicated in tumorigenesis and cancer progression, as well as in the regulation of immune responses.
The binding of ephrin-Bs to EphB1 receptors triggers a variety of intracellular signaling pathways that can lead to both forward and reverse signaling. Forward signaling occurs when the activated EphB1 receptor phosphorylates downstream effector proteins, leading to changes in cell behavior such as repulsion or adhesion. Reverse signaling occurs when ephrin-Bs, which are also transmembrane proteins, activate their own intracellular signaling pathways upon binding to EphB1 receptors.
Overall, the EphB1 receptor is a crucial component of the Eph/ephrin signaling system that plays important roles in various biological processes and has potential implications for disease treatment and diagnosis.
Ephrin-B2 is a type of protein that belongs to the ephrin family and is primarily involved in the development and function of the nervous system. It is a membrane-bound ligand for Eph receptor tyrosine kinases, and their interactions play crucial roles in cell-cell communication during embryogenesis and adult tissue homeostasis.
Ephrin-B2 is specifically a glycosylphosphatidylinositol (GPI)-anchored protein that is expressed on the cell membrane of various cell types, including endothelial cells, neurons, and some immune cells. Its interactions with Eph receptors, which are transmembrane proteins, lead to bidirectional signaling across the contacting cell membranes. This process regulates various aspects of cell behavior, such as adhesion, migration, repulsion, and proliferation.
In the context of the cardiovascular system, ephrin-B2 is essential for the development and maintenance of blood vessels. It is involved in the formation of arterial-venous boundaries, vascular branching, and remodeling. Mutations or dysregulation of ephrin-B2 have been implicated in various diseases, including cancer, where it can contribute to tumor angiogenesis and metastasis.
Ephrin-B1 is a type of protein that belongs to the ephrin family and is involved in cell signaling, specifically in the process known as cell-cell communication. It is a transmembrane protein, which means it spans the membrane of the cell and has a portion that faces the outside of the cell (the extracellular domain) and a portion that faces the inside of the cell (the intracellular domain).
Ephrin-B1 binds to Eph receptors, which are tyrosine kinase receptors found on the surface of neighboring cells. This binding results in the initiation of a signaling cascade that can influence various cellular processes, including cell migration, adhesion, and proliferation.
Ephrin-B1 is widely expressed in various tissues throughout the body, including the nervous system, where it plays important roles in the development and function of the brain. Mutations in the gene that encodes ephrin-B1 have been associated with certain neurological disorders, such as intellectual disability and epilepsy.
EphB3 is a type of receptor tyrosine kinase that belongs to the Eph family of receptors. It is a transmembrane protein that plays a crucial role in cell signaling and communication, particularly during embryonic development and tissue organization. The EphB3 receptor binds to ephrin-B ligands, which are also transmembrane proteins expressed on neighboring cells.
The binding of ephrin-B to EphB3 initiates a bidirectional signaling process that regulates various cellular processes such as cell adhesion, migration, and repulsion. This interaction is important for the formation of boundaries between different tissues, axon guidance, and synaptic plasticity in the nervous system.
Mutations in the EphB3 gene have been associated with several human diseases, including cancer, immune disorders, and neurological conditions. Therefore, understanding the function and regulation of EphB3 receptors is essential for developing novel therapeutic strategies to treat these diseases.
EphB6 is not a traditional "receptor" in the sense of a protein that binds to a signaling molecule and triggers a cellular response. Instead, EphB6 is a member of the Eph receptor tyrosine kinase family, which are involved in intracellular signaling pathways.
EphB6 is unique among the Eph receptors because it lacks a functional kinase domain and is therefore considered to be a "non-kinase" member of the family. Instead, EphB6 forms complexes with other Eph receptors and modulates their signaling activity.
EphB6 has been shown to interact with other Eph receptors, such as EphB2 and EphB3, and regulate their downstream signaling pathways. It is involved in various cellular processes, including cell adhesion, migration, and differentiation. Dysregulation of EphB6 has been implicated in several diseases, including cancer, where it can act as a tumor suppressor or promote tumor progression depending on the context.
In summary, while EphB6 is not a traditional receptor that binds to signaling molecules and triggers cellular responses, it is a member of the Eph receptor tyrosine kinase family that modulates the signaling activity of other Eph receptors and plays important roles in various cellular processes.
Eph family receptors are a group of tyrosine kinase receptors that play crucial roles in the development and function of the nervous system, as well as in other tissues. They are named after the first discovered member of this family, EPH (Erythropoietin-Producing Human Hepatocellular carcinoma) receptor.
These receptors are divided into two subfamilies: EphA and EphB, based on their binding preferences for ephrin ligands. Ephrins are membrane-bound proteins that can be either GPI-anchored (ephrin-A) or transmembrane (ephrin-B), and they interact with Eph receptors in a bidirectional manner, activating both forward signaling in the receptor-expressing cell and reverse signaling in the ephrin-expressing cell.
Eph receptors and ephrins are essential for axon guidance, topographic mapping, and synaptic plasticity during neural development. They also participate in various processes in adult tissues, such as angiogenesis, tumorigenesis, and immune responses. Dysregulation of Eph family receptors has been implicated in several diseases, including cancer, neurological disorders, and vascular diseases.
EphB5 is a type of receptor tyrosine kinase that belongs to the Eph family of receptors. It is a cell surface receptor that interacts with its ligand, ephrin-B2, which is also a cell surface protein. The interaction between EphB5 and ephrin-B2 plays a crucial role in various biological processes, including cell migration, axon guidance, and tissue boundary formation during development.
EphB5 receptor is composed of an extracellular domain that contains the ligand-binding site, a transmembrane domain, and an intracellular domain with tyrosine kinase activity. Upon binding to its ligand, EphB5 undergoes dimerization and autophosphorylation of specific tyrosine residues in the intracellular domain. This triggers downstream signaling cascades that regulate various cellular processes.
Mutations in the EPHB5 gene have been associated with several human diseases, including cancer, intellectual disability, and congenital heart defects. Therefore, understanding the function of EphB5 receptor and its signaling pathways is essential for developing novel therapeutic strategies for these diseases.
Ephrin-B3 is a type of protein that belongs to the ephrin family and is involved in cell signaling, particularly during the development and functioning of the nervous system. It is a transmembrane protein, which means it spans the membrane of the cell and has a domain outside the cell and a domain inside the cell.
Ephrin-B3 interacts with Eph receptors on neighboring cells to initiate bidirectional signaling, which means that both the cells that express ephrin-B3 and the cells that express the Eph receptor are affected by this interaction. This signaling is important for various processes such as axon guidance, cell migration, and tissue boundaries formation during development. In addition, ephrin-B3 has been implicated in the regulation of synaptic plasticity and vascular remodeling in adults.
Mutations in the gene that encodes ephrin-B3 have been associated with certain neurological disorders, such as intellectual disability and epilepsy.
Ephrins are a family of membrane-bound proteins that play crucial roles in various biological processes, including cell migration, axon guidance, and tissue boundary formation during embryonic development. They interact with Eph receptors, which are tyrosine kinase receptors found on the surface of neighboring cells. This interaction results in bidirectional signaling between the two cells, affecting their behaviors and influencing the organization of tissues and organs.
There are two main types of ephrins: Ephrin-A (also known as GPI-anchored ephrins) and Ephrin-B (transmembrane ephrins). Ephrin-A proteins are attached to the cell membrane through a glycosylphosphatidylinositol (GPI) anchor, while Ephrin-B proteins have a transmembrane domain and a cytoplasmic tail. Both types of ephrins interact with Eph receptors, leading to the initiation of intracellular signaling cascades that regulate various cellular responses.
Dysregulation of ephrin/Eph receptor interactions has been implicated in several human diseases, including cancer, where they can contribute to tumor growth, progression, and metastasis. Therefore, understanding the functions and regulation of ephrins and their receptors is essential for developing novel therapeutic strategies to treat various diseases.