(h) Human phospho - receptor tyrosine kinase array for EphA2, EphB2 and EphB4
ephrin receptors from control BP (shCtr) and BP silenced for Tie2 (siTie2 I and siTie2 II).
For intance, GluA2 binds to PDZ domains 4 and 5 (Dong et al 1997), while
ephrin receptors bind to domains 6 and 7 (Torres et al 1998).
Not exact matches
The team was successful in getting the drug to piggyback on 123B9, an agent they devised to target an oncogene called EphA2 (
ephrin type - A
receptor 2).
Recently, however,
ephrins and Eph
receptors have also been found in extracellular vesicles / exosomes — small droplets of fat released by cells, used as transport vehicles, signal transmitters or for eliminating cell components.
When an
ephrin meets the Eph
receptor of another cell, they join to form an
ephrin - Eph complex.
One way this communication happens is through the
ephrin / Eph -
receptor system, which is able to guide cell migration and the growth of neuronal extensions.
Ephrins and Eph
receptors have also been found in the exosomes of cancer cells.
Eph
receptors and their binding partners, the
ephrins, are found on the surface of almost all cell types.
«This is why it's so fundamentally important to understand how cells use this system to communicate,» says Rüdiger Klein, whose Department at the Max Planck Institute of Neurobiology is studying
ephrins and Eph
receptors.
Eph
receptors and their partner proteins, the
ephrins, are vital for intercellular communication.
However, Rüdiger Klein and his team at the Max Planck Institute of Neurobiology have now shown that cells can also pack and release active
ephrins and Eph
receptors through extracellular vesicles.
The
ephrins and Eph
receptors in angiogenesis.
Eph
receptor and
ephrin ligand signalling has been implicated in vascular development and in in vivo models of angiogenesis where bi-directional signalling mediates juxtracrine cell — cell contact, cell adhesion to extracellular matrix and cell migration30, 31,32.
Studies by ours and other groups have shown that a number of EphA2 and EphA3 mutations inactivate Eph
receptor canonical signaling by disrupting
ephrin binding or kinase activity, consistent with a role of canonical signaling in tumor suppression.
Certain Eph
receptors and
ephrins promote tumor angiogenesis.
This knowledge is useful for the development of disease treatments based on modulating Eph
receptor /
ephrin activities.
This leads to bidirectional signals emanating from Eph
receptor -
ephrin complexes positioned at sites of cell - cell contact.
Binding to
ephrin ligands on the surface of neighboring cells induces canonical signaling involving
receptor clustering, autophosphorylation on tyrosine residues, and kinase activity - dependent downstream signaling.
(A) Eph
receptor -
ephrin binding at cell - cell contact sites results in the dimerization / clustering of Eph
receptor -
ephrin complexes, and initiation of canonical signals through the
receptor cytoplasmic domain.
We discovered several Eph
receptors and
ephrins, and research in our laboratory is dedicated to the characterization of Eph
receptor signal transduction mechanisms and biological functions using biochemical, mass spectrometry, molecular biology and cell biology approaches in conjunction with animal models.
We also found that the EphB4
receptor expressed on the surface of breast cancer cells can promote tumor xenograft growth by enhancing blood vessel formation through interactions with its preferred ligand,
ephrin - B2, present in tumor endothelial cells.
We found that canonical signaling by the EphB4
receptor is low in breast cancer cells and that
ephrin - induced stimulation of EphB4 kinase activity inhibits breast cancer cell malignancy in culture and tumor growth in vivo (Figure 1A) through inhibition of the CRK proto - oncogene.
Receptor tyrosine kinases of the Eph family and their ligands, the
ephrins, represent an important cell communication system that controls a vast array physiological and disease processes.
Most of the peptides are antagonists, but the peptides targeting EphA2 are agonists that activate
receptor signaling and endocytosis similarly to the natural
ephrin ligands.
These activities are independent of
ephrin binding and / or kinase activity and their mechanism is not well understood but in some cases depends on Eph
receptor phosphorylation on serine / threonine residues (red circle).
This is unlike the natural
ephrin ligands, each of which promiscuously binds to multiple Eph
receptors.
We have identified tyrosine and serine / threonine phosphorylation sites of Eph
receptors and
ephrins using mass spectrometry and investigated the signaling role of these phosphorylation sites.
Understanding the effects of Eph
receptor mutations in cancer cells will help shed light on the role of the Eph
receptor /
ephrin system in cancer cell transformation, malignant progression and drug resistance.
Peptides can target the
ephrin - binding pocket of Eph
receptors with high affinity and specificity, affecting
receptor function.
(A) Peptides targeting the Eph
receptors can function as antagonists that inhibit
ephrin binding and
receptor signaling, or in some cases as agonists that mimic the
ephrins by activating Eph
receptor signaling.
Binding to the Eph
receptors can also cause the
ephrins, which have a cytoplasmic domain or a GPI - anchor, to transmit signals.