The ephrin/Eph signaling pathway
The ephrin/Eph signaling pathway is an important tool for cell communication. Among others, it plays a central role in embryonic development. Similar to a construction site manager, the pathway is active wherever cells have to find their way – for example neuronal filaments in a developing brain. This site manager is particularly good at saying where something does not belong.
The membrane-bound ephrin-ligand of a cell contacts its signaling partner, the Eph-receptor on another cell. The binding of ephrin to the Eph-receptor triggers a signaling cascade into the receptor-bearing cell, which leads to a change in the cytoskeleton. A possible result of this contact is the repulsion of the two cells from each other. The message to the Eph-bearing cell: This is the wrong way.
The special feature of the ephrin/Eph signaling pathway is its ability to work in reverse as well, albeit with different consequences. Then the ephrin/Eph binding complex triggers in the ephrin-cell a signaling cascade. This bi-directional communication allows cells to better modulate signals. The communication via ephrin/Eph thus seems able to relay a whole bunch of news, ranging from "come closer" to "turn around".
The ephrin/Eph signaling pathway is involved in many processes: wherever cells contact each other and have to separate again. Some examples for such processes include the conversion of neuronal stem cells into neurons in the adult brain, the breakdown of synaptic compounds, the inhibition of regeneration after a brain or spinal cord injury, and the metastasis of cancer cells. This list shows that decoding the ephrin/Eph signaling pathway also has great therapeutic potential.