[Ephrins, neuronal development and plasticity].

AIMS

In this work we review the main characteristics of ephrins and their Eph receptors (ER), as well as descriptions that have been published to date of the different functions the ephrin/Eph system (EES) performs in neuronal development.

DEVELOPMENT

ER constitute the largest group of tyrosine kinase receptors and are found in many different types of cells during development and in mature tissues. Their ligands, the ephrins, are membrane anchored proteins that are divided into class A ephrins, with a glycosylphosphatidylinositol bond, and class B ephrins, with a hydrophobic transmembrane region and a cytoplasmic domain. The EES is the only one that involves bidirectional signalling. Thus, the ephrin Eph interaction both activates the tyrosine kinase domain of the ER, with the resulting signal transduction in the cell that expresses Eph, and produces a reverse signal in the cells that contain the ligands. Over the last decade a number of studies have been conducted that establish the involvement of the EES in neuronal development. Although the classic function of this system is that of establishing patterns of both cellular and axonal organisation, recent reports describe how the ER and their ephrin ligands regulate synaptogenesis and the maturation of terminals during development, as well as the plasticity of the adult brain.

CONCLUSIONS

Recent findings open up new expectations regarding the possible functions carried out by the interaction of ephrin and Eph. They also confirm the crucial role played by this system in all the processes involved in allowing neuronal development to take place in a correct fashion.