IDENTIFICATION OF FULL-LENGTH AND TRUNCATED FORMS OF EHK-3, A NOVEL MEMBER OF THE EPH RECEPTOR TYROSINE KINASE FAMILY

Factors that bind and activate receptor tyrosine kinases are known to play key roles during development and in the adult, The Eph-related re ceptors constitute the largest known family of receptor tyrosine kinas es, Members of the Eph family exhibit intriguing patterns of expressio n in the embryo, implicating them in a variety of developmental proces ses, and their expression is often restricted to particular subpopulat ions of postmitotic neurons in the adult, We describe the identificati on and characterization of a novel member of the Eph receptor family, which we have termed Ehk-3 for Eph Homologous Kinase 3, Ehk-3 displays all the major structural features shared by other members of the Eph family, including a cysteine-rich region and tandem fibronectin type-I II domains in its extracellular portion, Ehk-3 is expressed in two for ms in a developmentally-regulated fashion: a conventional full-length version containing the intracellular tyrosine kinase domain, as well a s a truncated form that lacks this domain, Both forms of Ehk-3 are qui te restricted to the nervous system in the adult, but Ehk-3 is more wi dely expressed in the embryo, suggesting that Ehk-3 mediates different functions during development and in the adult.