Cell-Cell Adhesion Mediated by Binding of Membrane-anchored Ligand LERK-2 to the EPH-related Receptor Human Embryonal Kinase 2 Promotes Tyrosine Kinase Activity

doi:10.1074/jbc.271.40.24747

Cell-Cell Adhesion Mediated by Binding of Membrane-anchored Ligand LERK-2 to the EPH-related Receptor Human Embryonal Kinase 2 Promotes Tyrosine Kinase Activity*

From the ^‡ Chemotherapeutisches Forschungsinstitut, Georg-Speyer-Haus, 60596 Frankfurt, Federal Republic of Germany, the
^§ Immunex Research and Development Corp., Seattle, Washington 98101, and the
^¶ Bayer AG, Institute of Virology, 42096 Wuppertal, Federal Republic of Germany

^∥ To whom correspondence should be addressed:
Chemotherapeutisches Forschungsinstitut, Georg-Speyer-Haus, Paul-Ehrlich-Strasse 42-44, 60596 Frankfurt, Germany
. Tel.: 011-49-69-63395110; Fax: 011-49-69-63395297.

Abstract

Human embryonal kinase 2 (HEK2) is a protein-tyrosine kinase that is a member of the EPH family of receptors. Transcripts for HEK2 have a wide tissue distribution. Recently, a still growing family of ligands, which we have named LERKs, for igands of the ph-elated inases, has been isolated. In order to analyze functional effects between the LERKs and the HEK2 receptor, we expressed HEK2 cDNA in an interleukin-3-dependent progenitor cell line 32D that grows as single cells in culture. Within the group of LERKs, LERK-2 and −5 were shown to bind to HEK2. Membrane-bound and soluble forms of LERK-2 were demonstrated to signal through HEK2 as judged by receptor phosphorylation. Coincubation of HEK2 and LERK-2 expressing cells induced cell-cell adhesion and formation of cell aggregates. This interaction could be inhibited by preincubation of HEK2 expressing cells with soluble LERK-2. Coexpression of HEK2 and LERK-2 in 32D cells showed reduced kinase activity and autophosphorylation of HEK2 compared with the juxtacrine stimulation, which seems to be due to a reduced sensitivity of the receptor.

Footnotes

↵* The Georg-Speyer-Haus is supported by the Bundesgesundheitsministerium and the Hessisches Ministerium für Wissenschaft und Kunst. This work was further supported by grants from the Georg und Franziska Speyer'sche-Hochschulstiftung, the Hessischer Verein zur Förderung der Jugendgesundheitspflege e.V., and the Deutsche Forschungsgemeinschaft Grants RU 242/11 u. 12-1, STR 336/6-1. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

RTK

receptor tyrosine kinase

HEK

human embryonal kinase

LERK

ligands of the eph-related kinase

Pipes

1,4-piperazinediethanesulfonic acid

PBS

phosphate-buffered saline.
- Received November 3, 1995.
- Revision received June 18, 1996.