IL-1-BETA ALTERS THE EXPRESSION OF THE RECEPTOR TYROSINE KINASE GENE R-EPHA3 IN NEONATAL RAT CARDIOMYOCYTES

To identify proinflammatory cytokine responsive genes in the myocardiu m, we used differential display to study RNA isolated from neonatal ra t cardiac myocytes treated with tumor necrosis factor-alpha (TNF-alpha ) and interleukin-1 beta (IL-1 beta). Sequence analysis of differentia l display products confirmed by reverse Northern blots revealed one cl one as the partial sequence of an Eph-related receptor tyrosine kinase (r-EphA3). In cardiac myocytes, 36-h exposure to TNF-alpha and IL-1 b eta reduced r-EphA3 transcripts to 59.9% (P < 0.01) of control levels; this effect was largely dependent on IL-1 beta. Western blot analysis showed that changes in r-EphA3 protein levels reflect that seen for t ranscripts. Cardiac nonmyocytes expressed substantially lower levels o f r-EphA3. Full-length r-EphA3 cDNA clone (3,077 base pair) yielded an amino acid sequence with 90-98% homology to the Eph receptor human Ep hA3, chick EphA3, and mouse EphA3. In the adult rat, r-EphA3 transcrip ts were most abundant in the heart, brain, and lung. These results sug gest that IL-1 beta may exert its effect on cardiac myocytes at least in part by altering r-EphA3 expression.