B61, A LIGAND FOR THE ECK RECEPTOR PROTEIN-TYROSINE KINASE, EXHIBITS NEUROTROPHIC ACTIVITY IN CULTURES OF RAT SPINAL-CORD NEURONS

Although the Eph subfamily represents the largest group of receptor pr otein-tyrosine kinases, the biological roles of the Eph-related recept ors and their ligands are not well understood, B61. has been identifie d recently by receptor affinity chromatography as a ligand for the Eph -related receptor Eck (Bartley et al.: Nature 368:558-560, 1994), Here we show that Eck immunoreactivity is localized in areas of the embryo nic rat spinal cord that are rich in axons, suggesting that Eck plays a role in this region of the developing nervous system, To examine the biological function of Eck, monolayer cultures of dissociated cells f rom embryonic rat spinal cord were treated with soluble B61, With an E D(50) of approximately 10 ng/ml, B61 treatment improved the survival o f the overall neuronal population, Furthermore, in the presence of B61 neurites were longer and more elaborated, B61 similarly affected surv ival and neurite length in cultures enriched in motor neurons, These n eurotrophic effects of B61 were not observed in the presence of anti-E ck antibodies, indicating that these effects are likely to be mediated by the Eck receptor. (C) 1996 Wiley-Liss, Inc.