High‐Affinity Neurotensin Binding Sites in Differentiated Neuroblastoma N1E115 Cells

Abstract

This paper describes the interaction of neurotensin with mouse neuroblastoma N1E115 cells. Neurotensin binding sites are undetectable in nondifferentiated neuroblastoma cells. They appear during cell differentiation in the presence of a low serum concentration and dimethyl sulfoxide, and reach a maximal level after 50–60 h of incubation under these conditions. The binding of monoiodo[Trp¹¹]neurotensin to homogenates of differentiated N1E115 cells is specific, saturable, and reversible. The interaction is characterized by a dissociation constant of 150 pM and a maximal binding capacity of 9 fmol/mg of protein at 0°C, pH 7.5. These binding parameters, as well as the specificity toward a series of neurotensin analogues, are similar for neurotensin receptors in N1E115 cells and for the high-affinity binding sites that had been previously characterized in rat brain synaptic membranes by means of the same radiolabeled ligand. The presence of high-affinity binding sites for neurotensin in the neuroblastoma N1E115 provides a useful model to study the cellular responses that are generated by the association of neurotensin to its receptor in electrically excitable cells.