MOLECULAR-CLONING OF A LEVOCABASTINE-SENSITIVE NEUROTENSIN BINDING-SITE

A search for sequences homologous to the neurotensin receptor cDNA in a rat hypothalamic library has identified a novel neurotensin receptor (NTR-2). The 1539 bp cDNA encodes a 416 amino acid protein and shows highest homology to the previously cloned neurotensin receptor (NTR-1) (64% homology and 43% identity), Binding and pharmacological studies demonstrate that NTR-2 expressed in COS cells recognizes neurotensin ( NT) with high affinity as well as several other agonists and antagonis ts, However, a fundamental difference was found; unlike NTR-1, NTR-2 r ecognizes, with high affinity, levocabastine, a histamine H1 receptor antagonist previously shown to compete with NT for low-affinity bindin g sites in brain.