A single amino acid of the human and rat neurotensin receptors (subtype 1) determining the pharmacological profile of a species-selective neurotensin agonist

Bernadette Cusack, Karen Jansen, Daniel J. McCormick, Thomas Chou, Yuan Ping Pang, Elliott Richelson

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

The neurotensin (NT) receptor, subtype 1 (NTR1), is a 7-transmembrane-spanning receptor, forming 3 extracellular and 3 intracellular loops. Previously, we showed that the third outer loop (E3) is the binding site for NT and its analogs, several of which bind with higher affinity to rat NTR1 (rNTR1) than to human NTR1 (hNTR1). In particular, NT34 {[3,1'-naphthyl-1-Ala11]NT(8-13)} has greater than 60-fold higher affinity for RNTR1 (46 and 60 Pm for transiently- and stably-transfected cells, respectively) than for HNTR1 (2.8 and 5.8 Nm for transiently- and stably-transfected cells, respectively) isolated from transfected cell membranes. Previously, our molecular modeling studies of RNTR1 and HNTR1 showed that the binding pocket in the human receptor for NT34 is smaller in volume from the bulky residue Tyr339 in the pocket center, as compared with the corresponding residue Phe344 in the rat binding pocket. Therefore, with site-directed mutagenesis, we derived mutant forms of RNTR1(F344Y) and HNTR1(Y339F). Examination of the mutant receptors from membranal preparations of transfected cells in radioligand binding assays and with intact cells in functional assays (phosphatidyl-4,5-bisphosphate turnover) showed that the human-like rat receptor and the rat-like human receptor bound NT34 with a predicted reverse of binding compared with its binding to the wild-type receptors. These results strongly affirm our molecular modeling studies and demonstrate the importance of the study of even minor structural variations in proteins to determine the basis of significantly different drug responses, an area of focus for pharmacological research in the 21st century. (C) 2000 Elsevier Science Inc.

Original languageEnglish (US)
Pages (from-to)793-801
Number of pages9
JournalBiochemical Pharmacology
Volume60
Issue number6
DOIs
StatePublished - Sep 15 2000

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Keywords

  • Binding site
  • Neurotensin receptor
  • Peptide analogs
  • Site-directed mutagenesis
  • Structure-activity studies
  • Subtype 1

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology

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