Similar rates of phosphatidylinositol hydrolysis following activation of wild-type and truncated rat neurokinin-1 receptors

J Neurochem. 1995 Mar;64(3):1183-91. doi: 10.1046/j.1471-4159.1995.64031183.x.

Abstract

The substance P (neurokinin-1) receptor belongs to the family of seven putative transmembrane domain receptors that are coupled via G proteins to phospholipase C activation. Homologous desensitization of substance P-stimulated responses has been described in various systems. The rat neurokinin-1 receptor and a truncated mutant lacking the carboxyl-terminal region were expressed in Chinese hamster ovary cells to examine the mechanisms of substance P-induced desensitization. Wild-type and truncated receptor-bearing cells were indistinguishable in agonist binding affinity and EC50 of substance P-induced accumulation of 3H-inositol phosphates. Substance P-induced responses continued for 30-45 min in cells expressing wild-type and truncated receptors as well as in rat LRM-55 and human U373 cells, which express endogenous neurokinin-1 receptors. In transfected cells expressing the wild-type receptor, CP-96,345 added 15 min after substance P blocked further responses, demonstrating the continuing presence of responsive receptors. The rates of accumulation of 3H-inositol phosphates were four times greater in the initial 15 s of stimulation than for the next 20 min for both wild-type and truncated receptor types. This decrease in rate of substance P-stimulated phosphatidylinositol hydrolysis is therefore not dependent on the carboxyl-terminal region of the rat neurokinin-1 receptor, which contains 26 serine and threonine residues. These results are discussed in relation to current ideas regarding neurokinin-1 receptor desensitization.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biphenyl Compounds / pharmacology
  • CHO Cells
  • Cricetinae
  • Inositol Phosphates / metabolism*
  • Phosphatidylinositols / metabolism*
  • Rats
  • Receptors, Neurokinin-1 / chemistry
  • Receptors, Neurokinin-1 / metabolism*
  • Recombinant Proteins
  • Signal Transduction
  • Structure-Activity Relationship
  • Substance P / metabolism
  • Substance P / pharmacology*
  • Time Factors
  • Transfection

Substances

  • Biphenyl Compounds
  • Inositol Phosphates
  • Phosphatidylinositols
  • Receptors, Neurokinin-1
  • Recombinant Proteins
  • Substance P
  • CP 96345