Rapid Desensitization of Serotonin 5-HT2C Receptor-Stimulated Intracellular Calcium Mobilization in CHO Cells Transfected With Cloned Human 5-HT2C Receptors

J Neurochem. 1995 Jun;64(6):2473-9. doi: 10.1046/j.1471-4159.1995.64062473.x.

Abstract

Serotonin 5-HT2C receptor-mediated intracellular Ca2+ mobilization was investigated in Chinese hamster ovary (CHO) cells transfected with 5-HT2C receptors. Fura-2 acetoxymethyl ester was used to investigate the regulation of 5-HT2C receptor function. CHO cells, transfected with a cDNA clone for the 5-HT2C receptor, expressed 287 fmol/mg of the receptor protein as determined by mianserin-sensitive [3H]mesulergine binding (KD = 0.49 nM). The addition of 5-HT mobilized intracellular Ca2+ in a dose-dependent fashion, ranging from a basal level of 99 +/- 1.8 up to 379 +/- 18 nM, with an EC50 value for 5-HT of 0.029 microM. Exposure to 5-HT, 1-(3-chlorophenyl)piperazine dihydrochloride (a 5-HT2C agonist), and 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane (a 5-HT2C and 5-HT2A agonist) resulted in increased intracellular Ca2+ levels. Mianserin, mesulergine, ritanserin, and ketanserin each blocked 5-HT-mediated intracellular Ca2+ mobilization more effectively than spiperone. The receptor was rapidly desensitized by preexposure to 5-HT in a time- and concentration-dependent manner. Mezerein and phorbol 12-myristate 13-acetate, protein kinase C activators, weakly inhibited the intracellular Ca2+ mobilization induced by 10 microM 5-HT. Furthermore, the protein kinase C inhibitor H-7 partially prevented the protein kinase C activator-induced inhibition of the 5-HT-mediated increase in intracellular Ca2+ concentration. The desensitization induced by pretreatment with 5-HT was blocked by W-7, added in conjunction with 5-HT, and partially inhibited by W-5, a nonselective inhibitor of protein kinases and weak analogue of W-7.(ABSTRACT TRUNCATED AT 250 WORDS)

MeSH terms

  • Animals
  • Biological Transport
  • CHO Cells / physiology*
  • Calcium / metabolism*
  • Cricetinae
  • Humans
  • Intracellular Membranes / metabolism*
  • Protein Kinase C / physiology
  • Receptors, Serotonin / classification
  • Receptors, Serotonin / genetics*
  • Receptors, Serotonin / metabolism*
  • Serotonin Antagonists / pharmacology
  • Serotonin Receptor Agonists / pharmacology
  • Sulfonamides / pharmacology
  • Transfection*

Substances

  • Receptors, Serotonin
  • Serotonin Antagonists
  • Serotonin Receptor Agonists
  • Sulfonamides
  • naphthalenesulfonamide
  • Protein Kinase C
  • Calcium