Expression pattern of the type 1 sigma receptor in the brain and identity of critical anionic amino acid residues in the ligand-binding domain of the receptor

Pankaj Seth, Malliga E. Ganapathy, Simon J. Conway, Christy D. Bridges, Sylvia B Smith, Pierre Casellas, Vadivel Ganapathy

Research output: Contribution to journalArticle

70 Scopus citations


The type 1 σ receptor (σR1) has been shown to participate in a variety of functions in the central nervous system. To identify the specific regions of the brain that are involved in σR1 function, we analyzed the expression pattern of the receptor mRNA in the mouse brain by in situ hybridization. σR1 mRNA was detectable primarily in the cerebral cortex, hippocampus, and Purkinje cells of cerebellum. To identify the critical anionic amino acid residues in the ligand-binding domain of σR1, we employed two different approaches: chemical modification of anionic amino acid residues and site-directed mutagenesis. Chemical modification of anionic amino acids in σR1 with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide reduced the ligand-binding activity markedly. Since it is known that a splice variant of this receptor which lacks exon 3 does not have the ability to bind σ ligands, the ligand-binding domain with its critical anionic amino acid residues is likely to be present in or around the region coded by exon 3. Therefore, each of the anionic amino acids in this region was mutated individually and the influence of each mutation on ligand binding was assessed. These studies have identified two anionic amino acids, D126 and E172, that are obligatory for ligand binding. Even though the ligand-binding function was abolished by these two mutations, the expression of these mutants was normal at the protein level. These results show that σR1 is expressed at high levels in specific areas of the brain that are involved in memory, emotion and motor functions. The results also provide important information on the chemical nature of the ligand-binding site of σR1 that may be of use in the design of σR1-specific ligands with potential for modulation of σR1-related brain functions.

Original languageEnglish (US)
Pages (from-to)59-67
Number of pages9
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Issue number1
Publication statusPublished - Jul 25 2001



  • Anionic amino acid
  • Brain
  • Chemical modification
  • In situ hybridization
  • Ligand-binding domain
  • Sigma receptor

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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