Fluorescent derivatives of σ receptor ligand 1-cyclohexyl-4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]piperazine (PB28) as a tool for uptake and cellular localization studies in pancreatic tumor cells

J Med Chem. 2011 Aug 25;54(16):5858-67. doi: 10.1021/jm200591t. Epub 2011 Jul 20.


Fluorescent derivatives of σ(2) high affinity ligand 1-cyclohexyl-4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]piperazine 1 (PB28) were synthesized. NBD or dansyl fluorescent tags were connected through a 5- or 6-atom linker in two diverse positions of 1 structure. Good σ(2) affinities were obtained when the fluorescent tag was linked to 5-methoxytetralin nucleus replacing the methyl function. NBD-bearing compound 16 displayed high σ(2) affinity (K(i) = 10.8 nM) and optimal fluorescent properties. Its uptake in pancreatic tumor cells was evaluated by flow cytometry, showing that it partially occurs through endocytosis. In proliferating cells, the uptake was higher supporting that σ(2) receptors are markers of cell proliferation and that the higher the proliferation is, the stronger the antiproliferative effect of σ(2) agonists is. Colocalization of 16 with subcellular organelles was studied by confocal microscopy: the greatest was in endoplasmic reticulum and lysosomes. Fluorescent σ(2) ligands show their potential in clarifying the mechanisms of action of σ(2) receptors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Binding, Competitive
  • Cell Line, Tumor
  • Endocytosis
  • Endoplasmic Reticulum / metabolism
  • Flow Cytometry
  • Fluorescence
  • Humans
  • Ligands*
  • Lysosomes / metabolism
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Models, Chemical
  • Molecular Structure
  • Pancreatic Neoplasms / metabolism
  • Pancreatic Neoplasms / pathology
  • Piperazines / chemistry
  • Piperazines / metabolism*
  • Piperazines / pharmacokinetics*
  • Protein Binding
  • Protein Isoforms / agonists
  • Protein Isoforms / metabolism
  • Radioligand Assay
  • Receptors, sigma / agonists
  • Receptors, sigma / metabolism*


  • Ligands
  • PB28 compound
  • Piperazines
  • Protein Isoforms
  • Receptors, sigma