CB1 and GPR55 Receptors Are Co-Expressed and Form Heteromers in Rat and Monkey Striatum

Exp Neurol. 2014 Nov;261:44-52. doi: 10.1016/j.expneurol.2014.06.017. Epub 2014 Jun 23.


Heteromerization of G-protein-coupled receptors is an important event as they integrate the actions of extracellular signals to give heteromer-selective ligand binding and signaling, opening new avenues in the development of potential drug targets in pharmacotherapy. The aim of the present paper was to check for cannabinoid CB1-GPR55 receptor heteromers in the central nervous system (CNS), specifically in striatum. First, a direct interaction was demonstrated in cells transfected with the cDNA for the human version of the receptors, using bioluminescence resonance energy transfer and in situ proximity ligation assays (PLA). In the heterologous system, a biochemical fingerprint consisting on cross-antagonism in ERK1/2 phosphorylation was detected. The cross-antagonism was also observed on GPR55-mediated NFAT activation. Direct identification of GPR55 receptors in striatum is here demonstrated in rat brain slices using a specific agonist. Moreover, the heteromer fingerprint was identified in these rat slices by ERK1/2 phosphorylation assays whereas PLA assays showed results consistent with receptor-receptor interactions in both caudate and putamen nuclei of a non-human primate. The results indicate not only that GPR55 is expressed in striatum but also that CB1 and GPR55 receptors form heteromers in this specific CNS region.

Keywords: BRET; Cannabinoids; GPCR heteromerization; PLA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Bioluminescence Resonance Energy Transfer Techniques
  • Corpus Striatum / drug effects
  • Corpus Striatum / metabolism*
  • DNA Fingerprinting
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology
  • Female
  • HEK293 Cells
  • Humans
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Macaca fascicularis
  • Male
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Models, Molecular
  • Piperidines / pharmacology
  • Pyrazoles / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Cannabinoid, CB1 / metabolism*
  • Receptors, Cannabinoid / metabolism*
  • Receptors, G-Protein-Coupled / metabolism*
  • Rimonabant
  • Transfection


  • Bacterial Proteins
  • Enzyme Inhibitors
  • GPR55 protein, rat
  • Luminescent Proteins
  • Piperidines
  • Pyrazoles
  • Receptor, Cannabinoid, CB1
  • Receptors, Cannabinoid
  • Receptors, G-Protein-Coupled
  • yellow fluorescent protein, Bacteria
  • Mitogen-Activated Protein Kinase 3
  • Rimonabant