The Low-Affinity Binding of Second Generation Radiotracers Targeting TSPO is Associated with a Unique Allosteric Binding Site

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Abstract

[ 11 C]-PK11195 (PK11195) has been widely used with positron emission tomography (PET) to assess levels of the translocator protein 18 kDa (TSPO) as a marker of neuroinflammation. Recent ligands, such as [ 11 C]-PBR28 and [ 11 C]-DPA713, have improved signal-to-noise ratio and specificity for TSPO over PK11195. However, these second generation radiotracers exhibit binding differences due to a single polymorphism (rs6971) that leads to three genotypes: C/C, C/T and T/T associated with high, mixed and low binding affinities, respectively. Here we report that [ 3 H]-DPA-713 in the presence of cholesterol or PK11195 has an accelerated dissociation rate from TSPO in platelets isolated from individuals with the T/T genotype. This allosteric interaction was not observed in platelets isolated from individuals with the C/C or C/T genotype. The results provide a molecular rationale for low binding affinity of T/T TSPO and further support the exclusion of these subjects from PET imaging studies using second generation TSPO ligands.

Original languageEnglish (US)
JournalJournal of Neuroimmune Pharmacology
Volume13
Issue number1
DOIs
StatePublished - Mar 1 2018

Keywords

  • Allosteric modulation
  • Residence time
  • Translocator protein 18 KDa (TSPO)

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Immunology and Allergy
  • Immunology
  • Pharmacology

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