Fluor NMR study of amino acid derived ligand to study TSPO

Abstract

Translocator protein (TSPO, 18 kDa), previously known as peripheral-type benzodiazepine receptor, is an evolutionarily conserved membrane protein involved in various physiological processes and patho-physiological conditions. The endogeneous TSPO ligand is a polypeptide of 9 kDa, but dipeptides with biological activity have been previously synthesized and characterized. Herein, we synthesized a phenyl alanine derived ligand with a 19F labelling which opens prospective for 19F-MRI and potential 18F-PET applications. We characterized the coexistence of two conformers that are not equally sensitive to the media used for membrane protein studies. Interaction studies with the recombinant mouse TSPO (mTSPO) in different membrane-mimicking environments are presented using 19F NMR enabling structure/function characterizations. A change in the mTSPO environment from pure detergent to lipid/detergent mixture reveals different exchange rates between bound and free ligand forms. Competition experiments with the high-affinity drug ligand (R)-PK 11195 suggests that phenyl alanine derived ligand binds in the same protein cavity. HighlightsO_LIFluor labelling of ligands easily reveals the presence of conformers C_LIO_LIFluorinated phenyl alanine derived ligand interacts with TSPO C_LIO_LIFluor NMR enables characterization of TSPO ligand interactions C_LIO_LIFluor NMR facilitates exchange rate studies between free and bound ligand states C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC="FIGDIR/small/618300v1_ufig1.gif" ALT="Figure 1"> View larger version (13K): org.highwire.dtl.DTLVardef@1913e31org.highwire.dtl.DTLVardef@8a3c30org.highwire.dtl.DTLVardef@175881borg.highwire.dtl.DTLVardef@13aaa7d_HPS_FORMAT_FIGEXP M_FIG C_FIG