title: Alternative reagents for methotrexate as immobilizing anchor moieties in the optimization of MASPIT: synthesis and biological evaluation.
abstract: We report the evaluation of two alternative chemical dimerizer approaches aimed at increasing the sensitivity of MASPIT, a three-hybrid system that enables small-molecule target protein profiling in intact human cells. To circumvent the potential limitations related to the binding of methotrexate (MTX) to endogenous human dihydrofolate reductase (DHFR), we explored trimethoprim (TMP) as an alternative prokaryote-specific DHFR ligand. MASPIT evaluation of TMP fusion compounds with tamoxifen, reversine, and simvastatin as model baits, resulted in dose-response curves shifted towards lower EC50 values than those of their MTX congeners. Furthermore, a scalable azido-TMP reagent was synthesized that displayed a similar improvement in sensitivity, possibly owing to increased membrane permeability relative to the MTX anchor. Applying the SNAP-tag approach to introduce a covalent bond into the system, on the other hand, produced an inferior readout than in the MTX- or TMP-tag based assay.
authors: Laboratory for Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Gent (Belgium).
authors: Dries J H
authors: DJ
authors: De Clercq
authors: Martijn D P
authors: MD
authors: Risseeuw
authors: Izet
authors: I
authors: Karalic
authors: Anne-Sophie
authors: AS
authors: De Smet
authors: Dieter
authors: D
authors: Defever
authors: Jan
authors: J
authors: Tavernier
authors: Sam
authors: S
authors: Lievens
authors: Serge
authors: S
authors: Van Calenbergh
mesh_terms: D001665:Binding Sites; D057809:HEK293 Cells; D006801:Humans; D007202:Indicators and Reagents / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008727:Methotrexate / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D014295:Trimethoprim / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D007202:Indicators and Reagents; D008024:Ligands; D014295:Trimethoprim; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate
keywords: MASPIT; dimerization; immobilization; target identification; trimethoprim conjugates