Synthesis and evaluation of cell-permeable biotinylated PU-H71 derivatives as tumor Hsp90 probes

The attachment of biotin to a small molecule provides a powerful tool in biology. Here, we present a systematic approach to identify biotinylated analogues of the Hsp90 inhibitor PU-H71 that are capable of permeating cell membranes so as to enable the investigation of Hsp90 complexes in live cells. The identified derivative 2g can isolate Hsp90 through affinity purification and, as we show, represents a unique and useful tool to probe tumor Hsp90 biology in live cells by affinity capture, flow cytometry and confocal microscopy. To our knowledge, 2g is the only reported biotinylated Hsp90 probe to have such combined characteristics.

Synthesis of purine-scaffold fluorescent probes for heat shock protein 90 with use in flow cytometry and fluorescence microscopy

Fluorescent ligands for the heat shock protein 90 (Hsp90) were synthesized containing either fluorescein isothiocyanate (FITC), 4-nitrobenzo[1,2,5]oxadiazole (NBD) or the red shifted dye sulforhodamine 101 (Texas Red) conjugated to PU-H71. Two of the compounds, PU-H71-FITC2 (9) and PU-H71-NBD1 (8), were shown to be suitable for fluorescence-activated flow cytometry and fluorescence microscopy. Thus these molecules serve as useful probes for studying Hsp90 in heterogeneous live cell populations.