title: A high-throughput screen for identification of molecular mimics of Smac/DIABLO utilizing a fluorescence polarization assay.
abstract: Resistance to apoptosis is afforded by inhibitor of apoptosis proteins (IAPs) which bind to and inhibit the caspases responsible for cleavage of substrates leading to apoptotic cell death. Smac (or DIABLO), a proapoptotic protein released from the mitochondrial intermembrane space into the cytosol, promotes apoptosis by binding to IAPs, thus reversing their inhibitory effects on caspases. We have developed a high-throughput fluorescence polarization assay utilizing a fluorescein-labeled peptide similar to the "IAP binding" domain of Smac N terminus complexed with the BIR3 domain of X-linked IAP (XIAP) to identify small-molecule mimics of the action of Smac. The IC(50)s of peptides and a tetrapeptidomimetic homologous to the N terminus of Smac demonstrated the specificity and utility of this assay. We have screened the National Cancer Institute "Training Set" of 230 compounds, with well-defined biological actions, and the "Diversity Set" of 2000 chemically diverse structures for compounds which significantly reduced fluorescence polarization. Highly fluorescing or fluorescence-quenching compounds (false positives) were distinguished from those which interfered with Smac peptide binding to the XIAP-BIR3 in a dose-dependent manner (true positives). This robust assay offers potential for high-throughput screening discovery of novel compounds simulating the action of Smac/DIABLO.
authors.affiliation: Developmental Therapeutics Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA. cglover@mail.ncifcrf.gov
authors.forename: Constance J
authors.initials: CJ
authors.lastname: Glover
authors.forename: Karen
authors.initials: K
authors.lastname: Hite
authors.forename: Renee
authors.initials: R
authors.lastname: DeLosh
authors.forename: Dominic A
authors.initials: DA
authors.lastname: Scudiero
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Fivash
authors.forename: Lindsey R
authors.initials: LR
authors.lastname: Smith
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fisher
authors.forename: Jia Wei
authors.initials: JW
authors.lastname: Wu
authors.forename: Yigong
authors.initials: Y
authors.lastname: Shi
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Kipp
authors.forename: George L
authors.initials: GL
authors.lastname: McLendon
authors.forename: Edward A
authors.initials: EA
authors.lastname: Sausville
authors.forename: Robert H
authors.initials: RH
authors.lastname: Shoemaker
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002623:Chemistry Techniques, Analytical; D005454:Fluorescence Polarization; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding
chemical_list: D002352:Carrier Proteins; D024101:Mitochondrial Proteins; D010455:Peptides