FRAUNHOFER IME SCREENINGPORT

Transcription

1 FRAUNHOFER IME SCREENINGPORT Detection technologies used in drug discovery

2 Introduction Detection technologies in drug discovery is unlimited only a biased snapshot can be presented Differences can presented based on high- vs. low-throughput, labeled vs. label-free, cell-based vs. cell-free, target centered vs. high content Classical detection technologies in high throughput screening include TR-FRET, Alpha-Screen, Luminescence, Fluorescence, Imaging Interesting assays are needed for target deconvolution

3 TR-FRET and AlphaScreen Biotinylated D2 conjugated to streptavidin Excitation at 680nm AlphaScreen Nickel donor bead Protein I FRET at 615nm Emission at 665nm 1 O 2 Eu-labeled Protein II Fc-chimera of Protein II AlphaScreen Protein A acceptor bead Excitation at 320nm Emission at 620nm Both assay systems require labeling Will be presented in a case study, too

4 Evolution of Luciferases Luciferases were used as reporters in reportergene assays or in assays wich are connected to ATP concentrations (Kinases, viability)

5 Example of imageing and image analysis Nuclei channel Nuclei Class A Nuclei Class B There are no limits, but dedicated software is needed

6 Methods For Analysis of Protein Protein Interactions Method Quantitative Pulldown Mass spec Real time Live cell Localisation Multiplex HTS No No No Limited No Limited Yes Yes Limited No No Yes No No No Yes Limited Limited SILAC SPR Yes No No No Yes Limited PCA (protein complementation) Calorimetry Fluorescence Correlation Spectroscopy No No No No Yes No Yes Yes Limited No No No FRET Yes Yes Yes No No Limited TR-FRET Yes No No No No Yes BRET Yes Yes Limited No No Yes

7 How does BRET work? BRET is like FRET, but with an internal light source The energy transfer is radiation-free (quantum effect, similar to FRET)

8 NanoBRET from Promega Previous BRET efficiency Only the newly developed BRET system by Promega allows good sensitivity and a high dynamic range

9 Validity of the BRET assay system Sensitivity and dynamic range are good These are mandatory controls which should be checked for every similar assay system

10 Scheme of constructs which have to be cloned It is essential to try all the possible combinations (8 constructs needed) Tagging could easily interfere with the function or the localisation

11 Protein complementation assay It started with complementation of enzyme (e.g. ß-lactamase) similar to yeast-2-hybrid Complementation of fluorescence proteins (GFP) results in crosslinking of the partners Luciferase is much faster and easy to detect

12 Yeast -3-hybrid assay Medicinal chemistry is needed A technology to screen for hundreds of binding partners G.C. Terstappen et al., Nat. Rev. Drug Disc. 2007, 6,

13 3 short case studies 3 short case studies to demonstrate technologies in more detail Focus on biochemical suppression, Pulldown analysis and Proximity ligation technology

14 Identification of a micromolar inhibitor by biochemical suppression Inhibitor with wnt protein (in media) EC50 of 3.9±0.07µM Low micromolar inhibitor of the wnt pathway with a decaline core structure

15 Reducing the number of possible targets Inhibitor with Li (similar results with selective GSK inhibitors) SR56 vs Lithium Luciferase Aktivität Konzentration SR56 in µm EC50 of 2.7±0.04µM Inhibition not upstream of GSK-3ß

16 Reducing the number of possible targets compound β-catenin medium Wnt3a control 2 µm 4 µm 6 µm 8 µm α-tubulin? Western blot in SW480 cell line (colon cancer) Inhibition not upstream of GSK-3ß and not at the level of Axin

17 Principle of biochemical suppression assay G.C. Terstappen et al., Nat. Rev. Drug Disc. 2007, 6,

18 Application of biochemical suppression assay Wnt3a control cytosol fraction nuclear fraction β-catenin α-tubulin Compound was used at EC 50 concentration Activity is retained if incubated with cytosolic fraction Decalin compound is bound by a protein of the nucleus fraction Nuclear envelope was removed during fractionation process

19 rel. amount of ß-catenin (%) rel. amount of ß-catenin (%) Detailed analysis of an oxepane activator via Pulldown compound β-catenin Wnt3a control 4 µm 8 µm 12 µm 16 µm α-tubulin H N O O O H O H N H O H Wnt3a wnt 4 µm 8 µm 12 12µM µm 16 µm Activity could be verified using Hek293 cell line SAR relationship was developed and affinity probe was synthesised

20 Affinity based target deconvolution Streptavidin magnetic beads Release by heating Biotinylated inhibitor washing Mixture of proteins

21 Affinity based target deconvolution Comparison variant was used 75 mm MgCl 2 was used for affinity purification, as 100 mm MgCl 2 was to stringent and 50 mm MgCl 2 resulted in too many identified proteins 5 affinity purifications were analysed 9 proteins were identified (3 out of 5) proteins identified probe specific proteins 100 mm MgCl 2 75 mm MgCl 2 50 mm MgCl

22 Pescadillo first identified protein wnt dependent phenotype (noncanonical) Pescadillo links Ribosome biogenesis to cancer and chomosomal stability function: Ribosome assembly non-canonical wnt signalling emryonic development / cell migration cell growth control / DNA replication X. laevis embryo treated with Pescadillo sirna cytoplasm nucleolus nucleus

23 wnt dependent phenotype (noncanonical) Van Gogh like-2 is a receptor of wnt signaling responsible for cell polarity Further textual evidence supports this finding

24 Introduction into Proximity ligation technology Detection and quantification of selective proteins, protein modifications or proteinprotein interactions Detection of proteins or modifications in close proximity (< 40 nm) Procedure: Preparation of cellular samples (fixation, permeabilization, blocking) Target detection using primary antibodies (A.) Addition of secondary antibodies, conjugated with oligonucleotide sequences (B.) Ligation of oligonucleotide sequences by the addition of two oligonucleotide sequences and a Ligase (C.) Amplification of PLA signal by rolling circle amplification (D.)

25 Workflow and miniaturisation Cell culture and compound treatment Fixation / Blocking Fixation: 10 µl/well; 30 min RT Blocking: 50 µl/well; 45 min 37 C Primary antibodies PLA protocol Counter staining 20 µl/well; o/n 4 C PLA probes: 10 µl/well; 1 h 37 C Ligation: 10 µl/well; 30 min 37 C Amp.: 10 µl/well; 100 min 37 C Counter stain for nucleus, cytopl. Every arrow includes a washing step Plate format: 384-well plates Image aquisition: images/well

26 reduction of spot density [%] reduction of spot density [%] PLA technology for relative activity assessment Log 10 [c68] (M) Log 10 [c61] (M) PLA used for activity assessment in a cellular enviroment PLA can also be used in tissue slices and with endogenous levels of proteins

27 PLA technology in tissue PLA performed on primary mouse hippocampal tissue to analyse recetor activation in 4% of cells the molecule is located in the nucleus Tissue PLA established by our academic partner Thomas Theis (AG Biosynthesis of Neural Structures, Center for Molecular Neurobiology Hamburg)