| 1. |
- Blokzijl, Andries, et al.
(författare)
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Single Chain Antibodies as Tools to Study transforming growth factor--Regulated SMAD Proteins in Proximity Ligation-Based Pharmacological Screens
- 2016
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 15:6, s. 1848-1856
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Tidskriftsartikel (refereegranskat)abstract
- The cellular heterogeneity seen in tumors, with subpopulations of cells capable of resisting different treatments, renders single-treatment regimens generally ineffective. Accordingly, there is a great need to increase the repertoire of drug treatments from which combinations may be selected to efficiently target sets of pathological processes, while suppressing the emergence of resistance mutations. In this regard, members of the TGF- signaling pathway may furnish new, valuable therapeutic targets. In the present work, we developed in situ proximity ligation assays (isPLA) to monitor the state of the TGF- signaling pathway. Moreover, we extended the range of suitable affinity reagents for this analysis by developing a set of in-vitro-derived human antibody fragments (single chain fragment variable, scFv) that bind SMAD2 (Mothers against decapentaplegic 2), 3, 4, and 7 using phage display. These four proteins are all intracellular mediators of TGF- signaling. We also developed an scFv specific for SMAD3 phosphorylated in the linker domain 3 (p179 SMAD3). This phosphorylation has been shown to inactivate the tumor suppressor function of SMAD3. The single chain affinity reagents developed in the study were fused tocrystallizable antibody fragments (Fc-portions) and expressed as dimeric IgG-like molecules having Fc domains (Yumabs), and we show that they represent valuable reagents for isPLA. Using these novel assays, we demonstrate that p179 SMAD3 forms a complex with SMAD4 at increased frequency during division and that pharmacological inhibition of cyclin-dependent kinase 4 (CDK4)(1) reduces the levels of p179SMAD3 in tumor cells. We further show that the p179SMAD3-SMAD4 complex is bound for degradation by the proteasome. Finally, we developed a chemical screening strategy for compounds that reduce the levels of p179SMAD3 in tumor cells with isPLA as a read-out, using the p179SMAD3 scFv SH544-IIC4. The screen identified two kinase inhibitors, known inhibitors of the insulin receptor, which decreased levels of p179SMAD3/SMAD4 complexes, thereby demonstrating the suitability of the recombinant affinity reagents applied in isPLA in screening for inhibitors of cell signaling.
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| 2. |
- Jarvius, Malin, et al.
(författare)
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In situ detection of phosphorylated platelet-derived growth factor receptor beta using a generalized proximity ligation method
- 2007
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 6:9, s. 1500-1509
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Tidskriftsartikel (refereegranskat)abstract
- Improved methods are needed for in situ characterization of post-translational modifications in cell lines and tissues. For example, it is desirable to monitor the phosphorylation status of individual receptor tyrosine kinases in samples from human tumors treated with inhibitors to evaluate therapeutic responses. Unfortunately the leading methods for observing the dynamics of tissue post-translational modifications in situ, immunohistochemistry and immunofluorescence, exhibit limited sensitivity and selectivity. Proximity ligation assay is a novel method that offers improved selectivity through the requirement of dual recognition and increased sensitivity by including DNA amplification as a component of detection of the target molecule. Here we therefore established a generalized in situ proximity ligation assay to investigate phosphorylation of platelet-derived growth factor receptor β (PDGFRβ) in cells stimulated with platelet-derived growth factor BB. Antibodies specific for immunoglobulins from different species, modified by attachment of DNA strands, were used as secondary proximity probes together with a pair of primary antibodies from the corresponding species. Dual recognition of receptors and phosphorylated sites by the primary antibodies in combination with the secondary proximity probes was used to generate circular DNA strands; this was followed by signal amplification by replicating the DNA circles via rolling circle amplification. We detected tyrosine phosphorylated PDGFRβ in human embryonic kidney cells stably overexpressing human influenza hemagglutinin-tagged human PDGFRβ in porcine aortic endothelial cells transfected with the β-receptor, but not in cells transfected with the α-receptor, and also in immortalized human foreskin fibroblasts, BJ hTert, endogenously expressing the PDGFRβ. We furthermore visualized tyrosine phosphorylated PDGFRβ in tissue sections from fresh frozen human scar tissue undergoing wound healing. The method should be of great value to study signal transduction, screen for effects of pharmacological agents, and enhance the diagnostic potential in histopathology.
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| 3. |
- Leuchowius, Karl-Johan, et al.
(författare)
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High content screening for inhibitors of protein interactions and post-translational modifications in primary cells by proximity ligation
- 2010
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 9:1, s. 178-183
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Tidskriftsartikel (refereegranskat)abstract
- The cost of developing new drugs is a major obstacle for pharmaceutical companies and academia with many drugs identified in the drug discovery process failing approval for clinical use due to lack of intended effect or because of severe side effects. Since the early 1990 s, high throughput screening of drug compounds has increased enormously in capacity but has not resulted in a higher success rate of the identified drugs. Thus, there is a need for methods that can identify biologically relevant compounds and more accurately predict in vivo effects early in the drug discovery process. To address this, we developed a proximity ligation-based assay for high content screening of drug effects on signaling pathways. As a proof of concept, we used the assay to screen through a library of previously identified kinase inhibitors, including six clinically used tyrosine kinase inhibitors, to identify compounds that inhibited the platelet-derived growth factor (PDGF) receptor beta signaling pathway in stimulated primary human fibroblasts. Thirteen of the 80 compounds were identified as hits, and the dose responses of these compounds were measured. The assay exhibited a very high Z' factor (0.71) and signal to noise ratio (11.7), demonstrating excellent ability to identify compounds interfering with the specific signaling event. A comparison with regular immunofluorescence detection of phosphorylated PDGF receptor demonstrated a far superior ability by the in situ proximity ligation assay to reveal inhibition of receptor phosphorylation. In addition, inhibitor-induced perturbation of protein-protein interactions of the PDGF signaling pathway could be quantified, further demonstrating the usefulness of the assay in drug discovery.
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| 4. |
- Leuchowius, Karl-Johan, et al.
(författare)
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Parallel Visualization of Multiple Protein Complexes in Individual Cells in Tumor Tissue
- 2013
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 12:6, s. 1563-1571
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Tidskriftsartikel (refereegranskat)abstract
- Cellular functions are regulated and executed by complex protein interaction networks. Accordingly, it is essential to understand the interplay between proteins in determining the activity status of signaling cascades. New methods are therefore required to provide information on different protein interaction events at the single cell level in heterogeneous cell populations such as in tissue sections. Here, we describe a multiplex proximity ligation assay for simultaneous visualization of multiple protein complexes in situ. The assay is an enhancement of the original proximity ligation assay, and it is based on using proximity probes labeled with unique tag sequences that can be used to read out which probes, from a pool of probes, have bound a certain protein complex. Using this approach, it is possible to gain information on the constituents of different protein complexes, the subcellular location of the complexes, and how the balance between different complex constituents can change between normal and malignant cells, for example. As a proof of concept, we used the assay to simultaneously visualize multiple protein complexes involving EGFR, HER2, and HER3 homo- and heterodimers on a single-cell level in breast cancer tissue sections. The ability to study several protein complex formations concurrently at single cell resolution could be of great potential for a systems understanding, paving the way for improved disease diagnostics and possibilities for drug development.
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| 5. |
- Liu, Yanling, et al.
(författare)
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Western Blotting via Proximity Ligation for High Performance Protein Analysis
- 2011
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 10:11, s. O111.011031-
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Tidskriftsartikel (refereegranskat)abstract
- Western blotting is a powerful and widely used method, but limitations in detection sensitivity and specificity, and dependence upon high quality antibodies to detect targeted proteins, are hurdles to overcome. The in situ proximity ligation assay, based on dual antibody recognition and powerful localized signal amplification, offers increased detection sensitivity and specificity, along with an ability to identify complex targets such as phosphorylated or interacting proteins. Here we have applied the in situ proximity ligation assay mechanism in Western blotting. This combination allowed the use of isothermal rolling circle amplification of DNA molecules formed in target-specific ligation reaction, for 16-fold or greater increase in detection sensitivity. The increased specificity because of dual antibody recognition ensured highly selective assays, detecting the specific band when combinations of two cross-reactive antitubulin antibodies were used (i.e. both producing distinct nonspecific bands in traditional Western blotting). We also demonstrated detection of phosphorylated platelet-derived growth factor receptor beta by proximity ligation with one antibody directed against the receptor and another directed against the phosphorylated tyrosine residue. This avoided the need for stripping and re-probing the membrane or aligning two separate traditional blots. We demonstrate that the high-performance in situ proximity ligation-based Western blotting described herein is compatible with detection via enhanced chemiluminescence and fluorescence detection systems, and can thus be readily employed in any laboratory.
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| 6. |
- Zieba, Agata, et al.
(författare)
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Intercellular variation in signaling through the TGF-β pathway and its relation to cell densityand cell cycle phase
- 2012
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Ingår i: Molecular & Cellular Proteomics. - : American Society for Biochemistry and Molecular Biology. - 1535-9476 .- 1535-9484. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- Fundamental open questions in signal transduction remain concerning the sequence and distribution of molecular signaling events among individual cells. In this work we have characterized the intercellular variability of transforming growth factor β-induced Smad interactions, providing essential information about TGF-β signaling and its dependence on the density of cell populations and the cell-cycle phase. By employing the recently developed in situ proximity ligation assay, we investigated the dynamics of interactions and modifications of Smad proteins and their partners under native and physiological conditions. We analyzed the kinetics of assembly of Smad complexes and the influence of cellular environment and relation to mitosis. We report rapid kinetics of formation of Smad complexes, including native Smad2-Smad3-Smad4 trimeric complexes, in a manner influenced by the rate of proteasomal degradation of these proteins, and we found a striking cell to cell variation of signaling complexes. The single-cell analysis of TGF-β signaling in genetically unmodified cells revealed previously unknown aspects of regulation of this pathway, and it provided a basis for analysis of these signaling events to diagnose pathological perturbations in patient samples, and to evaluate their susceptibility to drug treatment.
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