| 1. |
- Ch'ng, Jun-Hong, et al.
(författare)
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Epitopes of anti-RIFIN antibodies and characterization of rif-expressing Plasmodium falciparum parasites by RNA sequencing
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Variable surface antigens of Plasmodium falciparum have been a major research focus since they facilitate parasite sequestration and give rise to deadly malaria complications. Coupled with its potential use as a vaccine candidate, the recent suggestion that the repetitive interspersed families of polypeptides (RIFINs) mediate blood group A rosetting and influence blood group distribution has raised the research profile of these adhesins. Nevertheless, detailed investigations into the functions of this highly diverse multigene family remain hampered by the limited number of validated reagents. In this study, we assess the specificities of three promising polyclonal anti-RIFIN antibodies that were IgG-purified from sera of immunized animals. Their epitope regions were mapped using a 175,000-peptide microarray holding overlapping peptides of the P. falciparum variable surface antigens. Through immunoblotting and immunofluorescence imaging, we show that different antibodies give varying results in different applications/assays. Finally, we authenticate the antibody-based detection of RIFINs in two previously uncharacterized non-rosetting parasite lines by identifying the dominant rif transcripts using RNA sequencing.
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| 2. |
- Orlova, Anna, et al.
(författare)
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Tumor imaging using a picomolar affinity HER2 binding affibody molecule
- 2006
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Ingår i: Cancer Research. - 0008-5472 .- 1538-7445. ; 66:8, s. 4339-48
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Tidskriftsartikel (refereegranskat)abstract
- The detection of cell-bound proteins that are produced due to aberrant gene expression in malignant tumors can provide important diagnostic information influencing patient management. The use of small radiolabeled targeting proteins would enable high-contrast radionuclide imaging of cancers expressing such antigens if adequate binding affinity and specificity could be provided. Here, we describe a HER2-specific 6 kDa Affibody molecule (hereinafter denoted Affibody molecule) with 22 pmol/L affinity that can be used for the visualization of HER2 expression in tumors in vivo using gamma camera. A library for affinity maturation was constructed by re-randomization of relevant positions identified after the alignment of first-generation variants of nanomolar affinity (50 nmol/L). One selected Affibody molecule, Z(HER2:342) showed a >2,200-fold increase in affinity achieved through a single-library affinity maturation step. When radioiodinated, the affinity-matured Affibody molecule showed clear, high-contrast visualization of HER2-expressing xenografts in mice as early as 6 hours post-injection. The tumor uptake at 4 hours post-injection was improved 4-fold (due to increased affinity) with 9% of the injected dose per gram of tissue in the tumor. Affibody molecules represent a new class of affinity molecules that can provide small sized, high affinity cancer-specific ligands, which may be well suited for tumor imaging.
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| 3. |
- Andersson, Annika, et al.
(författare)
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Membrane integration and topology of RIFIN and STEVOR proteins of the Plasmodium falciparum parasite
- 2020
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 287:13, s. 2744-2762
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Tidskriftsartikel (refereegranskat)abstract
- The malarial parasite Plasmodium exports its own proteins to the cell surfaces of red blood cells (RBCs) during infection. Examples of exported proteins include members of the repetitive interspersed family (RIFIN) and subtelomeric variable open reading frame (STEVOR) family of proteins from Plasmodium falciparum. The presence of these parasite-derived proteins on surfaces of infected RBCs triggers the adhesion of infected cells to uninfected cells (rosetting) and to the vascular endothelium potentially obstructing blood flow. While there is a fair amount of information on the localization of these proteins on the cell surfaces of RBCs, less is known about how they can be exported to the membrane and the topologies they can adopt during the process. The first step of export is plausibly the cotranslational insertion of proteins into the endoplasmic reticulum (ER) of the parasite, and here, we investigate the insertion of three RIFIN and two STEVOR proteins into the ER membrane. We employ a well-established experimental system that uses N-linked glycosylation of sites within the protein as a measure to assess the extent of membrane insertion and the topology it assumes when inserted into the ER membrane. Our results indicate that for all the proteins tested, transmembranes (TMs) 1 and 3 integrate into the membrane, so that the protein assumes an overall topology of Ncyt-Ccyt. We also show that the segment predicted to be TM2 for each of the proteins likely does not reside in the membrane, but is translocated to the lumen.
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| 4. |
- Bañó-Polo, Manuel, et al.
(författare)
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Transmembrane but not soluble helices fold inside the ribosome tunnel
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Integral membrane proteins are assembled into the ER membrane via a continuous ribosome-translocon channel. The hydrophobicity and thickness of the core of the membrane bilayer leads to the expectation that transmembrane (TM) segments minimize the cost of harbouring polar polypeptide backbones by adopting a regular pattern of hydrogen bonds to form a-helices before integration. Co-translational folding of nascent chains into an a-helical conformation in the ribosomal tunnel has been demonstrated previously, but the features governing this folding are not well understood. In particular, little is known about what features influence the propensity to acquire a-helical structure in the ribosome. Using in vitro translation of truncated nascent chains trapped within the ribosome tunnel and molecular dynamics simulations, we show that folding in the ribosome is attained for TM helices but not for soluble helices, presumably facilitating SRP (signal recognition particle) recognition and/or a favourable conformation for membrane integration upon translocon entry.
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| 5. |
- Cuviello, Flavia, et al.
(författare)
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Membrane insertion and topology of the amino-terminal domain TMD0 of multidrug-resistance associated protein 6 (MRP6)
- 2015
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 589:24, s. 3921-3928
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Tidskriftsartikel (refereegranskat)abstract
- The function of the ATP-binding cassette transporter MRP6 is unknown but mutations in its gene cause pseudoxanthoma elasticum. We have investigated the membrane topology of the N-terminal transmembrane domain TMD0 of MRP6 and the membrane integration and orientation propensities of its transmembrane segments (TMs) by glycosylation mapping. Results demonstrate that TMD0 has five TMs, an Nout-Cin topology and that the less hydrophobic TMs have strong preference for their orientation in the membrane that affects the neighboring TMs. Two disease-causing mutations changing the number of positive charges in the loops of TMD0 did not affect the membrane insertion efficiencies of the adjacent TMs.
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| 6. |
- Enquist, Karl, et al.
(författare)
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Membrane-integration characteristics of two ABC transporters, CFTR and P-glycoprotein
- 2009
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 387:5, s. 1153-1164
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Tidskriftsartikel (refereegranskat)abstract
- To what extent do corresponding transmembrane helices in related integral membrane proteins have different membrane-insertion characteristics? Here, we compare, side-by-side, the membrane insertion characteristics of the 12 transmembrane helices in the adenosine triphosphate-binding cassette (ABC) transporters, P-glycoprotein (P-gp) and the cystic fibrosis transmembrane conductance regulator (CFTR). Our results show that 10 of the 12 CFTR transmembrane segments can insert independently into the ER membrane. In contrast, only three of the P-gp transmembrane segments are independently stable in the membrane, while the majority depend on the presence of neighboring loops and/or transmembrane segments for efficient insertion. Membrane-insertion characteristics can thus vary widely between related proteins.
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| 7. |
- Fagerberg, Linn, et al.
(författare)
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Analysis of the human tissue-specific expression by genome-wide integration of transcriptomics and antibody-based proteomics
- 2014
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 13:2, s. 397-406
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Tidskriftsartikel (refereegranskat)abstract
- Global classification of the human proteins with regards to spatial expression patterns across organs and tissues is important for studies of human biology and disease. Here, we used a quantitative transcriptomics analysis (RNA-Seq) to classify the tissue-specific expression of genes across a representative set of all major human organs and tissues and combined this analysis with antibody- based profiling of the same tissues. To present the data, we launch a new version of the Human Protein Atlas that integrates RNA and protein expression data corresponding to 80% of the human protein-coding genes with access to the primary data for both the RNA and the protein analysis on an individual gene level. We present a classification of all human protein-coding genes with regards to tissue-specificity and spatial expression pattern. The integrative human expression map can be used as a starting point to explore the molecular constituents of the human body.
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| 8. |
- Fagerberg, Linn, et al.
(författare)
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Contribution of antibody-based protein profiling to the human chromosome-centric proteome project (C-HPP)
- 2013
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 12:6, s. 2439-2448
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Tidskriftsartikel (refereegranskat)abstract
- A gene-centric Human Proteome Project has been proposed to characterize the human protein-coding genes in a chromosome-centered manner to understand human biology and disease. Here, we report on the protein evidence for all genes predicted from the genome sequence based on manual annotation from literature (UniProt), antibody-based profiling in cells, tissues and organs and analysis of the transcript profiles using next generation sequencing in human cell lines of different origins. We estimate that there is good evidence for protein existence for 69% (n = 13985) of the human protein-coding genes, while 23% have only evidence on the RNA level and 7% still lack experimental evidence. Analysis of the expression patterns shows few tissue-specific proteins and approximately half of the genes expressed in all the analyzed cells. The status for each gene with regards to protein evidence is visualized in a chromosome-centric manner as part of a new version of the Human Protein Atlas (www.proteinatlas.org).
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| 9. |
- Friedman, Mikaela, et al.
(författare)
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Directed evolution to low nanomolar affinity of a tumor-targeting epidermal growth factor receptor-binding affibody molecule
- 2008
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 376:5, s. 1388-1402
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Tidskriftsartikel (refereegranskat)abstract
- The epidermal growth factor receptor 1 (EGFR) is overexpressed in various malignancies and is associated with a poor patient prognosis. A small, receptor-specific, high-affinity imaging agent would be a useful tool in diagnosing malignant tumors and in deciding upon treatment and assessing the response to treatment. We describe here the affinity maturation procedure for the generation of Affibody molecules binding with high affinity and specificity to EGFR. A library for affinity maturation was constructed by rerandomization of selected positions after the alignment of first-generation binding variants. New binders were selected with phage display technology, using a single oligonucleotide in a single-library effort, and the best second-generation binders had an approximately 30-fold improvement in affinity (K(d)=5-10 nM) for the soluble extracellular domain of EGFR in biospecific interaction analysis using Biacore. The dissociation equilibrium constant, K(d), was also determined for the Affibody with highest affinity using EGFR-expressing A431 cells in flow cytometric analysis (K(d)=2.8 nM). A retained high specificity for EGFR was verified by a dot blot assay showing staining only of EGFR proteins among a panel of serum proteins and other EGFR family member proteins (HER2, HER3, and HER4). The EGFR-binding Affibody molecules were radiolabeled with indium-111, showing specific binding to EGFR-expressing A431 cells and successful targeting of the A431 tumor xenografts with 4-6% injected activity per gram accumulated in the tumor 4 h postinjection.
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| 10. |
- Friedman, Mikaela, et al.
(författare)
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Phage display selection of Affibody molecules with specific binding to the extracellular domain of the epidermal growth factor receptor
- 2007
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Ingår i: Protein Engineering Design & Selection. - : Oxford University Press (OUP). - 1741-0126 .- 1741-0134. ; 20:4, s. 189-199
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Tidskriftsartikel (refereegranskat)abstract
- Affibody molecules specific for the epidermal growth factor receptor (EGFR) have been selected by phage display technology from a combinatorial protein library based on the 58-residue, protein A-derived Z domain. EGFR is overexpressed in various malignancies and is frequently associated with poor patient prognosis, and the information provided by targeting this receptor could facilitate both patient diagnostics and treatment. Three selected Affibody variants were shown to selectively bind to the extracellular domain of EGFR (EGFR-ECD). Kinetic biosensor analysis revealed that the three monomeric Affibody molecules bound with similar affinity, ranging from 130 to 185 nM. Head-to-tail dimers of the Affibody molecules were compared for their binding to recombinant EGFR-ECD in biosensor analysis and in human epithelial cancer A431 cells. Although the dimeric Affibody variants were found to bind in a range of 25-50 nM affinities in biosensor analysis, they were found to be low nanomolar binders in the cellular assays. Competition assays using radiolabeled Affibody dimers confirmed specific EGFR-binding and demonstrated that the three Affibody molecules competed for the same epitope. Immunofluorescence microscopy demonstrated that the selected Affibody dimers were initially binding to EGFR at the cell surface of A431, and confocal microscopy analysis showed that the Affibody dimers could thereafter be internalized. The potential use of the described Affibody molecules as targeting agents for radionuclide based imaging applications in various carcinomas is discussed.
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