| 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. |
- Jaud, Simon, et al.
(författare)
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Insertion of short transmembrane helices by the Sec61 translocon
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:28, s. 11588-11593
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Tidskriftsartikel (refereegranskat)abstract
- The insertion efficiency of transmembrane (TM) helices by the Sec61 translocon depends on helix amino acid composition, the positions of the amino acids within the helix, and helix length. We have used an in vitro expression system to examine systematically the insertion efficiency of short polyleucine segments (L(n), n = 4 ... 12) flanked at either end by 4-residue sequences of the form XXPX-L(n)-XPXX with X = G, N, D, or K. Except for X = K, insertion efficiency (p) is <10% for n < 8, but rises steeply to 100% for n = 12. For X = K, p is already close to 100% for n = 10. A similar pattern is observed for synthetic peptides incorporated into oriented phospholipid bilayer arrays, consistent with the idea that recognition of TM segments by the translocon critically involves physical partitioning of nascent peptide chains into the lipid bilayer. Molecular dynamics simulations suggest that insertion efficiency is determined primarily by the energetic cost of distorting the bilayer in the vicinity of the TM helix. Very short lysine-flanked leucine segments can reduce the energetic cost by extensive hydrogen bonding with water and lipid phosphate groups (snorkeling) and by partial unfolding.
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| 3. |
- 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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| 4. |
- Ostuni, A., et al.
(författare)
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The hepatitis B x antigen anti-apoptotic effector URG7 is localized to the endoplasmic reticulum membrane
- 2013
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 587:18, s. 3058-3062
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Tidskriftsartikel (refereegranskat)abstract
- Hepatitis B x antigen up-regulates the liver expression of URG7 that contributes to sustain chronic virus infection and to increase the risk for hepatocellular carcinoma by its anti-apoptotic activity. We have investigated the subcellular localization of URG7 expressed in HepG2 cells and determined its membrane topology by glycosylation mapping in vitro. The results demonstrate that URG7 is N-glycosylated and located to the endoplasmic reticulum membrane with an N-lumen-C-cytosol orientation. The results imply that the anti-apoptotic effect of URG7 could arise from the C-terminal cytosolic tail binding a pro-apoptotic signaling factor and retaining it to the endoplasmic reticulum membrane.
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| 5. |
- Dowaidar, Moataz
(författare)
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In-silico design of peptide-based transfection systems, in-vitro validation, and up-take pathways investigation
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cell-penetrating peptide-based transfection systems (PBTS) are a promising group of drug delivery vectors. Cell-penetrating peptides (CPPs) are short cationic peptides that are able of transporting cell non-permeant cargos into different cell types. Some CPPs can be used to form non-covalent complexes with oligonucleotides for gene delivery applications. For the potential use of CPPs as drug delivery tools, it is important to understand the mechanism of uptake. Here, a fragment quantitative structure–activity relationships (FQSAR) model is generated to predict novel peptides based on approved alpha helical conformers and assisted model construction with energy refinement molecular mechanics simulations of former peptides. The modeled peptides were examined for plasmid transfection efficiency and compared with their predicted biological activity. The best predicted peptides were efficient for plasmid transfection with significant enhancement compared to the former group of peptides. Our results confirm that FQSAR model refinement is an efficient method for optimizing PBTS for improved biological activity. Additionally, using RNA sequencing, we demonstrated the involvement of autophagy pathways in PBTS uptake.
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| 6. |
- Lee, Hunsang, et al.
(författare)
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Live-cell topology assessment of URG7, MRP6(102) and SP-C using glycosylatable green fluorescent protein in mammalian cells
- 2014
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 450:4, s. 1587-1592
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Tidskriftsartikel (refereegranskat)abstract
- Experimental tools to determine membrane topology of a protein are rather limited in higher eukaryotic organisms. Here, we report the use of glycosylatable GFP (gGFP) as a sensitive and versatile membrane topology reporter in mammalian cells. gGFP selectively loses its fluorescence upon N-linked glycosylation in the ER lumen. Thus, positive fluorescence signal assigns location of gGFP to the cytosol whereas no fluorescence signal and a glycosylated status of gGFP map the location of gGFP to the ER lumen. By using mammalian gGFP, the membrane topology of disease-associated membrane proteins, URG7, MRP6(102), SP-C(Val) and SP-C(Leu) was confirmed. URG7 is partially targeted to the ER, and inserted in C-in, form. MRP6(102) and SP-C(Leu/Val) are inserted into the membrane in C-out form. A minor population of untargeted SP-C is removed by proteasome dependent quality control system.
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| 7. |
- Lundin, Carolina, et al.
(författare)
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Membrane topology of the Drosophila OR83b odorant receptor
- 2007
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 581:29, s. 5601-5604
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Tidskriftsartikel (refereegranskat)abstract
- By analogy to mammals, odorant receptors (ORs) in insects, such as Drosophila melanogaster, have long been thought to belong to the G-protein coupled receptor (GPCR) superfamily. However, recent work has cast doubt on this assumption and has tentatively suggested an inverted topology compared to the canonical N(out) - C(in) 7 transmembrane (TM) GPCR topology, at least for some Drosophila ORs. Here, we report a detailed topology mapping of the Drosophila OR83b receptor using engineered glycosylation sites as topology markers. Our results are inconsistent with a classical GPCR topology and show that OR83b has an intracellular N-terminus, an extracellular C-terminus, and 7TM helices.
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| 8. |
- Öjemalm, Karin, et al.
(författare)
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Apolar surface area determines the efficiency of translocon-mediated membrane-protein integration into the endoplasmic reticulum
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:31, s. E359-E364
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Tidskriftsartikel (refereegranskat)abstract
- Integral membrane proteins are integrated cotranslationally into the membrane of the endoplasmic reticulum in a process mediated by the Sec61 translocon. Transmembrane α-helices in a translocating polypeptide chain gain access to the surrounding membrane through a lateral gate in the wall of the translocon channel [van den Berg B, et al. (2004) Nature427:36–44; Zimmer J, et al. (2008) Nature455:936–943; Egea PF, Stroud RM (2010)Proc Natl Acad Sci USA 107:17182–17187]. To clarify the nature of the membrane-integration process, we have measured the insertion efficiency into the endoplasmic reticulum membrane of model hydrophobic segments containing nonproteinogenic aliphatic and aromatic amino acids. We find that an amino acid’s contribution to the apparent free energy of membrane-insertion is directly proportional to the nonpolar accessible surface area of its side chain, as expected for thermodynamic partitioning between aqueous and nonpolar phases. But unlike bulk-phase partitioning, characterized by a nonpolar solvation parameter of 23 cal∕ðmol · Å2Þ, the solvation parameter for transfer from translocon to bilayer is 6 –10 cal∕ðmol · Å2Þ, pointing to important differences between translocon-guided partitioning and simple water-to-membrane partitioning. Our results provide compelling evidence for a termodynamic partitioning model and insights into the physical properties of the translocon.
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| 9. |
- 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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| 10. |
- Gadalla, Salah-Eldin, et al.
(författare)
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EpCAM associates with endoplasmic reticulum aminopeptidase 2 (ERAP2) in breast cancer cells
- 2013
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 439:2, s. 203-208
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Tidskriftsartikel (refereegranskat)abstract
- Epithelial cell adhesion molecule (EpCAM) is an epithelial and cancer cell marker and there is a cumulative and growing evidence of its signaling role. Its importance has been recognized as part of the breast cancer stem cell phenotype, the tumorigenic breast cancer stem cell is EpCAM(+). In spite of its complex functions in normal cell development and cancer, relatively little is known about EpCAM-interacting proteins. We used breast cancer cell lines and performed EpCAM co-immunoprecipitation followed by mass spectrometry in search for novel potentially interacting proteins. The endoplasmic reticulum aminopeptidase 2 (ERAP2) was found to co-precipitate with EpCAM and to co-localize in the cytoplasm/ER and the plasma membrane. ERAP2 is a proteolytic enzyme set in the endoplasmic reticulum (ER) where it plays a central role in the trimming of peptides for presentation by MHC class I molecules. Expression of EpCAM and ERAP2 in vitro in the presence of dog pancreas rough microsomes (ER vesicles) confirmed N-linked glycosylation, processing in ER and the size of EpCAM. The association between ERAP2 and EpCAM is a unique and novel finding that provides new ideas on EpCAM processing and on how antigen presentation may be regulated in cancer.
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