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- Fagerberg, Linn, et al.
(författare)
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The Global Protein Expression Pattern in Human Cell Lines
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Human cancer cell lines grown in vitro are frequently used to decipher basic cell biological phenomena but also to specifically study different forms of cancer. Here we present the first large-scale study of protein expression patterns in cell lines using an antibody-based proteomics approach. We analyzed the expression pattern of 5436 proteins in 45 different cell lines using hierarchical clustering, principal component analysis and two-group comparisons for the identification of differentially expressed proteins. The results show that protein profiles of cell lines, as determined using immunohistochemistry, allow for a hierarchical clustering that overall reflects tumor tissues of origin. Hematological cell lines appear to retain their protein profiles to a higher degree than cell lines established from solid tumors, resulting in a clustering that well reflects progenitor cell types. The discrepancy may reflect different levels of in vitro induced alterations in adherent and suspension grown cell lines, respectively. In addition, multiple myeloma cells and cells of myeloid origin were found to share a protein profile, relative the protein profile of lymphoid leukemia and lymphoma cells, possibly reflecting their common dependency of bone marrow microenvironment.
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- Hu, Francis Jingxin, 1986-, et al.
(författare)
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SPUX - A Solid Phase Uracil Excision Method for Antibody Affinity Maturation and Paratope Mapping
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Mutagenesis libraries are the heart of combinatorial protein engineering where proteins such as antibodies are evolved for improved functionality. Despite recent improvements in gene synthesis and selection methodologies, current methods still fail to provide practical means for synthesis of complete antibody scFv and screening of theoretical diversities, hence forcing the user to focused diversity screening and assembly of shorter oligos to avoid synthesis errors and maximize library functionality. Here we demonstrate a way to generate highly functional tailored mutagenesis libraries for efficient antibody affinity maturation using a rapid cell-free solid phase cloning method with single strand diversity oligonucleotides. For this we are utilizing a combination of a high-fidelity polymerase for PCR-based incorporation of Uracil into a wild-type template, bead-based solid-phase technology for elution of single strand DNA, oligonucleotide annealing, extension and automation, and an uracil excision enzyme cocktail for in vitro degradation of template DNA to minimize background. Our method allowed for fast (8 hours) mutagenesis and automated cloning of a complete set of 50 position specific alanine-mutations for mapping of the paratope of a scFv antibody in a single robot run. We further exemplify our method by generating and stratifying a set of antibody scFv affinity maturation libraries with targeted diversity into critical or nonessential paratope positions, as well as by a complete randomization in all positions. The libraries were subjected to bacterial surface display selections and output was followed by Illumina deep sequencing and binding analysis by SPR. The functional quality of our libraries were high, with a yield of >99% functional diversity in the case for two of our libraries. We were further able to target all positions in all loops with diversity, and we could show the ability to target all six loops with diversity at the same time. The comparison of different library focus showed us that scFv libraries with diversity targeted to non-essential enhancing paratope positions more quickly rendered enrichment of improved binders compared to random diversity or paratope-targeted libraries. Surprisingly several of the improved binders from the random library had beneficial mutations in the same positions targeted by the smaller focused non-essential enhancing residue focused library indicating a possible benefit of focusing diversity to these spots. We believe our method for construction of libraries with site directed mutagenesis to be a viable way for generation of functional and diverse genetic libraries, particularly suitable for affinity maturation and paratope mapping of antibodies.
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- Lindbo, Sarah, et al.
(författare)
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Design, construction and characterization of an ABD-based library with improved stability
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recombinant affinity proteins binding specifically to other molecules are important tools for many clinical and industrial applications. Small robust protein scaffolds have proven to be well suited as frameworks for generation of novel affinity binders due to their stability. Here we used the albumin-binding domain (ABD) of protein G from Streptococcus G148 as scaffold to design a new combinatorial library capable of generating stable binders to various target proteins with high affinity and specificity. To create a robust framework able to generate highly stable binders, mutations in the non-binding region were evaluated and residues providing increased stability were introduced into the scaffold. By combining rational design with combinatorial protein engineering we also evaluated the surface exposed amino acids at the albumin-binding interface and identified 11 residues suitable for randomization. The potency of the novel scaffold library was assessed by screening for binders using phage display against three distinct targets; complement factor 4, (C4), insulin and interleukin-6 (IL-6). Binders in the nanomolar range with melting temperature above 57°C were selected for all three targets. Notably, the identified IL-6 binders were characterized by extreme thermal stability with variants demonstrating organized structures even at 90°C. This demonstrates that stable binders with distinct specificities can be generated and thus proves the high potential of the library.
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- Steen, Johanna, et al.
(författare)
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The correlation between antigen solubility and immunogenicity
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In antigen design, several characteristics contribute to the final success of the antigen to elicit the desired immunogenicity. However, it is difficult to screen theses attributes due to the variability within the host immune receptor repertoire. Herein, with the massive numeral of immunizations performed within a proteome-wide endeavor to produce affinity reagents to human proteins, the correlation between the solubility of the antigens and the immunogenicity was investigated. We showed that increased solubility of the antigen resulted in higher success rate in provoking the immune defense as well as higher antibody titers. We have also shown, that the increased antibody titers after affinity purifications indeed reflectthe concentration of target specific antibodies within the serum. Finally, the amino acid composition of soluble antigens was determined to be over-represented in polar residues.
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