Shirley K Knauer

University of Duisburg-Essen, Essen, North Rhine-Westphalia, Germany

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Publications (66)413.28 Total impact

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    ABSTRACT: Besides the wide use of engineered nanomaterials (NMs) in technical products, their applications are not only increasing in biotechnology and biomedicine, but also in the environmental field. While the physico-chemical properties and behaviour of NMs can be characterized accurately under idealized conditions, this is no longer the case in complex physiological or natural environments. Herein, proteins and other biomolecules rapidly bind to NMs, forming a protein/biomolecule corona that critically affects the NMs' (patho)biological and technical identities. As the corona impacts the in vitro and/or in vivo NM applications in humans and ecosystems, a mechanistic understanding of its relevance and of the biophysical forces regulating corona formation is mandatory. Based on recent insights, we here critically review and present an updated concept of corona formation and evolution. We comment on how corona signatures may be linked to effects at the nano-bio interface in physiological and environmental systems. In order to comprehensively analyse corona profiles and to mechanistically understand the coronas' biological/ecological impact, we present a tiered multidisciplinary approach. To stimulate progress in this field, we introduce the potential impact of the corona for NM-microbiome-(human)host interactions and the novel concept of 'nanologicals', i.e., the nanomaterial-specific targeting of molecular machines. We conclude by discussing the relevant challenges that still need to be resolved in this field.
    Chemical Society Reviews 06/2015; DOI:10.1039/c5cs00217f · 30.43 Impact Factor
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    ABSTRACT: The ubiquitin-dependent proteasomal degradation of proteins controls signaling and cellular survival. An increasing body of evidence suggests that the E3 ubiquitin ligases SIAH1 and SIAH2 are able to dictate the growth, development, and chemo-/radiosensitivity of breast and prostate cancer cells. Here we review the current knowledge on the impact of SIAHs on breast and prostate tumorigenesis. Furthermore, we summarize how stress, hormones, and cytokines regulate SIAH1 and SIAH2 in transformed mammalian cells. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Cytokine & Growth Factor Reviews 05/2015; DOI:10.1016/j.cytogfr.2015.04.002 · 6.54 Impact Factor
  • Oral Oncology 05/2015; 51(5):e29-e30. DOI:10.1016/j.oraloncology.2015.02.011 · 3.03 Impact Factor
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    ABSTRACT: MicroRNAs (miRNAs) are deregulated in a variety of human cancers, including neuroblastoma, the most common extracranial tumor of childhood. We previously reported a signature of 42 miRNAs to be highly predictive of neuroblastoma outcome. One miRNA in this signature, miR-542, was downregulated in tumors from patients with adverse outcome. Re-analysis of quantitative PCR and next-generation sequencing transcript data revealed that miR-542-5p as well as miR-542-3p expression is inversely correlated with poor prognosis in neuroblastoma patients. We, therefore, analyzed the function of miR-542 in neuroblastoma tumor biology. Ectopic expression of miR-542-3p in neuroblastoma cell lines reduced cell viability and proliferation, induced apoptosis and downregulated Survivin. Survivin expression was also inversely correlated with miR-542-3p expression in primary neuroblastomas. Reporter assays confirmed that miR-542-3p directly targeted Survivin. Downregulating Survivin using siRNA copied the phenotype of miR-542-3p expression in neuroblastoma cell lines, while cDNA-mediated ectopic expression of Survivin partially rescued the phenotype induced by miR-542-3p expression. Treating nude mice bearing neuroblastoma xenografts with miR-542-3p-loaded nanoparticles repressed Survivin expression, decreased cell proliferation and induced apoptosis in the respective xenograft tumors. We conclude that miR-542-3p exerts its tumor suppressive function in neuroblastoma, at least in part, by targeting Survivin. Expression of miR-542-3p could be a promising therapeutic strategy for treating aggressive neuroblastoma. © 2014 Wiley Periodicals, Inc.
    International Journal of Cancer 03/2015; 136(6). DOI:10.1002/ijc.29091 · 5.01 Impact Factor
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    ABSTRACT: Besides the wide use of nanomaterials in technical products, their application spectrum in biotechnology and biomedicine is steadily increasing. Whereas the physico-chemical properties and behavior of nanomaterials can be engineered and characterized accurately under idealized conditions, this is no longer the case in complex physiological environments. In biological fluids, proteins rapidly bind to nanomaterials forming the protein corona, critically affecting the nanomaterials' biological identity. As the corona impacts in vitro and/or in vivo nanomaterial applications, we here review the concept of the protein corona and its analytical dissection. We comment on how corona signatures may be linked to effects at the nano-bio interface and conclude how such knowledge is offering novel opportunities for improved nanomedicine.
    Nanomedicine 02/2015; 10(3):503-19. DOI:10.2217/nnm.14.184 · 5.82 Impact Factor
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    ABSTRACT: Human Taspase1 is essential for development and cancer by processing critical regulators, such as the mixed-lineage leukemia protein. Likewise, its ortholog, trithorax, is cleaved by Drosophila Taspase1 (dTaspase1), implementing a functional coevolution. To uncover novel mechanism regulating protease function, we performed a functional analysis of dTaspase1 and its comparison to the human ortholog. dTaspase1 contains an essential nucleophile threonine(195), catalyzing cis cleavage into its α- and β-subunits. A cell-based assay combined with alanine scanning mutagenesis demonstrated that the target cleavage motif for dTaspase1 (Q(3)[F/I/L/M](2)D(1)↓G(1')X(2')X(3')) differs significantly from the human ortholog (Q(3)[F,I,L,V](2)D(1)↓G(1')x(2')D(3')D(4')), predicting an enlarged degradome containing 70 substrates for Drosophila. In contrast to human Taspase1, dTaspase1 shows no discrete localization to the nucleus/nucleolus due to the lack of the importin-α/nucleophosmin1 interaction domain (NoLS) conserved in all vertebrates. Consequently, dTaspase1 neither interacts with the Drosophila nucleoplasmin-like protein nor human nucleophosmin1. The impact of localization on the protease's degradome was confirmed by demonstrating that dTaspase1 did not efficiently process nuclear substrates, such as upstream stimulatory factor 2. However, genetic introduction of the NoLS into dTaspase1 restored its nucleolar localization, nucleophosmin1 interaction, and efficient cleavage of nuclear substrates. We report that evolutionary functional divergence separating vertebrates from invertebrates can be achieved for proteases by a transport/localization-regulated mechanism.-Wünsch, D., Hahlbrock, A., Heiselmayer, C., Bäcker, S., Heun, P., Goesswein, D., Stöcker, W., Schirmeister, T., Schneider, G., Krämer, O. H., Knauer, S. K., Stauber, R. H. Fly versus man: Evolutionary impairment of nucleolar targeting affects the degradome of Drosophila's Taspase1. © FASEB.
    The FASEB Journal 01/2015; 29(5). DOI:10.1096/fj.14-262451 · 5.48 Impact Factor
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    ABSTRACT: Arginine-rich cell-penetrating peptides are widely utilized as vectors for gene delivery. However, their transfection efficacy still needs to be optimized. To accomplish this, guanidinocarbonylpyrrole groups, which are tailor-made anion binding sites, were introduced into the side chains of tetralysine to obtain the peptide analogue 1. In contrast to the common strategy of adding a lipophilic tail to peptide vectors, this novel method most likely enhances transfection efficacy through more specific interactions between the binding motifs and DNA or the cell membrane. Tetrapeptide analogue 1 is thus the smallest peptidic transfection vector that has been reported to date. The transfection efficacy of 1, which on average has less than two positive charges under physiological conditions, is even better than that of polyethylenimine (PEI). Furthermore, 1 exhibits only negligible cytotoxicity, which makes it an interesting candidate for further development.
    Angewandte Chemie International Edition 01/2015; 127(10). DOI:10.1002/anie.201410429 · 11.34 Impact Factor
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    ABSTRACT: The transcription factor nuclear factor-κB (NF-κB) is crucial for the maintenance of homeostasis. It is incompletely understood how nuclear NF-κB and the crosstalk of NF-κB with other transcription factors are controlled. Here, we demonstrate that the epigenetic regulator histone deacetylase 2 (HDAC2) activates NF-κB in transformed and primary cells. This function depends on both, the catalytic activity and an intact HDAC2 sumoylation motif. Several mechanisms account for the induction of NF-κB through HDAC2. The expression of wild-type HDAC2 can increase the nuclear presence of NF-κB. In addition, the ribosomal S6 kinase 1 (RSK1) and the tumor suppressor p53 contribute to the regulation of NF-κB by HDAC2. Moreover, TP53 mRNA expression is positively regulated by wild-type HDAC2 but not by sumoylation-deficient HDAC2. Thus, sumoylation of HDAC2 integrates NF-κB signaling involving p53 and RSK1. Since HDAC2-dependent NF-κB activity protects colon cancer cells from genotoxic stress, our data also suggest that high HDAC2 levels, which are frequently found in tumors, are linked to chemoresistance. Accordingly, inhibitors of NF-κB and of the NF-κB/p53-regulated anti-apoptotic protein survivin significantly sensitize colon carcinoma cells expressing wild-type HDAC2 to apoptosis induced by the genotoxin doxorubicin. Hence, the HDAC2-dependent signaling node we describe here may offer an interesting therapeutic option.
    Oncotarget 01/2015; · 6.63 Impact Factor
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    ABSTRACT: Abstract Proteases are key regulators of life. Human Threonine Aspartase1 processes substrates, such as the mixed-lineage leukemia (MLL) protein, containing two cleavage sites, CS1 and CS2. Likewise, MLL's Drosophila ortholog trithorax is cleaved by D̲rosophila T̲hreonine A̲s̲p̲artase1 (dTasp), suggesting a mechanistic co-evolution. However, a detailed analysis of dTasp's function was missing so far. Here, active and inactive dTasp mutants allowed to compare substrate recognition and cleavage-site selectivity of human and Drosophila enzymes. In contrast to the human protease, our cell-based assay revealed a preferential processing of CS2-like (QLD↓Gx[xD/Dx]) targets for dTasp, whereas cleavage of CS1-like targets (QVD↓Gx[xD/Dx]) was significantly impaired. Systematic mutagenesis of the CS2-sequence defined the motif x[FILMW]D↓Gx[xD/Dx] as the consensus cleavage sequence for dTasp. Substrate species-selectivity of the enzymes was uncovered by demonstrating that dTasp cleaves Drosophila TFIIA, but not the human ortholog, suggesting evolutionary divergence of TFIIA downstream networks. Also, Drosophila USF2 was neither predicted, nor cleaved by dTasp. Moreover, we found that dTasp cleavage-site selectivity is independent of heterocomplex formation, as dTasp exists predominantly as an αβ-monomer. Collectively, we provide novel insights into evolutionary similarities and divergence concerning Threonine Aspartase1 function in different species, which may aid to dissect and better target human Threonine Aspartase1 in malignancies.
    Biological Chemistry 01/2015; DOI:10.1515/hsz-2014-0318 · 2.69 Impact Factor
  • Shirley K. Knauer, Wolf Mann, Roland H. Stauber
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    ABSTRACT: Survivin is proposed to function as a mitotic regulator and an apoptosis inhibitor duringdevelopment and pathogenesis. As such, survivin has aroused keen interest in disparateareas of basic and translational research. Survivin acts as a subunit of the chromosomalpassenger complex (CPC), composed of the mitotic kinase Aurora-B, Borealin 5 and INCENP,and is essential for proper chromosome segregation and cytokinesis. Our recent findingsindicate that the nuclear export receptor Crm1 is critically involved in tethering the CPC to thecentromere by interacting with a leucine-rich nuclear export signal (NES), evolutionaryconserved in all mammalian survivin proteins. In addition, the survivin/Crm1 interaction10 seems to be required for the cytoprotective activity of survivin, because export deficientsurvivin fails to protect tumor cells against cancer therapy-induced apoptosis. These findingsappear of clinical relevance since preferential nuclear localization of survivin turned out to bea favorable prognostic factor in cancer patients. Besides emphasizing the functionalsignificance of the Crm1/survivin interface, we suggest to exploit the pharmacogenetic15 interference with survivin’s export as a novel strategy to antagonize survivin’s activity.
    Cell cycle (Georgetown, Tex.) 10/2014; 6(5):518-521. DOI:10.4161/cc.6.5.3902 · 5.01 Impact Factor
  • ChemBioChem 10/2014; 15(15):2165-2165. DOI:10.1002/cbic.201490051 · 3.06 Impact Factor
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    ABSTRACT: Taspase 1 is an N-terminal threonine protease implicated in leukemia and other cancers. Despite intensive efforts in recent years, only a limited number of Taspase 1 inhibitors are currently available, and they lack general applicability. Here we present a novel class of Taspase 1 inhibitors based on a peptidyl succinimidyl peptide motif. These inhibitors were obtained from the substrate cleavage sequence and mechanistic considerations involving the previously proposed asparaginase-type cleavage mechanism. We anticipate that this class of Taspase 1 inhibitor will find wide application in further biochemical and structural studies, for example for better investigating the molecular details of the unusual enzymatic cleavage mechanism of Taspase 1.
    ChemBioChem 10/2014; 15(15). DOI:10.1002/cbic.201402108 · 3.06 Impact Factor
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    ABSTRACT: Calcium phosphate/poly(D,L-lactide-co-glycolide acid) (PLGA) nanoparticles with a diameter below 200 nm, loaded with either nucleic acids or proteins, were synthesized by a water-in-oil-in-water (W1/O/W2) emulsion solvent evaporation technique. The particles were stabilized by polyvinyl alcohol (PVA) and had a negative charge (zeta potential -26 mV). By the addition of calcium phosphate into the inner aqueous phase of the W1/O/W2-emulsion, the encapsulation efficiency of siRNA was increased to 37%, of DNA to 52%, and of bovine serum albumin to 78%, i.e. by a factor of 3 to 10 compared to PLGA nanoparticles without calcium phosphate. Total loadings of 8 µg siRNA, 5 µg DNA and 280 µg fluorescein isothiocyanate-labelled bovine serum albumin (FITC-BSA) per mg of PLGA were achieved by this method. The addition of an outer layer of either chitosan or polyethyleneimine (PEI) reversed the charge of the particles (zeta potential > +30 mV) and improved the cellular uptake as well as the endosomal escape of these particles as demonstrated by confocal laser scanning microscopy. Calcium phosphate-PLGA nanoparticles loaded with DNA encoding for green fluorescent protein (eGFP-DNA) showed a good transfection efficiency for epithelial cells (HeLa) without any toxic effects. Gene silencing with HeLa cells expressing eGFP gave knockdown efficiencies of 53% for anionic nanoparticles, of 68% for chitosan-coated cationic nanoparticles, and of 89% for polyethyleneimine-coated cationic nanoparticles.
    09/2014; 2(41). DOI:10.1039/C4TB00922C
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    ABSTRACT: Nanoparticle applications in biotechnology and biomedicine are steadily increasing. In biological fluids, proteins bind to nanoparticles that form the protein corona, crucially affecting the nanoparticles' biological identity. As the corona affects in vitro and/or in vivo nanoparticle applications, we developed a method to obtain time-resolved protein corona profiles formed on various nanoparticles. After incubation in plasma or a similar biofluid, or after injection into a mouse, the first analytical step is sedimentation of the nanoparticle-protein complexes through a sucrose cushion, thereby allowing analysis of early corona formation time points. Next, corona profiles are visualized by gel electrophoresis and quantitatively analyzed after tryptic digestion using label-free liquid chromatography-high-resolution mass spectrometry. In contrast to other approaches, our established methodology allows the researcher to obtain qualitative and quantitative high-resolution corona signatures. The protocol can be readily extended to the investigation of protein coronas from various nanomaterials (as an example, we applied this protocol to different silica nanoparticles (SiNPs) and polystyrene nanoparticles (PSNPs)). Depending on the number of samples, the protocol from nanoparticle-protein complex recovery to data evaluation takes ∼8-12 d to complete.
    Nature Protocols 09/2014; 9(9):2030-2044. DOI:10.1038/nprot.2014.139 · 7.78 Impact Factor
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    ABSTRACT: Into the library: Screening a focused library of 259 peptide tweezers, composed of two identical arms with zero to three amino acids and an artificial anion recognition site, yielded DNA binders with nanomolar affinity. These ligands are only modest gene carriers (transfection efficiency <10 %); however, excellent transfection efficiencies (up to 90 %) were achieved after the covalent attachment of long aliphatic chains.
    Angewandte Chemie International Edition 12/2013; 52(52):14016-20. DOI:10.1002/anie.201306929 · 11.34 Impact Factor
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    ABSTRACT: In biological fluids, proteins bind to the surface of nanoparticles to form a coating known as the protein corona, which can critically affect the interaction of the nanoparticles with living systems. As physiological systems are highly dynamic, it is important to obtain a time-resolved knowledge of protein-corona formation, development and biological relevancy. Here we show that label-free snapshot proteomics can be used to obtain quantitative time-resolved profiles of human plasma coronas formed on silica and polystyrene nanoparticles of various size and surface functionalization. Complex time- and nanoparticle-specific coronas, which comprise almost 300 different proteins, were found to form rapidly (<0.5 minutes) and, over time, to change significantly in terms of the amount of bound protein, but not in composition. Rapid corona formation is found to affect haemolysis, thrombocyte activation, nanoparticle uptake and endothelial cell death at an early exposure time.
    Nature Nanotechnology 09/2013; 8(10). DOI:10.1038/nnano.2013.181 · 33.27 Impact Factor
  • Roland H. Stauber, Shirley K. Knauer
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    ABSTRACT: Proteases not only play an essential role in biological processes, they serve as clinically approved targets of current oncological approaches. As such, Taspase1 was postulated as therapeutic target in leukemogenesis. However, our molecular knowledge on its function is still rather fragmentary as still no effective inhibitors are available. Moreover the Taspase1 degradome, the collectivity of its target proteins, could be revealed just recently by the development of special cell-based assays.
    BioSpektrum 03/2013; 19(2). DOI:10.1007/s12268-013-0281-5
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    ABSTRACT: Survivin (BIRC5) is an acknowledged cancer therapy-resistance factor and overexpressed in head and neck squamous cell carcinomas (HNSCC). Driven by its nuclear export signal (NES), Survivin shuttles between the nucleus and the cytoplasm, and is detectable in both cellular compartments in tumor biopsies. Although predominantly nuclear Survivin is considered a favorable prognostic disease marker for HNSCC patients, the underlying molecular mechanisms are not resolved. Hence, we performed immunohistochemical and mutational analyses using laser capture microdissection on HNSCC biopsies from patients displaying high levels of nuclear Survivin. We found somatic BIRC5 mutations, c.278T>C (p.Phe93Ser), c.292C>T (p.Leu98Phe) and c.288A>G (silent), in tumor cells, but not in corresponding normal tissues. Comprehensive functional characterization of the Survivin mutants by ectopic expression and microinjection experiments revealed that p.Phe93Ser, but not p.Leu98Phe inactivated Survivin's NES, resulted in a predominantly nuclear protein, and attenuated Survivin's dual cytoprotective activity against chemo-radiation-induced apoptosis. Notably, in xenotransplantation studies, HNSCC cells containing the p.Phe93Ser mutation responded significantly better to cisplatin-based chemotherapy. Collectively, our results underline the disease-relevance of Survivin's nucleo-cytoplasmic transport, and provide first evidence that genetic inactivation of Survivin's NES may account for predominantly nuclear Survivin and increased therapy response in cancer patients.
    Human Mutation 02/2013; 34(2). DOI:10.1002/humu.22249 · 5.05 Impact Factor
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    ABSTRACT: The delicate balance between the synthesis and the degradation of proteins ensures cellular homeostasis. Proteases act in an irreversible manner and therefore have to be strictly regulated. The ubiquitin-proteasome-system (UPS) is a major pathway for the proteolytic degradation of cellular proteins. Since dysregulation of the UPS is observed in most cancers including leukemia, the UPS is a valid target for therapeutic intervention strategies. Ubiquitin-ligases selectively bind substrates to target them for poly-ubiquitinylation and proteasomal degradation. Therefore, pharmacological modulation of these proteins could allow a specific level of control. Increasing evidence accumulates that ubiquitin-ligases termed mammalian seven in absentia homologues (SIAHs) are not only critical for the pathogenesis of solid tumors but also for leukemogenesis. However, the relevance and therapeutic potential of SIAH-dependent processes has not been fully elucidated. Here, we summarize functions of SIAH ubiquitin-ligases in leukemias, how they select leukemia-relevant substrates for proteasomal degradation, and how the expression and activity of SIAH1 and SIAH2 can be modulated in vivo. We also discuss that epigenetic drugs belonging to the group of histone deacetylase inhibitors induce SIAH-dependent proteasomal degradation to accelerate the turnover of leukemogenic proteins. In addition, our review highlights potential areas for future research on SIAH proteins.Leukemia accepted article preview online, 5 October 2012; doi:10.1038/leu.2012.284.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 10/2012; 27(4). DOI:10.1038/leu.2012.284 · 9.38 Impact Factor

Publication Stats

2k Citations
413.28 Total Impact Points

Institutions

  • 2010–2015
    • University of Duisburg-Essen
      • • Arbeitsgruppe Molekularbiologie I
      • • Center for Medical Biotechnology
      Essen, North Rhine-Westphalia, Germany
  • 2007–2009
    • Johannes Gutenberg-Universität Mainz
      Mayence, Rheinland-Pfalz, Germany
  • 2007–2008
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany
  • 2005–2008
    • Georg-Speyer-Haus
      Frankfurt, Hesse, Germany