| 1. |
- Hernandez, Frank J, et al.
(författare)
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Degradation of nuclease-stabilized RNA oligonucleotides in Mycoplasma-contaminated cell culture media
- 2012
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Ingår i: Nucleic Acid Therapeutics. - : Mary Ann Liebert. - 2159-3337 .- 2159-3345. ; 22:1, s. 58-68
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Tidskriftsartikel (refereegranskat)abstract
- Artificial RNA reagents such as small interfering RNAs (siRNAs) and aptamers often must be chemically modified for optimal effectiveness in environments that include ribonucleases. Mycoplasmas are common bacterial contaminants of mammalian cell cultures that are known to produce ribonucleases. Here we describe the rapid degradation of nuclease-stabilized RNA oligonucleotides in a human embryonic kidney 293 (HEK) cell culture contaminated with Mycoplasma fermentans, a common species of mycoplasma. RNA with 2′-fluoro-or 2′-O-methyl-modified pyrimidines was readily degraded in conditioned media from this culture, but was stable in conditioned media from uncontaminated HEK cells. RNA completely modified with 2′-O-methyls was not degraded in the mycoplasma-contaminated media. RNA zymogram analysis of conditioned culture media and material centrifuged from the media revealed several distinct protein bands (ranging from 30 to 68kDa) capable of degrading RNA with 2′-fluoro-or 2′-O-methyl-modified pyrimidines. Finally, the mycoplasma-associated nuclease was detected in material centrifuged from the contaminated culture supernatants in as little as 15 minutes with an RNA oligo-containing 2′-O-methyl-modified pyrimidines and labeled with a 5′-fluorescein amidite (FAM) and 3′-quencher. These results suggest that mycoplasma contamination may be a critical confounding variable for cell culture experiments involving RNA-based reagents, with particular relevance for applications involving naked RNA (e.g., aptamer-siRNA chimeras). © 2012 Mary Ann Liebert, Inc.
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| 2. |
- Hernandez, Frank J, et al.
(författare)
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Noninvasive imaging of Staphylococcus aureus infections with a nuclease-activated probe
- 2014
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Ingår i: Nature Medicine. - : Nature Publishing Group. - 1078-8956 .- 1546-170X. ; 20:3, s. 301-306
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Tidskriftsartikel (refereegranskat)abstract
- Technologies that enable the rapid detection and localization of bacterial infections in living animals could address an unmet need for infectious disease diagnostics. We describe a molecular imaging approach for the specific, noninvasive detection of S. aureus based on the activity of the S. aureus secreted nuclease, micrococcal nuclease (MN). Several short synthetic oligonucleotides, rendered resistant to mammalian serum nucleases by various chemical modifications and flanked with a fluorophore and quencher, were activated upon degradation by purified MN and in S. aureus culture supernatants. A probe consisting of a pair of deoxythymidines flanked by several 2′-O-methyl-modified nucleotides was activated in culture supernatants of S. aureus but not in culture supernatants of several other pathogenic bacteria. Systemic administration of this probe to mice bearing S. aureus muscle infections resulted in probe activation at the infection sites in an MN-dependent manner. This new bacterial imaging approach has potential clinical applicability for infections with S. aureus and several other medically important pathogens. © 2014 Nature America, Inc.
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| 3. |
- Hernandez, Luiza I., et al.
(författare)
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Methods for evaluating cell-specific, cell-internalizing RNA aptamers
- 2013
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Ingår i: Pharmaceuticals. - : Multidisciplinary Digital Publishing Institute (M D P I AG). - 1424-8247. ; 6:3, s. 295-319
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Tidskriftsartikel (refereegranskat)abstract
- Recent clinical trials of small interfering RNAs (siRNAs) highlight the need for robust delivery technologies that will facilitate the successful application of these therapeutics to humans. Arguably, cell targeting by conjugation to cell-specific ligands provides a viable solution to this problem. Synthetic RNA ligands (aptamers) represent an emerging class of pharmaceuticals with great potential for targeted therapeutic applications. For targeted delivery of siRNAs with aptamers, the aptamer-siRNA conjugate must be taken up by cells and reach the cytoplasm. To this end, we have developed cell- based selection approaches to isolate aptamers that internalize upon binding to their cognate receptor on the cell surface. Here we describe methods to monitor for cellular uptake of aptamers. These include: (1) antibody amplification microscopy, (2) microplate- based fluorescence assay, (3) a quantitative and ultrasensitive internalization method (QUSIM) and (4) a way to monitor for cytoplasmic delivery using the ribosome inactivating protein-based (RNA-RIP) assay. Collectively, these methods provide a toolset that can expedite the development of aptamer ligands to target and deliver therapeutic siRNAs in vivo. © 2013 by the authors; licensee MDPI, Basel, Switzerland.
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| 4. |
- Huang, Yang Zhong, et al.
(författare)
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RNA aptamer-based functional ligands of the neurotrophin receptor, TrkB
- 2012
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Ingår i: Molecular Pharmacology. - Bethesda, United States : American Society for Pharmacology and Experimental Therapeutics. - 0026-895X .- 1521-0111. ; 82:4, s. 623-635
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Tidskriftsartikel (refereegranskat)abstract
- Many cell surface signaling receptors, such as the neurotrophin receptor, TrkB, have emerged as potential therapeutic targets for diverse diseases. Reduced activation of TrkB in particular is thought to contribute to neurodegenerative diseases. Unfortunately, development of therapeutic reagents that selectively activate particular cell surface receptors such as TrkB has proven challenging. Like many cell surface signaling receptors, TrkB is internalized upon activation; in this proof-of-concept study, we exploited this fact to isolate a pool of nuclease-stabilized RNA aptamers enriched for TrkB agonists. One of the selected aptamers, C4-3, was characterized with recombinant protein-binding assays, cell-based signaling and functional assays, and, in vivo in a seizure model in mice. C4-3 binds the extracellular domain of TrkB with high affinity (KD ∼2 nM) and exhibits potent TrkB partial agonistic activity and neuroprotective effects in cultured cortical neurons. In mice, C4-3 activates TrkB upon infusion into the hippocampus; systemic administration of C4-3 potentiates kainic acid-induced seizure development. We conclude that C4-3 is a potentially useful therapeutic agent for neurodegenerative diseases in which reduced TrkB activation has been implicated. We anticipate that the cell-based aptamer selection approach used here will be broadly applicable to the identification of aptamer-based agonists for a variety of cell-surface signaling receptors. Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics.
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| 5. |
- Kiedrowski, Megan R., et al.
(författare)
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Staphylococcus aureus Nuc2 is a functional, surface-attached extracellular nuclease
- 2014
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Ingår i: PLOS ONE. - San Francisco, United States : Public Library of Science. - 1932-6203. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- Staphylococcus aureus is a prominent bacterial pathogen that causes a diverse range of acute and chronic infections. Recently, it has been demonstrated that the secreted nuclease (Nuc) enzyme is a virulence factor in multiple models of infection, and in vivo expression of nuc has facilitated the development of an infection imaging approach based on Nuc-activatable probes. Interestingly, S. aureus strains encode a second nuclease (Nuc2) that has received limited attention. With the growing interest in bacterial nucleases, we sought to characterize Nuc2 in more detail through localization, expression, and biochemical studies. Fluorescence microscopy and alkaline phosphatase localization approaches using Nuc2-GFP and Nuc2-PhoA fusions, respectively, demonstrated that Nuc2 is membrane bound with the C-terminus facing the extracellular environment, indicating it is a signal-anchored Type II membrane protein. Nuc2 enzyme activity was detectable on the S. aureus cell surface using a fluorescence resonance energy transfer (FRET) assay, and in time courses, both nuc2 transcription and enzyme activity peaked in early logarithmic growth and declined in stationary phase. Using a mouse model of S. aureus pyomyositis, Nuc2 activity was detected with activatable probes in vivo in nuc mutant strains, demonstrating that Nuc2 is produced during infections. To assess Nuc2 biochemical properties, the protein was purified and found to cleave both single- and double-stranded DNA, and it exhibited thermostability and calcium dependence, paralleling the properties of Nuc. Purified Nuc2 prevented biofilm formation in vitro and modestly decreased biomass in dispersal experiments. Altogether, our findings confirm that S. aureus encodes a second, surface-attached and functional DNase that is expressed during infections and displays similar biochemical properties to the secreted Nuc enzyme. © 2014 Kiedrowski et al.
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| 6. |
- Rockey, William M., et al.
(författare)
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Rational truncation of an RNA aptamer to prostate-specific membrane antigen using computational structural modeling
- 2011
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Ingår i: Nucleic Acid Therapeutics. - : Mary Ann Liebert. - 2159-3337 .- 2159-3345. ; 21:5, s. 299-314
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Tidskriftsartikel (refereegranskat)abstract
- RNA aptamers represent an emerging class of pharmaceuticals with great potential for targeted cancer diagnostics and therapy. Several RNA aptamers that bind cancer cell-surface antigens with high affinity and specificity have been described. However, their clinical potential has yet to be realized. A significant obstacle to the clinical adoption of RNA aptamers is the high cost of manufacturing long RNA sequences through chemical synthesis. Therapeutic aptamers are often truncated postselection by using a trial-and-error process, which is time consuming and inefficient. Here, we used a rational truncation approach guided by RNA structural prediction and protein/RNA docking algorithms that enabled us to substantially truncateA9, an RNA aptamer to prostate-specific membrane antigen (PSMA),with great potential for targeted therapeutics. This truncated PSMA aptamer (A9L; 41mer) retains binding activity, functionality, and is amenable to large-scale chemical synthesis for future clinical applications. In addition, the modeled RNA tertiary structure and protein/RNA docking predictions revealed key nucleotides within the aptamer critical for binding to PSMA and inhibiting its enzymatic activity. Finally, this work highlights the utility of existing RNA structural prediction and protein docking techniques that may be generally applicable to developing RNA aptamers optimized for therapeutic use. © 2011 Mary Ann Liebert, Inc.
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| 7. |
- Thiel, Kristina W., et al.
(författare)
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Delivery of chemo-sensitizing siRNAs to HER2+-breast cancer cells using RNA aptamers
- 2012
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Ingår i: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 40:13, s. 6319-6337
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Tidskriftsartikel (refereegranskat)abstract
- Human epidermal growth factor receptor 2 (HER2) expression in breast cancer is associated with an aggressive phenotype and poor prognosis, making it an appealing therapeutic target. Trastuzumab, an HER2 antibody-based inhibitor, is currently the leading targeted treatment for HER2+-breast cancers. Unfortunately, many patients inevitably develop resistance to the therapy, highlighting the need for alternative targeted therapeutic options. In this study, we used a novel, cell-based selection approach for isolating cell-type specific, cell-internalizing RNA ligands (aptamers) capable of delivering therapeutic small interfering RNAs (siRNAs) to HER2-expressing breast cancer cells. RNA aptamers with the greatest specificity and internalization potential were covalently linked to siRNAs targeting the anti-apoptotic gene, Bcl-2. We demonstrate that, when applied to cells, the HER2 aptamer-Bcl-2 siRNA conjugates selectively internalize into HER2+-cells and silence Bcl-2 gene expression. Importantly, Bcl-2 silencing sensitizes these cells to chemotherapy (cisplatin) suggesting a potential new therapeutic approach for treating breast cancers with HER2+-status. In summary, we describe a novel cell-based selection methodology that enables the identification of cell-internalizing RNA aptamers for targeting therapeutic siRNAs to HER2-expressing breast cancer cells. The future refinement of this technology may promote the widespread use of RNA-based reagents for targeted therapeutic applications. © 2012 The Author(s).
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