Exploring the cellular accumulation of metal complexes Puckett, Cindy A; Ernst, Russell J; Barton, Jacqueline K
Dalton transactions : an international journal of inorganic chemistry,
01/2010, Letnik:
39, Številka:
5
Journal Article
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Transition metal complexes offer great potential as diagnostic and therapeutic agents, and a growing number of biological applications have been explored. To be effective, these complexes must reach ...their intended target inside the cell. Here we review the cellular accumulation of metal complexes, including their uptake, localization, and efflux. Metal complexes are taken up inside cells through various mechanisms, including passive diffusion and entry through organic and metal transporters. Emphasis is placed on the methods used to examine cellular accumulation, to identify the mechanism(s) of uptake, and to monitor possible efflux. Conjugation strategies that have been employed to improve the cellular uptake characteristics of metal complexes are also described.
Identifying the proteins synthesized at specific times in cells of interest in an animal will facilitate the study of cellular functions and dynamic processes. Here we introduce stochastic orthogonal ...recoding of translation with chemoselective modification (SORT-M) to address this challenge. SORT-M involves modifying cells to express an orthogonal aminoacyl-tRNA synthetase/tRNA pair to enable the incorporation of chemically modifiable analogs of amino acids at diverse sense codons in cells in rich media. We apply SORT-M to Drosophila melanogaster fed standard food to label and image proteins in specific tissues at precise developmental stages with diverse chemistries, including cyclopropene-tetrazine inverse electron demand Diels-Alder cycloaddition reactions. We also use SORT-M to identify proteins synthesized in germ cells of the fly ovary without dissection. SORT-M will facilitate the definition of proteins synthesized in specific sets of cells to study development, and learning and memory in flies, and may be extended to other animals.
Genetically encoded unnatural amino acids provide powerful strategies for modulating the molecular functions of proteins in mammalian cells. However, this approach has not been coupled to genome-wide ...measurements, because efficient incorporation of unnatural amino acids is limited to transient expression settings that lead to very heterogeneous expression. We demonstrate that stable integration of the Methanosarcina mazei pyrrolysyl-tRNA synthetase (PylRS)/tRNA(Pyl)CUA pair (and its derivatives) into the mammalian genome enables efficient, homogeneous incorporation of unnatural amino acids into target proteins in diverse mammalian cells, and we reveal the distinct transcriptional responses of embryonic stem cells and mouse embryonic fibroblasts to amber codon suppression. Genetically encoding N-ɛ-acetyl-lysine in place of six lysine residues in histone H3 enables deposition of pre-acetylated histones into cellular chromatin, via a pathway that is orthogonal to enzymatic modification. After synthetically encoding lysine-acetylation at natural modification sites, we determined the consequences of acetylation at specific amino acids in histones for gene expression.
We develop an approach to tag proteomes synthesized by specific cell types in dissociated cortex, brain slices, and the brains of live mice. By viral-mediated expression of an orthogonal ...pyrrolysyl-tRNA synthetase-tRNAXXX pair in a cell type of interest and providing a non-canonical amino acid with a chemical handle, we selectively label neuronal or glial proteomes. The method enables the identification of proteins from spatially and genetically defined regions of the brain.
Recent human decedent model studies
and compassionate xenograft use
have explored the promise of porcine organs for human transplantation. To proceed to human studies, a clinically ready porcine ...donor must be engineered and its xenograft successfully tested in nonhuman primates. Here we describe the design, creation and long-term life-supporting function of kidney grafts from a genetically engineered porcine donor transplanted into a cynomolgus monkey model. The porcine donor was engineered to carry 69 genomic edits, eliminating glycan antigens, overexpressing human transgenes and inactivating porcine endogenous retroviruses. In vitro functional analyses showed that the edited kidney endothelial cells modulated inflammation to an extent that was indistinguishable from that of human endothelial cells, suggesting that these edited cells acquired a high level of human immune compatibility. When transplanted into cynomolgus monkeys, the kidneys with three glycan antigen knockouts alone experienced poor graft survival, whereas those with glycan antigen knockouts and human transgene expression demonstrated significantly longer survival time, suggesting the benefit of human transgene expression in vivo. These results show that preclinical studies of renal xenotransplantation could be successfully conducted in nonhuman primates and bring us closer to clinical trials of genetically engineered porcine renal grafts.
Genetic code expansion in the mouse brain Ernst, Russell J; Krogager, Toke P; Maywood, Elizabeth S ...
Nature chemical biology,
10/2016, Letnik:
12, Številka:
10
Journal Article
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Site-specific incorporation of non-natural amino acids into proteins, via genetic code expansion with pyrrolysyl tRNA synthetase (PylRS) and tRNA(Pyl)CUA pairs (and their evolved derivatives) from ...Methanosarcina sp., forms the basis of powerful approaches to probe and control protein function in cells and invertebrate organisms. Here we demonstrate that adeno-associated viral delivery of these pairs enables efficient genetic code expansion in primary neuronal culture, organotypic brain slices and the brains of live mice.
Deficiencies in mismatch repair (MMR) are associated with carcinogenesis. Rhodium metalloinsertors bind to DNA base mismatches with high specificity and inhibit cellular proliferation preferentially ...in MMR-deficient cells versus MMR-proficient cells. A family of chrysenequinone diimine complexes of rhodium with varying ancillary ligands that serve as DNA metalloinsertors has been synthesized, and both DNA mismatch binding affinities and antiproliferative activities against the human colorectal carcinoma cell lines HCT116N and HCT116O, an isogenic model system for MMR deficiency, have been determined. DNA photocleavage experiments reveal that all complexes bind to the mismatch sites with high specificities; DNA binding affinities to oligonucleotides containing single base CA and CC mismatches, obtained through photocleavage titration or competition, vary from 104 to 108 M−1 for the series of complexes. Significantly, binding affinities are found to be inversely related to ancillary ligand size and directly related to differential inhibition of the HCT116 cell lines. The observed trend in binding affinity is consistent with the metalloinsertion mode where the complex binds from the minor groove with ejection of mismatched base pairs. The correlation between binding affinity and targeting of the MMR-deficient cell line suggests that rhodium metalloinsertors exert their selective biological effects on MMR-deficient cells through mismatch binding in vivo.
The suprachiasmatic nucleus (SCN) is the principal circadian clock of mammals, coordinating daily rhythms of physiology and behavior. Circadian timing pivots around self-sustaining ...transcriptional–translational negative feedback loops (TTFLs), whereby CLOCK and BMAL1 drive the expression of the negative regulators Period and Cryptochrome (Cry). Global deletion of Cry1 and Cry2 disables the TTFL, resulting in arrhythmicity in downstream behaviors. We used this highly tractable biology to further develop genetic code expansion (GCE) as a translational switch to achieve reversible control of a biologically relevant protein, Cry1, in the SCN. This employed an orthogonal aminoacyl-tRNA synthetase/tRNACUA pair delivered to the SCN by adeno-associated virus (AAV) vectors, allowing incorporation of a noncanonical amino acid (ncAA) into AAV-encoded Cry1 protein carrying an ectopic amber stop codon. Thus, translational readthrough and Cry1 expression were conditional on the supply of ncAA via culture medium or drinking water and were restricted to neurons by synapsin-dependent expression of aminoacyl tRNA-synthetase. Activation of Cry1 translation by ncAA in neurons of arrhythmic Cry-null SCN slices immediately and dose-dependently initiated TTFL circadian rhythms, which dissipated rapidly after ncAA withdrawal. Moreover, genetic activation of the TTFL in SCN neurons rapidly and reversibly initiated circadian behavior in otherwise arrhythmic Cry-null mice, with rhythm amplitude being determined by the number of transduced SCN neurons. Thus, Cry1 does not specify the development of circadian circuitry and competence but is essential for its labile and rapidly reversible activation. This demonstrates reversible control of mammalian behavior using GCE-based translational switching, a method of potentially broad neurobiological interest.
Abstract Objective This phase II, multicenter, single-arm, two-stage study in platinum-resistant, advanced epithelial ovarian or primary peritoneal cancer evaluated the efficacy, safety, and ...tolerability of weekly single-agent volociximab. Pharmacokinetic/pharmacodynamic (PK/PD) studies were also performed. Methods Sixteen patients were enrolled in Stage 1. Volociximab was administered at 15 mg/kg IV qwk until progression of disease or drug intolerability. Tumor response was assessed every 8 weeks. Serum samples for PK or whole blood for the evaluation of circulating tumor cells, endothelial cells, and endothelial progenitor cells were obtained on Days 1, 8, 15, 29, and 50. Ascites from one patient was collected for volociximab concentration analysis. Archived tumor tissue was analyzed by immunohistochemistry (IHC) for α5 integrin expression. Results Safety data are available on all 16 patients; 14 were evaluable for efficacy. One patient had stable disease at 8 weeks. The remaining 13 progressed on treatment. Twelve patients (75%) experienced study-related adverse events (AEs); the most common (≥ 20%) were headache and fatigue. Three patients experienced possible study-related serious AEs (SAEs): reversible posterior leukoencephalopathy syndrome, pulmonary embolism, and hyponatremia. Peak serum concentrations of volociximab increased 2–3 fold from Day 1 to Day 50. Clinically relevant trough levels were achieved (> 150 μg/mL). IHC analysis of archived tumor sections showed low-to-moderate expression of α5 integrin on all ovarian cancer tissue evaluated. Conclusion Despite insufficient clinical activity in this refractory patient population to continue the study, weekly volociximab was well tolerated, and the gained understanding of the mechanism of action of volociximab will inform future development efforts.
The ability to assign cellular origin to low-abundance secreted factors in extracellular vesicles (EVs) would greatly facilitate the analysis of paracrine-mediated signaling. Here, we report a ...method, named selective isolation of extracellular vesicles (SIEVE), which uses cell type-specific proteome labeling via stochastic orthogonal recoding of translation (SORT) to install bioorthogonal reactive groups into the proteins derived from the cells targeted for labeling. We establish the native purification of intact EVs from a target cell, via a bioorthogonal tetrazine ligation, leading to copurification of the largely unlabeled EV proteome from the same cell. SIEVE enables capture of EV proteins at levels comparable with those obtained by antibody-based methods, which capture all EVs regardless of cellular origin, and at levels 20× higher than direct capture of SORT-labeled proteins. Using proteomic analysis, we analyze nonlabeled cargo proteins of EVs and show that the enhanced sensitivity of SIEVE allows for unbiased and comprehensive analysis of EV proteins from subpopulations of cells as well as for cell-specific EV proteomics in complex coculture systems. SIEVE can be applied with high efficiency in a diverse range of existing model systems for cell-cell communication and has direct applications for cell-of-origin EV analysis and for protein biomarker discovery.
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