In the Hot off the Press section of Molecular BioSystems members of the Editorial Board and their research groups highlight recent literature for the benefit of the community. This month the highlighted topics include steps towards personalized medicine, viral encapsulation of gold nanoparticles, regulation of heat shock protein 70, new insights into the molecular pathogenesis of Alzheimer’s disease, inhibition of Bcr-abl kinase in chronic myelogenous leukemia, detection of DNA using a self-fuelled DNA machine and a traditional solution to a new problem.
In their paper, the use of red clover necrotic mosaic virus (RCNMV) coat proteins (CP) to encapsulate gold nanoparticles was described. Normally, assembly of RSNM virus begins with recognition of a specific virion RNA sequence, called the origin of assembly or OAS, by coat protein. The binding of proteins to the OAS RNA initiates the assembly process and formation of a capsid. Knowing that, the researchers were able to prepare gold nanoparticles containing 20 base DNA hairpins with the loop complementary to RNA-1 of the RCNM virus. When RNA-1 is added to DNA modified gold, it hybridizes to the loop therefore forming an artificial origin of assembly (Fig. 1). Subsequent addition of RCNM coat protein and overnight incubation results in formation of virus-like particles, which contain encapsulated gold. After purification, TEM showed that the average size of the particles was 33.5 nm and only gold nanoparticles of sizes that correspond or are smaller than the size of the inner capsid hole (17 nm) can be encapsulated. Several control experiments also showed that the encapsulation is not successful if all requirements (presence of stem-loop DNA, RNA-1 and viral protein) are not met.
Taking into account the growing significance of nanoparticles for cell targeting applications, this could be a successful way of overcoming some limits of intracellular targeting. As the authors point out, viral protein capsids represent a system that can be exploited as a transport container, which could also be modified with specific protein or peptides to ease the cell penetration.
Fig. 1 Encapsulation of gold nanoparticles. The procedure mimics the encapsulation of the genome using an oligonucleotide (DNA-2) to capture the larger polycistronic RNA-1. The loop–RNA complex forms the origin of assembly that binds to the coat proteins. Reprinted with permission from J. Am. Chem. Soc., April 12, 2006, volume 128, issue 14, pages 4502–4503. Copyright 2006 American Chemical Society. |
L. Loo, R. H. Guenther, V. R. Basnayake, S. A. Lommel, S. Franzen, Controlled encapsidation of gold nanoparticles by a viral protein shell, J. Am. Chem. Soc., 2006, 128, 4502–4503.
Reviewed by: Ljiljana Fruk, Universität, Dortmund, GermanyThis paper reveals a new function associated with CHIP, regulation of Hsp70 independent of HSF1. The experiments show that CHIP targets Hsp70 for destruction when the chaperone-bound substrates in the cell are depleted, providing an elegant mechanism for maintaining the balance between the level of this chaperone and its substrates. From these data we can begin to understand how Hsp70 and potentially other chaperones are regulated. CHIP can indirectly stimulate Hsp70 expression, degrade the chaperone-bound substrates and then target Hsp70 for destruction during stress recovery by the cell, essentially controlling Hsp70 expression from beginning to end. This paper is the first to demonstrate how a chaperone can be regulated during stress recovery of a cell. Even more intriguing is that these results present a novel form of biphasic regulation of Hsp70 levels by one protein, CHIP. It will be interesting to evaluate the scope of this type of mechanism for the regulation of chaperone levels.
Shu-Bing Qian, Holly McDonough, Frank Boellmann, Douglas M. Cyr and Cam Patterson, CHIP-mediated stress recovery by sequential ubiquitination of substrates and Hsp70, Nature, 2006, 440, 551–555.
Reviewed by: Melissa O'Neal, University of Texas Southwestern Medical Center, Dallas, USAPreviously, it had been demonstrated that phosphorylation of transmembrane amyloid precursor protein (APP) on the Thr668–Pro motif is elevated in the brains of AD patients and Pin1 could restore the function of AD-associated phosphorylated tau protein and protect neurodegeneration. The authors hypothesized that Pin1 might also act on the pThr668–Pro motif to regulate APP processing and Aβ production. They found that Pin1 specifically interacts with phosphorylated APP and the interaction depends on both the pThr–Pro motif in APP and the WW domain of Pin1, which is a domain known to interact with the pSer/Thr–Pro motif. To further confirm this binding interaction and the consequence of this binding, NMR spectroscopy was employed to show that Pin1 can indeed bind to a 21-residue phosphopeptide corresponding to G659–Q679 of APP and more importantly, the binding accelerates the p-Thr668–Pro peptide bond to undergo cis to trans isomerization by several orders of magnitude compared to uncatalyzed isomerization.
To characterize the biological consequence of Pin1 binding to phosphorylated APP, the effect of Pin1 overexpression on Aβ secretion in CHO–APP cells, which is stably expressing the wild-type human APP751 isoform was investigated. The authors found that the total Aβ secretion was decreased by ∼40% in mitotic cells that have elevated levels of phosphorylated APP. Furthermore, Pin1 knockout in cells drastically increased the total Aβ secretion. Consistent with the cellular data, Pin1−/− mice also presented increased levels of insoluble Aβ42, the major toxic species, in the brain at 15 months old. On the other hand, the other APP processing products including soluble Aβ40, Aβ42 and insoluble Aβ40 did not show significant change compared to the Pin1+/+ mice.
Taken together, these data support the model shown in Fig. 2. In the presence of Pin1, the cis isomer of phosphorylated APP is converted into the trans isomer, which undergoes non-amyloidogenic processing resulting in decreased levels of toxic Aβ. In AD patients, however, the Pin1 is downregulated/inhibited by oxidation. Therefore, the cis-APP cannot be isomerized to the trans form, resulting in increased amyloidogenic APP processing to present elevated levels of toxic Aβ. In conjunction with previous data, deregulation of Pin1 in AD patients might account for the formation of both amyloid-β (Aβ) peptide plaques and neurofibrillary tangles.
Fig. 2 Pin1 affects the balance of amyloidogenic and non-amyloidogenic processing of phosphorylated APP by catalyzing the cis→trans isomerization of pThr–Pro motif. Adapted by permission from Macmillan Publishers Ltd: Nature, 2006, 440, 528–534 (http://www.nature.com), copyright 2006. |
Lucia Pastorino, Anyang Sun, Pei-Jung Lu, Xiao Zhen Zhou, Martin Balastik, Greg Finn, Gerburg Wulf, Jormay Lim, Shi-Hua Li, Xiaojiang Li, Weiming Xia, Linda K. Nicholson and Kun Ping Lu, The prolyl isomerase Pin1 regulates amyloid precursor protein processing and amyloid-β production, Nature, 2006, 440, 528–534.
Reviewed by Xiangshu Xiao, University of Texas Southwestern Medical Center, Dallas, USAKnowing that metabolite profiles of biofluids reflect a range of different factors like age, sex, diet and disease, T. A. Clayton et al. decided to test the hypothesis (Fig. 3) that the drug efficiency or toxicity can be predicted without any genetic information, but solely on the basis of a pre-drug treatment metabolite profile. An experiment on 65 rats using paracetamol as a test drug was conducted. Urine samples of rats before and after paracetamol treatment were collected, analysed by 1H NMR and correlated to the extent of liver damage observed after treatment. The results showed a statistically significant relationship between the variation in the pre-treatment data and paracetamol-induced effects on liver damage. In the example, a high level of a chemical called taurine in pre-treatment rats led to less post-treatment liver damage. On the other hand, high levels of trimethylamine-N-oxide and betain caused higher incidence of liver damage. This was a clear demonstration that the concept of pharmaco-metabonomics works and that the drug induced response could be predicted from the pre-treatment metabolite profile. Thus, in principle, drug types and particular doses could be individually tailored and the adverse drug reactions avoided. It is important to point out that the ability to do so could lead to a real pharmaceutics revolution not only in relation to improved individual healthcare, but also in a broader scientific sense concerning the synthesis of drugs as well as understanding of their metabolitic pathways.
Fig. 3 The pharmaco-metabonomic hypothesis. Adapted by permission from Macmillan Publishers Ltd: Nature, 2006, 440, 1073–1077 (http://www.nature.com), copyright 2006. |
T. A. Clayton, J. C. Lindon, O. Cloarec, H. Antti, C. Charuel, G. Hanton, J.-P. Provost, J.-L. Le Net, D. Baker, R. J. Walley, J. R. Everett, J. K. Nicholson, Pharmaco-metabonomic phenotyping and personalized drug treatment, Nature, 2006, 440, 1073–1077.
Reviewed by: Ljiljana Fruk, Universität, Dortmund, GermanyThe authors present proof-of-principle experiments in which they examined urine samples obtained from rats prior to paracetamol (acetaminophen) treatment to determine if there was a correlation between the pre-dose metabolic profile and both the post-dose drug metabolite profile and adverse effects on the liver. Using 1H nuclear magnetic resonance spectroscopy, they analyzed both pre- and post-dose urine samples and identified a significant association between the pre-dose profile and the quantities and ratios of a number of paracetamol metabolites (Fig. 4). In particular, a strong correlation between the pre-dose data and the ratio of paracetamol glucuronide to paracetamol was observed. Nicholson and coworkers also detected a statistically significant relationship between the pre-dose urinary profile (specifically, levels of taurine, trimethylamine-N-oxide and betaine) and the post-dose histological outcome. Together, these data provide evidence that pharmaco-metabonomic studies may serve as a powerful predictive tool and suggest that pre-dose metabolic profiling could dramatically decrease the occurrence and severity of adverse drug effects. Thus, they have presented an approach that will likely be important in the development of a “personalized” therapeutic strategy.
Fig. 4 1H NMR spectra of pre-dose (a, −48 h to −24 h) and post-dose (b, 0 to +24 h) urine samples from a rat dosed with paracetamol (600 mg kg−1). The inset in a is an expansion of the δ1.9–1.0 region, indicating the complexity of the endogenous profile and the richness of the embedded information. 2-OG, 2-oxoglutarate; G, paracetamol glucuronide. Reprinted by permission from Macmillan Publishers Ltd: Nature, 2006, 440, 1073–1077 (http://www.nature.com), copyright 2006. |
T. A. Clayton, J. C. Lindon, O. Cloarec, H. Antti, C. Charuel, G. Hanton, J.-P. Provost, J.-L. Le Net, D. Baker, R. J. Walley, J. R. Everett, J. K. Nicholson, Pharmaco-metabonomic phenotyping and personalized drug treatment, Nature, 2006, 440, 1073–1077.
Reviewed by: Erin E. Carlson, The Scripps Research Institute, California, USA
F. J. Adrián, Q. Ding, T. Sim, A. Velentza, C. Sloan, Y. Liu, G. Zhang, W. Hur, S. Ding, P. Manley, J. Mestan, D. Fabbro and N. S. Gray, Allosteric inhibition of Bcr-abl-dependent cell proliferation, Nat. Chem. Biol., 2006, 2, 95–102.
Reviewed by: Hyun-Suk Lim, University of Texas Southwestern Medical Center, Dallas, USA
Y. Weizmann, Z. Cheglakov, V. Pavlov, I. Willner, Autonomous fueled mechanical replication of nucleic acid templates for the amplified optical detection of DNA, Angew.Chem., Int. Ed., 2006, 45, 2238–2242.
Reviewed by: Ljiljana Fruk, Universität Dortmund, Germany
J. R. Peterson, A. M. Lebensohn, H. E. Pelish, M. W. Kirschner, Biochemical suppression of small-molecule inhibitors: a strategy to identify inhibitor targets and signaling pathway components, Chem. Biol., 2006, 13(4), 443–452.
Reviewed by: Thomas Kodadek, University of Texas Southwestern Medical Center, Dallas, USAThis journal is © The Royal Society of Chemistry 2006 |