Mammalian cells are capable of delivering multiple types of membrane capsules extracellularly. The limiting membrane of late endosomes can fuse with the plasma membrane, leading to the extracellular ...release of multivesicular bodies (MVBs), initially contained within the endosomes, as exosomes. Budding viruses exploit the TSG101 protein and endosomal sorting complex required for transport (ESCRT) machinery used for MVB formation to mediate the egress of viral particles from host cells. Here we report the discovery of a virus-independent cellular process that generates microvesicles that are distinct from exosomes and which, like budding viruses, are produced by direct plasma membrane budding. Such budding is driven by a specific interaction of TSG101 with a tetrapeptide PSAP motif of an accessory protein, arrestin domain-containing protein 1 (ARRDC1), which we show is localized to the plasma membrane through its arrestin domain. This interaction results in relocation of TSG101 from endosomes to the plasma membrane and mediates the release of microvesicles that contain TSG101, ARRDC1, and other cellular proteins. Unlike exosomes, which are derived from MVBs, ARRDC1-mediated microvesicles (ARMMs) lack known late endosomal markers. ARMMs formation requires VPS4 ATPase and is enhanced by the E3 ligase WWP2, which interacts with and ubiquitinates ARRDC1. ARRDC1 protein discharged into ARMMs was observed in co-cultured cells, suggesting a role for ARMMs in intercellular communication. Our findings reveal an intrinsic cellular mechanism that results in direct budding of microvesicles from the plasma membrane, providing a formal paradigm for the evolutionary recruitment of ESCRT proteins in the release of budding viruses.
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In November 1973, my colleagues A. C. Y. Chang, H. W. Boyer, R. B. Helling, and I reported in PNAS that individual genes can be cloned and isolated by enzymatically cleaving DNA molecules into ...fragments, linking the fragments to an autonomously replicating plasmid, and introducing the resulting recombinant DNA molecules into bacteria. A few months later, Chang and I reported that genes from unrelated bacterial species can be combined and propagated using the same approach and that interspecies recombinant DNA molecules can produce a biologically functional protein in a foreign host. Soon afterward, Boyer’s laboratory and mine published our collaborative discovery that even genes from animal cells can be cloned in bacteria. These three PNAS papers quickly led to the use of DNA cloning methods in multiple areas of the biological and chemical sciences. They also resulted in a highly public controversy about the potential hazards of laboratory manipulation of genetic material, a decision by Stanford University and the University of California to seek patents on the technology that Boyer and I had invented, and the application of DNA cloning methods for commercial purposes. In the 40 years that have passed since publication of our findings, use of DNA cloning has produced insights about the workings of genes and cells in health and disease and has altered the nature of the biotechnology and biopharmaceutical industries. Here, I provide a personal perspective of the events that led to, and followed, our report of DNA cloning.
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In this randomized comparison of stenting and endarterectomy as treatment for carotid-artery stenosis, there was no significant difference in the rate of the composite primary end point of stroke, ...myocardial infarction, or death (7.2% and 6.8%, respectively; P=0.51). Stroke was more common with carotid-artery stenting than carotid endarterectomy; myocardial infarction was more common with carotid endarterectomy. The 4-year rate of stroke or death was 6.4% for carotid-artery stenting and 4.7% for carotid endarterectomy (P=0.03).
In this randomized comparison of stenting and endarterectomy as treatment for carotid-artery stenosis, there was no significant difference in the rate of the composite primary end point of stroke, myocardial infarction, or death (7.2% and 6.8%, respectively).
Carotid-artery atherosclerosis is an important cause of ischemic stroke.
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Carotid endarterectomy has been established as effective treatment for both symptomatic patients and asymptomatic patients.
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Carotid-artery stenting is another option for treatment. The results of randomized trials comparing carotid-artery stenting and carotid endarterectomy for use in symptomatic patients are conflicting.
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The primary aim of the Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST) was to compare the outcomes of carotid-artery stenting with those of carotid endarterectomy among patients with symptomatic or asymptomatic extracranial carotid stenosis.
Methods
Study Design
CREST is a randomized, controlled trial with blinded end-point adjudication. Ethics review . . .
Lengthy trinucleotide repeats encoding polyglutamine (polyQ) stretches characterize the variant proteins of Huntington's disease and certain other inherited neurological disorders. Using a phenotypic ...screen to identify events that restore functionality to polyQ proteins in S. cerevisiae, we discovered that transcription elongation factor Spt4 is required to transcribe long trinucleotide repeats located either in ORFs or nonprotein-coding regions of DNA templates. Mutation of SPT4 selectively decreased synthesis of and restored enzymatic activity to expanded polyQ protein without affecting protein lacking long-polyQ stretches. RNA-seq analysis revealed limited effects of Spt4 on overall gene expression. Inhibition of Supt4h, the mammalian ortholog of Spt4, reduced mutant huntingtin protein in neuronal cells and decreased its aggregation and toxicity while not altering overall cellular mRNA synthesis. Our findings identify a cellular mechanism for transcription through repeated trinucleotides and a potential target for countermeasures against neurological disorders attributable to expanded trinucleotide regions.
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► Spt4 is selectively required for transcription through extended trinucleotide repeats ► Reduced synthesis of polyQ protein restores function in yeast and neurons ► Nonaggregated expanded polyQ proteins retain enzymatic activity ► Supt4h inhibition decreases synthesis and aggregation of mutant huntingtin
The transcription elongation protein Spt4 and its mammalian ortholog, Supt4h, promote the synthesis of mRNAs containing lengthy trinucleotide repeats, revealing a potential target for the treatment of neurological disorders caused by expanded trinucleotide regions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Production of protein containing lengthy stretches of polyglutamine encoded by multiple repeats of the trinucleotide CAG is a hallmark of Huntington's disease (HD) and of a variety of other inherited ...degenerative neurological and neuromuscular disorders. Earlier work has shown that interference with production of the transcription elongation protein SUPT4H results in decreased cellular capacity to transcribe mutant huntingtin gene (Htt) alleles containing long CAG expansions, but has little effect on expression of genes containing short CAG stretches. zQ175 and R6/2 are genetically engineered mouse strains whose genomes contain human HTT alleles that include greatly expanded CAG repeats and which are used as animal models for HD. Here we show that reduction of SUPT4H expression in brains of zQ175 mice by intracerebroventricular bolus injection of antisense 2'-O-methoxyethyl oligonucleotides (ASOs) directed against Supt4h, or in R6/2 mice by deletion of one copy of the Supt4h gene, results in a decrease in mRNA and protein encoded specifically by mutant Htt alleles. We further show that reduction of SUPT4H in mouse brains is associated with decreased HTT protein aggregation, and in R6/2 mice, also with prolonged lifespan and delay of the motor impairment that normally develops in these animals. Our findings support the view that targeting of SUPT4H function may be useful as a therapeutic countermeasure against HD.
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Much of the information available about factors that affect mRNA decay in Escherichia coli, and by inference in other bacteria, has been gleaned from study of less than 25 of the ≈4,300 predicted E. ...coli messages. To investigate these factors more broadly, we examined the half-lives and steady-state abundance of known and predicted E. coli mRNAs at single-gene resolution by using two-color fluorescent DNA microarrays. An rRNA-based strategy for normalization of microarray data was developed to permit quantitation of mRNA decay after transcriptional arrest by rifampicin. We found that globally, mRNA half-lives were similar in nutrient-rich media and defined media in which the generation time was approximately tripled. A wide range of stabilities was observed for individual mRNAs of E. coli, although ≈80% of all mRNAs had half-lives between 3 and 8 min. Genes having biologically related metabolic functions were commonly observed to have similar stabilities. Whereas the half-lives of a limited number of mRNAs correlated positively with their abundance, we found that overall, increased mRNA stability is not predictive of increased abundance. Neither the density of putative sites of cleavage by RNase E, which is believed to initiate mRNA decay in E. coli, nor the free energy of folding of 5′ or 3′ untranslated region sequences was predictive of mRNA half-life. Our results identify previously unsuspected features of mRNA decay at a global level and also indicate that generalizations about decay derived from the study of individual gene transcripts may have limited applicability.
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The lack of generally accepted diagnostic criteria for neuroleptic malignant syndrome (NMS) impedes research and clinical management of patients receiving antipsychotic medications. The purpose of ...this study was to develop NMS diagnostic criteria reflecting a broad consensus among clinical knowledge experts, represented by an international multispecialty physician panel.
Eleven psychiatrists, 2 neurologists, 2 anesthesiologists, and 2 emergency medicine specialists participated in a formal Delphi consensus procedure.
A core bibliography consisting of 12 prominent, current reviews of the NMS literature was identified by an objective, comprehensive electronic search strategy. Each panel member was given a copy of these references and asked to examine them before commencing the survey process.
After reviewing the core bibliography, panel members were asked to list any clinical signs or symptoms or diagnostic studies that they believed, on the basis of their knowledge and clinical experience, were useful in making a diagnosis of NMS. In subsequent survey rounds, panel members assigned priority points to these items, and items that failed to receive a minimum priority score were eliminated from the next round. Information about individual panel member responses was fed back to the group anonymously in the form of the group median or mean and the number of members who had ranked or scored each survey item. The a priori consensus endpoint was defined operationally as a change of 10% or less in the mean priority score for any individual item, and an average absolute value change of 5% or less across all items, between consecutive rounds. The survey was conducted from January 2009 through September 2009.
Consensus was reached on the fifth round regarding the following criteria: recent dopamine antagonist exposure, or dopamine agonist withdrawal; hyperthermia; rigidity; mental status alteration; creatine kinase elevation; sympathetic nervous system lability; tachycardia plus tachypnea; and a negative work-up for other causes. The panel also reached a consensus on the relative importance of these criteria and on the following critical values for quantitative criteria: hyperthermia, > 100.4°F or > 38.0°C on at least 2 occasions; creatine kinase elevation, at least 4 times the upper limit of normal; blood pressure elevation, ≥ 25% above baseline; blood pressure fluctuation, ≥ 20 mm Hg (diastolic) or ≥ 25 mm Hg (systolic) change within 24 hours; tachycardia, ≥ 25% above baseline; and tachypnea, ≥ 50% above baseline.
These diagnostic criteria significantly advance the field because they represent the consensus of an international multispecialty expert panel, include critical values, provide guidance regarding the relative importance of individual elements, and are less influenced by particular theoretical biases than most previously published criteria. They require validation before being applied in clinical settings.
An expanded hexanucleotide repeat in C9orf72 causes amyotrophic lateral sclerosis and frontotemporal dementia (c9FTD/ALS). Therapeutics are being developed to target RNAs containing the expanded ...repeat sequence (GGGGCC); however, this approach is complicated by the presence of antisense strand transcription of expanded GGCCCC repeats. We found that targeting the transcription elongation factor Spt4 selectively decreased production of both sense and antisense expanded transcripts, as well as their translated dipeptide repeat (DPR) products, and also mitigated degeneration in animal models. Knockdown of SUPT4H1, the human Spt4 ortholog, similarly decreased production of sense and antisense RNA foci, as well as DPR proteins, in patient cells. Therapeutic targeting of a single factor to eliminate c9FTD/ALS pathological features offers advantages over approaches that require targeting sense and antisense repeats separately.
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The protective antigen component of Bacillus anthracis toxins can interact with at least three distinct proteins on the host cell surface, capillary morphogenesis gene 2 (CMG2), tumor endothelial ...marker 8, and β ₁-integrin, and, with the assistance of other host proteins, enters targeted cells by receptor-mediated endocytosis. Using an antisense-based phenotypic screen, we discovered the role of calpains in this process. We show that functions of a ubiquitous Ca ²⁺-dependent cysteine protease, calpain-2, and of the calpain substrate talin-1 are exploited for association of anthrax toxin and its principal receptor, CMG2, with higher-order actin filaments and consequently for toxin entry into host cells. Down-regulated expression of calpain-2 or talin-1, or pharmacological interference with calpain action, did not affect toxin binding but reduced endocytosis and increased the survival of cells exposed to anthrax lethal toxin. Adventitious expression of wild-type talin-1 promoted toxin endocytosis and lethality, whereas expression of a talin-1 mutant (L432G) that is insensitive to calpain cleavage did not. Disruption of talin-1, which links integrin-containing focal adhesion complexes to the actin cytoskeleton, facilitated association of toxin bound to its principal cell-surface receptor, CMG2, with higher-order actin filaments undergoing dynamic disassembly and reassembly during endocytosis. Our results reveal a mechanism by which a bacterial toxin uses constitutively occurring calpain-mediated cytoskeletal rearrangement for internalization.
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