Showing papers by "University of Würzburg published in 2003"
TL;DR: Cancer cells possess a broad spectrum of migration and invasion mechanisms and learning more about the cellular and molecular basis of these different migration/invasion programmes will help to understand how cancer cells disseminate and lead to new treatment strategies.
Abstract: Cancer cells possess a broad spectrum of migration and invasion mechanisms. These include both individual and collective cell-migration strategies. Cancer therapeutics that are designed to target adhesion receptors or proteases have not proven to be effective in slowing tumour progression in clinical trials — this might be due to the fact that cancer cells can modify their migration mechanisms in response to different conditions. Learning more about the cellular and molecular basis of these different migration/invasion programmes will help us to understand how cancer cells disseminate and lead to new treatment strategies.
3,064 citations
TL;DR: In this paper, the authors used sequence typing of the spa gene repeat region to study the epidemiology of MRSA at a German university hospital during two periods of 10 and 4 months, respectively.
Abstract: The spa gene of Staphylococcus aureus encodes protein A and is used for typing of methicillin-resistant Staphylococcus aureus (MRSA) We used sequence typing of the spa gene repeat region to study the epidemiology of MRSA at a German university hospital One hundred seven and 84 strains were studied during two periods of 10 and 4 months, respectively Repeats and spa types were determined by Ridom StaphType, a novel software tool allowing rapid repeat determination, data management and retrieval, and Internet-based assignment of new spa types following automatic quality control of DNA sequence chromatograms Isolates representative of the most abundant spa types were subjected to multilocus sequence typing and pulsed-field gel electrophoresis One of two predominant spa types was replaced by a clonally related variant in the second study period Ten unique spa types, which were equally distributed in both study periods, were recovered The data show a rapid dynamics of clone circulation in a university hospital setting spa typing was valuable for tracking of epidemic isolates The data show that disproval of epidemiologically suggested transmissions of MRSA is one of the main objectives of spa typing in departments with a high incidence of MRSA
1,544 citations
TL;DR: Molecular modeling suggests that available rhinovirus 3Cpro inhibitors may be modified to make them useful for treating SARS, and a homology model for SARS coronavirus (SARS-CoV) Mpro is constructed.
Abstract: A novel coronavirus has been identified as the causative agent of severe acute respiratory syndrome (SARS). The viral main proteinase (Mpro, also called 3CLpro), which controls the activities of the coronavirus replication complex, is an attractive target for therapy. We determined crystal structures for human coronavirus (strain 229E) Mpro and for an inhibitor complex of porcine coronavirus [transmissible gastroenteritis virus (TGEV)] Mpro, and we constructed a homology model for SARS coronavirus (SARS-CoV) Mpro. The structures reveal a remarkable degree of conservation of the substrate-binding sites, which is further supported by recombinant SARS-CoV Mpro-mediated cleavage of a TGEV Mpro substrate. Molecular modeling suggests that available rhinovirus 3Cpro inhibitors may be modified to make them useful for treating SARS.
1,503 citations
TL;DR: The transition from proteolytic mesenchymal toward nonproteolytic amoeboid movement highlights a supramolecular plasticity mechanism in cell migration and further represents a putative escape mechanism in tumor cell dissemination after abrogation of pericellular proteolysis.
Abstract: Invasive tumor dissemination in vitro and in vivo involves the proteolytic degradation of ECM barriers. This process, however, is only incompletely attenuated by protease inhibitor–based treatment, suggesting the existence of migratory compensation strategies. In three-dimensional collagen matrices, spindle-shaped proteolytically potent HT-1080 fibrosarcoma and MDA-MB-231 carcinoma cells exhibited a constitutive mesenchymal-type movement including the coclustering of β1 integrins and MT1–matrix metalloproteinase (MMP) at fiber bindings sites and the generation of tube-like proteolytic degradation tracks. Near-total inhibition of MMPs, serine proteases, cathepsins, and other proteases, however, induced a conversion toward spherical morphology at near undiminished migration rates. Sustained protease-independent migration resulted from a flexible amoeba-like shape change, i.e., propulsive squeezing through preexisting matrix gaps and formation of constriction rings in the absence of matrix degradation, concomitant loss of clustered β1 integrins and MT1-MMP from fiber binding sites, and a diffuse cortical distribution of the actin cytoskeleton. Acquisition of protease-independent amoeboid dissemination was confirmed for HT-1080 cells injected into the mouse dermis monitored by intravital multiphoton microscopy. In conclusion, the transition from proteolytic mesenchymal toward nonproteolytic amoeboid movement highlights a supramolecular plasticity mechanism in cell migration and further represents a putative escape mechanism in tumor cell dissemination after abrogation of pericellular proteolysis.
1,444 citations
TL;DR: Genetic intervention in the fly Drosophila melanogaster has provided strong evidence that the mushroom bodies of the insect brain act as the seat of a memory trace for odours, and the development of a circuit model that addresses this function might allow the mushrooms to throw light on the basic operating principles of the brain.
Abstract: Genetic intervention in the fly Drosophila melanogaster has provided strong evidence that the mushroom bodies of the insect brain act as the seat of a memory trace for odours. This localization gives the mushroom bodies a place in a network model of olfactory memory that is based on the functional anatomy of the olfactory system. In the model, complex odour mixtures are assumed to be represented by activated sets of intrinsic mushroom body neurons. Conditioning renders an extrinsic mushroom-body output neuron specifically responsive to such a set. Mushroom bodies have a second, less understood function in the organization of the motor output. The development of a circuit model that also addresses this function might allow the mushroom bodies to throw light on the basic operating principles of the brain.
1,189 citations
TL;DR: It is argued that to understand the variable consequences of comparison, one has to examine what target knowledge is activated during the comparison process, which is conceptualized in a selective accessibility model that distinguishes 2 fundamental comparison processes.
Abstract: This article proposes an informational perspective on comparison consequences in social judgment. It is argued that to understand the variable consequences of comparison, one has to examine what target knowledge is activated during the comparison process. These informational underpinnings are conceptualized in a selective accessibility model that distinguishes 2 fundamental comparison processes. Similarity testing selectively makes accessible knowledge indicating target-standard similarity, whereas dissimilarity testing selectively makes accessible knowledge indicating target-standard dissimilarity. These respective subsets of target knowledge build the basis for subsequent target evaluations, so that similarity testing typically leads to assimilation whereas dissimilarity testing typically leads to contrast. The model is proposed as a unifying conceptual framework that integrates diverse findings on comparison consequences in social judgment.
1,167 citations
TL;DR: These newly recognized viral enzymes place the mechanism of coronavirus RNA synthesis in a completely new perspective and will be important targets for the design of antiviral strategies aimed at controlling the further spread of SARS-CoV.
1,114 citations
TL;DR: Analysis of the Arabidopsis mutant npr1 revealed that the antagonistic effect of SA on JA signaling requires the regulatory protein NPR1, indicating that cross-talk between SA and JA is modulated through a novel function of NPR1 in the cytosol.
Abstract: Plant defenses against pathogens and insects are regulated differentially by cross-communicating signal transduction pathways in which salicylic acid (SA) and jasmonic acid (JA) play key roles. In this study, we investigated the molecular mechanism of the antagonistic effect of SA on JA signaling. Arabidopsis plants unable to accumulate SA produced 25-fold higher levels of JA and showed enhanced expression of the JA-responsive genes LOX2, PDF1.2, and VSP in response to infection by Pseudomonas syringae pv tomato DC3000, indicating that in wild-type plants, pathogen-induced SA accumulation is associated with the suppression of JA signaling. Analysis of the Arabidopsis mutant npr1, which is impaired in SA signal transduction, revealed that the antagonistic effect of SA on JA signaling requires the regulatory protein NPR1. Nuclear localization of NPR1, which is essential for SA-mediated defense gene expression, is not required for the suppression of JA signaling, indicating that cross-talk between SA and JA is modulated through a novel function of NPR1 in the cytosol.
1,088 citations
National Institutes of Health1, University of British Columbia2, University of Nebraska Medical Center3, University of Oslo4, University of Barcelona5, University of Würzburg6, Oregon Health & Science University7, University of Arizona8, University of Rochester9, Fred Hutchinson Cancer Research Center10
TL;DR: Gene expression profiling strongly supported a relationship between PMBL and Hodgkin lymphoma: over one third of the genes that were more highly expressed in PMBL than in other DLBCLs were also characteristically expressed in Hodgkinymphoma cells.
Abstract: Using current diagnostic criteria, primary mediastinal B cell lymphoma (PMBL) cannot be distinguished from other types of diffuse large B cell lymphoma (DLBCL) reliably. We used gene expression profiling to develop a more precise molecular diagnosis of PMBL. PMBL patients were considerably younger than other DLBCL patients, and their lymphomas frequently involved other thoracic structures but not extrathoracic sites typical of other DLBCLs. PMBL patients had a relatively favorable clinical outcome, with a 5-yr survival rate of 64% compared with 46% for other DLBCL patients. Gene expression profiling strongly supported a relationship between PMBL and Hodgkin lymphoma: over one third of the genes that were more highly expressed in PMBL than in other DLBCLs were also characteristically expressed in Hodgkin lymphoma cells. PDL2, which encodes a regulator of T cell activation, was the gene that best discriminated PMBL from other DLBCLs and was also highly expressed in Hodgkin lymphoma cells. The genomic loci for PDL2 and several neighboring genes were amplified in over half of the PMBLs and in Hodgkin lymphoma cell lines. The molecular diagnosis of PMBL should significantly aid in the development of therapies tailored to this clinically and pathogenetically distinctive subgroup of DLBCL.
1,039 citations
TL;DR: A metric for probability distributions is introduced, which is bounded, information-theoretically motivated, and has a natural Bayesian interpretation, and the square root of the well-known /spl chi//sup 2/ distance is an asymptotic approximation.
Abstract: We introduce a metric for probability distributions, which is bounded, information-theoretically motivated, and has a natural Bayesian interpretation. The square root of the well-known /spl chi//sup 2/ distance is an asymptotic approximation to it. Moreover, it is a close relative of the capacitory discrimination and Jensen-Shannon divergence.
1,028 citations
TL;DR: Evidence-based guidelines developed by an international panel of experts for the management of postoperative nausea and vomiting are presented.
Abstract: IMPLICATIONS We present evidence-based guidelines developed by an international panel of experts for the management of postoperative nausea and vomiting.
TL;DR: Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions.
Abstract: Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Polynesia and the Americas, the neolithic introduction of farming to Europe, the Bantu expansion within Africa, and the slave trade.
TL;DR: A quantitative model of the aberrant cell cycle regulation in MCL is proposed that provides a rationale for the design of cell cycle inhibitor therapy in this malignancy.
TL;DR: AHSG deficiency is associated with inflammation and links vascular calcification to mortality in patients on dialysis and might account for accelerated atherosclerosis in uraemia.
TL;DR: The mitochondrial proteome will provide an important database for the analysis of new mitochondrial and mitochondria-associated functions and the characterization of mitochondrial diseases.
Abstract: We performed a comprehensive approach to determine the proteome of Saccharomyces cerevisiae mitochondria. The proteins of highly pure yeast mitochondria were separated by several independent methods and analyzed by tandem MS. From >20 million MS spectra, 750 different proteins were identified, indicating an involvement of mitochondria in numerous cellular processes. All known components of the oxidative phosphorylation machinery, the tricarboxylic acid cycle, and the stable mitochondria-encoded proteins were found. Based on the mitochondrial proteins described in the literature so far, we calculate that the identified proteins represent ≈90% of all mitochondrial proteins. The function of a quarter of the identified proteins is unknown. The mitochondrial proteome will provide an important database for the analysis of new mitochondrial and mitochondria-associated functions and the characterization of mitochondrial diseases.
TL;DR: The availability of recombinant forms of key replicative enzymes of SARS coronavirus should pave the way for high-throughput screening approaches to identify candidate inhibitors in compound libraries.
Abstract: A novel coronavirus is the causative agent of the current epidemic of severe acute respiratory syndrome (SARS). Coronaviruses are exceptionally large RNA viruses and employ complex regulatory mechanisms to express their genomes. Here, we determined the sequence of SARS coronavirus (SARS-CoV), isolate Frankfurt 1, and characterized key RNA elements and protein functions involved in viral genome expression. Important regulatory mechanisms, such as the (discontinuous) synthesis of eight subgenomic mRNAs, ribosomal frameshifting and post-translational proteolytic processing, were addressed. Activities of three SARS coronavirus enzymes, the helicase and two cysteine proteinases, which are known to be critically involved in replication, transcription and/or post-translational polyprotein processing, were characterized. The availability of recombinant forms of key replicative enzymes of SARS coronavirus should pave the way for high-throughput screening approaches to identify candidate inhibitors in compound libraries.
TL;DR: It is shown that motoneurons isolated from an SMA mouse model exhibit normal survival, but reduced axon growth, and data suggest that a complex of Smn with its binding partner hnRNP R interacts with β-actin mRNA and translocates to axons and growth cones of mot oneurons.
Abstract: Spinal muscular atrophy (SMA), a common autosomal recessive form of motoneuron disease in infants and young adults, is caused by mutations in the survival motoneuron 1 (SMN1) gene. The corresponding gene product is part of a multiprotein complex involved in the assembly of spliceosomal small nuclear ribonucleoprotein complexes. It is still not understood why reduced levels of the ubiquitously expressed SMN protein specifically cause motoneuron degeneration. Here, we show that motoneurons isolated from an SMA mouse model exhibit normal survival, but reduced axon growth. Overexpression of Smn or its binding partner, heterogeneous nuclear ribonucleoprotein (hnRNP) R, promotes neurite growth in differentiating PC12 cells. Reduced axon growth in Smn-deficient motoneurons correlates with reduced β-actin protein and mRNA staining in distal axons and growth cones. We also show that hnRNP R associates with the 3′ UTR of β-actin mRNA. Together, these data suggest that a complex of Smn with its binding partner hnRNP R interacts with β-actin mRNA and translocates to axons and growth cones of motoneurons.
TL;DR: This study suggests that strict temporal Hebbian rules govern the induction of long-term potentiation/long-term depression-like phenomena in vivo in the human primary motor cortex.
Abstract: Synaptic plasticity is conspicuously dependent on the temporal order of the pre- and postsynaptic activity. Human motor cortical excitability can be increased by a paired associative stimulation (P...
University of California, Irvine1, Oregon Health & Science University2, Merck & Co.3, University of Virginia4, Harvard University5, Thomas Jefferson University6, Yale University7, Astellas Pharma8, University of Wisconsin-Madison9, University of Ulm10, University of California, San Francisco11, University of Würzburg12, Rosalind Franklin University of Medicine and Science13, Vanderbilt University14, Osaka University15, Centre national de la recherche scientifique16, California Institute of Technology17, Stony Brook University18, Washington University in St. Louis19, King's College London20, New York University21, University of Utah22, Chiba University23, Max Planck Society24, Colorado State University25, University of California, Santa Barbara26, University of Tulsa27
TL;DR: An overview of the molecular relationships among the voltage-gated potassium channels and a standard nomenclature for them is derived from the IUPHAR Compendium of Voltage-Gated Ion Channels as mentioned in this paper.
Abstract: This summary article presents an overview of the molecular relationships among the voltage-gated potassium channels and a standard nomenclature for them, which is derived from the IUPHAR Compendium of Voltage-Gated Ion Channels.1 The complete Compendium, including data tables for each member of the potassium channel family can be found at http://www.iuphar-db.org/iuphar-ic/.
TL;DR: It is shown that viral Src transformation of FAK−/− cells promotes integrin-stimulated motility equal to stable FAK reexpression, and a dual role for FAK in promoting cell motility and invasion through the activation of distinct signaling pathways.
Abstract: Cell migration and invasion are fundamental components of tumor cell metastasis. Increased focal adhesion kinase (FAK) expression and tyrosine phosphorylation are connected with elevated tumorigenesis. Null mutation of FAK results in embryonic lethality, and FAK−/− fibroblasts exhibit cell migration defects in culture. Here we show that viral Src (v-Src) transformation of FAK−/− cells promotes integrin-stimulated motility equal to stable FAK reexpression. However, FAK−/− v-Src cells were not invasive, and FAK reexpression, Tyr-397 phosphorylation, and FAK kinase activity were required for the generation of an invasive cell phenotype. Cell invasion was linked to transient FAK accumulation at lamellipodia, formation of a FAK–Src-p130Cas–Dock180 signaling complex, elevated Rac and c-Jun NH2-terminal kinase activation, and increased matrix metalloproteinase expression and activity. Our studies support a dual role for FAK in promoting cell motility and invasion through the activation of distinct signaling pathways.
TL;DR: The value of Arabidopsis for studies of the biosynthesis and ecological role of terpenoids is demonstrated and new insights into their metabolism in wild-type and transgenic plants are provided.
Abstract: Volatile components, such as terpenoids, are emitted from aerial parts of plants and play a major role in the interaction between plants and their environment. Analysis of the composition and emission pattern of volatiles in the model plant Arabidopsis showed that a range of volatile components are released, primarily from flowers. Most of the volatiles detected were monoterpenes and sesquiterpenes, which in contrast to other volatiles showed a diurnal emission pattern. The active terpenoid metabolism in wild-type Arabidopsis provoked us to conduct an additional set of experiments in which transgenic Arabidopsis overexpressing two different terpene synthases were generated. Leaves of transgenic plants constitutively expressing a dual linalool/nerolidol synthase in the plastids (FaNES1) produced linalool and its glycosylated and hydroxylated derivatives. The sum of glycosylated components was in some of the transgenic lines up to 40- to 60-fold higher than the sum of the corresponding free alcohols. Surprisingly, we also detected the production and emission of nerolidol, albeit at a low level, suggesting that a small pool of its precursor farnesyl diphosphate is present in the plastids. Transgenic lines with strong transgene expression showed growth retardation, possibly as a result of the depletion of isoprenoid precursors in the plastids. In dual-choice assays with Myzus persicae, the FaNES1-expressing lines significantly repelled the aphids. Overexpression of a typical cytosolic sesquiterpene synthase resulted in the production of only trace amounts of the expected sesquiterpene, suggesting tight control of the cytosolic pool of farnesyl diphosphate, the precursor for sesquiterpenoid biosynthesis. This study further demonstrates the value of Arabidopsis for studies of the biosynthesis and ecological role of terpenoids and provides new insights into their metabolism in wild-type and transgenic plants.
TL;DR: A sequential role for TNF and p38 in the induction of neuropathic pain is suggested and parallel inhibition of p38 activation and allodynia may represent a clinically relevant therapeutic window.
Abstract: Tumor necrosis factor-α (TNF) is implicated in the initiation of neuropathic pain. In vitro, TNF activates p38 mitogen-activated kinase. Accordingly, we investigated whether TNF activates the p38 cascade in vivo to trigger pain behavior after spinal nerve ligation (SNL). Treatment starting 2 d before SNL with the TNF antagonist etanercept (1 mg, i.p., every third day) attenuated mechanical allodynia. Treatment starting 1 or 7 d after SNL was ineffective. Similarly, intrathecal infusion of a p38 inhibitor (SB203580, 4 mg/d) was effective only if it was started before but not 7 d after SNL. For both treatments, the cessation of therapy resulted in increased allodynia. In separate experiments using Western blots and immunohistochemistry, ipsilateral lumbar spinal cord and L5 and L6 DRG were analyzed for total and phosphorylated p38 after SNL alone or SNL combined with etanercept pretreatment. In DRG, activated p38 was transiently elevated 5 hr after SNL and returned to baseline by 1 d after SNL. Phosphorylated p38 was localized in small TNF-positive DRG neurons. In spinal cord, p38 was activated between 5 hr and 3 d after SNL and returned to baseline within 5 d. In DRG, but not spinal cord, etanercept pretreatment blocked p38 activation. These data indicate that after SNL treatment, phosphorylated p38 levels in spinal cord and DRG are transiently elevated. In DRG, p38 activation is blocked by systemic TNF inhibition. Parallel inhibition of p38 activation and allodynia may represent a clinically relevant therapeutic window. These data suggest a sequential role for TNF and p38 in the induction of neuropathic pain.
TL;DR: An unexpected role of GPVI is revealed in the initiation of platelet attachment at sites of vascular injury and platelet–collagen interactions (via GPVI) is identified as the major determinant of arterial thrombus formation.
Abstract: Platelet adhesion and aggregation at sites of vascular injury is crucial for hemostasis but may lead to arterial occlusion in the setting of atherosclerosis and precipitate diseases such as myocardial infarction. A current hypothesis suggests that platelet glycoprotein (GP) Ib interaction with von Willebrand factor recruits flowing platelets to the injured vessel wall, where subendothelial fibrillar collagens support their firm adhesion and activation. However, so far this hypothesis has not been tested in vivo. Here, we demonstrate by intravital fluorescence microscopy of the mouse carotid artery that inhibition or absence of the major platelet collagen receptor, GPVI, abolishes platelet-vessel wall interactions after endothelial denudation. Unexpectedly, inhibition of GPVI by the monoclonal antibody JAQ1 reduced platelet tethering to the subendothelium by approximately 89%. In addition, stable arrest and aggregation of platelets was virtually abolished under these conditions. Using different models of arterial injury, the strict requirement for GPVI in these processes was confirmed in GPVI-deficient mice, where platelets also failed to adhere and aggregate on the damaged vessel wall. These findings reveal an unexpected role of GPVI in the initiation of platelet attachment at sites of vascular injury and unequivocally identify platelet-collagen interactions (via GPVI) as the major determinant of arterial thrombus formation.
TL;DR: Based on the observed co-ordinated regulation of source/sink relations and defence responses by sugars and stress-related stimuli, the identified activation of distinct subsets of MAP kinases provides a mechanism for signal integration and distribution within such complex networks.
Abstract: Extracellular invertase is the key enzyme of an apoplasmic phloem unloading pathway and catalyses the hydrolytic cleavage of the transport sugar sucrose released into the apoplast. This mechanism contributes to long-distance assimilate transport, provides the substrate to sustain heterotrophic growth and generates metabolic signals known to effect various processes of primary metabolism and defence responses. The essential function of extracellular invertase for supplying carbohydrates to sink organs was demonstrated by the finding that antisense repression of an anther-specific isoenzyme provides an efficient method for metabolic engineering of male sterility. The regulation of extracellular invertase by all classes of phytohormones indicates an essential link between the molecular mechanism of phytohormone action and primary metabolism. The up-regulation of extracellular invertase appears to be a common response to various biotic and abiotic stress-related stimuli such as pathogen infection and salt stress, in addition to specific stress-related reactions. Based on the observed co-ordinated regulation of source/sink relations and defence responses by sugars and stress-related stimuli, the identified activation of distinct subsets of MAP kinases provides a mechanism for signal integration and distribution within such complex networks. Sucrose derivatives not synthesized by higher plants, such as turanose, were shown to elicit responses distinctly different from metabolizable sugars and are rather perceived as stress-related stimuli.
TL;DR: Together, amoeboid shape change and contact guidance provide constitutive protease-independent mechanisms for leukocyte trafficking through interstitial tissues that are insensitive toward pharmacologic protease inhibitors.
TL;DR: A generally applicable fluorescence-based technique is developed that allows the comparison of agonist and partial agonist intrinsic activities at the receptor level and provides evidence for millisecond activation times of GPCRs.
Abstract: Hormones and neurotransmitters transduce signals through G protein-coupled receptors (GPCR). Despite their common signaling pathways, however, the responses they elicit have different temporal patterns. To reveal the molecular basis for these differences we have developed a generally applicable fluorescence-based technique for real-time monitoring of the activation switch of GPCRs in living cells. We used such direct measurements to investigate the activation of the alpha(2A)-adrenergic receptor (alpha(2A)AR; neurotransmitter) and the parathyroid hormone receptor (PTHR; hormone) and observed much faster kinetics than expected: approximately 40 ms for the alpha(2A)AR and approximately 1 s for the PTHR. The different switch times are in agreement with the different receptors' biological functions. Agonists and antagonists could rapidly switch the receptors on or off, whereas a partial agonist caused only a partial signal. This approach allows the comparison of agonist and partial agonist intrinsic activities at the receptor level and provides evidence for millisecond activation times of GPCRs.
TL;DR: It is found that Gi proteins activate within 1-2 s, which is considerably slower than activation kinetics of the receptors themselves, which will be of particular interest for unraveling Gβγ-induced signaling pathways.
Abstract: G protein-coupled receptors transduce diverse extracellular signals, such as neurotransmitters, hormones, chemokines, and sensory stimuli, into intracellular responses through activation of heterotrimeric G proteins. G proteins play critical roles in determining specificity and kinetics of subsequent biological responses by modulation of effector proteins. We have developed a fluorescence resonance energy transfer (FRET)-based assay to directly measure mammalian G protein activation in intact cells and found that Gi proteins activate within 1-2 s, which is considerably slower than activation kinetics of the receptors themselves. More importantly, FRET measurements demonstrated that Galphai- and Gbetagamma-subunits do not dissociate during activation, as has been previously postulated. Based on FRET measurements between Galphai-yellow fluorescent protein and Gbetagamma-subunits that were fused to cyan fluorescent protein at various positions, we conclude that, instead, G protein subunits undergo a molecular rearrangement during activation. The detection of a persistent heterotrimeric composition during G protein activation will impact the understanding of how G proteins achieve subtype-selective coupling to effectors. This finding will be of particular interest for unraveling Gbetagamma-induced signaling pathways.
TL;DR: The clinical and molecular parallels between DM1 and DM2 indicate that the multisystemic features common to both diseases are caused by CUG or CCUG expansions expressed at the RNA level.
Abstract: Background: Myotonic dystrophy types 1 (DM1) and 2 (DM2/proximal myotonic myopathy PROMM) are dominantly inherited disorders with unusual multisystemic clinical features. The authors have characterized the clinical and molecular features of DM2/PROMM, which is caused by a CCTG repeat expansion in intron 1 of the zinc finger protein 9 (ZNF9) gene. Methods: Three-hundred and seventy-nine individuals from 133 DM2/PROMM families were evaluated genetically, and in 234 individuals clinical and molecular features were compared. Results: Among affected individuals 90% had electrical myotonia, 82% weakness, 61% cataracts, 23% diabetes, and 19% cardiac involvement. Because of the repeat tract’s unprecedented size (mean ∼5,000 CCTGs) and somatic instability, expansions were detectable by Southern analysis in only 80% of known carriers. The authors developed a repeat assay that increased the molecular detection rate to 99%. Only 30% of the positive samples had single sizeable expansions by Southern analysis, and 70% showed multiple bands or smears. Among the 101 individuals with single expansions, repeat size did not correlate with age at disease onset. Affected offspring had markedly shorter expansions than their affected parents, with a mean size difference of −17 kb (−4,250 CCTGs). Conclusions: DM2 is present in a large number of families of northern European ancestry. Clinically, DM2 resembles adult-onset DM1, with myotonia, muscular dystrophy, cataracts, diabetes, testicular failure, hypogammaglobulinemia, and cardiac conduction defects. An important distinction is the lack of a congenital form of DM2. The clinical and molecular parallels between DM1 and DM2 indicate that the multisystemic features common to both diseases are caused by CUG or CCUG expansions expressed at the RNA level.
TL;DR: Bees are the first example of an insect to show between-individual and within-individual speed– accuracy trade-offs, and each bee will sacrifice speed in favour of accuracy when errors are penalized.
Abstract: Bees have an impressive cognitive capacity1,2,3,4, but the strategies used by individuals in solving foraging tasks have been largely unexplored. Here we test bumblebees (Bombus terrestris) in a colour-discrimination task on a virtual flower meadow and find that some bees consistently make rapid choices but with low precision, whereas other bees are slower but highly accurate. Moreover, each bee will sacrifice speed in favour of accuracy when errors are penalized instead of just being unrewarded. To our knowledge, bees are the first example of an insect to show between-individual and within-individual speed– accuracy trade-offs.
TL;DR: expression of the cathelicidin LL-37 in colonocytes and cellular differentiation are separately modulated by SCFA via distinct signalling pathways, which may provide a rationale for dietary modulation of mucosal defence mechanisms.
Abstract: Background and aims: Short chain fatty acids (SCFA) exert profound effects on the colonic mucosa. In particular, SCFA modulate mucosal immune functions. The antimicrobial cathelicidin LL-37 is expressed by colon epithelial cells. In the present study the effect of SCFA on LL-37 expression was investigated.
Methods: LL-37 expression in vivo was assessed by immunohistochemistry. Real time quantitative reverse transcription-polymerase chain reaction was employed to determine LL-37 expression in colonocytes in vitro after treatment with various cytokines, SCFA, or flavone. LL-37 levels were correlated to cell differentiation which was determined by alkaline phosphatase (AP) activity. In addition, intracellular signalling pathways such as MEK-ERK (mitogen/extracellular signal protein kinase (MEK)/extracellular signal regulated protein kinase (ERK)) and p38/mitogen activated protein (MAP) kinase were explored.
Results: In vivo, LL-37 expression in healthy mucosa was restricted to differentiated epithelial cells in human colon and ileum. In colonocytes, increased LL-37 expression associated with cell differentiation was detected in vitro following treatment with butyrate, isobutyrate, propionate, and trichostatin A. Flavone induced LL-37 transcription but did not affect AP activity while cytokines had no effect. To dissect pathways mediating differentiation and LL-37 expression, specific inhibitors were applied. Inhibition of the protein kinase MEK enhanced butyrate induced AP activity while LL-37 expression in colon epithelial cells was blocked. In contrast, inhibition of p38/MAP kinase blocked cell differentiation without inhibiting LL-37 expression.
Conclusions: Expression of the cathelicidin LL-37 in colonocytes and cellular differentiation are separately modulated by SCFA via distinct signalling pathways. These data may provide a rationale for dietary modulation of mucosal defence mechanisms.