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Edinburgh, United Kingdom

Van Breemen C.,University of British Columbia | Fameli N.,University of British Columbia | Evans A.M.,Center for Integrative Physiology
Journal of Physiology | Year: 2013

Abstract This review focuses on how smooth muscle sarcoplasmic reticulum (SR), the major releasable Ca2+ store in these cells, performs its many functions by communicating with the plasma membrane (PM) and other organelles across cytoplasmic nanospaces, defined by membrane-membrane junctions less than 50 nm across. In spite of accumulating evidence in favour of the view that cytoplasmic nanospaces are a prerequisite for effective control of diverse cellular functions, our current understanding of how smooth muscle cells accomplish site- and function-specific Ca2+ signalling remains in its infancy. We first present evidence in support of the view that effective Ca2+ signalling depends on the restricted diffusion of Ca2+ within cytoplasmic nanospaces. We then develop an evidence-based model of the smooth muscle SR - the 'pan-junctional SR' model - that incorporates a network of tubules and quilts that are capable of auto-regulating their Ca2+ content and determining junctional [Ca2+]i through loading and unloading at membrane-membrane nanojunctions. Thereby, we provide a novel working hypothesis in order to inform future investigation into the control of a variety of cellular functions by local Ca2+ signals at junctional nanospaces, from contraction and energy metabolism to nuclear transcription. Based on the current literature, we discuss the molecular mechanisms whereby the SR mediates these multiple functions through the interaction of ion channels and pumps embedded in apposing membranes within inter-organellar junctions. We finally highlight the fact that although most current hypotheses are qualitatively supported by experimental data, solid quantitative simulations are seriously lacking. Considering that at physiological concentrations the number of calcium ions in a typical junctional nanospace between the PM and SR is of the order of 1, ion concentration variability plays a major role as the currency of information transfer and stochastic quantitative modelling will be required to both test and develop working hypotheses. © 2013 The Physiological Society. Source


Brydges N.M.,University of Edinburgh | Argyle D.J.,Roslin Institute | Mosley J.R.,Roslin Institute | Duncan J.C.,Roslin Institute | And 3 more authors.
Veterinary Journal | Year: 2012

Dogs with chronic pain have a compromised quality of life. Repeatable and accurate sensory assessments form a means by which the hypersensitivity likely to reflect chronic pain may be quantified. These assessments can be applied to individuals to identify those that may benefit from improved analgesic relief. In this study four sensory assessments were evaluated in dogs presenting with a naturally occurring chronic painful condition (cranial cruciate ligament rupture, CCLR) and were compared with healthy control animals of similar age and weight. Inter-digital von Frey filament and thermal sensitivity tests revealed that the affected hind limb of dogs with CCLR was significantly more sensitive than the opposing limb. Static weight bearing and gait parameter scores were also reduced in the affected hind limb compared to the opposing hind limb of dogs with CCLR; no such differences were found between the hind limbs of healthy (control) dogs. The quantitative sensory tests permitted the differentiation of limbs affected by CCLR from healthy limbs. Dogs presenting with CCLR demonstrate objectively quantitative sensory sensitivities, which may require additional consideration in case management. © 2012 Elsevier Ltd. Source


Brose N.,Max Planck Institute for Experimental Medicine | O'Connor V.,University of Southampton | Skehel P.,Center for Integrative Physiology
Biochemical Society Transactions | Year: 2010

Synaptopathy is an increasingly popular term used to define key features of neurodegenerative and psychiatric disease. It implies that disruptions in synaptic structure and function are potentially the major determinant of such brain diseases. The Synaptopathies: Dysfunction of Synaptic Function Biochemical Society Focused Meeting brought together several invited speakers, supplemented with short communications from young scientists, who addressed this possibility. The talks spanned the full gamut of approaches that brought molecular, cellular, systems and whole-animal experimentation together to address how fundamental synaptic biology was increasingly informing on dysfunction in disease. The disease and models thereof discussed included Alzheimer's disease, prions, Huntington's disease, Parkinson's disease, schizophrenia and autism. The audience were asked to reflect on whether synaptopathy, although attractive and conceptually useful, provided a significant explanation as the cause of these major diseases. The breadth of the meeting reinforced the complexity of these brain diseases, supported the significance of synaptic dysfunction in disease, but left open the issue as to whether the prime cause of these disorders could be resolved as simple synaptic dysfunction. Thus, despite revealing a value of synaptopathy, further investigation will be required to reveal its balance in the cause and effect in each of the major brain diseases. ©The Authors. Source


Robertson K.A.,University of Edinburgh | Hsieh W.Y.,University of Edinburgh | Forster T.,University of Edinburgh | Blanc M.,University of Edinburgh | And 23 more authors.
PLoS Biology | Year: 2016

In invertebrates, small interfering RNAs are at the vanguard of cell-autonomous antiviral immunity. In contrast, antiviral mechanisms initiated by interferon (IFN) signaling predominate in mammals. Whilst mammalian IFN-induced miRNA are known to inhibit specific viruses, it is not known whether host-directed microRNAs, downstream of IFN-signaling, have a role in mediating broad antiviral resistance. By performing an integrative, systematic, global analysis of RNA turnover utilizing 4-thiouridine labeling of newly transcribed RNA and pri/pre-miRNA in IFN-activated macrophages, we identify a new post-transcriptional viral defense mechanism mediated by miR-342-5p. On the basis of ChIP and site-directed promoter mutagenesis experiments, we find the synthesis of miR-342-5p is coupled to the antiviral IFN response via the IFN-induced transcription factor, IRF1. Strikingly, we find miR-342-5p targets mevalonate-sterol biosynthesis using a multihit mechanism suppressing the pathway at different functional levels: transcriptionally via SREBF2, post-transcriptionally via miR-33, and enzymatically via IDI1 and SC4MOL. Mass spectrometry-based lipidomics and enzymatic assays demonstrate the targeting mechanisms reduce intermediate sterol pathway metabolites and total cholesterol in macrophages. These results reveal a previously unrecognized mechanism by which IFN regulates the sterol pathway. The sterol pathway is known to be an integral part of the macrophage IFN antiviral response, and we show that miR-342-5p exerts broad antiviral effects against multiple, unrelated pathogenic viruses such Cytomegalovirus and Influenza A (H1N1). Metabolic rescue experiments confirm the specificity of these effects and demonstrate that unrelated viruses have differential mevalonate and sterol pathway requirements for their replication. This study, therefore, advances the general concept of broad antiviral defense through multihit targeting of a single host pathway. © 2016 Robertson et al. Source


Livesey M.R.,University of EdinburghEdinburgh United Kingdom | Magnani D.,University of EdinburghEdinburgh United Kingdom | Cleary E.M.,University of EdinburghEdinburgh United Kingdom | Vasistha N.A.,Euan MacDonald Center for Research | And 9 more authors.
Stem Cells | Year: 2016

Abstract: Rodent-based studies have shown that the membrane properties of oligodendrocytes play prominent roles in their physiology and shift markedly during their maturation from the oligodendrocyte precursor cell (OPC) stage. However, the conservation of these properties and maturation processes in human oligodendrocytes remains unknown, despite their dysfunction being implicated in human neurodegenerative diseases such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Here, we have defined the membrane properties of human oligodendrocytes derived from pluripotent stem cells as they mature from the OPC stage, and have identified strong conservation of maturation-specific physiological characteristics reported in rodent systems. We find that as human oligodendrocytes develop and express maturation markers, they exhibit a progressive decrease in voltage-gated sodium and potassium channels and a loss of tetrodotoxin-sensitive spiking activity. Concomitant with this is an increase in inwardly rectifying potassium channel activity, as well as a characteristic switch in AMPA receptor composition. All these steps mirror the developmental trajectory observed in rodent systems. Oligodendrocytes derived from mutant C9ORF72-carryng ALS patient induced pluripotent stem cells did not exhibit impairment to maturation and maintain viability with respect to control lines despite the presence of RNA foci, suggesting that maturation defects may not be a primary feature of this mutation. Thus, we have established that the development of human oligodendroglia membrane properties closely resemble those found in rodent cells and have generated a platform to enable the impact of human neurodegenerative disease-causing mutations on oligodendrocyte maturation to be studied. © 2016 The Authors STEM CELLS published by Wiley Periodicals, Inc. Source

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