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Neuron,
2002]
Nuclear pre-mRNA editing by selective adenosine deamination (A-to-I editing) occurs in all organisms from C. elegans to humans. This rare posttranscriptional mechanism can alter codons and hence the structure and function of proteins. New findings report new sites, give evidence that the efficiency of editing can be regulated by neurotransmitter, and reveal that an amino acid substitution introduced by editing into a neurotransmitter-gated ion channel subunit serves as a determinant for controlling the maturation, intracellular trafficking, and assembly with other subunits of this transmembrane protein.
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Methods Mol Biol,
2006]
Whether by patch-clamp techniques or the use of fluorescent vital dyes, measurements of transepithelial ion flux in mammals are limited by cell accessibility. Furthermore, redundant functions and complex regulatory mechanisms can mask loss-of-function phenotypes through compensatory mechanisms. In this chapter, we present a technique whereby the optically transparent nematode Caenorhabditis elegans, engineered to express a fluorescent pH indicator protein, can be used to study how intracellular pH (pHi) fluctuates in response to environmental and/or experimental challenge. By using a live whole animal model, systemic, and even behavioral relationships to individual cellular pHi can be inferred. In combination with dye loading of excised or cultured cells, this technique also provides a powerful means of contrasting these relationships to biophysical measurements of ion flux.
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Cell Cycle,
2010]
Carbon dioxide (CO2) is an end product of cellular respiration, a process by which organisms including all plants, animals, many fungi and some bacteria obtain energy. CO2 has several physiologic roles in respiration, pH buffering, autoregulation of the blood supply and others. Here we review recent findings from studies in mammalian lung cells, Caenorhabditis elegans and Drosophila melanogaster that help shed light on the molecular sensing and response to hypercapnia.
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Neuron,
2002]
The DEG/ENaC ion channel family contributes to channels of striking functional diversity. Neuronally expressed family members include the C. elegans degenerins that mediate touch and are thought to be mechanically gated, and the mammalian ASICs, which are gated by protons. ASICs affect a range of sensory functions that includes perception of gentle touch, harsh touch, heat, sour taste, and pain. Family member ASIC1 is now implicated in long-term potentiation, suggesting that minute fluxes in synaptic pH may activate ASICs to enhance learning.
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FEBS Lett,
2002]
Phospholipase D1 and D2 (PLD1, PLD2) both have PX and PH domains in their N-terminal regions with these inositol lipid binding domains playing key roles in regulating PLD activity and localisation. The activity of PLD1 is also regulated by protein kinase C and members of the Rho and Arf families of GTPases. Each of these proteins binds to unique sites; however, there appears to be little in vitro discrimination between individual family members. In agonist-stimulated cells, however, there is specificity, with, for example in RBL-2H3 cells, antigen stimulating the activation of PLD1 by association with Arf6, Rac1 and protein kinase Calpha. PLD2 appears to be less directly regulated by GTPases and rather is primarily controlled through interaction with phosphatidylinositol 4-phosphate 5-kinase that generates the activating phosphatidylinositol 4,5-bisphosphate.
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Trends in Pharmacological Sciences,
2005]
K+ channels that possess two pore domains in each channel subunit are common in many animal tissues. Such channels are generated from large families of subunits and are implicated in several functions, including temperature sensation, responses to ischaemia, K+ homeostasis and setting the resting potential of the cell. Their activity can be modulated by polyunsaturated fatty acids, pH and oxygen, and some are candidate targets of volatile anaesthetics. However, despite their potential as targets for novel drugs for human health, comparatively little is known about the molecular basis of their diverse physiological and pharmacological properties. Genetic model organisms have considerable potential for improving our understanding of these channels. In this article, we review the contributions of some of these genetic model organisms to recent advances in our knowledge of two-pore-domain K+
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Semin Nephrol,
2006]
The vacuolar H(+)-ATPase is a multisubunit protein consisting of a peripheral catalytic domain (V(1)) that binds and hydrolyzes adenosine triphosphate (ATP) and provides energy to pump H(+) through the transmembrane domain (V(0)) against a large gradient. This proton-translocating vacuolar H(+)-ATPase is present in both intracellular compartments and the plasma membrane of eukaryotic cells. Mutations in genes encoding kidney intercalated cell-specific V(0)
a4 and V(1) B1 subunits of the vacuolar H(+)-ATPase cause the syndrome of distal tubular renal acidosis. This review focuses on the function, regulation, and the role of vacuolar H(+)-ATPases in renal physiology. The localization of vacuolar H(+)-ATPases in the kidney, and their role in intracellular pH (pHi) regulation, transepithelial proton transport, and acid-base homeostasis are discussed.
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WormBook,
2006]
Form follows function, and this maxim is particularly true for the nematode sperm cell. Motility is essential for fertilization, and the process of spermatogenesis culminates in the production of a crawling spermatozoon with an extended pseudopod. However, the morphological similarity to amoeboid cells of other organisms is not conserved at the molecular level. Instead of utilizing the actin cytoskeleton and motor proteins, the pseudopod moves via the regulated assembly and disassembly of filaments composed of the major sperm protein (MSP). The current work reviews the structure and dynamics of MSP filament formation, the critical role of pH in MSP assembly, and the recent identification of components that regulate this process. The combination of cytological, biochemical, and genetic approaches in this relatively simple system make nematode sperm an attractive model for investigating the mechanics of amoeboid cell motility.
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Environ Pollut,
2013]
To improve risk estimates at the screening stage of Ecological Risk Assessment (ERA), short duration bioassays tailored to undisturbed soil cores from the contaminated site could be useful. However, existing standardized bioassays use disturbed soil samples and often pH sensitive organisms. This is a problem as naturally acidic soils are widespread. Changing soil properties to suit the test organism may change metal bioavailability, leading to erroneous risk estimates. For bioassays in undisturbed soil cores to be effective, species able to withstand natural soil properties must be identified. This review presents a critical examination of bioassay species' tolerance of acidic soils and sensitivity to metal contaminants such as Pb and Zn. Promising organisms include; Dendrobaena octaedra, Folsomia candida, Caenorhabditis elegans, Oppia nitens, Brassica rapa, Trifolium pratense, Allium cepa, Quercus rubra and Acer rubrum. The MetSTICK test and the Bait lamina test were also identified as suitable microorganism tests.
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J Bioenerg Biomembr,
2005]
The V-ATPases are ATP-dependent proton pumps present in both intracellular compartments and the plasma membrane. They function in such processes as membrane traffic, protein degradation, renal acidification, bone resorption and tumor metastasis. The V-ATPases are composed of a peripheral V(1) domain responsible for ATP hydrolysis and an integral V(0) domain that carries out proton transport. Our recent work has focused on structural analysis of the V-ATPase complex using both cysteine-mediated cross-linking and electron microscopy. For cross-linking studies, unique cysteine residues were introduced into structurally defined sites within the B and C subunits and used as points of attachment for the photoactivated cross-linking reagent MBP. Disulfide mediated cross-linking has also been used to define helical contact surfaces between subunits within the integral V(0) domain. With respect to regulation of V-ATPase activity, we have investigated the role that intracellular environment, luminal pH and a unique domain of the catalytic A subunit play in controlling reversible dissociation in vivo.