38 research outputs found
Recent advances in understanding the extracellular calcium-sensing receptor
No full textThe extracellular calcium-sensing receptor (CaR), a ubiquitous class C G-protein-coupled receptor (GPCR), is responsible for the control of calcium homeostasis in body fluids. It integrates information about external Ca and a surfeit of other endogenous ligands into multiple intracellular signals, but how is this achieved? This review will focus on some of the exciting concepts in CaR signaling and pharmacology that have emerged in the last few years
The inner and outer compartments of mitochondria are sites of distinct cAMP/PKA signaling dynamics
No full textCyclic AMP (cAMP)-dependent phosphorylation has been reported to exert biological effects in both the mitochondrial matrix and outer mitochondrial membrane (OMM). However, the kinetics, targets, and effectors of the cAMP cascade in these organellar domains remain largely undefined. Here we used sensitive FRET-based sensors to monitor cAMP and protein kinase A (PKA) activity in different mitochondrial compartments in real time. We found that cytosolic cAMP did not enter the matrix, except during mitochondrial permeability transition. Bicarbonate treatment (expected to activate matrix-bound soluble adenylyl cyclase) increased intramitochondrial cAMP, but along with membrane-permeant cAMP analogues, failed to induce measureable matrix PKA activity. In contrast, the OMM proved to be a domain of exceptionally persistent cAMP-dependent PKA activity. Although cAMP signaling events measured on the OMM mirrored those of the cytosol, PKA phosphorylation at the OMM endured longer as a consequence of diminished control by local phosphatases. Our findings demonstrate that mitochondria host segregated cAMP cascades with distinct functional and kinetic signatures.Version of Recor
Coal as a source rock for hydrocarbon gas in the Aldebaran Sandstone, Denison Trough, Bowen Basin - geochemical evidence
No full textThe Early Permian Aldebaran Sandstone is the main hydrocarbon reservoir in the Denison Trough. Contained hydrocarbon gas has a wet gas index (C/C - C) of between 0.87 and 0.97 (N=10), and constituent methane has δC values ranging from -51.5 to -36.2‰ (N=10). These values clearly indicate that the gas is thermogenic rather than biogenic. The methane δC values are anomalously low, with typical values for humic methane present in natural gas formed at similar maturity levels significantly higher at -26 ± 5‰. This suggests that, in addition to disseminated organic matter in underlying marine mudrocks of the Cattle Creek Formation, methane substantially more depleted in C was derived from coal seams of the Reids Dome beds, a thick coal measure sequence which underlies the Cattle Creek Formation and, in the south, the Aldebaran Sandstone. The presence of co-existing, isotopically heavy CO in the Glentulloch and Merivale Fields is consistent with the view that natural gas in the Aldebaran Sandstone is in part coal seam derived. -from Author
“cAMP Sponge”: A Buffer for Cyclic Adenosine 3′, 5′-Monophosphate
No full textBackground: While intracellular buffers are widely used to study calcium signaling, no such tool exists for the other major second messenger, cyclic AMP (cAMP). Methods/Principal Findings: Here we describe a genetically encoded buffer for cAMP based on the high-affinity cAMP-binding carboxy-terminus of the regulatory subunit of protein kinase A (PKA). Addition of targeting sequences permitted localization of this fragment to the extra-nuclear compartment, while tagging with mCherry allowed quantification of its expression at the single cell level. This construct (named “cAMP sponge”) was shown to selectively bind cAMP in vitro. Its expression significantly suppressed agonist-induced cAMP signals and the downstream activation of PKA within the cytosol as measured by FRET-based sensors in single living cells. Point mutations in the cAMP-binding domains of the construct rendered the chimera unable to bind cAMP in vitro or in situ. Cyclic AMP sponge was fruitfully applied to examine feedback regulation of gap junction-mediated transfer of cAMP in epithelial cell couplets. Conclusions: This newest member of the cAMP toolbox has the potential to reveal unique biological functions of cAMP, including insight into the functional significance of compartmentalized signaling events.Version of Recor
] Changes in Agonist-Sensitive Internal Stores Using Compartmentalized Fluorescent Indicators
No full text] Changes in Agonist-Sensitive Internal Stores Using Compartmentalized Fluorescent Indicators
No full text
Recommended from our members
Quantitative Approaches to Cellular Information Processing and Metabolic Regulation
No full textOrganisms of all levels of complexity must undertake complex information processing tasks. Diverse cellular and biochemical mechanisms are required to integrate multiple sources of information and to balance performance trade-offs, such as between speed and accuracy or robustness and fragility. This dissertation describes a series of quantitative analyses of cellular information processing, with particular attention given to the regulation of metabolism. Chapters 2 and 3 consider mechanisms for achieving concentration robustness in signal transduction. Chapter 2 develops a large compendium of reaction networks involving bifunctional enzymes, which are often positioned at key metabolic branch points and are experimentally associated with robust control. Using high-throughput algebraic analysis of this compendium, we demonstrate that bifunctional enzymes can implement five different forms of concentration robustness, and that the type of robustness is highly sensitive to biochemical details beyond bifunctionality. Chapter 3 identifies intermediate buffering in a three-component phospho-relay as a novel mechanism for concentration robustness and argues that such a mechanism accounts for robust inactivation of the yeast osmotic stress response. Chapter 4 reports an integrated computational and experimental analysis of production of the oncometabolite 2-hydroxyglutarate by mutant isocitrate dehydrogenase 1 (IDH1), which suggests that the clinically observed retention of a wild-type (WT) IDH1 allele in tumors is not due to a requirement for substrate channeling or substantial inter-subunit flux in WT/mutant IDH1 heterodimers. In Chapter 5 we examine the information processing capabilities of calcium/calmodulin signaling and show that a straightforward equilibrium binding analysis can clarify longstanding questions about the control of smooth muscle contraction. Finally, Chapter 6 reports an experimental approach to investigate the limits of complex information processing in single cells. Resurrecting a classical body of literature on the behavior of unicellular organisms, we demonstrate that the giant ciliate Stentor roeseli engages in multi-step hierarchical sequences of avoidance behaviors. The S. roeseli avoidance response is distinct from other primitive forms of learning such as habituation and conditioning and is suggestive of complex decision-making by the organism. Throughout the dissertation, a common theme is the use of mathematical modeling to link biochemical form to physiological function and to generate experimentally testable predictions that are independent of hard-to-measure parameter values.Systems Biolog
