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  • 1
    Online Resource
    Online Resource
    β 2 -Adrenergic Receptor Redistribution in Heart Failure Changes cAMP Compartmentation
    American Association for the Advancement of Science (AAAS) ; 2010
    In:  Science Vol. 327, No. 5973 ( 2010-03-26), p. 1653-1657
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 327, No. 5973 ( 2010-03-26), p. 1653-1657
    Abstract: The β 1 - and β 2 -adrenergic receptors (βARs) on the surface of cardiomyocytes mediate distinct effects on cardiac function and the development of heart failure by regulating production of the second messenger cyclic adenosine monophosphate (cAMP). The spatial localization in cardiomyocytes of these βARs, which are coupled to heterotrimeric guanine nucleotide–binding proteins (G proteins), and the functional implications of their localization have been unclear. We combined nanoscale live-cell scanning ion conductance and fluorescence resonance energy transfer microscopy techniques and found that, in cardiomyocytes from healthy adult rats and mice, spatially confined β 2 AR-induced cAMP signals are localized exclusively to the deep transverse tubules, whereas functional β 1 ARs are distributed across the entire cell surface. In cardiomyocytes derived from a rat model of chronic heart failure, β 2 ARs were redistributed from the transverse tubules to the cell crest, which led to diffuse receptor-mediated cAMP signaling. Thus, the redistribution of β 2 ARs in heart failure changes compartmentation of cAMP and might contribute to the failing myocardial phenotype.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1185988
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2010
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  • 2
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    Online Resource
    Esmolol is antiarrhythmic in doxorubicin‐induced arrhythmia in cultured cardiomyocytes – determination by novel rapid cardiomyocyte assay
    Wiley ; 2003
    In:  FEBS Letters Vol. 548, No. 1-3 ( 2003-07-31), p. 74-78
    Details
    In: FEBS Letters, Wiley, Vol. 548, No. 1-3 ( 2003-07-31), p. 74-78
    Abstract: Cardiac toxicity is an uncommon but potentially serious complication of cancer therapy, especially with anthracyclines. One of the most effective anticancer drugs is doxorubicin, but its value is limited by the risk of developing cardiomyopathy and ventricular arrhythmia. When applied to a network of periodically contracting cardiomyocytes in culture, doxorubicin induces rhythm disturbances. Using a novel rapid assay based on non‐invasive ion‐conductance microscopy we show that the β‐antagonist esmolol can restore rhythm in doxorubicin‐treated cultures of cardiomyocytes. Moreover, esmolol pre‐treatment can protect the culture from doxorubicin‐induced arrhythmia.
    Type of Medium: Online Resource
    ISSN: 0014-5793 , 1873-3468
    URL: Article
    DOI: 10.1016/S0014-5793(03)00743-9
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2003
    detail.hit.zdb_id: 1460391-3
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  • 3
    Online Resource
    Online Resource
    Endocytic pathways: combined scanning ion conductance and surface confocal microscopy study
    Springer Science and Business Media LLC ; 2008
    In:  Pflügers Archiv - European Journal of Physiology Vol. 456, No. 1 ( 2008-4), p. 227-235
    Details
    In: Pflügers Archiv - European Journal of Physiology, Springer Science and Business Media LLC, Vol. 456, No. 1 ( 2008-4), p. 227-235
    Type of Medium: Online Resource
    ISSN: 0031-6768 , 1432-2013
    URL: Article
    DOI: 10.1007/s00424-007-0410-4
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2008
    detail.hit.zdb_id: 1463014-X
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  • 4
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    A conserved tryptophan in pneumolysin is a determinant of the characteristics of channels formed by pneumolysin in cells and planar lipid bilayers
    Portland Press Ltd. ; 1998
    In:  Biochemical Journal Vol. 329, No. 3 ( 1998-02-01), p. 571-577
    Details
    In: Biochemical Journal, Portland Press Ltd., Vol. 329, No. 3 ( 1998-02-01), p. 571-577
    Abstract: Pneumolysin is one of the family of thiol-activatable, cytolytic toxins. Within these toxins the amino acid sequence Trp-Glu-Trp-Trp is conserved. Mutations made in this region of pneumolysin, residues 433-436 inclusive, did not affect cell binding or the formation of toxin oligomers in the target cell membrane. However, the mutations did affect haemolysis, leakage of low-molecular-mass metabolites from Lettre cells and the induction of conductance channels across planar lipid bilayers. Of eight modified pneumolysins examined, Trp-433 → Phe showed the smallest amount of haemolysis or leakage (less than 5% of wild type). Pneumolysin-induced leakage from Lettre cells was sensitive to inhibition by bivalent cations but the extent of inhibition varied depending on the modification. Leakage by the mutant Trp-433 → Phe was least sensitive to cation inhibition. The ion-conducting channels formed across planar lipid bilayers exhibit small (less than 30 pS), medium (30 pS-1 nS) and large (more than 1 nS) conductance steps. Small- and medium-sized channels were preferentially closed by bivalent cations. In contrast with wild-type toxin, which formed predominantly small channels, the modified toxin Trp-433 → Phe formed large channels that were insensitive to cation-induced closure. Polysaccharides of molecular mass more than 15 kDa inhibited haemolysis by wild-type toxin, but polysaccharide of up to 40 kDa did not prevent haemolysis by Trp-433 → Phe. Electron microscopy revealed that Trp-433 → Phe formed oligomeric arc and ring structures with dimensions identical with those of wild-type toxin, and that the ratio of arcs to rings formed was the same for wild-type toxin and the Trp-433 → Phe variant. We conclude that the change Trp-433 → Phe affects channel formation at a point subsequent to binding to the cell membrane and the formation of oligomers, and that the size of arc and ring structures revealed by electron microscopy does not reflect the functional state of the channels.
    Type of Medium: Online Resource
    ISSN: 0264-6021 , 1470-8728
    URL: Article
    DOI: 10.1042/bj3290571
    RVK:
    WA 15000
    Language: English
    Publisher: Portland Press Ltd.
    Publication Date: 1998
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  • 5
    Online Resource
    Online Resource
    Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy
    Proceedings of the National Academy of Sciences ; 2012
    In:  Proceedings of the National Academy of Sciences Vol. 109, No. 29 ( 2012-07-17), p. 11540-11545
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 109, No. 29 ( 2012-07-17), p. 11540-11545
    Abstract: We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5–100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5–3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1203570109
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2012
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    detail.hit.zdb_id: 1461794-8
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  • 6
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    Loss of T-tubules and other changes to surface topography in ventricular myocytes from failing human and rat heart
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 16 ( 2009-04-21), p. 6854-6859
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 16 ( 2009-04-21), p. 6854-6859
    Abstract: T-tubular invaginations of the sarcolemma of ventricular cardiomyocytes contain junctional structures functionally coupling L-type calcium channels to the sarcoplasmic reticulum calcium-release channels (the ryanodine receptors), and therefore their configuration controls the gain of calcium-induced calcium release (CICR). Studies primarily in rodent myocardium have shown the importance of T-tubular structures for calcium transient kinetics and have linked T-tubule disruption to delayed CICR. However, there is disagreement as to the nature of T-tubule changes in human heart failure. We studied isolated ventricular myocytes from patients with ischemic heart disease, idiopathic dilated cardiomyopathy, and hypertrophic obstructive cardiomyopathy and determined T-tubule structure with either the fluorescent membrane dye di-8-ANNEPs or the scanning ion conductance microscope (SICM). The SICM uses a scanning pipette to produce a topographic representation of the surface of the live cell by a non-optical method. We have also compared ventricular myocytes from a rat model of chronic heart failure after myocardial infarction. T-tubule loss, shown by both ANNEPs staining and SICM imaging, was pronounced in human myocytes from all etiologies of disease. SICM imaging showed additional changes in surface structure, with flattening and loss of Z-groove definition common to all etiologies. Rat myocytes from the chronic heart failure model also showed both T-tubule and Z-groove loss, as well as increased spark frequency and greater spark amplitude. This study confirms the loss of T-tubules as part of the phenotypic change in the failing human myocyte, but it also shows that this is part of a wider spectrum of alterations in surface morphology.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0809777106
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
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    detail.hit.zdb_id: 1461794-8
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  • 7
    Online Resource
    Online Resource
    Imaging the cell surface and its organization down to the level of single molecules
    The Royal Society ; 2013
    In:  Philosophical Transactions of the Royal Society B: Biological Sciences Vol. 368, No. 1611 ( 2013-02-05), p. 20120027-
    Details
    In: Philosophical Transactions of the Royal Society B: Biological Sciences, The Royal Society, Vol. 368, No. 1611 ( 2013-02-05), p. 20120027-
    Abstract: Determining the organization of key molecules on the surface of live cells in two dimensions and how this changes during biological processes, such as signalling, is a major challenge in cell biology and requires methods with nanoscale spatial resolution and high temporal resolution. Here, we review biophysical tools, based on scanning ion conductance microscopy and single-molecule fluorescence and the combination of both of these methods, which have recently been developed to address these issues. We then give examples of how these methods have been be applied to provide new insights into cell membrane organization and function, and discuss some of the issues that will need to be addressed to further exploit these methods in the future.
    Type of Medium: Online Resource
    ISSN: 0962-8436 , 1471-2970
    URL: Article
    DOI: 10.1098/rstb.2012.0027
    RVK:
    WA 15000
    Language: English
    Publisher: The Royal Society
    Publication Date: 2013
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  • 8
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    Epidermal growth factor stimulates translocation of the class II phosphoinositide 3-kinase PI3K-C2β to the nucleus
    Portland Press Ltd. ; 2009
    In:  Biochemical Journal Vol. 422, No. 1 ( 2009-08-15), p. 53-60
    Details
    In: Biochemical Journal, Portland Press Ltd., Vol. 422, No. 1 ( 2009-08-15), p. 53-60
    Abstract: Although the class II phosphoinositide 3-kinase enzymes PI3K-C2α and PI3K-C2β act acutely downstream of cell surface receptors they have also been localized to nuclei in mammalian cells. As with the class I PI3K enzymes, the relationship between the pools of enzyme present in cytoplasm and nuclei remains poorly understood. In this study we test the hypothesis that PI3K-C2β translocates to nuclei in response to growth factor stimulation. Fractionating homogenates of quiescent cells revealed that less than 5% of total PI3K-C2β resides in nuclei. Stimulation with epidermal growth factor sequentially increased levels of this enzyme, firstly in the cytosol and secondly in the nuclei. Using detergent-treated nuclei, we showed that PI3K-C2β co-localized with lamin A/C in the nuclear matrix. This was confirmed biochemically, and a phosphoinositide kinase assay showed a statistically significant increase in nuclear PI3K-C2β levels and lipid kinase activity following epidermal growth factor stimulation. C-terminal deletion and point mutations of PI3K-C2β demonstrated that epidermal growth factor-driven translocation to the nucleus is dependent on a sequence of basic amino acid residues (KxKxK) that form a nuclear localization motif within the C-terminal C2 domain. Furthermore, when this sequence was expressed as an EGFP (enhanced green fluorescent protein) fusion protein, it translocated fluorescence into nuclei with an efficiency dependent upon copy number. These data demonstrate that epidermal growth factor stimulates the appearance of PI3K-C2β in nuclei. Further, this effect is dependent on a nuclear localization signal present within the C-terminal C2 domain, indicating its bimodal function regulating phospholipid binding and shuttling PI3K-C2β into the nucleus.
    Type of Medium: Online Resource
    ISSN: 0264-6021 , 1470-8728
    URL: Article
    DOI: 10.1042/BJ20090654
    RVK:
    WA 15000
    Language: English
    Publisher: Portland Press Ltd.
    Publication Date: 2009
    detail.hit.zdb_id: 1473095-9
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  • 9
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    Aldosterone acts via an ATP autocrine/paracrine system: The Edelman ATP hypothesis revisited
    Proceedings of the National Academy of Sciences ; 2005
    In:  Proceedings of the National Academy of Sciences Vol. 102, No. 42 ( 2005-10-18), p. 15000-15005
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 102, No. 42 ( 2005-10-18), p. 15000-15005
    Abstract: Aldosterone, the most important sodium-retaining hormone, was first characterized 〉 50 years ago. However, despite numerous studies including the classical work of Isidore S. “Izzy” Edelman showing that aldosterone action depended on ATP production, the mechanism by which it activates sodium reabsorption via the epithelial sodium channel remains unclear. Here, we report experiments that suggest that one of the key steps in aldosterone action is via an autocrine/paracrine system. The hormone stimulates ATP release from the basolateral side of the target kidney cell. Prevention of ATP accumulation or its removal blocks aldosterone action. ATP then acts via a purinergic mechanism to produce contraction of small groups of adjacent epithelial cells. Patch clamping demonstrates that it is these contracted cells that have channel activity. With progressive recruitment of contracting cells, there is then a parallel increase in transepithelial electrical conductance. In common with other stimuli of sodium transport, this pathway involves phosphatidylinositol 3-kinase. Inhibition of phosphatidylinositol 3-kinase blocks both cell contraction and conductance. We put forward the hypothesis that redistribution of the cell volume caused by the lateral contraction results in apical swelling and that this change, in turn, disrupts the epithelial sodium channel interaction with the F-actin cytoskeleton, opening the channel and hence increasing sodium transport.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0507008102
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2005
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 10
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    An alternative mechanism of clathrin-coated pit closure revealed by ion conductance microscopy
    Rockefeller University Press ; 2012
    In:  Journal of Cell Biology Vol. 197, No. 4 ( 2012-05-14), p. 499-508
    Details
    In: Journal of Cell Biology, Rockefeller University Press, Vol. 197, No. 4 ( 2012-05-14), p. 499-508
    Abstract: Current knowledge of the structural changes taking place during clathrin-mediated endocytosis is largely based on electron microscopy images of fixed preparations and x-ray crystallography data of purified proteins. In this paper, we describe a study of clathrin-coated pit dynamics in living cells using ion conductance microscopy to directly image the changes in pit shape, combined with simultaneous confocal microscopy to follow molecule-specific fluorescence. We find that 70% of pits closed with the formation of a protrusion that grew on one side of the pit, covered the entire pit, and then disappeared together with pit-associated clathrin–enhanced green fluorescent protein (EGFP) and actin-binding protein–EGFP (Abp1-EGFP) fluorescence. This was in contrast to conventionally closing pits that closed and cleaved from flat membrane sheets and lacked accompanying Abp1-EGFP fluorescence. Scission of both types of pits was found to be dynamin-2 dependent. This technique now enables direct spatial and temporal correlation between functional molecule-specific fluorescence and structural information to follow key biological processes at cell surfaces.
    Type of Medium: Online Resource
    ISSN: 1540-8140 , 0021-9525
    URL: Article
    DOI: 10.1083/jcb.201109130
    RVK:
    WA 15000
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 2012
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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