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Membrane Ca2+ Channels (membrane + ca2+_channel)

Distribution by Scientific Domains
Life Sciences75%

Kinds of Membrane Ca2+ Channels

  • plasma membrane ca2+ channel
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    Selected Abstracts

    Modulation of calcium signalling by intracellular organelles seen with targeted aequorins

    ACTA PHYSIOLOGICA, Issue 1 2009
    M. T. Alonso
    Abstract The cytosolic Ca2+ signals that trigger cell responses occur either as localized domains of high Ca2+ concentration or as propagating Ca2+ waves. Cytoplasmic organelles, taking up or releasing Ca2+ to the cytosol, shape the cytosolic signals. On the other hand, Ca2+ concentration inside organelles is also important in physiology and pathophysiology. Comprehensive study of these matters requires to measure [Ca2+] inside organelles and at the relevant cytosolic domains. Aequorins, the best-known chemiluminescent Ca2+ probes, are excellent for this end as they do not require stressing illumination, have a large dynamic range and a sharp Ca2+ -dependence, can be targeted to the appropriate location and engineered to have the proper Ca2+ affinity. Using this methodology, we have evidenced the existence in chromaffin cells of functional units composed by three closely interrelated elements: (1) plasma membrane Ca2+ channels, (2) subplasmalemmal endoplasmic reticulum and (3) mitochondria. These Ca2+ -signalling triads optimize Ca2+ microdomains for secretion and prevent propagation of the Ca2+ wave towards the cell core. Oscillatory cytosolic Ca2+ signals originate also oscillations of mitochondrial Ca2+ in several cell types. The nuclear envelope slows down the propagation of the Ca2+ wave to the nucleus and filters high frequencies. On the other hand, inositol-trisphosphate may produce direct release of Ca2+ to the nucleoplasm in GH3 pituitary cells, thus providing mechanisms for selective nuclear signalling. Aequorins emitting at different wavelengths, prepared by fusion either with green or red fluorescent protein, permit simultaneous and independent monitorization of the Ca2+ signals in different subcellular domains within the same cell. [source]

    Homocysteine enhances cardiac neural crest cell attachment in vitro by increasing intracellular calcium levels

    DEVELOPMENTAL DYNAMICS, Issue 8 2008
    David J. Heidenreich
    Abstract Elevated homocysteine (Hcys) increases the risk of neurocristopathies. Previous studies show Hcys inhibits neural crest (NC) cell migration in vivo. However, the mechanisms responsible for this effect are unknown. Here, we evaluated the effect of Hcys on NC cell attachment in vitro and determined if any of the effects were due to altered Ca2+ signaling. We found Hcys enhanced NC cell attachment in a dose and substrate-dependent manner. Ionomycin mimicked the effect of Hcys while BAPTA-AM and 2-APB blocked the effect of Hcys on NC attachment. In contrast, inhibitors of plasma membrane Ca2+ channels had no effect on NC attachment. Hcys also increased the emission of the intracellular Ca2+ -sensitive probe, Fluo-4. These results show Hcys alters NC attachment by triggering an increase in intracellular Ca2+ possibly by generating inositol triphosphate. Hence, the teratogenic effect ascribed to Hcys may be due to perturbation of intracellular Ca2+ signaling. Developmental Dynamics 237:2117,2128, 2008. © 2008 Wiley-Liss, Inc. [source]

    Ca2+ microdomains near plasma membrane Ca2+ channels: impact on cell function

    THE JOURNAL OF PHYSIOLOGY, Issue 13 2008
    Anant B. Parekh
    In eukaryotic cells, a rise in cytoplasmic Ca2+ can activate a plethora of responses that operate on time scales ranging from milliseconds to days. Inherent to the use of a promiscuous signal like Ca2+ is the problem of specificity: how can Ca2+ activate some responses but not others? We now know that the spatial profile of the Ca2+ signal is important Ca2+ does not simply rise uniformly throughout the cytoplasm upon stimulation but can reach very high levels locally, creating spatial gradients. The most fundamental local Ca2+ signal is the Ca2+ microdomain that develops rapidly near open plasmalemmal Ca2+ channels like voltage-gated L-type (Cav1.2) and store-operated CRAC channels. Recent work has revealed that Ca2+ microdomains arising from these channels are remarkably versatile in triggering a range of responses that differ enormously in both temporal and spatial profile. Here, I delineate basic features of Ca2+ microdomains and then describe how these highly local signals are used by Ca2+ -permeable channels to drive cellular responses. [source]

    Different Ca2+ signalling cascades manifested by mastoparan in the prothoracic glands of the tobacco hornworm, Manduca sexta, and the silkworm, Bombyx mori

    ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2007
    Skarlatos G. Dedos
    Abstract Application of the tetradecapeptide mastoparan to the prothoracic glands (PGs) of the tobacco hornworm, Manduca sexta, and the silkworm, Bombyx mori, resulted in increases in intracellular Ca2+ ([Ca2+]i). In M. sexta, Gi proteins are involved in the mastoparan-stimulated increase in [Ca2+]i. However, there is no involvement of Gi proteins in the mastoparan-stimulated increase in [Ca2+]i in prothoracic gland cells from B. mori. Unlike in M. sexta prothoracic glands, in B. mori prothoracic glands mastoparan increases [Ca2+]i even in the absence of extracellular Ca2+. Pharmacological manipulation of the Ca2+ signalling cascades in the prothoracic glands of both insect species suggests that in M. sexta prothoracic glands, mastoparan's first site of action is influx of Ca2+ through plasma membrane Ca2+ channels while in B. mori prothoracic glands, mastoparan's first site of action is mobilization of Ca2+ from intracellular stores. In M. sexta, the combined results indicate the presence of mastoparan-sensitive plasma membrane Ca2+ channels, distinct from those activated by prothoracicotropic hormone or the IP3 signalling cascade, that coordinate spatial increases in [Ca2+]i in prothoracic gland cells. We propose that in B. mori, mastoparan stimulates Ca2+ mobilization from ryanodine-sensitive intracellular Ca2+ stores in prothoracic gland cells. Arch. Insect Biochem. Physiol. 65:52,64, 2007. © 2007 Wiley-Liss, Inc. [source]