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Intracellular Ca2+ Signalling (intracellular + ca2+_signalling)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Roles of the actin-binding proteins in intracellular Ca2+ signalling

ACTA PHYSIOLOGICA, Issue 1 2009
J. T. Chun
Abstract Starfish oocytes undergo massive intracellular Ca2+ signalling during meiotic maturation and fertilization. Although the igniting stimulus of Ca2+ mobilization may differ in different cell contexts, its final leverage is usually the Ca2+ -releasing second messengers such as InsP3, cADPr and NAADP. The general scheme of intracellular Ca2+ release is that the corresponding receptors for these molecules serve as ion channels to release free Ca2+ from its internal stores such as the lumen of the endoplasmic reticulum. However, a growing body of evidence has suggested that intracellular Ca2+ release can be strongly modulated by the actin cytoskeleton. Although it is known that Ca2+ contributes to remodelling of the actin cytoskeleton, whether the actin cytoskeleton modulates Ca2+ signalling in return has not been much explored. An emerging candidate to answer to this reciprocal causality of Ca2+ and the actin cytoskeleton may be actin-binding proteins. In this review, we discuss how the actin cytoskeleton may fit into the known mechanisms of intracellular Ca2+ release, and propose two models to explain the experimental data. [source]

The patterns of spontaneous Ca2+ signals generated by ventral spinal neurons in vitro show time-dependent refinement

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
Sara Sibilla
Abstract Embryonic spinal neurons maintained in organotypic slice culture are known to mimic certain maturation-dependent signalling changes. With such a model we investigated, in embryonic mouse spinal segments, the age-dependent spatio-temporal control of intracellular Ca2+ signalling generated by neuronal populations in ventral circuits and its relation with electrical activity. We used Ca2+ imaging to monitor areas located within the ventral spinal horn at 1 and 2 weeks of in vitro growth. Primitive patterns of spontaneous neuronal Ca2+ transients (detected at 1 week) were typically synchronous. Remarkably, such transients originated from widespread propagating waves that became organized into large-scale rhythmic bursts. These activities were associated with the generation of synaptically mediated inward currents under whole-cell patch-clamp. Such patterns disappeared during longer culture of spinal segments: at 2 weeks in culture, only a subset of ventral neurons displayed spontaneous, asynchronous and repetitive Ca2+ oscillations dissociated from background synaptic activity. We observed that the emergence of oscillations was a restricted phenomenon arising together with the transformation of ventral network electrophysiological bursting into asynchronous synaptic discharges. This change was accompanied by the appearance of discrete calbindin immunoreactivity against an unchanged background of calretinin-positive cells. It is attractive to assume that periodic oscillations of Ca2+ confer a summative ability to these cells to shape the plasticity of local circuits through different changes (phasic or tonic) in intracellular Ca2+. [source]

Expression, purification, crystallization and preliminary X-ray analysis of calmodulin in complex with the regulatory domain of the plasma-membrane Ca2+ -ATPase ACA8

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010
Henning Tidow
Plasma-membrane Ca2+ -ATPases (PMCAs) are calcium pumps that expel Ca2+ from eukaryotic cells to maintain overall Ca2+ homoeostasis and to provide local control of intracellular Ca2+ signalling. They are of major physiological importance, with different isoforms being essential, for example, for presynaptic and postsynaptic Ca2+ regulation in neurons, feedback signalling in the heart and sperm motility. In the resting state, PMCAs are autoinhibited by binding of their C-terminal (in mammals) or N-terminal (in plants) tail to two major intracellular loops. Activation requires the binding of calcium-bound calmodulin (Ca2+ -CaM) to this tail and a conformational change that displaces the autoinhibitory tail from the catalytic domain. The complex between calmodulin and the regulatory domain of the plasma-membrane Ca2+ -ATPase ACA8 from Arabidopsis thaliana has been crystallized. The crystals belonged to space group C2, with unit-cell parameters a = 176.8, b = 70.0, c = 69.8,Å, , = 113.2°. A complete data set was collected to 3.0,Å resolution and structure determination is in progress in order to elucidate the mechanism of PMCA activation by calmodulin. [source]

Tonic Potentiation And Attenuation Produced By Membrane Depolarization In Guinea-Pig Trachealis

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2000
Kenichi Yamaki
SUMMARY 1. We studied how membrane depolarization directly affected intracellular Ca2+ signalling when voltage-operated Ca2+ channels (VOCC) were not available in guinea-pig tracheal smooth muscle. To block VOCC, we used 3 ,mol/L verapamil, which completely abolished high K+ (20,60 mmol/L)-induced contraction, and elevation of fura-2 signal. 2. Muscle tone was generated by adding Ca2+ to the extracellular Ca2+ -free solution containing prostaglandin (PG)E2 (100 nmol/L) after abolishing basal tone with indomethacin (1 ,mol/L). 3. In the absence of verapamil, high K+ (20,60 mmol/L) solution potentiated 2.4 mmol/L Ca2+ -induced sustained contractions. Even in the presence of 3 ,mol/L verapamil, replacement with 20 and 40 mmol/L K+ solution induced tonic potentiation, which was changed to attenuation with a higher K+ solution (60 mmol/L), lower extracellular Ca2+ concentration ([Ca2+]o) and pretreatment with cyclopiazonic acid (10 ,mol/L), a Ca2+ sequestration inhibitor. 4. These results indicate that the balance between depolarization-dependent Ca2+ release and receptor-operated cation channel inhibition may determine whether tonic potentiation or attenuation is manifested, depending on the availability of VOCC, the magnitude of the depolarization, [Ca2+]o and Ca2+ content in the sarcoplasmic reticulum. [source]