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Ca2+ Microdomains (ca2+ + microdomain)
Selected AbstractsCa2+ microdomains near plasma membrane Ca2+ channels: impact on cell functionTHE JOURNAL OF PHYSIOLOGY, Issue 13 2008Anant 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] Modulation of calcium signalling by intracellular organelles seen with targeted aequorinsACTA PHYSIOLOGICA, Issue 1 2009M. 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] Altered distribution of mitochondria impairs calcium homeostasis in rat hippocampal neurons in cultureJOURNAL OF NEUROCHEMISTRY, Issue 1 2003Guang Jian Wang Abstract The specificity of Ca2+ signals is conferred in part by limiting changes in cytosolic Ca2+ to subcellular domains. Mitochondria play a major role in regulating Ca2+ in neurons and may participate in its spatial localization. We examined the effects of changes in the distribution of mitochondria on NMDA-induced Ca2+ increases. Hippocampal cultures were treated with the microtubule-destabilizing agent vinblastine, which caused the mitochondria to aggregate and migrate towards one side of the neuron. This treatment did not appear to decrease the energy status of mitochondria, as indicated by a normal membrane potential and pH gradient across the inner membrane. Moreover, electron microscopy showed that vinblastine treatment altered the distribution but not the ultrastructure of mitochondria. NMDA (200 µm, 1 min) evoked a greater increase in cytosolic Ca2+ in vinblastine-treated cells than in untreated cells. This increase did not result from impaired Ca2+ efflux, enhanced Ca2+ influx, opening of the mitochondrial permeability transition pore or altered function of endoplasmic reticulum Ca2+ stores. Ca2+ uptake into mitochondria was reduced by 53% in vinblastine-treated cells, as reported by mitochondrially targeted aequorin. Thus, the distribution of mitochondria maintained by microtubules is critical for buffering Ca2+ influx. A subset of mitochondria close to a Ca2+ source may preferentially regulate Ca2+ microdomains, set the threshold for Ca2+ -induced toxicity and participate in local ATP production. [source] Ca2+ microdomains near plasma membrane Ca2+ channels: impact on cell functionTHE JOURNAL OF PHYSIOLOGY, Issue 13 2008Anant 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] | ||||||||||