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Ca2+ Regulation (ca2+ + regulation)
Selected AbstractsEffects of Antrodia camphorata on viability, apoptosis, [Ca2+]i, and MAPKs phosphorylation in MG63 human osteosarcoma cellsDRUG DEVELOPMENT RESEARCH, Issue 2 2007Yih-Chau Lu Abstract The present study explored the effect of Antrodia camphorata (AC) on viability, apoptosis, mitogen-activated protein kinases (MAPKs) phosphorylation, and Ca2+ regulation in MG63 human osteosarcoma cells. AC (25,50,µg/ml) did not affect cell viability, but at 100,200,µg/ml decreased viability and induced apoptosis in a concentration-dependent manner. AC at concentrations of 25,200,µg/ml did not alter basal [Ca2+]i, but at 25,µg/ml decreased [Ca2+]i increases induced by ATP, bradykinin, histamine, and thapsigargin. ATP, bradykinin, and histamine increased cell viability while thapsigargin decreased it. AC (25,µg/ml) pretreatment failed to alter bradykinin- and thapsigargin-induced effects on viability, but potentiated ATP- and histamine-induced increases in viability. Immunoblotting showed that MG63 cells did not have background phospho-JNK and phospho-p38 mitogen-activated protein kinases (MAPKs); and AC did not induce the phosphorylation of these two MAPKs. Conversely, the cells had significant background phospho-ERK MAPK that was inhibited by 200,µg/ml AC. The ERK-specific inhibitor PD98059 also induced cell death. Collectively, in MG63 cells, AC exerted multiple effects on viability and [Ca2+]i, caused apoptosis probably via inhibition of ERK MAPK phosphorylation. Drug Dev Res 68:71,78, 2007. © 2007 Wiley-Liss, Inc. [source] Cell shrinkage evoked by Ca2+ -free solution in rat alveolar type II cells: Ca2+ regulation of Na+,H+ exchangeEXPERIMENTAL PHYSIOLOGY, Issue 2 2005Hitoshi Murao The effects of intracellular Ca2+ concentration, [Ca2+]i, on the volume of rat alveolar type II cells (AT-II cells) were examined. Perfusion with a Ca2+ -free solution induced shrinkage of the AT-II cell volume in the absence or presence of amiloride (1 ,m, an inhibitor of Na+ channels); however, it did not in the presence of 5-(N -methyl- N -isobutyl)-amiloride (MIA, an inhibitor of Na+,H+ exchange). MIA decreased the volume of AT-II cells. Inhibitors of Cl,,HCO3, exchange, 4,4,-diisothiocyanostilbene-2,2,-disulfonic acid (DIDS) and 4-acetamido-4,-isothiocyanatostilbene-2,2,-disulfonic acid (SITS) also decreased the volume of AT-II cells. This indicates that the cell shrinkage induced by a Ca2+ -free solution is caused by a decrease in NaCl influx via Na+,H+ exchange and Cl,,HCO3, exchange. Addition of ionomycin (1 ,m), in contrast, induced cell swelling when AT-II cells were pretreated with quinine and amiloride. This swelling of the AT-II cells is not detected in the presence of MIA. Intracellular pH (pHi) measurements demonstrated that the Ca2+ -free solution or MIA decreases pHi, and that ionomycin increases it. Ionomycin stimulated the pHi recovery after an acid loading (NH4+ pulse method), which was not noted in MIA-treated AT-II cells. Ionomycin increased [Ca2+]i in fura-2-loaded AT-II cells. In conclusion, the Na+,H+ exchange activities of AT-II cells, which maintain the volume and pHi, are regulated by [Ca2+]i. [source] Mechanism of the persistent sodium current activator veratridine-evoked Ca2+ elevation: implication for epilepsyJOURNAL OF NEUROCHEMISTRY, Issue 3 2009Ádám Fekete Abstract Although the role of Na+ in several aspects of Ca2+ regulation has already been shown, the exact mechanism of intracellular Ca2+ concentration ([Ca2+]i) increase resulting from an enhancement in the persistent, non-inactivating Na+ current (INa,P), a decisive factor in certain forms of epilepsy, has yet to be resolved. Persistent Na+ current, evoked by veratridine, induced bursts of action potentials and sustained membrane depolarization with monophasic intracellular Na+ concentration ([Na+]i) and biphasic [Ca2+]i increase in CA1 pyramidal cells in acute hippocampal slices. The Ca2+ response was tetrodotoxin- and extracellular Ca2+ -dependent and ionotropic glutamate receptor-independent. The first phase of [Ca2+]i rise was the net result of Ca2+ influx through voltage-gated Ca2+ channels and mitochondrial Ca2+ sequestration. The robust second phase in addition involved reverse operation of the Na+,Ca2+ exchanger and mitochondrial Ca2+ release. We excluded contribution of the endoplasmic reticulum. These results demonstrate a complex interaction between persistent, non-inactivating Na+ current and [Ca2+]i regulation in CA1 pyramidal cells. The described cellular mechanisms are most likely part of the pathomechanism of certain forms of epilepsy that are associated with INa,P. Describing the magnitude, temporal pattern and sources of Ca2+ increase induced by INa,P may provide novel targets for antiepileptic drug therapy. [source] Different effects of cardiac versus skeletal muscle regulatory proteins on in vitro measures of actin filament speed and forceTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Emilie Warner Clemmens Mammalian cardiac and skeletal muscle express unique isoforms of the thin filament regulatory proteins, troponin (Tn) and tropomyosin (Tm), and the significance of these different isoforms in thin filament regulation has not been clearly identified. Both in vitro and skinned cellular studies investigating the mechanism of thin filament regulation in striated muscle have often used heterogeneous mixtures of Tn, Tm and myosin isoforms, and variability in reported results might be explained by different combinations of these proteins. Here we used in vitro motility and force (microneedle) assays to investigate the influence of cardiac versus skeletal Tn and Tm isoforms on actin,heavy meromyosin (HMM) mechanics. When interacting with skeletal HMM, thin filaments reconstituted with cardiac Tn/Tm or skeletal Tn/Tm exhibited similar speed,calcium relationships and significantly increased maximum speed and force per filament length (F/l) at pCa 5 (versus unregulated actin filaments). However, augmentation of F/l was greater with skeletal regulatory proteins. Reconstitution of thin filaments with the heterogeneous combination of skeletal Tn and cardiac Tm decreased sliding speeds at all [Ca2+] relative to thin filaments with skeletal Tn/Tm. Finally, for filaments reconstituted with any heterogeneous mix of Tn and Tm isoforms, force was not potentiated over that of unregulated actin filaments. Combined the results suggest (1) that cardiac regulatory proteins limit the allosteric enhancement of force, and (2) that Tn and Tm isoform homogeneity is important when studying Ca2+ regulation of crossbridge binding and kinetics as well as mechanistic differences between cardiac and skeletal muscle. [source] Expression, purification, crystallization and preliminary X-ray analysis of calmodulin in complex with the regulatory domain of the plasma-membrane Ca2+ -ATPase ACA8ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010Henning 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] | ||||||||||