Regulated exocytosis of GABA-containing synaptic-like microvesicles in pancreatic beta-cells.
AuthorsBraun M, Wendt A, Birnir B, Broman J, Eliasson L, Galvanovskis J, Gromada J, Mulder H, Rorsman P
JournalJ Gen Physiol
PubMed ID14769845
'We have explored whether gamma-aminobutyric acid (GABA) is released by regulated exocytosis of GABA-containing synaptic-like microvesicles (SLMVs) in insulin-releasing rat pancreatic beta-cells. To this end, beta-cells were engineered to express GABA(A)-receptor Cl(-)-channels at high density using adenoviral infection. Electron microscopy indicated that the average diameter of the SLMVs is 90 ... More
Presynaptic strontium dynamics and synaptic transmission.
AuthorsXu-Friedman MA, Regehr WG
JournalBiophys J
PubMed ID10096899
'Strontium can replace calcium in triggering neurotransmitter release, although peak release is reduced and the duration of release is prolonged. Strontium has therefore become useful in probing release, but its mechanism of action is not well understood. Here we study the action of strontium at the granule cell to Purkinje ... More
Ionic selectivity of low-affinity ratiometric calcium indicators: mag-Fura-2, Fura-2FF and BTC.
AuthorsHyrc KL, Bownik JM, Goldberg MP
JournalCell Calcium
PubMed ID10756974
'Accurate measurement of elevated intracellular calcium levels requires indicators with low calcium affinity and high selectivity. We examined fluorescence spectral properties and ionic specificity of three low-affinity, ratiometric indicators structurally related to Fura-2: mag-Fura-2 (furaptra), Fura-2FF, and BTC. The indicators differed in respect to their excitation wavelengths, affinity for Ca2+ ... More
Simultaneous detection of intracellular free calcium and zinc using fura-2FF and FluoZin-3.
AuthorsDevinney MJ, Reynolds IJ, Dineley KE
JournalCell Calcium
PubMed ID15670869
'Elevation of intracellular free zinc ([Zn2+]i) probably contributes to cell death in injury paradigms involving calcium deregulation and oxidative stress such as glutamate excitotoxicity. However, it is difficult to monitor both ions simultaneously in live cells. Here we present a new method using fluorescence microscopy and the ion sensitive indicators ... More
Identification of common binding sites for calmodulin and inositol 1,4,5-trisphosphate receptors on the carboxyl termini of trp channels.
AuthorsTang J, Lin Y, Zhang Z, Tikunova S, Birnbaumer L, Zhu MX
JournalJ Biol Chem
PubMed ID11290752
Homologues of Drosophila Trp (transient receptor potential) form plasma membrane channels that mediate Ca(2+) entry following the activation of phospholipase C by cell surface receptors. Among the seven Trp homologous found in mammals, Trp3 has been shown to interact with and respond to IP(3) receptors (IP(3)Rs) for activation. Here we ... More
Ca2+ regulation of gelsolin activity: binding and severing of F-actin.
AuthorsKinosian HJ, Newman J, Lincoln B, Selden LA, Gershman LC, Estes JE
JournalBiophys J
PubMed ID9826630
Regulation of the F-actin severing activity of gelsolin by Ca2+ has been investigated under physiologic ionic conditions. Tryptophan fluorescence intensity measurements indicate that gelsolin contains at least two Ca2+ binding sites with affinities of 2.5 x 10(7) M-1 and 1.5 x 10(5) M-1. At F-actin and gelsolin concentrations in the ... More
NMR-sensitive fluorinated and fluorescent intracellular calcium ion indicators with high dissociation constants.
AuthorsLondon RE, Rhee CK, Murphy E, Gabel S, Levy LA
JournalAm J Physiol
PubMed ID8203496
A new series of high-dissociation constant (KD) Ca2+ indicators has been developed to reduce perturbations due to buffering of transients, to carry out measurements in cells and organelles with high basal Ca2+ concentrations, and to measure cytosolic Ca2+ levels in the presence of perturbations that may significantly increase these levels. ... More
Tiron exerts effects unrelated to its role as a scavenger of superoxide anion: effects on calcium binding and vascular responses.
AuthorsGhosh M, Wang HD, McNeill JR
JournalCan J Physiol Pharmacol
PubMed ID12269784
The effect of tiron (4,5-dihydroxy-1,3-benzene disulfonic acid) on the binding of Ca2+ and its effect on vascular responses of the rat perfused mesenteric bed was studied at concentrations of tiron that are used widely to scavenge superoxide anion. In competition assays in buffered solutions with no tissue present, tiron decreased ... More
Basal and physiological Ca(2+) leak from the endoplasmic reticulum of pancreatic acinar cells. Second messenger-activated channels and translocons.
AuthorsLomax RB, Camello C, Van Coppenolle F, Petersen OH, Tepikin AV
JournalJ Biol Chem
PubMed ID11994289
We have studied the Ca(2+) leak pathways in the endoplasmic reticulum of pancreatic acinar cells by directly measuring Ca(2+) in the endoplasmic reticulum ([Ca(2+)](ER)). Cytosolic Ca(2+) ([Ca(2+)](C)) was clamped to the resting level by a BAPTA-Ca(2+) mixture. Administration of cholecystokinin within the physiological concentration range caused a graded decrease of ... More
Ca(2+)- and voltage-dependent gating of Ca(2+)- and ATP-sensitive cationic channels in brain capillary endothelium.
AuthorsCsanády L, Adam-Vizi V
JournalBiophys J
PubMed ID12829486
Biophysical properties of the Ca(2+)-activated nonselective cation channel expressed in brain capillaries were studied in inside-out patches from primary cultures of rat brain microvascular endothelial cells. At -40 mV membrane potential, open probability (P(o)) was activated by cytosolic [Ca(2+)] > 1 micro M and was half-maximal at approximately 20 micro ... More
Characterization of a range of fura dyes with two-photon excitation.
AuthorsWokosin DL, Loughrey CM, Smith GL
JournalBiophys J
PubMed ID14990500
Two-photon excitation (TPE) spectra of Fura-2, -4F, -6F, -FF, and Furaptra were characterized using a tunable (750-850 nM) ultra-short pulse laser. Two-photon fluorescence of these dyes was studied in free solution and in the cytosol of isolated rabbit ventricular cardiomyocytes. The TPE spectra of the Ca(2+)-free and Ca(2+)-bound forms of ... More
Mitochondria suppress local feedback activation of inositol 1,4, 5-trisphosphate receptors by Ca2+.
AuthorsHajnóczky G, Hager R, Thomas AP
JournalJ Biol Chem
PubMed ID10318833
The concerted action of inositol 1,4,5-trisphosphate (IP3) and Ca2+ on the IP3 receptor Ca2+ release channel (IP3R) is a fundamental step in the generation of cytosolic Ca2+ oscillations and waves, which underlie Ca2+ signaling in many cells. Mitochondria appear in close association with regions of endoplasmic reticulum (ER) enriched in ... More
Localized Na+/H+ exchanger 1 expression protects Ca2+-regulated adenylyl cyclases from changes in intracellular pH.
AuthorsWilloughby D, Masada N, Crossthwaite AJ, Ciruela A, Cooper DM
JournalJ Biol Chem
PubMed ID16002403
The Ca2+-sensitive adenylyl cyclases (ACs) are exclusively regulated by capacitative Ca2+ entry (CCE) in nonexcitable cells. The present study investigates whether this Ca2+-dependent modulation of AC activity is further regulated by local pH changes that can arise beneath the plasma membrane as a consequence of cellular activity. Ca2+ stimulation of ... More
Presynaptic mitochondrial calcium sequestration influences transmission at mammalian central synapses.
AuthorsBillups B, Forsythe ID
JournalJ Neurosci
PubMed ID12122046
Beyond their role in generating ATP, mitochondria have a high capacity to sequester calcium. The interdependence of these functions and limited access to presynaptic compartments makes it difficult to assess the role of sequestration in synaptic transmission. We addressed this important question using the calyx of Held as a model ... More
Rapid Ca2+ entry through Ca2+-permeable AMPA/Kainate channels triggers marked intracellular Ca2+ rises and consequent oxygen radical production.
AuthorsCarriedo SG, Yin HZ, Sensi SL, Weiss JH
JournalJ Neurosci
PubMed ID9742143
The widespread neuronal injury that results after brief activation of highly Ca2+-permeable NMDA channels may, in large part, reflect mitochondrial Ca2+ overload and the consequent production of injurious oxygen radicals. In contrast, AMPA/kainate receptor activation generally causes slower toxicity, and most studies have not found evidence of comparable oxygen radical ... More
Fast exocytosis with few Ca(2+) channels in insulin-secreting mouse pancreatic B cells.
AuthorsBarg S, Ma X, Eliasson L, Galvanovskis J, Göpel SO, Obermüller S, Platzer J, Renström E, Trus M, Atlas D, Striessnig J, Rorsman P
JournalBiophys J
PubMed ID11720994
The association of L-type Ca(2+) channels to the secretory granules and its functional significance to secretion was investigated in mouse pancreatic B cells. Nonstationary fluctuation analysis showed that the B cell is equipped with <500 alpha1(C) L-type Ca(2+) channels, corresponding to a Ca(2+) channel density of 0.9 channels per microm(2). ... More
Calcium influx constitutes the ionic basis for the maintenance of glutamate-induced extended neuronal depolarization associated with hippocampal neuronal death.
AuthorsLimbrick DD, Sombati S, DeLorenzo RJ
JournalCell Calcium
PubMed ID12531183
Excessive activation of neuronal glutamate receptors has been implicated in the pathophysiology of stroke, epilepsy, and traumatic brain injury. Previously, it has been demonstrated that excitotoxic glutamate exposure results in the induction of an extended neuronal depolarization (END), as well as protracted elevations in free intracellular calcium ([Ca(2+)](i)). Both END ... More
Endoplasmic reticulum D-myo-inositol 1,4,5-trisphosphate-sensitive stores regulate nuclear factor-kappaB binding activity in a calcium-independent manner.
The transcription factor nuclear factor-kappaB (NF-kappaB) plays critical roles in neuronal survival and plasticity and in activation of immune responses. The activation of NF-kappaB has been closely associated with changes in intracellular calcium levels, but the relationship between the two remains unclear. Here we report that inhibition of endoplasmic reticulum ... More