scholarly journals Cross-talk between Native Plasmalemmal Na+/Ca2+Exchanger and Inositol 1,4,5-Trisphosphate-sensitive Ca2+Internal Store inXenopusOocytes

2004 ◽  
Vol 279 (50) ◽  
pp. 52414-52424 ◽  
Author(s):  
Luisa M. Solís-Garrido ◽  
Antonio J. Pintado ◽  
Eva Andrés-Mateos ◽  
María Figueroa ◽  
Carlos Matute ◽  
...  
Keyword(s):  
Confocal Microscopy ◽  
Surface Membrane ◽  
Rabbit Serum ◽  
Caged Compounds ◽  
Reverse Transcription Pcr ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Functional Consequences ◽  
Extracellular Sodium ◽  
Cortical Endoplasmic Reticulum

Because the presence of a native plasmalemmal Na+/Ca2+exchange (NCX) activity inXenopus laevisoocytes remains controversial, its possible functional role in these cells is poorly understood. Here, in experiments on control oocytes and oocytes overexpressing a cloned NCX1 cardiac protein, confocal microscopy combined with electrophysiological techniques reveal that these cells express an endogenous NCX protein forming a functional microdomain with inositol 1,4,5-trisphosphate receptors (InsP3R) that controls intracellular Ca2+in a restricted subplasmalemmal space. The following data obtained in control denuded oocytes are consistent with this view: (i) reverse transcription-PCR revealed that the oocyte expresses two transcripts for the NCX1 and NCX3 isoforms; (ii) immunofluorescence experiments showed that native NCX1 and InsP3Rs are largely codistributed in discrete areas of the plasma membrane in close apposition to the cortical endoplasmic reticulum shell; (iii) when stimulated by rabbit serum, which elevates intracellular Ca2+mediated by InsP3, voltage-clamped oocytes display a large and transient inward Ca2+-activated chloride current, ICl(Ca), as a result of the Ca2+rise at the inner surface membrane; (iv) this current is significantly enhanced by KB-R7943 and by an extracellular sodium-depleted medium, two maneuvers that prevent “Ca2+extrusion” via NCX; and (v) blocking NCX enhanced the ICl(Ca)elicited by InsP3but not by Ca2+photolysis in oocytes injected with the respective caged compounds. Moreover, overexpression of cardiac NCX1, confirmed by confocal microscopy, has functional consequences for the “Ca2+influx” but not for the serum-elicited “Ca2+efflux” mode of basal exchange activity and does not alter the number of endogenous NCX/InsP3Rs colocalization sites. Our results suggest that native NCX, because of its strategic position, may regulate InsP3-mediated Ca2+signaling during the early phases of oocyte maturation and/or fertilization, and furthermore foreign cardiac protein is excluded from the Ca2+microdomains surrounding the native NCX/InsP3Rs complex in the oocyte.

scholarly journals Calpain-cleaved Type 1 Inositol 1,4,5-Trisphosphate Receptor (InsP3R1) Has InsP3-independent Gating and Disrupts Intracellular Ca2+ Homeostasis

2011 ◽  
Vol 286 (41) ◽  
pp. 35998-36010 ◽  
Author(s):  
Catherine M. Kopil ◽  
Horia Vais ◽  
King-Ho Cheung ◽  
Adam P. Siebert ◽  
Don-On Daniel Mak ◽  
...  
Keyword(s):  
Single Channel ◽  
Open Probability ◽  
Release Channel ◽  
Terminal Fragment ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Functional Consequences ◽  
Carboxyl Terminal ◽  
Trisphosphate Receptor

The type 1 inositol 1,4,5-trisphosphate receptor (InsP3R1) is a ubiquitous intracellular Ca2+ release channel that is vital to intracellular Ca2+ signaling. InsP3R1 is a proteolytic target of calpain, which cleaves the channel to form a 95-kDa carboxyl-terminal fragment that includes the transmembrane domains, which contain the ion pore. However, the functional consequences of calpain proteolysis on channel behavior and Ca2+ homeostasis are unknown. In the present study we have identified a unique calpain cleavage site in InsP3R1 and utilized a recombinant truncated form of the channel (capn-InsP3R1) corresponding to the stable, carboxyl-terminal fragment to examine the functional consequences of channel proteolysis. Single-channel recordings of capn-InsP3R1 revealed InsP3-independent gating and high open probability (Po) under optimal cytoplasmic Ca2+ concentration ([Ca2+]i) conditions. However, some [Ca2+]i regulation of the cleaved channel remained, with a lower Po in suboptimal and inhibitory [Ca2+]i. Expression of capn-InsP3R1 in N2a cells reduced the Ca2+ content of ionomycin-releasable intracellular stores and decreased endoplasmic reticulum Ca2+ loading compared with control cells expressing full-length InsP3R1. Using a cleavage-specific antibody, we identified calpain-cleaved InsP3R1 in selectively vulnerable cerebellar Purkinje neurons after in vivo cardiac arrest. These findings indicate that calpain proteolysis of InsP3R1 generates a dysregulated channel that disrupts cellular Ca2+ homeostasis. Furthermore, our results demonstrate that calpain cleaves InsP3R1 in a clinically relevant injury model, suggesting that Ca2+ leak through the proteolyzed channel may act as a feed-forward mechanism to enhance cell death.

scholarly journals Caffeine-induced inhibition of inositol(1,4,5)-trisphosphate-gated calcium channels from cerebellum.

1994 ◽  
Vol 5 (1) ◽  
pp. 97-103 ◽  
Author(s):  
I Bezprozvanny ◽  
S Bezprozvannaya ◽  
B E Ehrlich
Keyword(s):  
Lipid Bilayers ◽  
Inhibitory Action ◽  
Single Channel ◽  
Ryanodine Receptors ◽  
Single Channels ◽  
Ca Channels ◽  
Open Time ◽  
Inositol 1,4,5 Trisphosphate ◽  
Insp3 Receptors ◽  
Intracellular Ca

Effects of the xanthine drug caffeine on inositol (1,4,5)-trisphosphate (InsP3)-gated calcium (Ca) channels from canine cerebellum were studied using single channels incorporated into planar lipid bilayers. Caffeine, used widely as an agonist of ryanodine receptors, inhibited the activity of InsP3-gated Ca channels in a noncooperative fashion with half-inhibition at 1.64 mM caffeine. The frequency of channel openings was decreased more than threefold after addition of 5 mM caffeine; there was only a small effect on mean open time of the channels, and the single channel conductance was unchanged. Increased InsP3 concentration overcame the inhibitory action of caffeine, but caffeine did not reduce specific [3H]InsP3 binding to the receptor. The inhibitory action of caffeine on InsP3 receptors suggests that the action of caffeine on the intracellular Ca pool must be interpreted with caution when both ryanodine receptors and InsP3 receptors are present in the cell.

Differential modulation of caffeine- and IP3-induced calcium release in cultured arterial tissue

1999 ◽  
Vol 276 (5) ◽  
pp. C1115-C1120 ◽  
Author(s):  
Karl Dreja ◽  
Per Hellstrand
Keyword(s):  
Calcium Release ◽  
Cyclopiazonic Acid ◽  
Differential Modulation ◽  
Transient Responses ◽  
Inositol 1,4,5 Trisphosphate ◽  
Arterial Tissue ◽  
Intracellular Ca ◽  
Rat Tail

To investigate the Ca2+-dependent plasticity of sarcoplasmic reticulum (SR) function in vascular smooth muscle, transient responses to agents releasing intracellular Ca2+ by either ryanodine (caffeine) ord- myo-inositol 1,4,5-trisphosphate [IP3; produced in response to norepinephrine (NE), 5-hydroxytryptamine (5-HT), arginine vasopressin (AVP)] receptors in rat tail arterial rings were evaluated after 4 days of organ culture. Force transients induced by all agents were increased compared with those induced in fresh rings. Stimulation by 10% FCS during culture further potentiated the force and Ca2+ responses to caffeine (20 mM) but not to NE (10 μM), 5-HT (10 μM), or AVP (0.1 μM). The effect was persistent, and SR capacity was not altered after reversible depletion of stores with cyclopiazonic acid. The effects of serum could be mimicked by culture in depolarizing medium (30 mM K+) and blocked by the addition of verapamil (1 μM) or EGTA (1 mM) to the medium, lowering intracellular Ca2+ concentration ([Ca2+]i) during culture. These results show that modulation of SR function can occur in vitro by a mechanism dependent on long-term levels of basal [Ca2+]iand involving ryanodine- but not IP3 receptor-mediated Ca2+release.

Three different calcium wave pacemakers in ascidian eggs

2001 ◽  
Vol 114 (13) ◽  
pp. 2471-2481 ◽  
Author(s):  
Rémi Dumollard ◽  
Christian Sardet
Keyword(s):  
Cytochalasin B ◽  
Calcium Wave ◽  
Spatiotemporal Variations ◽  
Microtubule Depolymerization ◽  
Rich Domain ◽  
Opposite Pole ◽  
Inositol 1,4,5 Trisphosphate ◽  
On Line ◽  
Cortical Endoplasmic Reticulum ◽  
Sperm Aster

Calcium wave pacemakers in fertilized eggs of ascidians and mouse are associated with accumulations of cortical endoplasmic reticulum in the vegetal hemisphere. In ascidians, two distinct pacemakers (PM1 and PM2) generate two series of calcium waves necessary to drive meiosis I and II. Pacemaker PM2 is stably localized in a cortical ER accumulation situated in the vegetal contraction pole. We now find that pacemaker PM1 is situated in a cortical ER-rich domain that forms around the sperm aster and moves with it during the calcium-dependant cortical contraction triggered by the fertilizing sperm. Global elevations of inositol (1,4,5)-trisphosphate (Ins(1,4,5)P3) levels produced by caged Ins(1,4,5)P3 or caged glycero-myo-PtdIns(4,5)P2 photolysis reveal that the cortex of the animal hemisphere, also rich in ER-clusters, is the cellular region most sensitive to Ins(1,4,5)P3 and acts as a third type of pacemaker (PM3). Surprisingly, the artificial pacemaker PM3 predominates over the natural pacemaker PM2, located at the opposite pole. Microtubule depolymerization does not alter the activity nor the location of the three pacemakers. By contrast, blocking the acto-myosin driven cortical contraction with cytochalasin B prevents PM1 migration and inhibits PM2 activity. PM3, however, is insensitive to cytochalasin B. Our experiments suggest that the three distinct calcium wave pacemakers are probably regulated by different spatiotemporal variations in Ins(1,4,5)P3 concentration. In particular, the activity of the natural calcium wave pacemakers PM1 and PM2 depends on the apposition of a cortical ER-rich domain to a source of Ins(1,4,5)P3 production in the cortex. Movies available on-line

Bombesin-evoked gastrin release and calcium signaling in human antral G cells in culture

1999 ◽  
Vol 276 (1) ◽  
pp. G227-G237 ◽  
Author(s):  
Paul E. Squires ◽  
R. Mark Meloche ◽  
Alison M. J. Buchan
Keyword(s):  
Cell Culture ◽  
Calcium Signaling ◽  
Gastrin Release ◽  
Voltage Gated ◽  
Gastrin Releasing Peptide ◽  
G Cells ◽  
Peptide Family ◽  
Inositol 1,4,5 Trisphosphate ◽  
Voltage Dependent ◽  
Intracellular Ca

Amplification of mRNA from a human antral cell culture preparation demonstrated the presence of two receptors of the bombesin and gastrin-releasing peptide family, GRPR-1 and BRS-3. Single cell microfluorometry demonstrated that most cells that exhibited bombesin-evoked changes in intracellular Ca2+ concentration were gastrin immunoreactive, indicating that antral G cells express the GRPR subtype. There were two components to the intracellular Ca2+ response: an initial nitrendipine-insensitive mobilization followed by a sustained phase that was inhibited by removal of extracellular Ca2+ and 20 mM caffeine and was partially inhibited by 10 μM nitrendipine. Preexposure of cells to thapsigargin and caffeine prevented the response to bombesin, indicating activation of inositol 1,4,5-trisphosphate (IP3)-sensitive stores. Gastrin release could be partially reversed by removal of extracellular Ca2+ and blockade of L-type voltage-dependent Ca2+ channels, indicating that a component of the secretory response to bombesin was dependent on Ca2+ influx. These data demonstrated that bombesin-stimulated gastrin release from human antral G cells resulted from activation of GRPRs and involved both release of intracellular Ca2+ and influx of extracellular Ca2+through a combination of L-type voltage-gated and IP3-gated Ca2+ channels.

Mobilization of Intracellular Calcium by Methacholine and Inositol 1,4,5-Trisphosphate in Rat Parotid Acinar Cells

1987 ◽  
Vol 66 (2) ◽  
pp. 547-551 ◽  
Author(s):  
D.L. Aub ◽  
J.W. Putney
Keyword(s):  
Receptor Activation ◽  
Transient Phase ◽  
Cell Preparation ◽  
Similar Concentration ◽  
Parotid Acinar Cells ◽  
Parotid Acinar Cell ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Rat Parotid ◽  
Stimulation Of

In the rat parotid acinar cell, methacholine caused an increase in [Ca2+]i as determined by quin-2 fluorescence. The increase in [Ca2+] i was initially independent of, and subsequently dependent on, the presence of extracellular Ca2+, indicating mobilization of intracellular Ca2+, as well as activation of Ca2+ entry. Methacholine mobilization of the internal Ca2+ pool and stimulation of the initial transient phase of K+ efflux have similar concentration dependencies; the EC50 value for Ca2+ mobilization is 80 nmollL, the EC50 value for K+ efflux is 200 nmol/L. In a permeable parotid cell preparation, inositol 1,4,5-trisphosphate, inositol 2,4,5-trisphosphate, and inositol 4,5-bisphosphate were able to release Ca2+ from an ATP-dependent, oligomycininsensitive pool. These observations, when taken with the previous finding that methacholine stimulates Ca-independent inositol trisphosphate formation, support the view that inositol 1,4,5-trisphosphate acts as a second messenger mediating the release of an intracellular Ca 2+ pool following muscarinic receptor activation in the parotid gland.

Effect of halothane on intracellular calcium oscillations in porcine tracheal smooth muscle cells

1999 ◽  
Vol 276 (1) ◽  
pp. L81-L89 ◽  
Author(s):  
Christina M. Pabelick ◽  
Y. S. Prakash ◽  
Mathur S. Kannan ◽  
Keith A. Jones ◽  
David O. Warner ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Ryanodine Receptor ◽  
Muscle Cells ◽  
Calcium Oscillations ◽  
Tracheal Smooth Muscle ◽  
Permeabilized Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Trisphosphate Receptor

The effect of halothane on intracellular Ca2+ concentration ([Ca2+]i) regulation in porcine tracheal smooth muscle cells was examined with real-time confocal microscopy. Both 1 and 2 minimum alveolar concentration (MAC) halothane increased basal [Ca2+]iwhen Ca2+ influx and efflux were blocked, suggesting increased sarcoplasmic reticulum (SR) Ca2+ leak and/or decreased reuptake. In β-escin-permeabilized cells, heparin inhibition of inositol 1,4,5-trisphosphate-receptor channels blunted the halothane-induced increase in [Ca2+]i. Both 1 and 2 MAC halothane decreased the frequency and amplitude of ACh-induced [Ca2+]ioscillations (which represent SR Ca2+ release through ryanodine-receptor channels), abolishing oscillations in ∼20% of tracheal smooth muscle cells at 2 MAC. When Ca2+ influx and efflux were blocked, halothane increased the baseline and decreased the frequency and amplitude of [Ca2+]ioscillations, inhibiting oscillations in ∼70% of cells at 2 MAC. The fall time of [Ca2+]ioscillations and the rate of fall of the [Ca2+]iresponse to caffeine were both increased by halothane. These results suggest that halothane abolishes agonist-induced [Ca2+]ioscillations by 1) depleting SR Ca2+ via increased Ca2+ leak through inositol 1,4,5-trisphosphate-receptor channels, 2) decreasing Ca2+ release through ryanodine-receptor channels, and 3) inhibiting reuptake.

Hypotonic swelling-induced Ca2+ release by an IP3-insensitive Ca2+ store

2001 ◽  
Vol 281 (2) ◽  
pp. C555-C562 ◽  
Author(s):  
Madhumita Jena Mohanty ◽  
Maian Ye ◽  
Xingli Li ◽  
Noreen F. Rossi
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Nicotinic Acid ◽  
Vascular Smooth Muscle Cells ◽  
Ruthenium Red ◽  
A7r5 Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Hypotonic Swelling

Hypotonic swelling increases the intracellular Ca2+ concentration ([Ca2+]i) in vascular smooth muscle cells (VSMC). The source of this Ca2+ is not clear. To study the source of increase in [Ca2+]i in response to hypotonic swelling, we measured [Ca2+]i in fura 2-loaded cultured VSMC (A7r5 cells). Hypotonic swelling produced a 40.7-nM increase in [Ca2+]i that was not inhibited by EGTA but was inhibited by 1 μM thapsigargin. Prior depletion of inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ stores with vasopressin did not inhibit the increase in [Ca2+]i in response to hypotonic swelling. Exposure of 45Ca2+-loaded intracellular stores to hypotonic swelling in permeabilized VSMC produced an increase in45Ca2+ efflux, which was inhibited by 1 μM thapsigargin but not by 50 μg/ml heparin, 50 μM ruthenium red, or 25 μM thio-NADP. Thus hypotonic swelling of VSMC causes a release of Ca2+ from the intracellular stores from a novel site distinct from the IP3-, ryanodine-, and nicotinic acid adenine dinucleotide phosphate-sensitive stores.

scholarly journals Normal brain ageing: models and mechanisms

2005 ◽  
Vol 360 (1464) ◽  
pp. 2347-2354 ◽  
Author(s):  
Emil C Toescu
Keyword(s):  
Neuronal Loss ◽  
Normal Activity ◽  
Normal Brain ◽  
Atp Production ◽  
Brain Ageing ◽  
Intracellular Ca ◽  
Functional Consequences ◽  
Metabolic Interactions ◽  
Normal Ageing ◽  
The Relationship

Normal ageing is associated with a degree of decline in a number of cognitive functions. Apart from the issues raised by the current attempts to expand the lifespan, understanding the mechanisms and the detailed metabolic interactions involved in the process of normal neuronal ageing continues to be a challenge. One model, supported by a significant amount of experimental evidence, views the cellular ageing as a metabolic state characterized by an altered function of the metabolic triad: mitochondria–reactive oxygen species (ROS)–intracellular Ca 2+ . The perturbation in the relationship between the members of this metabolic triad generate a state of decreased homeostatic reserve, in which the aged neurons could maintain adequate function during normal activity, as demonstrated by the fact that normal ageing is not associated with widespread neuronal loss, but become increasingly vulnerable to the effects of excessive metabolic loads, usually associated with trauma, ischaemia or neurodegenerative processes. This review will concentrate on some of the evidence showing altered mitochondrial function with ageing and also discuss some of the functional consequences that would result from such events, such as alterations in mitochondrial Ca 2+ homeostasis, ATP production and generation of ROS.

Sign in / Sign up

Export Citation Format

Share Document