scholarly journals Inhibition of inositol 1,4,5-trisphosphate-mediated Ca2+ release by Ca2+ in cells from peripheral tissues.

1990 ◽  
Vol 265 (35) ◽  
pp. 21419-21422 ◽  
Author(s):  
H Zhao ◽  
S Muallem
Keyword(s):  
Peripheral Tissues ◽  
Inositol 1,4,5 Trisphosphate ◽  
In Cells

scholarly journals Effect of sphingosine derivatives on calcium fluxes in thyroid FRTL-5 cells

1994 ◽  
Vol 299 (1) ◽  
pp. 213-218 ◽  
Author(s):  
K Törnquist ◽  
E Ekokoski
Keyword(s):  
Elevated Level ◽  
Channel Blocker ◽  
Thyroid Stimulating Hormone ◽  
Thyroid Cell ◽  
Dependent Manner ◽  
Myristate Acetate ◽  
Permeabilized Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Dose Dependent ◽  
In Cells

The effects of sphingosine derivatives on Ca2+ fluxes were investigated in thyroid FRTL-5 cells labelled with Fura 2. Addition of sphingosylphosphocholine (SPC) or sphingosine (SP) increased intracellular free Ca2+ ([Ca2+]i) in a dose-dependent manner. At the highest dose tested (30 microM), the response was biphasic: a rapid transient increase in [Ca2+]i, followed by a new, elevated, level of [Ca2+]i. Both phases of the SPC-evoked increase in [Ca2+]i were dependent on extracellular Ca2+, whereas only the SP-evoked elevated level of [Ca2+]i was dependent on the influx of Ca2+. Both compounds released sequestered Ca2+ from thapsigargin- and inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ pools. In addition, the increase in [Ca2+]i in response to SPC, but not to SP, was attenuated in cells treated with phorbol myristate acetate or with the putative Ca(2+)-channel blocker SKF 96365, and in cells pretreated with pertussis toxin for 24 h. SPC did not activate the production of IP3. Furthermore, both SPC and SP released sequestered Ca2+ from permeabilized cells. We observed that SPC, but not SP, stimulated release of [3H]arachidonate from cells prelabelled with [3H]arachidonate for 24 h. Both SPC and SP stimulated the incorporation of [3H]thymidine into DNA in cells grown in the absence of thyroid-stimulating hormone (TSH). The results suggest that sphingosine derivatives are putative regulators of Ca2+ fluxes in FRTL-5 cells, and that SP and SPC may act on [Ca2+]i via different mechanisms. Furthermore, both SP and SPC may be of importance in modulating thyroid-cell proliferation.

scholarly journals Atp-Dependent Adenophostin Activation of Inositol 1,4,5-Trisphosphate Receptor Channel Gating

2001 ◽  
Vol 117 (4) ◽  
pp. 299-314 ◽  
Author(s):  
Don-On Daniel Mak ◽  
Sean McBride ◽  
J. Kevin Foskett
Keyword(s):  
Single Channel ◽  
Free Acid ◽  
Channel Gating ◽  
Xenopus Laevis Oocyte ◽  
Open Probability ◽  
Release Channel ◽  
Gating Kinetics ◽  
Inositol 1,4,5 Trisphosphate ◽  
Kinetics Of ◽  
In Cells

The inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) is a ligand-gated intracellular Ca2+ release channel that plays a central role in modulating cytoplasmic free Ca2+ concentration ([Ca2+]i). The fungal metabolite adenophostin A (AdA) is a potent agonist of the InsP3R that is structurally different from InsP3 and elicits distinct calcium signals in cells. We have investigated the effects of AdA and its analogues on single-channel activities of the InsP3R in the outer membrane of isolated Xenopus laevis oocyte nuclei. InsP3R activated by either AdA or InsP3 have identical channel conductance properties. Furthermore, AdA, like InsP3, activates the channel by tuning Ca2+ inhibition of gating. However, gating of the AdA-liganded InsP3R has a critical dependence on cytoplasmic ATP free acid concentration not observed for InsP3-liganded channels. Channel gating activated by AdA is indistinguishable from that elicited by InsP3 in the presence of 0.5 mM ATP, although the functional affinity of the channel is 60-fold higher for AdA. However, in the absence of ATP, gating kinetics of AdA-liganded InsP3R were very different. Channel open time was reduced by 50%, resulting in substantially lower maximum open probability than channels activated by AdA in the presence of ATP, or by InsP3 in the presence or absence of ATP. Also, the higher functional affinity of InsP3R for AdA than for InsP3 is nearly abolished in the absence of ATP. Low affinity AdA analogues furanophostin and ribophostin activated InsP3R channels with gating properties similar to those of AdA. These results provide novel insights for interpretations of observed effects of AdA on calcium signaling, including the mechanisms that determine the durations of elementary Ca2+ release events in cells. Comparisons of single-channel gating kinetics of the InsP3R activated by InsP3, AdA, and its analogues also identify molecular elements in InsP3R ligands that contribute to binding and activation of channel gating.

scholarly journals Regulation of Inositol 1,4,5-Trisphosphate 3-Kinases by Calcium and Localization in Cells

2007 ◽  
Vol 282 (13) ◽  
pp. 9526-9535 ◽  
Author(s):  
Samantha M. Lloyd-Burton ◽  
Jowie C. H. Yu ◽  
Robin F. Irvine ◽  
Michael J. Schell
Keyword(s):  
Inositol 1,4,5 Trisphosphate ◽  
In Cells

scholarly journals Functional Consequences of Phosphomimetic Mutations at Key cAMP-dependent Protein Kinase Phosphorylation Sites in the Type 1 Inositol 1,4,5-Trisphosphate Receptor

2004 ◽  
Vol 279 (44) ◽  
pp. 46242-46252 ◽  
Author(s):  
Larry E. Wagner ◽  
Wen-Hong Li ◽  
Suresh K. Joseph ◽  
David I. Yule
Keyword(s):  
Splice Variants ◽  
Phosphorylation Sites ◽  
Wild Type ◽  
Igm Antibody ◽  
Temporal Properties ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Spatio Temporal ◽  
In Cells

Regulation of Ca2+release through inositol 1,4,5-trisphosphate receptors (InsP3R) has important consequences for defining the particular spatio-temporal properties of intracellular Ca2+signals. In this study, regulation of Ca2+release by phosphorylation of type 1 InsP3R (InsP3R-1) was investigated by constructing “phosphomimetic” charge mutations in the functionally important phosphorylation sites of both the S2+ and S2- InsP3R-1 splice variants. Ca2+release was investigated following expression in Dt-40 3ko cells devoid of endogenous InsP3R. In cells expressing either the S1755E S2+ or S1589E/S1755E S2- InsP3R-1, InsP3-induced Ca2+release was markedly enhanced compared with nonphosphorylatable S2+ S1755A and S2- S1589A/S1755A mutants. Ca2+release through the S2- S1589E/S1755E InsP3R-1 was enhanced ∼8-fold over wild type and ∼50-fold when compared with the nonphosphorylatable S2- S1589A/S1755A mutant. In cells expressing S2- InsP3R-1 with single mutations in either S1589E or S1755E, the sensitivity of Ca2+release was enhanced ∼3-fold; sensitivity was midway between the wild type and the double glutamate mutation. Paradoxically, forskolin treatment of cells expressing either single Ser/Glu mutation failed to further enhance Ca2+release. The sensitivity of Ca2+release in cells expressing S2+ S1755E InsP3R-1 was comparable with the sensitivity of S2- S1589E/S1755E InsP3R-1. In contrast, mutation of S2+ S1589E InsP3R-1 resulted in a receptor with comparable sensitivity to wild type cells. Expression of S2- S1589E/S1755E InsP3R-1 resulted in robust Ca2+oscillations when cells were stimulated with concentrations of α-IgM antibody that were threshold for stimulation in S2- wild type InsP3R-1-expressing cells. However, at higher concentrations of α-IgM antibody, Ca2+oscillations of a similar period and magnitude were initiated in cells expressing either wild type or S2- phosphomimetic mutations. Thus, regulation by phosphorylation of the functional sensitivity of InsP3R-1 appears to define the threshold at which oscillations are initiated but not the frequency or amplitude of the signal when established.

scholarly journals Electroporation can cause artefacts due to solubilization of cations from the electrode plates. Aluminum ions enhance conversion of inositol 1,3,4,5-tetrakisphosphate into inositol 1,4,5-trisphosphate in electroporated L1210 cells

1991 ◽  
Vol 277 (3) ◽  
pp. 883-885 ◽  
Author(s):  
J W Loomis-Husselbee ◽  
P J Cullen ◽  
R F Irvine ◽  
A P Dawson
Keyword(s):  
Experimental System ◽  
Experimental Medium ◽  
Assay Medium ◽  
L1210 Cells ◽  
Aluminum Ions ◽  
Inositol 1,4,5 Trisphosphate ◽  
The Difference ◽  
High Concentrations ◽  
As If ◽  
In Cells

1. In electroporated L1210 cells, Ins(1,3,4,5)P4 causes Ca2+ release, owing to its conversion into Ins(1,4,5)P3, but this does not happen in cells permeabilized by digitonin treatment [Cullen, Irvine, Drøbak & Dawson (1989) Biochem. J. 259, 931-933]. 2. If the assay medium is subjected to electroporation by using a commercially available electroporation apparatus and then the cells are added and permeabilized with digitonin, the cells behave as if they had been electroporated. 3. Electroporation causes the release of high concentrations of Al3+ into the experimental medium, and addition of these concentrations of Al3+ into the experimental medium mimics the effect of electroporation on the conversion of Ins(1,3,4,5)P4 into Ins(1,4,5)P3. 4. It is concluded that the difference between electroporated and digitonin-permeabilized L1210 cells in this experimental system can be attributed to dissolution of Al3+ from the electroporation cuvette. Al3+ contamination may thus be a serious problem when using this apparatus.

scholarly journals The regulatory domain of the inositol 1,4,5-trisphosphate receptor is necessary to keep the channel domain closed: possible physiological significance of specific cleavage by caspase 3

2004 ◽  
Vol 377 (2) ◽  
pp. 299-307 ◽  
Author(s):  
Tomohiro NAKAYAMA ◽  
Mitsuharu HATTORI ◽  
Keiko UCHIDA ◽  
Takeshi NAKAMURA ◽  
Yoko TATEISHI ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Caspase 3 ◽  
Fluorescent Protein ◽  
Binding Domain ◽  
Ligand Binding Domain ◽  
Physiological Significance ◽  
Regulatory Domain ◽  
Inositol 1,4,5 Trisphosphate ◽  
Trisphosphate Receptor ◽  
In Cells

The type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) is an intracellular Ca2+ channel protein that plays crucial roles in generating complex Ca2+ signalling patterns. IP3R1 consists of three domains: a ligand-binding domain, a regulatory domain and a channel domain. In order to investigate the function of these domains in its gating machinery and the physiological significance of specific cleavage by caspase 3 that is observed in cells undergoing apoptosis, we utilized various IP3R1 constructs tagged with green fluorescent protein (GFP). Expression of GFP-tagged full-length IP3R1 or IP3R1 lacking the ligand-binding domain in HeLa and COS-7 cells had little effect on cells’ responsiveness to an IP3-generating agonist ATP and Ca2+ leak induced by thapsigargin. On the other hand, in cells expressing the caspase-3-cleaved form (GFP–IP3R1-casp) or the channel domain alone (GFP–IP3R1-ES), both ATP and thapsigargin failed to induce increase of cytosolic Ca2+ concentration. Interestingly, store-operated (−like) Ca2+ entry was normally observed in these cells, irrespective of thapsigargin pre-treatment. These findings indicate that the Ca2+ stores of cells expressing GFP–IP3R1-casp or GFP–IP3R1-ES are nearly empty in the resting state and that these proteins continuously leak Ca2+. We therefore propose that the channel domain of IP3R1 tends to remain open and that the large regulatory domain of IP3R1 is necessary to keep the channel domain closed. Thus cleavage of IP3R1 by caspase 3 may contribute to the increased cytosolic Ca2+ concentration often observed in cells undergoing apoptosis. Finally, GFP–IP3R1-casp or GFP–IP3R1-ES can be used as a novel tool to deplete intracellular Ca2+ stores.

scholarly journals Lithium stimulates accumulation of second-messenger inositol 1,4,5-trisphosphate and other inositol phosphates in mouse pancreatic minilobules without inositol supplementation

1994 ◽  
Vol 304 (1) ◽  
pp. 251-258 ◽  
Author(s):  
J F Dixon ◽  
L E Hokin
Keyword(s):  
Cerebral Cortex ◽  
Phospholipase C ◽  
Feedback Inhibition ◽  
Inositol Phosphates ◽  
Plasma Concentrations ◽  
Second Messenger ◽  
Inositol Polyphosphates ◽  
Peripheral Tissues ◽  
Inositol 1,4,5 Trisphosphate ◽  
Cortex Slices

Previous studies showed that lithium, beginning at therapeutic plasma concentrations in the treatment of manic depression, increased the accumulation of second-messenger inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] in cerebral cortex slices of guinea pig and rhesus monkey [Lee, Dixon, Reichman, Moummi, Los and Hokin (1992) Biochem. J. 282, 377-385; Dixon, Lee, Los and Hokin (1992) J. Neurochem. 59, 2332-2335; Dixon, Los and Hokin (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 8358-8362]. These studies have now been extended to a peripheral tissue, mouse pancreatic minilobules. In the presence of carbachol, concentrations of lithium from 1 to 20 mM sharply and progressively increased the accumulation of Ins(1,4,5)P3 and inositol 1,3,4,5-tetrakisphosphate, followed by a decrease. Assay of these inositol polyphosphates by either the prelabelling technique or mass assay gave similar results. Atropine quenching of cholinergically stimulated pancreatic minilobules led to a rapid disappearance of Ins(1,4,5)P3. This disappearance was impeded by lithium. This suggested that the lithium-induced elevation in Ins(1,4,5)P3 was due to inhibition of the 5-phosphatase and, on the basis of the markedly elevated concentrations of inositol 1,3,4-trisphosphate [Ins(1,3,4)P3] and inositol 1,4-bisphosphate in the presence of lithium, probably by feedback inhibition by these latter two compounds. An additional mechanism, i.e. a stimulatory effect of lithium on phospholipase C, cannot, however, be ruled out. The other reaction product of phospholipase C, inositol cyclic 1:2,4,5-trisphosphate, also increased in the presence of lithium. This may also be due to inhibition of the 5-phosphatase, which is the exclusive mechanism for removal of this compound. The effects of lithium on the accumulation of other inositol phosphates paralleled that of Ins(1,4,5)P3, with the exception of inositol 3,4-bisphosphate, which decreased. This was presumably due to the inhibition of Ins(1,3,4)P3 1-phosphatase by lithium. Unlike mouse cerebral cortex slices [Lee, Dixon, Reichman, Moummi, Los and Hokin (1992) Biochem. J. 282, 377-385], inositol supplementation was not required to demonstrate lithium-stimulated Ins(1,4,5)P3 accumulation in mouse pancreatic minilobules. This indicates that inositol depletion sufficient to impair lithium-stimulated Ins(1,4,5)P3 accumulation does not occur in mouse pancreatic minilobules, even though an elevation of cytidine diphosphodiacylglycerol occurred, indicating some inositol depletion due to lithium. Elevation of Ins(1,4,5)P3 by lithium may be a general phenomenon in the central nervous system and peripheral tissues under non-rate-limiting concentrations of inositol.

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