scholarly journals Thimerosal stimulates Ca2+ flux through inositol 1,4,5-trisphosphate receptor type 1, but not type 3, via modulation of an isoform-specific Ca2+-dependent intramolecular interaction

2004 ◽  
Vol 381 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Geert BULTYNCK ◽  
Karolina SZLUFCIK ◽  
Nael Nadif KASRI ◽  
Zerihun ASSEFA ◽  
Geert CALLEWAERT ◽  
...  
Keyword(s):  
Amino Acids ◽  
Conformational Changes ◽  
Intramolecular Interaction ◽  
Binding Activity ◽  
Release Channel ◽  
B Lymphoma Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Adenophostin A ◽  
Binding Core ◽  
Trisphosphate Receptor

Thiol-reactive agents such as thimerosal have been shown to modulate the Ca2+-flux properties of IP3 (inositol 1,4,5-trisphosphate) receptor (IP3R) via an as yet unidentified mechanism [Parys, Missiaen, De Smedt, Droogmans and Casteels (1993) Pflügers Arch. 424, 516–522; Kaplin, Ferris, Voglmaier and Snyder (1994) J. Biol. Chem. 269, 28972–28978; Missiaen, Taylor and Berridge (1992) J. Physiol. (Cambridge, U.K.) 455, 623–640; Missiaen, Parys, Sienaert, Maes, Kunzelmann, Takahashi, Tanzawa and De Smedt (1998) J. Biol. Chem. 273, 8983–8986]. In the present study, we show that thimerosal potentiated IICR (IP3-induced Ca2+ release) and IP3-binding activity of IP3R1, expressed in triple IP3R-knockout R23-11 cells derived from DT40 chicken B lymphoma cells, but not of IP3R3 or [Δ1–225]-IP3R1, which lacks the N-terminal suppressor domain. Using a 45Ca2+-flux technique in permeabilized A7r5 smooth-muscle cells, we have shown that Ca2+ shifted the stimulatory effect of thimerosal on IICR to lower concentrations of thimerosal and thereby increased the extent of Ca2+ release. This suggests that Ca2+ and thimerosal synergetically regulate IP3R1. Glutathione S-transferase pull-down experiments elucidated an interaction between amino acids 1–225 (suppressor domain) and amino acids 226–604 (IP3-binding core) of IP3R1, and this interaction was strengthened by both Ca2+ and thimerosal. In contrast, calmodulin and sCaBP-1 (short Ca2+-binding protein-1), both having binding sites in the 1–225 region, weakened the interaction. This interaction was not found for IP3R3, in agreement with the lack of functional stimulation of this isoform by thimerosal. The interaction between the IP3-binding and transmembrane domains (amino acids 1–604 and 2170–2749 respectively) was not affected by thimerosal and Ca2+, but it was significantly inhibited by IP3 and adenophostin A. Our results demonstrate that thimerosal and Ca2+ induce isoform-specific conformational changes in the N-terminal part of IP3R1, leading to the formation of a highly IP3-sensitive Ca2+-release channel.

scholarly journals Insulin Promotes the Association of Heat Shock Protein 90 with the Inositol 1,4,5-Trisphosphate Receptor to Dampen Its Ca2+ Release Activity

Endocrinology ◽  
2009 ◽  
Vol 150 (5) ◽  
pp. 2190-2196 ◽  
Author(s):  
Nathalie Nguyen ◽  
Nancy Francoeur ◽  
Valérie Chartrand ◽  
Klaus Klarskov ◽  
Gaétan Guillemette ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Protein ◽  
Protein Interactions ◽  
Mammalian Target Of Rapamycin ◽  
Src Kinase ◽  
Target Of Rapamycin ◽  
Resting Cells ◽  
Release Channel ◽  
Inositol 1,4,5 Trisphosphate ◽  
Trisphosphate Receptor

The inositol 1,4,5-trisphosphate receptor (IP3R) is a Ca2+ release channel that plays a pivotal role in regulating intracellular Ca2+ levels in resting cells. Three isoforms of IP3Rs have been identified, and they all possess a large regulatory domain that covers about 60% of the protein. This regulation is accomplished by interaction with small molecules, posttranslational modifications, and mostly protein-protein interactions. In our search for new binding partners of the IP3R, we found that 90-kDa heat-shock protein (Hsp90) binds to the IP3R. This interaction increased on stimulation of HEK293T6.11 cells with insulin but not with Gq protein-coupled receptor (GqPCR) agonists. Moreover, the Hsp90 inhibitor geldanamycin (GA) disrupted the interaction between Hsp90 and the IP3R. Pretreatment of HEK293T6.11 cells with GA greatly increased the intracellular Ca2+ release induced by a GqPCR agonist. Insulin alone did not induce any intracellular Ca2+ release. However, insulin diminished the intracellular Ca2+ release induced by a GqPCR agonist. Interestingly, GA abolished the inhibitory effect of insulin on GqPCR-induced intracellular Ca2+ release. Furthermore, in our search for a mechanistic explanation to this phenomenon, we found that inhibition of kinases activated downstream of the insulin receptor greatly increased the interaction between Hsp90 and the IP3R. Of greater interest, we found that the simultaneous inhibition of mammalian target of rapamycin and the Src kinase almost completely disrupted the interaction between Hsp90 and the IP3R. These results demonstrate that insulin promotes the interaction of Hsp90 with the IP3R to dampen its Ca2+ release activity by a complex mechanism involving mammalian target of rapamycin and the Src kinase.

scholarly journals Two-state Conformational Changes in Inositol 1,4,5-Trisphosphate Receptor Regulated by Calcium

2002 ◽  
Vol 277 (24) ◽  
pp. 21115-21118 ◽  
Author(s):  
Kozo Hamada ◽  
Tomoko Miyata ◽  
Kouta Mayanagi ◽  
Junji Hirota ◽  
Katsuhiko Mikoshiba
Keyword(s):  
Conformational Changes ◽  
Inositol 1,4,5 Trisphosphate ◽  
Trisphosphate Receptor

The IP3 receptor/Ca2+ channel and its cellular function

2007 ◽  
Vol 74 ◽  
pp. 9-22 ◽  
Author(s):  
Katsuhiko Mikoshiba
Keyword(s):  
Exocrine Secretion ◽  
Axis Formation ◽  
Ip3 Receptor ◽  
Release Channel ◽  
Saliva Secretion ◽  
Binding Core ◽  
Gastric Juice Secretion ◽  
Trisphosphate Receptor ◽  
Type 3

The IP3R [IP3 (inositol 1,4,5-trisphosphate) receptor] is responsible for Ca2+ release from the ER (endoplasmic reticulum). We have been working extensively on the P400 protein, which is deficient in Purkinje-neuron-degenerating mutant mice. We have discovered that P400 is an IP3R and we have determined the primary sequence. Purified IP3R, when incorporated into a lipid bilayer, works as a Ca2+ release channel and overexpression of IP3R shows enhanced IP3 binding and channel activity. Addition of an antibody blocks Ca2+ oscillations indicating that IP3R1 works as a Ca2+ oscillator. Studies on the role of IP3R during development show that IP3R is involved in fertilization and is essential for determination of dorso-ventral axis formation. We found that IP3R is involved in neuronal plasticity. A double homozygous mutant of IP3R2 (IP3R type 2) and IP3R3 (IP3R type 3) shows a deficit of saliva secretion and gastric juice secretion suggesting that IP3Rs are essential for exocrine secretion. IP3R has various unique properties: cryo-EM (electron microscopy) studies show that IP3R contains multiple cavities; IP3R allosterically and dynamically changes its form reversibly (square form–windmill form); IP3R is functional even though it is fragmented by proteases into several pieces; the ER forms a meshwork but also forms vesicular ER and moves along microtubules using a kinesin motor; X ray analysis of the crystal structure of the IP3 binding core consists of an N-terminal β-trefoil domain and a C-terminal α-helical domain. We have discovered ERp44 as a redox sensor in the ER which binds to the luminal part of IP3R1 and regulates its activity. We have also found the role of IP3 is not only to release Ca2+ but also to release IRBIT which binds to the IP3 binding core of IP3R.

Molecular Recognition of Adenophostin, a Very Potent Ca2+Inducer, at thed-myo-Inositol 1,4,5-Trisphosphate Receptor‡

Biochemistry ◽  
1999 ◽  
Vol 38 (29) ◽  
pp. 9234-9241 ◽  
Author(s):  
Hitoshi Hotoda ◽  
Kazuhiro Murayama ◽  
Shuichi Miyamoto ◽  
Yoriko Iwata ◽  
Masaaki Takahashi ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Inositol 1,4,5 Trisphosphate ◽  
Adenophostin A ◽  
Trisphosphate Receptor

scholarly journals Permeant calcium ion feed-through regulation of single inositol 1,4,5-trisphosphate receptor channel gating

2012 ◽  
Vol 140 (6) ◽  
pp. 697-716 ◽  
Author(s):  
Horia Vais ◽  
J. Kevin Foskett ◽  
Ghanim Ullah ◽  
John E. Pearson ◽  
Don-On Daniel Mak
Keyword(s):  
Posttranslational Modifications ◽  
Imaging Techniques ◽  
Channel Gating ◽  
Channel Activity ◽  
Release Channel ◽  
Solution Exchange ◽  
Inositol 1,4,5 Trisphosphate ◽  
Direct Binding ◽  
Trisphosphate Receptor ◽  
Type 3

The ubiquitous inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) Ca2+ release channel plays a central role in the generation and modulation of intracellular Ca2+ signals, and is intricately regulated by multiple mechanisms including cytoplasmic ligand (InsP3, free Ca2+, free ATP4−) binding, posttranslational modifications, and interactions with cytoplasmic and endoplasmic reticulum (ER) luminal proteins. However, regulation of InsP3R channel activity by free Ca2+ in the ER lumen ([Ca2+]ER) remains poorly understood because of limitations of Ca2+ flux measurements and imaging techniques. Here, we used nuclear patch-clamp experiments in excised luminal-side-out configuration with perfusion solution exchange to study the effects of [Ca2+]ER on homotetrameric rat type 3 InsP3R channel activity. In optimal [Ca2+]i and subsaturating [InsP3], jumps of [Ca2+]ER from 70 nM to 300 µM reduced channel activity significantly. This inhibition was abrogated by saturating InsP3 but restored when [Ca2+]ER was raised to 1.1 mM. In suboptimal [Ca2+]i, jumps of [Ca2+]ER (70 nM to 300 µM) enhanced channel activity. Thus, [Ca2+]ER effects on channel activity exhibited a biphasic dependence on [Ca2+]i. In addition, the effect of high [Ca2+]ER was attenuated when a voltage was applied to oppose Ca2+ flux through the channel. These observations can be accounted for by Ca2+ flux driven through the open InsP3R channel by [Ca2+]ER, raising local [Ca2+]i around the channel to regulate its activity through its cytoplasmic regulatory Ca2+-binding sites. Importantly, [Ca2+]ER regulation of InsP3R channel activity depended on cytoplasmic Ca2+-buffering conditions: it was more pronounced when [Ca2+]i was weakly buffered but completely abolished in strong Ca2+-buffering conditions. With strong cytoplasmic buffering and Ca2+ flux sufficiently reduced by applied voltage, both activation and inhibition of InsP3R channel gating by physiological levels of [Ca2+]ER were completely abolished. Collectively, these results rule out Ca2+ regulation of channel activity by direct binding to the luminal aspect of the channel.

Structure of the inositol 1,4,5-trisphosphate receptor binding core in complex with its ligand

Nature ◽  
2002 ◽  
Vol 420 (6916) ◽  
pp. 696-700 ◽  
Author(s):  
Ivan Bosanac ◽  
Jean-René Alattia ◽  
Tapas K. Mal ◽  
Jenny Chan ◽  
Susanna Talarico ◽  
...  
Keyword(s):  
Receptor Binding ◽  
Inositol 1,4,5 Trisphosphate ◽  
Binding Core ◽  
Trisphosphate Receptor
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