Activation of store-mediated calcium entry by secretion-like coupling between the inositol 1,4,5-trisphosphate receptor type II and human transient receptor potential (hTrp1) channels in human platelets

2001 ◽  
Vol 356 (1) ◽  
pp. 191-198 ◽  
Author(s):  
Juan A. ROSADO ◽  
Stewart O. SAGE
Keyword(s):  
Actin Filaments ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Human Platelets ◽  
Type Ii ◽  
Actin Network ◽  
Ip3 Receptors ◽  
Ip3 Receptor ◽  
Inositol 1,4,5 Trisphosphate ◽  
Transient Receptor

Physical coupling between inositol 1,4,5-trisphosphate (IP3) receptors and transient receptor potential (Trp) channels has been demonstrated in both transfected and normal cells as a candidate mechanism for the activation of store-mediated Ca2+ entry (SMCE). We have investigated the properties of the coupling between the type II IP3 receptor and naturally expressed human Trp1 (hTrp1) in human platelets. Treatment with xestospongin C, an inhibitor of IP3 receptor function, abolished SMCE and coupling between the IP3 receptor and hTrp1. The coupling was activated by depletion of the intracellular Ca2+ stores, and was reversed by refilling of the stores. We have also examined the role of actin filaments in the activation and maintenance of the coupling. Stabilization of the cortical actin network with jasplakinolide prevented the coupling, indicating that, as with secretion, the actin filaments at the cell periphery act as a negative clamp which prevents constitutive coupling. In addition, the actin cytoskeleton plays a positive role, since disruption of the actin network inhibited the coupling when the Ca2+ stores were depleted. These results provide strong evidence for the activation of SMCE by a secretion-like coupling mechanism involving a reversible association between IP3 receptors and hTrp1 in normal human cells.

scholarly journals Coupling between inositol 1,4,5-trisphosphate receptors and human transient receptor potential channel 1 when intracellular Ca2+ stores are depleted

2000 ◽  
Vol 350 (3) ◽  
pp. 631-635 ◽  
Author(s):  
Juan A. ROSADO ◽  
Stewart O. SAGE
Keyword(s):  
Transient Receptor Potential ◽  
De Novo ◽  
Receptor Potential ◽  
Transient Receptor Potential Channel ◽  
Human Platelets ◽  
Ip3 Receptors ◽  
Inositol 1,4,5 Trisphosphate ◽  
Normal Human ◽  
Transient Receptor

In the present study we have investigated the role of inositol 1,4,5-trisphosphate (IP3), functional IP3 receptors (IP3Rs) and the human homologue of the Drosophila transient receptor potential (Trp) channel, human Trp1 (hTrp1), in store-mediated Ca2+ entry (SMCE) in human platelets. Inhibition of IP3 recycling using Li+, or the inhibition of IP3Rs using xestospongin C, both resulted in the inhibition of SMCE activation following Ca2+ store depletion using thapsigargin. Co-immunoprecipitation experiments indicated that endogenously expressed hTrp1 couples with IP3R type II, but not types I or III, in platelets with depleted intracellular Ca2+ stores, but not in control, undepleted cells. These results provide strong evidence for the activation of SMCE by conformational coupling involving de novo association between IP3Rs and a plasma membrane channel in normal human cells.

scholarly journals Rapid agonist-evoked coupling of type II Ins(1,4,5)P3 receptor with human transient receptor potential (hTRPC1) channels in human platelets

2003 ◽  
Vol 375 (3) ◽  
pp. 697-704 ◽  
Author(s):  
Sharon L. BROWNLOW ◽  
Stewart O. SAGE
Keyword(s):  
Transient Receptor Potential ◽  
De Novo ◽  
Receptor Potential ◽  
Coupling Model ◽  
Human Platelets ◽  
Type Ii ◽  
Bivalent Cation ◽  
Store Depletion ◽  
Transient Receptor ◽  
Trisphosphate Receptor

Depletion of intracellular Ca2+ stores results in the activation of SMCE (store-mediated Ca2+ entry) in many cells. The mechanism of activation of SMCE is poorly understood. In human platelets, a secretion-like coupling model may be involved. This proposes that store depletion results in trafficking of portions of the endoplasmic reticulum to the plasma membrane, enabling coupling between proteins in the two membranes. In support of this, we have shown that, in human platelets, agonist-evoked Ca2+ store depletion results in de novo and reversible coupling of the InsP3RII [type II inositol (1,4,5)trisphosphate receptor] with the putative Ca2+ entry channel hTRPC1 [human canonical transient receptor potential 1 (protein); Rosado, Brownlow and Sage (2002) J. Biol. Chem. 277, 42157–42163]. A crucial test of the hypothesis that this coupling activates SMCE is that it should occur rapidly enough to account for agonist-evoked Ca2+ entry. In the present study, we have used quenched- and stopped-flow approaches to determine the latencies of thrombin-evoked coupling of InsP3RII with hTRPC1 and of thrombin-evoked bivalent cation entry using Mn2+ quenching of fura 2 fluorescence. Thrombin-evoked Mn2+ entry was detected with a latency of 0.81±0.07 s (S.E.M., n=7) or 1.36±0.09 s (S.E.M., n=7) at a concentration of 1.0 or 0.1 unit/ml respectively. Coupling between InsP3RII and hTRPC1, assessed at 100 ms intervals, was first detected with a latency of 0.9 or 1.4 s after stimulation with thrombin at a concentration of 1.0 or 0.1 unit/ml respectively. These results support the hypothesis that de novo coupling of InsP3RII with hTRPC1 could activate SMCE in human platelets.

scholarly journals Mibefradil alters intracellular calcium concentration by activation of phospholipase C and IP3 receptor function

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Guilherme H. Souza Bomfim ◽  
Erna Mitaishvili ◽  
Talita Ferreira Aguiar ◽  
Rodrigo S. Lacruz
Keyword(s):  
Phospholipase C ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Ip3 Receptor ◽  
Hek 293 ◽  
Cellular Targets ◽  
293 Cells ◽  
Intracellular Ca ◽  
Transient Receptor ◽  
Orai Channels

AbstractMibefradil is a tetralol derivative originally developed as an antagonist of T-type voltage-gated calcium (Ca2+) channels to treat hypertension when used at nanomolar dosage. More recently, its therapeutic application in hypertension has declined and has been instead repurposed as a treatment of cancer cell proliferation and solid tumor growth. Beyond its function as a Cav blocker, the micromolar concentration of mibefradil can stimulate a rise in [Ca2+]cyt although the mechanism is poorly known. The chanzyme TRPM7 (transient receptor potential melastanin 7), the release of intracellular Ca2+ pools, and Ca2+ influx by ORAI channels have been associated with the increase in [Ca2+]cyt triggered by mibefradil. This study aims to investigate the cellular targets and pathways associated with mibefradil’s effect on [Ca2+]cyt. To address these questions, we monitored changes in [Ca2+]cyt in the specialized mouse epithelial cells (LS8 and ALC) and the widely used HEK-293 cells by stimulating these cells with mibefradil (0.1 μM to 100 μM). We show that mibefradil elicits an increase in [Ca2+]cyt at concentrations above 10 μM (IC50 around 50 μM) and a fast Ca2+ increase capacity at 100 μM. We found that inhibiting IP3 receptors, depleting the ER-Ca2+ stores, or blocking phospholipase C (PLC), significantly decreased the capacity of mibefradil to elevate [Ca2+]cyt. Moreover, the transient application of 100 μM mibefradil triggered Ca2+ influx by store-operated Ca2+ entry (SOCE) mediated by the ORAI channels. Our findings reveal that IP3R and PLC are potential new targets of mibefradil offering novel insights into the effects of this drug.

scholarly journals Transient Receptor Potential 1 Regulates Capacitative Ca2+ Entry and Ca2+ Release from Endoplasmic Reticulum in B Lymphocytes✪

2002 ◽  
Vol 195 (6) ◽  
pp. 673-681 ◽  
Author(s):  
Yasuo Mori ◽  
Minoru Wakamori ◽  
Tomoya Miyakawa ◽  
Meredith Hermosura ◽  
Yuji Hara ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
B Lymphocytes ◽  
Transient Receptor Potential ◽  
Lymphocyte Activation ◽  
Receptor Potential ◽  
Functional Coupling ◽  
B Cell Antigen Receptor ◽  
Ip3 Receptor ◽  
Transient Receptor ◽  
Molecular Components

Capacitative Ca2+ entry (CCE) activated by release/depletion of Ca2+ from internal stores represents a major Ca2+ influx mechanism in lymphocytes and other nonexcitable cells. Despite the importance of CCE in antigen-mediated lymphocyte activation, molecular components constituting this mechanism remain elusive. Here we demonstrate that genetic disruption of transient receptor potential (TRP)1 significantly attenuates both Ca2+ release-activated Ca2+ currents and inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ release from endoplasmic reticulum (ER) in DT40 B cells. As a consequence, B cell antigen receptor–mediated Ca2+ oscillations and NF-AT activation are reduced in TRP1-deficient cells. Thus, our results suggest that CCE channels, whose formation involves TRP1 as an important component, modulate IP3 receptor function, thereby enhancing functional coupling between the ER and plasma membrane in transduction of intracellular Ca2+ signaling in B lymphocytes.

scholarly journals Internal Ca2+ release in yeast is triggered by hypertonic shock and mediated by a TRP channel homologue

2002 ◽  
Vol 156 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Valérie Denis ◽  
Martha S. Cyert
Keyword(s):  
Mammalian Cells ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Second Messengers ◽  
Receptor Potential ◽  
Ip3 Receptors ◽  
Intracellular Compartments ◽  
No Signaling ◽  
Transient Receptor

Calcium ions, present inside all eukaryotic cells, are important second messengers in the transduction of biological signals. In mammalian cells, the release of Ca2+ from intracellular compartments is required for signaling and involves the regulated opening of ryanodine and inositol-1,4,5-trisphosphate (IP3) receptors. However, in budding yeast, no signaling pathway has been shown to involve Ca2+ release from internal stores, and no homologues of ryanodine or IP3 receptors exist in the genome. Here we show that hyperosmotic shock provokes a transient increase in cytosolic Ca2+ in vivo. Vacuolar Ca2+, which is the major intracellular Ca2+ store in yeast, is required for this response, whereas extracellular Ca2+ is not. We aimed to identify the channel responsible for this regulated vacuolar Ca2+ release. Here we report that Yvc1p, a vacuolar membrane protein with homology to transient receptor potential (TRP) channels, mediates the hyperosmolarity induced Ca2+ release. After this release, low cytosolic Ca2+ is restored and vacuolar Ca2+ is replenished through the activity of Vcx1p, a Ca2+/H+ exchanger. These studies reveal a novel mechanism of internal Ca2+ release and establish a new function for TRP channels.

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