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.

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 Diacylglycerol activates the influx of extracellular cations in T-lymphocytes independently of intracellular calcium-store depletion and possibly involving endogenous TRP6 gene products

2002 ◽  
Vol 364 (1) ◽  
pp. 245-254 ◽  
Author(s):  
Alessandra GAMBERUCCI ◽  
Emanuele GIURISATO ◽  
Paola PIZZO ◽  
Maristella TASSI ◽  
Roberta GIUNTI ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
T Lymphocytes ◽  
Peripheral Blood ◽  
Transient Receptor Potential ◽  
Human Peripheral Blood ◽  
Receptor Potential ◽  
Animal Cells ◽  
Bivalent Cation ◽  
Intracellular Calcium Store ◽  
Transient Receptor

In Jurkat and human peripheral blood T-lymphocytes, 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeant analogue of diacylglycerol, activated the influx of Ca2+, Ba2+ and Sr2+. OAG also caused plasma-membrane depolarization in Ca2+-free media that was recovered by the addition of bivalent cation, indicating the activation of Na+ influx. OAG-induced cation influx was (i) mimicked by the natural dacylglycerol 1-stearoyl-2-arachidonyl-sn-glycerol, (ii) not blocked by inhibiting protein kinase C or in the absence of phopholipase C activity and (iii) blocked by La3+ and Gd3+. Differently from OAG, both thapsigargin and phytohaemagglutinin activated a potent influx of Ca2+, but little influx of Ba2+ and Sr2+. Moreover, the influx of Ca2+ activated by thapsigargin and that activated by OAG were additive. Furthermore, several drugs (i.e. econazole, SKF96365, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, 2-aminoethoxy diphenylborate and calyculin-A), while inhibiting the influx of Ca2+ induced by both thapsigargin and phytohaemagglutinin, did not affect OAG-stimulated cation influx. Transient receptor potential (TRP) 3 and TRP6 proteins have been shown previously to be activated by diacylglycerol when expressed heterologously in animal cells [Hofmann, Obukhov, Schaefer, Harteneck, Gudermann and Schultz (1999) Nature (London) 397, 259–263]. In both Jurkat and peripheral blood T-lymphocytes, mRNA encoding TRP proteins 1, 3, 4 and 6 was detected by reverse transcriptase PCR, and the TRP6 protein was detected by Western blotting in a purified plasma-membrane fraction. We conclude that T-cells express a diacylglycerol-activated cation channel, unrelated to the channel involved in capacitative Ca2+ entry, and associated with the expression of TRP6 protein.

scholarly journals Capacitative Ca2+ entry in agonist-induced pulmonary vasoconstriction

2001 ◽  
Vol 280 (5) ◽  
pp. L870-L880 ◽  
Author(s):  
Sharon S. McDaniel ◽  
Oleksandr Platoshyn ◽  
Jian Wang ◽  
Ying Yu ◽  
Michele Sweeney ◽  
...  
Keyword(s):  
Transient Receptor Potential ◽  
Channel Blocker ◽  
Receptor Potential ◽  
Rt Pcr ◽  
Pulmonary Vasoconstriction ◽  
Store Depletion ◽  
Intracellular Ca ◽  
Gene Transcripts ◽  
Transient Receptor ◽  
Sustained Increase

Agonist-induced increases in cytosolic Ca2+ concentration ([Ca2+]cyt) in pulmonary artery (PA) smooth muscle cells (SMCs) consist of a transient Ca2+ release from intracellular stores followed by a sustained Ca2+ influx. Depletion of intracellular Ca2+ stores triggers capacitative Ca2+ entry (CCE), which contributes to the sustained increase in [Ca2+]cyt and the refilling of Ca2+ into the stores. In isolated PAs superfused with Ca2+-free solution, phenylephrine induced a transient contraction, apparently by a rise in [Ca2+]cyt due to Ca2+ release from the intracellular stores. The transient contraction lasted for 3–4 min until the Ca2+ store was depleted. Restoration of extracellular Ca2+ in the presence of phentolamine produced a contraction potentially due to a rise in [Ca2+]cyt via CCE. The store-operated Ca2+ channel blocker Ni2+ reduced the store depletion-activated Ca2+ currents, decreased CCE, and inhibited the CCE-mediated contraction. In single PASMCs, we identified, using RT-PCR, five transient receptor potential gene transcripts. These results suggest that CCE, potentially through transient receptor potential-encoded Ca2+ channels, plays an important role in agonist-mediated PA contraction.

scholarly journals Pregnancy-enhanced store-operated Ca2+ channel function in uterine artery endothelial cells is associated with enhanced agonist-specific transient receptor potential channel 3-inositol 1,4,5-trisphosphate receptor 2 interaction

2006 ◽  
Vol 190 (2) ◽  
pp. 385-395 ◽  
Author(s):  
Shannon M Gifford ◽  
Fu-Xian Yi ◽  
Ian M Bird
Keyword(s):  
Endothelial Cells ◽  
Uterine Artery ◽  
Transient Receptor Potential ◽  
Purinergic Receptor ◽  
Receptor Potential ◽  
Cell Types ◽  
Transient Receptor Potential Channels ◽  
Significant Difference ◽  
Transient Receptor ◽  
Trisphosphate Receptor

We have previously shown that endothelial cells (EC) derived from the uterine artery (UA) of both pregnant (P-UAEC) and nonpregnant (NP-UAEC) ewes show a biphasic intracellular free Ca2+ ([Ca2+]i) response after ATP stimulation. In each case, the initial transient peak, caused by the release of Ca2+ from the intracellular Ca2+ stores, is mediated by purinergic receptor-Y2 and is very similar in both cell types. However, the sustained phase in particular, caused by the influx of extracellular Ca2+, is heightened in the P-UAEC, and associates with an increased ability of the cells to demonstrate enhanced capacitative Ca2+ entry (CCE) via store-operated channels (SOCs). Herein we demonstrated that the difference in the sustained [Ca2+]i response is maintained for at least 30 min. When 2-aminoethoxydiphenyl borate (2APB) (an inhibitor of the inosital 1,4,5-trisphosphate receptor (IP3R) and possibly SOC) was used in conjunction with ATP, it was capable of completely inhibiting CCE. Since 2APB can inhibit SOC in some cell types and 2APB was capable of inhibiting CCE in the UAEC model, the role of SOC in CCE was first evaluated using the classical inhibitor La3+. The ATP-induced sustained phase was inhibited by 10 μM La3+, implying a role for SOC in the [Ca2+]i response. Since canonical transient receptor potential channels (TRPCs) have recently been identified as putative SOCs in many cell types, including EC, the expression levels of several isoforms were evaluated in UAEC. Expression of TRPC3 and TRPC6 channels in particular was detected, but no significant difference in expression level was found between NP- and P-UAEC. Nonetheless, we were able to show that IP3R2 interacts with TRPC3 in UAEC, forming a protein complex, and that this interaction is considerably enhanced in an agonist sensitive manner by pregnancy. Thus, while IP3R and TRPC isoforms are not altered in their expression by pregnancy, enhanced functional interaction of TRPC3 with IP3R2 may underlie pregnancy-enhanced CCE in the UAEC model and so explain the prolonged [Ca2+]i sustained phase seen in response to ATP.

scholarly journals Receptor-Operated Osteoclast Calcium Sensing*

Endocrinology ◽  
2001 ◽  
Vol 142 (5) ◽  
pp. 1968-1974 ◽  
Author(s):  
Brian D. Bennett ◽  
Ulises Alvarez ◽  
Keith A. Hruska
Keyword(s):  
Transient Receptor Potential ◽  
Calcium Influx ◽  
Receptor Potential ◽  
Transient Receptor Potential Channels ◽  
Independent Manner ◽  
Calcium Sensing ◽  
Store Depletion ◽  
Potential Channels ◽  
Transient Receptor ◽  
Channel Type

Abstract Osteoclasts “sense” elevated extracellular calcium, which leads to cytoskeletal changes that may be linked to phospholipase C (PLC) activation and the associated rise in intracellular calcium ([Ca2+]i). Since PLC is linked to transient receptor potential channels (trp), we hypothesized that receptor activated calcium influx due to this channel type would be activated by osteoclasts sensing [Ca2+]e. We found that high [Ca2+]e induced similar intracellular Ca2+ rises in chicken osteoclasts with or without intracellular Ca2+ store depletion by either TPEN or thapsigargin, thus defining store-insensitive Ca2+ influx. This store-insensitive calcium sensing component was blocked by the PLC antagonist U73122. Also, the calcium channel inhibitor SKF 96365, a blocker of store-independent trp-like channels, was effective in inhibiting calcium sensing in the presence of thapsigargin. Thus, a store-independent component of calcium sensing was associated with ion channels linked to PLC. Since receptor activated transient receptor potential (trp) family cation channels open in a PLC-dependent and store-independent manner, we suggest that receptor operated channels are activated in osteoclasts stimulated by high extracellular Ca2+.

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