scholarly journals Junctate is a key element in calcium entry induced by activation of InsP3 receptors and/or calcium store depletion

2004 ◽  
Vol 166 (4) ◽  
pp. 537-548 ◽  
Author(s):  
Susan Treves ◽  
Clara Franzini-Armstrong ◽  
Luca Moccagatta ◽  
Christophe Arnoult ◽  
Cristiano Grasso ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Intracellular Calcium ◽  
Calcium Binding ◽  
Calcium Release ◽  
Transient Receptor Potential ◽  
Receptor Activation ◽  
Calcium Entry ◽  
Calcium Stores ◽  
Store Depletion ◽  
Insp3 Receptors

In many cell types agonist-receptor activation leads to a rapid and transient release of Ca2+ from intracellular stores via activation of inositol 1,4,5 trisphosphate (InsP3) receptors (InsP3Rs). Stimulated cells activate store- or receptor-operated calcium channels localized in the plasma membrane, allowing entry of extracellular calcium into the cytoplasm, and thus replenishment of intracellular calcium stores. Calcium entry must be finely regulated in order to prevent an excessive intracellular calcium increase. Junctate, an integral calcium binding protein of endo(sarco)plasmic reticulum membrane, (a) induces and/or stabilizes peripheral couplings between the ER and the plasma membrane, and (b) forms a supramolecular complex with the InsP3R and the canonical transient receptor potential protein (TRPC) 3 calcium entry channel. The full-length protein modulates both agonist-induced and store depletion–induced calcium entry, whereas its NH2 terminus affects receptor-activated calcium entry. RNA interference to deplete cells of endogenous junctate, knocked down both agonist-activated calcium release from intracellular stores and calcium entry via TRPC3. These results demonstrate that junctate is a new protein involved in calcium homeostasis in eukaryotic cells.

scholarly journals Elucidation of a TRPC6-TRPC5 Channel Cascade That Restricts Endothelial Cell Movement

2008 ◽  
Vol 19 (8) ◽  
pp. 3203-3211 ◽  
Author(s):  
Pinaki Chaudhuri ◽  
Scott M. Colles ◽  
Manjunatha Bhat ◽  
David R. Van Wagoner ◽  
Lutz Birnbaumer ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Transient Receptor Potential ◽  
Calcium Influx ◽  
Cell Movement ◽  
Receptor Potential ◽  
Receptor Activation ◽  
Calcium Stores ◽  
Trpc Channels ◽  
Transient Receptor

Canonical transient receptor potential (TRPC) channels are opened by classical signal transduction events initiated by receptor activation or depletion of intracellular calcium stores. Here, we report a novel mechanism for opening TRPC channels in which TRPC6 activation initiates a cascade resulting in TRPC5 translocation. When endothelial cells (ECs) are incubated in lysophosphatidylcholine (lysoPC), rapid translocation of TRPC6 initiates calcium influx that results in externalization of TRPC5. Activation of this TRPC6–5 cascade causes a prolonged increase in intracellular calcium concentration ([Ca2+]i) that inhibits EC movement. When TRPC5 is down-regulated with siRNA, the lysoPC-induced rise in [Ca2+]i is shortened and the inhibition of EC migration is lessened. When TRPC6 is down-regulated or EC from TRPC6−/− mice are studied, lysoPC has minimal effect on [Ca2+]i and EC migration. In addition, TRPC5 is not externalized in response to lysoPC, supporting the dependence of TRPC5 translocation on the opening of TRPC6 channels. Activation of this novel TRPC channel cascade by lysoPC, resulting in the inhibition of EC migration, could adversely impact on EC healing in atherosclerotic arteries where lysoPC is abundant.

scholarly journals Air bubble contact with endothelial cells in vitro induces calcium influx and IP3-dependent release of calcium stores

2011 ◽  
Vol 301 (3) ◽  
pp. C679-C686 ◽  
Author(s):  
Peter Sobolewski ◽  
Judith Kandel ◽  
Alexandra L. Klinger ◽  
David M. Eckmann
Keyword(s):  
Endothelial Cells ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Transient Receptor Potential ◽  
Calcium Influx ◽  
Calcium Transient ◽  
Epifluorescence Microscopy ◽  
Transient Receptor Potential Vanilloid ◽  
Calcium Stores ◽  
Air Bubble

Gas embolism is a serious complication of decompression events and clinical procedures, but the mechanism of resulting injury remains unclear. Previous work has demonstrated that contact between air microbubbles and endothelial cells causes a rapid intracellular calcium transient and can lead to cell death. Here we examined the mechanism responsible for the calcium rise. Single air microbubbles (50–150 μm), trapped at the tip of a micropipette, were micromanipulated into contact with individual human umbilical vein endothelial cells (HUVECs) loaded with Fluo-4 (a fluorescent calcium indicator). Changes in intracellular calcium were then recorded via epifluorescence microscopy. First, we confirmed that HUVECs rapidly respond to air bubble contact with a calcium transient. Next, we examined the involvement of extracellular calcium influx by conducting experiments in low calcium buffer, which markedly attenuated the response, or by pretreating cells with stretch-activated channel blockers (gadolinium chloride or ruthenium red), which abolished the response. Finally, we tested the role of intracellular calcium release by pretreating cells with an inositol 1,4,5-trisphosphate (IP3) receptor blocker (xestospongin C) or phospholipase C inhibitor (neomycin sulfate), which eliminated the response in 64% and 67% of cases, respectively. Collectively, our results lead us to conclude that air bubble contact with endothelial cells causes an influx of calcium through a stretch-activated channel, such as a transient receptor potential vanilloid family member, triggering the release of calcium from intracellular stores via the IP3 pathway.

scholarly journals Capacitative calcium entry

2005 ◽  
Vol 169 (3) ◽  
pp. 381-382 ◽  
Author(s):  
James W. Putney
Keyword(s):  
Plasma Membrane ◽  
Calcium Binding ◽  
Cell Biology ◽  
Essential Role ◽  
Calcium Entry ◽  
Calcium Stores ◽  
Capacitative Calcium Entry ◽  
Calcium Store ◽  
Channel Regulation ◽  
Calcium Channel Regulation

A long-standing mystery in the cell biology of calcium channel regulation is the nature of the signal linking intracellular calcium stores to plasma membrane capacitative calcium entry channels. An RNAi-based screen of selected Drosophila genes has revealed that a calcium-binding protein, stromal interaction molecule (STIM), plays an essential role in the activation of these channels and may be the long sought sensor of calcium store content.

scholarly journals Putative capacitative calcium entry channels: expression of Drosophila trp and evidence for the existence of vertebrate homologues

1995 ◽  
Vol 311 (1) ◽  
pp. 41-44 ◽  
Author(s):  
C C Petersen ◽  
M J Berridge ◽  
M F Borgese ◽  
D L Bennett
Keyword(s):  
Intracellular Calcium ◽  
Xenopus Oocytes ◽  
Transient Receptor Potential ◽  
Calcium Entry ◽  
Calcium Stores ◽  
Pcr Cloning ◽  
Capacitative Calcium Entry ◽  
Homologous Proteins ◽  
Major Pathway ◽  
Intracellular Calcium Stores

Capacitative calcium entry is a major pathway through which intracellular calcium stores are refilled after stimulation. It has been suggested that the protein encoded by the transient receptor potential (trp) gene expressed in Drosophila photoreceptors may be homologous with capacitative calcium entry channels. Expression of the trp gene product in Xenopus oocytes led to significant increases in calcium entry only when the intracellular calcium stores were depleted. Previous investigations have found trp to be uniquely expressed in Drosophila photoreceptors, but PCR cloning shows that homologous proteins exist in Calliphora, mouse brain and Xenopus oocytes. It is thus possible that capacitative calcium entry in Xenopus oocytes is mediated by a homologue of trp.

scholarly journals Discrimination of intracellular calcium store subcompartments using TRPV1 (transient receptor potential channel, vanilloid subfamily member 1) release channel activity

2003 ◽  
Vol 371 (2) ◽  
pp. 341-350 ◽  
Author(s):  
Helen TURNER ◽  
Andrea FLEIG ◽  
Alexander STOKES ◽  
Jean-Pierre KINET ◽  
Reinhold PENNER
Keyword(s):  
Intracellular Calcium ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Transient Receptor Potential Channel ◽  
Calcium Stores ◽  
Calcium Store ◽  
Release Channel ◽  
Subfamily Member ◽  
Store Depletion ◽  
Transient Receptor

The store-operated calcium-release-activated calcium current, ICRAC, is a major mechanism for calcium entry into non-excitable cells. ICRAC refills calcium stores and permits sustained calcium signalling. The relationship between inositol 1,4,5-trisphosphate receptor (InsP3R)-containing stores and ICRAC is not understood. A model of global InsP3R store depletion coupling with ICRAC activation may be simplistic, since intracellular stores are heterogeneous in their release and refilling activities. Here we use a ligand-gated calcium channel, TRPV1 (transient receptor potential channel, vanilloid subfamily member 1), as a new tool to probe store heterogeneity and define intracellular calcium compartments in a mast cell line. TRPV1 has activity as an intracellular release channel but does not mediate global calcium store depletion and does not invade a store coupled with ICRAC. Intracellular TRPV1 localizes to a subset of the InsP3R-containing stores. TRPV1 sensitivity functionally subdivides the InsP3-sensitive store, as does heterogeneity in the sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase isoforms responsible for store refilling. These results provide unequivocal evidence that a specific ‘CRAC store’ exists within the InsP3-releasable calcium stores and describe a novel methodology for manipulation of intracellular free calcium.

Store-operated calcium entry and increased endothelial cell permeability

2000 ◽  
Vol 279 (5) ◽  
pp. L815-L824 ◽  
Author(s):  
Natalie Norwood ◽  
Timothy M. Moore ◽  
David A. Dean ◽  
Rakesh Bhattacharjee ◽  
Ming Li ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Calcium Current ◽  
Calcium Release ◽  
Calcium Entry ◽  
Extracellular Calcium ◽  
Cell Permeability ◽  
Calcium Stores ◽  
Store Depletion ◽  
Endothelial Cell Permeability ◽  
Store Operated Calcium Entry

We hypothesized that myosin light chain kinase (MLCK) links calcium release to activation of store-operated calcium entry, which is important for control of the endothelial cell barrier. Acute inhibition of MLCK caused calcium release from inositol trisphosphate-sensitive calcium stores and prevented subsequent activation of store-operated calcium entry by thapsigargin, suggesting that MLCK serves as an important mechanism linking store depletion to activation of membrane calcium channels. Moreover, in voltage-clamped single rat pulmonary artery endothelial cells, thapsigargin activated an inward calcium current that was abolished by MLCK inhibition. F-actin disruption activated a calcium current, and F-actin stabilization eliminated the thapsigargin-induced current. Thapsigargin increased endothelial cell permeability in the presence, but not in the absence, of extracellular calcium, indicating the importance of calcium entry in decreasing barrier function. Although MLCK inhibition prevented thapsigargin from stimulating calcium entry, it did not prevent thapsigargin from increasing permeability. Rather, inhibition of MLCK activity increased permeability that was especially prominent in low extracellular calcium. In conclusion, MLCK links store depletion to activation of a store-operated calcium entry channel. However, inhibition of calcium entry by MLCK is not sufficient to prevent thapsigargin from increasing endothelial cell permeability.

scholarly journals Impaired Calcium Release in Cerebellar Purkinje Neurons Maintained in Culture

2000 ◽  
Vol 115 (3) ◽  
pp. 339-346 ◽  
Author(s):  
Mary D. Womack ◽  
Jeffery W. Walker ◽  
Kamran Khodakhah
Keyword(s):  
Intracellular Calcium ◽  
Purkinje Cells ◽  
Calcium Release ◽  
Brain Slices ◽  
Purkinje Neurons ◽  
Calcium Stores ◽  
Intracellular Calcium Stores ◽  
Insp3 Receptors ◽  
Cerebellar Purkinje Neurons

Cerebellar Purkinje neurons demonstrate a form of synaptic plasticity that, in acutely prepared brain slices, has been shown to require calcium release from the intracellular calcium stores through inositol trisphosphate (InsP3) receptors. Similar studies performed in cultured Purkinje cells, however, find little evidence for the involvement of InsP3 receptors. To address this discrepancy, the properties of InsP3- and caffeine-evoked calcium release in cultured Purkinje cells were directly examined. Photorelease of InsP3 (up to 100 μM) from its photolabile caged analogue produced no change in calcium levels in 70% of cultured Purkinje cells. In the few cells where a calcium increase was detected, the response was very small and slow to peak. In contrast, the same concentration of InsP3 resulted in large and rapidly rising calcium responses in all acutely dissociated Purkinje cells tested. Similar to InsP3, caffeine also had little effect on calcium levels in cultured Purkinje cells, yet evoked large calcium transients in all acutely dissociated Purkinje cells tested. The results demonstrate that calcium release from intracellular calcium stores is severely impaired in Purkinje cells when they are maintained in culture. Our findings suggest that cultured Purkinje cells are an unfaithful experimental model for the study of the role of calcium release in the induction of cerebellar long term depression.

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