MURC/CAVIN-4 facilitates store-operated calcium entry in neonatal cardiomyocytes.

Intact store-operated calcium entry (SOCE) mechanisms ensure the maintenance of Ca homeostasis in cardiomyocytes while their dysregulation promotes the development of cardiomyopathies. To better understand this calcium handling process in cardiomyocytes, we sought to identify unknown protein partners of stromal interaction molecule 1 (STIM1), a main regulatory protein of SOCE. We identified the muscle-related coiled-coil protein (MURC), also known as Cavin-4, as a candidate and showed that MURC interacts with STIM1 in cardiomyocytes.

GTPase of the Immune-Associated Nucleotide Protein 5 Regulates the Lysosomal Calcium Compartment in T Lymphocytes.

T lymphocytes from rats carrying a recessive mutation in the GTPase of immune-associated protein 5 () gene undergo spontaneous apoptosis. Molecular mechanisms underlying this survival defect are not yet clear. We have shown that T lymphocytes display reduced calcium influx following T cell antigen receptor (TCR) stimulation that was associated with impaired buffering of calcium by mitochondria.

Functional consequences of the over-expression of TRPC6 channels in HEK cells: impact on the homeostasis of zinc.

The canonical transient receptor potential 6 (TRPC6) protein is a non-selective cation channel able to transport essential trace elements like iron (Fe) and zinc (Zn) through the plasma membrane. Its over-expression in HEK-293 cells causes an intracellular accumulation of Zn, indicating that it could be involved in Zn transport. This finding prompted us to better understand the role played by TRPC6 in Zn homeostasis.

STIM1 participates in the contractile rhythmicity of HL-1 cells by moderating T-type Ca(2+) channel activity.

STIM1 plays a crucial role in Ca(2+) homeostasis, particularly in replenishing the intracellular Ca(2+) store following its depletion. In cardiomyocytes, the Ca(2+) content of the sarcoplasmic reticulum must be tightly controlled to sustain contractile activity. The presence of STIM1 in cardiomyocytes suggests that it may play a role in regulating the contraction of cardiomyocytes.

GTPase of the immune-associated nucleotide-binding protein 5 (GIMAP5) regulates calcium influx in T-lymphocytes by promoting mitochondrial calcium accumulation.

Mature T-lymphocytes undergo spontaneous apoptosis in the biobreeding diabetes-prone strain of rats due to the loss of the functional GIMAP5 (GTPase of the immune-associated nucleotide-binding protein 5) protein. The mechanisms underlying the pro-survival function of GIMAP5 in T-cells have not yet been elucidated. We have previously shown that GIMAP5 deficiency in T-cells impairs Ca2+ entry via plasma membrane channels following exposure to thapsigargin or stimulation of the T-cell antigen receptor.

Involvement of phosphoinositide 3-kinase and PTEN protein in mechanism of activation of TRPC6 protein in vascular smooth muscle cells.

TRPC6 is a cation channel in the plasma membrane that plays a role in Ca(2+) entry after the stimulation of a G(q)-protein-coupled or tyrosine-kinase receptor. TRPC6 translocates to the plasma membrane upon stimulation and remains there as long as the stimulus is present. However, the mechanism that regulates the trafficking and activation of TRPC6 are unclear.

The over-expression of TRPC6 channels in HEK-293 cells favours the intracellular accumulation of zinc.

TRPC6 are plasma membrane cation channels. By means of live-cell imaging and spectroscopic methods, we found that HEK cells expressing TRPC6 channels (HEK-TRPC6) are enriched in zinc and sulphur and have a reduced copper content when compared to HEK cells and HEK cells expressing TRPC3 channels (HEK-TRPC3). Hence, HEK-TRPC6 cells have larger pools of mobilizable Zn2+ and are more sensitive to an oxidative stress.

The serine 814 of TRPC6 is phosphorylated under unstimulated conditions.

TRPC are nonselective cation channels involved in calcium entry. Their regulation by phosphorylation has been shown to modulate their routing and activity. TRPC6 activity increases following phosphorylation by Fyn, and is inhibited by protein kinase G and protein kinase C.

Augmented glucose-induced insulin release in mice lacking G(o2), but not G(o1) or G(i) proteins.

Insulin secretion by pancreatic β cells is a complex and highly regulated process. Disruption of this process can lead to diabetes mellitus. One of the various pathways involved in the regulation of insulin secretion is the activation of heterotrimeric G proteins.

Protein kinase C-dependent phosphorylation of transient receptor potential canonical 6 (TRPC6) on serine 448 causes channel inhibition.

TRPC6 is a cation channel in the plasma membrane that plays a role in Ca(2+) entry following the stimulation of a G(q)-protein coupled or tyrosine kinase receptor. A dysregulation of TRPC6 activity causes abnormal proliferation of smooth muscle cells and glomerulosclerosis. In the present study, we investigated the regulation of TRPC6 activity by protein kinase C (PKC).

Gαo represses insulin secretion by reducing vesicular docking in pancreatic beta-cells.

Objective: Pertussis toxin uncoupling-based studies have shown that Gαi and Gαo can inhibit insulin secretion in pancreatic β-cells. Yet it is unclear whether Gαi and Gαo operate through identical mechanisms and how these G-protein-mediated signals inhibit insulin secretion in vivo. Our objective is to examine whether/how Gαo regulates islet development and insulin secretion in β-cells.

TRUSS, TNF-R1, and TRPC ion channels synergistically reverse endoplasmic reticulum Ca2+ storage reduction in response to m1 muscarinic acetylcholine receptor signaling.

Although most signaling responses initiated by tumor necrosis factor-alpha (TNF-alpha) occur in a Ca(2+)-independent fashion, TNF-alpha receptor signaling augments Ca(2+) entry induced by Galpha(q/11) G-protein coupled receptors (GPCRs) in endothelial cells and increases trans-endothelial permeability. The signaling events involved in GPCR-induced Ca(2+) influx have been characterized and involve store-operated Ca(2+) entry facilitated by the Ca(2+) permeable ion channel, transient receptor potential canonical 4 (TRPC4). Little is known about the mechanisms by which TNF-alpha receptor signaling augments GPCR-induced Ca(2+) entry.

Involvement of Rab9 and Rab11 in the intracellular trafficking of TRPC6.

TRPC proteins become involved in Ca2+ entry following the activation of Gq-protein coupled receptors. TRPC6 is inserted into the plasma membrane upon stimulation and remains in the plasma membrane as long as the stimulus is present. However, the mechanism that regulates the trafficking of TRPC6 is unclear.

Caveolae facilitate but are not essential for platelet-activating factor-mediated calcium mobilization and extracellular signal-regulated kinase activation.

Certain proteins, including receptors and signaling molecules, are known to be enriched in caveolae and lipid rafts. Caveolin-1, the major structural protein of caveolae, specifically interacts with many signaling molecules and, thus, caveolae and lipid rafts are often seen as preassembled signaling platforms. A potential binding site for caveolin-1 is present in the platelet-activating factor receptor (PAFR) sequence, and many downstream signaling components of PAFR activation preferentially localize in caveolae.

Insulin promotes the association of heat shock protein 90 with the inositol 1,4,5-trisphosphate receptor to dampen its Ca2+ release activity.

The inositol 1,4,5-trisphosphate receptor (IP(3)R) is a Ca(2+) release channel that plays a pivotal role in regulating intracellular Ca(2+) levels in resting cells. Three isoforms of IP(3)Rs 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.

The self-association of two N-terminal interaction domains plays an important role in the tetramerization of TRPC4.

Transient receptor potential canonical (TRPC) channels function as cation channels. In a previous study, we identified the molecular determinants involved in promoting TRPC subunit assembly. In the present study, we used size-exclusion chromatography assays to show that the N-terminus of TRPC4 can self-associate and form a tetramer in cellulo.

Loss of GIMAP5 (GTPase of immunity-associated nucleotide binding protein 5) impairs calcium signaling in rat T lymphocytes.

The recessive lyp allele, which harbors a defective gimap5 (GTPase of immunity-associated nucleotide binding protein 5) gene, causes spontaneous apoptosis of T lymphocytes in the biobreeding diabetes-prone strain of rats. Mechanisms underlying the pro-survival function of GIMAP5 remain unclear. In this study, we show that gimap5(lyp/lyp) T cells display diminished calcium flux in response to thapsigargin or signaling via the T cell antigen receptor.

Memantine potentiates agonist-induced Ca2+ responses in HEK 293 cells.

Background/aims: The Alzheimer drug memantine (1-amino-3,5-dimethyl-adamantane) blocks the pore channel of the NMDA receptor. Since memantine also blocks the 5-HT(3) receptor, neuronal nicotinic receptor, and voltage-activated Na(+) channels, the purpose of our study was to verify whether memantine could influence other types of channels involved in the regulation of Ca(2+).

Methods: Free intracellular Ca(2+) concentrations in whole cells and in saponin-permeabilized cells were monitored spectrofluorometrically in HEK-293 cells stably expressing TRPC6.

ATP/UTP activate cation-permeable channels with TRPC3/7 properties in rat cardiomyocytes.

Extracellular purines and pyrimidines have major effects on cardiac rhythm and contraction. ATP/UTP are released during various physiopathological conditions, such as ischemia, and despite degradation by ectonucleotidases, their interstitial concentrations can markedly increase, a fact that is clearly associated with arrhythmia. In the present whole cell patch-clamp analysis on ventricular cardiomyocytes isolated from various mammalian species, ATP and UTP elicited a sustained, nonselective cationic current, I(ATP).

RNF24, a new TRPC interacting protein, causes the intracellular retention of TRPC.

TRPCs function as cation channels in non-excitable cells. The N-terminal tails of all TRPCs contain an ankyrin-like repeat domain, one of the most common protein-protein interaction motifs. Using a yeast two-hybrid screening approach, we found that RNF24, a new membrane RING-H2 protein, interacted with the ankyrin-like repeat domain of TRPC6.

Activation of TRPC6 calcium channels by diacylglycerol (DAG)-containing arachidonic acid: a comparative study with DAG-containing docosahexaenoic acid.

We synthesized a diacylglycerol (DAG)-containing arachidonic acid, i.e., 1-stearoyl-2-arachidonyl-sn-glycerol (SAG), and studied its implication in the modulation of canonical transient receptor potential sub-type 6 (TRPC6) channels in stably-transfected HEK-293 cells.

Differential regulation of lipopolysaccharide and Gram-positive bacteria induced cytokine and chemokine production in macrophages by Galpha(i) proteins.

Heterotrimeric G(i) proteins play a role in signalling activated by lipopolysaccharide (LPS), Staphylococcus aureus (SA) and group B streptococci (GBS), leading to production of inflammatory mediators. We hypothesized that genetic deletion of G(i) proteins would alter cytokine and chemokine production induced by LPS, SA and GBS stimulation. LPS-induced, heat-killed SA-induced and heat-killed GBS-induced cytokine and chemokine production in peritoneal macrophages from wild-type (WT), Galpha(i2) (-/-) or Galpha(i1/3) (-/-) mice were investigated.

Intracellular trafficking of TRP channels.

Thirteen years ago, it was suggested that exocytotic insertion of store-operated channels into the plasma membrane lead to increased Ca(2+) entry in non-excitable cells upon G protein-coupled or tyrosine kinase receptor stimulation. Since the discovery of the TRP channel superfamily and their involvement in receptor-induced Ca(2+) entry, many studies have shown that different members of the TRP superfamily translocate into the plasma membrane upon stimulation. While the exact molecular mechanism by which TRP channels insert into the plasma membrane is unknown, TRP-binding proteins have been shown to directly regulate this trafficking.

Differential regulation of lipopolysaccharide and Gram-positive bacteria induced cytokine and chemokine production in splenocytes by Galphai proteins.

Heterotrimeric Gi proteins play a role in lipopolysaccharide (LPS) and Staphylococcus aureus (SA) activated signaling leading to inflammatory mediator production. We hypothesized that genetic deletion of Gi proteins would alter cytokine and chemokine production induced by LPS and SA. LPS- and heat killed SA-induced cytokine and chemokine production in splenocytes from wild type (WT), Galpha(i2) (-/-) or Galpha(i1/3) (-/-) mice were investigated.

Identification of two domains involved in the assembly of transient receptor potential canonical channels.

Transient receptor potential canonical (TRPC) channels are associated with calcium entry activity in nonexcitable cells. TRPCs can form homo- or heterotetrameric channels, in which case they can assemble together within a subfamily groups. TRPC1, 4, and 5 represent one group, and TRPC3, 6, and 7 represent the other.