Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hormones, neurotransmitters, and growth factors give rise to calcium entry via receptor-activated cation channels that are activated downstream of phospholipase C activity. Members of the transient receptor potential channel (TRPC) family have been characterized as molecular substrates mediating receptor-activated cation influx. TRPC channels are assumed to be composed of multiple TRPC proteins. However, the cellular principles governing the assembly of TRPC proteins into homo- or heteromeric ion channels still remain elusive. By pursuing four independent experimental approaches--i.e., subcellular cotrafficking of TRPC subunits, differential functional suppression by dominant-negative subunits, fluorescence resonance energy transfer between labeled TRPC subunits, and coimmunoprecipitation--we investigate the combinatorial rules of TRPC assembly. Our data show that (i) TRPC2 does not interact with any known TRPC protein and (ii) TRPC1 has the ability to form channel complexes together with TRPC4 and TRPC5. (iii) All other TRPCs exclusively assemble into homo- or heterotetramers within the confines of TRPC subfamilies--e.g., TRPC4/5 or TRPC3/6/7. The principles of TRPC channel formation offer the conceptual framework to assess the physiological role of distinct TRPC proteins in living cells.
...
PMID:Subunit composition of mammalian transient receptor potential channels in living cells. 1203 5

TRP proteins, in most cases, provide localized Ca2+ increases for spatially defined signal transduction processes. They are activated by as yet unclear mechanisms, many involving the complex phospholipase C and phosphatidylinositol pathways. In mouse endothelial cells at least seven TRPs are expressed, including TRPC1, TRPC2, TRPC3, TRPC4, TRPC6, TRPV4 and TRPM4. As shown previously, TRPC4 is an indispensable component of agonist-induced Ca2+ entry channels in native endothelial cells which essentially contributes to agonist-induced vessel relaxation and microvascular endothelial permeability, although, it is still open, whether TRPC4 acts as channel-forming subunit and/or essential constituent for channel activation. Utilizing the mouse model is one way to address this question and to provide novel insights for the biological functions of TRPC4. Here we review recent results on heterologously expressed TRPC4 and summarize what is known on the phenotype of the TRPC4-/- mice generated in our laboratory.
...
PMID:TRPC4 and TRPC4-deficient mice. 1510 83

In the present study, we examined the mechanisms through which erythropoietin (Epo) activates the calcium-permeable transient receptor potential protein channel (TRPC)2. Erythroblasts were isolated from the spleens of phenylhydrazine-treated mice, and Epo stimulation resulted in a significant and dose-dependent increase in intracellular calcium concentration ([Ca(2+)](i)). This increase in [Ca(2+)](i) was inhibited by pretreatment with the phospholipase C (PLC) inhibitor U-73122 but not by the inactive analog U-73343, demonstrating the requirement for PLC activity in Epo-modulated Ca(2+) influx in primary erythroid cells. To determine whether PLC is involved in the activation of TRPC2 by Epo, cell models were used to examine this interaction. Single CHO-S cells that expressed transfected Epo receptor (Epo-R) and TRPC2 were identified, and [Ca(2+)](i) was quantitated. Epo-induced Ca(2+) influx through TRPC2 was inhibited by pretreatment with U-73122 or by downregulation of PLCgamma1 by RNA interference. PLC activation results in the production of inositol 1,4,5-trisphosphate (IP(3)), and TRPC2 has IP(3) receptor (IP(3)R) binding sites. To determine whether IP(3)R is involved in Epo-R signaling, TRPC2 mutants were prepared with partial or complete deletions of the COOH-terminal IP(3)R binding domains. In cells expressing TRPC2 IP(3)R binding mutants and Epo-R, no significant increase in [Ca(2+)](i) was observed after Epo stimulation. TRPC2 coassociated with Epo-R, PLCgamma, and IP(3)R, and the association between TRPC2 and IP(3)R was disrupted in these mutants. Our data demonstrate that Epo-R modulates TRPC2 activation through PLCgamma; that interaction of IP(3)R with TRPC2 is required; and that Epo-R, TRPC2, PLCgamma, and IP(3)R interact to form a signaling complex.
...
PMID:Erythropoietin-modulated calcium influx through TRPC2 is mediated by phospholipase Cgamma and IP3R. 1532 38

In order to elucidate the functional role of TRPC genes, in vivo, the targeted inactivation of these genes in mice is an invaluable technique. In this review, we summarize the currently available results on the phenotype of TRPC-deficient mouse lines. The analysis of mice with targeted deletion in three TRPC genes demonstrates that these proteins represent essential constituents of agonist-activated and phospholipase C-dependent Ca2+ entry channels in primary cells. Furthermore, from the deficits observed in these TRPC-deficient mouse lines a striking number of biological functions could already be ascribed to TRPC2, TRPC4, and TRPC6, not only on the cellular level but also for complex organ functions and integrative physiology. Accordingly, TRPC2 proteins are critically involved in pheromone sensing by neurones of the vomeronasal organ and, thereby, in the regulation of sexual and social behavior of mice, TRPC4 proteins are essential determinants of endothelial-dependent regulation of vascular tone, endothelial permeability, and neurotransmitter release from thalamic interneurones, and TRPC6 proteins are supposed to have a fundamental role in the regulation of smooth muscle tone in blood vessels and lung.
...
PMID:Functional role of TRPC proteins in vivo: lessons from TRPC-deficient mouse models. 1533 83

Previous studies on the activation mechanism of canonical transient receptor potential (TRPC) channels have often produced conflicting conclusions. All seven have been shown to be activated by phospholipase C (PLC)-coupled receptors, but TRPC1, TRPC2, TRPC3, TRPC4, TRPC5, and TRPC7 have also been proposed to function as store-operated channels.(1)1Although PLC activation inevitably leads to activation of store-operated channels, in this report when we refer to PLC-activated channels, we mean those channels that are specifically activated by PLC independently of store depletion. In the case of TRPC3, the expression environment and the expression level appear to determine the mode of regulation. Evidence of a close structural relative of TRPC3, TRPC7, has been presented that this channel is activated by receptor activation or by store depletion. On the basis of previous findings for TRPC3, we reasoned that subtle differences in structure or expression conditions might account for the apparent distinct gating mechanisms of TRPC7. To reexamine the mode of activation of TRPC7, we stably and transiently transfected human embryonic kidney (HEK)-293 cells with cDNA encoding for human TRPC7. We examined the ability of a PLC-activating agonist and an intracellular Ca(2+) store-depleting agent to activate these channels. Our findings demonstrate that when transiently expressed in HEK-293 cells, TRPC7 forms channels that are activated by PLC-stimulating agonists, but not by Ca(2+) store depletion. However, when stably expressed in HEK-293 cells, TRPC7 can be activated by either Ca(2+) store depletion or PLC activation. To our knowledge, this is the first demonstration of a channel protein that can be activated by both receptor- and store-operated modes in the same cell. In addition, the results reconcile the apparently conflicting findings of other laboratories regarding TRPC7 regulation.
...
PMID:Canonical transient receptor potential TRPC7 can function as both a receptor- and store-operated channel in HEK-293 cells. 1534 42

The TRPC cation channel family has been implicated in receptor- or phospholipase C (PLC)-mediated Ca2+ entry into animal cells. These channels are present in mammalian sperm and are assigned a role in ZP3-evoked Ca2+ influx that drives acrosome reactions. However, the mechanisms controlling channel activity and coupling Ca2+ entry through these channels to cellular responses are not well understood. A yeast two-hybrid screen was carried out to identify TRPC-interacting proteins that would be candidate regulators or effectors. We identified a novel protein, enkurin, that is expressed at high levels in the testis and vomeronasal organ and at lower levels in selected other tissues. Enkurin interacts with several TRPC proteins (TRPC1, TRPC2, TRPC5, but not TRPC3) and colocalizes with these channels in sperm. Three protein-protein interaction domains were identified in enkurin: a C-terminal region is essential for channel interaction; an IQ motif binds the Ca2+ sensor, calmodulin, in a Ca2+-dependent manner; and a proline-rich N-terminal region contains predicted ligand sequences for SH3 domain proteins, including the SH3 domain of the p85 regulatory subunit of 1-phosphatidylinositol-3-kinase. We suggest that enkurin is an adaptor that functions to localize a Ca2+ sensitive signal transduction machinery in sperm to a Ca2+-permeable ion channel.
...
PMID:Enkurin is a novel calmodulin and TRPC channel binding protein in sperm. 1538 69

AK032317 is the GenBank accession no. of a full-length RIKEN mouse cDNA. It encodes a putative variant of the C3-type TRPC (transient receptor potential channel) that differs from the previously cloned murine TRPC3 cDNA in that it has a 5' extension stemming from inclusion of an additional exon (exon 0). The extended cDNA adds 62 aa to the sequence of the murine TRPC3. Here, we report the cloning of a cDNA encoding the human homologue of this extended TRPC3 having a highly homologous 73-aa N-terminal extension, referred to as hTRPC3a. A query of the GenBank genomic database predicts the existence of a similar gene product also in rats. Transient expression of the longer TRPC3a in human embryonic kidney (HEK) cells showed that it mediates Ca2+ entry in response to stimulation of the Gq-phospholipase C beta pathway, which is similar to that mediated by the shorter hTRPC3. However, after isolation of HEK cells expressing hTRPC3 in stable form, TRPC3a gave rise to Ca2+-entry channels that are not only activated by the Gq-phospholipase C beta pathway (receptor-activated Ca entry) but also by thapsigargin triggered store depletion. In conjunction with findings from our and other laboratories that TRPC1, TRPC2, TRPC4, TRPC5, and TRPC7, can each mediate store-depletion-activated Ca2+ entry in mammalian cells, our findings with hTRC3a support our previous proposal that TRPCs form capacitative Ca-entry channels.
...
PMID:Molecular cloning of TRPC3a, an N-terminally extended, store-operated variant of the human C3 transient receptor potential channel. 1572 70

Available data on transient receptor potential channel (TRPC) protein functions indicate that these proteins represent essential constituents of agonist-activated and phospholipase C-dependent cation entry pathways in primary cells which contribute to the elevation of cytosolic Ca2+. In addition, a striking number of biological functions have already been assigned to the various TRPC proteins, including mechanosensing activity (TRPC1), chemotropic axon guidance (TRPC1 and TRPC3), pheromone sensing and the regulation of sexual and social behaviour (TRPC2), endothelial-dependent regulation of vascular tone, endothelial permeability and neurotransmitter release (TRPC4), axonal growth (TRPC5), modulation of smooth muscle tone in blood vessels and lung and regulation of podocyte structure and function in the kidney (TRPC6). The lack of compounds which specifically block or activate TRPC proteins impairs the analysis of TRPC function in primary cells. We therefore concentrate in this contribution on (i) studies of TRPC-deficient mouse lines, (ii) data obtained by gene-silencing approaches using antisense oligonucleotides or RNA interference, (iii) expression experiments employing dominant negative TRPC constructs, and (iv) recent data correlating mutations of TRPC genes associated with human disease.
...
PMID:Functional role of TRPC proteins in native systems: implications from knockout and knock-down studies. 1597 74

The acrosome reaction, the first step of the fertilization, is induced by calcium influx through Canonical Transient Receptor Potential channels (TRPC). The molecular nature of TRPC involved is still a debated question. In mouse, TRPC2 plays the most important role and is responsible for the calcium plateau. However, TRPC1 and TRPC5 are also localized in the acrosomal crescent of the sperm head and may participate in calcium signaling, especially in TRPC2-deficient mice. Activation of TRPC channels is an unresolved question in germ and somatic cells as well. In particular, in sperm, little is known concerning the molecular events leading to TRPC2 activation. From the discovery of IP3R binding domains on TRPC2, it has been suggested that TRPC channel activation may be due to a conformational coupling between IP3R and TRPC channels. Moreover, recent data demonstrate that junctate, an IP3R associated protein, participates also in the gating of some TRPC. In this study, we demonstrate that junctate is expressed in sperm and co-localizes with the IP3R in the acrosomal crescent of the anterior head of rodent sperm. Consistent with its specific localization, we show by pull-down experiments that junctate interacts with TRPC2 and TRPC5 but not with TRPC1. We focused on the interaction between TRPC2 and junctate, and we show that the N-terminus of junctate interacts with the C-terminus of TRPC2, both in vitro and in a heterologous expression system. We show that junctate binds to TRPC2 independently of the calcium concentration and that the junctate binding site does not overlap with the common IP3R/calmodulin binding sites. TRPC2 gating is downstream phospholipase C activation, which is a key and necessary step during the acrosome reaction. TRPC2 may then be activated directly by diacylglycerol (DAG), as in neurons of the vomeronasal organ. In the present study, we investigated whether DAG could promote the acrosome reaction. We found that 100 microM OAG, a permeant DAG analogue, was unable to trigger the acrosome reaction. Altogether, these results provide a new hypothesis concerning sperm TRPC2 gating: TRPC2 activation may be due to modifications of its interaction with both junctate and IP3R, induced by depletion of calcium from the acrosomal vesicle.
...
PMID:Junctate, an inositol 1,4,5-triphosphate receptor associated protein, is present in rodent sperm and binds TRPC2 and TRPC5 but not TRPC1 channels. 1615 33

The mammalian signal transduction apparatus utilized by vomeronasal sensory neurons (VSNs) in the vomeronasal organ (VNO) has been richly explored, while that of reptiles, and in particular, the stinkpot or musk turtle Sternotherus odoratus, is less understood. Given that the turtle's well-known reproductive and mating behaviors are governed by chemical communication, 247 patch-clamp recordings were made from male and female S. odoratus VSNs to study the chemosignal-activated properties as well as the second-messenger system underlying the receptor potential. Of the total neurons tested, 88 (35%) were responsive to at least one of five complex natural chemicals, some of which demonstrated a degree of sexual dimorphism in response selectivity. Most notably, male VSNs responded to male urine with solely outward currents. Ruthenium Red, an IP3 receptor (IP3R) antagonist, failed to block chemosignal-activated currents, while the phospholipase C (PLC) inhibitor, U73122, abolished the chemosignal-activated current within 2 min, implicating the PLC system in the generation of a receptor potential in the VNO of musk turtles. Dialysis of several second messengers or their analogues failed to elicit currents in the whole-cell patch-clamp configuration, negating a direct gating of the transduction channel by cyclic adenosine monophosphate (cAMP), inositol 1,4,5-trisphosphate (IP3), arachidonic acid (AA), or diacylglycerol (DAG). Reversal potential analysis of chemosignal-evoked currents demonstrated that inward currents reversed at -5.7+/-7.8 mV (mean +/- s.e.m.; N=10), while outward currents reversed at -28.2+/-2.4 mV (N=30). Measurements of conductance changes associated with outward currents indicated that the outward current represents a reduction of a steady state inward current by the closure of an ion channel when the VSN is exposed to a chemical stimulus such as male urine. Chemosignal-activated currents were significantly reduced when a peptide mimicking a domain on canonical transient receptor potential 2 (TRPC2), to which type 3 IP3 receptor (IP3R3) binds, was included in the recording pipette. Collectively these data suggest that there are multiple transduction cascades operational in the VSNs of S. odoratus, one of which may be mediated by a non-selective cation conductance that is not gated by IP3 but may be modulated by the interaction of its receptor with the TRPC2 channel.
...
PMID:Vomeronasal sensory neurons from Sternotherus odoratus (stinkpot/musk turtle) respond to chemosignals via the phospholipase C system. 1665 57


1 2 Next >>

---