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

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

The diffuse chemosensory system (DCS) of the respiratory apparatus is composed of solitary chemosensory cells (SCCs) that resemble taste cells but are not organized in end organs. The discovery of the DCS may open up new approaches to respiratory diseases. However, available data on mammalian SCCs have so far been collected from rodents, the airways of which display some differences from those of large mammals. Here we investigated the presence of the DCS and of SCCs in cows and bulls (Bos taurus), in which the airway cytology is similar to that in humans, focusing our attention on detection in the airways of molecules involved in the transduction cascade of taste [i.e. alpha-gustducin and phospholipase C of the beta2 subtype (PLCbeta2)]. The aim of the research was to extend our understanding of airway chemoreceptors and to compare the organization of the DCS in a large mammal with that in rodents. Using immunocytochemistry for alpha-gustducin, the taste buds of the tongue and arytenoid were visualized. In the trachea and bronchi, alpha-gustducin-immunoreactive SCCs were frequently found. Using immunocytochemistry for PLCbeta2, the staining pattern was generally similar to those seen for alpha-gustducin. Immunoblotting confirmed the expression of alpha-gustducin in the tongue and in all the airway regions tested. The study demonstrated the presence of SCCs in cows and bulls, suggesting that DCSs are present in many mammalian species. The description of areas with a high density of SCCs in bovine bronchi seems to indicate that the view of the DCS as made up of isolated cells totally devoid of ancillary elements is probably an oversimplification.
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PMID:Evidence of solitary chemosensory cells in a large mammal: the diffuse chemosensory system in Bos taurus airways. 1692 2

Airway secretion is maintained by specialized non-ciliated epithelial cells whose phenotype varies with their topographical location. In addition, specialized epithelial cells located in the airway contain the molecular machinery of chemoreceptive elements. Our aim has been to evaluate whether the secretory cells themselves possess a chemoreceptive capability, which requires the simultaneous presence of chemosensory and secretory mechanisms. We performed immunohistochemical analysis with antibodies against the Clara-cell-specific secretory proteins, CC10 and CC26, as secretory markers. As chemoreceptive markers, we employed antibodies against alpha-gustducin and phospholipase C beta 2 (PLCbeta2), two components of the taste transduction pathway. We also attempted to characterize further the secretory cell type by using a marker of chloride secretion, cystic fibrosis transmembrane regulator (CFTR). We found alpha-gustducin localized in non-ciliated cells of the epithelium lining the trachea and bronchioles of adult rats, where it was also co-expressed with CC10 and CC26. Ultrastructural immunohistochemistry revealed alpha-gustducin in the apical cytoplasm of secretory cells, concentrated around and inside the granules. CFTR was also observed in a subpopulation of non-ciliated epithelial cells, co-localized with some alpha-gustducin- and PLCbeta2-immunoreactive cells, at all levels of the airway epithelium. We conclude that non-ciliated epithelial cells of the rat airway express components of distinct signaling mechanisms and suggest that secretory events are driven by a molecular mechanism activated by the binding of luminal substances to G-protein-coupled receptors.
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PMID:Secretory cells of the airway express molecules of the chemoreceptive cascade. 1702 21

Natural sugars and artificial sweeteners are sensed by receptors in taste buds. T2R bitter and T1R sweet taste receptors are coupled through G-proteins, alpha-gustducin and transducin, to activate phospholipase C beta2 and increase intracellular calcium concentration. Intestinal brush cells or solitary chemosensory cells (SCCs) have a structure similar to lingual taste cells and strongly express alpha-gustducin. It has therefore been suggested over the last decade that brush cells may participate in sugar sensing by a mechanism analogous to that in taste buds. We provide here functional evidence for an intestinal sensing system based on lingual taste receptors. Western blotting and immunocytochemistry revealed that all T1R members are expressed in rat jejunum at strategic locations including Paneth cells, SCCs or the apical membrane of enterocytes; T1Rs are colocalized with each other and with alpha-gustducin, transducin or phospholipase C beta2 to different extents. Intestinal glucose absorption consists of two components: one is classical active Na+-glucose cotransport, the other is the diffusive apical GLUT2 pathway. Artificial sweeteners increase glucose absorption in the order acesulfame potassium approximately sucralose > saccharin, in parallel with their ability to increase intracellular calcium concentration. Stimulation occurs within minutes by an increase in apical GLUT2, which correlates with reciprocal regulation of T1R2, T1R3 and alpha-gustducin versus T1R1, transducin and phospholipase C beta2. Our observation that artificial sweeteners are nutritionally active, because they can signal to a functional taste reception system to increase sugar absorption during a meal, has wide implications for nutrient sensing and nutrition in the treatment of obesity and diabetes.
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PMID:Sweet taste receptors in rat small intestine stimulate glucose absorption through apical GLUT2. 1749 45

Bitter, sweet, and umami tastants are detected by G-protein-coupled receptors that signal through a common second-messenger cascade involving gustducin, phospholipase C beta2, and the transient receptor potential M5 (TRPM5) ion channel. The mechanism by which phosphoinositide signaling activates TRPM5 has been studied in heterologous cell types with contradictory results. To resolve this issue and understand the role of TRPM5 in taste signaling, we took advantage of mice in which the TRPM5 promoter drives expression of green fluorescent protein and mice that carry a targeted deletion of the TRPM5 gene to unequivocally identify TRPM5-dependent currents in taste receptor cells. Our results show that brief elevation of intracellular inositol trisphosphate or Ca2+ is sufficient to gate TRPM5-dependent currents in intact taste cells, but only intracellular Ca2+ is able to activate TRPM5-dependent currents in excised patches. Detailed study in excised patches showed that TRPM5 forms a nonselective cation channel that is half-activated by 8 microM Ca2+ and that desensitizes in response to prolonged exposure to intracellular Ca2+. In addition to channels encoded by the TRPM5 gene, we found that taste cells have a second type of Ca2+-activated nonselective cation channel that is less sensitive to intracellular Ca2+. These data constrain proposed models for taste transduction and suggest a link between receptor signaling and membrane potential in taste cells.
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PMID:The transduction channel TRPM5 is gated by intracellular calcium in taste cells. 1752 21

Taste receptor cells (TRCs) are the sensory cells of taste transduction and are organized into taste buds embedded in the epithelium of the tongue, palate, pharynx, and larynx. Several studies have demonstrated that TRCs involved in sweet as well as bitter and umami responses express alpha-gustducin, an alpha-subunit of the G-protein complex. It has been further demonstrated that this typical taste protein is a potent marker of chemosensory cells located in several tissues, including gastric and pancreatic mucosa and the respiratory apparatus. We recently observed that alpha-gustducin and phospholipase C beta 2-immunoreactive cells were colocalized in the airways with cystic fibrosis transmembrane regulator (CFTR) and Clara cell-specific secretory protein of 10 (CC10) and 26 kDa (CC26). This finding suggests that TRCs might themselves express secretory markers. To test this hypothesis, we investigated the expression of CFTR, CC10, and CC26 in rat circumvallate papillae using reverse transcriptase-polymerase chain reaction analysis, immunohistochemistry, and confocal laser microscopy. The results showed that secretory markers such as CFTR, CC10, and CC26 are present in taste cells of rat circumvallate papillae, and their immunoreactivity is expressed, to a different extent, in subsets of taste cells that express alpha-gustducin. The presence of CFTR, CC10, and CC26 in taste bud cells and their coexpression pattern with alpha-gustducin confirms and extends our previous findings in airway epithelium, lending further credence to the notion that chemoreception and secretion may be related processes.
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PMID:Immunohistochemical localization of cystic fibrosis transmembrane regulator and clara cell secretory protein in taste receptor cells of rat circumvallate papillae. 1815 3

The present study demonstrated for the first time the localizations and patterns of expression of key enzymes for steroidogenesis, cytochrome P450 side-chain-cleavage (P450scc), and P450 aromatase in the taste buds of rat circumvallate papillae, using immunoblot analyses and immunohistochemistry. Immunoblot analyses showed that proteins with a molecular weight close to that of rat adrenal cytochrome P450scc and a molecular weight close to that of rat ovary cytochrome P450 aromatase were present in the rat circumvallate papillae. In immunohistochemistry, antibodies against cytochrome P450scc and P450 aromatase yielded the labelings of a subset of taste bud cells. In the double immunolabeling of P450scc and alpha-gustducin or phospholipase C beta2(PLCbeta2), which were considered as markers of a majority of type II cells, P450scc was co-expressed in a subset of alpha-gustducin or PLCbeta2, but did not co-express neural adhesion molecule (NCAM), a marker of major type III cells. Further double immunolabeled studies showed that P450 aromatase was co-expressed in a subset of alpha-gustducin or PLCbeta2, but did not co-express PGP9.5, a marker of a majority of type III cells. The selective localization of cytochrome P450scc and P450 aromatase strongly suggests that estrogen biosynthesis from cholesterol might occur in a subset of type II cells of the rat taste buds. Although the full significance of estrogen in the taste bud function is not yet understand, estrogen appears to be an important regulator of taste transduction, as is the case with ATP (Finger et al., 2005), which further supports the centrality of taste cells in the life of taste buds.
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PMID:Immunohistochemical identification of cells expressing steroidogenic enzymes cytochrome P450scc and P450 aromatase in taste buds of rat circumvallate papillae. 1829 22

The present study employed immunohistochemistry for single-stranded DNA (ssDNA) to detect apoptotic cells in taste buds of the rat circumvallate papilla. Double-labeling of ssDNA and markers for each cell type - phospholipase C beta2 (PLCbeta2) and alpha-gustducin for type II cells, neural cell adhesion molecule (NCAM) for type III cells, and Jacalin for type IV cells - was also performed to reveal which types of cells die by apoptosis. We detected approximately 16.8% and 14.0% of ssDNA-immunoreactive nuclei among PLCbeta2-immunoreactive and alpha-gustducinimmunoreactive cells, respectively, but rarely found ssDNA-immunoreactive cells among NCAM-immunoreactive or Jacalin-labeled cells, indicating that type II cells die by apoptosis. We also applied double labeling of ssDNA and human blood group antigen H (AbH) - which mostly labels type I cells as well as other cell types - and found that approximately 78% of ssDNA-immunoreactive cells were labeled with AbH, indicating that apoptosis also occurs in type I cells. The present results revealed that apoptosis occurs in both type I cells (dark cells) and type II cells (light cells), suggesting that there are two major cell lineages (dark cell and light cell lineages) for the differentiation of taste bud cells. In summury, type IV cells differentiate into dark and light cells and type III cells differentiate to type II cells within the light cell line.
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PMID:Cell-type specific occurrence of apoptosis in taste buds of the rat circumvallate papilla. 1862 94

Taste signal is received in taste buds and transmitted via sensory afferent nerves to the brainstem. Although a signaling pathway involving phospholipase C-beta2 has been shown to transduce taste signals of bitterness, sweetness and umami in taste receptor cells (Type II cells), these taste receptor cells appear to be different from the presynaptic cells (Type III cells) containing afferent synapses associated with nerve processes. To elucidate the neurotransmission system in the taste receptor cells expressing phospholipase C-beta2, we searched for candidate molecules involved in the neurotransmission, and identified synaptophysin. Synaptophysin was expressed in the taste receptor cells expressing phospholipase C-beta2, as well as in the presynaptic cells harboring synaptic structures with taste nerves and containing serotonin. Synaptophysin-immunoreactive signals were not limited to gustducin-positive bitter taste receptor cells, and sweet/umami taste receptor cells were indicated to also express synaptophysin. Expression of synaptophysin was already initiated 6 days after cell division, almost in synchrony with the initiation of phospholipase C-beta2 expression. Synaptophysin-containing cells co-expressed vesicular-associated membrane protein 2, a v-SNARE molecule which is important for exocytosis. In addition, majority of the synaptophysin-expressing cells also expressed cholecystokinin, a neuropeptide expressed in taste buds. These results suggest that the taste receptor cells have a neurotransmission system involving synaptophysin, which occurs alternatively or additionally to a recently shown hemichannel system.
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PMID:Synaptophysin as a probable component of neurotransmission occurring in taste receptor cells. 1925 17

The chemical composition of the luminal content is now accepted to have a profound influence on the performance of chemosensory receptors. Gustatory and intestinal chemoreceptors have in common their expression of molecules involved in taste sensing and signal transduction pathways. The recent finding that enterocytes of the duodenal epithelium are capable of expressing luminal pancreatic amylase suggests that taste cells of the gustatory epithelium might, in the same way, express salivary amylase in the oral cavity. Therefore, we investigated amylase expression in rat circumvallate papillae by using analyses involving immunohistochemistry, Western blot, and reverse transcription with the polymerase chain reaction. In addition, we used double-labeling confocal laser microscopy to compare amylase immunolabeling with that of the following markers: protein gene product 9.5 (PGP 9.5) and chromogranin A (CgA) for endocrine cells, alpha-gustducin and phospholipase C beta 2 (PLC beta 2) as taste-signaling molecules, and cystic fibrosis transmembrane regulator (CFTR) and Clara-cell-specific secretory protein of 10-kDa (CC10) as secretory markers. The results showed that amylase was present in some taste bud cells; its immunoreactivity was observed in subsets of cells that expressed CgA, alpha-gustducin, PLC beta 2, CFTR, or CC10. PGP 9.5 immunoreactivity was never colocalized with amylase. The data suggest that amylase-positive cells constitute an additional subset of taste receptor cells also associated with chemoreceptorial and/or secretory molecules, confirming the occurrence of various pathways in taste buds.
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PMID:Amylase expression in taste receptor cells of rat circumvallate papillae. 1940 14

l-Glutamate elicits the umami taste sensation, now recognized as a fifth distinct taste quality. A characteristic feature of umami taste is its potentiation by 5'-ribonucleotides such as guanosine-5'-monophosphate and inosine 5'-monophosphate, which also elicit the umami taste on their own. Recent data suggest that multiple G protein-coupled receptors contribute to umami taste. This review will focus on events downstream of the umami taste receptors. Ligand binding leads to Gbetagamma activation of phospholipase C beta2, which produces the second messengers inositol trisphosphate and diacylglycerol. Inositol trisphosphate binds to the type III inositol trisphosphate receptor, which causes the release of Ca(2+) from intracellular stores and Ca(2+)-dependent activation of a monovalent-selective cation channel, TRPM5. TRPM5 is believed to depolarize taste cells, which leads to the release of ATP, which activates ionotropic purinergic receptors on gustatory afferent nerve fibers. This model is supported by knockout of the relevant signaling effectors as well as physiologic studies of isolated taste cells. Concomitant with the molecular studies, physiologic studies show that l-glutamate elicits increases in intracellular Ca(2+) in isolated taste cells and that the source of the Ca(2+) is release from intracellular stores. Both Galpha gustducin and Galpha transducin are involved in umami signaling, because the knockout of either subunit compromises responses to umami stimuli. Both alpha-gustducin and alpha-transducin activate phosphodiesterases to decrease intracellular cAMP. The target of cAMP in umami transduction is not known, but membrane-permeant analogs of cAMP antagonize electrophysiologic responses to umami stimuli in isolated taste cells, which suggests that cAMP may have a modulatory role in umami signaling.
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PMID:Umami taste transduction mechanisms. 1957 Dec 14


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