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)

Odorant stimulation leads to a depolarization of olfactory receptor neurons. A mechanism underlying this transduction, which occurs in the sensory cilia, involves a G-protein-mediated increase in adenylyl cyclase activity, and therefore a rise in internal cyclic AMP and consequent opening of a cAMP-gated cation channel on the plasma membrane. Another mechanism, not as well established, involves the opening of an inositol trisphosphate-activated cation channel on the plasma membrane as a result of phospholipase C activity. In both cases, an influx of cations is thought to generate the depolarizing receptor potential. We now report, however, that the mechanism is actually more complex. The odorant-induced current appears to contain an inward chloride component also, which is triggered by calcium influx through the cation-selective channel. This newly found chloride component can be as large as the cationic component. The co-existence of cationic and chloride components in the odorant response, possibly unique among sensory transduction mechanisms, may serve to reduce variations in the transduction current resulting from changes in external ionic concentrations around the olfactory cilia. Our finding can explain the long-standing puzzle of why removal of most mucosal cations still does not diminish the amplitude of the olfactory receptor cell response.
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PMID:Co-existence of cationic and chloride components in odorant-induced current of vertebrate olfactory receptor cells. 768 13

A central problem in sensory system biology is the identification of the signal transduction pathways used in different sensory modalities. Genetic analysis of transduction mutants provides a means of studying in vivo the contributions of different pathways. This report shows that odorant response in one olfactory organ of Drosophila melanogaster depends on the norpA phospholipase C (EC 3.1.4.3) gene, providing evidence for use of the inositol 1,4,5-trisphosphate (IP3) signal transduction pathway. Since the norpA gene is also essential to phototransduction, this work demonstrates overlap in the genetic and molecular underpinnings of vision and olfaction. Genetic and molecular data also indicate that some olfactory information flows through a pathway which does not depend on norpA.
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PMID:Requirement for a phospholipase C in odor response: overlap between olfaction and vision in Drosophila. 770 38

The limbic system-associated membrane protein (LAMP) is a 64-68 x 10(3) M(r) glycoprotein that is expressed by subsets of neurons that are functionally interconnected. LAMP exhibits characteristics that are indicative of a developmentally significant protein, such as an early and restricted pattern of expression and the ability to mediate specific fiber-target interactions. A potential, selective adhesive mechanism by which LAMP may regulate the formation of specific circuits is investigated in the present experiments. LAMP is readily released from intact membranes by phosphatidyl inositol-specific phospholipase C. Purified, native LAMP, isolated by PI-PLC digestion and immunoaffinity chromatography, is capable of mediating fluorescent Covasphere aggregation via homophilic binding. To test the ability of LAMP to selectively facilitate substrate adhesion and growth of neurons from LAMP-positive, in contrast to LAMP-negative regions of the developing brain, purified LAMP was dotted onto nitrocellulose-coated dishes and test cells plated. Limbic neurons from perirhinal cortex bind specifically to substrate-bound LAMP within 4 hours, forming small cell aggregates with short neuritic processes that continue to grow through a 48 hour period of monitoring. Preincubation of cells with anti-LAMP has a modest effect on cell binding but significantly reduces initiation of process growth. Non-limbic neurons from somatosensory cortex and olfactory bulb fail to bind or extend processes on the LAMP substrate to any significant extent. All cell populations bind equally well and form neurites on poly-D-lysine and laminin. The present results provide direct evidence that LAMP can specifically facilitate interactions with select neurons in the CNS during development. The data support the concept that patterned expression of unique cell adhesion molecules in functionally related regions of the mammalian brain can regulate circuit formation.
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PMID:The limbic system-associated membrane protein (LAMP) selectively mediates interactions with specific central neuron populations. 774 28

The expression of three phosphoinositide-specific phospholipase C (PLC) isotypes in rat olfactory epithelium was investigated using monoclonal antibodies. In intact animals, PLC beta 1 was not expressed in the olfactory epithelium but was found in glands below the epithelium. However, following unilateral olfactory bulbectomy (OBX), PLC beta 1 was expressed in the dentrites of some olfactory receptor neurons, primarily in the endoturbinates on the unoperated side. PLC gamma 1 immunoreactivity was found in the apices of sustentacular cells and in glands below the epithelium. PLC delta 1 immunoreactivity was found in the glands and in the perinuclear region and dendrites of some receptor neurons. Since none of the PLC isotypes studied were expressed in the cilia of receptor neurons, the results suggest that another PLC isotype is likely to be involved in mediating olfactory transduction.
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PMID:Identification of three phospholipase C isotypes expressed in rat olfactory epithelium. 775 99

Conjugated bile acids such as taurocholic acid (TChA) are potent olfactory stimuli for Atlantic salmon (Salmo salar). A plasma membrane rich fraction was derived from salmon olfactory rosettes and used to investigate TChA signal transduction and receptor binding. In the presence of GTP gamma S, TChA caused dose-dependent stimulation of phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown, half maximal at less than 10(-7) M TChA. Stimulation of PIP2 breakdown by TChA required GTP gamma S, was blocked by GDP beta S, and was mimicked by A1F4-, consistent with a G protein requirement. A1F4- and Ca2+ stimulated breakdown of PIP2, but not phosphatidylcholine, arguing against a non-specific lipase activation. Stimulation of PIP2 breakdown by TChA was maximal at low Ca2+ concentration, < or = 10 nM. Conventional binding analysis with 3H-TChA was inconclusive due to a high degree of non-specific binding and to lack of tissue specificity expected for an olfactory receptor. Analysis of odorant amino acid binding indicated possible interaction of TChA with a putative acidic amino acid receptor but no interaction of TChA with a putative neutral amino acid receptor. We conclude that olfactory discrimination between amino acids and bile acids occurs in part at the receptor level while both classes of odors appear to use the same signal transduction mechanism, G protein mediated activation of phosphoinositide specific phospholipase C (PLC).
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PMID:Signal transduction for taurocholic acid in the olfactory system of Atlantic salmon. 788 71

A plasma membrane rich fraction was prepared from olfactory rosettes of Atlantic salmon and used to study binding of L-glutamic acid and activation of phospholipase C (PLC). Glutamate binding was saturable, high affinity, and inhibited by aspartic acid and taurocholate but not by alanine and lysine. Binding of glutamate was potently inhibited by various ligands for rat brain metabotropic glutamate receptors (mGluR) and also by kainate and N-methyl-D-aspartate. Glutamate stimulated phosphatidylinositol 4,5-bisphosphate breakdown consistent with G protein-dependent activation of PLC. Northern blot analyses demonstrated the presence of olfactory rosette RNA that hybridizes with cDNA probes for mGluR1 and mGluR4 under low stringency conditions. The results indicate the salmon olfactory system includes a subtype of the metabotropic glutamate receptor family.
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PMID:A subtype of the metabotropic glutamate receptor family in the olfactory system of Atlantic salmon. 795 44

Olfactory transduction in invertebrates seems to be similar to that in vertebrates. Three signalling systems involving activation of adenylate cyclase, phospholipase C and guanylate cyclase are present. A variety of second messengers, including cAMP, inositol 1,4,5-trisphosphate, diacylglycerol, nitric oxide and Ca2+, have been identified but their target sites and mode of action are not yet fully understood. The central projections of olfactory signals in invertebrates are relatively simple and perhaps more hard-wired than in vertebrates. Information about circuitry and functional mapping in the olfactory pathway is lacking. This is essential for understanding the sensory code and higher olfactory functions. Neurogenetic analysis has provided useful insights into olfaction and olfactory learning.
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PMID:Olfaction in invertebrates. 821 21

L-Amino acids are potent olfactory stimuli for Atlantic salmon. A plasma membrane fraction, previously shown to be rich in amino acid binding sites, was prepared from olfactory rosettes of Atlantic salmon (Salmo salar) and utilized to investigate the role of phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis in olfactory signal transduction. A cocktail of L-amino acids (Ser, Glu, Lys, and Gly) stimulated PIP2 hydrolysis by phospholipase C (PLC) in a dose-dependent manner with half-maximal stimulation when all amino acids were present at approximately 1 microM. Stimulation of PIP2 hydrolysis by amino acids required GTP gamma S, which alone had no effect on PLC activity. Unlike GTP gamma S, AlF4- and Ca2+ stimulated PIP2 breakdown. Preincubation with 1 mM GDP beta S eliminated the effect of amino acids and AlF4- on PIP2 hydrolysis, suggesting the involvement of G protein regulation. The lack of stimulation by GTP gamma S alone suggested that there was negligible exchange of GTP gamma S for GDP in the absence of odorant. There were no significant effects of amino acids on either adenylate cyclase or guanylate cyclase activities in the membrane preparation under these conditions. The effect of the amino acid cocktail was maximal at 1-10 nM free Ca2+. At or above 100 nM free Ca2+, no effect of amino acids on PIP2 hydrolysis was found. However, between 100 nM and 100 microM, Ca2+ directly stimulated PLC activity in a dose-dependent manner. This stimulation by Ca2+ appeared to be G protein independent because it did not require GTP gamma S and was not inhibited by GDP beta S.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Stimulation of Ca(2+)-regulated olfactory phospholipase C by amino acids. 824 Nov 23

Inositol phospholipid-specific phospholipase C (PLC) generates two important second messengers, inositol triphosphate and diacylglycerol. The recently cloned rat PLC beta 4 cDNA is highly homologous to the norpA cDNA of Drosophila melanogaster. We have mapped the PLC beta 4 gene expression in rat brain tissue sections by in situ hybridization. The PLC beta 4 gene is expressed at high abundance in cerebellar Purkinje cells and neurones of the substantia nigra, the median geniculate bodies and the thalamic nuclei. PLC beta 4 transcripts are also detected in the mammillary nuclei, the neocortex, the habenula and the olfactory bulbs. The specific pattern of gene expression we have observed should help to clarify the relationships between the PLC beta 4 and various constituents of second-messenger systems involved in transduction mechanisms triggered by the stimulation of seven transmembrane domain receptors. The strong gene expression in Purkinje cells and retinal neurones suggests that PLC beta 4 may be involved in the pathogenesis of mouse and human neurological diseases characterized by ataxia and retinal degeneration.
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PMID:The rat phospholipase C beta 4 gene is expressed at high abundance in cerebellar Purkinje cells. 854 79

Olfactory stimuli (odorants) are detected and recognized by binding to receptors belonging to the G-protein-coupled receptor superfamily. The binding of odorants to some receptors stimulates the activity of an odorant-sensitive phospholipase C (PLC) thereby generating the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 plays a key role in membrane depolarization by binding to a receptor that is itself a cation channel. The formation of DAG is expected to stimulate the activity of protein kinase C (PKC). PKC, together with G-protein-coupled receptor kinases, mediates signal termination by phosphorylation of odorant receptors and possibly other substrates. This review summarizes recent evidence regarding the role of phosphoinositide-derived second messengers in the molecular events underlying olfactory signaling. In addition, the role of calcium as a "third messenger" that provides a mechanism for interaction between phosphoinositide second messengers and components of the cyclic AMP signaling pathway is also discussed.
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PMID:Phosphoinositide second messengers in olfaction. 882 99


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