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)

The GTP-binding proteins involved in signal transduction now constitute a large family of so called 'G proteins'. Among them, Gs and Gi mediate the stimulation and inhibition of adenyl cyclase, respectively. Recently, another G protein (Go) abundant in brain was purified, but its function is still unknown. Like other G proteins, Go is a heterotrimer (alpha, beta, gamma) and the beta-gamma subunits seem to be identical to those of Gs and Gi. The alpha subunit of Go (Go-alpha) has a molecular weight of 39 kDa lower than those of Gi (41 kDa) or Gs (45-52 kDa). A positive immunoreativity with antibodies against Go-alpha was found in peripheral nervous tissues, adrenal medulla, heart, adenohypophysis and adipocytes. Go ressembles Gi in its ability to be ADP-ribosylated by pertussis toxin, and sequence analysis reveals a 68% homology between their alpha subunits. The GTPase activity of Go is several times higher than that of Gi. The affinity of the beta-gamma entity is about 3 times higher for Gi than for Go. In reconstitution studies, Go does not mimic the inhibitory effect of Gi on adenyl cyclase-stimulated by Gs. On the contrary, Go is as efficient as Gi in reconstituting the functional coupling with the muscarinic, alpha 2-adrenergic and chemotactic agent f-Met-Leu-Phe (fMLP), receptors. Recent studies seem to rule out Go as the coupling G protein of phospholipase C, the enzyme involved in phosphatidyl inositol trisphosphate hydrolysis. However, Go remains a putative candidate for transduction mechanisms coupled to a potassium channel or to a voltage-dependent calcium channel.
...
PMID:Go, a major brain GTP binding protein in search of a function: purification, immunological and biochemical characteristics. 311 14

Phospholipase A has been solubilized from the sarcoplasmic reticulum of rat heart by treatment with Tris buffer, potassium chloride, taurodeoxycholate or octyl glucoside. On HPLC gel permeation, two phospholipases were identified at the void volume of a TSK 3000 column and at an apparent molecular mass of 60 kDa. The two activity peaks exhibited a predominance of phospholipase A1 activity (83-91%) and a lesser phospholipase C activity (4-9%) using sonicated 1-palmitoyl-2[1-14C]oleoylphosphatidylcholine liposomes as substrate. The voiding phospholipase A peak, which represented the bulk of the recovered activity, exhibited a requirement for calcium ions in the 0.3-3 microM range. The heat stability and response to mercuric ions was studied and some similarities were noted between the solubilized sarcoplasmic reticulum phospholipases A and the cytosolic phospholipases A of rat heart. It is speculated that the cytosolic phospholipase A which we reported earlier may represent in part phospholipase A released from sarcoplasmic reticulum during isolation of the subcellular membrane fractions.
...
PMID:Solubilization and partial characterization of phospholipase A from rat heart sarcoplasmic reticulum. 316 81

Regulation of aldosterone secretion is complex both in terms of the number of secretagogues that can influence its biosynthesis and the number of second messengers utilized by these secretagogues (Table 1, Figure 1). ACTH primarily acts via the adenylate cyclase system through a stimulatory G protein; however, there is evidence that at low concentration it may also activate calcium influx and phospholipase C in some species. The primary effect of AII is activation of phospholipase C, which increases both calcium release from intracellular stores and calcium flux across the cell membrane and activates protein kinase C. Potassium depolarizes the membrane, thereby activating calcium flow through voltage-dependent calcium channels. It also directly or indirectly causes release of calcium from intracellular binding sites. A small change in cAMP levels may also be involved in the sustained secretory response to potassium. Species variation in the regulation of aldosterone secretion probably exists; the control mechanisms in the human appear to be closer to those in the rat than to those in cow and sheep. How changes in dietary sodium and potassium modify aldosterone secretion and the adrenal's responsiveness to secretagogues remains unclear. Yet these effects may be of considerable importance, both in terms of understanding the overall regulation of aldosterone secretion and in resolving the discrepancies in the results obtained under different experimental conditions.
...
PMID:Regulation of aldosterone secretion. 328 99

Chromaffin cells purified from bovine adrenal medulla and maintained in primary culture were used to study the effects of hyperosmolarity on the nicotine- and high potassium-induced secretory response. A similar study was also performed on cells permeabilized with digitonin and with alpha-toxin from Staphylococcus aureus. Hyperosmolarity does not affect the spontaneous release of catecholamines from either intact cells or permeabilized cells. The nicotine-induced secretion and high potassium-induced secretion from intact cells are inhibited by hypertonic solutions; a 100% inhibition of net release was observed at 660 mOsm (sucrose as osmotic agent). Veratridine- and the cation ionophore X537-A-induced release were both depressed under hyperosmotic conditions. Hyperosmolarity was shown to have reversible effects on the secretory response of intact cells. Finally, hyperosmolarity has intracellular effects on catecholamine release evoked by calcium from both detergent- and alpha-toxin-permeabilized cells. Our data show that hyperosmolarity has multiple effects on the cell membrane and the protein constituents associated with it, but has also a significant effect on intracellular reactions concerned with exocytosis.
...
PMID:Influence of hypertonic solutions on catecholamine release from intact and permeabilized cultured chromaffin cells. 379 Jun 19

The effect of the diglyceride lipase inhibitor RHC 80267 on the prolactin secretory process was examined in clonal anterior pituitary GH3 cells. This compound reduced basal prolactin secretion as well as secretion induced by TRH and phospholipase C but not that induced by phorbol myristate acetate. Although exogenous phospholipase C increased diglyceride, no increase in the products of diglyceride lipase was detected. Moreover, low doses of RHC 80267 were observed to effectively block potassium-stimulated 45calcium influx. It is unlikely that RHC 80267 inhibits prolactin release solely by inhibiting diglyceride lipase. These data suggest blockade of plasma membrane calcium channels as an alternate mechanism for the inhibitory actions of RHC 80267 on intact GH3 cells. These observations may have implications for RHC 80267 action in other cell types.
...
PMID:Effects of RHC 80267, a diglyceride lipase inhibitor, on prolactin secretion and calcium uptake in GH3 pituitary cells. 379 24

Studies in erythrocytes indicate that staphylococcal alpha-toxin generates discrete transmembrane channels with an effective diameter of 2-3 nm. In cultured, confluent, pig pulmonary arterial endothelial cells we studied the triggering of the arachidonic acid cascade and its dependence on calcium influx, possibly through toxin-created pores. In endothelial cells alpha-toxin time dependently (5-30 min) and dose dependently (0.1-8 micrograms/ml) stimulated the release of radiolabeled arachidonic acid and prostacyclin (PGI2) production in similar amounts as the calcium ionophore A23187 (10 microM). Preincubation of alpha-toxin with neutralizing antibodies abolished the effect. The toxin response was strictly dose dependent on extracellular calcium but not on magnesium. The toxin effect was accompanied by an up to 10-fold increased passive permeability of pulmonary arterial endothelial cells for 45Ca. Interference with calcium-calmodulin function (trifluoperazine, W7) dose dependently reduced production of PGI2, but blockers of physiological calcium channels (verapamil, nimodipine, nisoldipine, and diltiazem) did not. In contrast to the effect of the ionophore A23187, the toxin effect was accompanied by a release of potassium, but in neither system was there a release of lactate dehydrogenase. In addition, alpha-toxin but not ionophore-exposed endothelial cells showed an increased passive influx of small radiolabeled markers (45Ca and [3H]sucrose) but not of large markers [( 3H]inulin and [3H]dextran). These data are consistent with the concept that alpha-toxin triggers the arachidonic acid cascade in pulmonary arterial endothelial cells by calcium influx and suggest that this calcium influx may proceed through toxin-created transmembrane channels.
...
PMID:Staphylococcal alpha-toxin-induced PGI2 production in endothelial cells: role of calcium. 391 12

It is now established that a key step in the action of calcium-mobilizing agonists is stimulation of the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) to 1,2-diacylglycerol and inositol 1,4,5-trisphosphate (InsP3). The latter substance acts as a second messenger, controlling the release of calcium from intracellular stores (see ref. 3 for review). The bifurcating nature of the signalling system is exemplified by the fact that the other product of PtdIns(4,5)P2 hydrolysis, 1,2-diacylglycerol, can alter cellular function by activating protein kinase C, the cellular target for several tumour-promoting agents such as the phorbol esters. In various tissues, including GH3 pituitary tumour cells, a synergistic interaction between calcium ions and protein kinase C underlies agonist-induced changes in cell activity. The data presented here suggest that when GH3 cells are stimulated by thyrotropin-releasing hormone (TRH), an agonist inducing PtdIns(4,5)P2 hydrolysis, the two limbs of the inositol lipid signalling system interact to control free cytosolic calcium levels [( Ca2+]i). At low levels of TRH receptor occupancy, [Ca2+]i increases rapidly, then declines relatively slowly. As receptor occupancy increases, the calcium signal becomes more short-lived due to the appearance of a second, inhibitory, component. This latter component, which is enhanced when [Ca2+]i is elevated by high potassium depolarization, is mimicked by active phorbol esters and by bacterial phospholipase C. It seems likely that protein kinase C subserves a negative feedback role in agonist-induced calcium mobilization.
...
PMID:Bidirectional control of cytosolic free calcium by thyrotropin-releasing hormone in pituitary cells. 392 49

Binding of acetylcholine in the concentration range 1 nM-1 muM was measured by equilibrium dialysis to a particulate preparation of Torpedo electroplax, without or with prior treatment of the tissue with one of three chemical modifying reagents. Significant reduction in binding of acetylcholine resulted after treatment with 1,4-dithiothreitol, p-chloromercuribenzoate, or p-(trimethylammonium)-benzenediazonium fluoroborate. Partial reversal of the reduction in binding occurred when dialysis was performed in the presence of 5,5'-dithiobis-(2-nitrobenzoic acid) or potassium ferricyanide (in the case of treatment with dithiothreitol), and 2-mercaptoethanol (in the case of treatment with p-chloromercuribenzoate). It is concluded that the functional acetylcholine-receptor macromolecule of Torpedo electroplax has disulfide bond(s), sulfhydryl group(s), and one or more of the amino acids vulnerable to diazotization by p-(trimethylammonium)-benzenediazonium fluoroborate. This, plus the effect of phospholipase C (EC 3.1.4.3) in elimination of detectable binding of acetylcholine after electrofocusing, is additional evidence that the functional acetylcholine receptor is a phospholipoprotein or a phospholipid-protein complex, which has a low isoelectric point of 4.5 +/- 0.2, yet is denatured by exposure to low pH for 24 hr. Due to this adverse effect, recovery of binding of acetylcholine after electrofocusing, as detected by equilibrium dialysis or ultrafiltration, is only 23% and, so far, only 6.3-fold purification of functional acetylcholine receptors by this technique is possible. Three or two forms of acetylcholinesterase (EC 3.1.1.7), whose peaks have isoelectric points ranging from 4.3 to 7.2, appear after electrofocusing of Torpedo extracted with 1% Triton X-100 or Lubrol, respectively. The major peak in either preparation has an isoelectric point of 5. Although the peaks of the functional acetylcholine receptors and of acetylcholinesterase of Torpedo electroplax are separable by electrofocusing, it has not been possible to isolate fractions that contain functional receptors but that are free of acetylcholinesterase. The opposite is possible.
...
PMID:Characterization and partial purification of the acetylcholine receptor from Torpedo electroplax. 450 55

Phenylmethanesulfonyl fluoride (PMSF) (2 mM), a putative inhibitor of phosphatidylinositol-specific phospholipase C, almost completely inhibited carbachol-stimulated inositol incorporation into phosphatidylinositol (PI) of longitudinal smooth muscle of guinea pig ileum, while it had no effect on potassium-stimulated inositol incorporation. This suggests that the two stimuli may affect phosphoinositide turnover by different mechanisms, distinguishable by PMSF. In contrast to its specific inhibition of carbachol-stimulated phosphoinositide turnover, PMSF produced a transient inhibition of contraction by both carbachol and potassium. The non-selective effect of PMSF on contraction suggests that it is not the result of its inhibitory effect on phosphoinositide breakdown. PMSF (2 mM) inhibited carbachol-stimulated inositol phosphate accumulation in the presence of Li+ by only 15%-19%, indicating that PMSF inhibition of phosphoinositide turnover was not due to its inhibition of phosphoinositide phosphodiesterase, but to one or more steps following phosphoinositide breakdown.
...
PMID:Differential effects of phenylmethanesulfonyl fluoride (PMSF) on carbachol and potassium stimulated phosphoinositide turnover and contraction in longitudinal smooth muscle of guinea pig ileum. 609 26

Bovine leukaemia virus (BLV) was found to agglutinate mouse erythrocytes. Under optimal conditions, including the use of neuraminidase-treated erythrocytes, 200 microgram/ml of BLV purified from the supernatant fluid of BLV-infected bat cells had haemagglutinating titres of about 512 units. BLV haemagglutination was drastically affected by pH and temperature; maximum agglutination occurred at pH 6 and 4 degrees C. That the BLV haemagglutinin is a glycoprotein was suggested by the fact that trypsin, potassium periodate or neuraminidase, but not lipid solvents or phospholipase C, significantly reduced the haemagglutinating (HA) activity of purified BLV. Furthermore, purified BLV glycoprotein of mol. wt. 51 000 (gp51) had HA activity. The receptors for BLV on mouse erythrocytes were inactivated by proteolytic enzymes but not by sodium deoxycholate or potassium periodate. Neuraminidase treatment of erythrocytes increase their agglutinability fourfold. Haemagglutination is a relatively sensitive test for detecting BLV glycoprotein because 0.4 microgram/ml of glycoprotein can be detected by this method. The pH and temperature sensitivity of the BLV HA reaction and specificity for mouse erythrocytes distinguish BLV from that of equine infectious anaemia virus and murine leukaemia virus, the other C type retroviruses known to have HA activity.
...
PMID:Haemagglutination by bovine leukaemia virus. 627 77


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---