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:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined changes in cAMP and inositol phosphate metabolism to assess the contribution of the guanine nucleotide regulatory (G) protein(s) regulating adenylate cyclase and phospholipase C in mediating the stimulatory effects of GppNHp on PTH release from permeabilized bovine parathyroid cells. To examine the role of Gs, the G protein stimulating adenylate cyclase, and cAMP on PTH release, permeabilized cells were incubated with either GppNHp or isoproterenol, and the effects of these agents on PTH release and cellular cAMP content were determined by RIA. To study the effects of GppNHp on inositol phosphate accumulation, permeabilized cells prelabeled with [3H]inositol were exposed to GppNHp, and inositol phosphates were measured using ion-exchange chromatography. These studies revealed that isoproterenol produced a dose-dependent increment in cAMP content in permeabilized cells with no significant effect on PTH release. Conversely, GppNHp rapidly and markedly elevated PTH release with a smaller and delayed rise in cAMP content. GppNHp- also promoted a dose-dependent increase in inositol monophosphate (IP), inositol bisphosphate (IP2), and inositol trisphosphate (IP3) accumulation, suggesting activation of phosphoinositide hydrolysis. Addition of dioctanoylglycerol, however, a synthetic diacylglycerol (DG) that activates protein kinase C, produced a much smaller increment in PTH release than GppNHp. Moreover, reducing the free calcium concentration to less than 10(-9) M by adding 10 mM EGTA to the permeabilization medium dissociated the effects of GppNHp and DG on secretion, increasing GppNHp-stimulated PTH release while reducing PTH secretion evoked by DG.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Mechanisms underlying the stimulation of PTH release by GppNHp in permeabilized bovine parathyroid cells. 216 60

Recent studies have shown that, in addition to its well-known action to stimulate adenylate cyclase activity, parathyroid hormone (PTH) may stimulate the inositol phosphate second messenger system in its target tissues, bone and kidney. We have developed a membrane preparation of canine renal cortex to test this hypothesis. We also have examined the potential role of guanine nucleotides on the formation of inositol phosphates (IPs) in this tissue. Collagenase-dispersed tubules were labeled with [3H]inositol, and membranes containing labeled phospholipase C (PLC) substrates ([3H]phosphatidyl inositol, [3H]phosphatidylinositol monophosphate, and [3H]phosphatidylinositol bisphosphate) were prepared. bPTH-(1-34) (100 nM) rapidly increased levels of all measured [3H]IPs (IP1, IP2, and IP3) 1.6-1.7-fold within the first 30 s of stimulation. The half-maximal concentration for the response to bPTH-(1-34) was approximately 8 nM. GTP gamma S (100 microM), a nonhydrolyzable analog of GTP, also increased levels of the three [3H]IPs (1.8 to 2.8-fold). The half-maximal concentration for the response to GTP gamma S was approximately 30 microM. In the presence of GTP gamma S, bPTH-(1-34) increased levels of IPs by up to 2.7 times more than GTP gamma S alone. The results indicate that bPTH-(1-34) can stimulate the formation of inositol phosphates in the kidney and suggest that PTH may activate a receptor coupled to this effect through a guanine nucleotide regulatory protein.
...
PMID:Parathyroid hormone stimulates formation of inositol phosphates in a membrane preparation of canine renal cortical tubular cells. 218 14

Carbachol (CCh)-stimulated hydrolysis of inositol lipids in human neuroblastoma SH-SY5Y cells was systematically characterized in parallel with the carbachol effects on cAMP formation. Carbachol concentration-dependently induced the hydrolysis of inositol lipids and formation of [3H]IP3, [3H]IP2 and [3H]IP1 in these cells labeled with [3H]inositol. The maximal amount of [3H]IP1 accumulated in the presence of 10 mM LiCl was about 50-fold above the basal level. The EC50 value of CCh was 14 microM. The muscarinic antagonists atropine, pirenzepine and 11-[[2-(diethylamino)methyl]-1-piperidinyl]acetyl]-5,11-dihydro- 6H-pyrido [2,3-b] (1,4)-benzodiazepine-6-one (AF-DX 116) competitively inhibited CCh-induced [3H]IP1 accumulation. The functional inhibition constants (converted from the pA2 values) were 0.24, 8.1 and 470 nM, respectively. These values are in good agreement with the inhibition constants of these drugs from antagonist/[3H]pirenzepine studies using intact cells. Forskolin, adenosine and PGE1 stimulated cAMP formation in this cell line. Morphine decreased PGE1-induced cAMP formation as well as the basal cAMP formation. However, CCh did not stimulate or inhibit the basal cAMP formation. Also, CCh did not have any effects on the adenosine and PGE1-induced cAMP formation in these cells. These data suggest that muscarinic M1 receptors are coupled to the hydrolysis of inositol lipids and not to the adenylate cyclase system in human neuroblastoma SH-SY5Y cells.
...
PMID:The coupling of muscarinic receptors to hydrolysis of inositol lipids in human neuroblastoma SH-SY5Y cells. 255 26

In previous studies, we showed that cardiac muscarinic receptors (M2) are composed of two subgroups, M2 alpha and M2 beta, with different affinities for agonists and that the M2 alpha subgroup is coupled with inhibition of adenylate cyclase. We now studied which subgroup was responsible for the formation of inositol mono- (IP), bis- (IP2), tris- (IP3) and tetrakis- (IP4) phosphates in guinea pig heart. Carbachol (1 mM) significantly stimulated the formation of all four IPs in [3H]myoinositol-preloaded slices of guinea-pig ventricles. Acetylcholine (1 mM) also stimulated the formation of IP2, IP3 and IP4. However, oxotremorine (1 mM) only slightly stimulated the formation of IP2, and pilocarpine did not stimulate the formation of any IP. The pED50 values of carbachol for IP2 and IP3 formation were 3.76 and 4.23, respectively, which coincided with the pKd values of the low-affinity agonist binding site (L site) measured by competition of carbachol with [3H]quinuclidinyl benzilate [( 3H]QNB) binding while the pKd value for inhibition of adenylate cyclase coincided with the pKd value of the high-affinity agonist binding site (H site). Treatment of animals with pertussis toxin decreased the formation of IP2 and IP3 by carbachol to 66 and 54%, respectively, but resulted in complete inhibition of adenylate cyclase. These results suggested that muscarinic stimulation of the formation of IPs was manifested through a different receptor subgroup (M2 beta) and GTP binding protein different from those for inhibition of adenylate cyclase.
...
PMID:The H-L subgroup of guinea-pig cardiac M2 receptors (M2 beta) regulates inositol phosphate formation. 258 43

In addition to stimulation of cyclic AMP, parathyroid hormone (PTH) may influence cellular events by utilizing other pathways of hormone action, such as the generation of inositol phosphates (IPs). We sought to examine this potential action of PTH by assessing the formation of inositol phosphates in PTH-sensitive ROS 17/2.8 cells. The polyphosphoinositides were labeled by growing the cells with [3H]inositol following which cell homogenates were prepared. The nonhydrolyzable guanine nucleotide, GTP gamma S, and calcium ion, alone and together, stimulated all three IPs, IP1, IP2, and IP3. IP1 formation was linear over 30 minutes but IP2 and IP3 accumulated more rapidly peaking by 5 minutes for all agonist conditions. The proportion of total P as IP3 was enhanced when the cells were grown with retinoic acid (1 microM) or when the assay was conducted at pH 4.5. In addition, the lower pH was associated with much more enzyme activity. PTH agonists, bPTH-(1-84) and bPTH-(1-34), both caused a small but significant stimulation of IP3 formation. When bPTH-(1-84), and the analog bPTH-(3-34)amide, that inhibits PTH-mediated adenylate cyclase activity were present together, there was additive stimulation of IP3 formation compared with that with either agent alone. The results demonstrate that inositol phosphate formation can be stimulated directly in a membrane preparation of ROS cells by GTP gamma S, calcium ion, and PTH and that the enzyme mediating this activity, phospholipase C, is regulated by a guanine nucleotide binding protein.
...
PMID:Stimulation of inositol phosphate formation in ROS 17/2.8 cell membranes by guanine nucleotide, calcium, and parathyroid hormone. 276 77

In human thyroid slices prelabeled with myo-[2-3H]inositol, thyrotropin (TSH, 3-30 mU/ml) stimulated IP3, IP2 and IP1 generation over a prolonged time course. The cAMP response was much more sensitive to TSH, peaking between 1 and 5 mU/ml. Forskolin (10(-5) M) and isoproterenol had no effect on basal IP levels, while carbamylcholine (10(-5) M, 10(-4) M) also increased IP accumulation. These data suggest that in the human thyroid, TSH activates a phospholipase C generating IP3 and diacylglycerol independently of the well-known adenylate cyclase stimulation. They validate in the human model a dual mode of action of the hormone previously proposed on the basis of indirect observations.
...
PMID:Dual activation by thyrotropin of the phospholipase C and cyclic AMP cascades in human thyroid. 282 Aug 16

Many hormones elicit effects on target cells by stimulating the enzyme phospholipase-C, which catalyzes the hydrolysis of phosphoinositides to the intracellular second messengers diacylglycerol and inositol phosphates. The present study examined the roles of FSH and guanine nucleotide-binding proteins (G-proteins) in regulating the hydrolysis of phosphoinositides in Sertoli cells. Sertoli cell cultures prepared from 16- to 18-day-old rats were incubated for 24 h with myo-[2-3H] inositol to label endogenous phospholipids. Treatment of cells from 0.5-20 min with preparations of ovine FSH ranging in potency from 1-60 times that of NIH FSH S1 did not affect accumulation of inositol phosphates. Levels of total [3H]inositol phosphates [[3H]inositol mono-, di-, and triphosphates (IP, IP2, and IP3)] in FSH-treated cultures was 75-120% the levels in control cultures over the various time intervals studied. Addition of testosterone and the combination of testosterone plus retinoic acid, agents that have been shown to potentiate effects of FSH in other systems, did not affect accumulation of inositol phosphates in response to FSH. In contrast to the lack of effect on accumulation of inositol phosphates, FSH stimulated 4- to 11-fold increases in estradiol secretion over 24 h of culture, indicating that Sertoli cells were viable and responsive to FSH. AIF4- has been shown to activate G-proteins involved in regulation of adenylate cyclase activity. In the present study, AIF4- induced 4- to 5-fold increases in IP, IP2, and IP3 in experiments wherein FSH had no effect. Pretreatment of Sertoli cells with pertussis toxin (100 and 1000 ng/ml) for 24 h inhibited fluoride-induced generation of IP, IP2, and IP3 by 24-51%. Similar treatment with cholera toxin had no effect on basal or fluoride-induced generation of IP2 or IP3, but increased fluoride-induced generation of IP by 20-34%. These results suggest that phospholipase-C activity in Sertoli cells is modulated by a pertussis toxin-sensitive G-protein(s), but does not appear to be affected by FSH.
...
PMID:Regulation of the phosphoinositide pathway in cultured Sertoli cells from immature rats: effects of follicle-stimulating hormone and fluoride. 313 93

When myo-2-[3H]inositol-labeled rabbit platelets were stimulated with 1 X 10(-9)M sn-3-AGEPC (platelet activating factor) for 5 s, the levels of [3H]inositol monophosphate (IP), [3H]inositol diphosphate (IP2), and [3H]inositol triphosphate (IP3) increased about 1.5-, 3-, and 5-fold, respectively. Formation of these inositol polyphosphates was strikingly independent of extracellular Ca2+. Inactive analogs of sn-3-AGEPC, i.e., lysoGEPC and stereoisomer sn-1-AGEPC, did not cause production of any inositol polyphosphate. Pretreatment of platelets with indomethacin (5 microM) had little effect on this phenomenon. On the other hand, a platelet activating factor antagonist, CV-3988, blocked the AGEPC-stimulated production of radioactive IP, IP2, and IP3. Similarly forskolin, an activator of adenylate cyclase, at 5 microM or above completely abolished AGEPC-induced aggregation, [3H]serotonin secretion, and formation of [3H]inositol polyphosphates. In the light of the emerging role of AGEPC in inflammation, hypotension, and other cardiovascular processes, studies with platelets reported here indicate that forskolin could be a useful tool for manipulating AGEPC responses. It is further concluded that AGEPC-induced formation of inositol polyphosphate is an early response "specific" to AGEPC, mediated via extracellular Ca2+-independent phosphoinositide phosphodiesterase, and could play a role in intracellular Ca2+ mobilization and platelet shape change.
...
PMID:Platelet activating factor-stimulated formation of inositol triphosphate in platelets and its regulation by various agents including Ca2+, indomethacin, CV-3988, and forskolin. 387 14

The coupling of muscarinic-cholinergic receptors (mAChR) to adenylate cyclase and phospholipase C (PLC) second messenger systems has been demonstrated in many animal species. However, little is known about this association in the developing human central nervous system. Because of the proposed role of acetylcholine in the regulation of development and differentiation of neural cells, an understanding of these relationships during human fetal development gains importance. We report, in this communication, the coupling of mAChR with PLC in the human fetal brain. This coupling was determined using two independent approaches that relied upon estimating the accumulation of inositol phosphates (IPs) and cytidine diphosphate diacylglycerol (CDP-DAG). Carbachol treatment of brain slices, in the presence of lithium, resulted in the accumulation of IPs. Analysis of the kinetics of this accumulation showed that IP3 and IP2 increased rapidly, reaching a peak or plateau before IP. The results also showed that agonist-stimulated PLC produced two second messengers, IP3 and DAG. The production of DAG was strongly supported by the carbachol-dependent increase of CDP-DAG. The accumulation of IP and CDP-DAG was dependent on agonist concentration. The obtained EC50 values were approximately: carbachol 47 microM; acetylcholine 6 microM; and oxotremorine 25 microM. Unexpectedly, all three agonists demonstrated a similar efficacy. The cholinergic stimulation of inositide hydrolysis appears to be the result of activation of the m1 muscarinic receptor.
...
PMID:Muscarinic receptor-dependent activation of phospholipase C in the developing human fetal central nervous system. 798 80

Bombesin (Bn) receptor subtype 3 (BRS-3) is an orphan receptor that is a predicted member of the heptahelical G-protein receptor family and so named because it shares a 50% amino acid homology with receptors for the mammalian bombesin-like peptides neuromedin B (NMB) and gastrin-releasing peptide. In a recent targeted disruption study, in which BRS-3-deficient mice were generated, the mice developed obesity, diabetes, and hypertension. To date, BRS-3's natural ligand remains unknown, its pharmacology unclear, and cellular basis of action undetermined. Furthermore, there are few tissues or cell lines found that express sufficient levels of BRS-3 protein for study. To define the intracellular signaling properties of BRS-3, we examined the ability of [D-Phe6,beta-Ala11,Phe13, Nle14]Bn-(6-14), a newly discovered peptide with high affinity for BRS-3, and various Bn receptor agonists and antagonists to alter cellular function in hBRS-3-transfected BALB 3T3 cells and hBRS-3-transfected NCI-H1299 non-small cell lung cancer cells, which natively express very low levels of hBRS-3. This ligand stimulated a 4-9-fold increase in [3H]inositol phosphate formation in both cell lines under conditions where it caused no stimulation in untransfected cells and also stimulated an increase in [3H]IP1, [3H]IP2, and 3H]IP3. The elevation of [3H]IP was concentration-dependent, with an EC50 of 20-35 nM in both cell lines. [D-Phe6,beta-Ala11,Phe13,Nle14]Bn-(6-14) stimulated a 2-3-fold increase in [Ca2+]i, a 3-fold increase in tyrosine phosphorylation of p125(FAK) with an EC50 of 0.2-0.7 nM, but failed to either stimulate increases in cyclic AMP or inhibit forskolin-stimulated increases. None of nine naturally occurring Bn peptides or three synthetic Bn analogues reported to activate hBRS-3 did so with high affinity. No high affinity Bn receptor antagonists had high affinity for the hBRS-3 receptor, although two low affinity antagonists for gastrin-releasing peptide and NMB receptors, [D-Arg1,D-Trp7,9, Leu11]substance P and [D-Pro4,D-Trp7,9,10]substance P-(4-11), inhibited hBRS-3 receptor activation. The NMB receptor-specific antagonist D-Nal,Cys,Tyr,D-Trp,Lys,Val, Cys,Nal-NH2 inhibited hBRS-3 receptor activation in a competitive fashion (Ki = 0.5 microM). Stimulation of p125(FAK) tyrosine phosphorylation by hBRS-3 activation was not inhibited by the protein kinase C inhibitor, GF109203X, or thapsigargin, alone or in combination. These results show that hBRS-3 receptor activation increases phospholipase C activity, which causes generation of inositol phosphates and changes in [Ca2+]i and is also coupled to tyrosine kinase activation, but is not coupled to adenylate cyclase activation or inhibition. hBRS-3 receptor activation results in tyrosine phosphorylation of p125(FAK), and it is not dependent on activation of either limb of the phospholipase C cascade. Although the natural ligand is not a known bombesin-related peptide, the availability of [D-Phe6,beta-Ala11, Phe13,Nle14]Bn-(6-14), which functions as a high affinity agonist in conjunction with hBRS-3-transfected cell lines and the recognition of three classes of receptor antagonists including one with affinity of 0.5 microM, should provide important tools to assist in the identification of its natural ligand, the development of more potent selective receptor antagonists and agonists, and further exploration of the signaling properties of the hBRS-3 receptor.
...
PMID:Ability of various bombesin receptor agonists and antagonists to alter intracellular signaling of the human orphan receptor BRS-3. 959 99


1 2 Next >>

---