Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The primary structure of phenylalanine hydroxylase purified from rat liver was investigated with high speed gel filtration chromatography, cyanogen bromide cleavage and end group analyses of polypeptides derived from the enzyme. On gel filtration in the presence of 6M guanidine hydrochloride, the enzyme gave a single peak corresponding to a molecular weight of 52,000. In the same system the enzyme that had been cleaved with cyanogen bromide gave two peptides (CB1, Mr = 32,800 and CB2, Mr = 20,400). Sequence studies showed that the alignment of these two peptides was CB1 - CB2. Furthermore, in experiments using 32P phosphorylated enzyme, the site of phosphorylation by cAMP-dependent protein kinase was found to be located on the CB1 peptide. The NH2-terminus of this enzyme, which was found to be blocked, was shown to be N-acetylalanine. By both carboxypeptidase A digestion and hydrazinolysis, the carboxyl terminus was identified as serine. These data indicate that the phenylalanine hydroxylase molecule from rat liver is composed of subunits which are homogenous or, at least, very similar in their primary structure.
 ...
PMID:Studies on the primary structure of rat liver phenylalanine hydroxylase. 397 94

This review details the biochemical events that follow IgE dimerization by antigen and cross-linking of receptors and are linked with the early rise in cyclic AMP. That the monophasic rise in cyclic AMP at 15 s is essential to the degranulation process is evident by pharmacological manipulation of adenylate cyclase, using specific activators and inhibitors to achieve potentiation and inhibition of immunologic release, respectively. Although only a small percentage of membrane adenylate cyclase is transmembrane linked to IgE-Fc perturbation, its product, cyclic AMP, is elevated during activation and is responsible for the activation of two protein kinase isoenzymes at 30-60 s. This sequence appears to be essential for secretion to occur, as evidenced by dose-related inhibition of both beta-hexosaminidase release and protein kinase activation by adenylate cyclase inhibitors. Competitive activation of cyclic AMP-dependent protein kinase activity by a phosphodiesterase inhibitor leads to inhibition of mediator release by diverting an essential enzyme or recruiting an inhibitory sequence. The precise functional role of the mast cell cyclic AMP-dependent protein kinases has not yet been identified, but there is much evidence in other cell types that protein phosphorylation is an essential accompaniment to cellular regulation. Although other apparently essential biochemical steps are noted, such as uncovering a serine esterase, methylation of membrane phospholipid, and increased Ca2+ influx, only a portion of the activation-secretion response is presented here as a sequence, namely, the IgE-Fc receptor-initiated, transmembrane-coupled activation of adenylate cyclase and the subsequent cytoplasmic cyclic AMP-dependent activation of types I and II protein kinases.
 ...
PMID:Enzymatic regulation of mast cell activation and secretion by adenylate cyclase and cyclic AMP-dependent protein kinases. 617 64

The initial monophasic rise in cyclic AMP beginning 5-15 sec after bridging of rat mast cell IgE-Fc receptors precedes the secretion of granule constituents, thereby implying a causal relationship. Direct evidence for a relationship between IgE-dependent transmembrane activation of adenylate cyclase and granule secretion was provided by the capacity of purine-modified (R site active) and ribose-modified (P site active) adenosine analogs, respectively, to augment and suppress mediator release while simultaneously increasing and decreasing the activity of adenylate cyclase. R site stimulation alone does not cause granule secretion but augments the rate and magnitude of IgE-Fc receptor-induced secretion, reflecting the coupled relationship of such receptors. Inhibition of adenylate cyclase at the P site attenuates the rise in cellular cyclic AMP and suppresses IgE-dependent mediator release in a parallel and superimposable dose-response fashion. Further, the relationship between the attenuation in the rise in cyclic AMP and the diminution in immunologic mediator release is linear with the regression line passing through the origin, indicating a direct relationship between the IgE-dependent activation of adenylate cyclase and preformed mediator release. Although not the only events in coupled mast cell activation--secretion, there is a sequential relationship among perturbation of IgE-Fc receptors, transmembrane activation of adenylate cyclase, elevation of cytoplasmic levels of cyclic AMP, activation of cyclic AMP-dependent protein kinase, and secretion of mast cell granules.
 ...
PMID:Role of adenylate cyclase in immunologic release of mediators from rat mast cells: agonist and antagonist effects of purine- and ribose-modified adenosine analogs. 625 61

Previous studies have shown that perturbation of the mast cell IgE-Fc receptor activates adenylate cyclase so as to raise cellular levels of cyclic AMP and to activate cyclic AMP-dependent protein kinase. Theophylline, an inhibitor of cytoplasmic cyclic nucleotide phosphodiesterase, raises cellular cyclic AMP levels, activates Type I and Type II cytoplasmic cyclic AMP-dependent protein kinase isoenzymes, and inhibits immunologic mediator release in a dose-dependent fashion. Since the EC50 values for each of these effects are similar (8 to 9.5 mM), it seems likely that a relationship exists between the activation of cyclic AMP-dependent protein kinase and the inhibition of mediator release. Such inhibition could be due to either to the uncovering of an inhibitory protein by phosphorylation or to the depletion of cyclic AMP-dependent protein kinase holoenzyme, which is essential for productive IgE-Fc receptor-induced activation-secretion coupling. PGD2, which also raises mast cell cyclic AMP levels in a dose-dependent fashion and interacts synergistically with theophylline in this regard, fails to suppress mediator release alone or to add to the inhibitory effect of theophylline. The finding that PGD2 also fails to activate cyclic AMP-dependent protein kinase suggests that the adenylate cyclase stimulated by this agonist is not linked to the mast cell activation-secretion response.
 ...
PMID:Effects of prostaglandin D2 and theophylline on rat serosal mast cells: discordance between increased cellular levels of cyclic AMP and activation of cyclic AMP-dependent protein kinase. 626 8

Stereo-specific perturbation of the IgE-receptor (shown in previous studies) produces a monophasic rise in cyclic AMP that peaks at 15 s and a depletion of cyclic AMP-dependent protein kinase that plateaus at 30-60 s. The previously observed linear relationship between the attenuation in the monophasic rise in cyclic AMP and the quantity of mediator release in the presence of incremental concentrations of the adenosine analogue 2',5',-dideoxyadenosine, DDA, which is known to inhibit adenylate cyclase, indicated a direct relationship between receptor perturbation, transmembrane activation of adenylate cyclase, and granule secretion. The role of cyclic AMP as a second messenger in this sequence is now apparent from the linear relationship between net percent mediator release and net percent activation of cyclic AMP-dependent protein kinase isoenzyme when IgE-dependent activation of adenylate cyclase is suppressed by incremental quantities of DDA. There was a comparable percent activation of both types I and II mast cell cyclic AMP-dependent protein kinase isoenzymes with anti-IgE-induced activation and secretion, and there was a parallel suppression of the activation of both isoenzymes in the presence of DDA. Although these studies firmly link the activation of cytoplasmic cyclic AMP-dependent protein kinase to the IgE receptor-initiated transmembrane activation of adenylate cyclase. they do not discriminate among the functions of the two isoenzymes.
 ...
PMID:Mast cell mediator release as a function of cyclic AMP-dependent protein kinase activation. 627 Feb 26

Adenosine activates adenylate cyclase and phospholipase C in mast cells and potentiates stimulated mediator release. To determine whether activation of adenylate cyclase is necessary for the effects of adenosine on the mast cell secretory process, a specific inhibitor of cAMP-dependent protein kinase, KT5720, was used. Antigen and adenosine each induced a rapid increase in mast cell cAMP-dependent protein kinase activity within 30 s. Preincubation with KT5720 (100 nM-10 microM) suppressed cAMP-dependent protein kinase activity and inhibited antigen-stimulated beta-hexosaminidase and leukotriene C4 releases. Adenosine retained its ability to potentiate beta-hexosaminidase release in antigen- and A23187-stimulated cells even in the presence of complete cAMP-dependent protein kinase inhibition. Mast cells rendered unresponsive to adenosine-related signals by preincubation with adenosine analogs maintained this hyporesponsiveness after incubation with KT5720. It appears that the abilities of adenosine to augment mast cell degranulation and induce receptor hyporesponsiveness are independent of changes in cAMP.
 ...
PMID:Inhibition of protein kinase A fails to alter mast cell adenosine responsiveness. 774 Oct 46

We have investigated the effects of wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI 3-kinase), on antigen-mediated signaling in the RBL-2H3 mast cell model. In RBL-2H3 cells, the cross-linking of high affinity IgE receptors (Fc epsilon R1) activates at least two cytoplasmic protein tyrosine kinases, Lyn and Syk, and stimulates secretion, membrane ruffling, spreading, pinocytosis, and the formation of actin plaques implicated in increased cell-substrate adhesion. In addition, Fc epsilon R1 cross-linking activates PI 3-kinase. It was previously shown that wortmannin causes a dose-dependent inhibition of PI 3-kinase activity and also inhibits antigen-stimulated degranulation. We report that the antigen-induced synthesis of inositol(1,4,5)P3 is also markedly inhibited by wortmannin. Consistent with evidence in other cell systems implicating phosphatidylinositol(3,4,5)P3 in ruffling, pretreatment of RBL-2H3 cells with wortmannin inhibits membrane ruffling and fluid pinocytosis in response to Fc epsilon R1 cross-linking. However, wortmannin does not inhibit antigen-induced actin polymerization, receptor internalization, or the actin-dependent processes of spreading and adhesion plaque formation that follow antigen stimulation in adherent cells. Wortmannin also fails to inhibit either of the Fc epsilon R1-coupled tyrosine kinases, Lyn or Syk, or the activation of mitogen-activated protein kinase as measured by in vitro kinase assays. Strikingly, there is substantial in vitro serine/threonine kinase activity in immunoprecipitates prepared from Fc epsilon R1-activated cells using antisera to the p85 subunit of PI 3-kinase. This activity is inhibited by pretreatment of the cells with wortmannin or by the direct addition of wortmannin to the kinase assay, suggesting that PI 3-kinase itself is capable of acting as a protein kinase. We conclude that Fc epsilon R1 cross-linking activates both lipid and protein kinase activities of PI 3-kinase and that inhibiting these activities with wortmannin results in the selective block of a subset of Fc epsilon R1-mediated signaling responses.
 ...
PMID:Wortmannin blocks lipid and protein kinase activities associated with PI 3-kinase and inhibits a subset of responses induced by Fc epsilon R1 cross-linking. 853 12

Stem cell factor (SCF) and interleukin-3 (IL-3) both act on several target hematopoietic populations, including mast cells. We have isolated a unique murine mast cell line, B6M, that is phenotypically similar to immature mast cells. For B6M cells, IL-3 is a survival factor and alone does not stimulate proliferation. SCF can stimulate proliferation of B6M cells, and together IL-3 and SCF synergize to stimulate optimal proliferation and long-term growth. A sustained induction of c-myc is observed only in the presence of SCF (with or without IL-3). In B6M cells, both IL-3 and SCF stimulate phosphorylation of Shc and activation of the Ras, Raf-1, MAPK pathway. Interestingly, IL-3 plus SCF synergistically activate MAPK. IL-3, but not SCF, leads to activation of Jak 2 and Stat 5 and induces pim-1 expression. From these data, we suggest that the induction of pim-1 and c-myc is independently regulated. Furthermore, IL-3-stimulated activation of the Jak 2/Stat 5 pathway, induction of pim-1, and activation of the Ras/MAPK pathway are insufficient to mediate proliferation of B6M cells. The unusual IL-3 response of B6M cells provides a useful model to dissect signals required for IL-3-stimulated survival and proliferation.
 ...
PMID:Signaling pathways activated in a unique mast cell line where interleukin-3 supports survival and stem cell factor is required for a proliferative response. 861 90

Aggregation of the high affinity receptor for IgE (FcepsilonRI) on the mucosal mast cell line, RBL-2H3, results in the rapid and persistent tyrosine phosphorylation of Vav. Immunoprecipitation of Vav from activated cells revealed co-immunoprecipitated phosphoproteins of molecular weights identical to the FcepsilonRI beta and gamma chains, and the former was reactive with antibody to the FcepsilonRI beta chain. Conversely, Western blots revealed the presence of p95 Vav in FcepsilonRI immunoprecipitates. The association of Vav and of Grb2 with the receptor was found to be regulated by aggregation of the receptor, and the interaction of Vav with the FcepsilonRI was localized to the gamma chain. To gain insight on the signaling pathway in which Vav participates, we investigated the in vivo associations of Vav with other molecules. A reducible chemical cross-linking agent was used to covalently maintain protein interactions under nonreducing conditions. A fraction of Vav increased in mass to form a complex of >300 kDa in molecular mass. Under reducing conditions the cross-linked Vav immunoprecipitates showed the presence of Grb2, Raf-1, and p42(mapk) (ERK2). In vitro kinase assays of Raf-1 activity associated with Vav revealed that this complex had an activity greater than that of Raf-1 derived from nonactivated cells, and aggregation of the FcepsilonRI did not modulate this activity. In contrast, aggregation of the FcepsilonRI increased the total Raf-1 activity by 2-5-fold. These results demonstrate that Vav associates constitutively with components of the mitogen-activated protein kinase pathway to form an active multimeric signaling complex whose in vivo activity and associations may be directed by aggregation of the FcepsilonRI. The findings of this study may also be relevant to other members of the immune recognition receptor family that share the T-cell antigen receptor zeta/gamma chains.
 ...
PMID:Association of a p95 Vav-containing signaling complex with the FcepsilonRI gamma chain in the RBL-2H3 mast cell line. Evidence for a constitutive in vivo association of Vav with Grb2, Raf-1, and ERK2 in an active complex. 890 Jan 82

Mast cell activation-secretion by several signal transduction pathways results in the release of proinflammatory mediators including histamine, proteases, arachidonic acid metabolites and multifunctional cytokines. In the present investigations the activation-secretion responses of the cytokine-independent, cloned 10P2 cell line have been explored. [14C]Serotonin (5-HT) preloaded cells were stimulated with antigen, with and without IL-4, ionophore A23187, thapsigargin or phorbol myristate acetate (PMA). Following passive sensitization with anti-dinitrophenol (anti-DNP) IgE, mast cells released up to 31% of incorporated [14C]5-HT when stimulated with specific antigen (DNP-human serum albumin). This response was potentiated by pretreatment with IL-4. Significant degranulation (50%) was noted following treatment with calcium ionophore A23187, thapsigargin and ionophore A23187/PMA. Collectively, these results suggest that 10P2 cells undergo activation-secretion responses, assessed as degranulation of preloaded [14C]5-HT when challenged with IgE antigen, by influx of extracellular calcium or release of intracellular calcium stores, or by direct activation of protein kinase isozymes. As a growth factor-independent cell line, 10P2 cells may be a valuable adjunct to existing mast cell model systems currently used for pharmacologic investigations.
 ...
PMID:Activation-secretion coupling in 10P2 murine mast cells challenged with IgE-antigen, ionophore A23187, thapsigargin and phorbol ester. 912 38


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