Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transforming growth factor-beta (TGF beta) produced by osteoblasts is present in high levels in bone and influences bone formation, replication of bone cells, and expression of osteoblast protein products. Interactions between bone active hormones and locally released and activated TGF beta were studied by examining the influence of TGF beta preincubation on PTH, calcitonin (CT), and vitamin D receptors in an osteoblastic cell line (UMR 106-06). Preincubation of UMR 106-06 cells with 1 ng/ml TGF beta for 3 days increased specific binding of [125I]PTH-related protein (PTHrP)(1-84) to 140% of that in control cells, but [125I]salmon CT binding decreased to 50% of controls. Binding isotherms indicated that the changes in binding were due to altered receptor numbers since affinities for 125I-labeled PTH and CT remained unchanged. The effect on receptor levels was time dependent, requiring 24 h preincubation with TGF beta for measurable changes, and dose dependent, with maximal effects seen with 1 ng/ml TGF beta. Binding of [3H]1,25(OH)2 vitamin D3 was increased to 130% of control in cytosolic extracts of UMR 106-06 cells pretreated for 3 days with 1 ng/ml TGF beta. Scatchard plots suggested an increase in receptor number without change in affinity. The adenylate cyclase response to PTH increased to 150% of control cells after 3 days of treatment with 1 ng/ml TGF beta; however, the adenylate cyclase response to CT was little changed. Forskolin- and cholera toxin-stimulated adenylate cyclase responses were increased by TGF beta treatment to 130-160% of control, indicating an increase in the stimulatory subunit of the G protein. Increased abundance of both Gs and Gi proteins were indicated by increased cholera toxin- or pertussis toxin-dependent [32P] NAD ribosylation of 47-kilodalton (kDa) and 42-kDa or 40-kDa proteins, respectively, in TGF beta-treated cells. Our data support a complex regulatory effect of TGF beta on UMR 106-06 cells with increases in PTH receptors, vitamin D receptors, and G proteins, whereas there is an apparent down-regulation of CT receptors. TGF beta might induce a more differentiated osteoblast phenotype of these cells, which already express differentiated features such as high alkaline phosphatase activity, PTH and vitamin D receptors, and collagenase production. Since low doses of PTH stimulate bone formation in vivo, TGF beta released or activated at sites of new bone formation might locally modulate PTH activity be allowing increased PTH receptor and postreceptor effectiveness.
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PMID:Transforming growth factor-beta modulates receptor binding of calciotropic hormones and G protein-mediated adenylate cyclase responses in osteoblast-like cells. 132 61

1,25-Dihydroxyvitamin D-3 (1,25(OH)2D3) has been shown to increase Ca2+ uptake readily in skeletal muscle through a dihydropyridine-sensitive pathway, cAMP levels and adenylate cyclase activity. In the present study, fluoride (F-), a potent guanine nucleotide binding protein (G protein) stimulator, rapidly increases vitamin D-deficient skeletal muscle Ca2+ uptake in a dose-dependent manner and with a similar time-course as 1,25(OH)2D3. The increment is detected within 1 min (15%) and steadily increases up to 15 min (60%). The effects of 1,25(OH)2D3 and F- are also observed in muscle from normal, vitamin D-replete chicks. AlCl3, which is required for G protein stimulation by F-, potentiates the effects of F-, Ca2+ uptake in 1,25(OH)2D3-dependent muscle is potentiated by F- and, analogous to the hormone, the effects of F- can be suppressed by Ca(2+)-channel antagonists. Direct exposure of microsomal membranes to 1,25(OH)2D3 reduces the specific binding of [gamma-35S]GTP to the membranes 40%. Pretreatment of muscle with Bordetella pertussis toxin (PTX), known to inhibit Gi, or with cholera toxin (CTX), known to stimulate Gs, produces an acute elevation of muscle Ca2+ uptake. 1,25(OH)2D3 potentiates CTX, but has no additional effect on PTX-dependent Ca2+ uptake. These results indicate that an interaction with an inhibitory G protein coupled to adenylate cyclase may be part of the mechanism by which 1,25(OH)2D3 increase Ca2+ uptake through regulation of Ca(2+)-channel gating by a cAMP-dependent pathway in skeletal muscle.
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PMID:A guanine nucleotide-binding protein mediates 1,25-dihydroxy-vitamin D-3-dependent rapid stimulation of Ca2+ uptake in skeletal muscle. 165 21

In the human premonocytic line U937, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) induces a functional NADPH oxidase, that is responsive to both phorbol esters and opsonized zymosan. The chemotactic peptide f-Met-Leu-Phe (fMLP) did not, however, induce superoxide generation by these cells. This was not due to the absence of receptors for fMLP. Although there was no significant binding of [3H]-fMLP to undifferentiated U937 cells, preincubation with 1,25-(OH)2D3 induced expression of specific and saturable binding sites. Moreover, fMLP induced a rapid and reversible rise in cytosolic free Ca2+ concentration ([Ca2+]i) in 1,25-(OH)2D3-treated U937 cells, but not in control or 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3)-treated cells. This [Ca2+]i response was dependent on concentrations of both fMLP and 1,25-(OH)2D3 and was observed at physiologic concentrations of the hormone (approximately 25 pM). The rise in [Ca2+]i induced by fMLP in 1,25-(OH)2D3-treated U937 cells was blocked by pertussis toxin and presumably mediated by inositol (1,4,5)-trisphosphate generation. These results indicate that in U937 cells differentiated with 1,25-(OH)2D3, inositol phosphate-mediated [Ca2+]i responses to fMLP are uncoupled from NADPH oxidase activation.
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PMID:1,25-dihydroxyvitamin D3 induces responsiveness to the chemotactic peptide f-Met-Leu-Phe in the human monocytic line U937: dissociation between calcium and oxidative metabolic responses. 254 Feb 55

We examined the characteristics of PTH resistance in vitamin D-deficient rats employing renal membranes in vitro. Homologous desensitization was characterized by diminished PTH-stimulated adenylate cyclase activity and was associated with a reduction in PTH-binding capacity, but not affinity. Heterologous desensitization was also seen, as manifested by decreased calcitonin (CT)-stimulated adenylate cyclase activity with normal CT receptor binding. The reduced capacity of the nonhormonal effectors NaF and guanylylimidodiphosphate to stimulate adenylate cyclase indicated a postreceptor defect at the level of the guanyl nucleotide-binding protein (G protein), whereas a normal forskolin response was consistent with a fully functional catalytic component. The G protein deficiency was confirmed by demonstrating that the addition of extracts of vitamin D-sufficient membranes to preparations of vitamin D-deficient membranes restored the normal responses to NaF and guanylylimidodiphosphate. In addition, cholera toxin- and pertussis toxin-catalyzed labeling of vitamin D-deficient renal membranes with [32P]NAD revealed a decrease in both the stimulatory and inhibitory binding proteins. Experiments with testicular membranes in vitro indicated that the adenylate cyclase abnormality was absent in tissue lacking PTH receptors. The results suggest that a major contribution to PTH resistance in vitamin D-deficient animals is a postreceptor defect at the level of the G proteins and that this defect is manifest only in tissue expressing the PTH receptor.
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PMID:Parathyroid hormone desensitization in renal membranes of vitamin D-deficient rats is associated with a postreceptor defect. 283 76

The steroid hormone 1,25(OH)2-vitamin D-3 [1,25(OH)2D3] stimulated phospholipase A2 (PLA2) activity in embryonic chick myoblasts releasing [3H]arachidonic acid from the sn-2 position of phospholipids. GTP-binding protein mediation of 1,25(OH)2D3-dependent PLA2 activity was investigated in cells prelabeled with [3H]arachidonic acid. AIF4-, a G-protein activator, mimicked 1,25(OH)2D3-stimulated arachidonic acid release from myoblasts in a dose-dependent manner. Consistent with the involvement of a G-protein in the activation of PLA2 by the hormone, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), a stable GTP analogue which activates G-protein mediated signals, strongly enhanced arachidonic acid release in myoblasts. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), which competitively inhibits G-protein activation by GTP and its analogues, abolished 1,25(OH)2D3-dependent arachidonic acid release. Bordetella pertussis toxin pretreatment significantly suppressed the hormone action whereas cholera toxin had minor effects on 1,25(OH)2D3 action. Hormone-induced activation of PLA2 was mimicked by the Ca2+ ionophore A23187 and blocked by nifedipine, but was unaffected by neomycin, a phospholipase C inhibitor, ruling out the contribution of phosphoinositide metabolism to arachidonic acid release. These results suggest that 1,25(OH)2D3-stimulation of PLA2 activity in embryonic chick myoblasts is mediated by a pertussis toxin-sensitive GTP-binding protein coupled to influx of extracellular calcium.
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PMID:1,25(OH)2-vitamin D-3 stimulates phospholipase A2 activity via a guanine nucleotide-binding protein in chick myoblasts. 764 3

We have previously shown that 24,25-(OH)2D3 plays a major role in resting zone (RC) chondrocyte differentiation and that this vitamin D metabolite regulates protein kinase C (PKC). The aim of the present study was to identify the signal transduction pathway used by 24,25-(OH)2D3 to stimulate PKC activation. Confluent, fourth passage RC cells from rat costochondral cartilage were used to evaluate the mechanism of PKC activation. Treatment of RC cultures with 24,25-(OH)2D3 for 90 min produced a dose-dependent increase in diacylglycerol (DAG). Addition of R59022, a diacylglycerol kinase inhibitor, significantly increased PKC activity in cultures treated with 24,25-(OH)2D3. Addition of dioctanoylglycerol (DOG) to plasma membranes isolated from RC increased PKC activity 447-fold. Addition of pertussis toxin or cholera toxin to control cultures elevated basal PKC activity. When added together with 10(-9) M 24,25-(OH)2D3, there was an additive effect on PKC activity but in cultures treated with 10(-8) M 24,25-(OH)2D3, only the hormone-dependent stimulation of PKC was observed. The phospholipase C inhibitor, U73-122, had no effect on PKC activity, indicating that the DAG produced in response to 24,25-(OH)2D3 is not derived from phosphatidylinositol. Addition of the tyrosine kinase inhibitor, genistein, also had no effect on 24,25-(OH)2D3-stimulated PKC, further supporting the hypothesis that phospholipase C is not involved in the mechanism and that phospholipase D is responsible for the increase in DAG production. Phospholipase A2 inhibitors, quinacrine and AACOCF3, and the cyclooxygenase inhibitor indomethacin increased PKC activity in the RC cultures. Exogenous PGE2, one of the downstream products of phospholipase A2 action, inhibited PKC activity. These results suggest that 24,25-(OH)2D3 regulates PKC activity by two distinct phospholipid-dependent mechanisms: production of DAG via phospholipase D and inhibition of the production of PGE2 via inhibition of phospholipase A2 and cyclooxygenase.
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PMID:24,25-(OH)2D3 regulates protein kinase C through two distinct phospholipid-dependent mechanisms. 895

We have shown that estrogens and calcitriol, the hormonally active form of vitamin D, increase the concentration of intracellular calcium ([Ca2+]i) within 5 s by mobilizing calcium from the endoplasmic reticulum and the formation of inositol 1,4, 5-trisphosphate and diacylglycerol. Because the activation of effectors as phospholipase C (PLC) coupled to G-proteins is the early event in the signal transduction pathway leading to the inositol 1,4,5-trisphosphate formation and to [Ca2+]i increase, we described different PLC isoforms (beta1, beta2, gamma1, and gamma2, but not beta4) in female rat osteoblasts using Western immunoblotting. The data showed that phospholipase C beta was involved in the mobilization of Ca2+ from the endoplasmic reticulum of Fura-2-loaded confluent osteoblasts by calcitriol and 17beta estradiol, and PLC gamma was ineffective. The data also showed that only a PLC beta1 linked to a Pertussis toxin-insensitive G-protein and a PLC beta2 coupled to a Pertussis toxin-sensitive G-protein are involved in the effects of calcitriol and 17beta estradiol on the mobilization of Ca2+ from intracellular Ca2+ stores. In conclusion, these results may be an important step toward understanding membrane effects of these steroids and may be an additional argument in favor of membrane receptors to steroid hormones.
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PMID:Phospholipase C beta and membrane action of calcitriol and estradiol. 911 51

1alpha,25-(OH)(2)D(3) regulates protein kinase C (PKC) activity in growth zone chondrocytes by stimulating increased phosphatidylinositol-specific phospholipase C (PI-PLC) activity and subsequent production of diacylglycerol (DAG). In contrast, 24R,25-(OH)(2)D(3) regulates PKC activity in resting zone (RC) cells, but PLC does not appear to be involved, suggesting that phospholipase D (PLD) may play a role in DAG production. In the present study, we examined the role of PLD in the physiological response of RC cells to 24R,25-(OH)(2)D(3) and determined the role of phospholipases D, C, and A(2) as well as G-proteins in mediating the effects of vitamin D(3) metabolites on PKC activity in RC and GC cells. Inhibition of PLD with wortmannin or EDS caused a dose-dependent inhibition of basal [3H]-thymidine incorporation by RC cells and further increased the inhibitory effect of 24R,25-(OH)(2)D(3). Wortmannin also inhibited basal alkaline phosphatase activity and [35]-sulfate incorporation and decreased the stimulatory effect of 24R,25-(OH)(2)D(3). This inhibitory effect of wortmannin was not seen in cultures treated with the PI-3-kinase inhibitor LY294002, verifying that wortmannin affected PLD. Wortmannin also inhibited basal PKC activity and partially blocked the stimulatory effect of 24R,25-(OH)(2)D(3) on this enzyme activity. Neither inhibition of PI-PLC with U73122, nor PC-PLC with D609, modulated PKC activity. Wortmannin had no effect on basal PLD in GC cells, nor on 1alpha,25-(OH)(2)D(3)-dependent PKC. Inhibition of PI-PLC blocked the 1alpha,25-(OH)(2)D(3)-dependent increase in PKC activity but inhibition of PC-PLC had no effect. Activation of PLA(2) with melittin inhibited basal and 24R,25-(OH)(2)D(3)-stimulated PKC in RC cells and stimulated basal and 1alpha,25-(OH)(2)D(3)-stimulated PKC in GC cells, but wortmannin had no effect on the melittin-induced changes in either cell type. Pertussis toxin modestly increased the effect of 24R,25-(OH)(2)D(3) on PKC, whereas GDPbetaS had no effect, suggesting that PLD2 is the isoform responsible. This indicates that 1alpha,25-(OH)(2)D(3) regulates PKC in GC cells via PI-PLC and PLA(2), but not PC-PLC or PLD, whereas 24R,25-(OH)(2)D(3) regulates PKC in RC cells via PLD2.
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PMID:The effect of 24R,25-(OH)(2)D(3) on protein kinase C activity in chondrocytes is mediated by phospholipase D whereas the effect of 1alpha,25-(OH)(2)D(3) is mediated by phospholipase C. 1154 56

Growth plate chondrocyte function is modulated by the vitamin D metabolite 1alpha,25-(OH)(2)D(3) via activation of protein kinase C (PKC). In previous studies with cells derived from prehypertrophic and upper hypertrophic zones of rat costochondral cartilage (growth zone cells), inhibition of prostaglandin production with indomethacin caused a decrease in the stimulation of PKC activity, suggesting that changes in prostaglandin levels mediate the 1alpha,25-(OH)(2)D(3)-dependent response in these cells. Growth zone cells also respond to PGE(2) directly, indicating that prostaglandins act as autocrine or paracrine regulators of chondrocyte metabolism in the growth plate. The aim of the present study was to identify which PGE(2) receptor subtypes (EP) mediate the effects of PGE(2) on growth zone cells. Using primers specific for EP1-EP4, reverse transcription-polymerase chain reaction (RT-PCR) amplified EP1 and EP2 cDNA in a RT-dependent manner. In parallel experiments, we used EP subtype-specific agonists to examine the role of EP receptors in 1alpha,25-(OH)(2)D(3)-mediated cell proliferation and differentiation. 17-Phenyl-trinor-PGE(2) (PTPGE(2)), an EP1 agonist, decreased [3H]-thymidine incorporation in a dose-dependent manner and augmented the 1alpha,25-(OH)(2)D(2)-induced inhibition of [3H]-thymidine incorporation. PTPGE(2) also caused significant increases in proteoglycan production, as measured by [35S]-sulfate incorporation, and alkaline phosphatase specific activity. 1alpha,25-(OH)(2)D(3)-induced alkaline phosphatase activity was only slightly stimulated by PTPGE(2). In contrast, 1alpha,25-(OH)(2)D(3)-induced PKC activity was synergistically increased by PTPGE(2), whereas EP1 antagonists SC-19220 and AH6809 inhibited PKC activity in a dose-dependent manner. The EP2, EP3 and EP4 agonists had no effect on the various cell-induced responses measured. EP1 receptor-induced responses were blocked by the phospholipase C inhibitor U73122, and reduced by PKA inhibitors. EP1 receptor-induced PKC activity was insensitive to pertussis toxin or choleratoxin but blocked by the G-protein inhibitor GDPbetaS, suggesting the involvement of G(q). These results suggest that the EP1 receptor subtype mediates various PGE(2)-induced cellular responses in growth zone chondrocytes leading to decreased proliferation and enhanced differentiation, as well as the effect of 1alpha,25-(OH)(2)D(3) on cellular maturation.
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PMID:Characterization of PGE(2) receptors (EP) and their role as mediators of 1alpha,25-(OH)(2)D(3) effects on growth zone chondrocytes. 1159 7

Osteoblast apoptosis plays a crucial role in bone remodeling. Physiological doses of 1 alpha,25(OH)(2)-vitamin D(3) (1,25D) protect osteoblasts against apoptosis by means of mechanisms only partially understood. We studied activation of an Akt survival cascade downstream of 1,25D nongenomic stimulation of phosphatidylinositide-3'-kinase (PI3K) in osteoblastic cells. We measured a dose- and time-dependent 1,25D induction of Akt phosphorylation (p-Akt) in cultured osteoblastic cells. Maximal response was achieved with 10 nM 1,25D after 5 min. We found that staurosporine (STSP)-induced apoptosis was significantly reduced in 1,25D-pretreated osteoblasts. 1,25D prosurvival effects were abolished when cells were preincubated with inhibitors of PI3K activation. By means of siRNA silencing, we proved that 1,25D induction of p-Akt requires a classic vitamin D receptor (VDR) in osteoblasts. Furthermore, non-osteoblastic CV-1 cells transfected with an enhanced green fluorescent protein (EGFP)-VDR construct responded to 1,25D treatment with a rapid p-Akt response associated with increased cell survival not detected in native, nontransfected cells. We measured increased levels of p-Akt substrates p-Bad and p-FKHR and significantly reduced activity of caspases 8 and 3/7 after 1,25D treatment. In addition, 1,25D-induced protection against apoptosis was abolished when osteoblasts were preincubated with pertussis toxin. We conclude that anti-apoptotic effects of 1,25D in osteoblasts occur through nongenomic activation of a VDR/PI3K/Akt survival pathway that includes phosphorylation of multiple p-Akt substrates and reduction of caspase activities.
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PMID:Vitamin D receptor-dependent 1 alpha,25(OH)2 vitamin D3-induced anti-apoptotic PI3K/AKT signaling in osteoblasts. 1841 Feb 28


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