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

Available data indicate that adipocytes are targets for PTH action, and chronic excess of PTH increases calcium burden of fat tissue, suggesting that PTH increases entry of calcium into adipocytes. The present study examined the effects of PTH-(1-84) and its amino-terminal fragment, PTH-(1-34), on cytosolic calcium ([Ca2+]i) of adipocytes and evaluated the cellular pathways that mediate the potential effect of PTH on [Ca2+]i of these cells. PTH-(1-84) but not PTH-(1-34) produced a dose-dependent rise in [Ca2+]i of adipocytes. This effect occurred in the presence or absence of calcium in the media, but the magnitude of the rise in [Ca2+]i was significantly greater when calcium was present in the media. The PTH antagonist [Nle8,18Tyr34]bPTH(7-34)NH2, verapamil, and nifedipine blocked to variable degrees the PTH-induced rise in [Ca2+]i. The phorbol ester 12-O-tetradecanoyl phorbol-13-acetate, and the GTP-binding protein (G protein) GTP gamma S also produced a dose-dependent rise in [Ca2+]i of adipocytes. These effects were inhibited by staurosporine and the G protein inhibitor guanosine 5'-O-1(2-thiodiphosphate), respectively. Similary, staurosporine, calphostin C, guanosine 5'-O-1(2-thiodiphosphate), and pertussis toxin inhibited the effect of PTH on [Ca2+]i of adipocytes. (Bu)2cAMP also increased [Ca2+]i of adipocytes, but PTH did not stimulate cAMP production by adipocytes, and N-[2(p-bromocin-namylamino)ethyl]5-isoquinoline-sulfonamide, an inhibitor of protein kinase A, did not affect the PTH-induced rise in [Ca2+]i of adipocytes. The data indicate that: 1) PTH-(1-84) increases [Ca2+]i of adipocytes; 2) this action of the hormone is receptor mediated; 3) the hormone uses a G protein activation of calcium channels and the phospholipase C pathway in mediating its action on [Ca2+]i; and 4) the rise in [Ca2+]i is due to both increased calcium influx into the adipocytes and mobilization of calcium from intracellular stores.
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PMID:Effects of parathyroid hormone on cytosolic calcium of rat adipocytes. 752 54

Experimental evidence exists for the presence of parathyroid cell membrane calcium channels that respond to plasma calcium. In previous reports, the effects of various calcium channel agents on PTH secretion have revealed conflicting results. To resolve some of these inconsistencies, we have compared the pure calcium channel agonist, (+)202-791, and its antagonistic enantiomer (-)202-791 with other calcium channel agents--verapamil, nifedipine, and (+)Bay-K-8644. The agonist (+)202-791 enhanced 45Ca+2 uptake and decreased PTH secretion, while the antagonist (-)202-791 decreased 45Ca+2 uptake and increased PTH secretion. The calcium channel appears coupled to a G-protein as indicated by pertussis toxin treatment of the cells. The enantiomers (+/-)202-791 had little effect on intracellular cAMP production suggesting that the calcium channel may not be responsible for the previously observed calcium-mediated changes in cAMP. The antagonist (-)202-791 increased the phosphorylation of a 60-kd protein. The enantiomers (+/-)202-791 did not alter the effect of depolarizing concentrations of potassium on PTH secretion. Our results suggest that calcium channels provide a pathway for the movement of calcium across the plasma membrane and that this pool of calcium regulates, at least in part, PTH secretion.
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PMID:Role of calcium channels in parathyroid hormone secretion. 754 1

We have investigated the role of the C-terminal cytoplasmic domain of the human PTH receptor in effector coupling. Following transient expression in COS-1 cells, coupling to both AC and PI-PLC was observed with the full-length receptor. Progressive C-terminal truncations did not dissociate activation of the two signalling systems. In stably transfected 293 cells, however, the full-length receptor as well as the majority of truncated constructs stimulated AC exclusively but failed to activate PI-PLC. Activation of both signalling systems was again observed following stable expression of a severely truncated receptor (R483) in 293 cells. In this case, pertussis toxin was also found to potentiate the cAMP response to hPTH-(1-38) significantly, indicating functional coupling of R483 to Gi proteins. Our results suggest that a core region of the human PTH receptor (first, second, third intracellular loop) can interact promiscuously with different G proteins and that the C-terminus of the full-length receptor directs the receptor towards an interaction with Gs.
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PMID:A C-terminally truncated human parathyroid hormone receptor is functional and activates multiple G proteins. 808 81

Tumor necrosis factor (TNF-alpha) has been shown to play an important role in local control of bone remodeling. The interaction of TNF-alpha and PTH was evaluated in UMR-106-01 cells, a phenotypic osteoblastic osteosarcoma cell line. We examined the influence of TNF-alpha on the two signal transduction systems triggered by PTH in UMR-106-01 cells, adenylate cyclase and free cytosolic calcium ([Ca2+]i). cAMP generation was inhibited in TNF-alpha-pretreated cells by 69, 61, 34, and 21% at PTH concentrations of 0.1, 1, 10, and 100 nM, respectively. Inhibition was seen at TNF-alpha doses of 100-1500 units/ml after a minimum incubation time of 12 h. TNF-alpha inhibition of the PTH-stimulated increase in [Ca2+]i was even more pronounced: treated cells showed no change in baseline [Ca2+]i after stimulation with 40 nM PTH. Treatment with TNF-alpha was also found to inhibit both arms of the PTH response in the nontransformed osteoblastic cell line, MC3T3-E1. TNF-alpha treatment did not alter cAMP generation in response to PGE2. TNF-alpha inhibition of the PTH-stimulated cAMP response was reversed completely by addition of cholera toxin (5 micrograms/ml) and partially by forskolin (10 microM) but not pertussis toxin (100 and 500 ng/ml). Scatchard analysis using PTHrP revealed that TNF-alpha treatment reduced the number of receptors but had no effect on KD. These findings suggest that TNF-alpha inhibits the osteoblastic response to PTH at least in part because of a reduction in receptor number. Further investigation is indicated to provide insight into the interaction of calciotropic hormones and cytokines in vivo.
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PMID:Tumor necrosis factor alpha modulates parathyroid hormone action in UMR-106-01 osteoblastic cells. 825 56

To verify whether the heterogeneous intracellular calcium ([Ca2+]i) responses to PTH observed in the UMR 106-01 osteogenic sarcoma cells are secondary to cell cycle asynchrony or to genotypic differences within the population, we synchronized cell monolayers at the G1/S boundary using a sequential thymidine-aphidicolin block. Video image analysis of fura-2-loaded cells revealed that PTH (10(-7) M) induced transient increases of [Ca2+]i preferentially in cells in S phase (82% response frequency, n = 63; 286 +/- 33% of baseline, n = 29), whereas cells in G1 phase responded poorly to PTH (10% response frequency, n = 51; 140 +/- 8% of baseline, n = 5). In contrast, cell exposure to 2% fetal calf serum was followed by [Ca2+]i transients in 83% (n = 42) of cells in G1 phase, but in only 25% (n = 63) of cells in S phase, with similar response amplitude. Hormonal responsiveness was heterogeneous in small clones obtained from single UMR 106-01 cells, with response frequency similar to that observed in nonsynchronized cultures. Pretreatment with either La3+, nifedipine, or pertussis toxin reduced both frequency and amplitude of PTH response in S phase to levels close to G1 phase, whereas there was no significant difference in inositol trisphosphate generated by PTH stimulation in either phase. Therefore, the heterogeneous [Ca2+]i responses of UMR 106-01 cells to hormonal stimulation is dependent on the phase of the cell cycle, rather than on genotypic heterogeneity. The switch from the G1 to the S phase mode of response is driven by active coupling between the PTH receptor and a Ca2+ channel through a pertussis toxin-sensitive G protein.
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PMID:Activation of the Ca2+ message system by parathyroid hormone is dependent on the cell cycle. 827 27

The pancreatic islets of Langerhans are targets for PTH and the action of the hormone on the islet is most likely mediated through the ability of PTH to increase cytosolic calcium ([Ca2+]i) of the islet cells. Although direct evidence for such an effect has been clearly demonstrated, the mechanisms through which the hormone exerts such an action are not elucidated. The present study examined these questions using pancreatic islets isolated from normal rats. Both 1-34 and 1-84 PTH produced a dose dependent increase in [Ca2+]i of the islets but the effect of the latter was significantly (P < 0.01) greater than that of the former. This action of PTH was significantly (P < 0.01) decreased by the use of PTH antagonist or by verapamil. The G protein activator (GTP gamma S) mimicked the effect of PTH while pertussis toxin and the G protein inhibitor (GDP beta S) significantly reduced the PTH-induced rise in [Ca2+]i. Dibutyryl cAMP, and phorbol ester 12-myristate 13 acetate increased [Ca2+]i of pancreatic islets in a dose dependent manner and the effect was inhibited (P < 0.01) by verapamil. Staurosporine inhibited the effect of TPA as well as of 1-84 PTH on [Ca2+]i of the islets. These data indicate that: (1) PTH increases [Ca2+]i of pancreatic islets, (2) this action is partly receptor mediated and is produced by activation of L-type calcium channels through stimulation of G protein(s), and (3) the rise in [Ca2+]i is due to both stimulation of cAMP generation and activation of protein kinase C.
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PMID:Parathyroid hormone raises cytosolic calcium in pancreatic islets: study on mechanisms. 838 79

PTH-related protein (PTHrP), the major mediator of hypercalcemia of malignancy, reduces tubular phosphate (Pi) reabsorption through its PTH-like renotropic actions. Another peptide detected in tumoral cells, transforming growth factor-beta (TGF beta), has been shown to considerably suppress the sodium-dependent Pi transport system present in the apical membrane of renal epithelial cells. The unexplored interactions between TGF beta and PTHrP were examined in opossum kidney (OK) cells. Using confluent OK cells, we showed that TGF beta attenuated the inhibition of Pi transport mediated by PTHrP. Similarly, 18 h TGF beta incubation resulted in a substantial reduction of the cAMP response elicited by PTHrP without apparent involvement of pertussis toxin-sensitive guanine nucleotide binding protein(s). The number of PTHrP(1-34) binding sites in TGF beta-treated cells was decreased with the affinity unchanged. Forskolin- and prostaglandin E2-stimulated cAMP productions were not significantly altered by TGF beta treatment. Therefore, TGF beta reduced Pi transport in OK cells, modulated the actions of PTHrP, and decreased its receptor number. Whether this happens in vivo is as yet unknown.
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PMID:Transforming growth factor-beta modulates the parathyroid hormone-related protein-induced responses in renal epithelial cells. 839 20

The involvement of multiple G-proteins in parathyroid hormone regulation of acid production was demonstrated in a highly enriched osteoclast population. Osteoclasts were isolated from the endosteum of 2.5 to 3-week-old chicken tibia using sequential enzymatic digestion. Single cell analysis of acid production was accomplished using microscope photometry and vital staining with acridine orange, a hydrogen ion concentration sensitive fluorescent dye. Lithium chloride, an uncoupler of G-proteins from their respective receptors, blocked parathyroid hormone stimulated production of acid. Cholera toxin, which permanently activates Gs-proteins, mimicked PTH stimulation. Pertussis toxin, which prevents receptor interaction with Gi- and Go-proteins, blocked both 10(-8) M and 10(-11) M PTH stimulated acid production, suggesting that the pertussis toxin-sensitive G-protein is utilized at both PTH concentrations. Immunoblots of osteoclast plasma membrane proteins, using a panel of antibodies generated against specific G-protein alpha subunits, revealed a 48 kDa Gs alpha, a 41 kDa Go alpha, a 34 kDa Gi alpha-3, and a unique 68 kDa G alpha subunit, with the 41 kDa and 34 kDa bands being the most intense. Immunoblots of osteoblast plasma membrane proteins had a substantially different profile with the most intense bands being a Gs alpha (48 kDa) and a Go alpha (36 and 38 kDa). The studies suggest the utilization of at least two different G-proteins in the parathyroid hormone regulation of acid formation by osteoclasts, a Gs and a pertussis toxin-sensitive G-protein (Go and/or Gi alpha-3).
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PMID:Multiple G-protein involvement in parathyroid hormone regulation of acid production by osteoclasts. 901 64

The expression of melatonin receptors (MR) of the Mel1a subtype in basolateral membrane of guinea pig kidney proximal tubule suggests that melatonin plays a role in regulating epithelial functions. To investigate the cellular basis of melatonin action on epithelia, we sought to establish an appropriate in vitro culture model. Epithelial cell lines originating from kidneys of dog (MDCK), pig (LLC-PK1), opossum (OK), and human embryo (HEK-293) were each tested for the presence of MR using 2-[125I]iodomelatonin (125I-MEL) as a radioligand. The HEK-293 cell line exhibited the highest specific 125I-MEL binding. By intermediate filament characterization, the HEK-293 cells were determined to be of epithelial origin. Binding of 125I-MEL in HEK-293 cells demonstrated saturability, reversibility, and high specificity with an equilibrium dissociation constant (Kd) value of 23.8 +/- 0.5 pM and a maximum number of binding sites (Bmax) value of 1.17 +/- 0.11 fmol/mg protein (n = 5), which are comparable with the reported Kd and Bmax values in human kidney cortex. Coincubation with GTPgammaS (10 microM) and pertussis toxin (100 ng/ml) provoked a marked decrease in binding affinity (Kd was increased by a factor of 1.5-2.0), with no significant difference in Bmax. Melatonin (1 microM) decreased the forskolin (10 microM) stimulated cAMP level by 50%. HEK-293 cells do not express dopamine D1A receptor. Following transient transfection of HEK-293 cells with human dopamine D1A receptor (hD1A-R), exposure of the cells to dopamine stimulated an increase in the level of cAMP. Similarly, transient transfection of HEK-293 cells with rat glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and PTH type 1 receptors, each resulted in an hormone inducible increase in cAMP levels. Surprisingly, only the stimulatory effect of dopamine could be inhibited by exposure to melatonin. The inhibitory effect of melatonin on dopamine D1-induced increase in cAMP was completely inhibited by pertussis toxin (100 ng/ml, 18 h). Immunoblot and immunocytochemical studies were carried out using two polyclonal antibodies raised against the extra and cytoplasmic domains of Mel1a receptor. Immunoblot studies using antibody against the cytoplasmic domain of Mel1a receptor confirmed the presence of a peptide blockable 37 kDa band in HEK-293 cells. Indirect immunofluorescent studies with both antibodies revealed staining predominantly at the cell surface, but staining with the antibody directed against the cytoplasmic domain required prior cell permeabilization. By RT-PCR, HEK-293 cells express both Mel1a and Mel1b messenger RNAs, but the messenger RNA level for Mel1b is several orders of magnitude lower than for Mel1a. We conclude that HEK-293 cells express MR predominantly of the Mel1a subtype. Our evidence suggests that one of the ways that melatonin exerts its biological function is through modulation of cellular dopaminergic responses.
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PMID:Studies of melatonin effects on epithelia using the human embryonic kidney-293 (HEK-293) cell line. 934

Many G protein-coupled receptor agonists activate p42/p44 mitogen-activated protein kinase (MAPK), using signaling pathways that are a function of receptor, G protein-coupled, and effector complement. In opossum kidney (OK) cells, activation of endogenous PTH receptors caused a time- (peak within 15-30 min, sustained for approximately 2 h) and dose-dependent (EC50 approximately 3 x 10(-10) M) activation of MAPK. Immunoblot analysis with an activation- specific MAPK antibody indicated that PTH activated both p42 and p44 MAPK. Epidermal growth factor (EGF) also activated p42 and p44MAPK in a time- (peak at 5 min, return to basal within 2 h) and dose-dependent (EC50 approximately 3 ng/ml) fashion. PTH-dependent MAPK activation was mimicked by the protein kinase C activator (PKC) phorbol myristate acetate (PMA), and the protein kinase A activators 8 bromo-cAMP (8-Br-cAMP) and forskolin but was not affected by pertussis toxin pretreatment. PMA or 8-Br-cAMP pretreatment blocked MAPK activation by reexposure to each kinase activator but caused no significant reduction in MAPK activation by PTH. MAPK activation by PTH, EGF, and 8-Br-cAMP was inhibited by the MAPK kinase inhibitor PD98059 and an EGF receptor (EGFR)-selective inhibitor tyrphostin AG1478. AG1478 also blocked MAPK activation by insulin-like growth factor-1 and platelet-derived growth factor. EGF and PTH caused time- and AG1478-sensitive phosphorylation of the EGFR, but EGFR desensitization did not affect MAPK activation by PTH. EGF, PMA, and low doses of PTH (10(12) to 10(-9) M) stimulated while 8-Br-cAMP and high doses of PTH (10(-8) to 10(-6) M) inhibited [3H]thymidine uptake. These data demonstrate that PTH activates MAPK and suggest that PKC, protein kinase A, and the EGFR play roles in PTH signaling. The biphasic effect of PTH on DNA synthesis suggests that MAPK activation by the hormone leads to distinct cellular responses.
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PMID:Parathyroid hormone activates mitogen-activated protein kinase in opossum kidney cells. 1057 43


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