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Pinheiro AR, Paramos-de-Carvalho D, Certal M, Costa C, Magalhães-Cardoso MT, Ferreirinha F, Costa MA, Correia-de-Sá P. Bradykinin-induced Ca2+ signaling in human subcutaneous fibroblasts involves ATP release via hemichannels leading to P2Y12 receptors activation. Cell Commun Signal 2013; 11:70. [PMID: 24047499 PMCID: PMC3848849 DOI: 10.1186/1478-811x-11-70] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 09/12/2013] [Indexed: 12/31/2022] Open
Abstract
Background Chronic musculoskeletal pain involves connective tissue remodeling triggered by inflammatory mediators, such as bradykinin. Fibroblast cells signaling involve changes in intracellular Ca2+ ([Ca2+]i). ATP has been related to connective tissue mechanotransduction, remodeling and chronic inflammatory pain, via P2 purinoceptors activation. Here, we investigated the involvement of ATP in bradykinin-induced Ca2+ signals in human subcutaneous fibroblasts. Results Bradykinin, via B2 receptors, caused an abrupt rise in [Ca2+]i to a peak that declined to a plateau, which concentration remained constant until washout. The plateau phase was absent in Ca2+-free medium; [Ca2+]i signal was substantially reduced after depleting intracellular Ca2+ stores with thapsigargin. Extracellular ATP inactivation with apyrase decreased the [Ca2+]i plateau. Human subcutaneous fibroblasts respond to bradykinin by releasing ATP via connexin and pannexin hemichannels, since blockade of connexins, with 2-octanol or carbenoxolone, and pannexin-1, with 10Panx, attenuated bradykinin-induced [Ca2+]i plateau, whereas inhibitors of vesicular exocytosis, such as brefeldin A and bafilomycin A1, were inactive. The kinetics of extracellular ATP catabolism favors ADP accumulation in human fibroblast cultures. Inhibition of ectonucleotidase activity and, thus, ADP formation from released ATP with POM-1 or by Mg2+ removal from media reduced bradykinin-induced [Ca2+]i plateau. Selective blockade of the ADP-sensitive P2Y12 receptor with AR-C66096 attenuated bradykinin [Ca2+]i plateau, whereas the P2Y1 and P2Y13 receptor antagonists, respectively MRS 2179 and MRS 2211, were inactive. Human fibroblasts exhibited immunoreactivity against connexin-43, pannexin-1 and P2Y12 receptor. Conclusions Bradykinin induces ATP release from human subcutaneous fibroblasts via connexin and pannexin-1-containing hemichannels leading to [Ca2+]i mobilization through the cooperation of B2 and P2Y12 receptors.
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Affiliation(s)
- Ana Rita Pinheiro
- Laboratório de Farmacologia e Neurobiologia, Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar da Universidade do Porto (ICBAS-UP), Rua Jorge Viterbo Ferreira 228, Edif, 2 Piso 4, Porto 4050-313, Portugal.
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2
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Improta-Brears T, Whorton AR, Codazzi F, York JD, Meyer T, McDonnell DP. Estrogen-induced activation of mitogen-activated protein kinase requires mobilization of intracellular calcium. Proc Natl Acad Sci U S A 1999; 96:4686-91. [PMID: 10200323 PMCID: PMC16393 DOI: 10.1073/pnas.96.8.4686] [Citation(s) in RCA: 254] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Estrogens and growth factors such as epidermal growth factor (EGF) act as mitogens promoting cellular proliferation in the breast and in the reproductive tract. Although it was considered originally that these agents manifested their mitogenic actions through separate pathways, there is a growing body of evidence suggesting that the EGF and estrogen-mediated signaling pathways are intertwined. Indeed, it has been demonstrated recently that 17beta-estradiol (E2) can induce a rapid activation of mitogen-activated protein kinase (MAPK) in mammalian cells, an event that is independent of both transcription and protein synthesis. In this study, we have used a pharmacological approach to dissect this novel pathway in MCF-7 breast cancer cells and have determined that in the presence of endogenous estrogen receptor, activation of MAPK by E2 is preceded by a rapid increase in cytosolic calcium. The involvement of intracellular calcium in this process was supported by the finding that the presence of EGTA and Ca2+-free medium did not affect the activation of MAPK by E2 and, additionally, that this response was blocked by the addition of the intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate. Cumulatively, these data indicate that the estrogen receptor, in addition to functioning as a transcription factor, is also involved, through a nongenomic mechanism, in the regulation of both intracellular calcium homeostasis and MAPK-signaling pathways. Although nongenomic actions of estrogens have been suggested by numerous studies in the past, the ability to link estradiol and the estrogen receptor to a well defined signaling pathway strongly supports a physiological role for this activity.
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Affiliation(s)
- T Improta-Brears
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
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3
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Baldo A, Sniderman AD, St Luce S, Zhang XJ, Cianflone K. Signal transduction pathway of acylation stimulating protein: involvement of protein kinase C. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)39728-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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4
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Tippmer S, Quitterer U, Kolm V, Faussner A, Roscher A, Mosthaf L, Müller-Esterl W, Häring H. Bradykinin induces translocation of the protein kinase C isoforms alpha, epsilon, and zeta. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 225:297-304. [PMID: 7925449 DOI: 10.1111/j.1432-1033.1994.00297.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bradykinin exerts a broad spectrum of cellular effects on different tissues. It is believed that these effects are predominantly mediated by the recently cloned B2 receptor. The mechanism of post-receptor signal transduction is not known in detail. Involvement of protein kinase C (PKC) was suggested and activation of the classical PKC isoforms alpha and beta was recently demonstrated. The aim of the present study was to investigate whether the B2 receptor also activates new (delta, epsilon) and atypical (zeta) PKC isoforms. To investigate this, chinese hamster ovary (CHO) cells, stably transfected with human B2 receptor, were used. In these cells the PKC isoforms alpha, delta, epsilon and zeta were detected by immunoblotting with specific antibodies. To monitor hormone-induced PKC translocation plasma membranes were prepared. Stimulation of the cells with bradykinin resulted in a rapid (30-60 s) translocation of the PKC isoforms alpha, epsilon, and zeta. Translocation of PKC delta was not detected. The effect of bradykinin was reduced by simultaneous addition of the receptor antagonist HOE 140, a bradykinin-related decapeptide. The data show that the B2 receptor in this cell model is able to activate, in addition to the classical PKC isoform alpha, the new PKC isoform epsilon and the atypical PKC isoform zeta. To test whether these effects are as well observed in a non-transfected cell, the experiments were repeated in human foreskin fibroblasts which naturally express high levels of B2 receptors. In this cell system similar results on PKC alpha, epsilon, and zeta were observed, suggesting that all three PKC isoforms are involved in signal transduction of the B2 receptor.
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Affiliation(s)
- S Tippmer
- Institut für Diabetesforschung, München, Germany
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5
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Kiehne K, Rozengurt E. Synergistic stimulation of DNA synthesis by bradykinin and vasopressin in Swiss 3T3 cells. J Cell Physiol 1994; 160:502-10. [PMID: 8077288 DOI: 10.1002/jcp.1041600313] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Vasopressin and bradykinin bind to receptors coupled to GTP-binding proteins and rapidly induce polyphosphoinositide breakdown leading to Ca2+ mobilization and activation of protein kinase C. Both peptides are known to induce mitogenesis in the presence of growth factors that act through receptors with intrinsic tyrosine kinase activity. Surprisingly, addition of a combination of vasopressin and bradykinin to Swiss 3T3 cells synergistically stimulates DNA synthesis in the absence of any other growth factors. This effect is induced at nanomolar concentrations of the peptides and could be inhibited by addition of specific receptor antagonists or broad spectrum neuropeptide antagonists. Bradykinin, which stimulates transient activation of protein kinase C, induces DNA synthesis in synergy with substances that cause long-term activation of protein kinase C, like vasopressin or phorbol 12,13-dibutyrate. Down-regulation of protein kinase C inhibited the induction of mitogenesis by the combination of vasopressin and bradykinin, thus demonstrating the importance of long-term activation of this enzyme for DNA synthesis. Analysis of tyrosine phosphorylated proteins of M(r) = 110,000-130,000 and M(r) = 70,000-80,000 revealed a biphasic response after stimulation with bradykinin, whereas the response induced by vasopressin declined after the initial maximum. The combination of bradykinin with vasopressin caused an enhanced and prolonged increase in tyrosine phosphorylation of these proteins as compared with the individual peptides. Inhibition of tyrosine phosphorylation by tyrphostin was paralleled by inhibition of DNA synthesis. Together, these results demonstrate synergistic stimulation of DNA synthesis by bradykinin and vasopressin via prolonged stimulation of multiple signaling pathways and imply that the interactive effects of Ca(2+)-mobilizing peptides on mitogenesis may be more general than previously thought.
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Affiliation(s)
- K Kiehne
- Imperial Cancer Research Fund, London, United Kingdom
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6
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Ozeki T, Osada K, Seishima M, Mori S, Nozawa Y. Decreased bradykinin binding sites in fibroblasts from progressive systemic scleroderma. Arch Dermatol Res 1994; 286:133-6. [PMID: 8002664 DOI: 10.1007/bf00374207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The numbers of bradykinin receptors (BK-R) in cultured dermal fibroblasts from patients with progressive systemic sclerosis (PSS) and from healthy controls were measured using a receptor binding assay. The numbers of BK-R were significantly fewer in PSS fibroblasts than in control fibroblasts (P < 0.02). However, no differences in affinity were observed in BK-R between PSS and control fibroblasts. The BK-R mRNA levels were determined in PSS and control fibroblasts by Northern blot hybridization using BK-R cDNA, but no significant differences were found. These findings suggest that the decrease in BK-R in PSS fibroblasts might occur during a posttranslational step.
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Affiliation(s)
- T Ozeki
- Department of Dermatology, Gifu University School of Medicine, Japan
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7
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Fletcher JE, Jiang MS. Possible mechanisms of action of cobra snake venom cardiotoxins and bee venom melittin. Toxicon 1993; 31:669-95. [PMID: 8342168 DOI: 10.1016/0041-0101(93)90375-s] [Citation(s) in RCA: 116] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cobra snake venom cardiotoxins and bee venom melittin share a number of pharmacological properties in intact tissues including hemolysis, cytolysis, contractures of muscle, membrane depolarization and activation of tissue phospholipase C and, to a far lesser extent, an arachidonic acid-associated phospholipase A2. The toxins have also been demonstrated to open the Ca2+ release channel (ryanodine receptor) and alter the activity of the Ca(2+)+Mg(2+)-ATPase in isolated sarcoplasmic reticulum preparations derived from cardiac or skeletal muscle. However, a relationship of these actions in isolated organelles to contracture induction has not yet been established. The toxins also bind to and, in some cases, alter the function of a number of other proteins in disrupted tissues. The most difficult tasks in understanding the mechanism of action of these toxins have been dissociating the primary from secondary effects and distinguishing between effects that only occur in disrupted tissues and those that occur in intact tissue. The use of cardiotoxin and melittin fractions contaminated with trace ('undetectable') amounts of venom-derived phospholipases A2 has continued to be common practice, despite the problems associated with the synergism between the toxins and enzymes and the availability of methods to overcome this problem. With adequate precautions taken with regard to methodology and interpretation of results, the cobra venom cardiotoxins and bee venom melittin may prove to be useful probes of a number of cell processes, including lipid metabolism and Ca2+ regulation in skeletal and cardiac muscle.
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Affiliation(s)
- J E Fletcher
- Department of Anesthesiology, Hahnemann University, Philadelphia, PA 19102-1192
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8
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Abstract
Lithium interferes with the responses of neural and secretory cells to calcium-mobilizing agonists by blocking the generation of phospholipase C-dependent second messengers. However, the mechanism by which lithium stimulates the proliferation of other cells in response to agonists that do not activate phospholipase C remains obscure. We investigated the pathways that mediate the mitogenic action of lithium on WI-38 cells in a defined, serum-free medium. Lithium, like dexamethasone (Dex), potentiated DNA synthesis in response to the combination of insulin+epidermal growth factor (EGF) (+50%), but not in response to either growth factor alone or with Dex. As in the case of Dex, lithium could be added as late as 8 h following stimulation of quiescent cells by insulin+EGF without loss of potentiating activity. While DNA synthesis in control cultures was essentially complete by 24 h, lithium and Dex stimulated "late" DNA synthesis (24-30 h) 10-fold and 5-fold, respectively. The potentiating activity of Dex, but not that of lithium, was blocked by the specific glucocorticoid receptor antagonist, RU486. Both lithium and Dex stimulated log-phase growth, but only Dex increased saturation density. These data indicate that both lithium and Dex recruit into the cell cycle a subpopulation of cells with a longer mean prereplicative phase (G1). The effect of lithium on DNA synthesis in WI-38 cells may be mediated by the glucocorticoid response pathway at some point distal to activation of the glucocorticoid receptor, or by an independent mechanism that can be switched on late in G1.
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Affiliation(s)
- T Sorger
- Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104
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9
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Byron KL, Babnigg G, Villereal ML. Bradykinin-induced Ca2+ entry, release, and refilling of intracellular Ca2+ stores. Relationships revealed by image analysis of individual human fibroblasts. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)48466-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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10
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Villereal ML, Byron KL. Calcium signals in growth factor signal transduction. Rev Physiol Biochem Pharmacol 1992; 119:67-121. [PMID: 1604156 DOI: 10.1007/3540551921_4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is a substantial amount of information which has been obtained concerning the effects of growth factors on [Ca2+]i in proliferating cells. A number of different mitogens are known to induce elevations in [Ca2+]i and some characterization of the Ca2+ response to different classes of mitogens has been obtained. In addition, much is known about whether the Ca2+ response to a particular growth factor occurs as the result of an influx of external Ca2+ or a mobilization of internal Ca2+ stores. In addition, a considerable amount of information is available on the mechanism by which the Ins(1,4,5)P3-sensitive internal Ca2+ store takes up and releases Ca2+. However, there is still a large deficiency in our information concerning other Ca2+ stores in proliferating cells as well as in our knowledge of the mechanisms for regulating Ca2+ entry pathways. Much more data addressing these issues exists for other types of agonist-stimulated cells, and we have discussed much of it in this review article. While the wealth of data in nonproliferating cells provides some indications of what mechanisms might be involved in the growth factor-induced changes in [Ca2+]i, it is clear that much work must be done in proliferating cells to fully understand how external factors such as growth factors control [Ca2+]i. In addition, much work remains to be done in identifying the mechanisms for the internal control of [Ca2+]i as cells move through the cell cycle and in identifying the role that these changes in [Ca2+]i may play throughout the cell cycle.
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Affiliation(s)
- M L Villereal
- Department of Pharmacological and Physiological Sciences, University of Chicago, IL 60637
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11
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Dill RE, Farmer GR. Phenytoin-induced DNA synthesis and inositol 1,4,5-trisphosphate formation in L-929 fibroblasts. EXPERIENTIA 1991; 47:728-30. [PMID: 2065771 DOI: 10.1007/bf01958828] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Culture of L-929 fibroblasts in the presence of phenytoin (2.5-5.0 micrograms/ml) increased DNA synthesis, as indicated by increased [3H]thymidine uptake, while a higher dose (20 micrograms/ml) inhibited DNA synthesis. In like manner, a low dose of phenytoin (5.0 micrograms/ml) was effective in increasing inositol 1,4,5-trisphosphate formation while a higher dose (10 micrograms/ml) tended to inhibit this activity. These data suggest that the formation of inositol phosphate second messengers may play a role in phenytoin-induced fibroblast proliferation and connective tissue growth.
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Affiliation(s)
- R E Dill
- Department of Anatomy, Baylor College of Dentistry, Dallas, Texas 75246
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12
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Godin C, Smith AD, Riley PA. Bradykinin stimulates DNA synthesis in competent Balb/c 3T3 cells and enhances inositol phosphate formation induced by platelet-derived growth factor. Biochem Pharmacol 1991; 42:117-22. [PMID: 2069585 DOI: 10.1016/0006-2952(91)90689-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Both platelet-derived growth factor (PDGF) and bradykinin were found to induce a growth response in Balb/c 3T3 cells. However, whereas PDGF brought about a five-fold increase in the incorporation of [3H]thymidine into DNA, the response to bradykinin was never more than 50%. When bradykinin was present simultaneously with sub-optimal concentrations of PDGF the response was about 15% greater than with PDGF alone. In contrast, if the cells were made competent by a 5 hr preincubation with PDGF which was then washed away, subsequent addition of bradykinin induced a more than two-fold increase in incorporation of [3H]thymidine into DNA compared with competent cells subsequently incubated with serum-free medium alone. Bradykinin also acted synergistically with insulin when the two agents were added simultaneously to competent cells. PDGF induced marked increases in the concentration of inositol phosphates at 30 min after stimulation, but by this time point any effect of bradykinin had disappeared. However, the simultaneous presence of PDGF and bradykinin induced increases at 30 min that were 50-100% greater than with PDGF alone. It is concluded that the pathways by which PDGF and bradykinin initiate a growth response in BALB/c 3T3 cells only partly overlap. Their actions on the synthesis of inositol phosphates exhibit distinctive temporal characteristics, but can be co-operative at 30 min and at earlier time intervals. This effect was found to be time-dependent, and developed over the first 5 min.
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Affiliation(s)
- C Godin
- Department of Chemical Pathology, University College & Middlesex School of Medicine, London, U.K
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13
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Seishima M, Kudo Y, Nagao S, Mori S, Nozawa Y. Alterations in intracellular calcium transients of fibroblasts from progressive systemic sclerotic patients: a digital imaging microscopic study. Arch Dermatol Res 1991; 283:96-9. [PMID: 2069418 DOI: 10.1007/bf00371616] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Intracellular Ca2+ concentrations ([Ca2+]i) in cultured skin fibroblasts from normal subjects and progressive systemic sclerosis (PSS) patients were determined by using Fura-2 and fluorescent videomicroscopy. With the exception of fibroblasts from one PSS patient showing a higher [Ca2+]i, no significant difference was observed in resting [Ca2+]i between the two groups of fibroblasts. Bradykinin (BK) (10 microM) induced a transient [Ca2+]i increase in normal fibroblasts, whereas the BK-induced [Ca2+]i increase was reduced or not detectable in PSS fibroblasts. Removal of extracellular Ca2+ did not eliminate the BK-induced [Ca2+]i increase in normal fibroblasts. These findings suggest that BK stimulates Ca2+ release from intracellular stores in human fibroblasts, and also that the BK-mediated Ca2+ release is impaired in PSS fibroblasts.
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Affiliation(s)
- M Seishima
- Department of Dermatology, Gifu University School of Medicine, Japan
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14
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Etscheid BG, Albert KA, Villereal ML, Palfrey HC. Transduction of the bradykinin response in human fibroblasts: prolonged elevation of diacylglycerol level and its correlation with protein kinase C activation. CELL REGULATION 1991; 2:229-39. [PMID: 1907204 PMCID: PMC361758 DOI: 10.1091/mbc.2.3.229] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Stimulation of quiescent human fibroblasts with the peptide mitogen bradykinin (BK) led to a biphasic elevation in cellular 1,2-diacylglycerol (DAG), as estimated by either measurement of total DAG mass or [3H]arachidonate incorporation. A rapid initial transient that peaked 15 s after BK addition was followed by a decline to near basal levels then a second rise to a plateau phase during which DAG levels remained elevated for less than or equal to 45 min. The source of the initial DAG transient appeared to be primarily polyphosphoinositides as these phospholipids were rapidly hydrolyzed after BK addition. This transient correlates well temporally with previous observations of the kinetics of inositol trisphosphate accumulation and intracellular free [Ca2+] observed in the same cells. Cultures preincubated with [3H]myristic acid incorporated label predominantly into the phosphatidylcholine (PC) pool. Subsequent addition of BK under these conditions caused only a relatively slow accumulation of [3H]DAG to a plateau level, without an initial transient. Together with the observation that PC was found to decrease upon BK stimulation, these observations suggest that the late phase of DAG accumulation may involve breakdown of other phospholipids including PC. To investigate the consequences of DAG elevation we examined the phosphorylation of an acidic 80 kDa protein, whose phosphorylation is solely dependent on the activation of protein kinase C (PK-C). The 80 kDa fibroblast protein could be immunoprecipitated by an antibody to bovine brain "myristoylated and alanine-rich C-kinase substrate" (MARCKS) and phosphopeptide maps of brain and fibroblast MARCKS were similar. Stimulation of [32P]-prelabeled fibroblasts with serum, BK, vasopressin, or 12-O-tetradecanoyl phorbol acetate, but not epidermal growth factor or calcium ionophores, resulted in the rapid phosphorylation of MARCKS. With BK or serum this phosphorylation showed an initial transient peak at less than 1 min then rose again to a plateau level that was sustained for less than or equal to 45 min. Removal of BK resulted in a rapid decline in MARCKS phosphorylation. These studies show that the biphasic DAG signal in BK-stimulated human fibroblasts correlates well with the state of activation of PK-C. However, the persistent activation of PK-C does not appear to require continued high levels of Ca2+.
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Affiliation(s)
- B G Etscheid
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637
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15
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Huang HM, Toral-Barza L, Gibson GE. Interactions between inositol phosphates and cytosolic free calcium following bradykinin stimulation in cultured human skin fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1091:409-16. [PMID: 2001422 DOI: 10.1016/0167-4889(91)90208-f] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The inositol triphosphate (IP3) that results from hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) is generally accepted to be responsible for the mobilization of intracellular calcium. However, some studies suggest that low concentrations of agonists elevate cytosolic free calcium concentration ([Ca2+]i) without IP3 formation. Thus, in the present studies, a comparison of the temporal response of inositol phosphates (IP3, IP2 and IP) and [Ca2+]i to a wide range of bradykinin concentrations was used to examine the relation of these two signal transduction events in cultured human skin fibroblasts (GM3652). In addition, the effects of alterations in internal or external calcium on the response of these second messengers to bradykinin were determined. Bradykinin stimulated accumulation of inositol phosphates and a rise of [Ca2+]i in a time- and dose-dependent manner. Decreasing the bradykinin concentration from 1 microM to 0.1 microM increased the time until the IP3 peak, and when the bradykinin concentration was reduced to 0.01 microM IP3 was not detected. [Ca2+]i was examined under parallel conditions. As the bradykinin concentration was reduced from 1 microM to 0.01 microM, the time to reach the peak of [Ca2+]i increased progressively, but the magnitude of the peak was unaltered. These two second messengers were variably dependent on external calcium. Although the bradykinin-stimulated initial spike of [Ca2+]i did not depend on extracellular calcium, the subsequent sustained levels of [Ca2+]i were abolished in calcium free medium. The bradykinin-stimulated inositol phosphate formation was not dependent on the extracellular calcium nor on the elevation of [Ca2+]i that was produced with Br-A23187. These results demonstrate that bradykinin-induced IP3 formation can be independent of [Ca2+]i and of external calcium, whereas changes in [Ca2+]i are partially dependent on external calcium.
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Affiliation(s)
- H M Huang
- Cornell University Medical College, Burke Rehabilitation Center, White Plains, NY 10605
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16
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Suffys P, Beyaert R, De Valck D, Vanhaesebroeck B, Van Roy F, Fiers W. Tumour-necrosis-factor-mediated cytotoxicity is correlated with phospholipase-A2 activity, but not with arachidonic acid release per se. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 195:465-75. [PMID: 1847684 DOI: 10.1111/j.1432-1033.1991.tb15727.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
L929, a murine fibrosarcoma cell line highly sensitive to the anti-proliferative and cytotoxic action of tumour necrosis factor (TNF), was used as a target cell in our studies. We [Suffys et al. (1987) Biochem. Biophys. Res. Commun. 149, 735-743], as well as others, have previously provided evidence that a phospholipase (PL), most probably a PL-A2-type enzyme, is likely to be involved in TNF-mediated cell killing. We now further document this conclusion and provide suggestive evidence that the enzyme activity specifically involved in TNF cytotoxicity differs from activities associated with the eventual cell death process itself or with non-toxic serum treatment. We also show that the 5,8,11,14-icosatetraenoic acid (arachidonic acid, delta 4 Ach) released by PL, and possibly metabolized, is unlikely to be a key mediator of the TNF-mediated cytotoxicity. These conclusions are based on the following experimental findings. 1. TNF treatment of cells, prelabelled for 24 h with [3H] delta 4Ach or [14C] delta 3Ach (delta 3Ach identical to 5,8,11-icosatrienoic acid) resulted in an early, time-dependent and concentration-dependent release of radioactivity in the supernatant preceding actual cell death. The extent of this response was moderate, albeit reproducible and significant. Analysis of the total lipid fraction from cells plus supernatant revealed that only release of arachidonic acid from phospholipids, but not its metabolization was induced by TNF. However, the release of less unsaturated fatty acids, such as linoleic acid (Lin) or palmitic acid (Pam), was not affected during the first hours after TNF addition. 2. An L929 subclone, selected for resistance to TNF toxicity, was found to be defective in TNF-induced delta 4Ach libration. 3. Interleukin-1 (IL1) was not cytotoxic for L929 and did not induce release of delta 4Ach. 4. Release of delta 4Ach was not restricted to TNF; the addition of serum to the cells also induced release of fatty acids into the medium. In this case, however, there was no specificity, as all fatty acids tested, including Lin and Pam, were released. 5. Inhibition of PL-A2 activity by appropriate drugs markedly diminished TNF-induced delta 4Ach release and resulted also in a strong decrease in TNF-induced cytotoxicity. 6. Other drugs, including serine protease inhibitors, which strongly inhibit TNF-induced cytotoxicity, also decreased the TNF-induced delta 4Ach release, whereas LiCl potentiated both TNF-mediated effects. 7. Protection of cells against TNF toxicity by means of various inhibitors was not counteracted by addition of exogenous fatty acids, including delta 4Ach.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- P Suffys
- Laboratory of Molecular Biology, State University of Gent, Belgium
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Etscheid BG, Jamieson GA, Toscas K, Villereal ML. Loss of bradykinin receptors and TPA-stimulated Na+ influx in SV40-transformed WI-38 cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:C549-56. [PMID: 2171345 DOI: 10.1152/ajpcell.1990.259.4.c549] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Mitogenic stimulation of Na(+)-H+ exchange activity, as defined by the level of 5-(N,N-hexamethylene)amiloride (HMA)-sensitive Na+ influx, was compared in WI-38 and SV40 virus-transformed WI-38 fibroblasts. Serum or bradykinin dramatically stimulated HMA-sensitive Na+ influx in WI-38 cells, whereas in SV40-transformed WI-38 cells, serum, but not bradykinin, produced a large increase in HMA-sensitive Na+ influx. This lack of a bradykinin response was traced to a dramatic reduction in the number of bradykinin receptors, from 470 fmol/mg protein in WI-38 cells to 29 fmol/mg protein in the SV40-transformed WI-38 cells. Transformation of WI-38 cells with SV40 virus also altered the mechanism by which HMA-sensitive Na+ influx is stimulated. In WI-38 cells, 12-O-tetradecanoylphorbol 13-acetate (TPA) dramatically stimulated HMA-sensitive Na+ influx. In SV40-transformed WI-38 cells, TPA alone had no effect on HMA-sensitive influx and inhibited serum-stimulated HMA-sensitive Na+ influx. Down-regulation of protein kinase C activity decreased serum- and TPA-stimulated HMA-sensitive Na+ influx in the WI-38 cells and relieved the TPA inhibition of serum-stimulated HMA-sensitive Na+ influx in the SV40-transformed WI-38 cells.
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Affiliation(s)
- B G Etscheid
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637
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18
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Hendey B, Mamrack MD, Putnam RW. Thrombin induces a calcium transient that mediates an activation of the Na+/H+ exchanger in human fibroblasts. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)47147-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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19
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Etscheid BG, Villereal ML. Coupling of bradykinin receptors to phospholipase C in cultured fibroblasts is mediated by a G-protein. J Cell Physiol 1989; 140:264-71. [PMID: 2545733 DOI: 10.1002/jcp.1041400211] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In cultured foreskin fibroblasts, bradykinin stimulates inositol phosphate generation, arachidonic acid release, and Na+/H+ exchange, with doses of 1-3 nM yielding half-maximal stimulation. Binding of 3H-bradykinin to these cells demonstrates a single receptor site with a Kd of 2.0 nM and a Bmax of 91 fmoles/mg protein. Bradykinin analogs of the B2 type inhibit this binding. GTP synergizes with bradykinin to stimulate phosphatidylinositol turnover in permeabilized fibroblasts and GTP-gamma-S decreases the Bmax of bradykinin binding to fibroblast membranes, indicating that a G-protein couples the receptor to phospholipase C. Pretreatment of fibroblasts with either cholera or pertussis toxin enhances bradykinin stimulation of inositol phosphate accumulation.
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Affiliation(s)
- B G Etscheid
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637
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20
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Jamieson GA, Mayforth RD, Villereal ML, Sukhatme VP. Multiple intracellular pathways induce expression of a zinc-finger encoding gene (EGR1): relationship to activation of the Na/H exchanger. J Cell Physiol 1989; 139:262-8. [PMID: 2541139 DOI: 10.1002/jcp.1041390207] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Intracellular pathways that rapidly stimulate the expression of a mitogen-inducible, zinc-finger encoding gene, EGR1 (Sukhatme et al., Cell 53:37-43), have been characterized in two human fibroblasts strains (WI-38 and HSWP). Serum and epidermal growth factor (EGF) were each found to strongly stimulate EGR1 expression in both cell types. Comparably high levels of expression could also be induced by treatment with the phorbol ester TPA. In cells rendered deficient in PK-C, serum and EGF were each still capable of inducing high levels of EGR1 mRNA, demonstrating that additional non-protein kinase C pathways are capable of stimulating EGR1 expression. In both fibroblasts strains, stimulation of EGR1 expression by all these agents exhibited rapid, transient kinetics and could be superinduced if protein synthesis was inhibited through the addition of cycloheximide. Finally, various agents, known to stimulate/inhibit the activation of another early mitogenic response, the activation of Na/H exchange, were analyzed for their effect on EGR1 expression. Interestingly bradykinin, vasopressin, and Ca ionophores, which dramatically stimulate Na/H exchange, were only weak stimulants of EGR1 expression. Conversely, EGF, which stimulates Na/H exchange poorly, strongly activated EGR1 expression. Hence while EGR1 expression could be triggered by multiple intracellular pathways, its expression does not appear to require the prior activation of Na/H exchange.
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Affiliation(s)
- G A Jamieson
- Department of Pharmacological, Howard Hughes Medical Research Institute, University of Chicago, Illinois 60637
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21
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London FS, Caamano-Haigh R, Chepenik KP. Dexamethasone does not interfere with hormone-sensitive PI hydrolysis. TERATOLOGY 1989; 39:121-6. [PMID: 2784594 DOI: 10.1002/tera.1420390204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Serum, but not epidermal growth factor (EGF), stimulated the release of radiolabeled inositol phosphates from human embryo palate mesenchyme (HEPM) cells prelabeled with [3H]-myoinositol. Pretreatment of cells with 10(-6) M dexamethasone (DEX) for 48 h had no effect on the release of inositol phosphates in response to serum. Furthermore, although treatment of the glucocorticoid-sensitive A/J strain of mouse embryo palate mesenchyme (MEPM) cells with 10(-6) M DEX inhibited their proliferation by 40%, it had no effect on the activity of phospholipase(s) C. However, DEX did enhance the incorporation of [3H]-myoinositol into membrane lipids. We interpret these data to mean that 1) serum factors enhance metabolism of inositol lipids in HEPM cells, 2) DEX does not interfere with the primary events by which agonists utilize metabolism of inositol lipids as a mechanism for transmembrane signaling, and 3) DEX may affect synthesis of phosphoinositides, as reported by Grove et al. (Biochem. Biophys. Res. Commun. 110:200-207, 1983; J. Craniofac. Genet. Dev. Biol. Suppl. 2:285-292, 1986).
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Affiliation(s)
- F S London
- Department of Anatomy, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
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22
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Smith JB, Dwyer SD, Smith L. Decreasing Extracellular Na+ Concentration Triggers Inositol Polyphosphate Production and Ca2+ Mobilization. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)85017-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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23
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Fu T, Okano Y, Nozawa Y. Bradykinin-induced generation of inositol 1,4,5-trisphosphate in fibroblasts and neuroblastoma cells: effect of pertussis toxin, extracellular calcium, and down-regulation of protein kinase C. Biochem Biophys Res Commun 1988; 157:1429-35. [PMID: 2849940 DOI: 10.1016/s0006-291x(88)81035-0] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The net content of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] was measured in bradykinin (BK)-stimulated NIH3T3 fibroblasts and neuroblastoma-glioma hybrid cells (NG108-15). BK-mediated production of Ins(1,4,5)P3 was not affected by replacing the medium with Ca2+-free medium, but addition of EGTA (1mM) to Ca2+-free medium markedly prevented production of Ins(1,4,5)P3. Although pertussis toxin (PT) treatment caused ADP-ribosylation in both NIH3T3 cells and NG108-15 cells, the BK-induced Ins(1,4,5)P3 formation was considerably reduced in the former cells but not in the latter cells, suggesting that PT-sensitive and PT-insensitive GTP-binding proteins are involved in phosphoinositide phospholipase C (PI-PLC) activation in fibroblasts and neuroblastoma cells, respectively. In NG108-15 cells down-regulated in protein kinase C (PKC) by long-term exposure to phorbol 12-myristate 13-acetate (PMA), BK-stimulated Ins(1,4,5)P3 accumulation was significantly enhanced compared to control cells.
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Affiliation(s)
- T Fu
- Department of Biochemistry, Gifu University School of Medicine, Japan
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24
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Jamieson GA, Etscheid BG, Muldoon LL, Villereal ML. Effects of phorbol ester on mitogen and orthovanadate stimulated responses of cultured human fibroblasts. J Cell Physiol 1988; 134:220-8. [PMID: 3346337 DOI: 10.1002/jcp.1041340207] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mitogenic stimulation of quiescent human fibroblasts (HSWP) with serum or a mixture of growth factors (consisting of vasopressin, bradykinin, EGF, and insulin) stimulates the release of inositol phosphates, mobilization of intracellular Ca, activation of Na/H exchange and subsequent incorporation of [3H]-thymidine. We have determined previously that pretreatment with the tumor-promoting phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) inhibits mitogen-stimulated Na influx in HSWP cells. We report herein that TPA pretreatment also substantially inhibits the mitogen-stimulated release of inositol phosphates in HSWP cells. Half maximal inhibition of mitogen-stimulated inositol phosphate release occurs at 1-2 nM TPA. Treatment of cells with TPA alone has no effect on inositol phosphate release. The effect of TPA pretreatment on inositol phosphate release induced by individual growth factors has also been determined. Orthovanadate, reported by Cassel et al. (1984) to increase Na/H exchange in A431 cells, has been demonstrated to stimulate both Na influx and inositol phosphate release in HSWP cells. TPA pretreatment also inhibits both orthovanadate-stimulated inositol phosphate release and Na influx. In addition, orthovanadate was determined to increase intracellular Ca activity by mobilizing intracellular calcium stores, as determined with the fluorescent intracellular calcium probe fura-2. TPA pretreatment blocks orthovanadate stimulated mobilization of intracellular Ca stores. It appears clear that in HSWP cells pretreatment of cells with phorbol ester is capable of artificially desensitizing the early cellular responses to mitogenic stimuli (growth factors, orthovanadate) by blocking the signal transduction mechanism involved at a point prior to the release of inositol phosphates. We hypothesize that in HSWP cells the normal desensitization of both inositol phosphate release and Na/H exchange is mediated via activation of protein kinase C subsequent to the stimulus-mediated activation of phospholipase C and release of protein kinase C activator diacylglycerol. However it is interesting to note that TPA-mediated inhibition of these early responses in HSWP cells does not inhibit their ability to be stimulated to incorporate [3H]-thymidine.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- G A Jamieson
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637
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Hayden JH. Microtubule-associated organelle and vesicle transport in fibroblasts. CELL MOTILITY AND THE CYTOSKELETON 1988; 10:255-62. [PMID: 3180246 DOI: 10.1002/cm.970100130] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Allen Video-enhanced contrast/differential interference contrast (AVEC-DIC) microscopy was used in conjunction with video intensification immunofluorescence microscopy to demonstrate that organelles and vesicle (particles) can move in either direction along microtubular linear elements in fibroblasts [Hayden et al., 1983]. Since it is not possible to determine the number of microtubules making up a linear element with light microscopy alone, AVEC-DIC microscopy was used in conjunction with whole-mount electron microscopy to show bidirectional transport along a single microtubule [Hayden and Allen, 1984]. These studies demonstrate that the structural polarity of the microtubule does not determine the direction of particle motion, and since dynein is an asymetric molecule, a simple microtubule-dynein-particle hypothesis cannot explain bidirectional transport along a single microtubule. Very little is known about regulation of particle transport in most cell types. Human embryonic lung fibroblasts grown on glass coverslips were serum-deprived for 24 hours and re-fed with serumless medium; the particle translocations/5 minutes were then determined. The cells were then re-fed with either serumless medium, serum-containing medium, or serumless medium containing some bioactive factor, and the particle translocations/5 minutes were again determined for the same cells. Medium containing 10% fetal bovine serum inhibited particle translocation by 51.8%. Of the bioactive factors tested, only vasopressin produced a significant reduction in particle translocations (38%). This suggests that protein kinase C or calcium/calmodulin kinase could be involved in regulating particle transport.
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Muldoon LL, Jamieson GA, Kao AC, Palfrey HC, Villereal ML. Mitogen stimulation of Na+-H+ exchange: differential involvement of protein kinase C. THE AMERICAN JOURNAL OF PHYSIOLOGY 1987; 253:C219-29. [PMID: 3039853 DOI: 10.1152/ajpcell.1987.253.2.c219] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The mitogen-induced activation of Na+-H+ exchange was investigated in two cultured human fibroblast strains (HSWP and WI-38 cells) that, based on previous studies, differed in their response to the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) (L. M. Vincentini and M. L. Villereal, Proc. Natl. Acad. Sci. USA 82: 8053-8056, 1985). The role of protein kinase C in the activation of Na+-H+ exchange was investigated by comparing the effects of TPA on Na+ influx, in vitro phosphorylation, and in vivo phosphorylation in both cell types. Although both cell types have significant quantities of protein kinase C activity that can be activated by TPA in intact cells, the addition of TPA to intact cells stimulates Na+ influx in WI-38 cells but not in HSWP cells, indicating that in HSWP cells the stimulation of protein kinase C is not sufficient to activate the Na+-H+ exchanger. Cells were then depleted of protein kinase C activity by chronic treatment with high doses of TPA. Both HSWP and WI-38 cells were rendered protein kinase C deficient by this treatment as determined by in vitro and in vivo phosphorylation studies. Protein kinase C-deficient HSWP cells lose the ability for TPA to inhibit the serum-induced activation of Na+-H+ exchange, but there is no reduction in the stimulation of Na+ influx by serum, bradykinin, vasopressin, melittin, or vanadate, indicating that protein kinase C activity is not necessary for the mitogen-induced activation of Na+-H+ exchange in HSWP cells by agents known to stimulate phosphatidylinositol turnover (G. A. Jamieson and M. Villereal. Arch. Biochem. Biophys. 252: 478-486, 1987). In contrast, depletion of protein kinase C activity in WI-38 cells significantly reduces both the TPA- and the serum-induced activation of the Na+-H+ exchange system, suggesting that protein kinase C activity is necessary for at least a portion of the mitogen-induced activation of the Na+-H+ exchanger in WI-38 cells. These results indicate that the mechanisms for regulating Na+-H+ exchange can differ dramatically between different types of fibroblasts.
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Palfrey HC, Nairn AC, Muldoon LL, Villereal ML. Rapid activation of calmodulin-dependent protein kinase III in mitogen-stimulated human fibroblasts. Correlation with intracellular Ca2+ transients. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)48002-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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28
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Muldoon LL, Jamieson GA, Villereal ML. Calcium mobilization in permeabilized fibroblasts: effects of inositol trisphosphate, orthovanadate, mitogens, phorbol ester, and guanosine triphosphate. J Cell Physiol 1987; 130:29-36. [PMID: 3492499 DOI: 10.1002/jcp.1041300106] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Utilizing a digitonin-permeabilized cell system, we have studied the release of calcium from a non-mitochondrial intracellular compartment in cultured human fibroblasts (HSWP cells). Addition of 1 mM MgATP to a monolayer of permeabilized cells in a cytosolic media buffered to 150 nM Ca with EGTA rapidly stimulates 45Ca uptake, and the subsequent addition of the putative intracellular messenger inositol trisphosphate (InsP3) induces rapid release of 85% (+/- 6% n = 6) of the 45Ca taken up in response to ATP. Mitogenic peptides (bradykinin, vasopressin, epidermal growth factor [EGF], and insulin) and orthovanadate, which are effective in mobilizing intracellular Ca in intact cells, have little or no effect when added alone to permeabilized cells. However, in the presence of GTP these agents stimulate accumulation of inositol phosphates and release Ca from the InsP3-sensitive pool. These data suggest that a GTP binding protein is involved in receptor mediated activation of phospholipase C, which leads to release of inositol phosphates. The GTP-dependent release of InsP3 and the mobilization of 45Ca from the intracellular compartment are inhibited by pretreatment of cells, prior to permeabilization, with the protein kinase C activator 12-O-tetradecanoyl-phorbol-13-acetate (TPA). TPA pretreatment does not affect the InsP3 stimulated Ca release. These results suggest that protein kinase C is involved in down-regulation or inhibition of phospholipase C, or the GTP binding protein responsible for relaying the mitogenic signal from the cell surface receptor to the phospholipase C activity.
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