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The Journal of Clinical Endocrinology & Metabolism Vol. 86, No. 2 773-777
Copyright © 2001 by The Endocrine Society

Original Studies

Adenosine Triphosphate-Evoked Cytosolic Calcium Oscillations in Human Granulosa-Luteal Cells: Role of Protein Kinase C1

Chen-Jei Tai, Sung Keun Kang2 and Peter C. K. Leung3

Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada V6H 3V5

Address all correspondence and requests for reprints to: Dr. Peter C. K. Leung, Department of Obstetrics and Gynecology, University of British Columbia, Room 2H30-4490 Oak Street, Vancouver, BC, Canada V6H 3V5. E-mail: peleung{at}interchange.ubc.ca


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
ATP has been shown to modulate progesterone production in human granulosa-luteal cells (hGLCs) in vitro. After binding to a G protein-coupled P2 purinergic receptor, ATP stimulates phospholipase C. The resultant production of diacylglycerol and inositol triphosphate activates protein kinase C (PKC) and intracellular calcium [Ca2+]i mobilization, respectively. In the present study, we examined the potential cross-talk between the PKC and Ca2+ pathway in ATP signal transduction. Specifically, the effect of PKC on regulating ATP-evoked [Ca2+]i oscillations were examined in hGLCs. Using microspectrofluorimetry, [Ca2+]i oscillations were detected in Fura-2 loaded hGLCs in primary culture. The amplitudes of the ATP-triggered [Ca2+]i oscillations were reduced in a dose-dependent manner by pretreating the cells with various concentrations (1 nM to 10 µM) of the PKC activator, phorbol-12-myristate-13-acetate (PMA). A 10 µM concentration of PMA completely suppressed 10 µM ATP-induced oscillations. The inhibitory effect occurred even when PMA was given during the plateau phase of ATP evoked [Ca2+]i oscillations, suggesting that extracellular calcium influx was inhibited. The role of PKC was further substantiated by the observation that, in the presence of a PKC inhibitor, bisindolylmaleimide I, ATP-induced [Ca2+]i oscillations were not completely suppressed by PMA. Furthermore, homologous desensitization of ATP-induced calcium oscillations was partially reversed by bisindolylmaleimide I, suggesting that activated PKC may be involved in the mechanism of desensitization. These results demonstrate that PKC negatively regulates the ATP-evoked [Ca2+]i mobilization from both intracellular stores and extracellular influx in hGLCs and further support a modulatory role of ATP and P2 purinoceptor in ovarian steroidogenesis.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
ATP, RELEASED FROM autonomic nerves by exocytosis, activates phospholipase C (PLC) through binding to a G protein-coupled P2 purinoceptors. This activation leads to the production of diacylglycerol and inositol 1,4,5-triphosphate, which in turn activates protein kinase C (PKC) and mobilizes intracellular calcium ([Ca2+]i), respectively (1, 2). Through this signaling pathway, ATP may participate in various types of physiological responses, including secretion, membrane potential, cell proliferation, platelet aggregation, neurotransmission, cardiac function, and muscle contraction (3, 4).

PKC, a serine-threonine kinase that can be activated by tumor-promoting phorbol esters, has been shown to play a key role in intracellular signaling and regulate a wide range of cell functions (5, 6). In many systems, PKC has been shown to regulate calcium channel activity and modulate calcium signaling pathway (6, 7, 8). In the ovary, activated PKC has been reported to alter ATP-triggered intracellular calcium oscillations in chicken granulosa cells (9) and inhibit steroidogenesis in swine granulosa cells (10). Recently, ATP has been shown to evoke calcium oscillations and regulate steroidogenesis in human granulosa cells (11, 12, 13). However, the cross-talk between the ATP-triggered PKC and Ca2+ signaling pathways in the human ovary is not understood. The present study was designed to examine the potential effect of PKC in the regulation of ATP-trigger calcium oscillations in human granulosa-luteal cells (hGLCs). As well, the role of PKC in the homologous desensitization of ATP-triggered calcium oscillations was investigated.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Reagents and materials

ATP and phorbol-12-myristate-13-acetate (PMA) were obtained from Sigma (St. Louis, MO). DMEM, penicillin-streptomycin, and FBS were purchased from Life Technologies, Inc. (Burlington, Ontario, Canada). Fura-2 AM was purchased from Molecular Probes, Inc. (Eugene, OR). bisindolylmaleimide I, a PKC inhibitor, was obtained from Calbiochem (Cedarlane, Ontario, Canada).

hGLCs in culture

hGLCs were collected from patients undergoing In Vitro Fertilization-Embryo Transfer (IVF-ET) program. The use of hGLCs is approved by UBC Clinical Screening Committee for Research and Other Studies Involving Human Subjects. Granulosa cells were separated from red blood cells in follicular aspirates by centrifugation through Ficoll Paque, then washed and suspended in DMEM containing 100 U penicillin G sodium/ml, 100 µg streptomycin/ml and 10% heat-inactivated FBS, as described before (12). hGLCs were seeded onto 25-mm circular glass cover slips (5,000 cells/slip) and incubated for 3 days at 37 C in humidified air with 5% CO2 before microfluorimetric experiments.

Microspectrofluorimetry

Cytosolic calcium concentrations were measured using the dual-excitation single-emission fluorometric technique, as described previously (12). Briefly, the cells were incubated with 5–10 µM fura-2 AM acetoxymethyl ester for 30 min at 37 C in humidified air with 5% CO2. The coverslip was mounted onto the perifusion chamber and equilibrated for 10 min with balanced salt buffer (137 mM NaCl, 5.36 mM KCl, 1.26 mM CaCl2, 0.81 mM MgSO4·7H2O, 0.34 mM Na2HPO4·7H2O, 0.44 mM KH2PO4, 4.17 mM NaHCO3, 10 mM HEPES, 2.02 mM glucose, pH 7.4) in humidified air with 5% CO2. The fura-2 ratio measurements were performed using the Attoflour Digital Fluorescence Microscopy System (Atto Instruments, Rockville, MD). The perifusion chamber was connected to a multiunit six-channel perifusion system with a flow rate of 1–2 mL/min. Fura-2 loaded cells were observed through a 40x fluorescent objective lens and illuminated alternatively with light at 340 nm and 380 nm. Emitted light was filtered using a 510 nm long-pass filter and detected using a low light sensitive camera. Measurements of cytosolic calcium were performed at 1–2 sec intervals. All records were normalized for background fluorescence (determined from cell-free region of cover slip). Changes in the fluorescence ratio recorded at 340 and 380 nm correspond to changes in cytosolic calcium.

Treatments

To examine the effect of ATP on inducing intracellular calcium oscillations, hGLCs were treated with various concentrations of ATP (1, 10, or 100 µM) before cytosolic calcium determinations on day 3. Further, hGLCs were cultured for various days (3, 5, or 7 days) before 10 µM ATP treatment.

To investigate the effect of PKC on regulating ATP-triggered calcium oscillations, hGLCs were treated with various concentrations of PKC activator, phorbol-12-myristate-13-acetate (PMA) (1, 10, 100 nM, 1 or 10 µM) for 5 min, followed by treatment with 10 µM ATP for 3 min.

To further investigate the role of PKC in the regulation of ATP-induced calcium oscillations, hGLCs were pretreated with 1 µM bisindolylmaleimide I, a PKC inhibitor (14), for 2 min before PMA and ATP stimulation as performed in the previous experiments.

It has been demonstrated that the intracellular calcium changes are initiated by the release of calcium from cytosolic stores and followed by extracellular calcium influx. To examine whether PKC affects the calcium influx in ATP-evoked calcium mobilization, cells were treated with PMA during the plateau phase of calcium oscillations.

To examine the role of PKC in homologous desensitization of ATP-evoked calcium oscillations, PMA was administered between two ATP treatments. In addition, hGLCs were treated repeatedly with ATP in the absence or presence of Bisindolylmaleimide I.

Data analysis

Data were shown as means of three individual experiments and presented as the mean ± SD. The data were analyzed by one-way ANOVA followed by Tukey test. Data were considered significant when P < 0.05.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Induction of cytosolic calcium oscillations by ATP in hGLCs

hGLCs were treated with various concentrations of ATP (1, 10, or 100 µM) for 3 min. Our results showed that ATP triggered calcium oscillations in these cells (Fig. 1AGo). The response to ATP was characterized by a spike and a marked increase in cytosolic calcium, followed by numerous oscillations with decreasing amplitudes to preactivated levels. As shown in Fig. 1AGo, ATP induced cytosolic mobilization in a dose-dependent manner, with maximal response reached when treated with 10 µM of ATP, and no difference was noted between cells treated with 10 µM and 100 µM. Figure 1BGo demonstrated the effects of 10 µM ATP on inducing calcium mobilization in hGLCs with various culturing days. There were no significant difference in both of the patterns and amplitudes of ATP-evoked calcium oscillations.



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  		Figure 1. Effects of ATP on inducing cytosolic calcium oscillations in cultured hGLCs. A, Fura-2 loaded hGLCs were treated with various concentrations of ATP (1–100 µM). B, Effects of 10 µM ATP on hGLCs cultured for various days (D3–D7). Data of calcium oscillations were presented as ratio (340:380 nm).

 
The role of PKC in ATP-triggered calcium oscillations in hGLCs

To determine the role of activated PKC in ATP-triggered calcium oscillations, hGLCs were pretreated with increasing concentrations of PKC activator, PMA (1 nM, 10 nM, 100 nM, 1 µM, or 10 µM) for 5 min, and then stimulated with 10 µM ATP. As shown in Fig. 2Go, PMA pretreatment reduced the amplitudes of ATP-induced calcium oscillations in a dose-dependent manner. Complete inhibition of initial [Ca2+]i spike was noted when cells were pretreated with 10 µM PMA.



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  		Figure 2. Dose-dependent effects of PMA on ATP-evoked cytosolic calcium oscillations in cultured hGLCs. Fura-2 loaded hGLCs were pretreated with various concentrations of PMA (1 nM to 10 µM, B–F) for 5 min before treatment with 10 µM ATP. Data of calcium oscillations were presented as ratio (340:380 nm).

 
To further examine the role of PKC in the regulation of ATP-triggered calcium oscillations, Fura-2 loaded hGLCs were pretreated in sequence with 1 µM bisindolylmaleimide I for 2 min, and Bisindolylmaleimide I plus 10 µM PMA for 5 min, before treatment of 10 µM ATP. The results revealed that, in contrast to pretreatment with PMA alone (Fig. 2FGo), ATP induced calcium oscillations when the cells were pretreated with both PMA and the PKC inhibitor (Fig. 3Go).



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  		Figure 3. The role of PKC in ATP induced-calcium oscillations in cultured hGLCs. Fura-2 loaded hGLCs were pretreated in sequence with 1 µM bisindolylmaleimide I for 2 min, and bisindolylmaleimide I plus 10 µM PMA for 5 min, before treatment with 10 µM ATP. Data of calcium oscillations were presented as ratio (340:380 nm).

 
To examine whether PMA affects the calcium influx in ATP-evoked calcium mobilization, cells were treated with PMA during the plateau phase of ATP-triggered calcium oscillations. The result, when compared with control (Fig. 4AGo), demonstrated that the amplitudes of calcium oscillations of PMA-treated cells declined to baseline level abruptly (Fig. 4BGo), suggesting that calcium influx was inhibited by activated PKC.



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  		Figure 4. The effect of PMA on ATP-evoked cytosolic calcium oscillations in cultured hGLCs. A, The biphasic pattern of ATP-induced cytosolic calcium oscillations in cultured hGLCs, which was initiated by the release of calcium from cytosolic store and followed by extracellular calcium influx. B, Fura-2 loaded hGLCs were treated with PMA during the plateau phase of calcium oscillations. Data of calcium oscillations were presented as ratio (340:380 nm).

 
The role of PKC in homologous desensitization of ATP-triggered calcium oscillations in hGLCs

Calcium replacement is required to maintain cytosolic calcium oscillations during repeated ATP treatments (13). In the present study, treatment of hGLCs with PMA completely suppressed the subsequent ATP-induced calcium oscillations (Fig. 5AGo), suggesting that activated PKC may play a role in mediating homologous desensitization. In addition, calcium oscillations were partially reversed during subsequent exposures of hGLCs to ATP in the presence of bisindolylmaleimide I (Fig. 5CGo), when compared with repeated ATP exposures in the absence of bisindolylmaleimide I (Fig, 5B), supporting the proposal that PKC may be involved in homologous desensitization of ATP-triggered calcium oscillations.



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  		Figure 5. The role of PKC in homologous desensitization of ATP induced-calcium oscillations in cultured hGLCs. A, Fura-2 loaded hGLCs were treated with 10 µM PMA for 5 min following exposure to ATP. No cytosolic calcium oscillations were induced by subsequent ATP treatment. B and C, The effect of PKC was observed in the absence or presence of PKC inhibitor, bisindolylmaleimide during repeated treatment of ATP in hGLCs. Data of calcium oscillations were presented as ratio (340:380 nm). Data represent the means ± SE. *, Significantly different from control (P < 0.05).

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
ATP, released from nerve endings, has been shown to participate in various types of physiological responses (3, 4, 15, 16, 17). It is tempting to speculate that the coreleased ATP from autonomic nerve endings in the ovary may play a role in regulating ovarian function. ATP has been shown to regulate the production of progesterone and estradiol in hGLCs (11). We have reported previously that the P2U purinoceptor is expressed in hGLCs (18), further supporting a physiological role of ATP in the human ovary.

Calcium, a second messenger, has been shown to mediate several physiological activities including fertilization, embryo development, cell proliferation, and cell death (19). As demonstrated in this study, ATP is able to mobilize cytosolic calcium, implicating a role of ATP in the control of ovarian function. This finding leads us to postulate that several calcium-dependent kinases such as PKC or Ca2+/calmodulin-dependent protein kinase (20) may be involved in regulating cellular function. However, the precise role of calcium oscillations is not clear yet (8). PKC has been reported to modulate the activities of ion channels including calcium channels and potassium channels (21). In addition, PKC has been shown to modulate cytosolic calcium and cAMP levels induced by activation of P2U-purinergic receptor on rat glioma cells (22). In the ovary, PKC has been reported to modulate ATP-evoked calcium oscillation in chicken granulosa cells, supporting the notion that the calcium oscillations were reduced by either activation or inhibition of PKC activity (9). In the present study, a role of PKC in regulating ATP-induced calcium oscillations was revealed in hGLCs. Our results demonstrate that the activation of PKC activity negatively regulated the ATP-evoked cytosolic calcium mobilization from both intracellular stores and extracellular influx in cultured hGLCs. Pretreatment with a PKC inhibitor reversed the inhibitory effect of activated PKC, further supporting the role of PKC in ATP-evoked calcium oscillations in the human ovary.

ATP has been shown to effect a homologous desensitization of ATP-receptor (23). Homologous desensitization is characterized by a reduced response to an agonist due to repeated treatments with the same agonist. It has been suggested that PKC activated by agonists may be involved in the mechanism of desensitization in several studies (23, 24, 25). ATP-evoked calcium oscillations are dependent upon calcium mobilizations from both cytosolic stores and extracellular influx. Calcium replacement is required to maintain cytosolic calcium oscillations during repeated ATP treatments (13). However, the calcium replacement still cannot prevent the down-regulation of the amplitudes of oscillations during repeated ATP treatments, implying that another regulator exists. Several other studies have linked this type of desensitization with activated PKC (22, 26). In many systems, PKC has been shown to regulate calcium channel activity and modulate calcium signaling pathway (6, 7, 8). In the present study, repeated treatment of ATP decreased the amplitudes of initial spike of calcium oscillations, which can be partially reversed by pretreatment with PKC inhibitor. This result indicates that PKC mediates ATP-induced homologous desensitization in calcium oscillations in hGLCs.

The mechanism of PKC in regulating calcium oscillations is not clear. Several proteins in the ATP signal transduction pathway can be proposed to act as potential targets of activated PKC. Considering several potential phosphorylation sites in P2U purinoceptor (27), the P2U purinoceptor function may be affected by activated PKC (Fig. 6Go, arrow 1). This proposal is supported by the finding that phorbol ester, a PKC activator, can inhibit the function of G protein-coupled receptor (28, 29). With respect to receptor-coupled G proteins, several studies have shown that phorbol ester can regulate G protein-mediated responses (30, 31, 32), indicating that P2UR-coupled G protein may be inhibited by activated PKC in hGLCs (Fig. 6Go, arrow 2]). In addition, activated PKC has been identified to attenuate agonist-induced inositol phospholipid hydrolysis (33, 34, 35), suggesting that agonist-stimulated phospholipase C may be desensitized through a negative feedback involving the activation of PKC (Fig. 6Go, arrow 3). Inositol triphosphate (IP3), a product of inositol phospholipid hydrolysis, binds to IP3 receptors on endoplasmic reticulum and induces the release of calcium from the intracellular stores. PKC has been shown to phosphorylate a serine site on IP3 receptors (36, 37), implying that activated PKC may shutdown cytosolic calcium mobilization through inactivation of the function of IP3 receptor (Fig. 6Go, arrow 4). Calcium influx from the extracellular environment plays a critical role in maintaining the plateau phase following an initial peak of cytosolic calcium oscillations (12). PKC has been demonstrated to down-regulate or alter calcium influx in agonist-induced calcium mobilization in different systems (21, 38, 39, 40) (Fig. 6Go, arrow 5]). Based on above findings, it can be proposed that the ATP-activated PKC may feedback at different levels intracellularly, including the P2U purinoceptor, G protein-coupled, phospholipase C, IP3 receptor, or calcium channel, culminating in a shutdown of the calcium signaling pathway in hGLCs.



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  		Figure 6. A proposed model of the potential cross-talk between ATP-activated PKC and cytosolic calcium oscillations in hGLCs. P2UR, P2U purinoceptor on cell membrane; G, G protein-coupled; PLC, phospholipase C; PIP2, phosphatidyl-inositol 4,5-bisphosphate; DAG, diacylglycerol; IP3, inositol 1,4,5-triphosphate; IP3R, IP3 receptor.

 
In conclusion, our results demonstrated that 1) ATP was capable of inducing calcium oscillation in hGLCs in a dose-dependent manner; 2) PKC negatively regulated the ATP-evoked [Ca2+]i mobilization from both intracellular stores and extracellular influx in cultured hGLCs; and 3) PKC was involved in ATP-induced homologous desensitization in hGLCs. Taken together, these results indicate that ATP may exert a feedback regulation on its own signaling pathway through activation of PKC in the human ovary.


   Acknowledgments
 
We would like to thank Dr. Margo Fluker and the Genesis Fertility Center, Vancouver, Canada, for the provision of hGLCs.


   Footnotes
 
1 This study was supported by the Medical Research Council of Canada. Back

2 A studentship award recipient of the British Columbia Research Institute for Children’s and Women’s Health. Back

3 A career investigator of the British Columbia Research Institute for Children’s and Women’s Health. Back

Received April 21, 2000.

Revised June 26, 2000.

Accepted July 24, 2000.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Berridge MJ. 1984 Inositol trisphosphate and diacylglcerol as second messengers. Biochem J. 220:345–360.[Medline]
  2. Gordon JL. 1986 Extracellular ATP: effects, sources and fate. Biochem J. 233:309–319.[Medline]
  3. el-Moatassim C, Dornand J, Mani JC. 1992 Extracellular ATP and cell signalling. Biochim Biophys Acta. 1134:31–45.[Medline]
  4. Burnstock G. 1990 Overview. Purinergic mechanisms. Ann NY Acad Sci. 603:1–17.
  5. Hug H, Sarre TF. 1993 Protein kinase C isozymes: divergence in signal transduction? Biochem J. 291:329–343.
  6. Nishizuka Y. 1992 Intracellular signaling by hydrolysis of phopholipids and activation of protein kinase C. Science. 258:607–614.[Abstract/Free Full Text]
  7. Berridge MJ. 1991 Cytoplasmic calcium oscillations: a two pool model. Cell Calcium. 12:63–72.[CrossRef][Medline]
  8. Tsien RW, Tsien RY. 1990 Calcium channels, stores, and oscillations. Annu Rev Cell Biol. 6:715–760.[CrossRef]
  9. Morley P, Chakravarthy BR, Mealing GA, Tsang BK, Whitfield JF. 1996 Role of protein kinase C in the regulation of ATP-triggered intracellular Ca2+ oscillations in chicken granulosa cells. Eur J Endocrinol. 134:734–750.
  10. Veldhuis JD, Demers LM. 1986 An inhibitory role for the protein kinase C pathway in ovarian steroidogenesis. Studies with cultured swine granulosa cells. Biochem J. 239:505–511.[Medline]
  11. Kamada S, Blackmore PF, Oehninger S, Gordon K, Hodgen GD. 1994 Existence of P2-purinoceptors on human and porcine granulosa cells. J Clin Endocrinol Metab. 78:650–656.[Abstract]
  12. Lee PS, Squires PE, Buchan AM, Yuen BH, Leung PC. 1996 P2-purinoreceptor evoked changes in intracellular calcium oscillations in single isolated human granulosa-lutein cells. Endocrinology. 137:3756–3761.[Abstract]
  13. Squires PE, Lee PS, Yuen BH, Leung PC, Buchan AM. 1997 Mechanisms involved in ATP-evoked Ca2+ oscillations in isolated human granulosa-luteal cells. Cell Calcium. 21:365–374.[CrossRef][Medline]
  14. Toullec D, Pianetti P, Coste H, et al. 1991 The Bisindolylmaleimide GF 109203X is a potent and selective inhibitor of protein kinase C. J Biol Chem. 266:15771–81.[Abstract/Free Full Text]
  15. Owman C, Rosengren E, Sjoberg NO. 1967 Adrenergic innervation of the human female reproductive organs: a histochemical and chemical investigation. Obstet Gynecol. 30:763–773.[Medline]
  16. Bodis J, Tinneberg HR, Torok A, Cledon P, Hanf V, Papenfuss F. 1993 Effect of noradrenaline and dopamine on progesterone and estradiol secretion of human granulosa cells. Acta Endocrinol (Copenh). 129:165–168.[Medline]
  17. Bodis J, Tinneberg HR, Papenfuss F, et al. 1993 Cholinergic stimulation of progesterone and estradiol secretion by human granulosa cells cultured in serum-free medium. Gynecol Endocrinol. 7:83–87.[Medline]
  18. Tai CJ, Kang SK, Cheng KW, Choi KC, Nathwani PS, Leung PCK. 2000 Expression and regulation of P2U-purinergic receptor in human granulosa-luteal cells. J Clin Endocrinol Metab. 85:1591–1597.[Abstract/Free Full Text]
  19. Berridge MJ, Bootman MD, Lipp P. 1998 Calcium—life and death signal. Nature. 395:645–648.[CrossRef][Medline]
  20. James W, Putney J. 1998 Calcium signaling: up, down, up, down. . . . What’s the point? Science. 279:191–192.[Free Full Text]
  21. Shearman MS, Sekiguchi K, Nishizuka Y. 1989 Modulation of ion channel activity: a key function of the protein kinase C enzyme family. Pharmacol Rev. 41:211–237.[Abstract]
  22. Munshi R, DeBernardi MA, Brooker G. 1993 P2U-purinergic receptors on C6–2B rat glioma cells: modulation of cytosolic Ca2+ and cAMP levels by protein kinase C. Mol Pharmacol. 44:1185–1191.[Abstract]
  23. Dickenson JM, Hill SJ. 1993 Homologous and heterologous desensitization of histamine H1- and ATP-receptors in the smooth muscle cell line, DDT1MF-2: the role of protein kinase C. Br J Pharmacol. 110:1449–1456.[Medline]
  24. Brown KD, Blakeley DM, Hamon MH, Laurie MS, Corps AN. 1987 Protein kinase C-mediated negative-feedback inhibition of unstimulated and bombesin-stimulated polyphosphoinositide hydrolysis in Swiss mouse 3T3 cells. Biochem J. 245:631–639.[Medline]
  25. Jones JA, Owen PJ, Boarder MR. 1990 Influence of phorbol esters, and diacylglycerol kinase and lipase inhibitors on noradrenaline release and phosphoinositide hydrolysis in chromaffin cells. Br J Pharmacol. 101:521–526.[Medline]
  26. Wilkinson GF, Purkiss JR, Boarder MR. 1994 Differential heterologous and homologous desensitization of two receptors for ATP (P2Y purinoceptors and nucleotide receptors) coexisting on endothelial cells. Mol Pharmacol. 45:731–736.[Abstract]
  27. Leeb-Lundberg LM, Cotecchia S, Lomasney JW, DeBernardis JF, Lefkowitz RJ, Caron MG. 1985 Phorbol esters promote alpha1-adrenergic receptor phosphorylation and receptor uncoupling from inositol phospholipid metabolism. Proc Natl Acad Sci USA. 82:5651–5655.[Abstract/Free Full Text]
  28. Thomopoulos P, Testa U, Gourdin MF, Hervy C, Titeux M, Vainchenker W. 1982 Inhibition of insulin receptor binding by phorbol esters. Eur J Biochem. 129:389–393.[Medline]
  29. Lustig KD, Weisman GA, Turner JT, Garrad R, Shiau AK, Erb L. 1996 P2U purinoceptors: cDNA cloning, signal transduction mechanisms and structure- function analysis. Ciba Found Symp. 198:193–207.[Medline]
  30. Orellana S, Solski PA, Brown JH. 1987 Guanosin 5'-O-(thiotriphosphate)-dependent inositol trisphosphate formation in membranes is inhibited by phorbol ester and protein kinase C. J Biol Chem. 262:1638–1643.[Abstract/Free Full Text]
  31. Sagi-Eisenberg R. 1989 GTP-binding proteins as possible targets for protein kinase C action. Trends Biochem Sci. 14:355–357.[CrossRef][Medline]
  32. Krishnamurthi S, Wheeler-Jones CP, Kakkar VV. 1989 Effect of phorbol ester treatment on receptor-mediated versus G-protein-activator-mediated responses in platelets. Evidence for a two-site action of phorbol ester at the level of G-protein function. Biochem J. 262:77–81.[Medline]
  33. Zavoico GB, Halenda SP, Sha’afi RI, Feinstein MB. 1985 Phorbol myristate acetate inhibits thrombin-stimulated Ca2+ mobilization and phosphatidylinositol 4,5-bisphosphate hydrolysis in human platelets. Proc Natl Acad Sci USA. 82:3859–3862.[Abstract/Free Full Text]
  34. Dubyak GR. 1986 Extracellular ATP activates polyphosphoinositide breakdown and Ca2+ mobilization in Ehrlich ascites tumor cells. Arch Biochem Biophys. 245:84–95.[CrossRef][Medline]
  35. Ryu SH, Kim UH, Wahl MI, Brown AB, Carpenter G, Huang KP, Rhee SG. 1990 Feedback regulation of phospholipase C-ß by protein kinase C. J Biol Chem. 265:17941–5.[Abstract/Free Full Text]
  36. Ferris CD, Huganir RL, Bredt DS, Cameron AM, Snyder SH. 1991 Inositol trisphosphate receptor: Phosphorylation by protein kinase C and calcium calmodulin-dependent protein kinases in reconstituted lipid vesicles. Proc Natl Acad Sci USA. 88:2232–2235.[Abstract/Free Full Text]
  37. Ferris CD, Cameron AM, Bredt DS, Huganir RL, Snyder SH. 1992 Autophosphorylation of inositol 1,4,5-trisphosphate receptors. J Biol Chem. 267:7036–7041.[Abstract/Free Full Text]
  38. Di Virgilio F, Pozzan T, Wollheim CB, Vicentini LM, Meldolesi J. 1986 Tumor promoter phorbol myristate acetate inhibits Ca2+ influx through voltage-gated Ca2+ channels in two secretory cell lines, PC12 and RINm5F. J Biol Chem. 261:32–35.[Abstract/Free Full Text]
  39. Rane SG, Dunlap K. 1986 Kinase C activator 1,2-oleoylacetylglycerol attenuates voltage-dependent calcium current in sensory neurons. Proc Natl Acad Sci USA. 83:184–188.[Abstract/Free Full Text]
  40. Clunes MT, Kemp PJ. 1996 P2u purinoceptor modulation of intracellular Ca2+ in a human lung adenocarcinoma cell line: down-regulation of Ca2+ influx by protein kinase C. Cell Calcium. 20:339–346.[CrossRef][Medline]



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