scholarly journals Intracellular cross-talk between thyrotropin receptor and A1 adenosine receptor in regulation of phospholipase C and adenylate cyclase in COS-7 cells transfected with their receptor genes

1995 ◽  
Vol 306 (3) ◽  
pp. 709-715 ◽  
Author(s):  
F Okajima ◽  
H Tomura ◽  
K Sho ◽  
M Akbar ◽  
M A Majid ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Adenylate Cyclase ◽  
Phospholipase C ◽  
Inositol Phosphate ◽  
Term Treatment ◽  
Camp Accumulation ◽  
Thyrotropin Receptor ◽  
A1 Adenosine Receptor ◽  
Kinase C ◽  
Inositol Phosphate Production

COS-7 cells were transiently transfected with human thyrotropin receptor (TSHR) and dog A1 adenosine receptor (A1R) cDNA. TSH stimulated both inositol phosphate production and cyclic AMP (cAMP) accumulation in the cells. An A1 agonist, N6-(L-2-phenylisopropyl)adenosine (PIA), which is ineffective alone, significantly enhanced TSH-induced inositol phosphate production, but insignificantly inhibited TSH-induced cAMP accumulation was revealed by short-term treatment with the protein kinase C inhibitors, staurosporine and K252a, or long-term treatment with 12-myristate 13-acetate, suggesting that endogenous protein kinase C inhibits the A1R-mediated inhibition of the TSHR-adenylate cyclase system. In staurosporine-treated cells, the stimulatory and inhibitory permissive actions of PIA on TSH-induced phospholipase C and adenylate cyclase activation respectively were completely reversed by pretreatment with pertussis toxin whereas intrinsic TSH-induced effects were hardly affected by the toxin. The cross-talk between the signalling pathway for TSHR and that for A1R was not detected in a mixture of cells expressing either TSHR or A1R. We conclude that a single species of A1R, via pertussis-toxin-sensitive GTP-binding proteins, not only inhibits adenylate cyclase but also stimulates phospholipase C in collaboration with an activated TSHR within a single cell expressing both types of receptor.

scholarly journals Scrape-loaded p21ras down-regulates agonist-stimulated inositol phosphate production by a mechanism involving protein kinase C

1989 ◽  
Vol 260 (1) ◽  
pp. 157-161 ◽  
Author(s):  
B D Price ◽  
J D H Morris ◽  
C J Marshall ◽  
A Hall
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Inositol Phosphate ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Ras Protein ◽  
Kinase C ◽  
Inositol Phosphate Production ◽  
Ligand Stimulation ◽  
Scrape Loading

The effect of scrape-loaded [Val-12]p21ras on agonist-stimulated phosphatidylinositol 4,5-bisphosphate (PIP2) turnover in Swiss-3T3 cells was studied. Previously [Morris, Price, Lloyd, Marshall & Hall (1989) Oncogene 4, 27-31] we demonstrated that [Val-12]p21ras activates protein kinase C within 10 min of scrape loading. Here, we show that [Val-12]p21ras inhibits bombesin and platelet-derived growth factor-stimulated PIP2 breakdown 1.5-4 h after scrape loading. This effect persisted for at least 18 h and could be mimicked in control cells by activation of protein kinase C with 12-O-tetradecanoyl 13-acetate (TPA) 15 min prior to ligand stimulation. When protein kinase C was down-regulated by chronic TPA treatment, [Val-12]p21ras was no longer able to inhibit agonist-stimulated inositol phosphate production. These results indicate that changes in inositol phosphate levels caused by ras protein are probably due to activation of protein kinase C and not to an interaction of ras with phospholipase C.

Acute effects of phorbol esters on receptor-mediated IP3, cAMP, and progesterone levels in rat granulosa cells

1989 ◽  
Vol 256 (3) ◽  
pp. E368-E374
Author(s):  
J. S. Davis ◽  
L. L. Weakland ◽  
R. G. Coffey ◽  
L. A. West
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Granulosa Cells ◽  
Phorbol Esters ◽  
Inositol Phosphate ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
Kinase C ◽  
Inositol Phospholipid

Luteinizing hormone (LH) stimulates the formation of adenosine 3',5'-cyclic monophosphate (cAMP) and inositol trisphosphate (IP3) in rat granulosa cells. This report describes the effects of protein kinase C activators on second messenger generation in isolated rat granulosa cells. The protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA) completely inhibited LH-stimulated inositol phosphate accumulation. The inhibitory effects of TPA were rapid (5-15 min) and concentration dependent with 50 nM TPA producing maximally inhibitory effects. However 30-min incubations with 10-100 nM TPA had no effect on LH-stimulated cAMP or progesterone levels. The inhibitory effect of TPA could not be overcome by high concentrations of LH. TPA also inhibited gonadotropin-releasing hormone-stimulated phospholipase C activity, although to a much lesser extent. Increased inositol phosphate degradation and reduced inositol phospholipid synthesis were unlikely explanations for the effects of TPA. The results indicate that phorbol esters modulate the inositol phospholipid-phospholipase C transmembrane signaling system in rat granulosa cells. The results suggest that phorbol esters may alter the coupling of the hormone receptor complex to phospholipase C.

scholarly journals Differential down-regulation of protein kinase C selectively affects IgE-dependent exocytosis and inositol trisphosphate formation

1990 ◽  
Vol 270 (3) ◽  
pp. 679-684 ◽  
Author(s):  
G Gat-Yablonski ◽  
R Sagi-Eisenberg
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Term Treatment ◽  
Short Term Treatment ◽  
Kinase C ◽  
Serotonin Secretion ◽  
Long Term Treatment ◽  
Ic50 Values

Short-term treatment of rat basophilic leukaemia (RBL-2H3) cells with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) activates protein kinase C (PKC) and results in the inhibition of the IgE-dependent formation of inositol phosphates, but in the potentiation of serotonin secretion. Long-term treatment with TPA, which depletes the cells of their endogenous PKC, eliminates both Ca2(+)-ionophore- and TPA- as well as IgE-dependent secretion, but it potentiates by 1.7-fold IgE-induced inositol phosphate formation. Taken together, these observations strongly suggest that the dual actions of TPA on IgE-dependent responses are both mediated by PKC. The opposing effects of TPA are differentially down-regulated. Following TPA treatment, the rate by which the cells lose their ability to undergo exocytosis is faster than the rate at which inhibition of inositol phosphates formation is relieved and their production potentiated. In addition, both processes show different sensitivities to inhibitors of PKC action. Whereas IgE-dependent secretion is completely blocked by the PKC inhibitors K252a, H-7 and sphingosine [concns. causing 50% inhibition (IC50 values) = 25 ng/ml 80 microns and 30 microns respectively], these inhibitors do not relieve inhibition of inositol phosphate formation by TPA, nor do they potentiate this response. These results may imply that the bidirectional control exerted by PKC on IgE-dependent responses is mediated by its different isoenzymes.

Regulation of endothelin-induced Ca2+ mobilization in smooth muscle cells by protein kinase C

1994 ◽  
Vol 266 (6) ◽  
pp. C1560-C1567 ◽  
Author(s):  
Y. T. Xuan ◽  
O. L. Wang ◽  
A. R. Whorton
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Inositol Phosphate ◽  
Phosphatidyl Inositol ◽  
Current Data ◽  
Coupling Mechanism ◽  
Kinase C ◽  
Transient Activation

We have investigated the role of protein kinase C (PKC) in regulating vascular smooth muscle cell responses to endothelin (ET). During the initial phase of the response, ET stimulated rapid formation of diacylglycerol due to rapid and transient activation of phosphatidyl inositol-specific phospholipase C and to rapid and prolonged activation of phospholipase D. Concurrently, ET stimulated translocation of PKC activity that reached a peak at 1 min and remained elevated for at least 20 min. Activation of PKC produced early inhibitory effects. Treatment of cells with phorbol 12-myristate 13-acetate (PMA) 5 min before stimulation with ET inhibited total inositol phosphate formation by > 50%. Because each inositol phosphate isomer was equally affected, the target appears to be either phospholipase C or some upstream component of the receptor coupling mechanism. Activation of PKC was important for sustained response to ET. Treatment of cells with staurosporine significantly reduced sustained elevation of cytosolic free Ca2+ concentration ([Ca2+]i) normally seen with ET. We had previously shown that sustained elevation of [Ca2+]i initiated by ET was due to continued activity of L-type Ca2+ channels. Our current data suggest that PKC is important in this response. For example, staurosporine inhibited both ET-induced 45Ca2+ and Mn2+ entry occurring 10 min after stimulation of influx mechanisms by the agonist. Similarly, pretreatment of cells for 18 h with phorbol dibutyrate depleted the cells of PKC and blocked the sustained activity of Ca2+ entry mechanisms stimulated by ET. Finally, PMA initiated a slowly developing, sustained elevation of [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)

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