Oestradiol-17β modulates the actions of pharmacologically distinct forms of protein kinase C in rat anterior pituitary cells

1993 ◽  
Vol 136 (1) ◽  
pp. 105-117 ◽  
Author(s):  
F. J. Thomson ◽  
M. S. Johnson ◽  
D. J. MacEwan ◽  
R. Mitchell
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Anterior Pituitary ◽  
Ovariectomized Rats ◽  
Pituitary Tissue ◽  
Kinase C ◽  
Lh Release ◽  
Facilitatory Action

ABSTRACT Phorbol ester-induced release of LH and GH from rat anterior pituitary tissue in vitro is differentially inhibited by some, but not other, inhibitors of protein kinase C (PKC), suggesting that pharmacologically distinct species of PKC may have different functional roles in these cells. Since stimulus-induced anterior pituitary hormone release can be enhanced by oestradiol-17β (OE2) pretreatment, we investigated the effect of OE2 treatment of long-term (4 weeks) ovariectomized rats on the amount, activity and cellular actions of pharmacologically distinct PKC species in rat anterior pituitary tissue. Here we report that OE2 treatment enhanced phorbol 12,13-dibutyrate (PDBu)-induced LH but not GH release measured in vitro. This effect of OE2 on LH release may involve synthesis of additional PKCs that are not targeted by the synthetic diacylglycerol, 1,2-dioctanoyl-snglycerol (DOG). Measurements of anterior pituitary PKC activity and [3H] phorbol ester-binding studies suggested that the facilitatory action of OE2 on LH release may occur, at least in part, by altering the quantity and activity of PKC(s). Our results also demonstrate that the OE2-induced PKC(s) which facilitate LH release may be of the type that are not dependent upon raised intracellular Ca2+ for their activation and display distinct pharmacological properties (being readily activated by PDBu, but not by DOG, and are staurosporine-sensitive but H7-insensitive). This facilitatory action of OE2 on PKC-induced LH release does not appear to involve OE2-induced changes in the affinity of existing PKC(s) for PDBu, or changes in the amount of releasable LH in the pituitary prior to the stimulus. Journal of Endocrinology (1993) 136, 105–117

Phorbol ester inhibition of Na-H exchange in rabbit proximal colon

1985 ◽  
Vol 249 (5) ◽  
pp. C527-C530 ◽  
Author(s):  
J. Ahn ◽  
E. B. Chang ◽  
M. Field
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Ph ◽  
Phorbol Ester ◽  
Proximal Colon ◽  
Bathing Medium ◽  
Two Agents ◽  
Luminal Membrane ◽  
Kinase C

In rabbit proximal colon, in vitro addition of phorbol 12,13-dibutyrate (PDB, 10(-7) M) to the serosal bathing medium inhibits mucosal (m)-to-serosal (s) unidirectional Na flux (JsmNa) without altering JsmNa or unidirectional Cl fluxes. Similar results were obtained when amiloride (2 X 10(-4) M) was added to the mucosal bathing medium. No additivity of effect was seen when tissues were exposed to both agents. Measurements with carboxyfluorescein reveal that the two agents cause equal decreases of intracellular pH (pHi), an effect that is dependent on the presence of extracellular Na (Na replacement also decreases pHi). No additivity of pHi effects is seen when both agents are added together. To determine the membrane site of this PDB-inhibitable Na-H exchange, Na influx across the luminal border of proximal colon was measured and was found to be inhibited equally by PDB and amiloride. We conclude that PDB, by activation of protein kinase C, inhibits electro-neutral amiloride-sensitive Na-H exchange in the luminal membrane of proximal colon.

scholarly journals Characterization of the Rac-GAP (Rac-GTPase-activating protein) activity of β2-chimaerin, a ‘non-protein kinase C’ phorbol ester receptor

2003 ◽  
Vol 375 (2) ◽  
pp. 313-321 ◽  
Author(s):  
Maria Jose CALOCA ◽  
HongBin WANG ◽  
Marcelo G. KAZANIETZ
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Gtpase Activating Protein ◽  
Protein Activity ◽  
Rac Gtpase ◽  
Kinase C ◽  
Phorbol Ester Receptor

The regulation and function of β2-chimaerin, a novel receptor for the phorbol ester tumour promoters and the second messenger DAG (diacylglycerol), is largely unknown. As with PKC (protein kinase C) isoenzymes, phorbol esters bind to β2-chimaerin with high affinity and promote its subcellular distribution. β2-Chimaerin has GAP (GTPase-activating protein) activity for the small GTP-binding protein Rac1, but for not Cdc42 or RhoA. We show that acidic phospholipids enhanced its catalytic activity markedly in vitro, but the phorbol ester PMA had no effect. β2-Chimaerin and other chimaerin isoforms decreased cellular levels of Rac-GTP markedly in COS-1 cells and impaired GTP loading on to Rac upon EGF (epidermal growth factor) receptor stimulation. Deletional and mutagenesis analysis determined that the β2-chimaerin GAP domain is essential for this effect. Interestingly, PMA has a dual effect on Rac-GTP levels in COS-1 cells. PMA increased Rac-GTP levels in the absence of a PKC inhibitor, whereas under conditions in which PKC activity is inhibited, PMA markedly decreased Rac-GTP levels and potentiated the effect of β2-chimaerin. Chimaerin isoforms co-localize at the plasma membrane with active Rac, and these results were substantiated by co-immunoprecipitation assays. In summary, the novel phorbol ester receptor β2-chimaerin regulates the activity of the Rac GTPase through its GAP domain, leading to Rac inactivation. These results strongly emphasize the high complexity of DAG signalling due to the activation of PKC-independent pathways, and cast doubts regarding the selectivity of phorbol esters and DAG analogues as selective PKC activators.

FLUORESCENT PHORBOL ESTER BINDING TO THE RECEPTOR PROTEIN KINASE C IN-VITRO AND IN-VIVO

1986 ◽  
Vol 38 (S12) ◽  
pp. 30P-30P ◽  
Author(s):  
N. A. Morrice ◽  
C. Ellis ◽  
A. T. Evans ◽  
F. J. Evans ◽  
A. Drummond ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Receptor Protein ◽  
Kinase C

Bryostatin 1, an activator of protein kinase C, mimics as well as inhibits biological effects of the phorbol ester TPA in vivo and in vitro

1988 ◽  
Vol 9 (4) ◽  
pp. 555-562 ◽  
Author(s):  
M. Gschwendt ◽  
G. Fürstenberger ◽  
S. Rose-John ◽  
M. Rogers ◽  
W. Kittstein ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Biological Effects ◽  
Bryostatin 1 ◽  
Kinase C

scholarly journals Direct interaction between protein kinase C theta (PKC theta) and 14-3-3 tau in T cells: 14-3-3 overexpression results in inhibition of PKC theta translocation and function.

1996 ◽  
Vol 16 (10) ◽  
pp. 5782-5791 ◽  
Author(s):  
N Meller ◽  
Y C Liu ◽  
T L Collins ◽  
N Bonnefoy-Bérard ◽  
G Baier ◽  
...  
Keyword(s):  
T Cells ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
T Cell Activation ◽  
Phorbol Ester ◽  
Interleukin 2 ◽  
General Mechanism ◽  
Wild Type ◽  
Kinase C

Recent studies have documented direct interactions between 14-3-3 proteins and several oncogene and proto-oncogene products involved in signal transduction pathways. Studies on the effects of 14-3-3 proteins on protein kinase C (PKC) activity in vitro have reported conflicting results, and previous attempts to demonstrate a direct association between PKC and 14-3-3 were unsuccessful. Here, we examined potential physical and functional interactions between PKC theta, a Ca(2+)-independent PKC enzyme which is expressed selectively in T lymphocytes, and the 14-3-3 tau isoform in vitro and in intact T cells. PKC theta and 14-3-3 tau coimmunoprecipitated from Jurkat T cells, and recombinant 14-3-3 tau interacted directly with purified PKC theta in vitro. Transient overexpression of 14-3-3 tau suppressed stimulation of the interleukin 2 (IL-2) promoter mediated by cotransfected wild-type or constitutively active PKC theta, as well as by endogenous PKC in ionomycin- and/or phorbol ester-stimulated cells. This did not represent a general inhibition of activation events, since PKC-independent (but Ca(2+)-dependent) activation of an IL-4 promoter element was not inhibited by 14-3-3 tau under similar conditions. Overexpression of wild-type 14-3-3 tau also inhibited phorbol ester-induced PKC theta translocation from the cytosol to the membrane in Jurkat cells, while a membrane-targeted form of 14-3-3 tau caused increased localization of PKC theta in the particulate fraction in unstimulated cells. Membrane-targeted 14-3-3 tau was more effective than wild-type 14-3-3 tau in suppressing PKC theta-dependent IL-2 promoter activity, suggesting that 14-3-3 tau inhibits the function of PKC theta not only by preventing its translocation to the membrane but also by associating with it. The interaction between 14-3-3 and PKC theta may represent an important general mechanism for regulating PKC-dependent signals and, more specifically, PKC theta-mediated functions during T-cell activation.

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