Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used primary cultures of swine granulosa cells to investigate the regulatory role of the protein kinase C pathway in the ovary. In this system, we observed the following. Swine granulosa cells bound [3H]phorbol 12,13-dibutyrate [( 3H]PDB) specifically with high affinity [apparent Ki for 12-O-tetradecanoylphorbol 13-acetate (TPA) = 3.1 (2.1-4.7) nM] and low capacity [0.68 (0.34-0.99) pmol/10(7) cells]. The cytosol of granulosa cells contained functionally active protein kinase C capable of phosphorylating distinct proteins in response to stimulation with active phorbol ester. TPA and PDB induced dose-dependent inhibition (greater than 85%) of follicle-stimulating-hormone (FSH)-stimulated progesterone production. Half-maximally inhibitory concentrations were 0.10 and 0.75 nM for TPA and PDB respectively, whereas phorbol analogues that do not activate protein kinase C were not inhibitory. TPA did not impede cyclic AMP generation in response to FSH, cholera toxin or forskolin acutely (within 48 h), but did inhibit the stimulatory effects of 8-bromo cyclic AMP, insulin and oestradiol on progesterone biosynthesis. In the presence of maximally effective concentrations of 25-hydroxy-, 20 alpha-hydroxy- or 22R-hydroxy-cholesterol as exogenous sterol substrates for cholesterol side-chain cleavage, treatment with TPA suppressed pregnenolone, progesterone and 20 alpha-hydroxypregn-4-en-3-one biosynthesis by more than 80%. The inhibitory effects of phorbol esters were not attributable to non-specific cytotoxicity, since prostaglandin F2 alpha production increased in the same cultures and aromatization of exogenously supplied testosterone to oestradiol was not suppressed. In intact granulosa cells, the effects of phorbol esters were mimicked by a synthetic non-diterpene diacylglycerol, 1-octanoyl-2-acetylglycerol, and the tumour promoter, mezerein, which specifically activates protein kinase C. We conclude that swine granulosa cells contain specific high-affinity receptors for phorbol esters that are functionally coupled to protein phosphorylation. Moreover, treatment with phorbol esters or non-phorbol activators of protein kinase C results in selective inhibition of cholesterol side-chain cleavage activity without impairing cyclic AMP generation or oestrogen biosynthesis.
 ...
PMID:An inhibitory role for the protein kinase C pathway in ovarian steroidogenesis. Studies with cultured swine granulosa cells. 310 2

Intact (IgG) rabbit anti-Ig antibodies, unlike F(ab')2 fragments, do not induce DNA synthesis in murine B cells. The F(ab')2 antibodies induce prolonged breakdown of phosphatidylinositol bisphosphate, and hence activation of protein kinase C (PKC) in B cells, whilst the non-mitogenic antibodies stimulate an abortive response. In order to investigate the role of PKC in B-cell activation, the cells were cultured with combinations of F(ab')2 or intact anti-Ig together with the PKC-activating phorbol esters PDB or PMA. Both these agents synergized with intact anti-Ig to drive resting B cells into the G1 phase of the cell cycle. This is in line with the concept that intact anti-Ig does not induce substantial cell cycle progression in B cells because it fails to cause sufficient activation of PKC. The Ca2+ signal generated by this ligand is apparently sufficient to synergize with PKC activation by phorbol esters to induce B cells to progress into G1. However, the combination of phorbol esters with either form of anti-Ig failed to stimulate B cells to synthesize DNA. This probably reflects the capacity of these agents to inhibit DNA synthesis stimulated by F(ab')2 anti-Ig.
 ...
PMID:Activation and proliferation signals in mouse B cells. IX. Protein kinase C activators synergize with non-mitogenic anti-immunoglobulin antibodies to drive B cells into G1. 326 Feb 15

Binding of [3H]PDB has been measured in the present study to determine the levels of protein kinase C in the neuronal and astrocytic glial cells in culture from rat brain. Binding of [3H]PDB to homogenates of cultured neuronal cells from the brains of normotensive and hypertensive rats was time-dependent and specific. The relative potency for competition by various phorbol esters to [3H]PDB binding was TPA greater than beta-PDD greater than POE greater than alpha-PDD greater than or equal to 4 alpha phorbol. Scatchard analysis showed that neuronal cultures from normotensive rat brains contained 2-3 fold more phorbol ester receptors compared with the glial cultures from the same brains. No differences in the Kd and Bmax were observed between neuronal cultures from normotensive and spontaneously hypertensive rat brains. These studies suggest that the phorbol ester receptors are primarily localized in neuronal cells.
 ...
PMID:Receptors for phorbol esters are primarily localized in neurons: comparison of neuronal and glial cultures. 336 29

1. The involvement of protein kinase C in the presynaptic modulation of stimulated acetylcholine release was investigated in rabbit hippocampus. 2. Slices of the rabbit hippocampus, labelled with [3H]-acetylcholine, were superfused with medium and stimulated electrically during superfusion. 3. The protein kinase C activating phorbol ester 4 beta-phorbol 12,13-dibutyrate (4 beta-PDB) enhanced the electrically evoked tritium overflow in a concentration-dependent manner. Its biologically inactive 4 alpha-isomer was without any effect on transmitter release. 4. The protein kinase C inhibitor polymyxin B decreased the stimulation-evoked tritium overflow and counteracted the enhancement of release caused by 4 beta-PDB. 5. The stimulation-evoked tritium overflow was facilitated when the muscarine receptor antagonist atropine was present. The effects of both atropine and 4 beta-PDB, given in combination, were additive. 6. The net inhibition of the evoked tritium overflow caused by the muscarine receptor agonists carbachol and oxotremorine was similar, irrespective of whether 4 beta-PDB was present or not. 7. Similar results to those for muscarine autoreceptor-mediated inhibition, were obtained for inhibition of the stimulated tritium overflow caused by the adenosine receptor agonist (-)-N6-(R-phenylisopropyl)-adenosine ((-)-PIA) and the opioid receptor agonist ethylketocyclazocine (EKC). The net inhibition of both agonists was independent of the presence of the phorbol ester. 8. The above results provide further evidence for participation of a presynaptically located protein kinase C in the modulation of acetylcholine release. However, the modulatory mechanisms which are coupled to presynaptic receptors and mediate inhibition of release seem not to be directly affected by protein kinase C.
 ...
PMID:Protein kinase C and presynaptic modulation of acetylcholine release in rabbit hippocampus. 337 Mar 87

Effects of phorbol esters on spontaneously beating rabbit sino-atrial (SA) node cells were investigated by means of voltage clamp technique. In a small SA node specimen, 12-O-tetradecanoylphorbol-13-acetate (TPA) 10(-7) mol/l lengthened the cycle length (CL) and at over 3 X 10(-7) mol/l prolonged the action potential duration (APD). Action potential amplitude (APA), maximum diastolic potential (MDP) and maximum rate of rise (Vmax) were unaffected. Amiloride 10(-3) mol/l, an inhibitor of Na+-H+ exchange, did not reverse the phorbol ester-induced effects. In voltage-clamp experiments, TPA 1-10 X 10(-7) mol/l slightly increased the slow inward current (Isi) and the time-dependent inward current (Ih) which activates during hyperpolarization. The outward current and the tail current were reduced, although the activation curve was not shifted along the voltage axis. In the presence of 10(-7) mol/l isoprenaline, TPA produced dysrhythmia and a transient inward current in voltage-clamp experiments. In the presence of 5 X 10(-5) mol/l phenylephrine or 2 X 10(-6) mol/l acetylcholine, TPA also elicited dysrhythmia. 4-beta-phorbol-12,13-dibutyrate (PBD) induced similar electrophysiological effects as TPA, but 4-alpha-phorbol-12,13-didecanoate (PDD) never did so even in the presence of isoprenaline. These results suggest that TPA and PDB might mobilize intracellular Ca2+ via protein kinase C activation in the presence of isoprenaline, phenylephrine or acetylcholine, resulting in dysrhythmia due to delayed afterdepolarization.
 ...
PMID:On electrophysiological responses to phorbol esters which stimulate protein kinase C in rabbit sino-atrial node cells. 339 33

We have evaluated the catalytic and receptor-binding properties of protein kinase C in swine luteal cytosol using two complementary approaches: assay of catalytic activity assessed as the enzymatic transfer of radiolabeled phosphate to histone III-s acceptor protein in the presence of specific phospholipid, diacylglycerol, or phorbol ester and ionic calcium; and, the high-affinity binding of [3H]phorbol-12,13-dibutyrate ([3H]PDB) to the protein kinase C receptor. Catalytic properties of pig luteal protein kinase C included: absolute dependence on calcium ions for maximal activation (approximate ka = 0.5 microM); synergistic activation by 1,2-sn-diolein, phospholipid and calcium ions; and rank order of specific phospholipid activational potency: phosphatidylserine greater than phosphatidic acid greater than phosphatidylinositol greater than phosphatidylethanolamine greater than phosphatidylcholine. The enzyme was also activated by specific phorbol esters at the following half-maximally effective (ED50) concentrations: 12-O-tetradecanoylphorbol-13-acetate (TPA) 11 nM; phorbol-12,13-dibenzoate (PDBe) 26 nM; phorbol-12,13-dibutyrate (PDBu) 33 nM; mezerein 65 nM; and phorbol-12,13-diacetate (PDA) 130 nM. Phorbol-ester receptor properties of protein kinase C included specific, high-affinity (kd congruent to 19 nM), saturable, low-capacity (congruent to 44 pmol/mg protein) [3H]PDB binding sites. Moreover, the rank order of the equilibrium binding ID50s for various phorbol compounds was similar to that of catalytic ED50s: viz. 3 nM TPA; 8 nM PDBe; 16 nM PDBu; 19 nM mezerein; and 590 nM PDA. Thus, swine luteal cytosol contains catalytically active protein kinase C with specific phospholipid sensitivity, synergistic activation by diacylglycerol, phospholipid and calcium, and a strict dependence on ionic calcium concentrations that is influenced markedly by the presence of diacylglycerol.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Catalytic and receptor-binding properties of the calcium-sensitive phospholipid-dependent protein kinase (protein kinase C) in swine luteal cytosol. 347 79

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.
 ...
PMID:Phorbol ester inhibition of Na-H exchange in rabbit proximal colon. 386 81

The calcium- and phospholipid-dependent kinase activity (protein kinase C) was isolated from bovine brains by a combination of DEAE-cellulose chromatography, gel filtration and hydrophobic chromatography on octyl-Sepharose and phenyl-Sepharose. The phorbol ester receptor co-purifies with the protein kinase C throughout the procedure yielding a homogeneous protein of 79 500 daltons on SDS-polyacrylamide gels. The purified kinase incorporated approximately 5000 nmol phosphate into substrate/min/mg protein at saturating concentrations of Ca2+ and phosphatidyl serine. Reciprocal plots of protein kinase activity at varying phosphatidyl serine concentrations were biphasic and yielded two apparent Ka values for phosphatidyl serine of 0.6-2 and 35-80 micrograms/ml). These apparent Ka values were reduced 2- to 3-fold by either diolein (20 micrograms/ml) or phorbol-12,13-dibutyrate (10 micrograms/ml). The protein binds [3H]phorbol-12,13-dibutyrate ( [3H]PDB) with high affinity (Ka = 15 nM) in a phosphatidyl serine-dependent manner. At saturating phosphatidyl serine concentrations 0.89 mol [3H]PDB are bound per mol protein. The identification of protein kinase C as the phorbol ester receptor is discussed with respect to the function and regulation of this protein.
 ...
PMID:Purification to homogeneity of protein kinase C from bovine brain--identity with the phorbol ester receptor. 632 48

The human colonic carcinoma cell line HT-29cl.19A responds to the protein kinase C activator PDB (4-beta-phorbol 12,13-dibutyrate), as it does to forskolin (an activator of adenylyl cyclase), with a secretory response when the cells are grown on filters and studied at 36 degrees C. Previously, we showed that when cells were grown on Petri dishes and studied at about 25 degrees C with the cell-attached patch-clamp technique, forskolin, but not PDB, could activate 8-pS chloride channels (cystic fibrosis transmembrane conductance regulator, CFTR, channels). The present work was carried out to study this discrepancy. Experiments in Ussing chambers, at different temperatures, showed that the responses to PDB and forskolin differ in their temperature sensitivity. This was also found following conventional microelectrode and Ussing chamber studies with nystatin-permeabilized epithelial layers carried out at 25 degrees C and at 36 degrees C. Pre-incubation with the microtubular disruptive agents nocodazole or colcemid did not affect the response to PDB or forskolin, suggesting that chloride secretion induced by these agonists in these cells is independent of the microtubular structure. Pre-incubation with brefeldin A strongly inhibited the response to PDB, but the response to forskolin was hardly affected. The differing effect of temperature and brefeldin A on the responses to forskolin and PDB may be due to the activation of two distinct mechanisms by protein kinases A and C.
 ...
PMID:Chloride secretion induced by phorbol dibutyrate and forskolin in the human colonic carcinoma cell line HT-29Cl.19A is regulated by different mechanisms. 747 22

Effects of protein kinase C (PKC) activator and inhibitors on adrenal catecholamine release were examined in anesthetized dogs. Output of epinephrine (EPI) and norepinephrine (NE) was determined from adrenal venous blood by high-performance liquid chromatography (HPLC) with electrochemical detection. All drugs were infused intraarterially (i.a.) into the adrenal gland through the phrenic abdominal artery. Infusion of the PKC activator phorbol-12,13-dibutyrate (PDB 0.1 micrograms/min) increased EPI and NE output during basal state and enhanced increases in catecholamine output induced by splanchnic nerve stimulation (SNS 1 and 3 Hz). These effects of PDB were abolished by the PKC inhibitor staurosporine (SSP 0.3 microgram/min), when both drugs were infused simultaneously. Infusion of SSP (0.1, 0.3, and 1 micrograms/min) caused a dose-dependent inhibition of the SNS-induced increases in EPI and NE output. SNS-induced increases in catecholamine output were also inhibited by another PKC inhibitor polymyxin B (PMB 0.1, 0.3, and 1 micrograms/min) and by the phospholipase C (PLC) inhibitor neomycin (NM 0.3, 1, and 3 mg/min). SSP, PMB, and NM did not affect basal output of EPI and NE. These results suggest that activation of PKC promotes release of adrenal catecholamines and provide indirect evidence that activation of PKC and PLC may be involved in SNS-induced release of catecholamines from dog adrenal gland.
 ...
PMID:Effects of protein kinase C activator and inhibitor on adrenal catecholamine release in response to splanchnic nerve stimulation in anesthetized dogs. 752 85


<< Previous 1 2 3 4 5 6 7 8 9 Next >>