Multiple effects of phorbol ester on secretory activity in rabbit gastric glands and parietal cells

1987 ◽  
Vol 65 (9) ◽  
pp. 1840-1847 ◽  
Author(s):  
Milton R. Brown ◽  
Catherine S. Chew
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Acid Secretion ◽  
Cholera Toxin ◽  
Parietal Cell ◽  
Pertussis Toxin ◽  
Secretory Activity ◽  
Gastric Glands ◽  
Kinase C ◽  
Stimulation Of

Acid secretory activity and respiration in rabbit gastric glands are stimulated by cAMP-dependent and -independent agonists. Potentiation between agonists suggests interaction of the activation pathways. Regulation of secretory response by protein kinase C was investigated with 12-O-tetradecanoyl phorbol-13-acetate (TPA). TPA elevated basal respiration, pepsin release, and acid secretion but inhibited histamine and carbachol stimulation of acid secretion by gastric glands, as measured by [dimethylamino-14C]aminopyrine accumulation. The inhibition of histamine response was specific for protein kinase C activators, occurred after a 20-min lag, and was not reversed by removal of TPA after 3 min of preincubation. TPA pretreatment inhibited acid secretory responses to cholera toxin and forskolin but enhanced the response to cAMP analogues. Cholera toxin and pertussis toxin simulated ADP-ribosylation of 45 and 41 kDa proteins, respectively, in parietal cell membranes. Therefore, both stimulatory (Gs) and inhibitory (Gi) GTP binding proteins of adenylyl cyclase appear to be present in parietal cells. Pretreatment with pertussis toxin attenuated PGE2 but not TPA inhibition of histamine stimulation of aminopyrine accumulation. Thus, the inhibitory effect of TPA does not appear to be associated with an action on Gi. The results with histamine and carbachol suggest that protein kinase C may regulate both cAMP-dependent and -independent stimulation of parietal cell acid secretion.

scholarly journals Stimulation of generation of inositol phosphates by carbamoylcholine and its inhibition by phorbol esters and iodide in dog thyroid cells

1989 ◽  
Vol 263 (3) ◽  
pp. 795-801 ◽  
Author(s):  
E Laurent ◽  
J Mockel ◽  
K Takazawa ◽  
C Erneux ◽  
J E Dumont
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Cholera Toxin ◽  
Pertussis Toxin ◽  
Inositol Phosphates ◽  
Cholinergic Stimulation ◽  
Kinase C ◽  
Gtp Binding ◽  
Stimulation Of

The action of carbamoylcholine (Cchol), NaF and other agonists on the generation of inositol phosphates (IPs) was studied in dog thyroid slices prelabelled with myo-[2-3H]inositol. The stimulation by Cchol (0.1 microM-0.1 mM) of IPs accumulation through activation of a muscarinic receptor [Graff, Mockel, Laurent, Erneux & Dumont (1987) FEBS Lett. 210, 204-210] was pertussis- and cholera-toxin insensitive. Ins(1,4,5)P3, Ins(1,3,4)P3 and InsP4 were generated. NaF (5-20 mM) also increased IPs generation (Graff et al., 1987); this effect was potentiated by AlCl3 (10 microM) and unaffected by pertussis toxin. Although phorbol dibutyrate (5 microM) abolished the cholinergic stimulation of IPs generation (Graff et al., 1987), it did not affect the fluoride-induced response. Cchol and NaF did not require extracellular Ca2+ to exert their effect, and neither KCl-induced membrane depolarization nor ionophore A23187 (10 microM) had any influence on basal IPs levels, or on cholinergic stimulation. However, more stringent Ca2+ depletion with EGTA (0.1 or 1 mM) decreased basal IPs levels as well as the amplitude of the stimulation by Cchol without abolishing it. Dibutyryl cyclic AMP, forskolin, cholera toxin and prostaglandin E1 had no effect on basal IPs levels and did not decrease the response to Cchol. Iodide (4 or 40 microM) also strongly decreased the cholinergic action on IPs, this inhibition being relieved by methimazole (1 mM). Our data suggest that Cchol activates a phospholipase C hydrolysing PtdIns(4,5)P2 in the dog thyroid cell in a cyclic AMP-independent manner. This activation requires no extracellular Ca2+ and depends on a GTP-binding protein insensitive to both cholera toxin and requires no extracellular Ca2+ and depends on a GTP-binding protein insensitive to both cholera toxin and pertussis toxin. The data are consistent with a rapid metabolism of Ins(1,4,5)P3 to Ins(1,3,4)P3 via the Ins(1,4,5)P3 3-kinase pathway, followed by dephosphorylation by a 5-phosphomonoesterase. Indeed, a Ca2+-sensitive InsP3 3-kinase activity was demonstrated in tissue homogenate. Stimulation of protein kinase C and an organified form of iodine inhibit the Cchol-induced IPs generation. The negative feedback of activated protein kinase C could be exerted at the level of the receptor or of the receptor-G-protein interaction.

Rat histidine decarboxylase promoter is regulated by gastrin through a protein kinase C pathway

1996 ◽  
Vol 270 (4) ◽  
pp. G619-G633 ◽  
Author(s):  
M. Hocker ◽  
Z. Zhang ◽  
D. A. Fenstermacher ◽  
S. Tagerud ◽  
M. Chulak ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Time Course ◽  
Histidine Decarboxylase ◽  
Peptide Hormone ◽  
Direct Stimulation ◽  
Gastric Glands ◽  
Kinase C ◽  
Translational Start ◽  
Stimulation Of

The enzyme L-histidine decarboxylase (HDC; EC 4.1.1.22), which converts L-histidine to histamine, plays a key role in the regulation of acid secretion. In the rat and human stomach, the peptide hormone gastrin appears to be one of the main regulators of HDC expression. In rats, marked elevation of gastric HDC mRNA abundance was observed within 12 h after induction of hypergastrinemia by a single injection of the proton-pump blocker omeprazole. In situ hybridization revealed that HDC expression occurred in the basal third of gastric glands where enterochromaffin-like cells are localized. To study the regulation of HDC gene transcription, 1,291 nucleotides of the 5'-flanking region of the rat HDC gene and the noncoding portion of exon 1 were cloned and sequenced. Gastrin and cholecystokinin (CCK) octapeptide equipotently stimulated the transcriptional activity of the rat HDC promoter three- to fourfold, and deletion analysis revealed the presence of a gastrin response element within 201 nucleotides upstream of the translational start site. Time-course studies revealed maximal activation of the HDC promoter after 12-36 h. Direct stimulation of protein kinase C (PKC) with the phorbol ester phorbol 12-myristate 13-acetate (PMA) substantially elevated rat HDC promoter activity, whereas induction of Ca2+ -dependent signaling pathways with thapsigargin was without effect. Downregulation or blockade of PKC abolished the effects of gastrin and PMA on the HDC promoter. These data indicate that stimulation of the CCK-B/gastrin receptor activates the rat HDC promoter in a time- and dose-dependent fashion and that this effect is primarily mediated via a PKC-dependent signaling pathway. Use of HDC as a model gene will allow further investigation of the intracellular pathways that are involved in gastrin-dependent gene regulation.

Ca2+-independent protein kinase C isoforms may modulate parietal cell HCl secretion

1997 ◽  
Vol 272 (2) ◽  
pp. G246-G256 ◽  
Author(s):  
C. S. Chew ◽  
C. J. Zhou ◽  
J. A. Parente
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Parietal Cell ◽  
Morphological Changes ◽  
Dependent Manner ◽  
Independent Manner ◽  
Gastric Glands ◽  
Kinase C ◽  
Pkc Epsilon ◽  
Hcl Secretion

Although activation of adenosine 3',5'-cyclic monophosphate by histamine and of Ca2+-dependent signaling pathways by cholinergic agonists is a generally recognized mechanism for increasing parietal cell HCl secretion, the role of protein kinase C (PKC) in this process is controversial. In this study, acid-secretory responses of gastric glands from rabbits [measured as accumulation of aminopyrine (AP)] were found to be relatively resistant to the PKC inhibitors calphostin C, chelerythrine chloride, staurosporine, and the bisindolylmaleimide-like inhibitors Ro 31-8220, Go 6976, and bisindolylmaleimide I hydrochloride. Western analyses of the PKC isozyme profile in highly enriched parietal cells (98% purity) indicated that this cell type expresses abundant levels of the novel isoforms PKC-epsilon and PKC-mu and abundant levels of the atypical isoforms PKC-iota, PKC-lambda, and PKC-zeta. In contrast, there appeared to be low to undetectable expression of the classical isoforms PKC-alpha and PKC-beta1/beta2, respectively. Relatively high concentrations of Ro 31-8220 potentiated both carbachol- and histamine-stimulated AP accumulation (IC50 857 +/- 100 and 910 +/- 98 nM, respectively). There was a similar dose dependence for Ro 31-8220 inhibition of in situ phosphorylation of a parietal cell phosphoprotein, pp66 (IC50 750 +/- 120 nM). Similar concentrations of Ro 31-8220 also inhibited phosphorylation of the cytoskeletal, actin membrane cross-linking phosphoprotein ezrin, but not other phosphoproteins. Ezrin phosphorylation was increased by carbachol and 12-O-tetradecanoylphorbol 13-acetate (TPA). Because carbachol and TPA stimulate pp66 phosphorylation in a Ca2+-independent manner, our results suggest that one or more novel PKC isoforms may be involved in negative regulation of HCl secretion. In related experiments, PKC-epsilon, but not PKC-mu, was immunolocalized by confocal microscopy to a parietal cell compartment that bore a striking resemblance to that containing filamentous actin. Moreover, pp66 was enriched in a Triton X-100-insoluble parietal cell fraction, suggesting a potential cytoskeletal localization for this unknown protein. Given their location and sensitivity to Ro 31-8220, it is possible that pp66 and ezrin interact in a PKC-dependent manner to regulate the well-known morphological changes that occur in concert with agonist-dependent activation of parietal cell HCl secretion.

scholarly journals cAMP-dependent inhibition is dominant in regulating superoxide production in the bone-resorbing osteoclasts

1998 ◽  
Vol 158 (3) ◽  
pp. 311-318 ◽  
Author(s):  
CE Berger ◽  
BR Horrocks ◽  
HK Datta
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Pertussis Toxin ◽  
Kinase C ◽  
Significant Stimulation ◽  
Dependent Inhibition ◽  
Dependent Protein ◽  
O2 Production ◽  
Stimulation Of

Calciotropic hormones such as parathyroid hormone (PTH) and calcitonin have been shown to have stimulatory and inhibitory effects respectively on superoxide anion (O2-) generation by osteoclasts, but the exact intracellular signalling mediating these pathways has not been investigated. In order to elucidate the intracellular pathways controlling O2- generation, we have carried out a systematic study of the effect of different agents on O2- production in osteoclasts cultured on bovine cortical bone. Dibutyryl cAMP and cholera toxin, while having no effect on the basal level of O2- production in bone-resorbing osteoclasts, were, however, found to completely block the stimulation of free radical production by PTH, pertussis toxin and ionomycin. The stimulation of O2- production was found to be independent of protein kinase C-dependent pathways since the presence of bisindolylmaleimide (GF109203X) (1 microM) did not block stimulation by PTH and pertussis toxin. Interestingly, while exposure to bisindolylmaleimide at this concentration did not have any effect on the basal level of O2- production, exposure to a higher concentration (10 microM), which is known to inhibit both protein kinase C and A, produced significant stimulation. These in vitro findings suggest that in the bone-resorbing cells, cAMP-dependent protein kinases prevent further stimulation of NADPH oxidase by agents such as PTH and pertussis toxin. The increase in cAMP has also been recently demonstrated to be associated with down-regulation of the oxidative burst in adherent neutrophils; and the findings reported here suggest a similar role for cAMP in O2- generation in osteoclasts cultured on bone.

ANP stimulates phospholipase C in cultured RIMCT cells: roles of protein kinases and G protein

1991 ◽  
Vol 260 (4) ◽  
pp. F590-F595 ◽  
Author(s):  
T. Berl ◽  
J. Mansour ◽  
I. Teitelbaum
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Kinases ◽  
G Protein ◽  
Pertussis Toxin ◽  
Cyclic Nucleotide ◽  
Dependent Protein Kinase ◽  
Kinase C ◽  
Dependent Protein ◽  
Stimulation Of

We examined the possibility that, in addition to stimulation of guanylate cyclase (GC), atrial natriuretic peptide (ANP) also activates phospholipase C (PLC) in cultured rat inner medullary collecting tubule (RIMCT) cells. ANP (10(-12)M) causes marked release of inositol trisphosphate (IP3) at a concentration that does not stimulate GC. Concentrations of ANP that stimulate GC (greater than or equal to 10(-10) M) result in attenuated IP3 release. Similarly, exogenous dibutyryl guanosine 3',5'-cyclic monophosphate (10(-6) M) markedly inhibits the response to 10(-10) M ANP. Inhibition of cyclic nucleotide-dependent protein kinase by H 8, but not inhibition of protein kinase C by H 7, restores the response to 10(-8) and 10(-6) M ANP. Therefore, activation of cyclic nucleotide-dependent protein kinase inhibits ANP-stimulated PLC activity. Activation of protein kinase C by phorbol 12-myristate-13-acetate (PMA) decreases ANP-stimulated IP3 production. Pretreatment with H 7, but not H 8, prevents inhibition by PMA. To explore a potential role for G proteins, we examined the effect of guanine nucleotide analogues on ANP-stimulated IP3 production in saponin-permeabilized cells. ANP-stimulated IP3 production is enhanced by GTP gamma S and is inhibited by GDP beta S. Similarly, preincubation with pertussis toxin prevents ANP-stimulated IP3 release. We conclude that ANP stimulates PLC in RIMCT cells via a pertussis toxin-sensitive G protein. Stimulation of PLC is inhibited on activation of either cyclic nucleotide or Ca2+-phospholipid dependent protein kinases.

scholarly journals Pancreastatin activates protein kinase C by stimulating the formation of 1,2-diacylglycerol in rat hepatocytes

1994 ◽  
Vol 303 (1) ◽  
pp. 51-54 ◽  
Author(s):  
V Sánchez-Margalet ◽  
M Lucas ◽  
R Goberna
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Pertussis Toxin ◽  
Time Course ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Dependent Manner ◽  
Kinase C ◽  
Glucose Output ◽  
Stimulation Of

We describe here the stimulation by pancreastatin of 1,2-diacylglycerol production and protein kinase C activity in liver plasma membrane and isolated hepatocytes. The dose-dependency for the stimulation of both processes was similar to the recently described pattern of glucose output and cytosolic Ca2+ transients produced by pancreastatin. The time course of diacylglycerol production at 30 degrees C showed a rapid increase within 5 min, reaching a maximum at 10 min. Protein kinase C from hepatocytes was dependent on Ca2+ and phosphatidylserine. Neither the pancreastatin-stimulated diacylglycerol production nor the activation of protein kinase C was affected by pretreatment with pertussis toxin. However, the presence of GTP partially inhibited this pancreastatin stimulation of 1,2-diacylglycerol in a dose-dependent manner, although GTP alone stimulates diacylglycerol accumulation. This inhibitory effect of GTP on pancreastatin stimulation of diacylglycerol synthesis was completely abolished by the pretreatment with pertussis toxin. In conclusion, this study provides evidence that pancreastatin stimulates the formation of 1,2-diacylglycerol by a pertussis-toxin-independent mechanism, which may be responsible for the pancreastatin activation of protein kinase C.

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