Nonspecific effects of the pharmacological probes commonly used to analyze signal transduction in rabbit parietal cells

Shh (Sonic hedgehog) regulates gastric epithelial cell differentiation. We reported that incubation of purified canine parietal cells with epidermal growth factor (EGF) for 6–16 h, stimulates H+/K+-ATPase α-subunit gene expression through the activation of Akt. We explored if Shh mediates some of the actions of EGF in the parietal cells. EGF induced a 6-fold increase in Shh expression, measured by Western blots, after 5 h of incubation. This effect was inhibited by both the phosphatidylinositol 3-kinase inhibitor LY294002 and by transduction of the cells with an adenoviral vector expressing dominant negative Akt. EGF stimulated the release of Shh-like immunoreactivity from the parietal cells, after 16 h of incubation. Shh induced H+/K+-ATPase α-subunit gene expression, assessed by Northern blots, it stimulated a luciferase reporter plasmid containing the EGF-responsive sequence (ERE) of the canine H+/K+-ATPase α-subunit gene promoter, and it induced parietal cell nuclear protein binding to the ERE. Gli transcription factors mediate the intracellular actions of Shh. Co-transfection of the parietal cells with the H+/K+-luc plasmid together with one expressing Gli2, induced H+/K+-luciferase activity 5-fold, whereas co-transfection of the cells with the H+/K+-luc plasmid together with one expressing dominant negative Gli2, inhibited EGF induction of H+/K+-luciferase activity. Identical results were observed in the presence of the Shh signal transduction pathway inhibitor, cyclopamine. Transfection of the cells with dominant negative Akt inhibited EGF, but not Shh stimulation of H+/K+-ATPase-luciferase activity. Thus, EGF but not Shh signals through Akt. Preincubation of the cells for 16 h with either Shh or EGF enhanced histamine-stimulated [14C]aminopyrine uptake by 50%. In conclusions, some of the actions of EGF in the parietal cells are mediated by the sequential activation of the Akt and the Shh signal transduction pathways. These effects might represent novel mechanisms mediating the actions of growth factors on gastric epithelial cell differentiation.

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Interaction of signal transduction pathways in mediating acid secretion by rat parietal cells

AJP Cell Physiology ◽

10.1152/ajpcell.1989.256.4.c873 ◽

1989 ◽

Vol 256 (4) ◽

pp. C873-C879 ◽

Cited By ~ 7

Author(s):

J. Ostrowski ◽

K. Bomsztyk

Keyword(s):

Signal Transduction ◽

Acid Secretion ◽

Phospholipase C ◽

Plasma Membranes ◽

Signal Transduction Pathway ◽

Secretory Activity ◽

Parietal Cells ◽

Cyclic Monophosphate ◽

Dose Dependent Fashion

To examine the role of protein kinase C (PKC) on the acid secretory activity of isolated rat parietal cells, histamine-and dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP)-stimulated [14C]aminopyrine accumulation was determined in the presence of agents that redistribute PKC activity to plasma membranes. Phorbol 12-myristate 13-acetate (PMA), 1-oleoyl-2-acetylglycerol (OAG), and phospholipase C inhibited, in a dose-dependent fashion, histamine- and DBcAMP-stimulated [14C]aminopyrine accumulation. Because PKC inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) reversed the effect, the results suggest that inhibition of histamine- or DBcAMP-stimulated [14C]aminopyrine accumulation induced by PMA, OAG, or phospholipase C was caused by increased activity of PKC in plasma membrane. To determine where in the cascade of events PKC inhibits acid secretion, histamine-, cholera toxin-, and forskolin-stimulated [14C]aminopyrine accumulation was measured with or without PMA. Because the percent of inhibition by PMA of [14C]aminopyrine accumulation was similar with the three secretagogues, the results suggest that PKC inhibits acid secretion at a point beyond adenosine 3',5'-cyclic monophosphate (cAMP) production. This was supported by the fact that PMA had no effect on histamine-stimulated production of cAMP and by the finding that activation of PKC had the same effect on histamine- or DBcAMP-stimulated [14C]aminopyrine accumulation. Histamine and DBcAMP inhibited PKC activity, suggesting a reciprocal interaction between PKC and histamine-triggered signal transduction pathway.

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Regulation and function of the sonic hedgehog (Shh) signal transduction pathway in isolated gastric parietal cells

Gastroenterology ◽

10.1016/s0016-5085(03)80490-0 ◽

2003 ◽

Vol 124 (4) ◽

pp. A100

Author(s):

Vinzenz Stepan ◽

Saravanan Ramamoorthy ◽

Hildegard Nitsche ◽

Jung Park ◽

Andrea Todisco

Keyword(s):

Signal Transduction ◽

Sonic Hedgehog ◽

Signal Transduction Pathway ◽

Parietal Cells ◽

Transduction Pathway ◽

And Function ◽

Gastric Parietal Cells

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Ultrastructural aspects of olfactory signal transduction and its development

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010016844x ◽

1994 ◽

Vol 52 ◽

pp. 142-143

Author(s):

Bert Ph. M. Menco

Keyword(s):

Signal Transduction ◽

Olfactory Receptor ◽

Receptor Cell ◽

Freeze Substitution ◽

Luminal Surface ◽

Tissue Sections ◽

Olfactory Receptor Cells ◽

Receptor Cells ◽

Olfactory Signal ◽

Odor Molecule

Vertebrate olfactory receptor cells are specialized neurons that have numerous long tapering cilia. The distal parts of these cilia line the interface between the external odorous environment and the luminal surface of the olfactory epithelium. The length and number of these cilia results in a large surface area that presumably increases the chance that an odor molecule will meet a receptor cell. Advanced methods of cryoprepration and immuno-gold labeling were particularly useful to preserve the delicate ultrastructural and immunocytochemical features of olfactory cilia required for localization of molecules involved in olfactory signal-transduction. We subjected olfactory tissues to freeze-substitution in acetone (unfixed tissues) or methanol (fixed tissues) followed by low temperature embedding in Lowicryl K11M for that purpose. Tissue sections were immunoreacted with several antibodies against proteins that are presumably important in olfactory signal-transduction.

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