Two G-proteins act in series to control stimulus-secretion coupling in mast cells: use of neomycin to distinguish between G-proteins controlling polyphosphoinositide phosphodiesterase and exocytosis.

Provision of GTP (or other nucleotides capable of acting as ligands for activation of G-proteins) together with Ca2+ (at micromolar concentrations) is both necessary and sufficient to stimulate exocytotic secretion from mast cells permeabilized with streptolysin-O. GTP and its analogues, through their interactions with Gp, also activate polyphosphoinositide-phosphodiesterase (PPI-pde generating inositol 1,4,5-trisphosphate and diglyceride [DG]). We have used mast cells labeled with [3H]inositol to test whether the requirement for GTP in exocytosis is an expression of Gp activity through the generation of DG and consequent activation of protein kinase C, or whether GTP is required at a later stage in the stimulus secretion sequence. Neomycin (0.3 mM) inhibits activation of PPI-pde, but maximal secretion due to optimal concentrations of guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) can still be evoked in its presence. When ATP is also provided the concentration requirement for GTP-gamma-S in support of exocytosis is reduced. This sparing effect of ATP is nullified when the PPI-pde reaction is inhibited by neomycin. We argue that the sparing effect of ATP occurs as a result of enhancement of DG production and through its action as a phosphoryl donor in the reactions catalyzed by protein kinase C.

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Phosphatidylinositol transfer proteins and protein kinase C make separate but non-interacting contributions to the phosphorylation state necessary for secretory competence in rat mast cells

Biochemical Journal ◽

10.1042/bj3560287 ◽

2001 ◽

Vol 356 (1) ◽

pp. 287-296 ◽

Cited By ~ 4

Author(s):

Jef A. PINXTEREN ◽

Bastien D. GOMPERTS ◽

Danise ROGERS ◽

Scott E. PHILLIPS ◽

Peter E. R. TATHAM ◽

...

Keyword(s):

Protein Kinase C ◽

Mast Cells ◽

Protein Kinase ◽

Aminoglycoside Antibiotic ◽

Pleckstrin Homology Domain ◽

Kinase C ◽

Streptolysin O ◽

Regulatory Machinery ◽

Phosphatidylinositol Transfer ◽

Phosphatidylinositol Transfer Proteins

Mast cells permeabilized by streptolysin O undergo exocytosis when stimulated with Ca2+ and guanosine 5′-[γ-thio]triphosphate but become progressively refractory to this stimulus if it is delayed. This run-down of responsiveness occurs over a period of 20–30min, during which the cells leak soluble and tethered proteins. We show here that withdrawal of ATP during the process of run-down is strongly inhibitory but that as little as 25μM ATP can extend responsiveness significantly; this effect is maximal at 50μM. When phosphatidylinositol transfer proteins (PITPs) are provided to cells at the time of permeabilization, run-down is retarded. We conclude that in the presence of ATP they convey substrates for phosphorylation that are essential for exocytosis and thus interact with the regulatory machinery. Furthermore, we show that PITPα and PITPβ have additive effects in this mechanism, suggesting that they are not functionally redundant. Alternatively, secretion from run-down cells can be inhibited by the aminoglycoside antibiotic neomycin, which is understood to bind to phosphoinositide headgroups, and by a PH (pleckstrin homology) domain polypeptide that binds phosphoinositides. The apparent displacement of neomycin by exogenous PITPs suggests that these proteins screen essential lipids. Secretion from run-down cells is also inhibited by 1-O-hexadecyl-2-O-methyl-rac-glycerol (AMG-C16), an inhibitor of protein kinase C. The lack of synergy between neomycin and AMG-C16 suggests that protein kinase C independently provides a second essential component through protein phosphorylation and that there are two independent phosphorylation pathways necessary for secretion competence.

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The Streptococcal Exotoxin Streptolysin O Activates Mast Cells To Produce Tumor Necrosis Factor Alpha by p38 Mitogen-Activated Protein Kinase- and Protein Kinase C-Dependent Pathways

Infection and Immunity ◽

10.1128/iai.71.11.6171-6177.2003 ◽

2003 ◽

Vol 71 (11) ◽

pp. 6171-6177 ◽

Cited By ~ 37

Author(s):

Michael Stassen ◽

Christian Müller ◽

Christoph Richter ◽

Christine Neudörfl ◽

Lothar Hültner ◽

...

Keyword(s):

Protein Kinase C ◽

Mast Cells ◽

Protein Kinase ◽

Map Kinase ◽

P38 Map Kinase ◽

Necrosis Factor Alpha ◽

Kinase C ◽

Streptolysin O ◽

Tnf Α ◽

Mitogen Activated Protein

ABSTRACT Streptolysin O (SLO), a major virulence factor of pyogenic streptococci, binds to cholesterol in the membranes of eukaryotic cells and oligomerizes to form large transmembrane pores. While high toxin doses are rapidly cytocidal, low doses are tolerated because a limited number of lesions can be resealed. Here, we report that at sublethal doses, SLO activates primary murine bone marrow-derived mast cells to degranulate and to rapidly induce or enhance the production of several cytokine mRNAs, including tumor necrosis factor alpha (TNF-α). Mast cell-derived TNF-α plays an important protective role in murine models of acute inflammation, and the production of this cytokine was analyzed in more detail. Release of biologically active TNF-α peaked ∼4 h after stimulation with SLO. Production of TNF-α was blunted upon depletion of protein kinase C by pretreatment of the cells with phorbol-12 myristate-13 acetate. Transient permeabilization of mast cells with SLO also led to the activation of the stress-activated protein kinases p38 mitogen-activated protein (MAP) kinase and c-jun N-terminal kinase (JNK), and inhibition of p38 MAP kinase markedly reduced production of TNF-α. In contrast, secretion of preformed granule constituents triggered by membrane permeabilization was not dependent on p38 MAP kinase or on protein kinase C. Thus, transcriptional activation of mast cells following transient permeabilization might contribute to host defense against infections via the beneficial effects of TNF-α. However, hyperstimulation of mast cells might also lead to overproduction of TNF-α, which would then promote the development of toxic streptococcal syndromes.

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Amylase release from streptolysin O-permeabilized pancreatic acini

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1990.259.2.g157 ◽

1990 ◽

Vol 259 (2) ◽

pp. G157-G164 ◽

Cited By ~ 4

Author(s):

M. Kitagawa ◽

J. A. Williams ◽

R. C. De Lisle

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Protein S ◽

Bacterial Toxin ◽

Amylase Secretion ◽

Amylase Release ◽

Pancreatic Acini ◽

Kinase C ◽

Streptolysin O ◽

Gamma S

Intracellular mediators of exocytosis were investigated using isolated mouse pancreatic acini permeabilized with the bacterial toxin streptolysin O (SLO). Permeabilization was demonstrated by fluorescent staining with ethidium bromide and fluorescein diacetate and release of cytoplasmic lactate dehydrogenase. When SLO-permeabilized acini were incubated at 37 degrees C in Ca2(+)-EGTA buffers containing MgATP, amylase secretion was Ca2+ dependent with an EC50 of 0.40 microM Ca2+ and a maximally effective Ca2+ concentration of 1 microM. Maximal amylase secretion was 330% of that in Ca2(+)-free buffer (basal). The nonhydrolyzable GTP analogue guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 30 microM) increased the maximal secretion to 451% of basal in the presence of 1 microM Ca2+ and decreased the EC50 to 0.14 microM Ca2+. Removal of ATP plus addition of antimycin A and 2-deoxy-D-glucose inhibited Ca2(+)-dependent, GTP gamma S-enhanced amylase secretion by 56%. The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA; 1 microM) also enhanced maximal secretion to 450% of basal and decreased the EC50 to 0.18 microM Ca2+. Enhancement of amylase secretion by submaximal concentrations of GTP gamma S or TPA was inhibited by the protein kinase C inhibitor staurosporine. These results suggest that Ca2+ stimulation of amylase secretion is potentiated by activation of protein kinase C. However, the enhancement of secretion by GTP gamma S and TPA was additive at their maximally effective concentrations, suggesting that another G protein(s) maybe involved in the terminal steps of exocytosis.

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