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| Item Type: | Article |
|---|---|
| Title: | Exocytosis from permeabilized bovine adrenal chromaffin cells is differently modulated by guanosine 5'-[gamma-thio]triphosphate and guanosine 5'-[beta gamma-imido]triphosphate. Evidence for the involvement of various guanine nucleotide-binding proteins |
| Creators Name: | Ahnert-Hilger, G. and Wegenhorst, U. and Stecher, B. and Spicher, K. and Rosenthal, W. and Gratz, M. |
| Abstract: | 1. In bovine adrenal chromaffin cells made permeable either to molecules less than or equal to 3 kDa with alphatoxin or to proteins less than or equal to 150 kDa with streptolysin O, the GTP analogues guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG) and guanosine 5'-[gamma-thio]triphosphate (GTP[S]) differently modulated Ca(2+)-stimulated exocytosis. 2. In alphatoxin-permeabilized cells, p[NH]ppG up to 20 microM activated Ca(2+)-stimulated exocytosis. Higher concentrations had little or no effect. At a free Ca2+ concentration of 5 microM, 7 microM-p[NH]ppG stimulated exocytosis 6-fold. Increasing the free Ca2+ concentration reduced the effect of p[NH]ppG. Pretreatment of the cells with pertussis toxin prevented the activation of the Ca(2+)-stimulated exocytosis by p[NH]ppG. 3. In streptolysin O-permeabilized cells, p[NH]ppG did not activate, but rather inhibited Ca(2+)-dependent catecholamine release under all conditions studied. In the soluble cytoplasmic material that escaped during permeabilization with streptolysin O, different G-protein alpha-subunits were detected using an appropriate antibody. Around 15% of the cellular alpha-subunits were detected in the supernatant of permeabilized control cells. p[NH]ppG or GTP[S] stimulated the release of alpha-subunits 2-fold, causing a loss of about 30% of the cellular G-protein alpha-subunits under these conditions. Two of the alpha-subunits in the supernatant belonged to the G(o) type, as revealed by an antibody specific for G(o) alpha. 4. GTP[S], when present alone during stimulation with Ca2+, activated exocytosis in a similar manner to p[NH]ppG. Upon prolonged incubation, GTP[S], in contrast to p[NH]ppG, inhibited Ca(2+)-induced exocytosis from cells permeabilized by either of the pore-forming toxins. This effect was resistant to pertussin toxin. 5. The p[NH]ppG-induced activation of Ca(2+)-stimulated release from alphatoxin-permeabilized chromaffin cells may be attributed to one of the heterotrimeric G-proteins lost during permeabilization with streptolysin O. The inhibitory effect of GTP[S] on exocytosis is apparently not mediated by G-protein alpha-subunits, but by another GTP-dependent process still occurring after permeabilization with streptolysin O. |
| Keywords: | Adrenal Glands, Bacterial Toxins, Calcium, Cell Membrane Permeability, Cultured Cells, Chromaffin Granules, Polyacrylamide Gel Electrophoresis, Exocytosis, GTP-Binding Proteins, Guanosine 5'-O-(3-Thiotriphosphate), Guanylyl Imidodiphosphate, Hemolysin Proteins, Streptolysins, Animals, Cattle |
| Source: | Biochemical Journal |
| ISSN: | 0264-6021 |
| Publisher: | Portland Press |
| Volume: | 284 |
| Number: | Pt 2 |
| Page Range: | 321-326 |
| Date: | 1992 |
| Official Publication: | http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1132640&blobtype=pdf |
| PubMed: | View item in PubMed |
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