Author/Editor | Kreft, Marko; Gasman, Stephane; Chasserot-Golaz, Sylvette; Kuster, Vlasta; Rupnik, Marjan; Sikdar, SK; Bader, Marie-France; Zorec, Robert | |
Title | The heterotrimeric Gi3 protein acts in slow but not in fast exocytosis of rat melanotrophs | |
Type | članek | |
Source | J Cell Sci | |
Vol. and No. | Letnik 112, št. 22 | |
Publication year | 1999 | |
Volume | str. 4143-50 | |
Language | eng | |
Abstract | Besides having a role in signal transduction some trimeric G-proteins may be involved in a late stage of exocytosis. Using immunocytochemistry and confocal microscopy we found that Gi3-protein resides mainly in the plasma membrane, whereas Gi1/2-protein is preferentially associated with secretory granules. To study the function of trimeric Gi3- and Gi1/2-proteins, secretory responses in single rat melanotrophs were monitored by patch-clamp membrane capacitance measurements. We report here that mastoparan, an activator of trimeric G-proteins, enhances calcium-induced secretory activity in rat melanotrophs. The introduction of synthetic peptides corresponding to the C-terminal domain of the a-subunit of Gi3- and Gi1/2- proteins indicated that Gi3 peptide specifically blocked the mastoparan-stimulated secretory activity, which indicates an involvement of a trimeric Gi3-protein in mastoparan-stimulated secretory activity. Flash photolysis of caged Ca 2+-elicited biphasic capacitance increasesconsisting of a fast and a slower component. Injection of anti-Gi3 antibodies selectively inhibited the slow but not the fast component of secretory activity in rat melanotrophs. We propose that the plasma membrane-bound Gi3-protein may be involved in regulated secretion by specifically controlling the slower kinetic component of exocytosis. | |
Descriptors | G-PROTEINS EXOCYTOSIS PITUITARY GLAND RATS IMMUNOHISTOCHEMISTRY MICROSCOPY, CONFOCAL PATCH-CLAMP TECHNIQUES CELLS, CULTURED CALCIUM MICROSCOPY, FLUORESCENCE WASP VENOMS KINETICS |