Avtor/Urednik		Kreft, Marko; Gasman, Stephane; Chasserot-Golaz, Sylvette; Kuster, Vlasta; Rupnik, Marjan; Sikdar, SK; Bader, Marie-France; Zorec, Robert
Naslov		The heterotrimeric Gi3 protein acts in slow but not in fast exocytosis of rat melanotrophs
Tip		članek
Vir		J Cell Sci
Vol. in št.		Letnik 112, št. 22
Leto izdaje		1999
Obseg		str. 4143-50
Jezik		eng
Abstrakt		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.
Deskriptorji		G-PROTEINS EXOCYTOSIS PITUITARY GLAND RATS IMMUNOHISTOCHEMISTRY MICROSCOPY, CONFOCAL PATCH-CLAMP TECHNIQUES CELLS, CULTURED CALCIUM MICROSCOPY, FLUORESCENCE WASP VENOMS KINETICS