Avtor/Urednik		Kreft, Marko
Naslov		Vloga GTP-beljakovin pri eksocitozi in endocitozi podganjih melanotrofov
Tip		monografija
Kraj izdaje		Ljubljana
Založnik		Medicinska fakulteta
Leto izdaje		1999
Obseg		str. 58
Jezik		slo
Abstrakt		Proteins able to bind and hydrolyze GTP can be divided into different families including trimeric G proteins and Ras-related low molecular mass G proteins. Trimeric G proteins have been found associated with the membrane of secretory granules in various secretory cells (Ahnert-Hilger et al.,1994; Konrad et al.,1995; Vitale et al.,1996). Thus, besides playing a role in the signal transduction cascade operating at the plasma membrane, trimeric G-proteins may also be involved in the regulation of calcium-evoked secretion. Indeed, the participation of Gi and Go proteins in the late stages of exocytosis has been demonstrated in mast cells (Aridor et al.,1993), insulin-secreting cells (Lang et al.,1995) and chromaffin cells. (Vitale et al.,1993,1994a; Gasman et al.,1997). The precise role of G proteins at specific stages of the exocytotic and endocytotic machinery remains to be determined. Our aim was to study the role of Gi3 and Gi1/2 in regulated secretion in rat melanotrophs. By immunocytochemistry, we provide the evidence that in rat melanotrophs Gi3 resides mainly in the plasma membrane whereas Gi1/2 is preferentially associated with the membrane of secretory granules. We used patch-clamp membrane capacitance measurements to monitor exocytotic activity in single rat melanotrophs (Neher and Marty, 1982). Mastoparan, a specific activator of trimeric G-proteins was found to enhance calcium-dependent secretory activity in rat melanotrophs. We introduced the synthetic peptides corresponding to the C-terminal domain of the a- subunit of Gi3- and Gi1/2-proteins. Peptide Gi3 but not Gi1/2 specifically blocked the mastoparan-stimulated secretory activity, which indicates an involvement of a trimeric Gi3-protein in secretory activity. In a series of experiments, cells were stimulated by increasing cytosolic calcium quickly and uniformly using flash photolysis of caged Ca2+ (Neher and Zucker, 1993). (Abstract truncated at 2000 characters).
Deskriptorji		G-PROTEINS EXOCYTOSIS ENDOCYTOSIS PITUITARY GLAND RATS, WISTAR CELLS, CULTURED IMMUNOHISTOCHEMISTRY PATCH-CLAMP TECHNIQUES WASP VENOMS CALCIUM PEPTIDES FLUORESCENT ANTIBODY TECHNIQUE