Trimeric G-proteins of the trans-Golgi network are involved in the formation of constitutive secretory vesicles and immature secretory granules

Abstract

Non-hydrolysable analogues of GTP, such as GTPγS and GMP-PNP, have previously been shown to inhibit the formation of constitutive secretory vesicles (CSVs) and immature secretory granules (ISGs) from the trans-Golgi network (TGN). Using a cell-free system, we show here that the formation of these vesicles is also inhibited by [AIF 4], a compound known to act on trimeric G-proteins. Addition of highly purified G-protein βγ subunits stimulated, in a differential manner, the cell-free formation of both CSVs and ISGs. ADP-ribosylation experiments revealed the presence of a pertussis toxin-sensitive G-protein α subunit in the TGN. We conclude that trimeric G-proteins regulate the formation of secretory vesicles from the TGN.