A heterotrimeric G protein, G alpha i-3, on Golgi membranes regulates the secretion of a heparan sulfate proteoglycan in LLC-PK1 epithelial cells.

Abstract

Abstract. A heterotrimeric Gai subunit, «i-3, is localized on Golgi membranes in LLC-PKI and NRK epithelial cells where it colocalizes with mannosidase II by immunofluorescence . The M-3 was found to be localized on the cytoplasmic face of Golgi cisternae and it was distributed across the whole Golgi stack. The a;_3 subunit is found on isolated rat liver Golgi membranes by Western blotting and Gai-3 on the Golgi apparatus is ADP ribosylated by pertussis toxin. LLC-PKI cells were stably transfected with GO ;-3 on an MT1, inducible promoter in order to overexpress ai-3 on Golgi membranes. The intracellular processing and

High level expression of transfected G protein αi3 subunit is required for plasma membrane targeting and adenylyl cyclase inhibition in NIH 3T3 fibroblasts

“…In the latter case, 3-fold expression of wild-type ~3 slowed the rate of constitutively secreted proteoglyean through the Golgi apparatus, an observation that is consistent with a role for Gi3 as a regulator of Golgi trafficking. A mechanism for such activity is unknown, although recent reports have implicated a heterotrimerie G protein in the regulation of coat proteins associated with vesicular transport [21][22][23][24]. We found that rat and murine fibrob~asts show an apparently exclusive Golgi localization for ~i3 (B.S.…”

“…Yet, subpopulations of cx~ subunits can be found in the eytosol and in association with subcellular organelles or cytoskeletal elements [14][15][16][17][18][19]. Particularly relevant is the observation that the ~ subunit of G~3 has been localized to both the Golgi and apical plasma membrane border in renal epithelial cells but is almost exclusively restricted to the Golgi apparatus in LLCPkl cells [20,21]. In the latter case, 3-fold expression of wild-type ~3 slowed the rate of constitutively secreted proteoglyean through the Golgi apparatus, an observation that is consistent with a role for Gi3 as a regulator of Golgi trafficking.…”

Interaction of the protein nucleobindin with Gαi2, as revealed by the yeast two‐hybrid system

“…One of these proteins, G~i3, has been localized not only to the plasma membrane but also to the Golgi apparatus, where it appears to be involved in the secretion of proteins [5]. G~i2, which interacts with adenylyl cyclase, causes neoplastic transformation of some types of cells when mutated to a constitutively active state [6].…”

Mutational and secondary structural analysis of the basolateral sorting signal of the polymeric immunoglobulin receptor.

“…Alternatively, the positively charged residues may directly interact with components of the basolateral sorting machinery. Recent observations proposed that heterotrimeric G~ proteins play a role in targeting from the TGN to the basolateral surface (Stow et al, 1991;Bomsel and Mostov, 1992;Pimplikar and Simons, 1993). This class of G proteins is known to be activated by positively charged peptides, such as the wasp venom mastoparan.…”