scholarly journals Olfactory desensitization requires membrane targeting of receptor kinase mediated by beta gamma-subunits of heterotrimeric G proteins.

1994 ◽  
Vol 269 (1) ◽  
pp. 37-40
Author(s):  
I. Boekhoff ◽  
J. Inglese ◽  
S. Schleicher ◽  
W.J. Koch ◽  
R.J. Lefkowitz ◽  
...  
Keyword(s):  
G Proteins ◽  
Membrane Targeting ◽  
Heterotrimeric G Proteins ◽  
Receptor Kinase ◽  
Gamma Subunits

scholarly journals Differential distribution of alpha subunits and beta gamma subunits of heterotrimeric G proteins on Golgi membranes of the exocrine pancreas.

1996 ◽  
Vol 133 (5) ◽  
pp. 1027-1040 ◽  
Author(s):  
S P Denker ◽  
J M McCaffery ◽  
G E Palade ◽  
P A Insel ◽  
M G Farquhar
Keyword(s):  
G Proteins ◽  
Exocrine Pancreas ◽  
Protein S ◽  
Beta Subunits ◽  
Heterotrimeric G Proteins ◽  
Differential Distribution ◽  
Alpha Subunits ◽  
Golgi Membranes ◽  
Gamma Subunits ◽  
G Alpha Q

Heterotrimeric G proteins are well known to be involved in signaling via plasma membrane (PM) receptors. Recent data indicate that heterotrimeric G proteins are also present on intracellular membranes and may regulate vesicular transport along the exocytic pathway. We have used subcellular fractionation and immunocytochemical localization to investigate the distribution of G alpha and G beta gamma subunits in the rat exocrine pancreas which is highly specialized for protein secretion. We show that G alpha s, G alpha i3 and G alpha q/11 are present in Golgi fractions which are > 95% devoid of PM. Removal of residual PM by absorption on wheat germ agglutinin (WGA) did not deplete G alpha subunits. G alpha s was largely restricted to TGN-enriched fractions by immunoblotting, whereas G alpha i3 and G alpha q/11 were broadly distributed across Golgi fractions. G alpha s did not colocalize with TGN38 or caveolin, suggesting that G alpha s is associated with a distinct population of membranes. G beta subunits were barely detectable in purified Golgi fractions. By immunofluorescence and immunogold labeling, G beta subunits were detected on PM but not on Golgi membranes, whereas G alpha s and G alpha i3 were readily detected on both Golgi and PM. G alpha and G beta subunits were not found on membranes of zymogen granules. These data indicate that G alpha s, G alpha q/11, and G alpha i3 associate with Golgi membranes independent of G beta subunits and have distinctive distributions within the Golgi stack. G beta subunits are thought to lock G alpha in the GDP-bound form, prevent it from activating its effector, and assist in anchoring it to the PM. Therefore the presence of free G alpha subunits on Golgi membranes has several important functional implications: it suggests that G alpha subunits associated with Golgi membranes are in the active, GTP-bound form or are bound to some other unidentified protein(s) which can substitute for G beta gamma subunits. It further implies that G alpha subunits are tethered to Golgi membranes by posttranslational modifications (e.g., palmitoylation) or by binding to another protein(s).

scholarly journals A G protein-gated K channel is activated via beta 2-adrenergic receptors and G beta gamma subunits in Xenopus oocytes.

1995 ◽  
Vol 105 (3) ◽  
pp. 421-439 ◽  
Author(s):  
N F Lim ◽  
N Dascal ◽  
C Labarca ◽  
N Davidson ◽  
H A Lester
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Xenopus Oocytes ◽  
K Channel ◽  
Intracellular Camp ◽  
Heterotrimeric G Proteins ◽  
M2 Muscarinic Receptor ◽  
Gamma Subunits ◽  
Beta 2 ◽  
Inwardly Rectifying

In many tissues, inwardly rectifying K channels are coupled to seven-helix receptors via the Gi/Go family of heterotrimeric G proteins. This activation proceeds at least partially via G beta gamma subunits. These experiments test the hypothesis that G beta gamma subunits activate the channel even if released from other classes of heterotrimeric G proteins. The G protein-gated K channel from rat atrium, KGA/GIRK1, was expressed in Xenopus oocytes with various receptors and G proteins. The beta 2-adrenergic receptor (beta 2AR), a Gs-linked receptor, activated large KGA currents when the alpha subunit, G alpha s, was also overexpressed. Although G alpha s augmented the coupling between beta 2AR and KGA, G alpha s also inhibited the basal, agonist-independent activity of KGA. KGA currents stimulated via beta 2AR activated, deactivated, and desensitized more slowly than currents stimulated via Gi/Go-linked receptors. There was partial occlusion between currents stimulated via beta 2AR and the m2 muscarinic receptor (a Gi/Go-linked receptor), indicating some convergence in the mechanism of activation by these two receptors. Although stimulation of beta 2AR also activates adenylyl cyclase and protein kinase A, activation of KGA via beta 2AR is not mediated by this second messenger pathway, because direct elevation of intracellular cAMP levels had no effect on KGA currents. Experiments with other coexpressed G protein alpha and beta gamma subunits showed that (a) a constitutively active G alpha s mutant did not suppress basal KGA currents and was only partially as effective as wild type G alpha s in coupling beta 2AR to KGA, and (b) beta gamma subunits increased basal KGA currents. These results reinforce present concepts that beta gamma subunits activate KGA, and also suggest that beta gamma subunits may provide a link between KGA and receptors not previously known to couple to inward rectifiers.

scholarly journals The role of heterotrimeric G proteins in the control of symbiosis development in legume plants

2020 ◽  
Vol 23 ◽  
pp. 03004
Author(s):  
Andrey D. Bovin ◽  
Irina V. Leppyanen ◽  
Olga A. Pavlova ◽  
Elena A. Dolgikh
Keyword(s):  
Gene Expression ◽  
G Proteins ◽  
Heterotrimeric G Proteins ◽  
Subunit Gene ◽  
Gene Suppression ◽  
Gamma Subunits ◽  
Genes Encoding ◽  
Specific Proteins ◽  
Alpha Beta

Heterotrimeric G proteins are involved in the regulation of signaling pathways in eukaryotes. Previously, the data about possible participation of heterotrimeric G proteins in the regulation of nodulation in legumes were obtained, however, specific proteins, their composition and role in this process remain poorly understood. In this work searching of the genes encoding the alpha, beta, and gamma subunits of heterotrimeric G proteins based on an analysis of the Pisum sativum L. genome was performed, as well as the dynamics of the gene expression encoding the particular subunits of G proteins in the process of symbiosis was studied. In addition, a significant effect of beta 1-subunit gene suppression by RNA interference on the nodulation process was revealed.

Selectivity in signal transduction determined by gamma subunits of heterotrimeric G proteins

Science ◽  
1993 ◽  
Vol 259 (5096) ◽  
pp. 832-834 ◽  
Author(s):  
C Kleuss ◽  
H Scherubl ◽  
J Hescheler ◽  
G Schultz ◽  
B Wittig
Keyword(s):  
Signal Transduction ◽  
G Proteins ◽  
Heterotrimeric G Proteins ◽  
Gamma Subunits

Association of the gamma12 subunit of G proteins with actin filaments

1997 ◽  
Vol 110 (13) ◽  
pp. 1503-1511
Author(s):  
H. Ueda ◽  
S. Saga ◽  
H. Shinohara ◽  
R. Morishita ◽  
K. Kato ◽  
...  
Keyword(s):  
G Proteins ◽  
Actin Filaments ◽  
Calf Serum ◽  
C6 Glioma Cells ◽  
Heterotrimeric G Proteins ◽  
Differential Distribution ◽  
Functional Differences ◽  
Gamma Subunits ◽  
Triton X

Recent studies have suggested an association between heterotrimeric G proteins, which play a major role in transmembrane signal transduction, and intracellular components. We therefore examined the subcellular localization of isoforms of G protein gamma subunits in Swiss 3T3 and C6 glioma cells, mainly containing the gamma5 and gamma12 subunits. Immunocytochemical double staining with phalloidin showed co-localization of the gamma12 subunit with actin filaments (F-actin), while the gamma5 co-localized with vinculin, suggesting an association with focal adhesion. Pretreatment of cells with Triton X-100 eliminated the gamma5 but not the gamma12 staining. Co-localization of gamma12 and F-actin was preserved when F-actin was disorganized with cytochalasin D or reorganized using fetal calf serum. Large amounts of gamma12 were recovered in the vimentin- and tubulin-free F-actin-rich fraction prepared from crude cytoskeleton preparations by double depolymerization-repolymerization. Co-localization of Gi2alpha, beta and gamma12 in the F-actin-rich fraction suggested the existence of gamma12 as a betagamma or heterotrimeric complex. Furthermore, purified betagamma12 was found to associate with F-actin in vitro more tightly than betagamma5. These results strongly suggest that the gamma12 subunit associates with F-actin in cells. The observed differential distribution of gamma12 and gamma5 implies functional differences for the two gamma subunits.

scholarly journals Localization of a heterotrimeric G protein gamma subunit to focal adhesions and associated stress fibers.

1994 ◽  
Vol 126 (3) ◽  
pp. 811-819 ◽  
Author(s):  
C A Hansen ◽  
A G Schroering ◽  
D J Carey ◽  
J D Robishaw
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Focal Adhesion ◽  
Cardiac Fibroblasts ◽  
Focal Adhesions ◽  
Heterotrimeric G Proteins ◽  
Gamma Subunit ◽  
Surface Receptors ◽  
Gamma Subunits ◽  
Dual Staining

Signal transducing heterotrimeric G proteins are responsible for coupling a large number of cell surface receptors to the appropriate effector(s). Of the three subunits, 16 alpha, 4 beta, and 5 gamma subunits have been characterized, indicating a potential for over 300 unique combinations of heterotrimeric G proteins. To begin deciphering the unique G protein combinations that couple specific receptors with effectors, we examined the subcellular localization of the gamma subunits. Using anti-peptide antibodies specific for each of the known gamma subunits, neonatal cardiac fibroblasts were screened by standard immunocytochemistry. The anti-gamma 5 subunit antibody yielded a highly distinctive pattern of intensely fluorescent regions near the periphery of the cell that tended to protrude into the cell in a fibrous pattern. Dual staining with anti-vinculin antibody showed co-localization of the gamma 5 subunit with vinculin. In addition, the gamma 5 subunit staining extended a short distance out from the vinculin pattern along the protruding stress fiber, as revealed by double staining with phalloidin. These data indicated that the gamma 5 subunit was localized to areas of focal adhesion. Dual staining of rat aortic smooth muscle cells and Schwann cells also indicated co-localization of the gamma 5 subunit and vinculin, suggesting that the association of the gamma 5 subunit with areas of focal adhesion was wide-spread.

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