scholarly journals Phospholipase A2 Is Required for PIN-FORMED Protein Trafficking to the Plasma Membrane in the Arabidopsis Root

2010 ◽  
Vol 22 (6) ◽  
pp. 1812-1825 ◽  
Author(s):  
Ok Ran Lee ◽  
Soo Jin Kim ◽  
Hae Jin Kim ◽  
Jeum Kyu Hong ◽  
Stephen Beungtae Ryu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Phospholipase A2 ◽  
Protein Trafficking ◽  
Arabidopsis Root

scholarly journals Ykt6 membrane-to-cytosol cycling regulates exosomal Wnt secretion

2018 ◽  
Author(s):  
Karen Linnemannstöns ◽  
Pradhipa Karuna M ◽  
Leonie Witte ◽  
Jeanette Clarissa Kittel ◽  
Adi Danieli ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Wnt Signaling ◽  
Signaling Pathways ◽  
Long Range ◽  
Protein Trafficking ◽  
Secretory Pathway ◽  
Multivesicular Bodies ◽  
Phosphorylation Sites ◽  
Wnt Proteins ◽  
C Terminus

Protein trafficking in the secretory pathway, for example the secretion of Wnt proteins, requires tight regulation. These ligands activate Wnt signaling pathways and are crucially involved in development and disease. Wnt is transported to the plasma membrane by its cargo receptor Evi, where Wnt/Evi complexes are endocytosed and sorted onto exosomes for long-range secretion. However, the trafficking steps within the endosomal compartment are not fully understood. The promiscuous SNARE Ykt6 folds into an auto-inhibiting conformation in the cytosol, but a portion associates with membranes by its farnesylated and palmitoylated C-terminus. Here, we demonstrate that membrane detachment of Ykt6 is essential for exosomal Wnt secretion. We identified conserved phosphorylation sites within the SNARE domain of Ykt6, which block Ykt6 cycling from the membrane to the cytosol. In Drosophila, Ykt6-RNAi mediated block of Wg secretion is rescued by wildtype but not phosphomimicking Ykt6. The latter accumulates at membranes, while wildtype Ykt6 regulates Wnt trafficking between the plasma membrane and multivesicular bodies. Taken together, we show that a regulatory switch in Ykt6 fine-tunes sorting of Wnts in endosomes.

Dual-color visualization of trans-Golgi network to plasma membrane traffic along microtubules in living cells

1999 ◽  
Vol 112 (1) ◽  
pp. 21-33 ◽  
Author(s):  
D. Toomre ◽  
P. Keller ◽  
J. White ◽  
J.C. Olivo ◽  
K. Simons
Keyword(s):  
Plasma Membrane ◽  
Protein Trafficking ◽  
Membrane Traffic ◽  
Living Cells ◽  
Tubular Structures ◽  
Trans Golgi Network ◽  
Vesicular Stomatitis ◽  
Golgi Network ◽  
Color Visualization

The mechanisms and carriers responsible for exocytic protein trafficking between the trans-Golgi network (TGN) and the plasma membrane remain unclear. To investigate the dynamics of TGN-to-plasma membrane traffic and role of the cytoskeleton in these processes we transfected cells with a GFP-fusion protein, vesicular stomatitis virus G protein tagged with GFP (VSVG3-GFP). After using temperature shifts to block VSVG3-GFP in the endoplasmic reticulum and subsequently accumulate it in the TGN, dynamics of TGN-to-plasma membrane transport were visualized in real time by confocal and video microscopy. Both small vesicles (<250 nm) and larger vesicular-tubular structures (>1.5 microm long) are used as transport containers (TCs). These TCs rapidly moved out of the Golgi along curvilinear paths with average speeds of approximately 0.7 micrometer/second. Automatic computer tracking objectively determined the dynamics of different carriers. Fission and fusion of TCs were observed, suggesting that these late exocytic processes are highly interactive. To directly determine the role of microtubules in post-Golgi traffic, rhodamine-tubulin was microinjected and both labeled cargo and microtubules were simultaneously visualized in living cells. These studies demonstrated that exocytic cargo moves along microtubule tracks and reveals that carriers are capable of switching between tracks.

Modulation of plasma membrane H+-ATPase from oat roots by lysophosphatidylcholine, free fatty acids and phospholipase A2

1988 ◽  
Vol 74 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Michael Gjedde Palmgren ◽  
Marianne Sommarin ◽  
Peter Ulvlskov ◽  
Peter Leth Jorgensen
Keyword(s):  
Fatty Acids ◽  
Plasma Membrane ◽  
Phospholipase A2 ◽  
Free Fatty Acids

scholarly journals Cytochemical evidence for the presence of phospholipids in epithelial tight junction strands.

1993 ◽  
Vol 41 (5) ◽  
pp. 649-656 ◽  
Author(s):  
F W Kan
Keyword(s):  
Plasma Membrane ◽  
Tight Junction ◽  
Phospholipase A2 ◽  
Plasma Membranes ◽  
Membrane Lipids ◽  
Freeze Fracture ◽  
Fracture Face ◽  
Gold Particles ◽  
Pancreatic Cells ◽  
Specific Association

Previous freeze-fracture experiments using either glutaraldehyde-fixed and cryoprotected specimens or unfixed rapid-frozen samples led to the proposal that cylindrical strands of the tight junction (TJ) observed in freeze-fracture preparations are inverted cylindrical micelles made up of membrane lipids and, possibly, membrane proteins. However, no one has yet been able to directly label the structural fibrils of the TJ. To test the hypothesis that TJ strands observed on freeze-fracture preparations are composed at least partially of lipids, we have combined the phospholipase A2-gold and the fracture-label techniques for localization of phospholipids. Phospholipase A2, purified from bee venom, was adsorbed on gold particles and used for specific labeling of its substrate. Phospholipase A2-colloidal gold (PLA2-CG) complex was applied to freeze-fractured preparations of rat exocrine pancreatic cells and testicular Sertoli cells, both of which are known to have extensive TJ complexes on their plasma membranes. Fracture-label replicas of exocrine pancreatic cells revealed specific association of gold particles with TJ fibrils on the protoplasmic fracture-face of the plasma membrane. The majority of these gold particles were observed either directly on the top of the TJ fibrils or adjacent to these cylindrical structures. A high density of PLA2-CG labeling was also observed over the complementary exoplasmic fracture-face of the TJ complex. This intimate association of PLA2-CG labeling with the TJ is particularly evident in the Sertoli cell plasma membrane, where rows of gold particles were observed to be superimposed on parallel arrays of cylindrical strands of the TJ complex. The present findings provide direct cytochemical evidence to support the hypothesis that cylindrical TJ strands observed in freeze-fracture preparations contain phospholipids.

Regulation of glycine transporters

2001 ◽  
Vol 29 (6) ◽  
pp. 742-745 ◽  
Author(s):  
B. López-Corcuera ◽  
C. Aragón ◽  
A. Geerlings
Keyword(s):  
Plasma Membrane ◽  
Protein Trafficking ◽  
Fluorescent Protein ◽  
Surface Expression ◽  
Immunogold Labelling ◽  
Glycine Release ◽  
Glycine Transporters ◽  
Protein Receptor ◽  
Large Dense Core Vesicles ◽  
Green Fluorescent

The regulation of neurotransmitter transporters is a central aspect of their physiology. Recent studies that focused on syntaxin-1 transporter interactions led to the postulation that syntaxin-1 is somehow implicated in protein trafficking. Because syntax – in-1 is involved in the exocytosis of neurotransmitters and it interacts with glycine transporter 2 (GLYT2), we stimulated exocytosis in synaptosomes and examined its effect on GLYT2 surface-expression and transport activity. We found that GLYT2 is rapidly trafficked first towards the plasma membrane and then internalized under conditions that stimulate vesicular glycine release. However, when syntaxin-1 was inactivated by pre-treatment of synaptosomes with the botulinum neurotoxin C, GLYT2 was unable to reach the plasma membrane but still was able to leave it. These results indicate the existence of a SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-mediated regulatory mechanism that controls the surface expression of GLYT2. Syntaxin-1 is involved in the transport of GLYT2 to, but not its retrieval from, the plasma membrane. Immunogold-labelling on purified vesicular preparations from synaptosomes showed that GLYT2 is present in small synaptic-like vesicles. This may represent neurotransmitter transporter that is being trafficked. The subcellular distribution of the glycine transporters was further examined in PC12 cells that were stably transfected with the fusions of GLYT1 and GLYT2 with green fluorescent protein. There was a clear difference in their intracellular distribution, GLYT1 being present mainly on the plasma membrane and GLYT2 being localized mainly on large, dense-core vesicles. We are trying to find signal sequences responsible for this differential localization.

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