Search results for "Coated vesicle"
showing 10 items of 26 documents
A Model for ERD2 Function in Higher Plants
2020
ER lumenal proteins have a K(H)DEL motif at their C-terminus. This is recognized by the ERD2 receptor (KDEL receptor in animals), which localizes to the Golgi apparatus and serves to capture escaped ER lumenal proteins. ERD2-ligand complexes are then transported back to the ER via COPI coated vesicles. The neutral pH of the ER causes the ligands to dissociate with the receptor being returned to the Golgi. According to this generally accepted scenario, ERD2 cycles between the ER and the Golgi, although it has been found to have a predominant Golgi localization. In this short article, we present a model for the functioning of ERD2 receptors in higher plants that explains why it is difficult t…
Hepatitis B Virus Exploits ERGIC-53 in Conjunction with COPII to Exit Cells.
2020
Several decades after its discovery, the hepatitis B virus (HBV) still displays one of the most successful pathogens in human populations worldwide. The identification and characterization of interactions between cellular and pathogenic components are essential for the development of antiviral treatments. Due to its small-sized genome, HBV highly depends on cellular functions to produce and export progeny particles. Deploying biochemical-silencing methods and molecular interaction studies in HBV-expressing liver cells, we herein identified the cellular ERGIC-53, a high-mannose-specific lectin, and distinct components of the endoplasmic reticulum (ER) export machinery COPII as crucial factor…
Shared midgut binding sites for Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac and Cry1Fa proteins from Bacillus thuringiensis in two important corn pests, Ostrin…
2013
First generation of insect-protected transgenic corn (Bt-corn) was based on the expression of Cry1Ab or Cry1Fa proteins. Currently, the trend is the combination of two or more genes expressing proteins that bind to different targets. In addition to broadening the spectrum of action, this strategy helps to delay the evolution of resistance in exposed insect populations. One of such examples is the combination of Cry1A.105 with Cry1Fa and Cry2Ab to control O. nubilalis and S. frugiperda. Cry1A.105 is a chimeric protein with domains I and II and the C-terminal half of the protein from Cry1Ac, and domain III almost identical to Cry1Fa. The aim of the present study was to determine whether the c…
Clathrin-mediated constitutive endocytosis of PIN auxin efflux carriers in Arabidopsis.
2007
SummaryEndocytosis is an essential process by which eukaryotic cells internalize exogenous material or regulate signaling at the cell surface [1]. Different endocytic pathways are well established in yeast and animals; prominent among them is clathrin-dependent endocytosis [2, 3]. In plants, endocytosis is poorly defined, and no molecular mechanism for cargo internalization has been demonstrated so far [4, 5], although the internalization of receptor-ligand complexes at the plant plasma membrane has recently been shown [6]. Here we demonstrate by means of a green-to-red photoconvertible fluorescent reporter, EosFP [7], the constitutive endocytosis of PIN auxin efflux carriers [8] and their …
Evidence for a selective and electroneutral K+/H+-exchange in Saccharomyces cerevisiae using plasma membrane vesicles
1996
The existence of a K+/H+ transport system in plasma membrane vesicles from Saccharomyces cerevisiae is demonstrated using fluorimetric monitoring of proton fluxes across vesicles (ACMA fluorescence quenching). Plasma membrane vesicles used for this study were obtained by a purification/reconstitution protocol based on differential and discontinuous sucrose gradient centrifugations followed by an octylglucoside dilution/gel filtration procedure. This method produces a high percentage of tightly-sealed inside-out plasma membrane vesicles. In these vesicles, the K+/H+ transport system, which is able to catalyse both K+ influx and efflux, is mainly driven by the K+ transmembrane gradient and ca…
Fabrication of polyelectrolyte multilayered vesicles as inhalable dry powder for lung administration of rifampicin
2014
A polyelectrolyte complex based on chitosan and carrageenan was used to coat rifampicin-loaded vesicles and obtain a dry powder for inhalation by spray-drying. The polymer complexation on vesicle surface stabilized them and improved their adhesion on airways and epithelia cells. Uncoated liposomes were small in size, negatively charged and able to incorporate large amounts of rifampicin (70%). Coated vesicles were still able to load adequate amounts of drug (∼70%) but the coating process produced larger particles (1 μm) that were positively charged and with a spherical shape. Aerosol performances, evaluated using the next-generation impactor, showed that coated vesicles reached the 50% of f…
Sorting signals in the cytosolic tail of plant p24 proteins involved in the interaction with the COPII coat.
2004
The ability of the cytosolic tail of a plant p24 protein to bind COPI and COPII subunits from plant and animal sources in vitro has been examined. We have found that a dihydrophobic motif in the -7,-8 position (relative to the cytosolic carboxy-terminus), which strongly cooperates with a dilysine motif in the -3,-4 position for COPI binding, is required for COPII binding. In addition, we show that COPI and COPII coat proteins from plant cytosol compete for binding to the sorting motifs in these tails. Only in the absence of the dilysine motif in the -3,-4 position or after COPI depletion could we observe COPII binding to the p24 tail. This competition is not observed when using rat liver cy…
ER-to-Golgi Transport: The COPII-Pathway
2006
The endoplasmic reticulum (ER) is the starting site of the journey of newly synthesized proteinsto the apoplast, plasma membrane and to the vacuolar compartments. Transport between these membranecompartments of the secretory pathway in eukaryotic cells is mediated by vesicles, which are producedby a budding mechanism involving coat proteins that capture specific cargo molecules and helppackage them into coated vesicles. These vesicles are known as COPII-coated vesicles, and are usuallyisolated after their induction in vitro using microsomal membranes, cytosol and a non-hydrolyzableGTP-analogue. COPII-coated vesicles are formed at specific sites in the ER known as ER-exit sites(ERES). ERES a…
Loss of endocytic clathrin-coated pits upon acute depletion of phosphatidylinositol 4,5-bisphosphate.
2007
Phosphatidylinositol 4,5-bisphosphate [PI(4,5) P 2 ], a phosphoinositide concentrated predominantly in the plasma membrane, binds endocytic clathrin adaptors, many of their accessory factors, and a variety of actin-regulatory proteins. Here we have used fluorescent fusion proteins and total internal reflection fluorescence microscopy to investigate the effect of acute PI(4,5) P 2 breakdown on the dynamics of endocytic clathrin-coated pit components and of the actin regulatory complex, Arp2/3. PI(4,5) P 2 breakdown was achieved by the inducible recruitment to the plasma membrane of an inositol 5-phosphatase module through the rapamycin/FRB/FKBP system or by treatment with ionomycin. PI(4,5)…
Hepatitis B subviral envelope particles use the COPII machinery for intracellular transport via selective exploitation of Sec24A and Sec23B
2020
Hepatitis B virus (HBV) is a leading cause of liver disease. Its success as a human pathogen is related to the immense production of subviral envelope particles (SVPs) contributing to viral persistence by interfering with immune functions. To explore cellular pathways involved in SVP formation and egress, we investigated host-pathogen interactions. Yeast-based proteomics revealed Sec24A, a component of the coat protein complex II (COPII), as an interaction partner of the HBV envelope S domain. To understand how HBV co-opts COPII as a proviral machinery, we studied roles of key Sec proteins in HBV-expressing liver cells. Silencing of Sar1, Sec23, and Sec24, which promote COPII assembly conco…