scholarly journals Manipulation of Host Vesicular Trafficking and Membrane Fusion During Chlamydia Infection

Chlamydia ◽  
10.5772/31244 ◽  
2012 ◽  
Author(s):  
Erik Ronzone ◽  
Jordan Wesolowski ◽  
Fabienne Paumet
Keyword(s):  
Membrane Fusion ◽  
Vesicular Trafficking ◽  
Chlamydia Infection

scholarly journals The AtC–VPS Protein Complex Is Localized to the Tonoplast and the Prevacuolar Compartment in Arabidopsis

2003 ◽  
Vol 14 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Enrique Rojo ◽  
Jan Zouhar ◽  
Valentina Kovaleva ◽  
Seho Hong ◽  
Natasha V. Raikhel
Keyword(s):  
Membrane Fusion ◽  
Plant Cells ◽  
Subcellular Fractionation ◽  
Vesicular Trafficking ◽  
Direct Role ◽  
Vacuole Formation ◽  
Plant Vacuole ◽  
Prevacuolar Compartment ◽  
Arabidopsis Mutant

Plant cells contain several types of vacuoles with specialized functions. Although the biogenesis of these organelles is well understood at the morphological level, the machinery involved in plant vacuole formation is largely unknown. We have recently identified an Arabidopsis mutant, vcl1, that is deficient in vacuolar formation. VCL1 is homologous to a protein that regulates membrane fusion at the tonoplast in yeast. On the basis of these observations, VCL1 is predicted to play a direct role in vacuolar biogenesis and vesicular trafficking to the vacuole in plants. In this work, we show that VCL1 forms a complex with AtVPS11 and AtVPS33 in vivo. These two proteins are homologues of proteins that have a well-characterized role in membrane fusion at the tonoplast in yeast. VCL1, AtVPS11, and AtVPS33 are membrane-associated and cofractionate with tonoplast and denser endomembrane markers in subcellular fractionation experiments. Consistent with this, VCL1, AtVPS11, and AtVPS33 are found on the tonoplast and the prevacuolar compartment (PVC) by immunoelectron microscopy. We also show that a VCL1-containing complex includes SYP2-type syntaxins and is most likely involved in membrane fusion on both the PVC and tonoplast in vivo. VCL1, AtVPS11, and AtVPS33 are the first components of the vacuolar biogenesis machinery to be identified in plants.

Dysfunction of Golgi tethers, SNAREs, and SNAPs in monocrotaline-induced pulmonary hypertension

2007 ◽  
Vol 292 (6) ◽  
pp. L1526-L1542 ◽  
Author(s):  
Pravin B. Sehgal ◽  
Somshuvra Mukhopadhyay ◽  
Fang Xu ◽  
Kirit Patel ◽  
Mehul Shah
Keyword(s):  
Cell Culture ◽  
Pulmonary Hypertension ◽  
Membrane Fusion ◽  
Vesicular Trafficking ◽  
Lung Epithelial Cells ◽  
Cell Fractionation ◽  
Golgi Membranes ◽  
Protein Receptors ◽  
Attachment Proteins ◽  
Endothelial Nitric Oxide

Monocrotaline (MCT)-induced pulmonary hypertension (PH) in the rat is a widely used experimental model. We have previously shown that MCT pyrrole (MCTP) produces loss of caveolin-1 (cav-1) and endothelial nitric oxide synthase from plasma membrane raft microdomains in pulmonary arterial endothelial cells (PAEC) with the trapping of these proteins in the Golgi organelle (the Golgi blockade hypothesis). In the present study, we investigated the mechanisms underlying this intracellular trafficking block in experiments in cell culture and in the MCT-treated rat. In cell culture, PAEC showed trapping of cav-1 in Golgi membranes as early as 6 h after exposure to MCTP. Phenotypic megalocytosis and a reduction in anterograde trafficking (assayed in terms of the secretion of horseradish peroxidase derived from exogenously transfected expression constructs) were evident within 12 h after MCTP. Cell fractionation and immunofluorescence techniques revealed the marked accumulation of diverse Golgi tethers, soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptors (SNAREs), and soluble NSF attachment proteins (SNAPs), which mediate membrane fusion during vesicular trafficking (GM130, p115, giantin, golgin 84, clathrin heavy chain, syntaxin-4, -6, Vti1a, Vti1b, GS15, GS27, GS28, SNAP23, and α-SNAP) in the enlarged/circumnuclear Golgi in MCTP-treated PAEC and A549 lung epithelial cells. Moreover, NSF, an ATPase required for the “disassembly” of SNARE complexes subsequent to membrane fusion, was increasingly sequestered in non-Golgi membranes. Immunofluorescence studies of lung tissue from MCT-treated rats confirmed enlargement of perinuclear Golgi elements in lung arterial endothelial and parenchymal cells as early as 4 days after MCT. Thus MCT-induced PH represents a disease state characterized by dysfunction of Golgi tethers, SNAREs, and SNAPs and of intracellular vesicular trafficking.

Trophoblast Cell Membrane Interactions at Implantation

1970 ◽  
Vol 28 ◽  
pp. 310-311
Author(s):  
A. C. Enders
Keyword(s):  
Epithelial Cells ◽  
Cell Membrane ◽  
Membrane Fusion ◽  
Trophoblast Cell ◽  
Membrane Interactions ◽  
Uterine Epithelial Cells ◽  
Functional Complex ◽  
Cytotrophoblast Cells ◽  
Complex Relationships ◽  
Syncytial Trophoblast

The alteration in membrane relationships seen at implantation include 1) interaction between cytotrophoblast cells to form syncytial trophoblast and addition to the syncytium by subsequent fusion of cytotrophoblast cells, 2) formation of a wide variety of functional complex relationships by trophoblast with uterine epithelial cells in the process of invasion of the endometrium, and 3) in the case of the rabbit, fusion of some uterine epithelial cells with the trophoblast.Formation of syncytium is apparently a membrane fusion phenomenon in which rapid confluence of cytoplasm often results in isolation of residual membrane within masses of syncytial trophoblast. Often the last areas of membrane to disappear are those including a desmosome where the cell membranes are apparently held apart from fusion.

Lipid Polymorphism and Virus-Membrane Fusion as Observed in Vitrified Thin Films by Cryo-Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 492-493
Author(s):  
P.M. Frederik ◽  
K.N.J. Burger ◽  
M.C.A. Stuart ◽  
A.J. Verkleij
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Membrane Fusion ◽  
Film Formation ◽  
Molar Ratio ◽  
Influenza B ◽  
Complex Structures ◽  
Type Ii ◽  
Suspended Material ◽  
Cryo Electron Microscopy

Cellular membranes are often composed of phospholipid mixtures in which one or more components have a tendency to adopt a type II non-bilayer lipid structure such as the inverted hexagonal (H||) phase. The formation of a type II non-bilayer intermediate, the inverted lipid micel is proposed as the initial step in membrane fusion (Verkleij 1984, Siegel, 1986). In the various forms of cellular transport mediated by carrier vesicles (e.g. exocytosis, endocytosis) the regulation of membrane fusion, and hence of inverted lipid micel formation, is of vital importance.We studied the phase behaviour of simple and complex lipid mixtures by cryo-electron microscopy to gain more insight in the ultrastructure of different lipid phases (e.g. Pβ’, Lα, H||) and in the complex membrane structures arising after Lα < - > H|| phase changes (e.g. isotropic, cubic). To prepare hydrated thin films a 700 mesh hexagonal grid (without supporting film) was dipped into and withdrawn from a liposome suspension. The excess fluid was blotted against filter paper and the thin films that form between the bars of the specimen grid were immediately (within 1 second) vitrified by plunging of the carrier grids into ethane cooled to its melting point by liquid nitrogen (Dubochet et al., 1982). Surface active molecules such as phospholipids play an important role in the formation and thinning of these aqueous thin films (Frederik et al., 1989). The formation of two interfacial layers at the air-water interfaces requires transport of surface molecules from the suspension as well as the orientation of these molecules at the interfaces. During the spontaneous thinning of the film the interfaces approach each other, initially driven by capillary forces later by Van der Waals attraction. The process of thinning results in the sorting by size of the suspended material and is also accompanied by a loss of water from the thinner parts of the film. This loss of water may result in the concentration and eventually in partial dehydration of suspended material even if thin films are vitrified within 1 sec after their formation. Film formation and vitrification were initiated at temperatures between 20-60°C by placing die equipment in an incubator provided widi port holes for the necessary manipulations. Unilamellar vesicles were made from dipalmitoyl phosphatidyl choline (DPPC) by an extrusion method and showed a smooth (Lα) or a rippled (PB’.) structure depending on the temperature of the suspensions and the temperature of film formation (50°C resp. 39°C) prior to vitrification. The thermotropic phases of hydrated phospholipids are thus faithfully preserved in vitrified thin films (fig. a,b). Complex structures arose when mixtures of dioleoylphosphatidylethanol-amine (DOPE), dioleoylphosphatidylcholine (DOPC) and cholesterol (molar ratio 3/1/2) are heated and used for thin film formation. The tendency of DOPE to adopt the H|| phase is responsible for the formation of complex structures in this lipid mixture. Isotropic and cubic areas (fig. c,d) having a bilayer structure are found in coexistence with H|| cylinders (fig. e). The formation of interlamellar attachments (ILA’s) as observed in isotropic and cubic structures is also thought to be of importance in biological fusion events. Therefore the study of the fusion activity of influenza B virus with liposomes (DOPE/DOPC/cholesterol/ganglioside in a molar ratio 1/1/2/0.2) was initiated. At neutral pH only adsorption of virus to liposomes was observed whereas 2 minutes after a drop in pH (7.4 - > 5.4) fusion between virus and liposome membranes was demonstrated (fig. f). The micrographs illustrate the exciting potential of cryo-electron microscopy to study lipid-lipid and lipid-protein interactions in hydrated specimens.

Sign in / Sign up

Export Citation Format

Share Document