scholarly journals Control of membrane fusion in exocytosis. Physiological studies on a Paramecium mutant blocked in the final step of the trichocyst extrusion process.

1980 ◽  
Vol 85 (2) ◽  
pp. 213-227 ◽  
Author(s):  
J Beisson ◽  
J Cohen ◽  
M Lefort-Tran ◽  
M Pouphile ◽  
M Rossignol
Keyword(s):  
Plasma Membrane ◽  
Membrane Fusion ◽  
Freeze Fracture ◽  
Acid Synthesis ◽  
Extrusion Process ◽  
Membrane Lipid ◽  
Effect Of Temperature ◽  
Physiological Studies ◽  
And Function ◽  
Induced Changes

Previous studies on exocytosis in Paramecium using mutants affecting trichocyst extrusion permitted us to analyze the assembly and function of three intramembrane particle arrays ("ring" and "rosette" in the plasma membrane, "annulus" in the trichocyst membrane) involved in the interaction between these two membranes. Using a conditional mutation, nd9, which blocks rosette assembly and prevents exocytosis at the nonpermissive temperature, we have analyzed the effect of temperature on the secretory capacity of nd9 cells. By combining several techniques (physiological studies, microinjections, inhibition of fatty acid synthesis, and freeze-fracture analysis) we demonstrate (a) that the product of the mutated allele nd9 is not thermolabile but that its activity is dependent upon temperature-induced changes in the membrane lipid composition and (b) that the product of the nd9 locus is a diffusible cytoplasmic component whose interaction with both plasma membrane and trichocyst membrane is required for rosette assembly and exocytosis. The data provide physiological evidence for the existence of a molecular complex(es) linking the two membranes and involved in the control of membrane fusion; we discuss the possible nature and function of these links.

scholarly journals Impact of Membrane Lipids on UapA and AzgA Transporter Subcellular Localization and Activity in Aspergillus nidulans

2021 ◽  
Vol 7 (7) ◽  
pp. 514
Author(s):  
Mariangela Dionysopoulou ◽  
George Diallinas
Keyword(s):  
Plasma Membrane ◽  
Subcellular Localization ◽  
Aspergillus Nidulans ◽  
Membrane Lipids ◽  
Membrane Lipid ◽  
Lipid Biosynthesis ◽  
Transport Kinetics ◽  
Negative Effect ◽  
And Function

Recent biochemical and biophysical evidence have established that membrane lipids, namely phospholipids, sphingolipids and sterols, are critical for the function of eukaryotic plasma membrane transporters. Here, we study the effect of selected membrane lipid biosynthesis mutations and of the ergosterol-related antifungal itraconazole on the subcellular localization, stability and transport kinetics of two well-studied purine transporters, UapA and AzgA, in Aspergillus nidulans. We show that genetic reduction in biosynthesis of ergosterol, sphingolipids or phosphoinositides arrest A. nidulans growth after germling formation, but solely blocks in early steps of ergosterol (Erg11) or sphingolipid (BasA) synthesis have a negative effect on plasma membrane (PM) localization and stability of transporters before growth arrest. Surprisingly, the fraction of UapA or AzgA that reaches the PM in lipid biosynthesis mutants is shown to conserve normal apparent transport kinetics. We further show that turnover of UapA, which is the transporter mostly sensitive to membrane lipid content modification, occurs during its trafficking and by enhanced endocytosis, and is partly dependent on autophagy and Hect-type HulARsp5 ubiquitination. Our results point out that the role of specific membrane lipids on transporter biogenesis and function in vivo is complex, combinatorial and transporter-dependent.

Membrane changes associated with mucus production by intestinal goblet cells

1978 ◽  
Vol 33 (1) ◽  
pp. 301-316
Author(s):  
J.G. Swift ◽  
T.M. Mukherjee
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Membrane Fusion ◽  
Thin Section ◽  
Structural Organization ◽  
Freeze Fracture ◽  
Goblet Cells ◽  
Mucus Production ◽  
Membrane Reorganization ◽  
Membrane Changes

Changes in the structural organization of membranes of mucous bodies and the plasma membrane that occur during mucus production in goblet cells of rat rectum have been studied by thin-section and freeze-fracture techniques. Immature mucous bodies are bounded by a trilaminar membrane and fracture faces of the membrane have randomly distributed intramembrane particles. During maturation, mucous bodies become packed tightly together and changes in the structure of their membranes include (1) fusion of apposing membranes of adjacent bodies to form a pentalaminar structure, (2) a reduction in the density of particles on membrane fracture faces, and (3) exclusion of particles from regions of membrane apposition. Some trilaminar membranes of mucous bodies fuse with the lumenal plasma membrane to form a pentalaminar structure. Sites of apposition between mucous body membranes and the lumenal plasma membrane are seen as particle-cleared bulges on fracture faces of the plasma membrane. Our results indicate that membrane reorganization associated with mucous production in goblet cells includes a reduction and redistribution of some membrane proteins and that membrane fusion occurs between portions of membranes from which proteins have been displaced.

scholarly journals Phagocytosis of bacteria by polymorphonuclear leukocytes: a freeze-fracture, scanning electron microscope, and thin-section investigation of membrane structure

1978 ◽  
Vol 76 (1) ◽  
pp. 158-174 ◽  
Author(s):  
PL Moore ◽  
HL Bank ◽  
NT Brissie ◽  
SS Spicer
Keyword(s):  
Plasma Membrane ◽  
Electron Microscope ◽  
Membrane Fusion ◽  
Thin Section ◽  
Membrane Structure ◽  
Freeze Fracture ◽  
Vacuole Membrane ◽  
Attachment Sites ◽  
Pmn Leukocytes ◽  
Scanning Electron

The changes in membrane structure of rabbit polymorphonuclear (PMN) leukocytes during bacterial phagocytosis was investigated with scanning electron microscope (SEM), thin-section, and freeze-fracture techniques. SEM observations of bacterial attachment sites showed the involvement of limited areas of PMN membrane surface (0.01-0.25μm(2)). Frequently, these areas of attachment were located on membrane extensions. The membrane extensions were present before, during, and after the engulfment of bacteria, but were diminished in size after bacterial engulfment. In general, the results obtained with SEM and thin-section techniques aided in the interpretation of the three-dimensional freeze-fracture replicas. Freeze-fracture results revealed the PMN leukocytes had two fracture faces as determined by the relative density of intramembranous particles (IMP). Membranous extensions of the plasma membrane, lysosomes, and phagocytic vacuoles contained IMP's with a distribution and density similar to those of the plasma membrane. During phagocytosis, IMPs within the plasma membrane did not undergo a massive aggregation. In fact, structural changes within the membranes were infrequent and localized to regions such as the attachment sites of bacteria, the fusion sites on the plasma membrane, and small scale changes in the phagocytic vacuole membrane during membrane fusion. During the formation of the phagocytic vacuole, the IMPs of the plasma membrane appeared to move in with the lipid bilayer while maintaining a distribution and density of IMPs similar to those of the plasma membranes. Occasionally, IMPs were aligned to linear arrays within phagocytic vacuole membranes. This alignment might be due to an interaction with linearly arranged motile structures on the side of the phagocytic vacuole membranes. IMP-free regions were observed after fusion of lysosomes with the phagocytic vacuoles or plasma membrane. These IMP-free areas probably represent sites where membrane fusion occurred between lysosomal membrane and phagocytic vacuole membrane or plasma membrane. Highly symmetrical patterns of IMPs were not observed during lysosomal membrane fusion.

scholarly journals Control of exocytotic processes: cytological and physiological studies of trichocyst mutants in Paramecium tetraurelia.

1981 ◽  
Vol 88 (2) ◽  
pp. 301-311 ◽  
Author(s):  
M Lefort-Tran ◽  
K Aufderheide ◽  
M Pouphile ◽  
M Rossignol ◽  
J Beisson
Keyword(s):  
Plasma Membrane ◽  
Freeze Fracture ◽  
Cell Interaction ◽  
Secretory Vesicle ◽  
Secretory Process ◽  
Cell Contact ◽  
Paramecium Tetraurelia ◽  
Cytoplasmic Factor ◽  
And Function ◽  
Cell Cell

The trichocysts of Paramecium tetraurelia constitute a favorable system for studying secretory process because of the numerous available mutations that block, at various stages, the development of these secretory vesicles, their migration towards and interaction with the cell surface, and their exocytosis. Previous studies of several mutants provided information (a) on the assembly and function of the intramembranous particles arrays in the plasma membrane at trichocyst attachment sites, (b) on the autonomous motility of trichocysts, required for attachment to the cortex, and (c) on a diffusible cytoplasmic factor whose interaction with both trichocyst and plasma membrane is required for exocytosis to take place. We describe here the properties of four more mutants deficient in exocytosis ability, nd6, nd7, tam38, and tam6, which were analyzed by freeze-fracture, microinjection of trichocysts, and assay for repair of the mutational defect through cell-cell interaction during conjugation with wild-type cells. As well as providing confirmation of previous conclusions, our observations show that the mutations nd6 and tam6 (which display striking abnormalities in their plasma membrane particle arrays and are reparable through cell-cell contact but not by microinjection of cytoplasm) affect two distinct properties of the plasma membrane, whereas the other two mutations affect different properties of the trichocysts. Altogether, the mutants so far analyzed now provide a rather comprehensive view of the steps and functions involved in secretory processes in Paramecium and demonstrate that two steps of these processes, trichocyst attachment to the plasma membrane and exocytosis, depend upon specific properties of both the secretory vesicle and the plasma membrane.

scholarly journals Gamma-ray-induced Changes in Plasma Membrane from Hypodermal Mesocarp Tissue of Muskmelon Fruit

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 823E-823
Author(s):  
Gene E. Lester ◽  
Bruce D. Whitaker
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Gamma Rays ◽  
Cucumis Melo ◽  
Gamma Ray ◽  
Total Protein Content ◽  
Protein Ratio ◽  
And Function ◽  
Induced Changes ◽  
Low Dosage

Postharvest gamma-irradiation of melons at low dosage has been reported to extend shelf life. This study assessed how irradiation alters the structure and function of plasma membrane (PM) from hypodermal-mesocarp tissue. Administration of gamma rays (1 kGy at 0.017 kGy/min) to mature melon (Cucumis melo L.) fruit caused a 14% drop in H+-ATPase activity within 4 h. Total protein content did not differ in PM from non-irradiated (NIR) vs. irradiated (IR) fruits. Following storage (7 days at 7C then 3 days at 21C), H+-ATPase activity was ≈10% to 20% lower in PM from both groups of fruit, with no difference between the two. Total PM protein had declined by 34% and 49% in IR and NIR fruits, respectively. After irradiation, the phospholipid to protein ratio (PL:protein) was substantially higher in PM from IR fruit (0.67 vs. 0.58 in NIR). With storage, PL:protein dropped to 0.52 in NIR fruit PM, but changed little (0.65) in IR fruit PM. These results may indicate that irradiation stimulates PL synthesis or inhibits PL catabolism. Further analyses of PM lipid content and composition are underway.

Particle Movement in Heliozoan Axopods Associated with Lateral Displacement of H ighly Ordered Membrane Domains

1976 ◽  
Vol 31 (3-4) ◽  
pp. 190-194 ◽  
Author(s):  
Christian F. Bardele
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Membrane Fusion ◽  
Lateral Displacement ◽  
Freeze Fracture ◽  
Motive Force ◽  
Membrane Domains ◽  
Particle Movement ◽  
Peripheral Membrane Proteins

Abstract Freeze-fracture studies reveal that extrusive organelles displaying saltatory particle movements in centrohelidian axopod are attached to highly ordered domains within the plasma membrane. It is postulated that the motive force for lateral displacement of these membrane domains with the adhering organelle is located immediately underneath the plasma membrane being either part of the peripheral membrane proteins or attached filaments alined parallel to the axopodial micro­ tubules. The attachment domain is interpreted organelle discharge by membrane fusion.

Cold-induced changes in bovine sperm plasma membrane: A freeze-fracture study

1988 ◽  
Vol 24 (4) ◽  
pp. 441
Author(s):  
F.E. De Leeuw ◽  
B. Colenbrander ◽  
A.J. Verkleij
Keyword(s):  
Plasma Membrane ◽  
Freeze Fracture ◽  
Bovine Sperm ◽  
Sperm Plasma Membrane ◽  
Fracture Study ◽  
Induced Changes

scholarly journals A freeze-fracture study of early membrane events during mast cell secretion.

1977 ◽  
Vol 73 (3) ◽  
pp. 660-671 ◽  
Author(s):  
S J Burwen ◽  
B H Satir
Keyword(s):  
Mast Cell ◽  
Plasma Membrane ◽  
Membrane Fusion ◽  
Ionic Composition ◽  
Freeze Fracture ◽  
Polymyxin B ◽  
Cell Secretion ◽  
Granule Membrane ◽  
Fracture Study ◽  
Freeze Fracture Electron Microscopy

The early membrane events taking place during mast cell secretion were followed in transmission and freeze-fracture electron microscopy. In order to slow down exocytosis and capture intermediate stages of membrane fusion, special conditions of incubation and stimulation were used. These were as follows: (a) the use of incubation media with altered ionic composition, and (b) stimulation with a low dosage of polymyxin B sulfate (4 microgram/ml) at low temperature (18 degrees C) for very short incubation times (30-60 s), with or without the presence of formaldehyde (0.8%). Under these conditions, unetchable circular impressions are found on the E face of the plasma membrane, 80-100 nm in diameter, with particles associated with their perimeters. In granule-to-granule fusion, the zone involved is demarcated by one or two rows of particles on the E face. In addition, raised circular areas of varying diameters (43-87 nm) surrounded by similar particles, also found on the E face, may represent potential sites before completion of fusion. Neither the circular impressions on the plasma membrane nor the sites on the granule membrane are permanent, but their appearance coincides with initiation of membrane fusion.

scholarly journals Membrane Lipid Composition: Effect on Membrane and Organelle Structure, Function and Compartmentalization and Therapeutic Avenues

2019 ◽  
Vol 20 (9) ◽  
pp. 2167 ◽  
Author(s):  
Doralicia Casares ◽  
Pablo V. Escribá ◽  
Catalina Ana Rosselló
Keyword(s):  
Plasma Membrane ◽  
Lipid Bilayers ◽  
Lipid Composition ◽  
Therapeutic Potential ◽  
Current Knowledge ◽  
Signal Propagation ◽  
Membrane Lipid ◽  
Membrane Lipid Composition ◽  
Cell Functions ◽  
And Function

Biological membranes are key elements for the maintenance of cell architecture and physiology. Beyond a pure barrier separating the inner space of the cell from the outer, the plasma membrane is a scaffold and player in cell-to-cell communication and the initiation of intracellular signals among other functions. Critical to this function is the plasma membrane compartmentalization in lipid microdomains that control the localization and productive interactions of proteins involved in cell signal propagation. In addition, cells are divided into compartments limited by other membranes whose integrity and homeostasis are finely controlled, and which determine the identity and function of the different organelles. Here, we review current knowledge on membrane lipid composition in the plasma membrane and endomembrane compartments, emphasizing its role in sustaining organelle structure and function. The correct composition and structure of cell membranes define key pathophysiological aspects of cells. Therefore, we explore the therapeutic potential of manipulating membrane lipid composition with approaches like membrane lipid therapy, aiming to normalize cell functions through the modification of membrane lipid bilayers.

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