scholarly journals Fluorescent, short-chain C6-NBD-sphingomyelin, but not C6-NBD-glucosylceramide, is subject to extensive degradation in the plasma membrane: implications for signal transduction related to cell differentiation

1995 ◽  
Vol 309 (3) ◽  
pp. 905-912 ◽  
Author(s):  
J W Kok ◽  
T Babia ◽  
K Klappe ◽  
D Hoekstra
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Cell Differentiation ◽  
Plasma Membranes ◽  
Cell Types ◽  
Short Chain ◽  
Synthetic Activity ◽  
Intact Cells ◽  
Ht29 Cells ◽  
Extensive Degradation

The involvement of the plasma membrane in the metabolism of the sphingolipids sphingomyelin (SM) and glucosylceramide (GlcCer) was studied, employing fluorescent short-chain analogues of these lipids, 6-[N-(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]hexanoylsphingosylphosphorylcholine (C6-NBD-SM), C6-NBD-GlcCer and their common biosynthetic precursor C6-NBD-ceramide (C6-NBD-Cer). Although these fluorescent short-chain analogues are metabolically active, some caution is to be taken in view of potential changes in biophysical/biochemical properties of the lipid compared with its natural counterpart. However, these short-chain analogues offer the advantage of studying the lipid metabolic enzymes in their natural environment, since detergent solubilization is not necessary for measuring their activity. These studies were carried out with several cell types, including two phenotypes (differing in state of differentiation) of HT29 cells. Degradation and biosynthesis of C6-NBD-SM and C6-NBD-GlcCer were determined in intact cells, in their isolated plasma membranes, and in plasma membranes isolated from rat liver tissue. C6-NBD-SM was found to be subject to extensive degradation in the plasma membrane, due to neutral sphingomyelinase (N-SMase) activity. The extent of C6-NBD-SM hydrolysis showed a general cell-type dependence and turned out to be dependent on the state of cell differentiation, as revealed for HT29 cells. In undifferentiated HT29 cells N-SMase activity was at least threefold higher than in its differentiated counterpart. In contrast, in all cell types studied, very little if any biosynthesis of C6-NBD-SM from the precursor C6-NBD-Cer occurred. Moreover, in the case of C6-NBD-GlcCer, neither hydrolytic nor synthetic activity was found to be associated with the plasma membrane. These results are discussed in the context of the involvement of the sphingolipids SM and GlcCer in signal transduction pathways in the plasma membrane.

scholarly journals Integrin-associated protein: a 50-kD plasma membrane antigen physically and functionally associated with integrins.

1990 ◽  
Vol 111 (6) ◽  
pp. 2785-2794 ◽  
Author(s):  
E Brown ◽  
L Hooper ◽  
T Ho ◽  
H Gresham
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Synthetic Peptides ◽  
Plasma Membranes ◽  
Protein A ◽  
Hematopoietic Cells ◽  
Cell Types ◽  
Cell Biol ◽  
Leukocyte Response ◽  
Stimulation Of

Phagocytosis by monocytes or neutrophils can be enhanced by interaction with several proteins or synthetic peptides containing the Arg-Gly-Asp sequence. Recently we showed that an mAb, B6H12, specifically inhibited this enhancement of neutrophil phagocytosis by inhibiting Arg-Gly-Asp binding to the leukocyte response integrin (Gresham, H. D., J. L. Goodwin, P. M. Allen, D. C. Anderson, and E. J. Brown. 1989. J. Cell Biol. 108:1935-1943). Now, we have purified the antigen recognized by B6H12 to homogeneity. Surprisingly, it is a 50-kD molecule that is expressed on the plasma membranes of all hematopoietic cells, including erythrocytes, which express no known integrins. On platelets and placenta, but not on erythrocytes, this protein is associated with an integrin that can be recognized by an anti-beta 3 antibody. In addition, both the anti-beta 3 and several mAbs recognizing the 50-kD protein inhibit Arg-Gly-Asp stimulation of phagocytosis. These data demonstrate an association between integrins and the 50-kD protein on several cell types. For this reason, we call it Integrin-associated Protein (IAP). We hypothesize that IAP may play a role in signal transduction for enhanced phagocytosis by Arg-Gly-Asp ligands.

Membrane microdomains: lessons from microscopy

1995 ◽  
Vol 53 ◽  
pp. 776-777
Author(s):  
J.M. Robinson ◽  
J.M Oliver
Keyword(s):  
Spatial Distribution ◽  
Plasma Membrane ◽  
Epithelial Cells ◽  
Plasma Membranes ◽  
Cell Types ◽  
Imaging Modalities ◽  
Membrane Microdomains ◽  
Membrane Domains ◽  
Lateral Heterogeneity ◽  
Functional Importance

Specialized regions of plasma membranes displaying lateral heterogeneity are the focus of this Symposium. Specialized membrane domains are known for certain cell types such as differentiated epithelial cells where lateral heterogeneity in lipids and proteins exists between the apical and basolateral portions of the plasma membrane. Lateral heterogeneity and the presence of microdomains in membranes that are uniform in appearance have been more difficult to establish. Nonetheless a number of studies have provided evidence for membrane microdomains and indicated a functional importance for these structures.This symposium will focus on the use of various imaging modalities and related approaches to define membrane microdomains in a number of cell types. The importance of existing as well as emerging imaging technologies for use in the elucidation of membrane microdomains will be highlighted. The organization of membrane microdomains in terms of dimensions and spatial distribution is of considerable interest and will be addressed in this Symposium.

Evidence for microtubule nucleation at plasma membrane-associated sites in Drosophila

1987 ◽  
Vol 88 (1) ◽  
pp. 95-107 ◽  
Author(s):  
M.M. Mogensen ◽  
J.B. Tucker
Keyword(s):  
Plasma Membrane ◽  
Cell Differentiation ◽  
Cross Section ◽  
Plasma Membranes ◽  
Early Stage ◽  
Apical Cell ◽  
Apical Plasma Membrane ◽  
Cell Surfaces ◽  
Microtubule Organizing Centres ◽  
Oriented Parallel

This report is concerned with the nucleation and organization of microtubule bundles that assemble after ‘conventional’ centrosomal microtubule-organizing centres have been lost. The microtubule bundles in question span the lengths of wing epidermal cells. Bundles extend between hemidesmosomes at the apical cuticle-secreting surfaces of cells and basal attachment desmosomes that unite the dorsal and ventral epidermal layers of developing wing blades. Furthermore, each bundle includes up to 1500 microtubules and most of the microtubules are composed of 15 protofilaments. Individual cells were serially cross-sectioned at an early stage of bundle assembly. The number of microtubule profiles/cell cross-section decreased progressively by up to 59% of the most apical values in section sequences cut from fairly apical to more basal levels in the cells. The apical ends of microtubules were associated with numerous small dense plaque-like sites (diameter 0.1-0.2 micron), which were specialized regions of plasma membranes at the apical surfaces of cells. Many of the microtubules near apical plaques were not well aligned with each other; they ‘radiated away’ from cell apices. This was in contrast to the situation at more basal levels where most microtubules were oriented parallel to the longitudinal axes of cells. These findings indicate that the relatively dispersed arrays of apical plasma membrane-associated plaques act as microtubule-nucleating sites to initiate basally directed elongation of bundle microtubules. Apical cell surfaces and their plaques seem to operate as microtubule-nucleating and -organizing regions that functionally replace the centrosomal microtubule-organizing centres lost earlier in cell differentiation.

Mechanisms of Hormone Action

2011 ◽  
Author(s):  
Stephen R. Hammes ◽  
Carole R. Mendelson
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Nuclear Receptors ◽  
Plasma Membranes ◽  
Hormone Receptors ◽  
Membrane Receptors ◽  
Endocrine Disorders ◽  
Messenger Rnas ◽  
Dihydroxyvitamin D3 ◽  
Transduction Mechanisms

The capacity of a cell to respond to a particular hormone depends on the presence of cellular receptors specific for that hormone. After binding hormone, the receptor is biochemically and structurally altered, resulting in its activation; the activated receptor then mediates all of the actions of the hormone on the cell. The steroid and thyroid hormones as well as retinoids and 1,25-dihydroxyvitamin D3 diffuse freely through the lipophilic plasma membrane of the cell and interact with receptors that are primarily within the nucleus. On activation, the receptors alter the transcription of specific genes, resulting in changes in the levels of specific messenger RNAs (mRNAs), which are in turn translated into proteins. Hormones that are water soluble, such as the peptide and polypeptide hormones, catecholamines, and other neurotransmitters, as well as the relatively hydrophobic prostaglandins, interact with receptors in the plasma membrane. After hormone binding, the activated membrane receptors initiate signal transduction cascades that result in changes in enzyme activities and alterations in gene expression. In this chapter, the properties of various classes of receptors that are localized within the plasma membranes of target cells and the signal transduction mechanisms that mediate interactions with their ligands will first be addressed. This will be followed by consideration of the structural properties of the nuclear hormone receptors, the events that result in their activation, and the mechanisms whereby the activated nuclear receptors alter the expression of specific genes. Finally, a number of endocrine disorders that are caused by alterations in the number and/or function of plasma membranes and nuclear receptors will be reviewed. The function of a receptor is to recognize a particular hormone among all the molecules in the environment of the cell at a given time and, after binding the hormone, to transmit a signal that ultimately results in a biological response. Hormones are normally present in the circulation in extremely low concentrations, ranging from 10 –9 to 10 –11 M.

scholarly journals Surface membrane vesicles from mononuclear cells stimulate erythroid stem cells to proliferate in culture

Blood ◽  
1982 ◽  
Vol 60 (3) ◽  
pp. 583-594 ◽  
Author(s):  
N Dainiak ◽  
CM Cohen
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Mononuclear Cells ◽  
Surface Membrane ◽  
Freeze Fracture ◽  
Membrane Vesicles ◽  
Cell Types ◽  
Target Cells ◽  
Freeze Fracture Electron Microscopy

Abstract In order to examine the contribution of cell surface materials to erythroid burst-promoting activity (BPA), we separated media conditioned by a variety of human cell types into pellets and supernatants by centrifugation. When added to serum-restricted cultures of nonadherent human marrow cells, pellets contained about half of the total stimulatory activity. Freeze-fracture electron microscopy of the pellets revealed the presence of unilamellar membrane vesicles ranging from 0.10 to 0.40 microM in diameter. The amount of BPA in culture increased with added vesicle concentration in a saturable fashion. Preparation of leukocyte conditioned medium (LCM) from 125I-wheat germ agglutinin labeled cells and studies comparing the glycoprotein composition of vesicles with that of leukocyte plasma membranes suggest that LCM-derived vesicles are of plasma membrane origin. Moreover, partially purified leukocyte plasma membrane preparations also contained BPA. While disruption of vesicles by freezing/thawing and hypotonic lysis did not alter BPA, heat, trypsin, or pronase treatment removed greater than 65% of BPA, implying that vesicle surface rather than intravesicular molecules express BPA. Results of BPA assays performed in two-layer clots indicated that proximity to target cells is required for vesicle BPA expression. We conclude that membrane vesicles spontaneously shed from cell surfaces may be important regulators of erythroid burst proliferation in vitro.

scholarly journals Paralemmin, a Prenyl-Palmitoyl–anchored Phosphoprotein Abundant in Neurons and Implicated in Plasma Membrane Dynamics and Cell Process Formation

1998 ◽  
Vol 143 (3) ◽  
pp. 795-813 ◽  
Author(s):  
Christian Kutzleb ◽  
Gabriele Sanders ◽  
Raina Yamamoto ◽  
Xiaolu Wang ◽  
Beate Lichte ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Species Conservation ◽  
Cell Types ◽  
Membrane Dynamics ◽  
Morphological Properties ◽  
Developmentally Regulated ◽  
Membrane Flow ◽  
Western Blots ◽  
Process Formation

We report the identification and initial characterization of paralemmin, a putative new morphoregulatory protein associated with the plasma membrane. Paralemmin is highly expressed in the brain but also less abundantly in many other tissues and cell types. cDNAs from chicken, human, and mouse predict acidic proteins of 42 kD that display a pattern of sequence cassettes with high inter-species conservation separated by poorly conserved linker sequences. Prenylation and palmitoylation of a COOH-terminal cluster of three cysteine residues confers hydrophobicity and membrane association to paralemmin. Paralemmin is also phosphorylated, and its mRNA is differentially spliced in a tissue-specific and developmentally regulated manner. Differential splicing, lipidation, and phosphorylation contribute to electrophoretic heterogeneity that results in an array of multiple bands on Western blots, most notably in brain. Paralemmin is associated with the cytoplasmic face of the plasma membranes of postsynaptic specializations, axonal and dendritic processes and perikarya, and also appears to be associated with an intracellular vesicle pool. It does not line the neuronal plasmalemma continuously but in clusters and patches. Its molecular and morphological properties are reminiscent of GAP-43, CAP-23, and MARCKS, proteins implicated in plasma membrane dynamics. Overexpression in several cell lines shows that paralemmin concentrates at sites of plasma membrane activity such as filopodia and microspikes, and induces cell expansion and process formation. The lipidation motif is essential for this morphogenic activity. We propose a function for paralemmin in the control of cell shape, e.g., through an involvement in membrane flow or in membrane–cytoskeleton interaction.

scholarly journals Membrane-associated phosphoproteins in Plasmodium berghei-infected murine erythrocytes.

1983 ◽  
Vol 97 (1) ◽  
pp. 196-201 ◽  
Author(s):  
M F Wiser ◽  
P A Wood ◽  
J W Eaton ◽  
J R Sheppard
Keyword(s):  
Plasma Membrane ◽  
Plasmodium Berghei ◽  
Plasma Membranes ◽  
Intact Cell ◽  
Erythrocyte Membranes ◽  
Amino Acid Residues ◽  
Two Dimensional Gel Electrophoresis ◽  
Intact Cells ◽  
Membrane Phosphorylation ◽  
Triton X

Normal and Plasmodium berghei (NYU-2 strain)-infected murine erythrocytes display substantially different patterns of plasma membrane phosphoproteins phosphorylation. Intact erythrocytes (normal and parasite infected) incubated with 32Pi and isolated washed erythrocyte plasma membranes incubated with gamma-32P-ATP were analyzed for phosphoproteins by SDS PAGE and autoradiography. Two new phosphoproteins of molecular weight 45,000 (pp45) and 68,000 (pp68), which are absent in normal erythrocyte membranes, are associated with the membranes of infected erythrocytes subjected to both intact-cell and isolated-membrane phosphorylation conditions. Two-dimensional gel electrophoresis indicates that pp45 and pp68 are of parasite origin. Partial or complete proteolytic digestion reveals that pp45 is phosphorylated at similar amino acid residues both in intact cells and in isolated membranes. The pp45 phosphoprotein can be detected at as low as 3% parasitemia and its phosphorylation is not affected by 10 microM cAMP, 1 mM Ca2+, or 5 mM EGTA. Extraction of isolated washed plasma membranes with 0.5% Triton X-100 or 0.1 M NaOH indicates that pp45 is detergent insoluble and only partially extractable with NaOH, suggesting that pp45 is closely associated with the host erythrocyte plasma membrane.

scholarly journals Modulation of 5′-nucleotidase activity in plasma membranes and intact cells by the extracellular matrix proteins laminin and fibronectin

1992 ◽  
Vol 282 (1) ◽  
pp. 181-188 ◽  
Author(s):  
N Olmo ◽  
J Turnay ◽  
G Risse ◽  
R Deutzmann ◽  
K von der Mark ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Plasma Membrane ◽  
Inhibitory Activity ◽  
Plasma Membranes ◽  
Extracellular Matrix Proteins ◽  
Cell Receptor ◽  
Inhibitory Effect ◽  
Matrix Proteins ◽  
Nucleotidase Activity ◽  
Intact Cells

Modulation of 5′-nucleotidase activity by the extracellular matrix proteins fibronectin, laminin and their fragments has been studied in plasma membrane preparations as well as in intact BCS-TC2 and Rugli cells. The ectoenzyme on plasma membranes is activated by laminin; fibronectin inhibits the AMPase activity on BCS-TC2 plasma membranes but no inhibitory effect is found in plasma membrane preparations from Rugli cells. These effects are dependent on the preincubation time and protein concentration. When the effect of the extracellular matrix proteins is studied on intact cells, both BCS-TC2 and Rugli cells show similar behaviour. A decrease in the enzyme activity is observed in the presence of fibronectin. The AMPase inhibitory activity is located on its 40 kDa fragment. No inhibitory activity is found in other fibronectin fragments, including the 140 kDa fragment which contains the RGDS cell-adhesion sequence. Laminin and its E1-4 and E8 fragments are able to activate the ecto-5′-nucleotidase activity of both BCS-TC2 and Rugli cells. The effect of the E1-4 fragment on intact cells is greater than that observed for the E8 fragment and uncleaved laminin. Our results suggest a bifunctional role for 5′-nucleotidase as ectoenzyme and cell receptor for extracellular matrix proteins.

scholarly journals Glycosynapses: microdomains controlling carbohydrate-dependent cell adhesion and signaling

2004 ◽  
Vol 76 (3) ◽  
pp. 553-572 ◽  
Author(s):  
Senitiroh Hakomori
Keyword(s):  
Signal Transduction ◽  
Cell Adhesion ◽  
Lipid Raft ◽  
Plasma Membranes ◽  
Cell Types ◽  
Src Family Kinases ◽  
Dependent Cell ◽  
Membrane Components ◽  
Type 3

The concept of microdomains in plasma membranes was developed over two decades, following observation of polarity of membrane based on clustering of specific membrane components. Microdomains involved in carbohydrate-dependent cell adhesion with concurrent signal transduction that affect cellular phenotype are termed "glycosynapse". Three types of glycosynapse have been distinguished: "type 1" having glycosphingolipid associated with signal transducers (small G-proteins, cSrc, Src family kinases) and proteolipids; "type 2" having O-linked mucin-type glycoprotein associated with Src family kinases; and "type 3" having N-linked integrin receptor complexed with tetraspanin and ganglioside. Different cell types are characterized by presence of specific types of glycosynapse or their combinations, whose adhesion induces signal transduction to either facilitate or inhibit signaling. E.g., signaling through type 3 glycosynapse inhibits cell motility and differentiation. Glycosynapses are distinct from classically-known microdomains termed "caveolae", "caveolar membrane", or more recently "lipid raft", which are not involved in carbohydrate-dependent cell adhesion. Type 1 and type 3 glycosynapses are resistant to cholesterol-binding reagents, whereas structure and function of "caveolar membrane" or "lipid raft" are disrupted by these reagents. Various data indicate a functional role of glycosynapses during differentiation, development, and oncogenic transformation.

Proton conductance of the plasma membrane: properties, regulation, and functional role

1993 ◽  
Vol 265 (1) ◽  
pp. C3-C14 ◽  
Author(s):  
G. L. Lukacs ◽  
A. Kapus ◽  
A. Nanda ◽  
R. Romanek ◽  
S. Grinstein
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Second Messengers ◽  
Cell Types ◽  
Membrane Properties ◽  
Transport Systems ◽  
Extracellular Acidification ◽  
Phagocyte Nadph Oxidase ◽  
Selective Permeability ◽  
Conductive Pathway

H+ conductive pathways have been detected in the plasma membranes of a variety of cell types. The large exquisitely H(+)-selective permeability of the conductive pathway can support sizable net H+ fluxes. Although subtle differences exist among tissues and species, certain common features suggest that related transport systems are involved in all cases. The H+ conductance is gated by depolarizing voltages and is promoted by intracellular acidification. Conversely, extracellular acidification inhibits the conductance. These features facilitate net H+ efflux, while precluding potentially deleterious H+ uptake. In some cell types, activation of the conductance is additionally controlled by physiological ligands and by second messengers. The conductance most likely functions in the regulation of intracellular pH, contributing to the extrusion of H+ during repetitive depolarization of the plasma membrane, as occurs in neurons and muscle cells. This pathway may be particularly relevant in the case of phagocytes. When stimulated, these cells undergo a sustained depolarization, while generating large amounts of metabolic acid. In addition, conductive H+ fluxes may also provide counterions to neutralize the activity of electrogenic enzymes, as suggested for the phagocyte NADPH oxidase.

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