scholarly journals Direct labelling of hormone-sensitive phosphoinositides by a plasma-membrane-associated PtdIns synthase in turkey erythrocytes

1993 ◽  
Vol 294 (3) ◽  
pp. 793-799 ◽  
Author(s):  
C Vaziri ◽  
C P Downes ◽  
S C Macfarlane
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Enzyme Activities ◽  
Plasma Membranes ◽  
Purinergic Receptor ◽  
Specific Radioactivity ◽  
Direct Access ◽  
Inositol Phospholipids ◽  
Direct Labelling ◽  
Hormone Sensitive

We have previously characterized phosphatidylinositol (PtdIns) synthase and PtdIns/myo-inositol-exchange enzyme activities in ghost membranes prepared by hypotonic lysis of turkey erythrocytes [McPhee, Lowe, Vaziri and Downes (1991) Biochem. J. 275, 187-192]. Here we show that PtdIns synthase activity is relatively enriched in plasma-membrane preparations of turkey erythrocytes and that inositol phospholipids labelled by both PtdIns synthase and PtdIns myo-inositol exchange enzymes are susceptible to hydrolysis by the receptor- and G-protein-regulated phospholipase C (PLC), which is present also in ghost preparations. Specific-radioactivity measurements of [3H]PtdIns from ghosts labelled to equilibrium under conditions favouring [3H]inositol incorporation by PtdIns synthase activity indicate that PtdIns synthase can directly access approx. 14% of the total erythrocyte ghost PtdIns. Approx. 16% of the [3H]PtdIns labelled by the PtdIns synthase reaction can be phosphorylated to polyphosphoinositides, which are then hydrolysed by the receptor- and G-protein-stimulated PLC. Since the mass of PtdIns declines to a similar extent as [3H]PtdIns during stimulation in the presence of guanine nucleotides and ATP, it is evident that both the labelled and unlabelled phosphoinositides are susceptible to hydrolysis by the relevant PLC. Phosphoinositides present in nuclei-free plasma membranes were also labelled by [3H]inositol under conditions favouring PtdIns synthase and PtdIns/myo-inositol-exchange enzyme activities respectively. These membranes lack PLC activity [Vaziri and Downes (1992) J. Biol. Chem. 267, 22973-22981], but the labelled lipids were sensitive to purinergic-receptor-stimulated hydrolysis in reconstitution assays using partially purified turkey erythrocyte PLC. The results strongly suggest that at least a portion of the PtdIns synthase in turkey erythrocytes is located in the plasma membrane and has direct access to an agonist-sensitive pool of inositol phospholipids.

scholarly journals Pseudotypes of Vesicular Stomatitis Virus with CD4 Formed by Clustering of Membrane Microdomains during Budding

2005 ◽  
Vol 79 (11) ◽  
pp. 7077-7086 ◽  
Author(s):  
Erica L. Brown ◽  
Douglas S. Lyles
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Lipid Rafts ◽  
Immunoelectron Microscopy ◽  
Vesicular Stomatitis Virus ◽  
Plasma Membranes ◽  
Membrane Microdomains ◽  
Virus Budding ◽  
Vesicular Stomatitis ◽  
Membrane Components

ABSTRACT Many plasma membrane components are organized into detergent-resistant membrane microdomains referred to as lipid rafts. However, there is much less information about the organization of membrane components into microdomains outside of lipid rafts. Furthermore, there are few approaches to determine whether different membrane components are colocalized in microdomains as small as lipid rafts. We have previously described a new method of determining the extent of organization of proteins into membrane microdomains by analyzing the distribution of pairwise distances between immunogold particles in immunoelectron micrographs. We used this method to analyze the microdomains involved in the incorporation of the T-cell antigen CD4 into the envelope of vesicular stomatitis virus (VSV). In cells infected with a recombinant virus that expresses CD4 from the viral genome, both CD4 and the VSV envelope glycoprotein (G protein) were found in detergent-soluble (nonraft) membrane fractions. However, analysis of the distribution of CD4 and G protein in plasma membranes by immunoelectron microscopy showed that both were organized into membrane microdomains of similar sizes, approximately 100 to 150 nm. In regions of plasma membrane outside of virus budding sites, CD4 and G protein were present in separate membrane microdomains, as shown by double-label immunoelectron microscopy data. However, virus budding occurred from membrane microdomains that contained both G protein and CD4, and extended to approximately 300 nm, indicating that VSV pseudotype formation with CD4 occurs by clustering of G protein- and CD4-containing microdomains.

Processing of receptor-bound somatostatin: internalization and degradation by pancreatic acini

1987 ◽  
Vol 252 (4) ◽  
pp. G535-G542 ◽  
Author(s):  
N. Viguerie ◽  
J. P. Esteve ◽  
C. Susini ◽  
N. Vaysse ◽  
A. Ribet
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Specific Radioactivity ◽  
Pancreatic Acinar Cells ◽  
Nuclear Fraction ◽  
Pancreatic Acini ◽  
Specific Binding Sites ◽  
Membrane Bound ◽  
Membrane Level

We have previously demonstrated the presence of specific binding sites for somatostatin on plasma membranes from pancreatic acinar cells. In the present study we attempted to characterize the fate of receptor-bound 125I-[Tyr11]somatostatin. Internalization of somatostatin was rapid (reaching a plateau at 20% of the cell-associated specific radioactivity) and temperature dependent. To follow the processing of bound somatostatin, acini were incubated with 125I-[Tyr11]somatostatin at 5 degrees C during 16 h then, after washing, incubated at 37 degrees C for 90 min in fresh medium. Surface-bound somatostatin decreased rapidly, whereas radioactivity increased in the cell interior and the incubation medium. Intracellular and membrane-bound radioactivity was mainly intact 125I-[Tyr11]somatostatin. Degradation occurred at the plasma membrane level and led to iodotyrosine production. After 15 min of incubation, 15% of the initially surface-bound 125I-[Tyr11]somatostatin was compartmentalized within the cell, mainly in the microsomal fraction. After 30 min, a significant increase in radioactivity appeared in the nuclear fraction. These results indicate that the major part of somatostatin cellular degradation takes place at the plasma membrane level. Within the cell, somatostatin is routed to the nucleus via particular fractions sedimenting with microsomal vesicles.

Incorporation in vivo of [32P]orthophosphate and [Me-3H]choline into rough microsomal, Golgi, and plasma membranes of rat liver

1977 ◽  
Vol 55 (8) ◽  
pp. 876-885 ◽  
Author(s):  
Patricia L. Chang ◽  
John R. Riordan ◽  
Mario A. Moscarello ◽  
Jennifer M. Sturgess
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Specific Radioactivity ◽  
Marker Enzyme ◽  
Golgi Membranes ◽  
Endomembrane Flow

To study membrane biogenesis and to test the validity of the endomembrane flow hypothesis, incorporation of 32P and [Me-3H]choline in vivo into membranes of the rat liver was followed. Rough microsomal, Golgi-rich, and plasma membrane fractions were monitored with marker enzyme assays and shown with morphometric analysis to contain 82% rough microsomes, at least 70% Golgi complexes, and 88% plasma membranes, respectively. Membrane subfractions from the rough microsomal and Golgi-rich fractions were prepared by sonic disruption.At 5 to 30 min after 32P injection, the specific radioactivity of phosphatidylcholine was higher in the rough microsomal membranes than in the Golgi membranes. From 1 to 3 h, the specific activity of phosphatidylcholine in Golgi membranes became higher and reached the maximum at about 3 h. Although the plasma membrane had the lowest specific radioactivity throughout 0.25–3 h, it increased rapidly thereafter to attain the highest specific activity at 5 h. Both rough microsomal and plasma membranes reached their maxima at 5 h.The specific radioactivity of [32P]phosphatidylethanolamine in the three membrane fractions was similar to that of [32P]phosphatidylcholine except from 5 to 30 min, when the specific radioactivity of phosphatidylethanolamine in the Golgi membranes was similar to the rough microsomal membranes.At 15 min to 5 h after [Me-3H]choline injection, more than 90% of the radioactivity in all the membranes was acid-precipitable. The specific radioactivities of the acid-precipitated membranes, expressed as dpm per milligram protein, reached the maximum at 3 h. After [Me-3H]choline injection, the specific radioactivity of phosphatidylcholine separated from the lipid extract of the acid-precipitated membranes (dpm per micromole phosphorus) did not differ significantly in the three membrane fractions. The results indicated rapid incorporation of choline into membrane phosphatidylcholine by the rough endoplasmic reticulum, Golgi, and plasma membranes simultaneously.The data with both 32P and [Me-3H]choline precursors did not support the endomembrane flow hypothesis. The Golgi complexes apparently synthesized phosphatidylethanolamine and incorporated choline into phosphatidylcholine as well as the endoplasmic reticulum. The results are discussed with relevance to current hypotheses on the biogenesis and transfer of membrane phospholipids.

scholarly journals Organization of G Proteins and Adenylyl Cyclase at the Plasma Membrane

1997 ◽  
Vol 8 (12) ◽  
pp. 2365-2378 ◽  
Author(s):  
Chunfa Huang ◽  
John R. Hepler ◽  
Linda T. Chen ◽  
Alfred G. Gilman ◽  
Richard G.W. Anderson ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Adenylyl Cyclase ◽  
G Protein ◽  
Buoyant Density ◽  
Cyclase Activity ◽  
Immunogold Electron Microscopy ◽  
Adenylyl Cyclase Activity ◽  
A Cell ◽  
Hormone Sensitive ◽  
Punctate Pattern

There is mounting evidence for the organization and compartmentation of signaling molecules at the plasma membrane. We find that hormone-sensitive adenylyl cyclase activity is enriched in a subset of regulatory G protein-containing fractions of the plasma membrane. These subfractions resemble, in low buoyant density, structures of the plasma membrane termed caveolae. Immunofluorescence experiments revealed a punctate pattern of G protein α and β subunits, consistent with concentration of these proteins at distinct sites on the plasma membrane. Partial coincidence of localization of G protein α subunits with caveolin (a marker for caveolae) was observed by double immunofluorescence. Results of immunogold electron microscopy suggest that some G protein is associated with invaginated caveolae, but most of the protein resides in irregular structures of the plasma membrane that could not be identified morphologically. Because regulated adenylyl cyclase activity is present in low-density subfractions of plasma membrane from a cell type (S49 lymphoma) that does not express caveolin, this protein is not required for organization of the adenylyl cyclase system. The data suggest that hormone-sensitive adenylyl cyclase systems are localized in a specialized subdomain of the plasma membrane that may optimize the efficiency and fidelity of signal transduction.

scholarly journals Multiple metabolic pools of phosphoinositides and phosphatidate in human erythrocytes incubated in a medium that permits rapid transmembrane exchange of phosphate

1987 ◽  
Vol 244 (1) ◽  
pp. 209-217 ◽  
Author(s):  
C E King ◽  
L R Stephens ◽  
P T Hawkins ◽  
G R Guy ◽  
R H Michell
Keyword(s):  
Plasma Membrane ◽  
Human Erythrocyte ◽  
Plasma Membranes ◽  
Age Distribution ◽  
Specific Radioactivity ◽  
Human Erythrocytes ◽  
Metabolic Compartmentation ◽  
To Come ◽  
Metabolic Heterogeneity

1. A Hepes-based medium has been devised which allows rapid Pi exchange across the plasma membrane of the human erythrocyte. This allows the metabolically labile phosphate pools of human erythrocytes to come to equilibrium with [32P]Pi in the medium after only 5 h in vitro. 2. After 5-7 h incubation with [32P]Pi in this medium, only three phospholipids, phosphatidic acid (PtdOH), phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P2) are radioactively labelled. The concentrations of PtdIns4P and PtdIns4,5P2 remain constant throughout the incubation, so this labelling process is a reflection of the steady-state turnover of their monoester phosphate groups. 3. During such incubations, the specific radioactivities of the monoesterified phosphates of PtdIns4, PtdIns4,5P2 and PtdOH come to a steady value after 5 h that is only 25-30% of the specific radioactivity of the gamma-phosphate of ATP at that time. We suggest that this is a consequence of metabolic heterogeneity. This heterogeneity is not a result of the heterogeneous age distribution of the erythrocytes in human blood. Thus it appears that there is metabolic compartmentation of these lipids within cells, such that within a time-scale of a few hours only 25-30% of these three lipids are actively metabolized. 4. The phosphoinositidase C of intact human erythrocytes, when activated by Ca2+-ionophore treatment, only hydrolyses 50% of the total PtdIns4,5P2 and 50% of 32P-labelled PtdIns4,5P2 present in the cells: this enzyme does not discriminate between the metabolically active and inactive compartments of lipids in the erythrocyte membrane. Hence at least four metabolic pools of PtdIns4P and PtdIns4,5P2 are distinguishable in the human erythrocyte plasma membrane. 5. The mechanisms by which multiple non-mixing metabolic pools of PtdOH, PtdIns4P and PtdIns4,5P2 are sustained over many hours in the plasma membranes of intact erythrocytes are unknown, although some possible explanations are considered.

scholarly journals Characterization of the membrane proteins of rat liver lysosomes. Composition, enzyme activities and turnover

1982 ◽  
Vol 204 (2) ◽  
pp. 525-534 ◽  
Author(s):  
J Burnside ◽  
D L Schneider
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Atpase Activity ◽  
Enzyme Activities ◽  
Plasma Membranes ◽  
Lysosomal Membrane ◽  
Pulse Labelling ◽  
Polypeptide Composition ◽  
Lysosomal Membranes ◽  
Triton Wr 1339

Lysosomes prepared from the livers of untreated rats and from the livers of rats injected with either Triton WR-1339 or dextran yielded membranes that were similar in both polypeptide composition and activities of ATPase and acid 5'-nucleotidase. The administration of Triton WR-1339 (and dextran) resulted in an increase in ATPase activity of liver homogenates that was associated with a parallel increase in the ATPase activity of the lysosomal membrane. On the other hand, plasma membranes appear to be different from lysosomal membranes with respect to polypeptide composition and enzyme activities. The ATPase activity of lysosomal membranes is not affected by ouabain and suramin, inhibitors of the plasma-membrane ATPase. The plasma-membrane alkaline 5'-nucleotidase has little activity at acid pH. Pulse-labelling of lysosomal membranes with [3H]fucose and with [3H]- and [14C]-leucine occurred rapidly, faster than labelling of plasma membranes. The labelling kinetics indicate that lysosomal membranes may be assembled independently of plasma membranes. These data suggest that, in liver, little bulk transport of plasma membrane to lysosomes takes place, and lysosomal-membrane proteins may not be derived from those of plasma membranes.

Agonist-induced translocation of Gq/11α immunoreactivity directly from plasma membrane in MDCK cells

1999 ◽  
Vol 276 (4) ◽  
pp. F528-F534
Author(s):  
John M. Arthur ◽  
Georgiann P. Collinsworth ◽  
Thomas W. Gettys ◽  
John R. Raymond
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Plasma Membranes ◽  
Protein Translocation ◽  
Mdck Cells ◽  
Regulatory Protein ◽  
Intact Cells ◽  
Intracellular Location ◽  
Signaling Specificity ◽  
Guanine Nucleotide Binding

Both Gsα and Gqα are palmitoylated and both can move from a crude membrane fraction to a soluble fraction in response to stimulation with agonists. This response may be mediated through depalmitoylation. Previous studies have not demonstrated that endogenous guanine nucleotide-binding regulatory protein (G protein) α-subunits are released directly from the plasma membrane. We have examined the effect of agonist stimulation on the location of Gq/11α immunoreactivity in Madin-Darby canine kidney (MDCK) cells. Bradykinin (BK; 0.1 μM) caused Gq/11α, but not Giα, to rapidly translocate from purified plasma membranes to the supernatant. AlF and GTP also caused translocation of Gq/11α immunoreactivity from purified plasma membranes. BK caused translocation of Gq/11α immunoreactivity in intact cells from the basal and lateral plasma membranes to an intracellular compartment as assessed by confocal microscopy. Thus Gq/11α is released directly from the plasma membrane to an intracellular location in response to activation by an agonist and direct activation of G proteins. G protein translocation may be a mechanism for desensitization or for signaling specificity.

Synthesis and Turnover of Membrane Proteins in Rat Liver: An Examination of the Membrane Flow Hypothesis

1971 ◽  
Vol 26 (10) ◽  
pp. 1031-1039 ◽  
Author(s):  
Werner W. Franke ◽  
D. James Morre ◽  
Barbara Deumling ◽  
Ronald D. Cheetham ◽  
Jürgen Kartenbeck ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Golgi Apparatus ◽  
Plasma Membranes ◽  
Degradation Kinetics ◽  
Specific Radioactivity ◽  
Membrane Flow ◽  
Rapid Turnover ◽  
Associated Proteins

The kinetics of synthesis and degradation of the protein constituents of nuclear membranes, endoplasmic reticulum membranes (rough-surfaced microsomes), Golgi apparatus membranes and plasma membranes were determined following a single administration of L- [guanido-14C] arginine by intraperitoneal injection. Membrane protein was determined as the fraction which resists sonication and sequential extrations with 1.5 M KCl, 0.1% deoxycholate and water to remove intravesicular, intracisternal (secretory), nucleo-, adsorbed and ribosome-associated proteins.The order of maximum labeling of membrane proteins was a) endoplasmic reticulum (nuclear membrane), b) Golgi apparatus, and c) plasma membrane. Rapid decreases in specific radioactivity followed maximal labeling of endoplasmic reticulum and Golgi apparatus membranes. These rapid turnover components of endoplasmic reticulum and Golgi apparatus were sufficient to account for labeling of plasma membranes via a flow mechanism.Incorporation of radioactivity into plasma membranes showed two distinct phases. The ultrastructural features underlying the biphasic pattern of incorporation into plasma membranes are discussed.Following initial incorporation and rapid turnover, membrane proteins were characterized by degradation kinetics approximating 1st order. Rates of degradation for Golgi apparatus and plasma membranes were faster than those for nuclear envelope and endoplasmic reticulum membranes.Assuming steady state conditions, an absolute synthetic rate of 7.1 mpg/min/avergage hepatocyte was calculated for membrane proteins of the plasma membrane.The results are compatible with intracellular movement and conversion of rough endoplasmic reticulum to plasma membrane via the membranes of the Golgi apparatus, i. e., membrane flow. Additionally, the kinetics indicate that membrane synthesis and transfer is restricted to specific parts of the endoplasmic reticulum and Golgi apparatus.

scholarly journals Isolation of plasma membrane from protoplasts of Lolium multiflorum (ryegrass) endosperm cells

1982 ◽  
Vol 205 (3) ◽  
pp. 511-519 ◽  
Author(s):  
A Schibeci ◽  
G B Fincher ◽  
B A Stone ◽  
A B Wardrop
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Membrane Fraction ◽  
Plasma Membranes ◽  
Lolium Multiflorum ◽  
Immunoglobulin A ◽  
Specific Radioactivity ◽  
Centrifugal Forces ◽  
Myeloma Protein ◽  
Plasma Membrane Fraction

Plasma membranes have been isolated from protoplasts of suspension-cultured ryegrass (Lolium multiflorum) endosperm cells. The protoplast membrane is coated before cell disruption with murine myeloma protein J539, a galactose-binding immunoglobulin A. The plasma membrane is labelled with 125I by using chemically or enzymically catalysed iodination techniques, or, more conveniently, by using 125I-labelled myeloma protein J539, which enables the membrane to be simultaneously coated and labelled. Protoplast lysis is effected by gentle mechanical means after swelling in hypo-osmotic medium. The plasma-membrane fraction is recovered at low centrifugal forces by fractionation of cell lysates on a discontinuous sucrose/sorbitol gradient. The plasma-membrane fraction is enriched 96-fold on a protein basis with respect to the specific radioactivity of 125I-labeled myeloma protein J539 in the homogenate. Electron microscopy showed long membrane profiles often associated with one another.

scholarly journals Polarized delivery of viral glycoproteins to the apical and basolateral plasma membranes of Madin-Darby canine kidney cells infected with temperature-sensitive viruses.

1985 ◽  
Vol 100 (1) ◽  
pp. 136-151 ◽  
Author(s):  
M J Rindler ◽  
I E Ivanov ◽  
H Plesken ◽  
D D Sabatini
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Plasma Membranes ◽  
Temperature Sensitive ◽  
Kidney Cells ◽  
Apical Surface ◽  
Nonpermissive Temperature ◽  
Madin Darby Canine Kidney ◽  
Darby Canine Kidney ◽  
Canine Kidney

The intracellular route followed by viral envelope glycoproteins in polarized Madin-Darby canine kidney cells was studied by using temperature-sensitive mutants of vesicular stomatitis virus (VSV) and influenza, in which, at the nonpermissive temperature (39.5 degrees C), the newly synthesized glycoproteins (G proteins) and hemagglutinin (HA), respectively, are not transported out of the endoplasmic reticulum. After infection with VSV and incubation at 39.5 degrees C for 4-5 h, synchronous transfer of G protein to the plasma membrane was initiated by shifting to the permissive temperature (32.5 degrees C). Immunoelectron microscopy showed that under these conditions the protein moved to the Golgi apparatus and from there directly to a region of the lateral plasma membrane near this organelle. G protein then seemed to diffuse progressively to basal regions of the cell surface and, only after it had accumulated in the basolateral domain, it began to appear on the apical surface near the intercellular junctions. The results of these experiments indicate that the VSV G protein must be sorted before its arrival at the cell surface, and suggest that passage to the apical domain occurs only late in infection when tight junctions are no longer an effective barrier. In complementary experiments, using the temperature-sensitive mutant of influenza, cultures were first shifted from the nonpermissive temperature (39.5 degrees C) to 18.5 degrees C, to allow entrance of the glycoprotein into the Golgi apparatus (see Matlin, K.S., and K. Simons, 1983, Cell, 34:233-243). Under these conditions HA accumulated in Golgi stacks and vesicles but did not reach the plasma membrane. When the temperature was subsequently shifted to 32.5 degrees C, HA rapidly appeared in discrete regions of the apical surface near, and often directly above, the Golgi elements, and later diffused throughout this surface. To ensure that the anti-HA antibodies had access to lateral domains, monolayers were treated with a hypertonic medium to dilate the intercellular spaces. Some labeling was then observed in the lateral plasma membranes soon after the shift, but this never increased beyond 1.0 gold particle/micron, whereas characteristic densities of labeling in apical surfaces soon became much higher (approximately 10 particles/micron). Our results suggest that the bulk of HA follows a direct pathway leading from the Golgi to regions of the apical surface close to trans-Golgi cisternae.

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