Modular Assembly of Synthetic Proteins that Span the Plasma Membrane in Mammalian Cells

A Triton X-100-lysed cell system has been used to identify calmodulin on the cytoskeleton of 3T3 and transformed SV3T3 cells. By indirect immunofluorescence, calmodulin was found to be associated with both the cytoplasmic microtubule complex and the centrosomes. A number of cytoplasmic microtubules more resistant to disassembly upon either cold (0-4 degrees C) or hypotonic treatment, as well as following dilution have been identified. Most of the stable microtubules appeared to be associated with the centrosome at one end and with the plasma membrane at the other end. These microtubules could be induced to depolymerize, however, by micromolar Ca++ concentrations. These data suggest that, by interacting directly with the microtubule, calmodulin may influence microtubule assembly and ensure the Ca++-sensitivity of both mitotic and cytoplasmic microtubules.

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Phosphatidylethanol stimulates the plasma-membrane calcium pump from human erythrocytes

Biochemical Journal ◽

10.1042/bj3170933 ◽

1996 ◽

Vol 317 (3) ◽

pp. 933-938 ◽

Cited By ~ 15

Author(s):

Meylin SUJU ◽

Marbelly DAVILA ◽

German POLEO ◽

Roberto DOCAMPO ◽

Gustavo BENAIM

Keyword(s):

Plasma Membrane ◽

Phospholipase D ◽

Mammalian Cells ◽

Human Erythrocytes ◽

Maximal Velocity ◽

Ethanol Intoxication ◽

Solubilized Enzyme ◽

Acidic Phospholipids ◽

Additive Combination ◽

Stimulation Of

Phosphatidylethanol is formed by ‘transphosphatidylation’ of phospholipids with ethanol catalysed by phospholipase D and can be accumulated in the plasma membrane of mammalian cells after treatment of animals with ethanol. In the present work we show that phosphatidylalcohols, such as phosphatidylethanol and phosphatidylbutanol, produced a twofold stimulation of the Ca2+-ATPase activity of human erythrocytes. This stimulation occurs with the purified, solubilized enzyme as well as with ghost preparations, where the enzyme is in its natural lipidic environment and is different to that obtained with other acidic phospholipids such as phosphatidylserine. Addition of either phosphatidylserine, phosphatidylethanol or phosphatidylbutanol to the purified Ca2+-ATPase, or to ghosts preparations, increased the affinity of the enzyme for Ca2+ and the maximal velocity of the reaction as compared with controls in the absence of acidic phospholipids. However, in contrast with what occurs with phosphatidylserine, simultaneous addition of phosphatidylalcohols and calmodulin increased the affinity of the enzyme for Ca2+ to a greater extent than each added separately. When ethanol was added to either the purified erythrocyte Ca2+-ATPase or to erythrocyte-ghost preparations in the presence of acidic phospholipids, an additive effect was observed. There was an increase in the affinity for Ca2+ and in the maximal velocity of the reaction, well above the values obtained with ethanol or with the acidic phospholipids tested separately. These findings could have pharmacological importance. It is conceivable that the decrease in the intracellular Ca2+ concentration that has been reported in erythrocytes as a result of ethanol intoxication could be due to the stimulation of the Ca2+-ATPase by the accumulated phosphatidylethanol, to a direct effect of ethanol on the enzyme or to an additive combination of both.

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The eisosome core is composed of BAR domain proteins

Molecular Biology of the Cell ◽

10.1091/mbc.e10-12-1021 ◽

2011 ◽

Vol 22 (13) ◽

pp. 2360-2372 ◽

Cited By ~ 66

Author(s):

Agustina Olivera-Couto ◽

Martin Graña ◽

Laura Harispe ◽

Pablo S. Aguilar

Keyword(s):

Plasma Membrane ◽

Mammalian Cells ◽

Site Directed Mutagenesis ◽

Bar Domain ◽

Macromolecular Assemblies ◽

Surface Patches ◽

Cytoplasmic Proteins ◽

Associated Proteins ◽

Core Components ◽

Membrane Bending

Eisosomes define sites of plasma membrane organization. In Saccharomyces cerevisiae, eisosomes delimit furrow-like plasma membrane invaginations that concentrate sterols, transporters, and signaling molecules. Eisosomes are static macromolecular assemblies composed of cytoplasmic proteins, most of which have no known function. In this study, we used a bioinformatics approach to analyze a set of 20 eisosome proteins. We found that the core components of eisosomes, paralogue proteins Pil1 and Lsp1, are distant homologues of membrane-sculpting Bin/amphiphysin/Rvs (BAR) proteins. Consistent with this finding, purified recombinant Pil1 and Lsp1 tubulated liposomes and formed tubules when the proteins were overexpressed in mammalian cells. Structural homology modeling and site-directed mutagenesis indicate that Pil1 positively charged surface patches are needed for membrane binding and liposome tubulation. Pil1 BAR domain mutants were defective in both eisosome assembly and plasma membrane domain organization. In addition, we found that eisosome-associated proteins Slm1 and Slm2 have F-BAR domains and that these domains are needed for targeting to furrow-like plasma membrane invaginations. Our results support a model in which BAR domain protein–mediated membrane bending leads to clustering of lipids and proteins within the plasma membrane.

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Depletion of rafts in late endocytic membranes is controlled by NPC1-dependent recycling of cholesterol to the plasma membrane

Journal of Cell Science ◽

10.1242/jcs.114.10.1893 ◽

2001 ◽

Vol 114 (10) ◽

pp. 1893-1900 ◽

Cited By ~ 3

Author(s):

S. Lusa ◽

T.S. Blom ◽

E.L. Eskelinen ◽

E. Kuismanen ◽

J.E. Mansson ◽

...

Keyword(s):

Plasma Membrane ◽

Protein Interactions ◽

Mammalian Cells ◽

Intracellular Transport ◽

Ldl Cholesterol ◽

Normal Cells ◽

Recycling Endosomes ◽

Regulate Protein ◽

Niemann Pick ◽

Accumulation Characteristic

In mammalian cells, cholesterol is thought to associate with sphingolipids to form lateral membrane domains termed rafts. Increasing evidence suggests that rafts regulate protein interactions, for example, during signalling, intracellular transport and host-pathogen interactions. Rafts are present in cholesterol-sphingolipid-enriched membranes, including early and recycling endosomes, but whether rafts are found in late endocytic organelles has not been analyzed. In this study, we analyzed the association of cholesterol and late endosomal proteins with low-density detergent-resistant membranes (DRMs) in normal cells and in cells with lysosomal cholesterol-sphingolipid accumulation. In normal cells, the majority of [(3)H]cholesterol released from [(3)H]cholesterol ester-LDL associated with detergent-soluble membranes, was rapidly transported to the plasma membrane and became increasingly insoluble with time. In Niemann-Pick C1 (NPC1) protein-deficient lipidosis cells, the association of LDL-cholesterol with DRMs was enhanced and its transport to the plasma membrane was inhibited. In addition, the NPC1 protein was normally recovered in detergent-soluble membranes and its association with DRMs was enhanced by lysosomal cholesterol loading. Moreover, lysosomal cholesterol deposition was kinetically paralleled by the sequestration of sphingolipids and formation of multilamellar bodies in late endocytic organelles. These results suggest that late endocytic organelles are normally raft-poor and that endocytosed LDL-cholesterol is efficiently recycled to the plasma membrane in an NPC1-dependent process. The cholesterol-sphingolipid accumulation characteristic to NPC disease, and potentially to other sphingolipidoses, causes an overcrowding of rafts forming lamellar bodies in the degradative compartments.

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Characterization of two Mg2+transporters in sealed plasma membrane vesicles from rat liver

AJP Cell Physiology ◽

10.1152/ajpcell.1998.275.4.c995 ◽

1998 ◽

Vol 275 (4) ◽

pp. C995-C1008 ◽

Cited By ~ 49

Author(s):

Christie Cefaratti ◽

Andrea Romani ◽

Antonio Scarpa

Keyword(s):

Plasma Membrane ◽

Rat Liver ◽

Intracellular Signaling ◽

Mammalian Cells ◽

Plasma Membranes ◽

Membrane Vesicles ◽

Channel Blockers ◽

Transport Mechanisms ◽

Plasma Membrane Vesicles ◽

New Information

The plasma membrane of mammalian cells possesses rapid Mg2+ transport mechanisms. The identity of Mg2+ transporters is unknown, and so are their properties. In this study, Mg2+ transporters were characterized using a biochemically and morphologically standardized preparation of sealed rat liver plasma membranes (LPM) whose intravesicular content could be set and controlled. The system has the advantages that it is not regulated by intracellular signaling machinery and that the intravesicular ion milieu can be designed. The results indicate that 1) LPM retain trapped intravesicular total Mg2+with negligible leak; 2) the addition of Na+ or Ca2+ induces a concentration- and temperature-dependent efflux corresponding to 30–50% of the intravesicular Mg2+; 3) the rate of flux is very rapid (137.6 and 86.8 nmol total Mg2+ ⋅ μm−2 ⋅ min−1after Na+ and Ca2+ addition, respectively); 4) coaddition of maximal concentrations of Na+ and Ca2+ induces an additive Mg2+ efflux; 5) both Na+- and Ca2+-stimulated Mg2+ effluxes are inhibited by amiloride, imipramine, or quinidine but not by vanadate or Ca2+ channel blockers; 6) extracellular Na+ or Ca2+ can stimulate Mg2+ efflux in the absence of Mg2+ gradients; and 7) Mg2+ uptake occurs in LPM loaded with Na+ but not with Ca2+, thus indicating that Na+/Mg2+but not Ca2+/Mg2+exchange is reversible. These data are consistent with the operation of two distinct Mg2+ transport mechanisms and provide new information on rates of Mg2+ transport, specificity of the cotransported ions, and reversibility of the transport.

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Characterization of the plasma-membrane calcium pump from Trypanosoma cruzi

Biochemical Journal ◽

10.1042/bj3060299 ◽

1995 ◽

Vol 306 (1) ◽

pp. 299-303 ◽

Cited By ~ 21

Author(s):

G Benaim ◽

S N J Moreno ◽

G Hutchinson ◽

V Cervino ◽

T Hermoso ◽

...

Keyword(s):

Plasma Membrane ◽

Trypanosoma Cruzi ◽

Mammalian Cells ◽

Membrane Vesicles ◽

High Sensitivity ◽

Bovine Brain ◽

Calcium Pump ◽

Plasma Membrane Vesicles ◽

P Type

Despite previous reports [McLaughlin (1985) Mol. Biochem. Parasitol. 15, 189-201; Ghosh, Ray, Sarkar and Bhaduri (1990) J. Biol. Chem. 265, 11345-11351; Mazumder, Mukherjee, Ghosh, Ray and Bhaduri (1992) J. Biol. Chem. 267, 18440-18446] suggesting that the plasma-membrane Ca(2+)-ATPases of different trypanosomatids differ from the Ca2+ pumps present in mammalian cells, Trypanosoma cruzi plasma-membrane Ca(2+)-ATPase shares several characteristics with the Ca2+ pumps present in other systems. This enzyme could be partially purified from epimastigote plasma-membrane vesicles using calmodulin-agarose affinity chromatography. The activity of the partially purified enzyme was stimulated by T. cruzi or bovine brain calmodulin. In addition, the enzyme cross-reacted with antiserum and monoclonal antibody 5F10 raised against human red-blood-cell Ca(2+)-ATPase, has a molecular mass of 140 kDa and forms Ca(2+)-dependent hydroxylamine-sensitive phosphorylated intermediates. These results, together with its high sensitivity to vanadate, indicate that this enzyme belongs to the P-type class of ionic pumps.

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Physiological role and regulation of the Na+/H+ exchanger

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y06-065 ◽

2006 ◽

Vol 84 (11) ◽

pp. 1081-1095 ◽

Cited By ~ 149

Author(s):

Mackenzie E. Malo ◽

Larry Fliegel

Keyword(s):

Plasma Membrane ◽

Amino Acid ◽

Mammalian Cells ◽

Cell Movement ◽

Physiological Role ◽

Membrane Domain ◽

Post Translational Modifications ◽

Homologous Protein ◽

The Family ◽

Extracellular Sodium

In mammalian eukaryotic cells, the Na+/H+ exchanger is a family of membrane proteins that regulates ions fluxes across membranes. Plasma membrane isoforms of this protein extrude 1 intracellular proton in exchange for 1 extracellular sodium. The family of Na+/H+ exchangers (NHEs) consists of 9 known isoforms, NHE1–NHE9. The NHE1 isoform was the first discovered, is the best characterized, and exists on the plasma membrane of all mammalian cells. It contains an N-terminal 500 amino acid membrane domain that transports ions, plus a 315 amino acid C-terminal, the intracellular regulatory domain. The Na+/H+ exchanger is regulated by both post-translational modifications including protein kinase-mediated phosphorylation, plus by a number of regulatory-binding proteins including phosphatidylinositol-4,5-bisphosphate, calcineurin homologous protein, ezrin, radixin and moesin, calmodulin, carbonic anhydrase II, and tescalcin. The Na+/H+ exchanger is involved in a variety of complex physiological and pathological events that include regulation of intracellular pH, cell movement, heart disease, and cancer. This review summarizes recent advances in the understanding of the physiological role and regulation of this protein.

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Host Cell Plasma Membrane Phosphatidylserine Regulates the Assembly and Budding of Ebola Virus

Journal of Virology ◽

10.1128/jvi.01087-15 ◽

2015 ◽

Vol 89 (18) ◽

pp. 9440-9453 ◽

Cited By ~ 47

Author(s):

Emmanuel Adu-Gyamfi ◽

Kristen A. Johnson ◽

Mark E. Fraser ◽

Jordan L. Scott ◽

Smita P. Soni ◽

...

Keyword(s):

Plasma Membrane ◽

Host Cell ◽

Human Cell ◽

Mammalian Cells ◽

Matrix Protein ◽

Ebola Virus ◽

Cell Plasma Membrane ◽

Replication Process ◽

Cell Plasma

ABSTRACTLipid-enveloped viruses replicate and bud from the host cell where they acquire their lipid coat. Ebola virus, which buds from the plasma membrane of the host cell, causes viral hemorrhagic fever and has a high fatality rate. To date, little has been known about how budding and egress of Ebola virus are mediated at the plasma membrane. We have found that the lipid phosphatidylserine (PS) regulates the assembly of Ebola virus matrix protein VP40. VP40 binds PS-containing membranes with nanomolar affinity, and binding of PS regulates VP40 localization and oligomerization on the plasma membrane inner leaflet. Further, alteration of PS levels in mammalian cells inhibits assembly and egress of VP40. Notably, interactions of VP40 with the plasma membrane induced exposure of PS on the outer leaflet of the plasma membrane at sites of egress, whereas PS is typically found only on the inner leaflet. Taking the data together, we present a model accounting for the role of plasma membrane PS in assembly of Ebola virus-like particles.IMPORTANCEThe lipid-enveloped Ebola virus causes severe infection with a high mortality rate and currently lacks FDA-approved therapeutics or vaccines. Ebola virus harbors just seven genes in its genome, and there is a critical requirement for acquisition of its lipid envelope from the plasma membrane of the human cell that it infects during the replication process. There is, however, a dearth of information available on the required contents of this envelope for egress and subsequent attachment and entry. Here we demonstrate that plasma membrane phosphatidylserine is critical for Ebola virus budding from the host cell plasma membrane. This report, to our knowledge, is the first to highlight the role of lipids in human cell membranes in the Ebola virus replication cycle and draws a clear link between selective binding and transport of a lipid across the membrane of the human cell and use of that lipid for subsequent viral entry.

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