Effective tumor immunization induced by cells of elevated membrane-lipid microviscosity.

Shinitzky, Meir; Skornick, Yehuda; Haran-Ghera, Nechama

doi:10.1073/pnas.76.10.5313

Cited by 81 publications

(42 citation statements)

References 22 publications

(29 reference statements)

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“…The increased packing and decreased mobility of hydrocarbon chains under the latter condition may interfere with normal protein-protein and protein-lipid interactions and may also induce a change in ionic conductivity of the membrane. In the present study cholesteryl hemisuccinate has been used to modify the membrane fluidity by using the technique of PVP association as described by Shinitzky et al (28). These workers have found that cholesteryl hemisuccinate is more readily incorporated into biological membranes as compared with cholesterol but that the two compounds have essentially identical effects on fluidity.…”

Section: Methodsmentioning

confidence: 99%

“…Cholesteryl hemisuccinate was added to thylakoid membranes by the method of Shinitzky et al (28); 3.5% (w/w) of polyvinyl pyrrolidone (PVP, Mr 40,000, Sigma) was incubated with 25 mm Tris-HCl buffer (pH 7.5) for at least 30 min and cholesteryl hemisuccinate (Tris-salt), dissolved in a small amount of tetrahydrofuran, was added to give the required concentration. The cholesteryl hemisuccinate/PVP solution was then added to chloroplast suspensions and incubated for a few minutes at room temperature.…”

Section: Methodsmentioning

confidence: 99%

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Relationship between Thylakoid Membrane Fluidity and the Functioning of Pea Chloroplasts

Yamamoto¹,

Ford²,

Barber³

1981

Plant Physiol.

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Cholesteryl hemisuccinate has been incorporated into pea chloroplast thylakoids to investigate the relationship between fluidity and functioning of this membrane system. Levels of sterol which increased the apparent viscosity of the membrane, estimated by fluorescence polarization measurements using the lppboilic probe, 1,6-diphenyl-1,3,5 hexatriene, affected several photosynthetic processes. A decrease in fluidity was accompanied by an inhibition of dark limiting steps associated with electron transfer between photosystems two and one (PSII and PSI) as observed by the oxidation of the primary acceptor of PSII and by electron flow to ferricyanide. Also, treatment with cholesteryl hemisuccinate inhibited the saltinduced rise in chlorophyli fluorescence and changed the ionic conductivity of the membrane as judged by measurements of the decay of the lightinduced proton gradient. The results are discussed in terms of the effect of fluidity changes on the lateral dfffusion of plastoquinone and chlorophyli protein complexes in the lipid matrix of the membrane.There is increasing evidence that the fluidity of the chloroplast thylakoid membrane may play an important role in controlling the light reactions of photosynthesis (4, 24). The fluidity of biological membranes is determined mainly by the length and the degree of saturation of alkyl chains in fatty acids of the constituent lipids. Thylakoid membranes of higher plants contain galactolipids with highly unsaturated fatty acids and a small portion of phospho-and sulfolipids (1,5,15). Thus, a relatively low viscosity may be expected for the thylakoid membrane at room temperature (2). However, the membrane fluidity can be changed by varying the temperature of the chloroplast suspension and a great deal of evidence has accumulated suggesting effects of temperature on function ofchloroplasts, including electron transport, fluorescence changes, and other related reactions (6,9,13,14,16,19,20,22,29,30,33,34 thylakoid lipid phase on the functioning of various photosynthetic processes such as electron transport, ionic conductivity of the membrane, and cation-induced Chl fluorescence changes. Although this sterol occurs only at low levels in higher plants its effect on the physical properties of biological membranes in general is well documented. Thus, we have simply used this compound, added as the hemisuccinate, in an attempt to artificialy manipulate the fluidity of the thylakoid membrane. MATERIALS AND METHODSPea chloroplasts were prepared according to Nakatani and Barber (21), and then osmotically disrupted, washed once, and suspended in 0.33 M sorbitol and 1 mm Tris-HCl solution (pH 7.5). Cholesteryl hemisuccinate was added to thylakoid membranes by the method of Shinitzky et al. (28); 3.5% (w/w) of polyvinyl pyrrolidone (PVP, Mr 40,000, Sigma) was incubated with 25 mm Tris-HCl buffer (pH 7.5) for at least 30 min and cholesteryl hemisuccinate (Tris-salt), dissolved in a small amount of tetrahydrofuran, was added to give the required concentration. The cholestery...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Relationship between Thylakoid Membrane Fluidity and the Functioning of Pea Chloroplasts

Yamamoto¹,

Ford²,

Barber³

1981

Plant Physiol.

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Section: Introductionmentioning

confidence: 99%

“…Cholesterol incorporation into mitochondrial membranes was performed using cholesterol-coated glass beads according to Coleman et al (1978). Cholesteryl hemisuccinate was incorporated according to Shinitzky et al (1979) by incubating the membranes with a medium containing 3.50% polyvinylpyrrolidone (Mr 40000; Sigma).Analytical methods Cytochrome c1 concentration was determined from the ascorbatereduced minus ferricyanide-oxidized spectrum in a Jasco 7850 spectrophotometer using a molar absorption coefficient of 17.5 mM-1 cm-' at 552 nm minus 541 nm; cytochrome b concentration was determined from the dithionite-reduced minus oxidized spectrum using a molar absorption coefficient of 25 mM-1 cm-1 at 562 minus 576 nm. The content of bel complex was routinely evaluated by dividing the cytochrome b content by two.…”

mentioning

confidence: 99%

Steady-state kinetics of ubiquinol-cytochrome c reductase in bovine heart submitochondrial particles: diffusional effects

Fato

Cavazzoni

Castelluccio

et al. 1993

Biochemical Journal

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In an attempt to establish the relative importance of diffusional and chemical control in the reactivity of the two substrates, ubiquinol and cytochrome c, we have undertaken an extensive characterization of the steady-state kinetics of ubiquinol-cytochrome c reductase (EC 1.10.2.2) when present in open submitochondrial particles from bovine heart. The kinetic pattern follows a Ping Pong mechanism; contrary to the situation found with the isolated enzyme [Speck and Margoliash (1984) J. Biol. Chem. 259, 1064-1072, and confirmed in our laboratory], no substrate inhibition by oxidized cytochrome c was observed with the membrane-bound enzyme. Endogenous oxidized ubiquinone-10 is unable to exert product inhibition under the conditions employed. In the Ping Pong mechanism for this enzyme, the reaction scheme can be clearly divided into two parts, and the Kmin (keat/Km) value for one substrate is independent of the rate constant for the second substrate. Both ubiquinol-1 and ubiquinol-2 can be used as electron donors reacting with the enzyme from within the lipid bilayer [Fato, Castelluccio, Palmer and Lenaz (1988) Biochim. Biophys. Acta 932,[216][217][218][219][220][221][222]; the kmin values for ubiquinols, when calculated on the basis of their membranous concentrations, are significantly lower than the kmin for cytochrome c. The temperature-dependence of the kinetic parameters was investigated by titrating each of the substrates under quasi-saturating concentrations of the second substrate. Arrhenius plots of Vm.. extrapolated from both cytochrome c and ubiquinol titrations were linear, when care was taken to verify the quasi-saturating concentrations of the fixed co-substrate. The Arrhenius plots for the kmin values for both ubiquinol and cytochrome c were linear, but the activation energy was much higher for the former, particularly when calculated for ubiquinol dissolved in the lipid phase; the very low value of activation energy of the kmin for cytochrome c is strong support for diffusion control being present in the reaction of cytochrome c with the membranous enzyme. In contrast to the soluble enzyme, ubiquinone titrations of submitochondrial particles at low cytochrome c concentrations deviated from hyperbolic behaviour. Changing the medium viscosity with either poly(ethylene glycol) or sucrose had a strong effect on the cytochrome c kmin, whereas the change in the ubiquinol kmin was much smaller. From the viscosity studies the extent of diffusional control could be calculated, revealing that the reaction with cytochrome c was mostly diffusion-limited. The viscosity of the membrane was changed by incorporating cholesterol; no significant effect on the ubiquinol kmin ascribable to diffusion control could be recognized. The bulk of the studies reported here strongly suggest that ubiquinol-cytochrome c reductase is subject to diffusion control of the interaction of cytochrome c from the aqueous medium, but not of the interaction of the short-chain ubiquinols from the membrane interior. INTRODUCTIONSeveral enzy...

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“…This hypothesis is supported by the observation that the cell fluidity varies markedly with the age of the tumour (in preparation). Thus, it has been reported that a modification of cell fluidity modulates the expression of cell-surface antigens (Borochov & Shinitzky, 1976;Shinitzky et al, 1979).…”

Section: Discussionmentioning

confidence: 99%

A comparative study of some growth characteristics and cell-surface properties of neoplastic cells

Bischoff¹,

Robert²,

Donner³

1981

Br J Cancer

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Summary.-Tumour cells from a polyoma-induced ascitic tumour were fractionated on the basis of the electrical charge on the cell surface by free-flow electrophoresis. Several characteristics of tumour cells have been investigated: (1) differences in the proliferation and antigenicity within the tumour at any point in time; (2) variation in proliferative potential with the ageing of the tumour.In early ascitic tumours, electrophoretically fractionated cells exhibit very similar proliferative characteristics. However, most DNA synthesis was found in slowmoving cells. The behaviour of older tumours was different. Proliferative potential and DNA synthesis were weaker and restricted to slow-moving cells, suggesting that fast-moving cells in older tumours were resting cells. An enrichment in immunoglobulin-bearing cells was also found in slow-moving cell fractions, supporting the hypothesis of variability in expression of tumour-specific antigens. The role of cellsurface properties and cell kinetics is discussed in relation to electrical surface charge, which might be involved in cell dissemination and metastasis. Thus, freeflow electrophoresis represents a satisfactory approach to isolate tumour cell subpopulations with characteristics such as high proliferative potential or increased expression of tumour antigens.

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Effective tumor immunization induced by cells of elevated membrane-lipid microviscosity.

Cited by 81 publications

References 22 publications

Relationship between Thylakoid Membrane Fluidity and the Functioning of Pea Chloroplasts

Relationship between Thylakoid Membrane Fluidity and the Functioning of Pea Chloroplasts

Steady-state kinetics of ubiquinol-cytochrome c reductase in bovine heart submitochondrial particles: diffusional effects

A comparative study of some growth characteristics and cell-surface properties of neoplastic cells

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