Studies on mixed monolayers of phospholipids and fusogenic lipids

Maggio, Bruno; Lucy, J. A.

doi:10.1042/bj1490597

Cited by 65 publications

(48 citation statements)

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“…Conversely, lipids chemically similar to those but not showing these type of interactions are ineffective as fusogenics [2,3]. On this basis it was surmised that a reduction of the electrostatic field perpendicular to the surface of the lipid bilayer induced by a lipid or a water-soluble substance is a key event for the initial increase of the membrane permeability and aggregation that leads to membrane fusion [6,7].…”

Section: Discussionmentioning

confidence: 99%

Induction of membrane fusion by polysialogangliosides

1978

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Section: Discussionmentioning

confidence: 99%

Induction of membrane fusion by polysialogangliosides

1978

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“…Fusogenic lipids interact with monolayers of phosphatidylcholine to allow closer packing in the monolayer and a rather small decrease in the surface potential (Maggio & Lucy, 1975, 1976. Since poly(ethylene glycol)-6000 is relatively non-toxic (as compared with fusogenic lipids), gives an exceptionally high incidence of chemically induced cell fusion (Pontecorvo, 1975) and decreases the surface potential of lipid monolayers by several hundred millivolts, a decrease in the surface potential of biological membranes may be of major importance in membrane fusion.…”

Section: Discussionmentioning

confidence: 99%

Poly(ethylene glycol), surface potential and cell fusion

Maggio

Ahkong

Lucy

1976

Biochemical Journal

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111

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Poly(ethylene glycol), glycerol and dimethyl sulphoxide markedly decrease the surface potentials of monolayers of phosphatidylcholine and phosphatidylethanolamine. This finding is discussed in relation to the properties of hen erythrocytes undergoing fusion induced by poly(ethylene glycol).Poly(ethylene glycol)-6000 induces the fusion of plant protoplasts (Kao & Michayluk, 1974), hen erythrocytes (Ahkong et al., 1975a), hen erythrocytes with yeast protoplasts (Ahkong et al., 1975b), and mammalian cells (Pontecorvo, 1975). We have studied the actions on monolayers of phospholipids of poly(ethylene glycol), glycerol, sorbitol, sucrose and dimethyl sulphoxide, all of which fuse hen ,erythrocytes (Ahkong et al., 1975a), to obtain information relevant to the molecular mechanisms by which these molecules may induce cell fusion. Materials and MethodsAnalaR NaCl, sucrose, sorbitol, glycerol, poly-(ethylene glycol) mol.wt. 1500 and poly(ethylene oxide) mol.wts. 3 x 105 and 5 x 106 were from BDH Chemicals, Poole, Dorset, U.K. Poly(ethylene glycol) and poly(ethylene oxide) describe the same polymer, -[CH2-CH2-0]"-, prepared from different monomers. The term poly(ethylene glycol) is used in this present paper, individual polymers being identified by their molecular weight. Dimethyl sulphoxide was from Sigma (London) Chemical Co., London S.W.6, U.K. Dipalmitoylglycerylphosphorylcholine, dipalmitoylglycerylphosphorylethanolamine and poly(ethylene glycol) mol.wt. 6000 were from Koch-Light Laboratories, Colnbrook, Bucks., U.K. Phospholipid monolayers were prepared from solutions in chloroform, and the surface pressures, molecular areas and surface potentials of the monolayers were recorded automatically, as described previously (Maggo & Lucy, 1975, 1976. All subphases contained NaCl (145mM); their pH was adjusted to 5.6 with HCI (5M) or NaOH (5M). The surface potential and surface pressure of each subphase were adjusted to give a zero reading before spreading of the phos. pholipid monolayer. Isotherms were obtained in duplicate; they were usually reproducible within * Present address: Departmento de Quimica Biologica, Universidad Nacional de Cordoba, Argentina. Vol. 158 ±0.02nm2, +lmN*m1l (+ldyn-cm-1) and ±lOmV. For some subphases containing high concentrations of organic solute, reproducibility was not better than 0.04nm2 in molecular areas, +2mN m-1 in surface pressure and ±20mV in surface potential; the isotherm was then obtained in triplicate, and the curves were averaged.Hen erythrocytes were prepared for experiments on cell fusion as described previously (Ahkong et al., 1973). ResultsPhospholipid monolayers Fig. 1 shows the surface potential-area and surface pressure-area curves for monolayers of phosphatidylcholine and phosphatidylethanolamine on subphases containing two small organic solutes and two polymers. Comparable observations (not shown) were made with subphases contaiing the other small organic solutes and polymers studied (see the Materials and Methods section). With subphases containing lower concentrations ...

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“…Therefore, the cells are also being exposed to monoacylglycerols, which have been shown, along with diacylglycerols, to possess fusogenic properties [42,43]. The inability of OaG to mimic completely the effects of TPA on cultured HL-60 cells has been a subject of discussion in recent papers [20,23,24].…”

Section: Discussionmentioning

confidence: 99%

sn‐1,2‐Diacylglycerols and phorbol diesters: Uptake, metabolism, and subsequent assimilation of the diacylglycerol metabolites into complex lipids of cultured cells

Welsh

Cabot

1987

J of Cellular Biochemistry

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The cell-permeable diacylglycerol mediators have been shown to mimic partially the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on cultured cells. In order to evaluate the metabolic stability of the lipid mediators, several radiolabeled diacylglycerols were synthesized and their uptake and intracellular fate in cultured HL-60 (human promyelocytic leukemia) cells was compared with TPA. In addition to whole cell assessment, the stability of diacyl lipids and TPA was evaluated in a buffer/water system and in the presence of serum and subcellular fractions. The compounds studied include 1,2-dioleoyl-sn-glycerol (DiOG), 1-oleoyl-2-acetyl-sn-glycerol (OaG), 1-palmitoyl-2-acetyl-sn-glycerol (PaG), the ether-linked analog 1-palmityl-2-acetyl-sn-glycerol (ePaG), and TPA. TPA was comparatively stable to lipase hydrolysis in all systems examined. First, the data show that within 5 min at pH 7.9, nearly 50% of the PaG (originally greater than 92% 1,2-isomer) had isomerized, and rapid formation of the 1,3-isomer also occurred with OaG and ePaG. The metabolism of OaG and PaG by serum hydrolases, using a reaction medium containing 10% serum, was chiefly by acetate hydrolysis; however, fatty acid was also liberated. After a 60-min incubation 68% of the [14C]OaG was converted, by serum enzymes, to monooleoylglycerol plus oleic acid. Heat-inactivation of serum reduced the enzymatic formation of fatty acid by 60-70%. ePaG was also metabolized by serum enzymes, but the ether-linked alkylglycerol product was stable. The results of cell-free studies (postmitochondrial supernatant) showed that cellular enzymes were present that could, like serum, convert the diacylglycerols to monoacylglycerols and free fatty acids. Studies using cultured cells showed that radiolabeled OaG, PaG, and ePaG were rapidly taken up by the cells and metabolized. Labeled metabolic products from the diacylglycerols appeared, in a time-dependent manner, in cellular phospholipids and triacylglycerols. The results from experiments employing 1-acyl-2-acetyl-sn-[3H]glycerol and [3H]acyl-2-acetyl-sn-glycerol indicate that the intracellular mode of mediator metabolism is via complete hydrolysis with subsequent incorporation of 3H-acyl groups into complex lipids. Data are also presented which show that a substantial amount of cellular lipid acyl group modification occurs and large amounts of glycerol are produced when cells are cultured with OaG. Collectively, these results demonstrate that the diacylglycerol mediators, when compared with TPA, are not stable and are metabolized by both serum and cellular enzymes.(ABSTRACT TRUNCATED AT 400 WORDS)

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Studies on mixed monolayers of phospholipids and fusogenic lipids

Cited by 65 publications

References 17 publications

Induction of membrane fusion by polysialogangliosides

Induction of membrane fusion by polysialogangliosides

Poly(ethylene glycol), surface potential and cell fusion

sn‐1,2‐Diacylglycerols and phorbol diesters: Uptake, metabolism, and subsequent assimilation of the diacylglycerol metabolites into complex lipids of cultured cells

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