Phosphate-calcium induced fusion of chicken erythrocytes

Majumdar, Sabita; Baker, Richard F.

doi:10.1016/0014-4827(80)90483-8

Cited by 14 publications

(8 citation statements)

References 19 publications

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“…In agreement with results presented by others [7,81, addition of ghosts to phosphate alone or to preformed calcium phosphate phases, did not suffice to induce membrane fusion (Table 2). Direct evidence was thus obtained, showing that (local) fusion was not induced under these conditions and, more importantly, excluding the possibility that the process secondary to fusion, i.e.…”

Section: Role Of Calcium Phosphate Complexes In Calcium-phosphate-indsupporting

confidence: 81%

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Fusion of erythrocyte ghosts induced by calcium phosphate

Hoekstra

Wilschut

Scherphof

1985

European Journal of Biochemistry

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Using an assay which allows continuous monitoring of the mixing of aqueous contents during membrane fusion, we have investigated the kinetics of calcium-phosphate-induced fusion of erythrocyte ghosts. In the presence of 10 mM phosphate, the threshold concentration for Ca2+-induced fusion was 1.25 mM, while the optimal concentration was approx. 1.75 mM Ca2+. Further enhancement of the cation concentration ( 2 2 mM) inhibited fusion of the ghosts. Initiation of fusion required the addition of phosphate prior to the addition of Ca2+, indicating that the combined interaction of Ca2+ and phosphate in or at the plane of the bilayer was a prerequisite for the induction of fusion. Furthermore, fusion was greatly facilitated upon transformation of calcium phosphate in the bulk medium from an amorphous to a solid, crystalline phase. It is suggested that membrane aggregation, and hence fusion, is facilitated by the formation of crystalline calcium phosphate nucleating on the ghost membrane. La3+, Mg2+ and Mn2+ did not trigger the fusion process, although aggregation of the ghosts did occur. Under conditions where calcium phosphate precipitation was inhibited, lanthanum phosphate precipitates facilitated fusion after prior treatment of ghosts with phosphate and Ca2+. These results indicated that fusion-prone conditions were induced prior to calcium phosphate precipitation. It is proposed that prior to calcium phosphate precipitation membrane changes are induced by separate interaction of Ca2 + and phosphate with the ghost membrane. Such an interaction could then render the ghosts susceptible to fusion and as soon as conditions are provided allowing close contact between adjacent membranes, fusion will be observed.

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Section: Role Of Calcium Phosphate Complexes In Calcium-phosphate-indsupporting

confidence: 81%

“…Obviously, the kinetics of both events will differ. In the case of calcium-phosphateinduced fusion of erythrocytes [7] or ghosts [8] (unpublished observation). light microscopic examination reveals the presence of large (swollen) polyghosts or polyerythrocytes after a time interval of 10-12 min.…”

Section: Discussionmentioning

confidence: 99%

Fusion of erythrocyte ghosts induced by calcium phosphate

Hoekstra

Wilschut

Scherphof

1985

European Journal of Biochemistry

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“…Establishing Optimal Conditions for Examining Ca2+-P04-Induced HEves and REves Aggregation. Previous studies of Ca2+-P04-induced membrane aggregation and/or fusion have been conducted under conditions where the total [Ca2+], [P04], pH, or temperature was reported (Zakai et al, 1976(Zakai et al, , 1977Majumdar & Baker, 1980;Fraley et al, 1980). In order to provide a basis for comparing the results obtained in the present study to those previously published, and to determine the optimal conditions for studying HEves and REves aggregation, we examined the effects of pH, [Ca2+], [P04], and order of ion addition on vesicle aggregation.…”

Section: Resultsmentioning

confidence: 99%

“…In earlier studies (Zakai et al, 1976(Zakai et al, , 1977Majumdar & Baker, 1980;Baker & Kalra, 1979), it has been suggested that Ca2+-P04 may be inducing membrane aggregation and/or fusion by modifying the erythrocytes' spectrin-actin cytoskeletal network and inducing the lateral aggregation of membrane proteins. While Ca2+-P04-induced modifications in the spectrin-actin cytoskeletal network of erythrocytes are quite likely, such effects are ruled out in the present study since both the HEves and REves are cytoskeleton free (Leonards & Ohki, 1983) yet undergo extensive vesicle aggregation.…”

Section: Discussionmentioning

confidence: 99%

“…Although erythrocytes do not normally fuse in nature, their relative simplicity, ready availability, and well-characterized chemical composition strongly recom-mend their use. As a result, it has been demonstrated that various chemical agents, such as oleoylglycerol (Quirk et al, 1978;Blow et al, 1979), lysolecithin (Lucy, 1976), calciumphosphate (Zakai et al, 1976(Zakai et al, , 1977Majumdar & Baker, 1980), polyethylene glycol) (Ahkong et al, 1975;Knutton, 1979a,b), and inactivated Sendi virus (Peretz et al, 1974;Volsky & Loyter, 1978; Knutton, 1979a,b;Lalazar & Loyter, 1979;Sekiguchi et al, 1981), will induce the aggregation and fusion of erythrocyte membranes.…”

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confidence: 99%

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Roles of lipids and proteins in the calcium(2+)-phosphate-induced aggregation of cytoskeleton-free erythrocyte vesicle membranes

Leonards¹,

Ohki²

1984

Biochemistry

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The roles of lipids and proteins in Ca2+-PO4-induced membrane aggregation were investigated. Cytoskeleton-free vesicles derived from intact human and rabbit erythrocytes (HEves and REves, respectively) were employed as a model system. The HEves and REves have a simplified membrane protein composition [band 3 proteins and glycoproteins PAS-1, -2, and -3 (HEves)] and normal lipid composition. Optimal experimental conditions for pH, [PO4], and [CaCl2] were determined for quantitatively examining the dynamics and extent of HEves and REves aggregation, measured turbidimetrically. The aggregation process was found to be quite sensitive to small changes in pH and [PO4] and much less sensitive to [CaCl2]. The roles of membrane proteins in vesicle aggregation were examined by selectively modifying the proteins enzymatically. The roles of lipids were studied by using sonicated lipid vesicles [small unilamellar vesicles (SUVs)] made from Dodge ghost lipid extracts. Enzymatic treatment with trypsin, chymotrypsin, or Pronase had no effect on either the rates or the extent of vesicle aggregation (2-min incubation period). Neuraminidase treatment reduced both factors by approximately 20%. SUVs aggregated with Ca2+-PO4 in a way which depended on the PO4/lipid ratio. Together the results suggest the following: (1) PO4 is associated with the vesicle surface, involving the membrane lipids; (2) the vesicle + PO4 incubation time component of the PO4 effect is eliminated by enzymatically modifying the vesicle membrane proteins; (3) qualitative, rather than quantitative, properties of sialic acid containing molecules affect vesicle aggregation; and (4) with the exception of the incubation time effect, membrane proteins seem neither to promote nor to inhibit Ca2+-PO4-induced HEves or REves aggregation.

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Molecular Aspects of Membrane Fusion

Lucy¹

1984

Membrane Processes

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Phosphate-calcium induced fusion of chicken erythrocytes

Cited by 14 publications

References 19 publications

Fusion of erythrocyte ghosts induced by calcium phosphate

Fusion of erythrocyte ghosts induced by calcium phosphate

Roles of lipids and proteins in the calcium(2+)-phosphate-induced aggregation of cytoskeleton-free erythrocyte vesicle membranes

Molecular Aspects of Membrane Fusion

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