Interaction of calcium and cholesterol sulphate induces membrane destabilization and fusion: implications for the acrosome reaction

doi:10.1016/0005-2736(90)90366-V

Biochimica et Biophysica Acta (BBA) - Biomembranes

Volume 1024, Issue 2, 24 May 1990, Pages 367-372

https://doi.org/10.1016/0005-2736(90)90366-V Get rights and content

Abstract

Cholesterol sulphate is a potent stabilizer of membrane bilayer structure in both dielaidoylphosphatidylethanolamine and egg phosphatidylethanolamine model membranes, however, the addition of calcium abolishes this bilayer stabilization. Calcium also induces fusion and leakage of egg phosphatidylethanolamine large unilamellar vesicles containing cholesterol sulphate, but has no effect on fusion or leakage of egg phosphatidylcholine large unilamellar vesicles containing cholesterol sulphate. With egg phosphatidylethanolamine liposomes, the initial rate, and extent of fusion, at constant calcium concentration, vary inversely with the mol percentage of cholesterol sulphate present in the vesicle membrane. The interaction of calcium and cholesterol sulphate, which causes membrane destabilization and fusion in phosphatidylethanolamine containing model systems, may play a role in the acrosome reaction in human sperm.

References (28)

P.R. Cullis et al.
Biochim. Biophys. Acta
(1979)
P.C. Noordam et al.
Chem. Phys. Lipids
(1980)
K. Lohner et al.
Chem. Phys. Lipids
(1984)
P.R. Cullis et al.
Biochim. Biophys. Acta
(1978)
D.P. Siegel
Chem. Phys. Lipids
(1986)
R.M. Epand et al.
Biochim. Biophys. Acta
(1988)
H.W. Moser et al.
Biochim. Biophys. Acta
(1966)
G. Bleau et al.
Biochim. Biophys. Acta
(1975)
A.M. Jetten et al.
J. Invest. Dermatol.
(1989)
G. Bleau et al.
Biochim. Biophys. Acta
(1974)

G. Lalumiere et al.

Steroids

(1976)

S.J. Rehfeld et al.

J. Invest. Dermatol.

(1988)

D.P. Siegel et al.

Biophys. J.

(1989)

A.J. Verkleij et al.

Cell Fusion

Cited by (31)

The scientific adventures of Richard Epand
2023, Biophysical Chemistry
Citation Excerpt :
Lipophosphoglycan of Leishmania donovani is a very potent inhibitor of the formation of inverted phases and it is also an inhibitor of viral fusion [62–66]. An interesting small molecule that can inhibit membrane fusion is the inhibitor of negative curvature and membrane fusion, cholesterol sulphate [67,68]. Hyrolysis of this lipid to remove the sulfate group may play a role in the capacitation reaction to allow sperm to fuse with an egg.
This essay summarizes the many areas of science that my career has contributed to. It attempts to highlight some of the innovative concepts that developed from this work. The discussion encompasses studies I undertook from graduate school to the present but it will not attempt to be comprehensive. I apologize to individuals whose work I omitted. Because of space I cannot acknowledge all the contributions from other individuals that made these achievements possible.
Anionic lipids in Ca<sup>2+</sup>-triggered fusion
2012, Cell Calcium
Citation Excerpt :
We have previously established the critical role of CHOL in the fusion reaction, in part by removing it from the CV membrane using mβcd and quantitatively confirming the full recovery of all fusion parameters after delivering exogenous CHOL using hpβcd [3–5,7,52]. Here we used the same approach, but tested for recovery using cholesterol sulfate which is known to have a bilayer stabilizing effect similar to that of CHOL (likely due to the sterol backbone) but that also binds Ca2+ resulting in effects comparable to PS in model membranes [53]. Simply adding exogenous cholesterol sulfate to intact CV resulted in an inhibition of the fusion extent to 51.7 ± 5.9%, and a 22.4%/s depression of the initial fusion rate; in contrast to exogenous PI and PS, there was no effect on the Ca2+-sensitivity of fusion (Fig. 4).
Anionic lipids are native membrane components that have a profound impact on many cellular processes, including regulated exocytosis. Nonetheless, the full nature of their contribution to the fast, Ca²⁺-triggered fusion pathway remains poorly defined. Here we utilize the tightly coupled quantitative molecular and functional analyses enabled by the cortical vesicle model system to elucidate the roles of specific anionic lipids in the docking, priming and fusion steps of regulated release. Studies with cholesterol sulfate established that effectively localized anionic lipids could contribute to Ca²⁺-sensing and even bind Ca²⁺ directly as effectors of necessary membrane rearrangements. The data thus support a role for phosphatidylserine in Ca²⁺ sensing. In contrast, phosphatidylinositol would appear to serve regulatory functions in the physiological fusion machine, contributing to priming and thus the modulation and tuning of the fusion process. We note the complexities associated with establishing the specific roles of (anionic) lipids in the native fusion mechanism, including their localization and interactions with other critical components that also remain to be more clearly and quantitatively defined.
Structure of the skin barrier and its modulation by vesicular formulations
2003, Progress in Lipid Research
The natural function of the skin is to protect the body from unwanted influences from the environment. The main barrier of the skin is located in the outermost layer of the skin, the stratum corneum. Since the lipids regions in the stratum corneum form the only continuous structure, substances applied onto the skin always have to pass these regions. For this reason the organization in the lipid domains is considered to be very important for the skin barrier function. Due to the exceptional stratum corneum lipid composition, with long chain ceramides, free fatty acids and cholesterol as main lipid classes, the lipid phase behavior is different from that of other biological membranes. In stratum corneum crystalline phases are predominantly present, but most probably a subpopulation of lipids forms a liquid phase. Both the crystalline nature and the presence of a 13 nm lamellar phase are considered to be crucial for the skin barrier function. Since it is impossible to selectively extract individual lipid classes from the stratum corneum, the lipid organization has been studied in vitro using isolated lipid mixtures. These studies revealed that mixtures prepared with isolated stratum corneum lipids mimic to a high extent stratum corneum lipid phase behavior. This indicates that proteins do not play an important role in the stratum corneum lipid phase behavior. Furthermore, it was noticed that mixtures prepared only with ceramides and cholesterol already form the 13 nm lamellar phase. In the presence of free fatty acids the lattice density of the structure increases. In stratum corneum the ceramide fraction consists of various ceramide subclasses and the formation of the 13 nm lamellar phase is also affected by the ceramide composition. Particularly the presence of ceramide 1 is crucial. Based on these findings a molecular model has recently been proposed for the organization of the 13 nm lamellar phase, referred to as “the sandwich model”, in which crystalline and liquid domains coexist. The major problem for topical drug delivery is the low diffusion rate of drugs across the stratum corneum. Therefore, several methods have been assessed to increase the permeation rate of drugs temporarily and locally. One of the approaches is the application of drugs in formulations containing vesicles. In order to unravel the mechanisms involved in increasing the drug transport across the skin, information on the effect of vesicles on drug permeation rate, the permeation pathway and perturbations of the skin ultrastructure is of importance. In the second part of this paper the possible interactions between vesicles and skin are described, focusing on differences between the effects of gel-state vesicles, liquid-state vesicles and elastic vesicles.
Effect of incubating human sperm at room temperature on capacitation-related events
2002, Fertility and Sterility
Objective: To determine the effect of human sperm incubation at room temperature (20°C) upon capacitation-related events.
Design: Prospective study.
Setting: Basic research laboratory.
Patient(s): Semen samples were obtained from normozoospermic volunteers. Human follicular fluid (hFF) was collected from women undergoing assisted reproductive treatment.
Intervention(s): Spermatozoa were incubated for up to 18 hours at 20°C and/or 37°C.
Main Outcome Measure(s): Protein tyrosine phosphorylation patterns, development of hyperactivated motility, and induction of acrosome reaction (AR) in response to hFF.
Result(s): Spermatozoa incubated for 18 hours at 20°C showed an array of tyrosine phosphorylated proteins similar to noncapacitated cells. After incubation at 20°C, the percentage of spermatozoa displaying hyperactivated motility and undergoing acrosomal loss in response to hFF was significantly lower when compared with cells kept the same time at 37°C. Conversely, spermatozoa incubated overnight at 37°C could respond to hFF, either at 37°C or 20°C. When preincubation at 20°C was followed by sperm exposure to 37°C, capacitation-related events could be activated. In capacitated cells (16 hours at 37°C), 2-hour incubation at 20°C led to a significant decrease in acrosome reaction inducibility, suggesting sperm decapacitation.
Conclusion(s): Human sperm incubation at room temperature does not allow capacitation, although it does not affect hFF-induced acrosome reaction in capacitated cells. The blocking effect is overcome when spermatozoa are exposed to 37°C.
The aminosterol antibiotic squalamine permeabilizes large unilamerllar phospholipid vesicles
1998, Biochimica et Biophysica Acta - Biomembranes
The ability of the shark antimicrobial aminosterol squalamine to induce the leakage of polar fluorescent dyes from large unilamellar phospholipid vesicles (LUVs) has been measured. Micromolar squalamine causes leakage of carboxyfluorescein (CF) from vesicles prepared from the anionic phospholipids phosphatidylglycerol (PG), phosphatidylserine (PS), and cardiolipin. Binding analyses based on the leakage data show that squalamine has its highest affinity to phosphatidylglycerol membranes, followed by phosphatidylserine and cardiolipin membranes. Squalamine will also induce the leakage of CF from phosphatidylcholine (PC) LUVs at low phospholipid concentrations. At high phospholipid concentrations, the leakage of CF from PC LUVs deviates from a simple dose–response relationship, and it appears that some of the squalamine can no longer cause leakage. Fluorescent dye leakage generated by squalamine is graded, suggesting the formation of a discrete membrane pore rather than a generalized disruption of vesicular membranes. By using fluorescently labeled dextrans of different molecular weight, material with molecular weight ≤4000 g/mol is released from vesicles by squalamine, but material with molecular weight ≥10,000 is retained. Negative stain electron microscopy of squalamine-treated LUVs shows that squalamine decreases the average vesicular size in a concentration-dependent manner. Squalamine decreases the size of vesicles containing anionic phospholipid at a lower squalamine/lipid molar ratio than pure PC LUVs. In a centrifugation assay, squalamine solubilizes phospholipid, but only at significantly higher squalamine/phospholipid ratios than required for either dye leakage or vesicle size reduction. Squalamine solubilizes PC at lower squalamine/phospholipid ratios than PG. We suggest that squalamine complexes with phospholipid to form a discrete structure within the bilayers of LUVs, resulting in the transient leakage of small encapsulated molecules. At higher squalamine/phospholipid ratios, these structures release from the bilayers and aggregate to form either new vesicles or squalamine/phospholipid mixed micelles.
Morphological changes of human erythrocytes induced by cholesterol sulphate
1998, Clinical Biochemistry
Objectives: Morphological alterations of human erythrocytes induced by cholesterol sulphate (5-cholesten-3β-ol sulphate, CS) were studied.
Design and Methods: Influence of CS on red blood cell stability (in isotonic conditions) by simultaneous application of flow cytometry and scanning electron microscopy was studied.
Results: In isotonic medium CS induces erythrocyte size and shape changes in dose- and time-dependent manner. Incubation (in vitro) of erythrocytes with CS concentrations from 4 × 10⁻⁵ mol/dm³ to 8 × 10⁻⁵ mol/dm³ led to a progressive sphero-echinocitic shape transformation accompanied by a cell size decrease. In contrast to this, for CS content equal to 1 × 10⁻⁵ mol/dm³ the maintenance of the normal biconcave shape of red blood cells was observed.
Conclusions: The results suggest that CS, similarly to numerous evaginating amphiphilic agents, induces a transformation of the erythrocyte normal discoid shape to echinocytic form. This effect may be caused, at least partly, by an asymmetric expansion of the membrane lipid bilayer due to asymmetric distribution of CS incorporated into the membrane. The echinocytic shape transformation of erythrocytes indicated that CS intercalates in the outer hemileaflet of the lipid bilayer leading to membrane externalization.

View all citing articles on Scopus

View full text

Regular paperInteraction of calcium and cholesterol sulphate induces membrane destabilization and fusion: implications for the acrosome reaction

Abstract

Biochim. Biophys. Acta

Chem. Phys. Lipids

Chem. Phys. Lipids

Biochim. Biophys. Acta

Chem. Phys. Lipids

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

J. Invest. Dermatol.

Biochim. Biophys. Acta

Steroids

J. Invest. Dermatol.

Biophys. J.

Cell Fusion

Regular paper
Interaction of calcium and cholesterol sulphate induces membrane destabilization and fusion: implications for the acrosome reaction