Do hydrophobic sequences cleaved from cellular polypeptides induce membrane fusion reactions in vivo?

Lucy, J. A.

doi:10.1016/0014-5793(84)80085-x

Cited by 59 publications

(22 citation statements)

References 84 publications

(53 reference statements)

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“…The polymorphism accessible to PtdEtn-containing membranes can be a powerful agent for inducing the initial destabilization of the apposed bilayers, but for fusion additional factors (25) are required.…”

Section: Methodsmentioning

confidence: 99%

On the correlation between HII phase and the contact-induced destabilization of phosphatidylethanolamine-containing membranes.

Bentz¹,

Ellens²,

Lai³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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The abundance of phosphatidylethanolamine (PtdEtn) in biological membranes and the capacity of this lipid to sustain nonbilayer structures have been promoted as evidence for a role ofPtdEtn in biological fusion processes. To date there has been no direct evidence of a connection between the kinetics of bilayer destabilization and the polymorphism accessible to PtdEtn. We have developed a model system to examine this point directly using the proton-induced destabilization of PtdEtn/choleste~rylhemisuccinate unilamellar liposomes. We rind that the initial rate of bilayer mixing rapidly increases with temperature and reaches a maximal level just below the HI-phase transition temperature. The leakage from these liposomes rapidly increases, both in rate and extent, within the HI,-phase transition temperature range. Of an even greater significance is that at no temperature is there any mixing of aqueous contents within the liposomes. Thus, these lipids can begin to undergo the lamellar-to HeI-phase transition at the stage of two apposed liposomes. However, the nonbilayer structures formed do not cause fusion-i.e., the concomitant mixing of aqueous contents.Although the amphipathic lipids found in biological membranes are normally considered to be in a bilayer structure, it is well known that when dispersed in pure form there is a group of these lipids that present nonbilayer structures. The most well-examined class of this group is phosphatidylethanolamine (PtdEtn) (1). Depending upon the acyl chain composition of the PtdEtn, there is a specific temperature range below which an aqueous dispersion of the lipid exists in the bilayer or lamellar phase and above which it exists in the hexagonal HI, phase. This temperature range is denoted TH.Intermediate between these two thermodynamic phases are the lipidic pai-ticles (1). Though the molecular architecture underlying the electron microscopically observed lipidic particles is debatable-i.e., whether they are inverted micelles (1-4) or other nonbilayer configurations (5-7) there is a general agreement that the ability of PtdEtn to form these nonbilayer structures is relevant to the fusion event between two apposed membranes (1-9). As yet, there has never been any direct evidence to support this claim. With this in mind, we can ask the most basic question: Is there a correlation between the TH of a PtdEtn-containing lipid dispersion and the initial kinetics of bilayer destabilization between liposomes with this composition? This is the crux of the issue as to whether the TH has a role in fusion occurring in biological systems and it has never been addressed experimentally.The evidence to date is that PtdEtn's polymorphism is not required for the initial destabilization and fusion of membranes. It is well known that liposomes composed of lipids that do not show this polymorphism will fuse, most notable being the Ca2+-induced fusion of phosphatidylserine (PtdSer)-containing liposomes (10, 11). Likewise, the Ca2+-induced fusion of PtdSer/PtdEtn liposomes will occur we...

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Section: Methodsmentioning

confidence: 99%

On the correlation between HII phase and the contact-induced destabilization of phosphatidylethanolamine-containing membranes.

Bentz¹,

Ellens²,

Lai³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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“…A role for soluble proteolytic enzymes in fusion processes is suggested by recent observations that limited proteolysis can initiate erythrocyte fusion (Lucy, 1984a). Lucy (1984b) has also proposed that hydrophobic polypeptides produced by proteolysis may induce membrane fusion. Couch & Strittmatter (1984) have now shown that the specific blockers of myoblast fusion that inhibit proteinases act on a cytosolic protein with an apparent Mr of 80000.…”

Section: Surface Biochemistry Of Myoblasts During Fusionmentioning

confidence: 99%

The fusion of myoblasts

Wakelam¹

1985

Biochemical Journal

304

197

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“…Serum albumin might also exert its effect on the AR by perturbing lipid bilayers of the cell membrane through its hydrophobic nature, as suggested by Lucy (1984) to explain how hydrophobic sequences cleaved from cellular polypeptides may induce membrane fusion. In view of Lucy's idea, it is of interest that Garcia et al (1984) have shown that the fusion of small unilamellar vesicles can be induced by a 9,000-molecular -weight fragment of serum albumin.…”

Section: Serum Albuminmentioning

confidence: 99%

“…Lucy (1984) reviewed evidence showing associations between membrane fusion and the action of proteases on membrane proteins and proposed that hydrophobic polypeptides (which he compared to fusogenic proteins of some viruses) produced by cellular proteases induce membrane fusion. Lucy also suggested that these hydrophobic polypeptides "perturb" the lipid bilayers of the cells resulting in fusion of membranes.…”

Section: Hydrolytic Enzymesmentioning

confidence: 99%

Molecules that initiate or help stimulate the acrosome reaction by their interaction with the mammalian sperm surface

Meizel¹

1985

Am. J. Anat.

204

113

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This review deals with exogenous molecules that stimulate the acrosome reaction (AR) of mammalian sperm in vitro, presumably by acting at the sperm surface. Such molecules may exert their effect(s) by stimulating capacitation and/or by stimulation or initiation of the AR, and they are probably present at one of three putative in vivo sites (also discussed here) for the AR of a fertilizing sperm: the oviductal fluid, the cumulus oophorus matrix, and the zona pellucida. The molecules discussed include serum albumin, hydrolytic enzymes (particularly proteases); hormones including biogenic amines, estradiol, and arachidonic acid metabolites; sulfur-containing beta-amino acids; glycosaminoglycans such as hyaluronic acid; and a zona pellucida glycoprotein. Possible mechanisms to explain the effects of these molecules are also discussed. Several conclusions and suggestions are offered in this review: There is more than one site for the AR of a fertilizing sperm in vitro, depending on experimental conditions and species, but the site(s) at which the AR of a fertilizing sperm occur(s) in vivo is/are still a matter of disagreement; there are a number of molecules that can stimulate or initiate the AR in vitro, and such molecular duplication may also exist in vivo to ensure fertility; and synergistic interaction between some of those exogenous molecules may occur in the stimulation of capacitation and the stimulation or initiation of the AR.

show abstract

Do hydrophobic sequences cleaved from cellular polypeptides induce membrane fusion reactions in vivo?

Cited by 59 publications

References 84 publications

On the correlation between HII phase and the contact-induced destabilization of phosphatidylethanolamine-containing membranes.

On the correlation between HII phase and the contact-induced destabilization of phosphatidylethanolamine-containing membranes.

The fusion of myoblasts

Molecules that initiate or help stimulate the acrosome reaction by their interaction with the mammalian sperm surface

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